Materials & grades
4140 / 42CrMo4 / EN19 / SCM440 chromium-molybdenum steel
AISI 4140 is a medium-carbon chromium-molybdenum alloy steel, normally used hardened and tempered for shafts, gears and high-strength bolts. Its usual equivalents are 42CrMo4 (1.7225) in Europe, 708M40 (formerly EN19) in the UK, 42Cr4Mo2 in India and SCM440 in Japan.
Names by standard
What it is called in each region
| Region | System | Designation | قياسي | Match |
|---|---|---|---|---|
| USA | AISI/SAE | 4140 | SAE J404; ASTM A29 (bar) | Same material |
| UNS | G41400 | — | Same material | |
| UK | BS 970-3 (1991) | 708M40BS 970 alloy grades are superseded by EN 10083-3 but are still widely ordered by name, often with a condition letter such as 708M40T. | BS 970-3 | Equivalent |
| BS 970 (1955 EN series) | EN19Superseded 1955 name. Still the most-searched UK name; EN19T and EN19U denote heat-treated tensile conditions. | — | Equivalent | |
| BS 970-3 (1991) | 709M40Sister grade to 708M40 with a different molybdenum range. Some charts give it as the modern name for EN19. | BS 970-3 | Closest equivalent | |
| EU | EN 10027-1 name | 42CrMo4Same name was used in the superseded DIN 17200. | EN 10083-3; EN ISO 683-2 | Equivalent |
| EN 10027-2 number | 1.7225 | EN 10083-3 | Equivalent | |
| EN 10027-1 name | 42CrMoS4 (1.7227)Resulphurised version with controlled sulphur 0.020–0.040% for better machinability. | EN 10083-3 | Closest equivalent | |
| الهند | IS 1570 | 42Cr4Mo2 | IS 1570 (Part 4):1988 | Equivalent |
| IS 11169 (Part 1) | 40Cr4Mo2Cold-heading and cold-extrusion steel standard. Its cross-reference annex marks 40Cr4Mo2 as identical to SAE 4140 (and lists SCM440). IS 1570 (Part 4) uses the same name, 40Cr4Mo2, for different limits that resemble 42CrMo4. The annex of IS 11169 labels its 42CrMo4 row "40Cr4Mo3". | IS 11169 (Part 1):2022 | Equivalent | |
| IS (pre-1974 designation) | 40Cr1Mo28Older Indian letter-symbol name still seen on charts. Superseded by the IS 1762 designation system used in IS 1570 (Part 4):1988. | IS 4368:1967 | Closest equivalent | |
| Japan | JIS G 4053 | SCM440SCM440H is the hardenability-band version. | JIS G 4053 | Equivalent |
On equivalence
- 4140, 42CrMo4, 708M40, 42Cr4Mo2 and SCM440 overlap closely but are not identical. 42CrMo4 allows up to 0.45% carbon and 0.90–1.20% chromium; 4140 caps carbon at 0.43%, specifies 0.80–1.10% chromium and requires more manganese (0.75–1.00%).
- EN19 is the 1955 BS 970 name. Most references map it to 708M40; some map it to 709M40, which differs in molybdenum. 708M40 is the usual modern equivalent.
- India: IS 1570 (Part 4):1988 lists 42Cr4Mo2 in its composition table, while its mechanical-property table prints the grade as 40Cr4Mo2. Indian charts also quote 40Cr4Mo3 or the pre-1974 name 40Cr1Mo28. 40Cr4Mo3 does not appear in the 1988 schedule, so check which designation a drawing means.
- India: IS 11169 (Part 1):2022 (cold-heading steel) lists 40Cr4Mo2 with SAE 4140 limits (Table C.2) and marks it identical to SAE 4140. That makes it the nearest Indian grade to 4140 by composition. The name is shared with the IS 1570 (Part 4) mechanical-property table, where 40Cr4Mo2 carries the 42CrMo4-like limits, and the IS 11169 annex prints its 42CrMo4 row as "40Cr4Mo3". Check which standard a drawing means.
- IS 1570 (Part 4) does not set phosphorus or sulphur limits; these come from the product specification.
- Japan: SCM440 (JIS G 4053) is the standard Japanese counterpart. Its full limits are not reproduced here; check JIS G 4053 for manganese and residual limits before substituting.
- Silicon: some US datasheets show 0.15–0.30% Si for 4140, while SAE bar tables give 0.15–0.35%.
- Compare equivalents at the same condition and ruling section. EN 10083-3 minimum yield for 42CrMo4 falls from 900 MPa (diameter ≤16 mm) to 500 MPa (160–250 mm).
Chemical composition
Composition limits, mass %
| Element | 4140USA · SAE J404 / ASTM A29 (bar) | 708M40UK · BS 970-3 | 42CrMo4 (1.7225)EU · EN 10083-3 (heat analysis) | 42Cr4Mo2الهند · IS 1570 (Part 4):1988 | 40Cr4Mo2الهند · IS 11169 (Part 1):2022 (ladle analysis) |
|---|---|---|---|---|---|
| C | 0.38–0.43 | 0.36–0.44 | 0.38–0.45 | 0.38–0.45 | 0.38–0.43 |
| Si | 0.15–0.35 | 0.10–0.35 | ≤0.40 | 0.10–0.35 | 0.15–0.35 |
| Mn | 0.75–1.00 | 0.70–1.00 | 0.60–0.90 | 0.60–0.90 | 0.75–1.00 |
| P | ≤0.035 | ≤0.035 | ≤0.025 | — | ≤0.030 |
| S | ≤0.040 | ≤0.040 | ≤0.035 | — | ≤0.040 |
| Cr | 0.80–1.10 | 0.90–1.20 | 0.90–1.20 | 0.90–1.20 | 0.80–1.10 |
| Ni | — | — | — | — | ≤0.25 |
| Mo | 0.15–0.25 | 0.15–0.25 | 0.15–0.30 | 0.15–0.30 | 0.15–0.25 |
| Cu | — | — | — | — | ≤0.35 |
Mechanical properties
Strength and hardness
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| AnnealedTypical values, not specified minimumsAZoM, AISI 4140 alloy steel (UNS G41400) | 655 MPa95.0 ksi | 415 MPa60.2 ksi | 25.7 % | 197 HB |
| Quenched and tempered (+QT)Specified, diameter 16–40 mm (thickness 8–20 mm); yield and elongation are minimumsEN 10083-3, 42CrMo4, via thyssenkrupp Materials Services datasheet | 1000–1200 MPa145–174 ksi | ≥750 MPa≥109 ksi | ≥11 % | — |
| Quenched and tempered (+QT)Specified, diameter 40–100 mm (thickness 20–60 mm); yield and elongation are minimumsEN 10083-3, 42CrMo4, via thyssenkrupp Materials Services datasheet | 900–1100 MPa131–160 ksi | ≥650 MPa≥94 ksi | ≥12 % | — |
| Quenched and tempered (+QT)Specified, diameter 100–160 mm (thickness 60–100 mm); yield and elongation are minimumsEN 10083-3, 42CrMo4, via thyssenkrupp Materials Services datasheet | 800–950 MPa116–138 ksi | ≥550 MPa≥80 ksi | ≥13 % | — |
| Hardened and tempered, condition TBS 970 condition T; values depend on ruling sectionWest Yorkshire Steel, 708M40 (EN19) datasheet | 850–1000 MPa123–145 ksi | ≥650 MPa≥94 ksi | ≥13 % | 248–302 HB |
| Oil hardened and temperedSpecified, limiting ruling section 63 mm; hardness for guidance onlyIS 1570 (Part 4):1988, Table 4 | 900–1050 MPa131–152 ksi | ≥650 MPa≥94 ksi | ≥11 % | 255–311 HB |
| Soft annealed (+A)Specified maximum hardnessEN 10083-3, 42CrMo4, via thyssenkrupp Materials Services datasheet | — | — | — | ≤241 HB |
In practice
Behaviour, heat treatment and uses
Characteristics
- Hardenability is good. Chromium and molybdenum let 4140 harden through in oil in moderate sections, but specified strength falls as the section grows.
- Strength and toughness are well balanced in the quenched and tempered condition, with good wear resistance.
- Machinability is rated about 65% of AISI 1212 in the annealed condition (typical rating).
- Weldability is difficult. At 0.38–0.45% carbon the weld and heat-affected zone harden, so preheat, controlled interpass temperature, slow cooling and usually post-weld heat treatment are needed. Filler metals are lower-carbon Mo or CrMo types.
- Tempering in the range of about 250–375 °C reduces impact toughness and is normally avoided.
- Corrosion resistance is that of ordinary low-alloy steel. Parts are oiled, plated, coated or nitrided when protection is needed.
- The steel is magnetic and hot-forms well. Cold formability depends on carbon content and microstructure.
Heat treatment
- Hardening: 820–880 °C, quench in oil or water (EN guidance for 42CrMo4). US practice is typically about 845 °C with an oil quench.
- Tempering: 540–680 °C for the EN 10083-3 quenched and tempered property ranges, held for at least about 60 minutes. Lower tempering temperatures, from about 205 °C, give higher strength and hardness.
- Normalizing: 840–880 °C, then air cool.
- Annealing: about 872 °C with slow furnace cooling (US practice). Soft-annealed 42CrMo4 is supplied at ≤241 HB; 708M40 is annealed at 680–700 °C.
- Surface hardening: responds to flame and induction hardening. IS 1570 (Part 4) cross-references 42Cr4Mo2 to the Indian specification for flame- and induction-hardening steels (IS 3930).
استخدامات نموذجية
- Shafts, axles, spindles and arbors
- Gears and pinions
- High-strength bolts and studs; ASTM A193 Grade B7 bolting is a 4140-type chromium-molybdenum steel
- Highly stressed forgings for machine building and vehicle construction
- Couplings, connecting rods and crankshafts
Alloy and case-hardening steels
Similar grades compared
| الدرجة | C % | Mn % | Cr % | Ni % | Tensile, first listed condition |
|---|---|---|---|---|---|
| 4140 / 42CrMo4 | 0.38–0.43 | 0.75–1.00 | 0.80–1.10 | ≤0.25 | 655 MPa |
| 4130 / 25CrMo4 | 0.28–0.33 | 0.40–0.60 | 0.80–1.10 | ≤0.25 | 590–760 MPa |
| 4135 / 34CrMo4 | 0.33–0.38 | 0.70–0.90 | 0.80–1.10 | ≤0.25 | 1000–1200 MPa |
| 4340 / EN24 | 0.38–0.43 | 0.60–0.80 | 0.70–0.90 | 1.65–2.00 | 745 MPa |
| 5140 / 41Cr4 | 0.38–0.43 | 0.70–0.90 | 0.70–0.90 | ≤0.25 | 570 MPa |
| 6150 / 51CrV4 | 0.48–0.53 | 0.70–0.90 | 0.80–1.10 | ≤0.40 | 670 MPa |
| 16MnCr5 | 0.13–0.18 | 0.70–0.90 | 0.70–0.90 | ≤0.25 | ≥1000 MPa |
| 20MnCr5 | 0.17–0.22 | 0.70–0.90 | 0.70–0.90 | ≤0.25 | ≥1200 MPa |
| 655M13 / EN36A | 0.08–0.13 | 0.45–0.65 | 1.00–1.40 | 3.00–3.50 | 700–770 MPa |
| 8620 / 20NiCrMo2-2 | 0.18–0.23 | 0.70–0.90 | 0.40–0.60 | 0.40–0.70 | 530 MPa |
Composition from the US standard where one exists, otherwise the first standard listed on each grade's page. Strength conditions differ between grades; open a grade for its full table.
أسئلة وأجوبة
Common questions
What is EN19 equivalent to?
EN19 is the old BS 970 name for 708M40. Its usual equivalents are AISI 4140 in the USA, 42CrMo4 (1.7225) in Europe, 42Cr4Mo2 in India and SCM440 in Japan. The chemistries overlap closely but are not identical, so check the limits when a drawing calls for one exact standard.
Is 42CrMo4 the same as 4140?
They are close equivalents, not the same specification. 42CrMo4 allows 0.38–0.45% carbon and 0.90–1.20% chromium; 4140 specifies 0.38–0.43% carbon, 0.80–1.10% chromium and slightly more manganese. A heat can often be certified to both, but each certificate refers to one standard.
What does EN19T mean?
The letter after EN19 or 708M40 is the BS 970 heat-treated tensile condition. Condition S is 775–925 MPa, T is 850–1000 MPa and U is 925–1075 MPa tensile strength. The condition that can be reached depends on the ruling section of the bar.
Can 4140 steel be welded?
Yes, but it needs a qualified procedure. Its carbon content makes the weld zone harden and crack-sensitive, so preheat, controlled interpass temperature, slow cooling and post-weld heat treatment are normally required. Welding hardened and tempered 4140 also changes its local properties.
What is the hardness of 4140?
Annealed 4140 is typically about 197 HB, and soft-annealed 42CrMo4 is supplied at no more than 241 HB. Hardened and tempered bar is commonly 248–302 HB (EN19T) and higher strength conditions go above 300 HB. Final hardness depends on tempering temperature and section size.
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Related references
References
Sources
- thyssenkrupp Materials Services, Werkstoffdatenblatt 42CrMo4 / 42CrMoS4 (1.7225 / 1.7227), based on DIN EN 10083-3:2007 — EN composition, +QT properties by diameter, heat treatment, welding notes.
- AZoM, AISI 4140 Alloy Steel (UNS G41400) — Typical annealed properties, machinability rating, US heat-treatment practice, related ASTM/SAE designations.
- Wikipedia, 41xx steel (SAE composition table citing the Central Steel & Wire catalog) — SAE/AISI 4140 bar composition.
- West Yorkshire Steel, 708M40 alloy steel — BS 970 composition, conditions S/T/U, heat treatment, tempering range to avoid.
- Bureau of Indian Standards, IS 1570 (Part 4):1988 Schedules for wrought steels, alloy steels (Public.Resource.Org copy) — Table 1 composition for 42Cr4Mo2; Table 4 hardened and tempered properties.
- Bureau of Indian Standards, IS 11169 (Part 1):2022 Steels for cold heading and cold extrusion, wrought carbon and alloy steels (Public.Resource.Org copy) — Table C.2 ladle-analysis limits for 40Cr4Mo2; Table E.1 cross-reference to SAE 4140 and JIS SCM440.
- Total Materia, IS 40Cr1Mo28 — Legacy Indian designation under IS 4368:1967.
- zknives steel database, EN19 — EN19 as the older name of 708M40.
Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.