Steel 6150 · hardness band
Steel 6150 Q&T 30-34 HRC
Properties of the Q&T 30-34 HRC condition, compared with the other 6150 tempers.
Tough, machinable hardened state for shafts and moderately loaded parts.
What is 6150 Q&T 30-34 HRC?
6150 Q&T 30-34 HRC is 6150 heat treated to Q&T 30-34 HRC — tough, machinable hardened state for shafts and moderately loaded parts. 6150 Q&T 30-34 HRC has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi). 6150 Q&T 30-34 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; Q&T 30-34 HRC is available on request or by drawing note.
Advantages
- High strength — 830 MPa (120 ksi), better than 87% of steel grades
6150 Q&T 30-34 HRC properties
Typical room-temperature values for 6150 Q&T 30-34 HRC — 9 properties are specific to this condition; the rest are grade-level values shared by every 6150 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
6150 Q&T 30-34 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical14
6150 Q&T 30-34 HRC has a yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
6150 Q&T 30-34 HRC 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
6150 Q&T 30-34 HRC 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 6150 Q&T 30-34 HRC takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 35%.
Manufacturability8
6150 Q&T 30-34 HRC's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (28/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 6150 tempers and conditions
6150 is also supplied in 10 other conditions. The full side-by-side table is on the 6150 overview.
- HRDefaultStandard stocked mill condition for bars and flats that will be machined and then heat treated by the user.600 MPa yield · 25 HRC
- Q&T 50-54 HRCMaximum hardness/wear condition for chisels, punches and cutting edges; low toughness, notch-sensitive.1,650 MPa yield · 52 HRC
- Q&T 44-48 HRCHigh elastic-limit condition for heavy leaf springs, torsion bars and hand tools.1,350 MPa yield · 46 HRC
- Q&TGeneral-purpose hardened spring/torsion-bar condition balancing high elastic limit with usable toughness.1,100 MPa yield · 40 HRC
- Q&T 30-34 HRCTough, machinable hardened state for shafts and moderately loaded parts.830 MPa yield · 32 HRC
- CDClose-tolerance bright bar with raised yield strength; use where little or no further machining is needed.750 MPa yield · 26 HRC
- NormalizedUniform fine-grained structure for stable machining and a good starting point for hardening of forgings.615 MPa yield · 27 HRC
- AnnealedSoftest and most machinable condition; choose for heavy machining, cold forming or as the delivery state before hardening.415 MPa yield · 197 HB
Working with 6150 Q&T 30-34 HRC
Is 6150 easy to machine?
Machine in the annealed or ≤32 HRC condition with rigid setups, carbide tooling and 30–40 % lower speeds than 1045; above 45 HRC grind or use CBN.
Can 6150 be welded?
Poor weldability (C≈0.50, CE>0.8): avoid on springs; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and temper immediately after welding.
Can 6150 be formed, bent or molded?
Cold form only in the annealed/spheroidized state; hot forge 1100–850 °C then normalize, and coil springs hot or from pre-tempered (OT) wire.
What surface finishes work on 6150?
No corrosion resistance — phosphate + oil, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement), or paint/powder coat; shot peen springs to boost fatigue life.
6150 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 |
|---|---|---|
| CAISI 6150 0.48–0.53; EN 50CrV4 0.47–0.55 | 0.47 – 0.55 | 0.5 |
| Si | 0.15 – 0.4 | 0.25 |
| MnAISI 0.70–0.90 | 0.5 – 0.9 | 0.8 |
| Cr | 0.8 – 1.2 | 1 |
| VAISI 6150 V min 0.15 | 0.1 – 0.25 | 0.17 |
| P | ≤ 0.03 | — |
| Smax (AISI allows 0.040) | ≤ 0.03 | — |
| Niresidual | ≤ 0.35 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
6150 Q&T 30-34 HRC — frequently asked
What is 6150 Q&T 30-34 HRC used for?
6150 Q&T 30-34 HRC is typically used for springs, bolts and stamped tool blanks. In short: chromium-vanadium spring bar.
What is the yield strength of 6150 Q&T 30-34 HRC?
6150 Q&T 30-34 HRC has a typical yield strength of 830 MPa (120 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 6150 Q&T 30-34 HRC easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed or ≤32 HRC condition with rigid setups, carbide tooling and 30–40 % lower speeds than 1045; above 45 HRC grind or use CBN.
Can 6150 Q&T 30-34 HRC be welded?
Not readily — weldability is rated poor (28/100). Poor weldability (C≈0.50, CE>0.8): avoid on springs; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and temper immediately after welding.
What surface finishes work on 6150 Q&T 30-34 HRC?
No corrosion resistance — phosphate + oil, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement), or paint/powder coat; shot peen springs to boost fatigue life.
Can 6150 Q&T 30-34 HRC be formed, bent or molded?
Cold form only in the annealed/spheroidized state; hot forge 1100–850 °C then normalize, and coil springs hot or from pre-tempered (OT) wire.
What is the maximum service temperature of 6150 Q&T 30-34 HRC?
6150 Q&T 30-34 HRC 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 6150-HR and 6150-OT?
HR is the default condition — standard stocked mill condition for bars and flats that will be machined and then heat treated by the user. OT: ready-to-coil hardened-and-tempered wire for valve springs and dynamically loaded coil springs; strength falls with increasing diameter. Yield strength is 600 MPa in HR versus 1,450 MPa in OT.
Can FabDigit make parts in 6150 Q&T 30-34 HRC?
Yes — 6150 Q&T 30-34 HRC 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
- ASTM A29/A29M – Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J404 – Chemical Compositions of SAE Alloy Steels — SAE International (2009)
- EN 10089 – Hot rolled steels for quenched and tempered springs — CEN (2002)
- EN 10083-3 – Steels for quenching and tempering: alloy steels — CEN (2006)
- GB/T 1222 – (Spring steels) — SAC (2016)
- EN 10270-2 – Steel wire for mechanical springs: oil hardened and tempered wire — CEN (2011)
- ASM Handbook Vol.1 – Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 – Heat Treating — ASM International (1991)
- Low-alloy spring steel property tables (50CrV4 / 1.7166) — Stahlschlüssel / Key to Steel (2019)
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.