Steel 5140 · heat-treated state
Steel 5140 Q&T
Properties of the Q&T condition, compared with the other 5140 tempers.
Standard general-purpose condition for shafts and gears — good strength/toughness balance (~30 HRC).
What is 5140 Q&T?
5140 Q&T is 5140 heat treated to Q&T — standard general-purpose condition for shafts and gears — good strength/toughness balance (~30 HRC). 5140 Q&T has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 17.5% and the elastic modulus is 210 GPa (30.5 Msi). 5140 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). HR is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
5140 Q&T properties
Typical room-temperature values for 5140 Q&T — 13 properties are specific to this condition; the rest are grade-level values shared by every 5140 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
5140 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
5140 Q&T has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Elongation at break is 17.5% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
5140 Q&T is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
5140 Q&T conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 5140 Q&T takes about 26 MJ of energy and emits 1.9 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
5140 Q&T's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (35/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 5140 tempers and conditions
5140 is also supplied in 11 other conditions. The full side-by-side table is on the 5140 overview.
- HRDefaultCheapest stock condition for parts that will be heat treated after rough machining.440 MPa yield · 200 HB
- Q&T 48-52HRCMaximum-hardness condition for small wear parts; brittle, avoid stress raisers and impact.1,560 MPa yield · 50 HRC
- Q&T 40-45HRCUse where wear and high yield strength dominate and toughness demands are moderate.1,260 MPa yield · 42 HRC
- Q&T 34-38HRCHigher-strength band for heavily loaded shafts and gear blanks still requiring machining.1,080 MPa yield · 36 HRC
- Q&TStandard general-purpose condition for shafts and gears — good strength/toughness balance (~30 HRC).860 MPa yield · 32 HRC
- IHSelect for shaft journals, splines and gear teeth needing a hard wear surface with a tough core.860 MPa yield · 55 HRC
- Q&T 28-32HRCSpecified hardness band for machinable shafts, couplings and moderately loaded gears.840 MPa yield · 30 HRC
- CDChoose for close-tolerance, bright-finish bar used as-supplied for lightly loaded shafts and pins.660 MPa yield · 19 HRC
- NormalizedUniform fine-grain structure for forgings before machining or final Q&T.472 MPa yield · 20 HRC
- AnnealedSoftest, most machinable condition; use for heavy stock removal before hardening.293 MPa yield · 167 HB
Working with 5140 Q&T
Is 5140 easy to machine?
Machines well at 180–230 HB (≈65 % of 1212); above 35 HRC use coated carbide, rigid setups and reduced feeds, and prefer rough-machining before final temper.
Can 5140 be welded?
Weldable with care only — preheat 250–350 °C, low-hydrogen consumables, and temper/stress-relieve immediately after welding to avoid martensitic cracking.
Can 5140 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming limited to the spheroidize-annealed condition (cold heading of bolts).
What surface finishes work on 5140?
No corrosion resistance — protect by black oxide, phosphate + oil, zinc or chrome plating (bake to relieve hydrogen above 40 HRC); polishes to a fine finish when clean and hardened.
5140 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 |
|---|---|---|
| CGB 40Cr: 0.37–0.44 | 0.38 – 0.43 | 0.4 |
| SiGB 40Cr: 0.17–0.37 | 0.15 – 0.35 | 0.25 |
| MnGB 40Cr: 0.50–0.80 | 0.7 – 0.9 | 0.8 |
| CrGB 40Cr / 41Cr4: 0.80–1.10 | 0.7 – 0.9 | 0.8 |
| P | ≤ 0.04 | — |
| Smax; 0.015–0.035 for resulfurized machining grades | ≤ 0.04 | — |
| Fe | balance | — |
5140 Q&T — frequently asked
What is 5140 Q&T used for?
5140 Q&T is typically used for shafts, gears and axles. In short: workhorse chromium spring bar.
What is the yield strength of 5140 Q&T?
5140 Q&T has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 5140 Q&T easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machines well at 180–230 HB (≈65 % of 1212); above 35 HRC use coated carbide, rigid setups and reduced feeds, and prefer rough-machining before final temper.
Can 5140 Q&T be welded?
With care — weldability is rated fair (35/100). Weldable with care only — preheat 250–350 °C, low-hydrogen consumables, and temper/stress-relieve immediately after welding to avoid martensitic cracking.
What surface finishes work on 5140 Q&T?
No corrosion resistance — protect by black oxide, phosphate + oil, zinc or chrome plating (bake to relieve hydrogen above 40 HRC); polishes to a fine finish when clean and hardened.
Can 5140 Q&T be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold forming limited to the spheroidize-annealed condition (cold heading of bolts).
What is the maximum service temperature of 5140 Q&T?
5140 Q&T 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 5140-HR and 5140-IH?
HR is the default condition — cheapest stock condition for parts that will be heat treated after rough machining. IH: select for shaft journals, splines and gear teeth needing a hard wear surface with a tough core. Yield strength is 440 MPa in HR versus 860 MPa in IH.
Can FabDigit make parts in 5140 Q&T?
Yes — 5140 Q&T is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- GB/T 3077 — Alloy Structure Steels (40Cr) — SAC (2015)
- EN 10083-3 — Quenched and tempered steels, 41Cr4 (1.7035) — CEN (2006)
- JIS G 4053 — Low-alloyed structural steels (SCr440) — JSA (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- Mysteel / SMM 40Cr (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.