Steel 8637-QT540
Heat-treated state
AISI/SAE 8637 · UNS G86370
QT540 = q&T 540 °C
Standard machinery temper: tough, ~30 HRC, good fatigue life for shafts and connecting rods.
Values for the QT540 condition
Other 8637 tempers and conditions
8637 is listed in 13 conditions; see the grade overview at 8637.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for heavy machining, cold forming or before re-hardening. | 400 | 660 | 22 | 187 HB | — |
Hot rolled | Cheapest stock form for parts that will be heat treated by the user after rough machining. | 470 | 760 | 20 | 217 HB | — |
Normalized | Uniform fine-grain structure with moderate strength; used as a pre-machining or as-supplied forging condition. | 620 | 900 | 20 | 26 HRC | — |
Cold drawn | Bright, size-accurate bar with raised yield strength for shafting that will not be re-heat-treated. | 650 | 760 | 14 | 223 HB | — |
Q&T 650 °C | Highest toughness/ductility temper for impact-loaded or low-temperature service. | 720 | 820 | 23 | 23 HRC | — |
QT28-32HRCDefault quenched and tempered to 28–32 HRC | Most commonly stocked/ordered condition: tough machinable bar for shafts, gears and hydraulic bodies. | 860 | 965 | 19 | 30 HRC | — |
QT540This page Q&T 540 °C | Standard machinery temper: tough, ~30 HRC, good fatigue life for shafts and connecting rods. | 860 | 965 | 20 | 30 HRC | — |
Induction hardened | Pick when a tough ~30 HRC core with a hard 55–58 HRC wear surface is needed on journals or splines. | 860 | 965 | 15 | 56 HRC | 7 % IACS |
quenched and tempered to 32–36 HRC | Higher-strength machinery band for gear blanks and heavily loaded pins where some machining remains. | 1,000 | 1,105 | 17 | 34 HRC | — |
Q&T 425 °C | Good strength/toughness compromise for heavily loaded gears and shafts. | 1,105 | 1,210 | 17 | 38 HRC | — |
quenched and tempered to 38–42 HRC | High-hardness through-hardened band for wear-critical shafts and tooling components; machining is difficult. | 1,180 | 1,310 | 14 | 40 HRC | — |
Q&T 315 °C | Very high strength for springs and highly stressed fasteners; still limited ductility. | 1,345 | 1,480 | 13 | 45 HRC | — |
Q&T 205 °C | Maximum hardness and wear resistance, low toughness — for wear surfaces, not shock-loaded parts. | 1,600 | 1,795 | 11 | 52 HRC | — |
What is 8637-QT540?
8637-QT540 is 8637 heat treated to QT540 — standard machinery temper: tough, ~30 HRC, good fatigue life for shafts and connecting rods. 8637-QT540 has a yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). 8637-QT540 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). QT28-32HRC is the default condition FabDigit quotes; QT540 is available on request or by drawing note.
Advantages
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
8637-QT540 properties
Typical room-temperature values for 8637-QT540; 12 are specific to this condition. Other listed values are 8637 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8637-QT540 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
8637-QT540 has a yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8637-QT540 is rated for continuous service to 425°C (797 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
8637-QT540 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 8637-QT540 takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 35%.
Manufacturability7
8637-QT540's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (35/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8637-QT540
Is 8637 easy to machine?
Machine at ≤32 HRC with rigid setups, carbide inserts and generous coolant; finish-grind after hardening for tight tolerances.
Can 8637 be welded?
Weldable only with care — preheat 200–300 °C, low-hydrogen consumables, and immediate post-weld temper below the part's tempering temperature.
Can 8637 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming limited to annealed/spheroidized bar with generous bend radii.
What surface finishes work on 8637?
No anodizing (ferrous): use black oxide, manganese phosphate, zinc or hard-chrome plating with 190 °C hydrogen bake-out above ~1000 MPa strength.
8637 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CSAE J404 heat analysis | 0.35 – 0.4 | 0.38 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.4 – 0.7 | 0.55 |
| Cr | 0.4 – 0.6 | 0.5 |
| Mo | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | 0.02 |
| Smax; H-grade/resulfurized variants differ | ≤ 0.04 | 0.02 |
| Fe | balance | — |
8637-QT540 — frequently asked
What is 8637-QT540 used for?
8637-QT540 is typically used for heavy-duty shafts, gears, axles and high-strength fasteners. In short: through-hardening 86xx grade; higher strength than 8630; 400 °C service limit.
What is the yield strength of 8637-QT540?
8637-QT540 has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is 8637-QT540 easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine at ≤32 HRC with rigid setups, carbide inserts and generous coolant; finish-grind after hardening for tight tolerances.
Can 8637-QT540 be welded?
With care — weldability is rated fair (35/100). Weldable only with care — preheat 200–300 °C, low-hydrogen consumables, and immediate post-weld temper below the part's tempering temperature.
What surface finishes work on 8637-QT540?
No anodizing (ferrous): use black oxide, manganese phosphate, zinc or hard-chrome plating with 190 °C hydrogen bake-out above ~1000 MPa strength.
Can 8637-QT540 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming limited to annealed/spheroidized bar with generous bend radii.
What is the maximum service temperature of 8637-QT540?
8637-QT540 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 8637 QT28-32HRC and 8637-QT205?
QT28-32HRC is the default condition — most commonly stocked/ordered condition: tough machinable bar for shafts, gears and hydraulic bodies. QT205: maximum hardness and wear resistance, low toughness — for wear surfaces, not shock-loaded parts. Yield strength is 860 MPa in QT28-32HRC versus 1,600 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.