Chromium-molybdenum engineering steel supplied annealed or quenched-and-tempered — composition, Q&T hardness, machining data and supply forms for 4140, the world’s most used alloy steel grade.
Alloy Steel Grades We Supply
Every grade below is stocked or produced on mill lots with an EN 10204 3.1 certificate. Click any grade for its full chemical composition, mechanical properties, heat-treatment windows and equivalent standards.
| Grade | Standard / UNS | Typical Hardness | Key Character | Details |
|---|---|---|---|---|
| 4140 Alloy Steel | AISI 4140 / EN 42CrMo4 (1.7225) | 28 – 34 HRC Q&T | Cr-Mo engineering steel; strong, tough, easy to harden in oil | View grade → |
Grade Overview
The universal alloy steel for shafts, gears, axles, bolts and tool holders — reliable strength after quench-and-temper at a moderate cost.
What Is Alloy Steel?
Alloy steels add chromium, molybdenum, nickel or vanadium to carbon steel to raise hardenability, strength and toughness at moderate cost. 4140 (EN 42CrMo4, JIS SCM440, GB 42CrMo) is the global default — the grade engineers reach first for shafts, gears, bolts and holders.
It machines well annealed, oil-hardens through moderate sections, and tempers into a wide usable window: 28–34 HRC for general engineering, up to 39 HRC where higher strength is needed. It is not stainless and needs corrosion protection in service.
We supply 4140 as round bar 10–300 mm, flat bar and plate 6–200 mm, forging stock and hex/square bar, in annealed, normalised or quenched-and-tempered condition with full mill certification.
How to Choose the Right Grade
4140 is the right call when a part must be strong and tough, machined in volume, and hardened in oil — think rotating shafts, gear blanks, high-tension bolts and tool holders. Step up to 4340 when the section is heavy or the part is fatigue-critical and needs nickel-added toughness. Drop to 1045 when the load is light and cost dominates. If you are unsure, send the drawing — we will confirm the grade, supply condition and tolerance before quoting.
Quality Control and Mill Certificates
Every shipment ships with an EN 10204 3.1 mill certificate covering heat chemical analysis, hardness and the mechanical test on record. On request we add: ultrasonic test on heavy bar and plate, magnetic particle inspection on machined surfaces, and third-party inspection (SGS / BV) before loading. Dimensional tolerances follow the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
What is 4140 steel equivalent to?
EN 42CrMo4 (1.7225) in Europe, JIS SCM440 in Japan and GB 42CrMo in China are the same chromium-molybdenum steel; confirm against the mill certificate for critical parts.
What hardness does 4140 reach?
Typically 28–34 HRC quenched and tempered near 600 °C; lower tempering temperatures push strength up to about 39 HRC where needed.
Is 4140 suitable for gears?
Yes — it is one of the most common gear steels. Harden and temper to your tooth-hardness requirement, then induction- or flame-harden the tooth surfaces where wear demands it.
Related Pages
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