Advantages
Good hardenability, strength, toughness and fatigue behavior. Quenching and tempering allow different strength/hardness combinations; nitriding can improve the surface.
Plan strength, treatment and final dimensions together
For an alloy-steel component, bring Aria the grade, required treatment, hardness and critical dimensions as one brief. We help you discuss the manufacturing and inspection requirements against the finished condition. Property values from different treatment states should remain attached to those states when comparing options.
Material options
| Property | Details |
|---|---|
| Colors | Steel gray, Black oxide |
| Special properties | Quenched-and-tempered or nitrided conditions must be specified. The supplied overview gives approximately 28–55 HRC across different treatments, not one universal hardness. |
Detailed values describe 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered. Family ranges are broader selection references and may include different grades or reinforcement levels. Confirm the selected grade, condition and test method for your part. Melting temperature is not a working-temperature limit; use the mill certificate for the specified alloy and temper.
Material properties
| Property | Metric | Imperial | Test method / conditions |
|---|---|---|---|
| Density | 7.85 g/cm³ | 0.284 lb/in³ | Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Tensile Strength UTS | 690~1080 MPa | 100~160×10³ psi | ASTM A29 · Annealed to quenched and tempered · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Yield Strength | 590~990 MPa | 85~140×10³ psi | ASTM A29 · Annealed to quenched and tempered · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Elongation | 11~26 % | 11~26 % | ASTM A29 · Depends on temper / condition · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Brinell Hardness | 200~310 HB | 200~310 HB | Annealed to quenched and tempered · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Elastic Modulus | 190 GPa | 27×10⁶ psi | Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Shear Strength | 410~660 MPa | 60~96×10³ psi | Depends on temper / condition · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Fatigue Strength | 360~650 MPa | 53~94×10³ psi | Depends on temper / condition · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Thermal Conductivity | 43 W/m·K | 25 BTU/h·ft·°F | Room temperature · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| CTE | 13 µm/m·K | 7.2 µin/in·°F | Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Specific Heat | 470 J/kg·K | 0.11 BTU/lb·°F | Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
| Melting Range | 1420~1460 °C | 2580~2660 °F | Solidus–liquidus · Reference: 4140 / SCM440 chromium-molybdenum steel, annealed to quenched and tempered |
Material family ranges — selection reference
| Property | Family reference |
|---|---|
| Material class | Steel |
| Density (g/cm³) | 7.8–7.9 |
| Tensile strength (MPa) | 650–1300 |
| Elongation at break (%) | 8–25 |
| Elastic modulus (GPa) | 190–210 |
| Hardness | HB 200–400 |
| Temperature reference (°C) | Melting point 1420–1460 |
Product standards and grade references
| Standard or designation | Scope and selection notes |
|---|---|
| ASTM A29 / A29M | General requirements for hot-wrought carbon and alloy steel bars. |
| AMS 6349 | SAE 4140 steel bars in the normalized condition. This does not specify every 4140 heat-treatment condition. |
| Cr-Mo grade comparison | AISI 4140; JIS SCM440; EN 42CrMo4 / 1.7225; GB 42CrMo. Confirm composition limits, section size and heat treatment. |
| Before ordering | Grade names listed for comparison are not a blanket equivalence declaration. Agree the product standard, edition, delivery condition and required certificate before approving a substitution. |
Advantages and considerations
Material limitations
Poor inherent corrosion resistance and difficult cutting after hardening. Welding needs a suitable preheat/postheat procedure.
Applications
Typical applications
Loaded shafts, gears, spindles, high-strength bolts, connecting rods, tooling, hydraulic parts and automotive/oilfield components.
Design considerations
Processing options
Rough-machine annealed or normalized stock, apply the specified heat treatment, then finish-machine or grind. Hardened stock may need CBN tooling or grinding.
Finishing options
Quenching/tempering and nitriding; nickel/chrome plating, black oxide, phosphate, paint and zinc-flake corrosion protection.
Grade and finish combinations
Confirm heat-treatment hardness before quoting. Welding may need preheat in the supplied 170–350°C reference range and suitable postheat, depending on the procedure. Alternatives include 4340, carburizing grade 8620 and 4130.
Color and grade options
Natural steel gray. Black oxide, nickel/chrome plating, phosphate or paint.