EN19 steel
Also called: 709M40, 42CrMo4, AISI 4140, 40Cr4Mo2, SCM440, EN19 material
EN19 is a chromium-molybdenum alloy steel (709M40), close to 42CrMo4 and AISI 4140. It is usually supplied hardened and tempered, and is used for high-strength shafts, gears, axles and bolts that are too heavily loaded for EN8.
Quick facts
- Type
- Low-alloy chromium-molybdenum steel
- Main alloys
- About 1% chromium and 0.25–0.35% molybdenum
- Usually supplied
- Hardened and tempered (condition T or U is common)
- Tensile strength
- About 850–1000 MPa in condition T
- Typical hardness
- About 250–300 HB in condition T
- Weldability
- Poor: needs preheating and post-weld heat treatment
Equivalent grades
| Standard | Closest grade |
|---|---|
| BS 970 (old / current) | EN19 / 709M40 |
| IS 1570 (India) | 40Cr4Mo2 |
| DIN / EN 10083 | 42CrMo4 (1.7225) |
| AISI / SAE | 4140 |
| JIS | SCM440 |
Close equivalents, not identical. In India EN19 and 42CrMo4 are used interchangeably for most parts.
Typical chemical composition (709M40)
| Element | % |
|---|---|
| Carbon (C) | 0.36–0.44 |
| Silicon (Si) | 0.10–0.35 |
| Manganese (Mn) | 0.70–1.00 |
| Chromium (Cr) | 0.90–1.20 |
| Molybdenum (Mo) | 0.25–0.35 |
Strength by hardened-and-tempered condition
| Condition | Tensile strength | Typical hardness |
|---|---|---|
| R | About 700–850 MPa | About 200–255 HB |
| S | About 775–925 MPa | About 225–275 HB |
| T | About 850–1000 MPa | About 250–300 HB |
| U | About 925–1075 MPa | About 270–320 HB |
| V | About 1000–1150 MPa | About 290–340 HB |
Condition letters come from BS 970. Larger bars cannot reach the higher conditions all the way through; ask the supplier what the bar size allows.
Heat treatment
- Hardening: about 830–860 °C, quench in oil
- Tempering: about 550–700 °C, depending on the strength wanted
- Induction hardening of the surface, around 50–55 HRC, for wear
- Nitriding works well for a hard, wear-resistant surface with little distortion
Machining and welding
In the hardened-and-tempered condition (around 250–300 HB) EN19 machines well with carbide tools; harder conditions are slower to cut.
Welding needs care: preheat (often about 200–300 °C), low-hydrogen consumables and usually a stress relief afterwards. For welded structures, choose a weldable steel instead.
Typical uses
- High-strength shafts, spindles and axles
- Gears and pinions
- High-tensile bolts and studs
- Crankshafts, connecting rods and couplings
- Hydraulic and oil-tool parts
Need parts made in EN19 steel?
Post your requirement free. Workshops that take your kind of work see it and get in touch. You only talk to the ones that fit.
Get startedRelated
Related job work
Questions
- Is EN19 the same as 42CrMo4 and 4140?
- They are close equivalents with about 1% chromium and 0.25% molybdenum, and are used interchangeably for most parts. If the exact grade matters, name the standard on the drawing.
- What is the hardness of EN19?
- It depends on the condition. In the commonly supplied condition T it is about 250–300 HB; induction hardening can give a surface of around 50–55 HRC.
- EN19 or EN24: which is stronger?
- EN24 contains nickel and hardens more deeply, so it keeps its strength in larger sections and is tougher. For small and medium sections, EN19 is usually enough and costs less.
- Can EN19 be welded?
- Yes, but with preheating, low-hydrogen consumables and usually stress relieving afterwards, otherwise it can crack.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.