Steel SCM422 Q&T 38-42 HRC
Hardness band
JIS SCM422
Q&T 38-42 HRC = quenched & low-tempered
Higher-strength direct-hardened option for medium sections where toughness can be traded for strength.
Values for the Q&T 38-42 HRC condition
Other SCM422 tempers and conditions
SCM422 is listed in 8 conditions; see the grade overview at SCM422.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
for cold forming / heading | Choose when the part is cold-headed, cold-extruded or deep-machined before carburizing. | 340 | 540 | 28 | 155 HB | 8 % IACS |
AnnealedDefault full/soft anneal, as-supplied bar | Standard stock condition for carburizing-grade bar: softest and most machinable state before case hardening. | 370 | 580 | 25 | 170 HB | — |
as-rolled black bar | Cheapest raw form; use when the part is fully machined and heat treated afterwards. | 420 | 660 | 20 | 195 HB | 8 % IACS |
880–920 °C air cool | Used to refine grain and homogenize forgings before carburizing or machining. | 470 | 720 | 20 | 210 HB | 8 % IACS |
bright bar, annealed then drawn | Pick for close-tolerance bright bar going straight onto a lathe or screw machine. | 600 | 730 | 12 | 215 HB | 8 % IACS |
Quenched & tempered | Direct-hardened (non-carburized) use for shafts and fasteners needing uniform medium strength and good toughness. | 830 | 1,000 | 15 | 31 HRC | — |
case 58–62 HRC | The intended service condition: hard wear-resistant case over a tough, Mo-strengthened core for gears and splined shafts. | 1,000 | 1,200 | 13 | 60 HRC | — |
Q&T 38-42 HRCThis page Quenched & low-tempered | Higher-strength direct-hardened option for medium sections where toughness can be traded for strength. | 1,080 | 1,250 | 12 | 40 HRC | — |
What is SCM422 Q&T 38-42 HRC?
SCM422 Q&T 38-42 HRC is SCM422 heat treated to Q&T 38-42 HRC — higher-strength direct-hardened option for medium sections where toughness can be traded for strength. SCM422 Q&T 38-42 HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi). SCM422 Q&T 38-42 HRC 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). Annealed is the default condition FabDigit quotes; Q&T 38-42 HRC is available on request or by drawing note.
Advantages
- High strength — 1,080 MPa (157 ksi), better than 93% of steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
SCM422 Q&T 38-42 HRC properties
Typical room-temperature values for SCM422 Q&T 38-42 HRC; 11 are specific to this condition. Other listed values are SCM422 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCM422 Q&T 38-42 HRC 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).
Mechanical13
SCM422 Q&T 38-42 HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SCM422 Q&T 38-42 HRC is rated for continuous service to 250°C (482 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
SCM422 Q&T 38-42 HRC conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SCM422 Q&T 38-42 HRC takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
SCM422 Q&T 38-42 HRC's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCM422 Q&T 38-42 HRC
Is SCM422 easy to machine?
Machine in the annealed or spheroidized state with coated carbide, ~120–180 m/min; leave grinding stock because carburizing causes 0.1–0.3 % growth and distortion.
Can SCM422 be welded?
Poor weldability (CE ≈ 0.7–0.8): preheat 250–350 °C, low-hydrogen filler, and temper/stress relieve immediately; never weld a carburized case.
Can SCM422 be formed, bent or molded?
Hot forge 1150–900 °C then normalize; cold heading only from spheroidize-annealed stock with generous radii.
What surface finishes work on SCM422?
No corrosion resistance bare — use black oxide, manganese phosphate, zinc plating (bake to avoid hydrogen embrittlement) or oil; case-hardened surfaces grind and polish to a fine finish.
SCM422 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 |
|---|---|---|
| Ccarburizing carbon level | 0.2 – 0.25 | 0.22 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Moraised vs SCM420/SCM421 for core hardenability | 0.35 – 0.45 | 0.4 |
| Niresidual max | ≤ 0.25 | — |
| Curesidual max | ≤ 0.3 | — |
| Febalance; confirm exact limits against the governing mill/JIS Cr-Mo specification for this designation | balance | — |
SCM422 Q&T 38-42 HRC — frequently asked
What is SCM422 Q&T 38-42 HRC used for?
SCM422 Q&T 38-42 HRC is typically used for carburized gears, shafts and pinions. In short: deeper-hardening carburizing Cr-Mo; hard case, strong core; medium-section gear steel.
What is the yield strength of SCM422 Q&T 38-42 HRC?
SCM422 Q&T 38-42 HRC has a typical yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SCM422 Q&T 38-42 HRC easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed or spheroidized state with coated carbide, ~120–180 m/min; leave grinding stock because carburizing causes 0.1–0.3 % growth and distortion.
Can SCM422 Q&T 38-42 HRC be welded?
With care — weldability is rated fair (40/100). Poor weldability (CE ≈ 0.7–0.8): preheat 250–350 °C, low-hydrogen filler, and temper/stress relieve immediately; never weld a carburized case.
What surface finishes work on SCM422 Q&T 38-42 HRC?
No corrosion resistance bare — use black oxide, manganese phosphate, zinc plating (bake to avoid hydrogen embrittlement) or oil; case-hardened surfaces grind and polish to a fine finish.
Can SCM422 Q&T 38-42 HRC be formed, bent or molded?
Hot forge 1150–900 °C then normalize; cold heading only from spheroidize-annealed stock with generous radii.
What is the maximum service temperature of SCM422 Q&T 38-42 HRC?
SCM422 Q&T 38-42 HRC is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- JIS G 4053 Low-alloyed steels for machine structural use (Cr-Mo SCM series) — JSA (2016)
- JIS G 4051 / G 0557 carburized case-depth and hardness test practice — JSA (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A: Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
- ASM Machining Data Handbook (4100-series machinability) — ASM International (1980)
- GB/T 3077 (equivalent 20CrMo/22CrMo class) — SAC (2015)
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.