SCM440 Alloy & Carbon Round Bar
JIS SCM440 · AISI 4140 · DIN 42CrMo4 (1.7225)
SCM440 is a chromium-molybdenum alloy engineering steel classified under JIS G4053, directly equivalent to the globally ubiquitous AISI 4140 and DIN 42CrMo4. It is one of the most widely specified alloy steels in industrial manufacturing, valued for its well-understood and reliable combination of high strength, good toughness, excellent fatigue resistance, and good machinability in the annealed condition.
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Material Properties
SCM440 has excellent hardenability — sections up to approximately 100 mm diameter can be through-hardened to the core via oil quenching. In the annealed condition (≤229 HB), machinability is good with HSS or carbide tooling. The Q&T condition develops tensile strength of 900–1 100 MPa with Charpy impact toughness of 60–100 J at room temperature. The steel responds well to surface hardening (induction hardening or nitriding) to achieve hard, wear-resistant surfaces while maintaining a tough core.
The chromium content (0.90–1.20%) provides hardenability, corrosion resistance, and high-temperature strength, while the molybdenum addition (0.15–0.30%) enhances hardenability further and inhibits temper brittleness — an important consideration in components that undergo cyclic loading. In the quenched and tempered condition, SCM440 achieves tensile strengths of 900–1 100 MPa, making it suitable for a very wide range of load-bearing components in industrial machinery, automotive, and oil & gas applications.
PT. Precision Special Steel supplies SCM440 in round bar form in a range of diameters. Supplied in the rolled or annealed condition; customers requiring pre-hardened material in the Q&T condition should consider our 4140QT grade.
Chemical Composition (%)
| Element | Content (%) |
|---|---|
| C | 0.38 – 0.43 |
| Si | 0.15 – 0.35 |
| Mn | 0.60 – 0.90 |
| Cr | 0.90 – 1.20 |
| Mo | 0.15 – 0.30 |
| P | ≤ 0.030 |
| S | ≤ 0.030 |
Mechanical Properties
| Property | Value |
|---|---|
| Hardness (Annealed) | ≤ 229 HB |
| Hardness (Q&T) | 28 – 34 HRC (280 – 330 HB) |
| Tensile Strength (Q&T) | 930 – 1 080 MPa |
| Yield Strength (Q&T) | 780 – 935 MPa |
| Elongation (Q&T) | ≥ 12% |
| Impact Toughness (KU2) | ≥ 63 J |
Heat Treatment
Annealing
Heat to 830–870°C, hold 3–5 hours, furnace cool to below 500°C, then air cool. Target: ≤229 HB.
Normalising
Heat to 870–920°C, hold 1 hr per 25 mm section, air cool. Improves microstructure prior to hardening.
Hardening
Austenitise at 830–860°C (typically 845°C), soak 20–40 min, oil quench. Water quench for sections < 30 mm only.
Tempering
Temper at 540–680°C (for 28–34 HRC range). Higher temperature = lower hardness but better toughness. Hold 1–2 hrs per 25 mm section.
Induction Hardening
Core in Q&T condition, surface induction harden to 50–55 HRC, temper immediately at 180–200°C.
Typical Applications
Sourced from Daye Special Steel (CITIC Group)
This grade is sourced from Daye Special Steel (大冶特殊钢), a member of CITIC Pacific Special Steel Group — China's largest special steel producer by volume. Daye is CITIC's flagship mill for engineering alloy steel, supplying Cr-Mo and medium-carbon grades to global manufacturers. All material is supplied with original Daye mill test certificates and full material traceability.
Frequently Asked Questions
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Alloy & Carbon Round Bar
Related Grades
Other grades in the same product family that may suit your application.
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4140QT
Alloy & Carbon Round Bar
AISI 4140 chromium-molybdenum steel supplied in the quenched and tempered condition (28–34 HRC) — ready for machining into high-strength components without further heat treatment.
View Details →product-4340qt-alloy-bar.jpg
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4340QT
Alloy & Carbon Round Bar
Nickel-chromium-molybdenum alloy steel supplied in the Q&T condition — offering the highest strength and toughness combination among our alloy bar grades, ideal for heavy-duty shafts and critical structural components.
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S45C
★Alloy & Carbon Round Bar
Standard medium-carbon steel round bar for general machinery components. Widely available, readily machinable, and heat-treatable — the workhorse of industrial manufacturing.
View Details →Need SCM440 in Indonesia?
Get a competitive quote within 1 business day. Material in stock at our Cikarang warehouse — available for same-day cutting and in-house CNC machining.