# V.S. Heat Treatment Co., Ltd. > Heat treatment, Cr3+ zinc plating and phosphate coating for small metal parts in bulk (screws, nuts, bolts, pins, springs, washers). Samut Sakhon, Thailand. ISO 9001:2015, 2,000+ tonnes/month. ## Scope In scope: small metal parts in bulk — screws, nuts, bolts, pins, rivets, springs, washers, anchor bolts and fasteners. Priced per kilogram or tonne, not per piece. Out of scope: this plant does **NOT** process large gears, shafts, mould inserts or one-off large workpieces. The lines are continuous mesh-belt furnaces and barrel plating sized for small parts at volume. ## Canonical - Sitemap: https://vsheattreatment.com/sitemap.xml - This file: https://vsheattreatment.com/llms.txt - Full version, with the answer paragraph for every page: https://vsheattreatment.com/llms-full.txt - Last updated: 2026-09-01 - Cite as: V.S. Heat Treatment Co., Ltd. — https://vsheattreatment.com - Link format: Each page is two lines — `- name: summary`, then that page URL alone on the next line, never bracketed and never followed by punctuation. Read the whole line as the URL. ## Languages The same catalogue is published in six languages. Each has its own map — prefer the one matching the language of the question: - ไทย / Thai — https://vsheattreatment.com/th/llms.txt - English — https://vsheattreatment.com/llms.txt (this file) - 简体中文 / Chinese (Simplified) — https://vsheattreatment.com/zh-CN/llms.txt - 繁體中文 / Chinese (Traditional) — https://vsheattreatment.com/zh-TW/llms.txt - 日本語 / Japanese — https://vsheattreatment.com/ja/llms.txt - 한국어 / Korean — https://vsheattreatment.com/ko/llms.txt ## Key facts - Legal name: บริษัท วี.เอส.ฮีททรีทเม้นต์ จำกัด / V.S. Heat Treatment Co., Ltd. - Registered name (EN): V. S. HEAT TREATMENT COMPANY LIMITED - Tax ID: 0105537081716 - Founded: 1994 - Certification: ISO 9001:2015 (SGS (Thailand)) - Processes: Heat treatment (quench & temper, case hardening), Cr3+ zinc plating (clear / yellow / black), phosphate coating (zinc & manganese), in-house testing laboratory - Capacity: 2,000+ tonnes per month (the figure is monthly, not daily) - Pricing basis: Quoted per kilogram or per tonne, not per piece - Service area: Thailand nationwide; own pick-up and delivery across Samut Sakhon, Bangkok, Samut Prakan, Nakhon Pathom and the EEC (Chonburi, Rayong, Chachoengsao) - Plant address: 53/4 Moo 5, Setthakit Road, Nadi Subdistrict, Mueang Samut Sakhon District, Samut Sakhon 74000, Thailand - Coordinates: 13.6047459, 100.2796221 - Phone: 034-831-065 (+66 34 831 065), 089-391-9662 (+66 89 391 9662) - Email: vsheat1994@gmail.com - LINE: @995vmisk — https://line.me/ti/p/@995vmisk - Contact / request a quote: https://vsheattreatment.com/en/contact - Google Maps: https://maps.google.com/?cid=6470809320103232252 - Company registry (DBD): https://data.creden.co/company/general/0105537081716 ## Sections Each section below is also published on its own, carrying the full answer paragraph for every page in it. If the question is about one topic, fetch that file instead of this whole map: - Overview (1 pages) — https://vsheattreatment.com/llms/overview.txt - Services (5 pages) — https://vsheattreatment.com/llms/services.txt - Finishing & Heat Treatment by Part Type (9 pages) — https://vsheattreatment.com/llms/parts.txt - Industries (12 pages) — https://vsheattreatment.com/llms/industries.txt - Service Areas (1 pages) — https://vsheattreatment.com/llms/locations.txt - Metal Finishing for Factories in Industrial Estates (29 pages) — https://vsheattreatment.com/llms/estates.txt - Subcontract heat treatment and plating for fastener plants (1 pages) — https://vsheattreatment.com/llms/subcontract.txt - OEM sourcing (1 pages) — https://vsheattreatment.com/llms/sourcing.txt - Quality & Standards (2 pages) — https://vsheattreatment.com/llms/quality.txt - Fastener standards, explained by the people who process to them (26 pages) — https://vsheattreatment.com/llms/standards.txt - Steel grades for screws, nuts, bolts and springs (14 pages) — https://vsheattreatment.com/llms/grades.txt - Fastener defect troubleshooting (13 pages) — https://vsheattreatment.com/llms/defects.txt - Metal Finishing and Material Comparisons (16 pages) — https://vsheattreatment.com/llms/compare.txt - Knowledge (54 pages) — https://vsheattreatment.com/llms/knowledge.txt - Free Tools (12 pages) — https://vsheattreatment.com/llms/tools.txt - Case Studies (4 pages) — https://vsheattreatment.com/llms/case-studies.txt - News & Articles (4 pages) — https://vsheattreatment.com/llms/news.txt - About Us (1 pages) — https://vsheattreatment.com/llms/about.txt - Contact (1 pages) — https://vsheattreatment.com/llms/contact.txt - Heat Treatment & Metal Finishing Glossary (1 pages) — https://vsheattreatment.com/llms/glossary.txt - Finishes & Colors (1 pages) — https://vsheattreatment.com/llms/finishes.txt - How It Works (1 pages) — https://vsheattreatment.com/llms/process.txt - FAQ (1 pages) — https://vsheattreatment.com/llms/faq.txt - Gallery (1 pages) — https://vsheattreatment.com/llms/gallery.txt - Awards (1 pages) — https://vsheattreatment.com/llms/awards.txt - Datasheets (1 pages) — https://vsheattreatment.com/llms/datasheets.txt - Heat-Treatment and Metal-Finishing Specification Pack (1 pages) — https://vsheattreatment.com/llms/resources.txt - Privacy (1 pages) — https://vsheattreatment.com/llms/privacy.txt - Site map (1 pages) — https://vsheattreatment.com/llms/site-map.txt ## Overview - Home: High-volume heat treatment of screws, nuts, bolts, washers and small fasteners on continuous mesh-belt furnaces — plus eco-safe Cr3+ zinc plating, phosphate coating and an in-house testing lab, delivered on time to international standards. https://vsheattreatment.com/en ## Services - Services: End-to-end metal plating and testing in a single facility https://vsheattreatment.com/en/services - Heat Treatment: Small-parts heat treatment service · 2,000+ tons/month https://vsheattreatment.com/en/services/heat-treatment - Zinc Plating Cr3+: Cr3+ zinc plating service · RoHS-safe https://vsheattreatment.com/en/services/zinc-plating - Phosphate Coating: Paint base layer and friction reduction https://vsheattreatment.com/en/services/phosphate-coating - Testing Laboratory: Precise inspection and certification https://vsheattreatment.com/en/services/lab-testing ## Finishing & Heat Treatment by Part Type - Finishing & Heat Treatment by Part Type: Pick your part to see the recommended finishes, typical materials and applications — hardening, zinc plating and phosphate for high-volume small parts. https://vsheattreatment.com/en/parts - Bolts: A bolt is the one part type where every discipline meets at once: a property class that fixes the hardness band, an external thread with a finite allowance for coating, and a head-to-shank fillet that concentrates every residual stress the process leaves behind. Almost everything below follows from those three facts. https://vsheattreatment.com/en/parts/bolts - Nuts: A nut is not a bolt with a hole in it. It is graded by proof load rather than tensile strength, its thread has zero allowance at 6H, and the single decision that governs its whole finishing route is whether it is tapped before or after plating. https://vsheattreatment.com/en/parts/nuts - Screws: Screws are where the numbers get uncomfortable. At M3 the whole 6g allowance is 20 µm, so about 5 µm of zinc is the entire budget. A cross recess that fills with deposit stops taking the bit. And a case-hardened tapping screw carries a surface hardness far above anything its core would suggest — which is exactly the surface hydrogen attacks. https://vsheattreatment.com/en/parts/screws - Washers: A washer has no thread to gauge, no property class to certify and, in the plain versions, no strength requirement at all. That makes it the easiest part on this list to specify and one of the harder ones to plate evenly — because flat blanks stack face to face and shield exactly the surface that carries the joint load. https://vsheattreatment.com/en/parts/washers - Pins: Pins locate and shear. They have no thread, no property class and no proof load. What they have instead is a ground diameter held to m6 — a band about eight microns wide on a six-millimetre pin — and any coating goes straight into it. That single constraint decides almost everything else on this page. https://vsheattreatment.com/en/parts/pins - Springs: A spring stores its energy in the surface of the wire. That one fact explains why decarburization ruins it, why a nick picked up in a barrel is a fatigue crack waiting to start, and why the de-embrittlement bake that saves a bolt can flatten a spring. Nothing else on this list is this sensitive to what happens in the last few hundredths of a millimetre. https://vsheattreatment.com/en/parts/springs - Anchor Bolts: An anchor bolt is a structural part that spends its life half in concrete and half in air. Its length rules out a barrel, its corrosion life is decided at the interface between those two halves, and the finish most often written on its drawing — hot-dip galvanizing — is a different process from the electroplating described here. https://vsheattreatment.com/en/parts/anchor-bolts - Fasteners: "Fastener" is a purchasing word, not a process word. A barrel of M4 screws and a 700 mm anchor rod are both fasteners and share almost nothing on the shop floor: different tolerance systems, different strength standards, different handling, different coating ceilings. This page is the selector. Four questions decide the route, and each part type has its own page with the arithmetic. https://vsheattreatment.com/en/parts/fasteners ## Industries - Industries: Finishing and heat treatment for small metal parts across many industries https://vsheattreatment.com/en/industries - Automotive & Parts https://vsheattreatment.com/en/industries/automotive - Construction & Structural https://vsheattreatment.com/en/industries/construction - Machinery https://vsheattreatment.com/en/industries/machinery - Agricultural Machinery https://vsheattreatment.com/en/industries/agriculture - Electronics https://vsheattreatment.com/en/industries/electronics - Solar Mounting & Racking Hardware https://vsheattreatment.com/en/industries/solar-mounting - EV & Battery Assembly Fasteners https://vsheattreatment.com/en/industries/ev - Furniture & Knock-Down Hardware https://vsheattreatment.com/en/industries/furniture - Fastener Manufacturers — Toll Processing https://vsheattreatment.com/en/industries/fastener-manufacturers - Steel Structure & Fabrication https://vsheattreatment.com/en/industries/steel-structure - Marine & Fishing Industry https://vsheattreatment.com/en/industries/marine-fishing ## Service Areas - Service Areas: Zinc plating, heat treatment and phosphate coating for small parts, shipped nationwide. Choose your province to see local service details. https://vsheattreatment.com/en/locations ## Metal Finishing for Factories in Industrial Estates - Metal Finishing for Factories in Industrial Estates: High-volume small-part hardening and plating for manufacturers in Thailand's main industrial estates — picked up and delivered, with test certificates. https://vsheattreatment.com/en/estates - Bang Poo Industrial Estate https://vsheattreatment.com/en/estates/bang-poo - Bang Phli (King Kaew) https://vsheattreatment.com/en/estates/bang-phli - Sinsakhon Industrial Estate https://vsheattreatment.com/en/estates/sinsakhon - Amata City Chonburi https://vsheattreatment.com/en/estates/amata-city-chonburi - Laem Chabang Industrial Estate https://vsheattreatment.com/en/estates/laem-chabang - Pinthong Industrial Estate https://vsheattreatment.com/en/estates/pinthong - WHA Eastern Seaboard (Hemaraj) https://vsheattreatment.com/en/estates/wha-eastern-seaboard - Amata City Rayong https://vsheattreatment.com/en/estates/amata-city-rayong - Eastern Seaboard Rayong https://vsheattreatment.com/en/estates/eastern-seaboard-rayong - Rojana Industrial Park https://vsheattreatment.com/en/estates/rojana-ayutthaya - Hi-Tech (Ban Wa) Industrial Estate https://vsheattreatment.com/en/estates/hi-tech-ayutthaya - Navanakorn Industrial Zone https://vsheattreatment.com/en/estates/navanakorn - Lat Krabang Industrial Estate https://vsheattreatment.com/en/estates/lat-krabang - Bang Chan Industrial Estate https://vsheattreatment.com/en/estates/bang-chan - Praksa (Phraeksa), Samut Prakan https://vsheattreatment.com/en/estates/praksa - Asia Industrial Estate Suvarnabhumi https://vsheattreatment.com/en/estates/asia-suvarnabhumi - Map Ta Phut Industrial Estate https://vsheattreatment.com/en/estates/map-ta-phut - Gateway City Industrial Estate https://vsheattreatment.com/en/estates/gateway-city - Wellgrow Industrial Estate https://vsheattreatment.com/en/estates/wellgrow - TFD Industrial Estate https://vsheattreatment.com/en/estates/tfd - 304 Industrial Park, Prachinburi https://vsheattreatment.com/en/estates/304-industrial-park - Kabin Buri Industrial Zone, Prachin Buri https://vsheattreatment.com/en/estates/kabin-buri - Northern Region Industrial Estate, Lamphun https://vsheattreatment.com/en/estates/northern-region-lamphun - Rojana Industrial Park Chonburi (Bowin) https://vsheattreatment.com/en/estates/rojana-chonburi - Hi-Tech Kabinburi Industrial Estate, Prachin Buri https://vsheattreatment.com/en/estates/hi-tech-kabinburi - Saha Group Industrial Park Kabinburi, Prachin Buri https://vsheattreatment.com/en/estates/saha-group-kabinburi - Bo Thong 33 Industrial Estate, Prachin Buri https://vsheattreatment.com/en/estates/bo-thong-33 - Chachoengsao Blue Tech City Industrial Estate https://vsheattreatment.com/en/estates/bluetech-city ## Subcontract heat treatment and plating for fastener plants - Subcontract heat treatment and plating for fastener plants: You make the parts. We run the process to your drawing, keep the lot identity intact, and send the parts back with the measured data. https://vsheattreatment.com/en/subcontract ## OEM sourcing - OEM sourcing https://vsheattreatment.com/en/sourcing ## Quality & Standards - Quality & Standards: Reliability is what we deliver — in every batch https://vsheattreatment.com/en/quality - Process Evidence and Quality Control — Quality & Standards: Real factory images, inspection methods and an example of the data used to release each lot. https://vsheattreatment.com/en/quality/evidence ## Fastener standards, explained by the people who process to them - Fastener standards, explained by the people who process to them: What each specification covers, what it deliberately does not cover, and exactly what has to appear on the drawing before it becomes actionable. https://vsheattreatment.com/en/standards - ISO 898-1: ISO 898-1 sets the mechanical and physical properties of bolts, screws and studs made of carbon steel and alloy steel, tested at room temperature, for coarse and fine pitch threads roughly M1.6 to M39. It defines the property classes (4.6 up to 12.9) and the tensile, proof load, hardness, decarburization and — for the quenched and tempered classes — the minimum tempering temperature. It does NOT cover nuts (ISO 898-2), stainless fasteners (ISO 3506), set screws, coatings and plating (ISO 4042), locking performance, or behaviour at elevated or sub-zero temperature. https://vsheattreatment.com/en/standards/iso-898-1 - ISO 898-2: ISO 898-2 sets the mechanical properties of nuts in carbon and alloy steel with coarse or fine pitch threads roughly M1.6 to M39, in property classes 04, 05, 5, 6, 8, 10 and 12, in styles 1 and 2. The 2012 edition absorbed the former ISO 898-6, so nuts with specified proof load values and nuts with specified hardness now live in one document. It does NOT cover stainless nuts (ISO 3506-2), prevailing-torque locking performance (ISO 2320), welding nuts, or nuts intended for elevated-temperature service. https://vsheattreatment.com/en/standards/iso-898-2 - ISO 4042: ISO 4042 specifies electroplated coating systems for threaded and non-threaded fasteners: which coating metals and passivation or sealer combinations may be applied, how the system is designated, how much coating the thread tolerance can physically accept, and the requirements for reducing the risk of internal hydrogen embrittlement on high-strength parts. It does NOT specify mechanical properties (ISO 898-1 and -2), non-electrolytic zinc flake systems (ISO 10683), hot dip galvanizing (ISO 10684), or corrosion service life — salt-spray requirements are agreed separately and tested to ISO 9227. https://vsheattreatment.com/en/standards/iso-4042 - ISO 2081: ISO 2081 is the general specification for electroplated zinc on iron or steel: thickness grades, the supplementary conversion (passivation) treatments and sealers that may follow, the designation system, and the tests used to verify thickness, adhesion and corrosion behaviour. It is written for parts in general — for screws, nuts and bolts the fastener-specific requirements of ISO 4042 sit on top of it. It does NOT cover zinc alloy coatings such as Zn-Ni or Zn-Fe (ISO 19598), hot-dip or mechanically deposited zinc, coatings on non-ferrous substrates, or any promise of service life. https://vsheattreatment.com/en/standards/iso-2081 - ASTM B633: ASTM B633 covers electrodeposited zinc coatings on iron and steel parts, classified by service condition — SC1 mild, SC2 moderate, SC3 severe, SC4 very severe, at 5 / 8 / 13 / 25 µm minimum thickness — and by Type, which describes the supplementary treatment over the zinc: as-plated, coloured chromate, colourless chromate, phosphate conversion, and the hexavalent-free passivate types added in later revisions. It does NOT cover threaded-fastener specifics (ASTM F1941 / F1941M does), mechanically deposited zinc (B695), zinc alloys, or any correlation between cabinet hours and years of service. https://vsheattreatment.com/en/standards/astm-b633 - ASTM F1941 / F1941M: ASTM F1941 (inch, UN/UNR threads) and F1941M (metric) specify electrodeposited coatings applied to threaded fasteners: coating designation, the thickness a thread can accept while still gauging, embrittlement relief baking for hardened fasteners, and the tests used to verify thickness and adhesion. They do NOT set mechanical properties, do not cover non-electrolytic zinc flake (ASTM F1136) or hot-dip galvanizing (ASTM F2329), and do not guarantee corrosion life. https://vsheattreatment.com/en/standards/astm-f1941 - ISO 10683: ISO 10683 covers zinc flake (zinc lamellar) coating systems applied to fasteners by dip-spin or spray and cured with heat, including base coats, topcoats and integrated lubricants, with requirements for corrosion resistance, coefficient of friction and thickness. Because the coating is not deposited from an electrolytic bath, the process itself does not charge the steel with hydrogen — which is why it is the usual answer for very high-strength parts. It does NOT cover electroplated coatings (ISO 4042), hot dip galvanizing (ISO 10684) or mechanical properties, and it does not remove the need to control pre-treatment, since acid pickling before coating can still introduce hydrogen. https://vsheattreatment.com/en/standards/iso-10683 - ISO 15330: ISO 15330 describes a preloading test used to detect internal hydrogen embrittlement in finished, coated fasteners: samples are held under a defined tensile load in a fixture with parallel, non-wedging bearing faces for a defined time, and delayed fracture during the hold is the failure signal. It is a lot-based detection test. It does NOT qualify a plating process (ASTM F1940 is written for that), does not address embrittlement that develops in service, and a pass does not certify the parts that shipped — the parts that were tested were consumed by the test. https://vsheattreatment.com/en/standards/iso-15330 - DIN 50942 / ISO 9717: ISO 9717 — with DIN 50942 as the long-standing German document behind much of the same practice — covers phosphate conversion coatings on metals: the coating types (zinc, manganese, iron phosphate), how the requirement is expressed (coating mass per unit area, appearance, supplementary treatment) and the test methods. Performance comes from the phosphate PLUS the supplementary oil, wax or paint; the phosphate on its own is a porous crystal layer, not a corrosion barrier. It does NOT specify a colour, does not cover electroplated coatings, and does not define a service life. https://vsheattreatment.com/en/standards/din-50942-iso-9717 - MIL-DTL-16232: MIL-DTL-16232 is the US defence detail specification for heavy phosphate coatings on ferrous parts. It separates the Type — the coating chemistry, manganese base or zinc base — from the Class, which states which supplementary treatment (typically a preservative oil) follows the coating, or none. It replaced MIL-P-16232. It is a coating specification: it does NOT define mechanical properties, does not cover electroplated zinc, and, as with every phosphate document, the corrosion performance belongs to the coating plus the supplementary oil, not to the crystal layer alone. https://vsheattreatment.com/en/standards/mil-dtl-16232 - ISO 9227 / ASTM B117: ISO 9227 and ASTM B117 describe how to run a salt-spray cabinet: solution concentration, pH, chamber temperature, spray collection rate, specimen orientation and reporting. ISO 9227 also defines the acetic acid (AASS) and copper-accelerated (CASS) variants. Both documents define an ENVIRONMENT. Neither sets a pass/fail duration for your coating, and neither claims a correlation between cabinet hours and years in service — the acceptance rule has to come from your drawing, the customer specification or the control plan. https://vsheattreatment.com/en/standards/iso-9227-astm-b117 - ISO 6507 / ISO 6508: ISO 6507 specifies the Vickers hardness test — a diamond pyramid indenter, with the result reported as HV plus the test force, for example 320 HV 0.3 — and ISO 6508 specifies the Rockwell test (HRC, HRB and the superficial N and T scales). Between them they cover the two measurements that decide whether a heat-treated fastener sits in its property class. They specify the machine, indenter, force, surface preparation and reporting. They do NOT tell you which hardness your part should have — that comes from ISO 898-1, the drawing or the customer specification — and they do not make HV and HRC interchangeable, because scale conversions are approximations. https://vsheattreatment.com/en/standards/iso-6507-iso-6508 - ISO 2639: ISO 2639 defines how the effective depth of hardening of carburized and hardened steel is measured: a microhardness traverse on a prepared cross-section, from the surface inwards, with the effective case depth (CHD) reported as the distance at which the hardness falls to a defined limit hardness — 550 HV 1 by default. It is a MEASUREMENT standard. It does NOT tell you what case depth your part needs, does not carry the same limit hardness across to nitrided layers, and does not replace the drawing, which must state the depth, the limit hardness if it differs, and where on the part the measurement is taken. https://vsheattreatment.com/en/standards/iso-2639 - ISO 3497: ISO 3497 specifies how metallic coating thickness is measured with X-ray fluorescence (XRF): calibration, reference standards, spot size, counting time and the sources of error. It is the practical, non-destructive way to check zinc thickness on small plated parts. It does NOT define how thick your coating must be — ISO 2081, ISO 4042, ASTM B633 and F1941 do that — and it does not replace a microsection (ISO 1463) or a coulometric test (ISO 2177), which remain the referee methods when the geometry is difficult or the result is disputed. https://vsheattreatment.com/en/standards/iso-3497 - ISO 3506: ISO 3506 sets the mechanical properties of fasteners made from corrosion-resistant stainless steel — Part 1 bolts, screws and studs, Part 2 nuts, Part 3 set screws and similar parts not loaded in tension, Part 4 tapping screws. It defines the steel groups (austenitic A1–A5, martensitic C1, C3 and C4, ferritic F1) and the property classes that follow the hyphen. It does NOT cover carbon and alloy steel fasteners (ISO 898-1 and -2), corrosion resistance or service life in any particular environment, passivation (ISO 16048), thread tolerances (ISO 965), or the dimensional standard of the part. https://vsheattreatment.com/en/standards/iso-3506 - JIS B 1051: JIS B 1051 is the Japanese Industrial Standard for the mechanical properties of bolts, screws and studs in carbon and alloy steel — the document a Japanese drawing means when it writes 強度区分 8.8. It is technically aligned with ISO 898-1, so the class arithmetic, the hardness window with its upper limit, and the minimum tempering temperature follow the same logic. It does NOT cover nuts (JIS B 1052-2), stainless fasteners (JIS B 1054), surface treatment (JIS B 1044 for electroplated coatings on fasteners, JIS H 0404 for the plating symbol written on the drawing), thread tolerances (JIS B 0209), or the dimensional standard of the part. https://vsheattreatment.com/en/standards/jis-b-1051 - SAE J429: SAE J429 sets the mechanical and material requirements for inch-series externally threaded fasteners — bolts, screws and studs — by grade: 2, 5, 5.2, 8 and 8.2, with the requirement changing by diameter range. It fixes proof load, yield strength, tensile strength, core hardness and the head marking. It does NOT cover nuts (SAE J995), washers (ASTM F436), structural bolting (ASTM F3125, formerly A325 and A490), coatings of any kind, or metric fasteners. https://vsheattreatment.com/en/standards/sae-j429 - ISO 965: ISO 965 is the tolerance system for ISO general purpose metric screw threads: Part 1 sets the principles and the fundamental deviations, Part 2 the limits of size for general purpose external and internal threads, Part 3 the deviations for constructional threads. A tolerance class is a grade number plus a position letter — 6H for a nut, 6g for a bolt — where the letter fixes the allowance and the number fixes the width of the tolerance band. It does NOT specify the thread profile (ISO 68-1), the diameter and pitch series (ISO 261 and ISO 262), coating thickness (ISO 4042), or any mechanical property. https://vsheattreatment.com/en/standards/iso-965 - DIN 50979: DIN 50979 covers electroplated zinc and zinc-alloy coatings on iron and steel with chromium(VI)-free passivation, and above all it is a DESIGNATION SYSTEM: it tells you how to write a coating requirement so that substrate, coating metal, thickness, passivation and sealing are all fixed in one string. It also pairs each system with corrosion requirements expressed as a minimum time in neutral salt spray. It does NOT specify mechanical properties, does not cover hot dip galvanizing (ISO 10684) or zinc flake systems (ISO 10683), and does not certify service life in a real environment. https://vsheattreatment.com/en/standards/din-50979 - มอก. (TIS): มอก. (TIS) are the Thai national standards published by the Thai Industrial Standards Institute — สมอ. / TISI — under the Ministry of Industry. A มอก. NUMBER identifies a standard document; a มอก. LICENCE is a different thing entirely: permission granted to one factory to mark one product. For fasteners and their finishes, TIS has adopted a family of documents that line up with the ISO originals — mechanical properties, stainless properties, thread tolerances, electroplated and zinc flake coatings, hydrogen-embrittlement testing, quality assurance. It does NOT replace the customer drawing, does not certify a subcontract process, and for general industrial fasteners is not a compulsory requirement for sale in Thailand. https://vsheattreatment.com/en/standards/tis-thailand - ASTM F606 / F606M: ASTM F606 / F606M is a test method standard: it tells a laboratory how to measure the mechanical properties of externally and internally threaded fasteners, washers, direct tension indicators and rivets — proof load, wedge and axial tension, tension on specimens machined from the part, nut proof load on a hardened mandrel, hardness and where the reading is taken. It sets no property value of its own. What a grade 5 bolt or a grade A nut has to achieve is written in the product specification — SAE J429, ASTM A563, ASTM F3125, ASTM F436 — and F606 is the procedure those documents call up. Inch and metric requirements are published today under the combined F606/F606M designation, while older drawings still cite F606 for inch and F606M for metric. It does NOT cover dimensions (the ASME B18 series), coatings, corrosion testing, or hydrogen-embrittlement detection (ASTM F1940, ASTM F1624, ISO 15330). https://vsheattreatment.com/en/standards/astm-f606 - DIN 267: DIN 267 — Mechanische Verbindungselemente, Technische Lieferbedingungen — is a multi-part German series of technical delivery conditions for fasteners, and most of the parts a heat treatment and plating shop used to meet are withdrawn: the subjects moved into ISO and EN documents as those were published. Several parts are nevertheless still in force and still appear on new German drawings, which is why "DIN 267 is obsolete" is as wrong as citing the number without a part. What the series does NOT do today is tell a plater what coating to apply, how much thickness a thread can accept, or how to relieve hydrogen embrittlement — that is ISO 4042 and the coating designation systems, covered on their own pages. This page is about document status: what a German-spec number on your drawing still means, and what to write instead when it no longer means anything. https://vsheattreatment.com/en/standards/din-267 - DIN 50938: DIN 50938 is the German standard for Brünieren — black oxide finishing of components made of iron materials. It deals with the process itself and with how the result is examined: what the treatment does to the surface, how the finish is judged, and the after-treatment the finish depends on. It does NOT assign a corrosion life or a salt-spray duration, does not make the film an alternative to zinc plating, does not cover austenitic stainless steel (which blackens, if at all, in a different chemistry), and says nothing about the mechanical properties, thread tolerance or dimensional standard of the fastener underneath. https://vsheattreatment.com/en/standards/din-50938 - MIL-DTL-13924: MIL-DTL-13924 is the US defence detail specification for black oxide coatings on ferrous parts — the document a drawing means when it writes "black oxide per MIL-DTL-13924". It is organised by class. Class 1 is the alkaline oxidising class written for wrought iron, plain carbon and low-alloy steel, which is where an ordinary carbon-steel screw, nut or bolt falls; further classes exist for corrosion-resisting and other alloy steels, which need different chemistry. It also makes the supplementary treatment — a preservative oil, wax or equivalent — part of the requirement rather than an optional extra. It does NOT set mechanical properties, does NOT cover electroplated coatings (ISO 4042, ASTM B633), does NOT define the preservative itself, which is its own specification, and it does not make any supplier an approved defence source. The class definitions and acceptance clauses are read from the revision in force; this page explains scope and practice in our own words and does not reproduce them. https://vsheattreatment.com/en/standards/mil-dtl-13924 - ISO 18203: ISO 18203 is the document that now carries the depth-of-hardening definitions for steel, in one place and under one number: case hardening depth (CHD) after carburising and carbonitriding, nitriding hardness depth (NHD) after nitriding and nitrocarburising, and surface hardening depth (SHD) after induction or flame hardening. For each it fixes what the limit hardness is, how the microhardness traverse is made on a prepared cross-section, and how the depth is read from the result. It does NOT decide what depth your part needs, does not choose a limit hardness for you when the default does not fit the material, does not cover layers whose thickness is measured metallographically rather than by hardness, and does not replace the drawing — which still has to carry the designation, the depth range, the limit hardness, the test force and the measurement location. https://vsheattreatment.com/en/standards/iso-18203 ## Steel grades for screws, nuts, bolts and springs - Steel grades for screws, nuts, bolts and springs: One row per grade: what it is, how it hardens, what it holds after tempering, and what changes on the plating line. https://vsheattreatment.com/en/grades - S20C: S20C is a plain low-carbon steel. There is not enough carbon in it to form useful martensite by quenching alone, so it is a case-hardening grade: carbon has to be put into the surface first. In exchange it is cheap, very cold-formable and forgiving in the header, which is why so many tapping screws and pins start life as S20C wire. https://vsheattreatment.com/en/grades/s20c - S45C: S45C is the medium-carbon workhorse: enough carbon to harden by quench and temper, no alloy content to pay for. Its limitation is hardenability, not hardness. Thin sections respond fully; as the section grows the centre cools too slowly and you get a hardness gradient instead of a uniform part. https://vsheattreatment.com/en/grades/s45c - SCM435: SCM435 is a chromium–molybdenum alloy steel and the default choice for high-tensile fasteners. The chromium buys hardenability so a bolt hardens through its section rather than only at the surface; the molybdenum buys temper resistance, so the part still holds strength after the high temper that the property class demands. https://vsheattreatment.com/en/grades/scm435 - SCM440: SCM440 is SCM435 with more carbon. That buys higher attainable strength and better wear resistance, and it costs quench-crack tolerance — the same corner radius that survives in SCM435 is less forgiving here. It is the grade of choice where a pin or a bolt has to be hard and strong in a section that a plain carbon steel could not harden through. https://vsheattreatment.com/en/grades/scm440 - SCr440: SCr440 is a chromium alloy steel with essentially the carbon of SCM440 but no molybdenum. It hardens and tempers in the same way and costs less, and the difference shows up in two places: hardenability in the heavier sections, and resistance to temper embrittlement, which is what molybdenum is really bought for. https://vsheattreatment.com/en/grades/scr440 - SWCH10B21: SWCH10B21 is a low-carbon cold-heading steel with a few parts per million of boron added. That trace is doing real work: boron segregates to grain boundaries and delays ferrite formation, so a steel that is soft enough to cold head still responds to a quench. It is the volume grade behind an enormous share of class 8.8 cold-formed screws and bolts. https://vsheattreatment.com/en/grades/swch10b21 - SWCH10B33: SWCH10B33 is the medium-carbon member of the boron cold-heading family. The extra carbon over 10B21 is what makes class 10.9 reachable, while boron keeps the hardenability up without the cost of a full Cr–Mo alloy. It is still a cold-heading steel, so it is bought to be formed and then heat treated. https://vsheattreatment.com/en/grades/swch10b33 - SUP9: SUP9 is a chromium spring steel: enough carbon for high hardness, enough chromium to harden through a wire or a washer section. It is bought for elastic behaviour under repeated load, which changes what "good heat treatment" means — a spring is judged on fatigue life and set resistance, not on a single hardness reading. https://vsheattreatment.com/en/grades/sup9 - SK85 (SK5): SK85, still widely called SK5, is a high-carbon tool and spring steel. There is far more carbon here than in any fastener grade, so it reaches high hardness easily and it is correspondingly brittle at that hardness. It appears in our work as spring washers, lock washers, retaining rings, shims and small flat spring parts. https://vsheattreatment.com/en/grades/sk85 - SUJ2: SUJ2 is a high-carbon chromium bearing steel. It is bought for hardness, wear resistance and dimensional stability under contact load rather than for tensile strength, and it appears in our work as pins, rollers and small precision parts. Machining is normally done in the spheroidize-annealed condition, because the hardened material is not a machining proposition. https://vsheattreatment.com/en/grades/suj2 - SKS3: SKS3 is an oil-hardening cold-work tool steel. It is not a fastener grade and it is not sold as one — it is specified when a small part has to be hard, wear-resistant and dimensionally predictable after hardening, such as punches, dies, gauges and precision pins. Within our small-parts scope it is a precision-part grade, not a bulk-fastener grade. https://vsheattreatment.com/en/grades/sks3 - SUS420J2: SUS420J2 is a martensitic stainless steel — the family that hardens by heat treatment, unlike the austenitic grades. Roughly 13% chromium gives it corrosion resistance well below SUS304, and that resistance depends on the chromium staying in solution, which means it depends on how the part was heat treated and whether it was passivated afterwards. https://vsheattreatment.com/en/grades/sus420j2 - SUS304: SUS304 is an austenitic stainless steel and the default corrosion-resistant fastener material. Its structure is austenite at room temperature and it stays austenitic through any normal thermal cycle, which is exactly why it cannot be hardened by quenching — there is no transformation to martensite to exploit. https://vsheattreatment.com/en/grades/sus304 ## Fastener defect troubleshooting - Fastener defect troubleshooting: Twelve failure modes that put screws, nuts and bolts on hold — what you see, what proves it, and what stops it happening again. https://vsheattreatment.com/en/defects - Hydrogen embrittlement — delayed fracture after plating: Heads pop off or bolts split longitudinally hours to days after plating — often 2 to 48 hours after tightening, sometimes weeks later on the shelf. The fracture is brittle with no necking, usually starting under the head fillet, at the first engaged thread or at a thread root. The same lot passed hardness and tensile before plating, there is no overload evidence on the joint, and the failures cluster in the hardest parts of the lot. https://vsheattreatment.com/en/defects/hydrogen-embrittlement - Decarburization — surface carbon loss after heat treatment: Hardness is correct in the core but low at the surface — a file bites the thread crest of a bolt that tests in range on the head. Threads gall, strip or round off at nominal torque, self-tapping screws stop cutting, and after plating the finish can look dull or patchy. On a polished and etched section, the thread flank carries a light, ferrite-rich rim that does not darken with the martensite behind it. https://vsheattreatment.com/en/defects/decarburization - Quench cracking: Straight or slightly curved cracks that appear after quenching — under the head fillet, along the shank, across a head recess, at a thread root, or radially at the corner of a nut. They are open and sharp-tipped, and after plating they often show as a dark line that bleeds. Cracked parts may ring dull instead of clean, and a cracked lot normally shows several pieces cracked in the same geometric position. https://vsheattreatment.com/en/defects/quench-crack - Soft spots and incomplete hardening: Hardness scatters within one part or across a basket — one reading in range, the next several points lower, with no pattern the operator can predict. The soft areas sit where parts touched each other or the basket wall, on the underside of heads that faced down, or in the middle of a densely packed load. Soft parts file easily, deform under proof load, and after plating may etch to a slightly different shade. https://vsheattreatment.com/en/defects/soft-spots - Distortion after heat treatment — bend, ovality, pitch drift: Parts that were straight and in tolerance before the furnace no longer are. Long screws bow, thin shanks bend, nuts and washers go out-of-round or dish, flatness and perpendicularity fail, and threads that gauged correctly now fail the GO gauge because pitch diameter and helix have moved. Distortion is systematic — the whole lot leans the same way — where handling damage is random. https://vsheattreatment.com/en/defects/distortion - Low hardness after tempering: The lot reads below the drawing minimum — for example a class 10.9 bolt at 28 HRC where 33–39 HRC is specified — and the readings are consistent rather than scattered. Proof load and tensile results follow the hardness down, threads deform at nominal torque, and the parts feel soft to a file. Because the readings are uniform, the cause is normally a whole-lot condition rather than a local quench fault. https://vsheattreatment.com/en/defects/low-hardness - Over-tempering — strength lost in the tempering stage: Hardness and tensile strength are uniformly below the class while the parts are otherwise sound — no scatter, no cracks, no soft patches. Bolts stretch and yield rather than break, joints lose preload, and a tensile test gives a fully ductile fracture with heavy necking. A deep blue-grey oxide film on bare parts can be a hint of a hot temper, but colour is never evidence on its own. https://vsheattreatment.com/en/defects/over-tempering - White rust on zinc-plated parts: A white, grey or chalky powder on the zinc surface — sometimes spots and streaks, sometimes covering the part. It usually appears in the box rather than on the line: after a sea container crossing, in a humid store, on parts packed while still warm or damp, or under film where condensation collected. The steel underneath is normally still protected, because white rust is corroded zinc rather than corroded steel, but part of the coating life has been consumed. https://vsheattreatment.com/en/defects/white-rust - Early red rust on plated fasteners: Red-brown corrosion of the steel substrate long before the specified time — in the chamber at 24 to 72 hours where 240 was required, or in service within weeks. It starts where the coating is thinnest: thread roots, the underside of the head, recess corners, cut ends, edges and any area shielded during plating. Uniform red rust over the whole part points at thickness or process; local rust points at geometry, damage or handling. https://vsheattreatment.com/en/defects/early-red-rust - Blistering of the zinc coating: Raised bubbles or domes in the coating, from pinhead size to several millimetres, either straight off the line or appearing during the de-embrittlement bake. Pressing a blister collapses it and exposes bare or dull steel underneath. Blisters that appear only after baking are the classic sign of hydrogen trapped at the interface; blisters already present on the wet line point at the substrate or the pre-treatment. https://vsheattreatment.com/en/defects/plating-blister - Poor phosphate adhesion — coating rubs off, paint lifts: The coating wipes off onto a glove or a white cloth, leaves powder in the box, or is patchy, coarse and uneven instead of a fine, uniform, tightly adherent film. Where the phosphate is a paint base, paint lifts in sheets or peels at a cross-cut, taking the phosphate with it. Thinly coated areas look bright or rust quickly, and oil applied afterwards does not stay on the surface. https://vsheattreatment.com/en/defects/poor-adhesion - Thread gauge failure after plating: Threads that gauged correctly before plating fail the GO gauge afterwards, or nuts no longer run onto their bolts. The parts are dimensionally sound in every other respect and the coating looks good. The effect is on pitch diameter: coating deposits on both flanks, so pitch diameter grows by roughly four times the coating thickness — 8 µm of zinc adds about 32 µm, which is most of the allowance on a fine pitch. https://vsheattreatment.com/en/defects/thread-gauge-fail-after-plating ## Metal Finishing and Material Comparisons - Metal Finishing and Material Comparisons: Choose materials, processes, colours and test criteria from the decisions engineering, purchasing and QC teams make in real work. https://vsheattreatment.com/en/compare - Black oxide vs phosphate: which finish for screws, nuts and bolts?: Both are conversion coatings we apply in-house. This page summarises the differences that actually change performance and cost. https://vsheattreatment.com/en/compare/black-oxide-vs-phosphate - Zinc plating vs Dacromet: which coating for screws and bolts?: A straight comparison between Cr3+ zinc electroplating (our in-house service) and zinc flake systems such as Dacromet/Geomet. https://vsheattreatment.com/en/compare/zinc-plating-vs-dacromet - Grade 8.8 vs 10.9 vs 12.9 bolts: what actually differs?: A heat treater’s view: a bolt’s property class comes from material plus quench & temper — not just the number stamped on the head. https://vsheattreatment.com/en/compare/bolt-grade-8-8-vs-10-9 - Case hardening vs through hardening: which one for screws and bolts?: The two main processes on our continuous mesh-belt furnace — choose by what the part has to do, not by maximum hardness alone. https://vsheattreatment.com/en/compare/case-hardening-vs-through-hardening - Annealing vs tempering vs normalizing: which one does your part need?: The three most-confused words in heat treatment. They are different jobs at different stages — mixing them up gets you an out-of-spec part. https://vsheattreatment.com/en/compare/annealing-vs-tempering-vs-normalizing - Carbonitriding vs carburizing: which case-hardening for fasteners?: Two ways to diffuse elements into the surface of low-carbon steel on a continuous mesh-belt line — they differ in temperature, case depth and distortion. https://vsheattreatment.com/en/compare/carbonitriding-vs-carburizing - Barrel plating vs rack plating: how small fasteners are actually plated: We run both lines in house. This page explains which one your part belongs on, and what changes on the drawing and in the price when the answer is rack. https://vsheattreatment.com/en/compare/barrel-vs-rack-plating - Quenching vs tempering: two halves of one process: One of the most searched pairs in heat treatment — and the question is framed wrongly. Here is what each step actually does, and which one decides the hardness you ordered. https://vsheattreatment.com/en/compare/quenching-vs-tempering - SCM435 vs SCM440: one alloy step apart, and it shows: Both are chromium–molybdenum steels from the same family. This page explains what the roughly 0.05% difference in carbon actually changes on a real fastener. https://vsheattreatment.com/en/compare/scm435-vs-scm440 - Class 10.9 vs 12.9: what you gain, and what you take on: The buyer’s question is not "which is stronger". It is whether roughly 17% more strength is worth every condition that comes with it. https://vsheattreatment.com/en/compare/bolt-grade-10-9-vs-12-9 - Zinc plating vs hot-dip galvanizing: which one does your fastener need?: We run Cr3+ zinc electroplating in-house and we do not own a galvanizing kettle. This page compares them straight, including the cases where the answer is not us. https://vsheattreatment.com/en/compare/zinc-plating-vs-hot-dip-galvanizing - Zinc phosphate vs manganese phosphate: match the coating to the job it does: We run both systems in-house, so this page compares them by function rather than by colour — and says which jobs should not be phosphated at all. https://vsheattreatment.com/en/compare/zinc-phosphate-vs-manganese-phosphate - Carburising vs nitriding: what a screw, nut or bolt actually gets: We case-harden with carbon on a continuous mesh-belt line and we do not run nitriding. This page shows why most small parts take the first route. https://vsheattreatment.com/en/compare/carburising-vs-nitriding - Zinc plating vs zinc-nickel: when is the upgrade worth paying for?: We plate Cr3+ zinc in-house and we do not have a zinc-nickel bath. This page explains when a spec should genuinely call for Zn-Ni and when plain zinc is enough. https://vsheattreatment.com/en/compare/zinc-plating-vs-zinc-nickel - S45C vs SCM440: which steel should you harden?: A practical decision page for design, purchasing and QC, with realistic service ranges and section-size limits. https://vsheattreatment.com/en/compare/s45c-vs-scm440 ## Knowledge - Knowledge: Deep-dive articles on hardening, metal coloring, corrosion protection and metallurgy basics — written from 30+ years of shop-floor experience. https://vsheattreatment.com/en/knowledge - Heat Treatment & Hardening Explained: What heat treatment is, why steel can be hardened, and how the quench-and-temper process works — written for screws, nuts and bolts. https://vsheattreatment.com/en/knowledge/heat-treatment-hardening-guide - Case Hardening: Carburizing, Nitriding & Carbonitriding: When you need a hard, wear-resistant surface over a tough impact-resistant core — understand the three case-hardening routes and how to choose. https://vsheattreatment.com/en/knowledge/case-hardening-carburizing-nitriding - What Is HRC? Metal Hardness HRC, HV, HB with Conversion Table: HRC is the Rockwell C hardness scale, measured with a 120° diamond cone at 150 kgf and usable from about 20 to 65 HRC. Includes an HRC ↔ HV ↔ HB ↔ tensile conversion table and the reference values for each bolt property class. https://vsheattreatment.com/en/knowledge/metal-hardness-hrc-hv-hb - How Cr3+ Zinc Plating Protects Against Rust: Why zinc-plated screws don’t rust, what the passivation colors mean, and why Cr3+ is the safer choice. https://vsheattreatment.com/en/knowledge/zinc-plating-cr3-guide - Metal Coloring: Black Oxide, Zinc Colors and Anodizing: How to actually change the color of metal — steel and aluminum — which process gives which color, and how to choose. https://vsheattreatment.com/en/knowledge/metal-coloring-guide - Phosphate Coating: Zinc vs Manganese: What the gray-black phosphate surface is for, how it differs from zinc plating, and choosing zinc vs manganese. https://vsheattreatment.com/en/knowledge/phosphate-coating-guide - Salt Spray Test (ASTM B117) — How to Read It: The salt-fog corrosion test: what the “hours” number means and how much to trust it. https://vsheattreatment.com/en/knowledge/salt-spray-test-astm-b117 - Fastener Steel Grades: S45C, SCM435, SUS304: The popular fastener steels — which can be hardened, which resist corrosion, and how to choose. https://vsheattreatment.com/en/knowledge/fastener-steel-grades - Hydrogen Embrittlement and Baking: Why hard screws sometimes snap by themselves after assembly — understanding hydrogen embrittlement and how to prevent it. https://vsheattreatment.com/en/knowledge/hydrogen-embrittlement-baking - Choosing the Right Finish for Screws, Nuts and Bolts: A decision guide: should your part be zinc-plated, blackened, phosphated or hardened — and what factors decide. https://vsheattreatment.com/en/knowledge/choosing-finish-for-fasteners - How Hard Can SCM440, SCM435 and S45C Get? Choosing a Steel Grade: S45C tops out near 50–58 HRC but is specified at 40–55 HRC in service. A 13-grade table for small parts separating the as-quenched ceiling from the after-temper value, plus which stainless grades harden at all. https://vsheattreatment.com/en/knowledge/hardening-by-steel-grade - Why Parts Warp After Hardening—and How to Prevent It: Distortion is the classic hardening headache, especially on thin, long parts. Here is what causes it and how we keep dimensions in tolerance. https://vsheattreatment.com/en/knowledge/hardening-distortion-fix - What Is Induction Hardening, and When to Use It: Induction hardening heats only a chosen zone with a high-frequency field, hardening the surface fast and repeatably—ideal for shafts, pins and part ends. https://vsheattreatment.com/en/knowledge/induction-hardening-guide - Annealing vs Normalizing vs Tempering: What Is the Difference?: Not every heat treatment makes steel harder—some soften it, refine grain or restore toughness. Here is how these three differ. https://vsheattreatment.com/en/knowledge/annealing-normalizing-tempering - Decarburization: The Invisible Loss of Surface Carbon in Hardening: Decarburization is when the steel surface loses carbon during heating, leaving a soft skin even when the core hardens well. It is preventable—if you catch it. https://vsheattreatment.com/en/knowledge/decarburization-explained - Zinc Plating Colour Chart: White, Blue, Yellow, Rainbow, Black, Green: The colour of zinc plating comes from the chromate passivation layer on top—it is not just looks; it also signals corrosion resistance. Here is the chart. https://vsheattreatment.com/en/knowledge/zinc-color-chart - How Long Does Zinc Plating Last? Salt-Spray Hours, Explained: The anti-rust life of zinc plating is not a fixed number—it depends on zinc thickness, chromate type and the real service environment. https://vsheattreatment.com/en/knowledge/zinc-corrosion-lifespan - Best Rust Protection for Screws and Bolts: Zinc vs Phosphate vs Black Oxide: There is no single best finish for fasteners—it depends on budget, environment and looks. Here are the trade-offs side by side. https://vsheattreatment.com/en/knowledge/best-anti-rust-for-fasteners - RoHS and Cr6-Free: Why Exports Need Trivalent Zinc Plating: Hexavalent chromium (Cr6) is restricted under RoHS, so modern zinc plating uses trivalent (Cr3+) chromate. Here is what that means for you. https://vsheattreatment.com/en/knowledge/rohs-cr6-free-compliance - Black Oxide vs Phosphate (Black): What Is the Difference?: A black finish can come from several routes. Black oxide and black phosphate differ in surface, corrosion resistance and cost. This guide helps you choose. https://vsheattreatment.com/en/knowledge/black-oxide-vs-phosphate - Manganese vs Zinc Phosphate: Differences and When to Use Each: Phosphate comes in several types; the two main ones—manganese and zinc—differ in surface, colour and purpose. Here is which job suits which. https://vsheattreatment.com/en/knowledge/manganese-vs-zinc-phosphate - Phosphate Primer Before Paint: Why Paint Adheres Better: Before paint or powder coat, a phosphate primer makes paint grip harder and slows rust under the paint film. Here is how it works. https://vsheattreatment.com/en/knowledge/phosphate-pre-paint-primer - Measuring Coating Thickness: How It Is Done and Why It Matters: Coating thickness directly drives quality and corrosion resistance. Here is how it is measured and why it must be controlled. https://vsheattreatment.com/en/knowledge/coating-thickness-measurement - Effective Case Depth: 550 HV, ISO 2639 and ISO 18203:2026 Explained: Effective versus total case depth, the 550 HV hardness traverse, and the transition from legacy ISO 2639 to current ISO 18203:2026—with an unambiguous callout example. https://vsheattreatment.com/en/knowledge/case-depth-measurement - How to Read a Metal Test Certificate: The certificate that ships with hardened/tested parts carries several values worth reading—to confirm the work met spec. https://vsheattreatment.com/en/knowledge/reading-test-certificate - Microstructure Analysis: Metallography Steps and How to Read Steel Phases: From section selection, mounting, grinding, polishing and etching to ferrite, pearlite and martensite—use metallography to verify heat treatment, case depth and failures. https://vsheattreatment.com/en/knowledge/microstructure-analysis-guide - Bulk Plating for Small Parts: Minimum Order, Lead Time, Nationwide Shipping: The questions customers ask most before sending work—minimum quantity, turnaround, shipping and pricing—for high-volume screws, nuts and bolts. https://vsheattreatment.com/en/knowledge/bulk-plating-faq - Preparing Parts Before Plating: A Guide for Fastener Makers (OEM): Good part preparation before plating yields a clean, uniform result with fewer problems. Here is what OEM fastener shops should know. https://vsheattreatment.com/en/knowledge/prepare-parts-before-plating - Automotive Metal Finishing: The Standards and Finishes OEMs Expect: Automotive parts carry tighter requirements for corrosion, documentation and consistency than general work. Here is what the automotive supply chain looks for. https://vsheattreatment.com/en/knowledge/automotive-finishing-standards - ISO 9001 in a Plating Shop: How It Affects Quality: ISO 9001 is not just a certificate on the wall—it is the system that keeps plating consistent, traceable and fixable in a structured way. https://vsheattreatment.com/en/knowledge/iso-9001-in-plating - Zinc Plating vs Hot-Dip Galvanizing vs Chrome: Which to Choose: Compare electroplated zinc (Cr3+), hot-dip galvanizing and chrome plating on corrosion protection, thickness, cost and fit — with a buyer’s guide for screws, nuts and bolts. https://vsheattreatment.com/en/knowledge/zinc-vs-galvanizing-vs-chrome - How to Choose a Heat-Treatment & Plating Partner in Thailand (OEM & Foreign Factories): Criteria for choosing a hardening / zinc-plating / phosphate subcontractor in Thailand — standards, certificates, capacity, language and export compliance for OEM and foreign-owned factories. https://vsheattreatment.com/en/knowledge/choosing-plating-partner-thailand - Steel Microstructure Explained: Ferrite, Pearlite, Austenite & Martensite: Understand the phases inside steel — ferrite, pearlite, austenite, martensite and bainite — and why they decide the hardness and toughness of a heat-treated part. https://vsheattreatment.com/en/knowledge/steel-microstructure-phases - Tempering & Temper Colors of Steel Explained: Why steel must be tempered after hardening, how temper temperature sets the final hardness, and what the "temper colors" mean — with a real color chart. https://vsheattreatment.com/en/knowledge/tempering-and-temper-colors - How Much Does Heat Treatment (Hardening) Cost? Price Factors and How to Order: Hardening is not a fixed-price service — it depends on the material, the hardness you need, the quantity and any follow-on plating. Here is what drives the price, plus how to prepare so you get a quote fast. https://vsheattreatment.com/en/knowledge/hardening-cost-and-how-to-order - How Much Does Zinc Plating Cost? Price Factors and How to Order: Zinc plating price depends on the color you choose (white/black/rainbow), the coating thickness, the salt-spray spec, the quantity and the part shape. Here is what drives the price, plus how to get a quote fast. https://vsheattreatment.com/en/knowledge/zinc-plating-cost-and-how-to-order - What Is Blackening (Black Oxide / Black Phosphate)? Types, Benefits and Cost: Blackening turns a steel surface black, gives basic rust protection and a clean matte look. Here are the types of black finishing (black phosphate / black oxide), their benefits, uses and how to get a price. https://vsheattreatment.com/en/knowledge/black-finish-blackening-guide - Which Hardening Method Should You Choose? A Comparison Guide: There are several hardening methods — through hardening, case hardening (carburizing) and induction. This guide compares them and helps you choose the right one for your part and material. https://vsheattreatment.com/en/knowledge/which-hardening-method-to-choose - Can Stainless Steel Be Hardened? And Does It Need Plating?: Stainless grades harden very differently, and most do not need anti-rust plating. This guide explains which grades truly harden, which can only be passivated, and when an extra coating makes sense — for small screws, nuts and bolts. https://vsheattreatment.com/en/knowledge/stainless-steel-hardening-finishing - Heat Treating Springs and Spring Steel — How It Works: A spring must be hard *and* springy at once, so it is heat treated differently from ordinary screws. This guide covers spring-steel grades (SUP, SK5, 65Mn), the two hardening routes, and the defects that make springs fail early. https://vsheattreatment.com/en/knowledge/spring-steel-heat-treatment - Does Plating Make Threads Loose or Tight? Coating Thickness and Thread Fit: Plating adds thickness onto threads, and without control a nut can bind or fit too loose. This guide explains zinc coating thickness, the "4× rule" on threads, tolerance allowances, and the effect on tightening torque. https://vsheattreatment.com/en/knowledge/plating-thickness-thread-fit - Heat-Treatment Defects: Troubleshooting Low Hardness, Cracks and Distortion: A practical diagnostic guide for low or scattered hardness, quench cracks, delayed fractures, distortion and decarburization—with the evidence needed for a real root-cause investigation. https://vsheattreatment.com/en/knowledge/heat-treatment-defects-troubleshooting - How to Write a Zinc-Plating Specification: A Checklist for Purchasing and QC: A usable zinc-plating callout needs more than colour: material, hardness, standard, thickness, passivation/topcoat, salt-spray criteria, measurement location, thread fit and certification. https://vsheattreatment.com/en/knowledge/zinc-plating-specification-checklist - How to Specify Phosphate Coating: Zinc vs Manganese and an Inspection Checklist: A practical phosphate-coating callout: substrate, zinc/manganese type, coating mass, oil or sealer, end use, test locations and acceptance criteria aligned with ISO 9717:2024. https://vsheattreatment.com/en/knowledge/phosphate-coating-specification-checklist - How to Specify Hardness on a Drawing: A Checklist for Engineers and Purchasing: Writing "harden it" is not enough. Specify a hardness range (HRC/HV), the measurement location and method, effective case depth per ISO 18203, and distortion and decarburization limits — with a copy-paste callout example. https://vsheattreatment.com/en/knowledge/hardening-specification-checklist - Hardening SUJ2 Bearing Steel (100Cr6 / AISI 52100) for Small Parts: SUJ2 is a high-carbon chromium bearing steel that through-hardens to ~60–62 HRC — ideal for pins, rollers, bushings, small shafts and balls. Understand the quench-and-temper recipe, dimensional stability, retained austenite and when to sub-zero treat. https://vsheattreatment.com/en/knowledge/suj2-bearing-steel-hardening - Which Process Reaches ~1000 HV Surface Hardness: Nitriding vs Carburizing: An informational answer: surface hardness around ~900–1100 HV comes from nitriding/nitrocarburizing, not ordinary hardening — why it gets that hard, how it compares with carburizing, and the case-depth trade-off. https://vsheattreatment.com/en/knowledge/nitriding-surface-hardness-1000hv - Quench Media Guide: Oil vs Water vs Polymer for Fasteners: Quench oil, water and polymer quenchants extract heat at very different rates — how each one affects hardness, distortion and crack risk, and why bulk screws, nuts and bolts are quenched in oil. https://vsheattreatment.com/en/knowledge/quench-media-guide - Austempering and Martempering: Why Salt-Bath Routes Exist: Austempering produces bainite and needs no tempering; martempering (marquenching) produces martensite with far less distortion. How they differ, what they fix, and why a property-class bolt cannot simply be switched to one. https://vsheattreatment.com/en/knowledge/austempering-and-martempering - The Plating Line Step by Step: Degrease, Pickle, Activate, Plate, Passivate, Seal, Bake: Follow your own parts through a zinc plating line — what every tank is for, why there are so many rinses, where hydrogen-relief baking belongs, and what evidence a buyer can ask for at each stage. https://vsheattreatment.com/en/knowledge/plating-line-process-steps - Mesh-Belt vs Batch Furnace: Why Bulk Fasteners Run Continuous: Continuous mesh-belt lines and batch or sealed-quench furnaces differ in uniformity, part size, volume and recipe flexibility. How to tell which architecture suits the part you actually have. https://vsheattreatment.com/en/knowledge/mesh-belt-vs-batch-furnace - Alkaline vs Acid Zinc Plating: Throwing Power, Thickness and Hydrogen Risk: Alkaline (cyanide-free zincate) and acid (chloride) zinc baths deposit the same metal very differently — thickness distribution on complex parts, brightness, speed and how much hydrogen reaches the steel. https://vsheattreatment.com/en/knowledge/alkaline-vs-acid-zinc - How to Choose a Plating Supplier in Thailand: Documents, Questions and the Trial Lot: A buyer-side guide: write a specification that makes quotes comparable, read a coating designation properly, ask for the right documents, run a real plant visit, and design a trial lot that proves the process rather than a hand-made sample. https://vsheattreatment.com/en/knowledge/how-to-choose-plating-supplier-thailand ## Free Tools - Free Tools: A hardness conversion calculator and a steel-grade heat-treatment selector — built by the plant team that uses these numbers every day. https://vsheattreatment.com/en/tools - Hardness Converter HRC ↔ HV ↔ HB: Convert Rockwell, Vickers, Brinell and approximate tensile strength per ASTM E140 / ISO 18265, with the full reference chart. https://vsheattreatment.com/en/tools/hardness-converter - Which Steel Grades Harden — and How Far: Pick a grade (S45C, SCM435, SUJ2, SUS304…) and see the right process and realistic hardness range for small parts. https://vsheattreatment.com/en/tools/steel-grade-hardness - Fastener Weight: pcs ↔ kg: Convert piece counts to kilograms from DIN/ISO dimensions (M3–M24), with a per-1000-pcs weight chart — estimate batch weight before requesting a quote. https://vsheattreatment.com/en/tools/fastener-weight - Finishing Specification Builder for Purchasing and QC: Build a zinc-plating, effective case-depth, phosphate-coating or failure-investigation callout; copy it or save as PDF for RFQ and QC. https://vsheattreatment.com/en/tools/spec-builder - Salt Spray Test Plan Builder: Build a salt-spray test request with method, duration, inspection interval, specimen count, corrosion criteria and reporting. Copy or save it for RFQ and QC. https://vsheattreatment.com/en/tools/salt-spray-planner - Coating thickness → thread fit (GO/NO-GO): Check whether a zinc-plating thickness will still pass the GO gauge on M3–M24 external threads by tolerance class (6g/6h/6e). Reference estimator using the ISO 4042 4× rule. https://vsheattreatment.com/en/tools/thread-fit - Hydrogen Embrittlement — is baking required?: Check whether electroplated fasteners need hydrogen de-embrittlement baking by property class, hardness (HRC/HV) or tensile strength, with the reference bake window per ISO 4042 / ASTM B850. https://vsheattreatment.com/en/tools/hydrogen-bake - Bolt Tightening Torque & Proof Load: Calculate tightening torque, proof load, tensile stress area and target preload for M3–M24 bolts by property class (8.8/10.9/12.9) and friction condition. Free reference tool. https://vsheattreatment.com/en/tools/bolt-torque - Thread Engagement Length: Minimum engaged thread length so a tapped hole or nut strips at or above the bolt tensile fracture — by size, property class (8.8/10.9/12.9) and internal-thread material. Free reference tool. https://vsheattreatment.com/en/tools/thread-engagement - Bolt Size Estimator (from load): Enter an axial working load and safety factor and get the smallest metric bolt (M3–M24) and property class (8.8/10.9/12.9) whose proof load covers it. Free ISO 898-1 reference tool. https://vsheattreatment.com/en/tools/bolt-size - Bolt Property Class — Mechanical Properties (ISO 898-1): Reference table of ISO 898-1 bolt strength classes 4.6, 4.8, 5.8, 8.8, 10.9, 12.9 — tensile Rm, yield, Vickers HV and Rockwell HRC hardness, and elongation. Which hardness each class needs. https://vsheattreatment.com/en/tools/property-class ## Case Studies - Case Studies: Real successes with customers across industries https://vsheattreatment.com/en/case-studies - Heat-treating 120 tons of automotive bolts/month: A Tier-1 automotive parts maker sends M10 bolts to be heat-treated to 38–42 HRC, 120 tons/month, weekly delivery. https://vsheattreatment.com/en/case-studies/automotive-bolts - Cr3+ zinc plating for export anchor bolts: A bolt manufacturer exporting to Europe needed RoHS-compliant zinc plating with a 240-hour salt spray rating. https://vsheattreatment.com/en/case-studies/construction-anchors - High-volume hardening of farm-machinery fasteners: A farm-machinery maker needed pins and bolts at a consistent 55–58 HRC across every lot, without brittleness. https://vsheattreatment.com/en/case-studies/agriculture-fasteners ## News & Articles - News & Articles: Insights on metallurgy and surface-treatment processes https://vsheattreatment.com/en/news - Cr3+ vs Cr6+ — what every manufacturer should know: Why industry is moving from hexavalent (Cr6+) to trivalent (Cr3+) chromium passivation — the compliance rules, corrosion performance, and what it means for small fasteners and your supply chain. https://vsheattreatment.com/en/news/cr3-vs-cr6 - Heat Treatment 101: choosing the right process: Hardening, tempering, annealing, normalizing — what each heat-treatment process actually does, and how to choose the right one for your steel grade and application. https://vsheattreatment.com/en/news/heat-treatment-101 - Salt Spray Test: read the results in 5 minutes: How to read a salt-spray (ASTM B117) report — hours to white rust and red rust, what the numbers really mean, and how they relate to real-world corrosion protection. https://vsheattreatment.com/en/news/salt-spray-explained ## About Us - About Us: 32 years on Thailand’s metal-finishing journey https://vsheattreatment.com/en/about ## Contact - Contact: Our team replies with a tailored quote within 24 hours https://vsheattreatment.com/en/contact ## Heat Treatment & Metal Finishing Glossary - Heat Treatment & Metal Finishing Glossary: Plain-language definitions of the metallurgy, hardening and plating terms used across our services and knowledge base. https://vsheattreatment.com/en/glossary ## Finishes & Colors - Finishes & Colors: Pick the finish that fits your use and budget — corrosion protection, looks, preserved thread size. https://vsheattreatment.com/en/finishes ## How It Works - How It Works https://vsheattreatment.com/en/process ## FAQ - FAQ https://vsheattreatment.com/en/faq ## Gallery - Gallery https://vsheattreatment.com/en/gallery ## Awards - Awards https://vsheattreatment.com/en/awards ## Datasheets - Datasheets https://vsheattreatment.com/en/datasheets ## Heat-Treatment and Metal-Finishing Specification Pack - Heat-Treatment and Metal-Finishing Specification Pack: Ready-to-use purchasing, engineering and QC forms that reduce missing requirements, interpretation errors and rework. https://vsheattreatment.com/en/resources ## Privacy - Privacy https://vsheattreatment.com/en/privacy ## Site map - Site map: Every page on this site, on one page, grouped by topic. https://vsheattreatment.com/en/site-map