Steel 4142
AISI/SAE 4142 · UNS G41420 · EN 42CrMoS4
4142 is a chromium-molybdenum through-hardening alloy steel in the SAE-AISI 41xx family (UNS G41420), carrying slightly more carbon than 4140 for higher as-quenched hardness.
Values for the HR condition
4142 tempers and conditions
4142 is supplied in 12 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed for machining and forming | Softest condition; pick for deep machining, cold forming or before final quench and temper. | 420 | 655 | 25 | 197 HB | 43 W/m·K |
HRDefault Hot rolled | Cheapest stock form for parts that will be heat treated or rough-machined after purchase. | 450 | 730 | 20 | 17 HRC | 7.8 % IACS |
Cold drawn | Straight, close-tolerance bright bar with better surface and chip control than hot rolled; use where no further heat treatment is planned. | 655 | 760 | 15 | 19 HRC | 7.8 % IACS |
Cold rolled | Cold-rolled flat/strip product with tight thickness tolerance and smooth surface; strength from cold work only. | 670 | 790 | 12 | 21 HRC | 7.8 % IACS |
870 °C air cooled | Uniform fine-grain structure with medium-high strength; used as a pre-machining or as-supplied condition for forgings. | 670 | 1,035 | 17 | 32 HRC | 7.6 % IACS |
High-temper condition | Choose when hardness must be capped for stress-corrosion / sour-service or maximum toughness. | 720 | 830 | 20 | 24 HRC | 7.7 % IACS |
Tempered ~590 °C | Most commonly specified pre-hard bar hardness band: good strength with straightforward machining. | 880 | 1,000 | 17 | 30 HRC | 7.6 % IACS |
Quenched and tempered | Standard workhorse condition for shafts and machine parts needing high strength with usable toughness and machinability. | 960 | 1,080 | 16 | 32 HRC | — |
Tempered ~540 °C | Higher-strength shafting and tooling bodies where machining is still required after heat treatment. | 1,010 | 1,120 | 15 | 34 HRC | 7.5 % IACS |
Tempered ~480 °C | For wear-loaded pins, spindles and hydraulic components; machining now needs carbide tooling. | 1,200 | 1,320 | 13 | 40 HRC | — |
Low-temper high-hardness condition | Maximum practical strength/wear from 4142; accept low toughness and difficult machining (grind/EDM). | 1,450 | 1,600 | 10 | 48 HRC | — |
As-quenched | Intermediate in-process state only — must be tempered promptly to avoid quench cracking. | 1,650 | 2,050 | 2 | 56 HRC | 6.9 % IACS |
What is 4142?
4142 is a chromium-molybdenum through-hardening alloy steel in the SAE-AISI 41xx family (UNS G41420), carrying slightly more carbon than 4140 for higher as-quenched hardness. Bar is stocked hot-rolled, cold-drawn, annealed or normalized at around 450 MPa yield, 730 MPa tensile and 217 HB, and as pre-hardened quench-and-tempered stock from 22–26 HRC up to 45–50 HRC for shafts, gears, drive components and high-strength fasteners. The higher carbon makes welding more demanding than 4140, corrosion resistance is nil without a coating, and machinability drops sharply above ~35 HRC; 4140 is the nearest and more widely available alternative. 4142 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 4142 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4142 used for?
- Shafts
- Industrial gears
- Drive shafts
4142 properties
Typical room-temperature values for 4142-HR; bars are the position among steel grades.
Physical3
4142 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical17
4142 has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4142 is rated for continuous service to 400°C (752 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), worse than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4142 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4142 takes about 29 MJ of energy and emits 2 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability7
4142's machinability is fair (54/100, better than 54% of steel grades); weldability fair (40/100); formability fair (42/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 4142 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4142
Is 4142 easy to machine?
Machines best at 197–255 HB (annealed or 22–28 HRC); above ~35 HRC use coated carbide, rigid setups and reduced speeds, or grind.
Can 4142 be welded?
Weldable with low-hydrogen consumables but requires 200–320 °C preheat, controlled interpass and post-weld temper below the part's tempering temperature; avoid welding fully hardened sections.
Can 4142 be formed, bent or molded?
Cold form only in the annealed condition with generous radii; most shaping is done hot (1050–1200 °C forging) followed by normalize/anneal.
Manufacturability
The process limits FabDigit applies to 4142. Every 4142 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better54 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair42 / 100 |
|---|---|
| Weldability | Better40 / 100 |
4142 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.4 – 0.45 | 0.42 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.8 – 1.1 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Pmax, SAE J404 | ≤ 0.04 | |
| Smax, SAE J404 | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4142?
No anodizing; protect with black oxide, manganese phosphate, zinc or hard chrome plating (bake to avoid hydrogen embrittlement above ~40 HRC) or nitriding for wear.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4142 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G41420
- EN / DIN / Werkstoff-Nr.
- 42CrMoS4
How much does 4142 cost?
4142 is a standard-cost steel ($$), cheaper than about 61% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4142 — frequently asked
What is 4142 used for?
4142 is typically used for shafts, industrial gears and drive shafts. In short: standard Cr-Mo machining bar.
What is the yield strength of 4142?
4142 has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 730 MPa (106 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 4142 easy to machine?
Reasonably — machinability is rated fair (54/100, better than 54% of steel grades). Machines best at 197–255 HB (annealed or 22–28 HRC); above ~35 HRC use coated carbide, rigid setups and reduced speeds, or grind.
Can 4142 be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but requires 200–320 °C preheat, controlled interpass and post-weld temper below the part's tempering temperature; avoid welding fully hardened sections.
What surface finishes work on 4142?
No anodizing; protect with black oxide, manganese phosphate, zinc or hard chrome plating (bake to avoid hydrogen embrittlement above ~40 HRC) or nitriding for wear.
Can 4142 be formed, bent or molded?
Cold form only in the annealed condition with generous radii; most shaping is done hot (1050–1200 °C forging) followed by normalize/anneal.
What is the maximum service temperature of 4142?
4142 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4142-HR and 4142-AQ?
HR is the default condition — cheapest stock form for parts that will be heat treated or rough-machined after purchase. AQ: intermediate in-process state only — must be tempered promptly to avoid quench cracking. Yield strength is 450 MPa in HR versus 1,650 MPa in AQ.
How much does 4142 cost?
4142 is a standard-cost steel ($$), cheaper than about 61% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 4142?
Yes — 4142 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
- GB/T 3077 — Alloy Structural Steels (42CrMo) — SAC (2015)
- 4140/4142 alloy bar datasheets — Various bar producers/distributors (2023)
- 42CrMo — Mysteel / 1688 (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.