Steel SCM425
JIS SCM425
SCM425 is a JIS chromium-molybdenum carburizing steel used where deeper case depth and higher core strength than SCM420 are required.
Reference datasheet — SCM425 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 A condition
SCM425 tempers and conditions
SCM425 is supplied in 11 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold forging, cold heading or deep-drilled parts where maximum softness and formability are needed. | 360 | 570 | 26 | 167 HB | 7.7 % IACS |
ADefault Solution annealed | Standard stocked condition: softest and most machinable state before carburizing or quench-and-temper. | 400 | 620 | 22 | 179 HB | — |
Hot rolled | Cheapest mill condition for stock that will be fully heat treated after rough machining. | 460 | 720 | 19 | 15 HRC | 7.5 % IACS |
Normalized and tempered | Used on heavy sections where full oil quenching is impractical but stress-relieved medium strength is wanted. | 520 | 760 | 20 | 20 HRC | 7.5 % IACS |
Normalized | Uniform fine-grain starting structure for large forgings before carburizing, and for moderate-strength as-supplied parts. | 550 | 810 | 18 | 21 HRC | 7.5 % IACS |
Cold drawn | Close-tolerance bright bar for shafts and pins machined without further heat treatment. | 640 | 780 | 12 | 229 HB | — |
oil quenched, high tempered | Tough through-hardened condition for shafts and bolts machined after heat treatment. | 810 | 950 | 16 | 30 HRC | — |
Induction hardened | Alternative to carburizing for selective wear surfaces on Q&T cores (journals, cam tracks). | 890 | 1,050 | 12 | 55 HRC | 7 % IACS |
oil quenched, medium-high tempered | Common core condition for gear blanks and splined shafts needing higher core strength than SCM420. | 930 | 1,080 | 14 | 34 HRC | — |
Carburized, quenched & tempered | The intended service condition: deep hard case for gear teeth and pins with a strong tempered-martensite core. | 950 | 1,180 | 10 | 60 HRC | — |
oil quenched, low tempered | High-strength through-hardened option for small-section shafts and fasteners; ductility and toughness fall off. | 1,120 | 1,280 | 11 | 40 HRC | — |
What is SCM425?
SCM425 is a JIS chromium-molybdenum carburizing steel used where deeper case depth and higher core strength than SCM420 are required. In the soft supply condition it runs about 400 MPa yield, 620 MPa tensile, 22 % elongation at 179 HB, with a machinability score of 55 and formability 45, then carburizes and quenches to a hard case over a Cr-Mo core; direct quench-and-temper tempers from 28–32 HRC to 38–42 HRC and induction hardening are also on file. It has no corrosion resistance, cannot be anodized, and welding is restricted by hardenability — carburized surfaces must not be welded. SCM420 is the lower-cost alternative for lighter sections. SCM425 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). SCM425 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 206 GPa (29.9 Msi).
What is SCM425 used for?
- Heavy-duty carburized gears
- Transmission and drive shafts
- Differential pinions and ring gears
- Splined shafts
- Planetary carriers and pins
- King pins and heavy machinery gearing
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
SCM425 properties
Typical room-temperature values for SCM425-A; bars are the position among steel grades.
Physical3
SCM425 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).
Mechanical15
SCM425 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SCM425 is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical2
SCM425 has an electrical resistivity of 2.3×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCM425 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
SCM425's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability fair (45/100).
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. SCM425 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SCM425
Is SCM425 easy to machine?
Rough machine in the annealed or spheroidized condition (~180 HB) with carbide inserts and flood coolant; leave 0.2–0.4 mm grinding stock for post-carburizing distortion.
Can SCM425 be welded?
Weldable only with care — preheat 200–300 °C, low-hydrogen or matching Cr-Mo filler, and temper/stress relieve at 600–650 °C; do not weld carburized surfaces.
Can SCM425 be formed, bent or molded?
Hot forge 1150–950 °C then normalize or spheroidize anneal; cold heading is practical only in the spheroidized condition.
SCM425 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 | 0.23 – 0.28 | 0.25 |
| 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 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual max | ≤ 0.25 | |
| Curesidual max | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SCM425?
Not anodizable — protect with black oxide, manganese phosphate, zinc or hard chrome; ground and superfinished tooth flanks after carburizing improve fatigue life.
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 SCM425 cost?
SCM425 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.
SCM425 — frequently asked
What is SCM425 used for?
SCM425 is typically used for heavy-duty carburized gears, transmission and drive shafts, differential pinions and ring gears, splined shafts, planetary carriers and pins and king pins and heavy machinery gearing. In short: deeper case than SCM420; cr-Mo carburizing gear steel; high core strength.
What is the yield strength of SCM425?
SCM425 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SCM425 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Rough machine in the annealed or spheroidized condition (~180 HB) with carbide inserts and flood coolant; leave 0.2–0.4 mm grinding stock for post-carburizing distortion.
Can SCM425 be welded?
With care — weldability is rated fair (40/100). Weldable only with care — preheat 200–300 °C, low-hydrogen or matching Cr-Mo filler, and temper/stress relieve at 600–650 °C; do not weld carburized surfaces.
What surface finishes work on SCM425?
Not anodizable — protect with black oxide, manganese phosphate, zinc or hard chrome; ground and superfinished tooth flanks after carburizing improve fatigue life.
Can SCM425 be formed, bent or molded?
Hot forge 1150–950 °C then normalize or spheroidize anneal; cold heading is practical only in the spheroidized condition.
What is the maximum service temperature of SCM425?
SCM425 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 SCM425-A and SCM425 CARB?
A is the default condition — standard stocked condition: softest and most machinable state before carburizing or quench-and-temper. CARB: the intended service condition: deep hard case for gear teeth and pins with a strong tempered-martensite core. Yield strength is 400 MPa in A versus 950 MPa in CARB.
How much does SCM425 cost?
SCM425 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 structural steels for machine structural use — JISC (2016)
- JIS G 4052 — Structural steels with specified hardenability bands — JISC (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 and Processes (carburizing) — ASM International (2013)
- Machinery's Handbook, 31st ed. — machinability ratings — Industrial Press (2020)
- GB/T 3077 — Alloy structural steels (25CrMo equivalent) — SAC (2015)
- (SMM / Mysteel / 1688 ) — SMM · Mysteel (2025)
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.