Grade EN19
Alloy engineering steel · 709M40, 4140, 42CrMo4
Chromium-molybdenum alloy steel for high-strength parts.
Data sheet
| Designations | AISI 4140 / SAE 4140 · UNS G41400 · EN 1.7225 (42CrMo4) |
|---|---|
| Standards | BS 970, EN 10083 |
| Used for | gears, crankshafts, high-tensile studs |
Offered in
Metallurgy
Reference data for AISI 4140 Chromium-Molybdenum High-Tensile Alloy Steel (Chromoly), against ASTM A29, ASTM A322, ASTM A193 Grade B7.
Elemental composition
42CrMo4 to 1.7225
- Chromium 0,95%0,80–1,10%
- Molybdenum 0,20%0,15–0,25%
- Carbon 0,41%0,38–0,43%
- Other additions 1,16%Mn, Si, P, S
- Iron 97,28%Balance
Proportions use the normalised midpoint of each specified range. The midpoint is a derived figure, not something the standard states: read the table for what is actually specified.
Performance profile
Comparative scores out of ten, for weighing one grade against another
These are relative ratings, not measured properties, and they carry no units. Use them to narrow a shortlist, then work from the specified values.
Composition as specified
| Element | Specified | Nominal |
|---|---|---|
| Iron Fe | Balance | 97,28% |
| Carbon C | 0,38–0,43% | 0,41% |
| Chromium Cr | 0,80–1,10% | 0,95% |
| Manganese Mn | 0,75–1,00% | 0,88% |
| Molybdenum Mo | 0,15–0,25% | 0,20% |
| Silicon Si | 0,15–0,35% | 0,25% |
| Phosphorus P | max 0,035%cap | 0,018% |
| Sulphur S | max 0,040%cap | 0,020% |
A cap is a ceiling, not a quantity: a heat may contain far less. The nominal column is the midpoint of each range, used for the chart's proportions only.
Mechanical and physical properties
| Property | Value |
|---|---|
| Tensile strength, ultimate | 655 MPa95 ksi |
| Yield strength, 0,2% offset | 415 MPa60,2 ksi |
| Elongation at break | 25% |
| Hardness | 197 HBW / 92 HRB |
| Modulus of elasticity | 205 GPa29,7 Mpsi |
| Density | 7,85 g/cm³0,28 lb/in³ |
| Thermal conductivity | 42,6 W/(m·K)295,4 BTU·in/(hr·ft²·°F) |
| Thermal expansion | 12,2 µm/(m·K)6,8 µin/(in·°F) |
Test condition not yet confirmed. These figures are typical values for the grade; the condition a bar was supplied in changes them materially, so ask us for the mill certificate before designing to a number.
Pitting resistance
Pitting resistance describes the passive chromium oxide film on a stainless steel. 4140 has no such film, so a PREN score does not apply to it. It relies on a coating, plating or galvanising for corrosion protection instead.
Corrosion and fabrication
Chloride and marine service
Low atmospheric corrosion resistance; Cr addition is for hardenability, not passivation; requires protective oiling, painting, or phosphating.
Acidic and chemical media
Susceptible to sour gas (H2S) sulfide stress cracking unless tempered to low hardness levels (e.g., NACE MR0175 <= 22 HRC).
Sensitisation and thermal behaviour
Not applicable; subject to temper embrittlement if slow-cooled through 450°C–550°C.
Welding
Moderate; medium carbon and alloy content creates high risk of martensitic cracking; requires preheat to 250°C–350°C and immediate post-weld stress relief.
Machining and cold forming
Machinability index 65% relative to AISI 1212. Moderate in annealed state; hot forged or machined in pre-hardened condition (28–32 HRC).
Where it is used
- Oilfield drill collars, tool joints, and ASTM A193 B7 stud bolts
- Automotive crankshafts, steering knuckles, and heavy axle shafts
- High-pressure hydraulic cylinder rods and pump shafts
- Industrial gearboxes, mill pinions, and forging press rams
Oil & Gas · Automotive & Heavy Truck · Industrial Machinery · Power Transmission
Performance scores in full
The same six scores the profile plots, as numbers.
| Property | 4140 |
|---|---|
| Corrosion resistance | 2.8 / 10 |
| Weldability | 5.5 / 10 |
| High-temperature resistance | 5.5 / 10 |
| Tensile strength | 9.2 / 10 |
| Cold formability | 6 / 10 |
| Machinability | 6.5 / 10 |
This page is guidance for selecting a grade, not a specification. Design to the governing standard and the mill certificate for the heat you are supplied.
The specifications and data on this site are provided for general information only. Verify any real-world project with a qualified metallurgist before relying on these figures. We take no responsibility for the use and application of this information.