Steel 4150 · heat-treated state
Steel 4150 Q&T
Properties of the Q&T condition, compared with the other 4150 tempers.
General-purpose oil quench from ~845 °C plus ~540 °C temper — the standard commercial 'HT' condition (~302–352 HB) balancing strength and toughness.
What is 4150 Q&T?
4150 Q&T is 4150 heat treated to Q&T — general-purpose oil quench from ~845 °C plus ~540 °C temper — the standard commercial 'HT' condition (~302–352 HB) balancing strength and toughness. 4150 Q&T has a yield strength of 1,105 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 4150 Q&T 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). HR is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- High strength — 1,105 MPa (160 ksi), better than 93% of steel grades
- High service temperature — 480°C (896 °F), better than 88% of steel grades
Limitations
- Difficult to weld — 15/100, worse than 91% of steel grades
- Difficult to machine — 35/100, worse than 83% of steel grades
4150 Q&T properties
Typical room-temperature values for 4150 Q&T — 16 properties are specific to this condition; the rest are grade-level values shared by every 4150 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
4150 Q&T 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).
Mechanical14
4150 Q&T has a yield strength of 1,105 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4150 Q&T is rated for continuous service to 480°C (896 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), better than 50% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4150 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 4150 Q&T takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability8
4150 Q&T's machinability is fair (35/100, worse than 83% of steel grades); weldability poor (15/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 4150 tempers and conditions
4150 is also supplied in 10 other conditions. The full side-by-side table is on the 4150 overview.
- HRDefaultStandard as-rolled bar stock — cheapest starting form for parts that will be machined and then heat treated.520 MPa yield · 21 HRC
- Q&T 48-52 HRCLow-temper, near-maximum hardness for wear parts and punches; grinding rather than turning, and notch sensitivity is high.1,550 MPa yield · 50 HRC
- Q&T 40-44 HRCHigher-hardness temper for wear surfaces, tool bodies and drill collars; machining now needs carbide tooling.1,250 MPa yield · 42 HRC
- Q&TGeneral-purpose oil quench from ~845 °C plus ~540 °C temper — the standard commercial 'HT' condition (~302–352 HB) balancing strength and toughness.1,105 MPa yield · 37 HRC
- Q&T 32-36 HRCCommon prehardened bar hardness for gears, die holders and hydraulic components needing wear resistance with machinability.985 MPa yield · 34 HRC
- Q&T 28-32 HRCTough, readily re-machinable prehardened condition for shafts, arbors and fixtures that must not be re-heat-treated.860 MPa yield · 30 HRC
- CDCold-drawn (usually annealed-then-drawn) bar for close size tolerance, straightness and good chip control on screw machines.830 MPa yield · 28 HRC
- NormalizedAir cooled from ~870 °C — uniform fine grain and higher strength than annealed; used to homogenize forgings before final machining or hardening.735 MPa yield · 34 HRC
- AnnealedFull anneal (~815–840 °C, furnace cool) — softest, most machinable condition and the usual delivery state for bar that will be hardened later.380 MPa yield · 197 HB
Working with 4150 Q&T
Is 4150 easy to machine?
Machine in the annealed or 28–32 HRC condition with rigid setups and carbide tooling; above 40 HRC switch to hard turning inserts or grinding.
Can 4150 be welded?
Poor weldability (CE ≈ 0.95): preheat 300–400 °C, low-hydrogen consumables, and temper/stress relieve immediately after welding to avoid HAZ cracking.
Can 4150 be formed, bent or molded?
Hot forge 1100–1200 °C and normalize afterwards; cold forming is limited to the spheroidize-annealed condition with generous bend radii.
What surface finishes work on 4150?
No natural corrosion resistance — use black oxide, manganese phosphate, zinc or hard chrome plating (bake to avoid hydrogen embrittlement above 40 HRC), or nitriding for wear surfaces.
4150 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 |
|---|---|---|
| CSAE J404 / AISI 4150 | 0.48 – 0.53 | 0.5 |
| 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 |
| P | ≤ 0.04 | — |
| Smax; 4150H/resulfurized variants differ | ≤ 0.04 | — |
| Fe | balance | — |
4150 Q&T — frequently asked
What is 4150 Q&T used for?
4150 Q&T is typically used for gun barrels, axles and gears. In short: deep-hardening toughness.
What is the yield strength of 4150 Q&T?
4150 Q&T has a typical yield strength of 1,105 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 4150 Q&T easy to machine?
Not especially — machinability is rated fair (35/100, worse than 83% of steel grades). Machine in the annealed or 28–32 HRC condition with rigid setups and carbide tooling; above 40 HRC switch to hard turning inserts or grinding.
Can 4150 Q&T be welded?
Not readily — weldability is rated poor (15/100). Poor weldability (CE ≈ 0.95): preheat 300–400 °C, low-hydrogen consumables, and temper/stress relieve immediately after welding to avoid HAZ cracking.
What surface finishes work on 4150 Q&T?
No natural corrosion resistance — use black oxide, manganese phosphate, zinc or hard chrome plating (bake to avoid hydrogen embrittlement above 40 HRC), or nitriding for wear surfaces.
Can 4150 Q&T be formed, bent or molded?
Hot forge 1100–1200 °C and normalize afterwards; cold forming is limited to the spheroidize-annealed condition with generous bend radii.
What is the maximum service temperature of 4150 Q&T?
4150 Q&T is rated for continuous use to about 480°C (896 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4150-HR and 4150-CD?
HR is the default condition — standard as-rolled bar stock — cheapest starting form for parts that will be machined and then heat treated. CD: cold-drawn (usually annealed-then-drawn) bar for close size tolerance, straightness and good chip control on screw machines. Yield strength is 520 MPa in HR versus 830 MPa in CD.
Can FabDigit make parts in 4150 Q&T?
Yes — 4150 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)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- EN 10083-3 — Quenched and tempered steels: alloy steels (50CrMo4, 1.7228) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. — machinability ratings and heat treating data — Industrial Press (2020)
- Alloy bar 4150 / 50CrMo4 datasheet — Böhler / Ovako / TimkenSteel (2022)
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.