Steel 8637
AISI/SAE 8637 · UNS G86370
8637 is a through-hardening nickel-chromium-molybdenum alloy steel (UNS G86370) with higher carbon than the 8615/8617 carburizing grades, so strength comes from quench and temper rather than case hardening.
Reference datasheet — 8637 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT28-32HRC condition
8637 tempers and conditions
8637 is supplied in 13 conditions, soft to hard. QT28-32HRC is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
8637 is a through-hardening nickel-chromium-molybdenum alloy steel (UNS G86370) with higher carbon than the 8615/8617 carburizing grades, so strength comes from quench and temper rather than case hardening. It is used for heavily loaded shafts, gears and axles from hot-rolled, annealed, normalized, cold-drawn, induction-hardened or Q&T bar; the default Q&T condition reaches about 860 MPa yield, 965 MPa tensile, 19 % elongation and 285 HB (30 HRC), with service to 400 °C. Weldability is poor (score 35) and machinability drops to about 50 % of 1212, so 4140 is the common alternative where broader availability matters. 8637 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). 8637 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 19% and the elastic modulus is 205 GPa (29.7 Msi).
What is 8637 used for?
- heavy-duty shafts
- gears
- axles
- high-strength fasteners
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 properties
Typical room-temperature values for 8637-QT28-32HRC; bars are the position among steel grades.
Physical3
8637 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 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 19% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8637 is rated for continuous service to 400°C (752 °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 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 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's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (35/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 8637 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 8637
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 8637 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G86370
How much does 8637 cost?
8637 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
8637 — frequently asked
What is 8637 used for?
8637 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?
8637 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 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 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?
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 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?
8637 is rated for continuous use to about 400°C (752 °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.
How much does 8637 cost?
8637 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.