Steel SCr440-A (Solution annealed)
Temper
JIS SCr440
Order fully annealed bar (197 HB typical, ≤229 HB) as the softened state for machining or cold heading, then quench and temper the finished part to reach service strength.
Values for the A condition
Other SCr440 tempers and conditions
SCr440 is listed in 11 conditions; see the grade overview at SCr440.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Pick spheroidize annealed bar, the softest state at 174 HB, for cold-headed bolts and cold extrusions where spheroidized carbides maximise cold formability; strength must come from later Q&T. | 370 | 600 | 28 | 174 HB | 8.5 % IACS |
AThis page Solution annealed | Order fully annealed bar (197 HB typical, ≤229 HB) as the softened state for machining or cold heading, then quench and temper the finished part to reach service strength. | 420 | 655 | 26 | 197 HB | — |
Hot rolled | Use hot-rolled bar as the cheapest stock form when you will quench and temper it yourself; dimensional and surface accuracy are lower and as-supplied yield is only 440 MPa. | 440 | 750 | 20 | 17 HRC | 8 % IACS |
Normalized | Choose normalized stock (about 870 °C, air cooled) to refine and homogenise the structure before further heat treatment, or for low to medium loaded parts at 470 MPa yield. | 470 | 790 | 22 | 20 HRC | — |
Cold drawn | Pick cold-drawn bright bar for small shafts and pins machined directly to size: work hardening raises yield to 680 MPa with tight tolerances, but elongation drops to 12%. | 680 | 790 | 12 | 21 HRC | 8 % IACS |
Q&T 28–32 HRC | Choose the toughness-biased 28–32 HRC quench-and-temper band for impact-loaded shafts and connecting rods, giving 830 MPa yield while keeping 17% elongation. | 830 | 1,000 | 17 | 30 HRC | 8 % IACS |
QTDefault Quenched and tempered | Specify the standard 830–880 °C oil quench plus 520–620 °C temper (269–331 HB) for shafts, gears and bolts that need combined strength and toughness at 860 MPa yield. | 860 | 1,030 | 16 | 31 HRC | — |
Induction hardened | Select a quenched-and-tempered core with an induction-hardened 52–58 HRC surface for journals, splines and gear flanks needing wear resistance and fatigue strength while the core stays tough. | 860 | 1,030 | 14 | 55 HRC | 8 % IACS |
Q&T 32–36 HRC | Use the strength-biased 32–36 HRC band for high-strength bolts, gear blanks and as the core condition before induction hardening; yield reaches 950 MPa at reduced machinability. | 950 | 1,100 | 15 | 34 HRC | — |
Q&T 40–45 HRC | Pick the low-temperature temper near 400 °C, giving 40–45 HRC and 1250 MPa yield, for small-section parts needing high strength and wear resistance; toughness and machinability drop clearly. | 1,250 | 1,400 | 12 | 43 HRC | — |
As-Quenched | Treat the as-quenched 55 HRC state as an intermediate step only — hard and brittle at 2% elongation, it must be tempered immediately to remove quenching stresses. | 1,550 | 1,980 | 2 | 55 HRC | 7 % IACS |
What is SCr440-A?
SCr440-A is SCr440 in the A temper — order fully annealed bar (197 HB typical, ≤229 HB) as the softened state for machining or cold heading, then quench and temper the finished part to reach service strength. SCr440-A has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 53% of steel grades. Elongation at break is 26% and the elastic modulus is 207 GPa (30 Msi). SCr440-A 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). QT is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
SCr440-A properties
Typical room-temperature values for SCr440-A; 12 are specific to this condition. Other listed values are SCr440 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCr440-A 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
SCr440-A has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 53% of steel grades. Elongation at break is 26% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCr440-A 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SCr440-A conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCr440-A takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
SCr440-A's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCr440-A
Is SCr440 easy to machine?
Machining is most economical in the annealed or normalised condition (≤229 HB); at around 30 HRC after quench and temper, coated carbide turning and milling still work, but above 40 HRC use grinding or CBN.
Can SCr440 be welded?
The carbon equivalent is high, so welding is generally not recommended; where it is unavoidable, preheat 200–300 °C, use low-hydrogen consumables and temper at 550–600 °C after welding.
Can SCr440 be formed, bent or molded?
Spheroidise-annealed bar can be cold-headed into bolts; hot forge at about 1100–1200 °C and normalize after forging to remove coarse grain.
What surface finishes work on SCr440?
Not anodizable; black oxide, phosphating, zinc plating or hard chrome are usual, with a post-plating de-embrittlement bake to prevent hydrogen embrittlement.
SCr440 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 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.85 | 0.72 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Niresidual element limit | ≤ 0.25 | — |
| Curesidual element limit | ≤ 0.3 | — |
| Fe | balance | — |
SCr440-A — frequently asked
What is SCr440-A used for?
SCr440-A is typically used for shafts, bolts, gears and spindles. In short: 5140-equivalent Q&T steel; chromium-only alloying; cold-headable bolt steel.
What is the yield strength of SCr440-A?
SCr440-A has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SCr440-A easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machining is most economical in the annealed or normalised condition (≤229 HB); at around 30 HRC after quench and temper, coated carbide turning and milling still work, but above 40 HRC use grinding or CBN.
Can SCr440-A be welded?
With care — weldability is rated fair (45/100). The carbon equivalent is high, so welding is generally not recommended; where it is unavoidable, preheat 200–300 °C, use low-hydrogen consumables and temper at 550–600 °C after welding.
What surface finishes work on SCr440-A?
Not anodizable; black oxide, phosphating, zinc plating or hard chrome are usual, with a post-plating de-embrittlement bake to prevent hydrogen embrittlement.
Can SCr440-A be formed, bent or molded?
Spheroidise-annealed bar can be cold-headed into bolts; hot forge at about 1100–1200 °C and normalize after forging to remove coarse grain.
What is the maximum service temperature of SCr440-A?
SCr440-A 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 SCr440-QT and SCr440-Q?
QT is the default condition — specify the standard 830–880 °C oil quench plus 520–620 °C temper (269–331 HB) for shafts, gears and bolts that need combined strength and toughness at 860 MPa yield. Q: treat the as-quenched 55 HRC state as an intermediate step only — hard and brittle at 2% elongation, it must be tempered immediately to remove quenching stresses. Yield strength is 860 MPa in QT versus 1,550 MPa in Q.
Sources
- GB/T 3077 40Cr — SAC (2015)
- SAE J404 / ASTM A29 (5140) — SAE / ASTM (2020)
- ASM Handbook Vol.1 Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 Heat Treating — ASM International (1991)
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.