4130 vs 4140 Steel: Which Chromoly Alloy Should You Choose?

📋 4130 / 25CrMo4 Datasheet → · 4140 / 42CrMo4 Datasheet → — chemical composition, section-dependent mechanical properties and international equivalent tables.

What Are 4130 and 4140?

Both are chrome-molybdenum (Cr-Mo) alloy steels with almost identical chromium (~1%) and molybdenum (~0.2%) content. The single defining difference is carbon content — and that one difference completely changes each steel's character:

• 4130 (EN equivalent 25CrMo4, W.Nr. 1.7218): low-to-medium carbon (~0.30% C)
• 4140 (EN equivalent 42CrMo4, W.Nr. 1.7225): medium carbon (~0.40% C)

In short: 4130 is tougher and more weldable, 4140 is stronger and more hardenable.

Chemical Composition Comparison

Element	4130 (%)	4140 (%)
Carbon (C)	0.28–0.33	0.38–0.43
Silicon (Si)	0.15–0.35	0.15–0.35
Manganese (Mn)	0.40–0.60	0.75–1.00
Chromium (Cr)	0.80–1.10	0.80–1.10
Molybdenum (Mo)	0.15–0.25	0.15–0.25

To compare chemistry across grades, use our Chemical Composition tool.

Mechanical Properties

Property	4130 (Q&T, thin section)	4140 (Q&T)
Tensile strength (Rm)	810–980 MPa	900–1100 MPa
Yield strength (Re)	min. 690 MPa	min. 650 MPa
Hardness	240–300 HB	260–320 HB
Ductility / toughness	Higher	Moderate
Weldability	Good	Limited (preheat required)

The Defining Difference: Carbon → Hardenability and Welding

As carbon rises, hardness and hardenability increase while ductility and weldability fall:

• 4130, thanks to its lower carbon, usually needs no preheat for welding (a light preheat suffices on heavier sections) and delivers excellent toughness in thin-walled parts. However, its hardenability is limited — the core will not fully harden in thick sections.
• 4140, thanks to its higher carbon, hardens through even in larger sections and offers higher strength. In return, welding requires 200–300°C preheat and post-weld stress relieving.

To convert hardness between HRC/HB/Rm, use our Hardness Converter.

When to Choose Which?

Choose 4130 if:

• The part requires welded fabrication (tubing, pressure vessels, frames, hydraulic lines)
• It is thin-walled / thin-section and high toughness is needed (aerospace, drawn tube, bike/motorcycle frames)
• Crack tolerance under cyclic loading matters

Choose 4140 if:

• High strength and hardness are the primary goal (shafts, axles, gears, high-strength bolts)
• The part is thick-section (this is where the hardenability advantage shows)
• Wear resistance and surface hardening (nitriding/induction) are required

Application Areas

Sector	4130	4140
Aerospace	Engine mounts, hydraulic tube	Landing-gear components
Oil & gas	Thin-wall tubing, pressure parts	Valve bodies, shafts, fittings
Machinery	Welded structures, frames	Gears, shafts, axles, dies
Automotive	Chassis, tubing	Crankshafts, suspension parts

For a detailed side-by-side technical comparison, see our 42CrMo4 vs 4140 comparison page, and for all cross-standard equivalents use the Steel Grade Equivalent tool.

Supply from Aktif Çelik

At Aktif Çelik we stock both 4130/25CrMo4 and 4140/42CrMo4 in hot-rolled bar, bright (cold drawn) bar and forged bar forms across a wide diameter range. With 3.1 certified, normalized or quenched-and-tempered options we recommend the most suitable grade for your project. Contact our team for technical consultancy and cut-to-length service.