SYZ ENGINEERING PRELIMINARY DESIGN TOOL · REFERENCE-BASED ESTIMATE
Hardness ↔ Tensile Strength Reference Converter
Estimate Brinell hardness and ultimate tensile strength from a Rockwell C (HRC) reading for quenched & tempered low-alloy steel such as 4130/4140, using interpolation between published reference points (20–50 HRC).
METALLURGY REFERENCE · APPROXIMATE SAE J417 / ASTM E140 CONVERSION RANGE
Hardness ↔ Tensile Strength Reference Converter
Interpolates between published approximate HRC–HB–tensile reference points for quenched & tempered low-alloy steel (e.g. 4130/4140). Not a substitute for the current edition of ASTM E140.
[20 to 50 HRC]
SYZ 4130/4140 normalized & tempered rod end body standard: HRC 32–38. Range capped at 50 HRC — the linear approximation breaks down above this and ASTM E140 requires the full published table.
| HRC | ≈ HB | ≈ Rm (MPa) |
|---|---|---|
| 20 | 225 | 772 |
| 25 | 253 | 862 |
| 30 | 286 | 1000 |
| 35 | 327 | 1145 |
| 40 | 371 | 1289 |
| 45 | 421 | 1451 |
| 50 | 481 | 1636 |
Estimated Ultimate Tensile Strength (Rm)
≈1,116 MPa
✔
≈161,900 PSI · Brinell ~319 HB · Standard 4130/4140 quenched & tempered range
Reference-Table Interpolation (not a single ASTM formula)
Standard Reference
ASTM E140 (“Standard Hardness Conversion Tables for Metals”) publishes conversion tables for non-austenitic steels — it does not publish a single linear equation across the full hardness range.
Calculation Method
Piecewise-linear interpolation between the reference points shown in the table, approximating commonly published SAE J417 / ASTM E140 conversion ranges for quenched & tempered alloy steel.
SYZ Quality Note
Rod end body (4130/4140 forged, Q&T): controlled to HRC 32–38. Bearing ball (52100/GCr15): through-hardened to HRC 58–62 — outside the reliable range of this linear-region converter; consult the full ASTM E140 table for hardness above 50 HRC.
Assumptions & Limitations
- Reference points are approximate published values for quenched & tempered alloy steel — actual conversion is material- and process-dependent.
- Not valid for austenitic stainless steel, cast iron, or non-ferrous alloys.
- Conversions are approximations, never a replacement for direct mechanical (tensile) testing on safety-critical parts.
STATIC REFERENCE DATA
Reference Table (also shown in the calculator above)
Precomputed values from the exact formula used above — useful as a quick lookup without re-entering inputs.
| HRC | ≈ HB | ≈ Rm (MPa) | ≈ Rm (PSI) |
|---|---|---|---|
| 20 | 225 | 772 | 111,970 |
| 25 | 253 | 862 | 125,043 |
| 30 | 286 | 1000 | 145,038 |
| 35 | 327 | 1145 | 166,069 |
| 40 | 371 | 1289 | 186,954 |
| 45 | 421 | 1451 | 210,470 |
| 50 | 481 | 1636 | 237,282 |
WORKED EXAMPLE
Checking SYZ Rod End Body Hardness Spec
SYZ’s 4130/4140 forged, quenched & tempered rod end body is controlled to HRC 32–38. What tensile strength range does that correspond to?
- HRC 32 interpolates between the 30 HRC (1,000 MPa) and 35 HRC (1,145 MPa) table rows → ≈ 1,058 MPa (≈153,450 PSI).
- HRC 38 interpolates between the 35 HRC (1,145 MPa) and 40 HRC (1,289 MPa) table rows → ≈ 1,231 MPa (≈178,600 PSI).
- So the HRC 32–38 spec band corresponds to an estimated ultimate tensile strength range of roughly 1,058–1,231 MPa (153–179 ksi) — consistent with typical 4130/4140 quenched & tempered chromoly performance.
- This is an approximation for quick reference only; certified mechanical properties come from the mill test report, not from this converter.
Related reading: Metallurgy & Quality Control →
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