Steel 8640-CR (Cold rolled)
Supply condition
AISI/SAE 8640 · UNS G86400
Cold-reduced strip/sheet with tight thickness and a smooth surface, usually supplied soft-annealed for later forming and hardening.
Values for the CR condition
Other 8640 tempers and conditions
8640 is listed in 10 conditions; see the grade overview at 8640.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Temper | Softest condition (full/spheroidize anneal ~840 °C, furnace cool) — best for deep machining, cold forming or thread rolling before hardening. | 380 | 695 | 22.5 | 184 HB | — |
HRDefault Hot rolled | Standard as-rolled bar for parts that will be heat treated after machining; cheapest stock form. | 570 | 860 | 19 | 20 HRC | — |
CRThis page Cold rolled | Cold-reduced strip/sheet with tight thickness and a smooth surface, usually supplied soft-annealed for later forming and hardening. | 620 | 760 | 13 | 17 HRC | 7.8 % IACS |
Heat Treat State | Normalized ~900 °C and air cooled: uniform fine grain and moderate strength; typical pre-treatment before machining and final Q&T of forgings. | 690 | 930 | 22 | 27 HRC | — |
Cold drawn | Cold-drawn bar with better size tolerance, straightness and surface than HR; higher yield strength but residual stress can cause distortion on machining. | 760 | 895 | 14 | 25 HRC | 7.8 % IACS |
Q&T to 28–32 HRC | Tough mid-hardness condition (temper ≈600 °C) for drill-pipe tool joints, sour-service and welded-then-tempered assemblies. | 860 | 965 | 19 | 30 HRC | 7.8 % IACS |
Quenched and tempered | General commercial condition: oil quench from ~830 °C and temper ~540 °C for a balanced strength/toughness shaft or gear blank. | 1,000 | 1,100 | 17 | 35 HRC | — |
Q&T to 32–36 HRC | Common shaft/gear-blank hardness giving high fatigue strength while still machinable with carbide tooling. | 1,000 | 1,105 | 16 | 34 HRC | 7.6 % IACS |
Q&T to 38–42 HRC | High-strength condition (temper ≈425 °C) for heavily loaded pins, sprockets and fasteners where wear resistance outweighs toughness. | 1,275 | 1,380 | 14 | 40 HRC | — |
Q&T to 48–52 HRC | Low-temper (≈205–260 °C) condition for maximum hardness/wear in small sections; notch-sensitive and difficult to machine — grind to size. | 1,620 | 1,795 | 11 | 50 HRC | — |
What is 8640-CR?
8640-CR is 8640 supplied in the CR condition — cold-reduced strip/sheet with tight thickness and a smooth surface, usually supplied soft-annealed for later forming and hardening. 8640-CR has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 78% of steel grades. Elongation at break is 13% and the elastic modulus is 205 GPa (29.7 Msi). 8640-CR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; CR is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 620 MPa (89.9 ksi), better than 78% of steel grades
Limitations
- Limited ductility — 13%, worse than 78% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
8640-CR properties
Typical room-temperature values for 8640-CR; 23 are specific to this condition. Other listed values are 8640 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8640-CR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
8640-CR has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 78% of steel grades. Elongation at break is 13% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8640-CR is rated for continuous service to 300°C (572 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
8640-CR conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 8640-CR takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
8640-CR's machinability is good (58/100, better than 75% of steel grades); weldability fair (40/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8640-CR
Is 8640 easy to machine?
Machine in the annealed or ≤32 HRC Q&T condition with carbide tooling and rigid setups; rough before hardening and leave grind stock for finish sizes.
Can 8640 be welded?
Weldable with low-hydrogen consumables but requires ~200–300 °C preheat, interpass control and post-weld temper below the original tempering temperature to avoid martensitic cracking.
Can 8640 be formed, bent or molded?
Cold forming only in the annealed state and with generous bend radii; hot forge at 1050–1200 °C then normalize before final heat treatment.
What surface finishes work on 8640?
No natural corrosion protection — apply black oxide, phosphate + oil, zinc or hard-chrome plating; bake plated parts above ~38 HRC to relieve hydrogen embrittlement.
8640 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 |
|---|---|---|
| C | 0.38 – 0.43 | 0.4 |
| 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 |
| Pmax, SAE J404 wrought bar | ≤ 0.04 | — |
| Smax; 8640H/resulfurized variants differ | ≤ 0.04 | — |
| Fe | balance | — |
8640-CR — frequently asked
What is 8640-CR used for?
8640-CR is typically used for gears, shafts and bolts. In short: workhorse Ni-Cr-Mo bar.
What is the yield strength of 8640-CR?
8640-CR has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 8640-CR easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in the annealed or ≤32 HRC Q&T condition with carbide tooling and rigid setups; rough before hardening and leave grind stock for finish sizes.
Can 8640-CR be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but requires ~200–300 °C preheat, interpass control and post-weld temper below the original tempering temperature to avoid martensitic cracking.
What surface finishes work on 8640-CR?
No natural corrosion protection — apply black oxide, phosphate + oil, zinc or hard-chrome plating; bake plated parts above ~38 HRC to relieve hydrogen embrittlement.
Can 8640-CR be formed, bent or molded?
Cold forming only in the annealed state and with generous bend radii; hot forge at 1050–1200 °C then normalize before final heat treatment.
What is the maximum service temperature of 8640-CR?
8640-CR is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 8640-HR and 8640-CD?
HR is the default condition — standard as-rolled bar for parts that will be heat treated after machining; cheapest stock form. CD: cold-drawn bar with better size tolerance, straightness and surface than HR; higher yield strength but residual stress can cause distortion on machining. Yield strength is 570 MPa in HR versus 760 MPa in CD.
Can FabDigit make parts in 8640-CR?
Yes — 8640-CR is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (tempering curves for 86xx steels) — ASM International (1991)
- SAE J1268 hardenability / typical mechanical property tables for 8640 — SAE International (2019)
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.