Steel SCM425-IH (Induction hardened)
Heat-treated state
JIS SCM425
Alternative to carburizing for selective wear surfaces on Q&T cores (journals, cam tracks).
Values for the IH condition
Other SCM425 tempers and conditions
SCM425 is listed in 11 conditions; see the grade overview at SCM425.
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 | — |
IHThis page 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-IH?
SCM425-IH is SCM425 heat treated to IH — alternative to carburizing for selective wear surfaces on Q&T cores (journals, cam tracks). SCM425-IH has a yield strength of 890 MPa (129 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 90% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi). SCM425-IH 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). A is the default condition FabDigit quotes; IH is available on request or by drawing note.
Advantages
- High strength — 890 MPa (129 ksi), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
SCM425-IH properties
Typical room-temperature values for SCM425-IH; 22 are specific to this condition. Other listed values are SCM425 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCM425-IH 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-IH has a yield strength of 890 MPa (129 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 90% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SCM425-IH is rated for continuous service to 200°C (392 °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-IH has an electrical resistivity of 2.4×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCM425-IH 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-IH's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (5/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCM425-IH
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.
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.
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 | — |
SCM425-IH — frequently asked
What is SCM425-IH used for?
SCM425-IH 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-IH?
SCM425-IH has a typical yield strength of 890 MPa (129 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SCM425-IH easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% 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-IH be welded?
Not readily — weldability is rated not recommended (5/100). 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-IH?
Not anodizable — protect with black oxide, manganese phosphate, zinc or hard chrome; ground and superfinished tooth flanks after carburizing improve fatigue life.
Can SCM425-IH 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-IH?
SCM425-IH is rated for continuous use to about 200°C (392 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.