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.
These are the grades we actually run as small parts at bulk volume. Every figure in the table is read from the same source the on-site calculators use, so the page and the tool cannot disagree. The ranges are typical industry values for small sections and depend on the part, the section size, the quench and the governing specification — your drawing decides, not this table.
Grade comparison
Scroll the table sideways on a narrow screen.
| Grade (JIS) | Closest equivalents | Carbon (%) | Steel family | Hardening route | Typical hardness in service (HRC) | Property classes | ISO 4042 bake |
|---|---|---|---|---|---|---|---|
| S20C | AISI 1020 / DIN C22 | 0.18–0.23 | Plain carbon steel | Carburizing (case hardening) | 55–60 HRC | — | Yes |
| S45C | AISI 1045 / DIN C45 | 0.42–0.48 | Plain carbon steel | Quench and temper | 40–55 HRC | 8.8 | Depends |
| SCM435 | AISI 4135 / DIN 34CrMo4 | 0.33–0.38 | Alloy steel (Cr / Cr–Mo) | Quench and temper | 33–44 HRC | 10.9, 12.9 | Yes |
| SCM440 | AISI 4140 / DIN 42CrMo4 | 0.38–0.43 | Alloy steel (Cr / Cr–Mo) | Quench and temper | 28–48 HRC | 10.9, 12.9 | Yes |
| SCr440 | AISI 5140 / DIN 41Cr4 | 0.38–0.43 | Alloy steel (Cr / Cr–Mo) | Quench and temper | 28–45 HRC | 10.9, 12.9 | Yes |
| SWCH10B21 | AISI 10B21 | 0.18–0.23 + B | Boron cold-heading steel | Quench and temper | 28–40 HRC | 8.8 | No |
| SWCH10B33 | AISI 10B33 | 0.30–0.36 + B | Boron cold-heading steel | Quench and temper | 32–42 HRC | 10.9 | Yes |
| SUP9 | AISI 5155 / DIN 55Cr3 | 0.52–0.60 | Spring steel | Quench and temper + Austempering | 40–50 HRC | — | Yes |
| SK85 (SK5) | AISI 1084–1086 / DIN C85 | 0.80–0.90 | Tool / high-carbon steel | Quench and temper + Austempering | 45–60 HRC | — | Yes |
| SUJ2 | AISI 52100 / DIN 100Cr6 | 0.95–1.10 | Bearing steel | Quench and temper | 58–64 HRC | — | Yes |
| SKS3 | AISI O1 (近) / DIN 100MnCrW4 | 0.90–1.00 | Tool / high-carbon steel | Quench and temper | 56–62 HRC | — | Yes |
| SUS420J2 | AISI 420 / DIN X30Cr13 | 0.26–0.40 | Stainless steel | Quench and temper | 45–52 HRC | — | Yes |
| SUS304 | AISI 304 / DIN X5CrNi18-10 | ≤ 0.08 | Stainless steel | Not hardenable by heat treatment | Not applicable | — | No |
ISO 4042 calls for embrittlement-relief baking on electroplated fasteners at property class 10.9 and above, or at roughly 390 HV (≈ 40 HRC) and above. Many customer specifications set a lower trigger — the drawing decides, not this page.
Hardness values are typical industry ranges for the small sections we process, and depend on the part, the section size, the quench and the governing specification. They are not a guarantee and do not replace your drawing or standard.