Steel SCM432 QT 40-45 HRC
Hardness band
JIS SCM432 · AISI/SAE 4137
Maximum practical through-hardness for small sections needing wear and high yield strength.
Values for the QT 40-45 HRC condition
Other SCM432 tempers and conditions
SCM432 is listed in 9 conditions; see the grade overview at SCM432.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed bar | Softest condition for deep machining, cold forming or before final heat treatment. | 400 | 620 | 24 | 187 HB | — |
Hot rolled | Cheapest mill condition, bought as feedstock for forging and subsequent heat treatment. | 430 | 700 | 20 | 14 HRC | 8.2 % IACS |
Normalized | Uniform fine-grain structure for forgings before machining or as a moderate-strength delivery condition. | 470 | 740 | 20 | 17 HRC | 8.2 % IACS |
Cold drawn | Close-tolerance bright bar for shafts machined without further heat treatment. | 650 | 780 | 12 | 20 HRC | 8 % IACS |
high-temper condition | Toughness-biased condition for large shafts and parts that still need post-HT machining. | 820 | 960 | 18 | 30 HRC | — |
QTDefault Quenched and tempered | Standard supply condition meeting JIS 930 MPa UTS / 785 MPa YS for shafts, bolts and gear blanks. | 850 | 1,000 | 17 | 31 HRC | — |
Q&T + gas/plasma nitrided case | Q&T core with 0.2–0.4 mm nitrided case for wear and fatigue on shafts and spindles. | 850 | 1,000 | 15 | 55 HRC | 7.8 % IACS |
medium-temper condition | Higher strength for loaded bolts, couplings and gear blanks with acceptable toughness. | 1,020 | 1,150 | 14 | 35 HRC | — |
QT 40-45 HRCThis page low-temper (high strength) condition | Maximum practical through-hardness for small sections needing wear and high yield strength. | 1,250 | 1,400 | 11 | 42 HRC | — |
What is SCM432 QT 40-45 HRC?
SCM432 QT 40-45 HRC is SCM432 heat treated to QT 40-45 HRC — maximum practical through-hardness for small sections needing wear and high yield strength. SCM432 QT 40-45 HRC has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi). SCM432 QT 40-45 HRC 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; QT 40-45 HRC is available on request or by drawing note.
Advantages
- High strength — 1,250 MPa (181 ksi), better than 95% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
SCM432 QT 40-45 HRC properties
Typical room-temperature values for SCM432 QT 40-45 HRC; 13 are specific to this condition. Other listed values are SCM432 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCM432 QT 40-45 HRC 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
SCM432 QT 40-45 HRC has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCM432 QT 40-45 HRC 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).
Electrical3
SCM432 QT 40-45 HRC conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCM432 QT 40-45 HRC takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
SCM432 QT 40-45 HRC's machinability is poor (32/100, worse than 87% of steel grades); weldability fair (45/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCM432 QT 40-45 HRC
Is SCM432 easy to machine?
Machine in the annealed/normalized state or at ≤32 HRC; use coated carbide, rigid setups and generous coolant — chips are stringy at low hardness.
Can SCM432 be welded?
Preheat 200–300 °C, use low-hydrogen consumables, control interpass heat and post-weld temper/stress-relieve at 600–650 °C to avoid HAZ cracking.
Can SCM432 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold bending or heading only in the spheroidize-annealed condition with generous bend radii.
What surface finishes work on SCM432?
No anodizing — protect with zinc/manganese phosphate, black oxide, Zn-Ni or hard chrome; nitriding or induction hardening adds surface wear resistance.
SCM432 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 |
|---|---|---|
| CJIS G4053 SCM432 | 0.27 – 0.37 | 0.33 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 1 – 1.5 | 1.2 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual, max | ≤ 0.25 | — |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SCM432 QT 40-45 HRC — frequently asked
What is SCM432 QT 40-45 HRC used for?
SCM432 QT 40-45 HRC is typically used for shafts, high-strength bolts and structural forgings. In short: between SCM430 and SCM435; balanced strength and toughness; nitridable Cr-Mo shaft steel.
What is the yield strength of SCM432 QT 40-45 HRC?
SCM432 QT 40-45 HRC has a typical yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is SCM432 QT 40-45 HRC easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Machine in the annealed/normalized state or at ≤32 HRC; use coated carbide, rigid setups and generous coolant — chips are stringy at low hardness.
Can SCM432 QT 40-45 HRC be welded?
With care — weldability is rated fair (45/100). Preheat 200–300 °C, use low-hydrogen consumables, control interpass heat and post-weld temper/stress-relieve at 600–650 °C to avoid HAZ cracking.
What surface finishes work on SCM432 QT 40-45 HRC?
No anodizing — protect with zinc/manganese phosphate, black oxide, Zn-Ni or hard chrome; nitriding or induction hardening adds surface wear resistance.
Can SCM432 QT 40-45 HRC be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold bending or heading only in the spheroidize-annealed condition with generous bend radii.
What is the maximum service temperature of SCM432 QT 40-45 HRC?
SCM432 QT 40-45 HRC 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 SCM432-QT and SCM432-HR?
QT is the default condition — standard supply condition meeting JIS 930 MPa UTS / 785 MPa YS for shafts, bolts and gear blanks. HR: cheapest mill condition, bought as feedstock for forging and subsequent heat treatment. Yield strength is 850 MPa in QT versus 430 MPa in HR.
Sources
- JIS G 4053 Low-alloyed steels for machine structural use — JSA (2016)
- GB/T 3077 (equivalent Cr-Mo grades) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
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.