Steel SCM422
JIS SCM422
SCM422 is a carburizing chromium-molybdenum case-hardening steel in the JIS SCM family, with molybdenum raised relative to SCM420 for better core hardenability in medium sections.
Reference datasheet — SCM422 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 Annealed condition
SCM422 tempers and conditions
SCM422 is supplied in 8 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
SCM422 is a carburizing chromium-molybdenum case-hardening steel in the JIS SCM family, with molybdenum raised relative to SCM420 for better core hardenability in medium sections. It is used where a hard wear surface must sit on a strong, tough core, and is supplied as bar, tube and forging stock in annealed, spheroidized, hot-rolled, normalized, cold-drawn, Q&T (28-34 and 38-42 HRC) and carburized conditions. The default annealed condition gives 370 MPa yield, 580 MPa tensile, 25 % elongation and 170 HB (87 HRB), with moderate machinability (55). Weldability is poor and the steel has no corrosion resistance bare; SCM420 is the nearer choice for thinner, less heavily loaded carburized parts. SCM422 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). SCM422 has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Elongation at break is 25% and the elastic modulus is 206 GPa (29.9 Msi).
What is SCM422 used for?
- carburized gears
- shafts
- pinions
Advantages
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
SCM422 properties
Typical room-temperature values for SCM422-Annealed; bars are the position among steel grades.
Physical3
SCM422 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 has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Elongation at break is 25% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SCM422 is rated for continuous service to 350°C (662 °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 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 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's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability good (55/100).
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. SCM422 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SCM422
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.
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 |
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.
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
How much does SCM422 cost?
SCM422 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SCM422 — frequently asked
What is SCM422 used for?
SCM422 is typically used for carburized gears, shafts and pinions. In short: deeper-hardening carburizing Cr-Mo; hard case, strong core; medium-section gear steel.
What is the yield strength of SCM422?
SCM422 has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SCM422 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed or spheroidized state with coated carbide, ~120–180 m/min; leave grinding stock because carburizing causes 0.1–0.3 % growth and distortion.
Can SCM422 be welded?
With care — weldability is rated fair (40/100). Poor weldability (CE ≈ 0.7–0.8): preheat 250–350 °C, low-hydrogen filler, and temper/stress relieve immediately; never weld a carburized case.
What surface finishes work on SCM422?
No corrosion resistance bare — use black oxide, manganese phosphate, zinc plating (bake to avoid hydrogen embrittlement) or oil; case-hardened surfaces grind and polish to a fine finish.
Can SCM422 be formed, bent or molded?
Hot forge 1150–900 °C then normalize; cold heading only from spheroidize-annealed stock with generous radii.
What is the maximum service temperature of SCM422?
SCM422 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does SCM422 cost?
SCM422 is a budget-cost steel ($), 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
- 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; 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.