Steel EN31 QT-HT
Hardness band
BS EN31 · AISI/SAE 52100 · EN 1.3505 · GB GCr15
QT-HT = q&T, high temper 35–45 HRC
Tough, machinable hardened condition for die bodies, punch shanks and heavily loaded structural parts.
Values for the QT-HT condition
Other EN31 tempers and conditions
EN31 is listed in 9 conditions; see the grade overview at EN31.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard stocked condition — soft, spheroidised carbides for machining and cold forming before hardening. | 420 | 690 | 25 | 195 HB | 46 W/m·K |
Hot rolled | As-rolled bar/billet for onward forging or annealing; too hard and brittle for direct machining. | 550 | 900 | 12 | 29 HRC | 7.8 % IACS |
Cold drawn | Close-tolerance bright bar for precision turning; slightly harder than annealed with better surface and straightness. | 600 | 780 | 12 | 20 HRC | 7.8 % IACS |
Normalized | Used to break up carbide networks in forgings before spheroidizing; not a delivery condition for machining. | 620 | 1,000 | 10 | 33 HRC | 7.8 % IACS |
QT-HTThis page Q&T, high temper 35–45 HRC | Tough, machinable hardened condition for die bodies, punch shanks and heavily loaded structural parts. | 1,150 | 1,350 | 8 | 40 HRC | — |
Q&T, medium temper 50–56 HRC | Chosen for tooling and shafts needing more toughness than a bearing race; slight loss of wear resistance. | 1,550 | 1,800 | 4 | 53 HRC | — |
Hardened & Stabilized | Higher tempering for dimensional stability at elevated bearing temperatures (S1/SN designations), trading a little hardness. | 1,750 | 2,050 | 1.5 | 59 HRC | — |
Hardened & Tempered 60–64 HRC | The classic bearing condition — maximum hardness and rolling contact fatigue life; low toughness, service ≤120–150 °C. | 1,900 | 2,250 | 1 | 62 HRC | — |
Induction hardened | Selective surface hardening for large rings, rollers and shafts where a tough core plus hard raceway is wanted. | 1,900 | 2,200 | 1 | 61 HRC | 7 % IACS |
What is EN31 QT-HT?
EN31 QT-HT is EN31 heat treated to QT-HT — tough, machinable hardened condition for die bodies, punch shanks and heavily loaded structural parts. EN31 QT-HT has a yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi). EN31 QT-HT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,424°C (2,595 °F). ANN is the default condition FabDigit quotes; QT-HT is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- High strength — 1,150 MPa (167 ksi), better than 94% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Difficult to machine — 22/100, worse than 95% of steel grades
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
EN31 QT-HT properties
Typical room-temperature values for EN31 QT-HT; 13 are specific to this condition. Other listed values are EN31 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
EN31 QT-HT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,424°C (2,595 °F).
Mechanical16
EN31 QT-HT has a yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
EN31 QT-HT is rated for continuous service to 400°C (752 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
EN31 QT-HT 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 EN31 QT-HT takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
EN31 QT-HT's machinability is poor (22/100, worse than 95% of steel grades); weldability poor (15/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with EN31 QT-HT
Is EN31 easy to machine?
Machine only in the spheroidize-annealed state (~40% of 1212) with rigid setups and carbide tooling; hardened 60+ HRC parts require CBN hard turning or grinding.
Can EN31 be welded?
Effectively non-weldable — high carbon equivalent gives untempered martensite and cracks; if unavoidable, preheat 300–400 °C, low-hydrogen filler and immediate stress relief.
Can EN31 be formed, bent or molded?
Cold heading/ball rolling is done only on soft annealed stock; hot forge 1050–1150 °C, do not finish below ~880 °C, then slow cool and spheroidize anneal.
What surface finishes work on EN31?
Cannot be anodized; typical finishes are hard grinding/lapping to mirror plus preservative oil, black oxide, manganese phosphate, zinc or hard chrome plating — bake after plating to avoid hydrogen embrittlement.
EN31 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 |
|---|---|---|
| CBS 970 EN31; AISI 52100 narrows to 0.93–1.05 | 0.9 – 1.2 | 1 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn52100/GCr15 typically 0.25–0.45 | 0.3 – 0.75 | 0.5 |
| Cr | 1 – 1.6 | 1.4 |
| Pbearing quality (GB/T 18254) limits to 0.025 | ≤ 0.05 | 0.02 |
| Sbearing quality limits to 0.025 | ≤ 0.05 | 0.02 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Moresidual | ≤ 0.1 | 0.03 |
| Ovacuum-degassed bearing quality, ppm-level control | ≤ 0 | 8×10⁻⁴ |
| Fe | balance | — |
EN31 QT-HT — frequently asked
What is EN31 QT-HT used for?
EN31 QT-HT is typically used for bearings, gauges, precision tools and rollers. In short: classic 52100 bearing steel; through-hardens to 60–64 HRC; effectively non-weldable.
What is the yield strength of EN31 QT-HT?
EN31 QT-HT has a typical yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is EN31 QT-HT easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of steel grades). Machine only in the spheroidize-annealed state (~40% of 1212) with rigid setups and carbide tooling; hardened 60+ HRC parts require CBN hard turning or grinding.
Can EN31 QT-HT be welded?
Not readily — weldability is rated poor (15/100). Effectively non-weldable — high carbon equivalent gives untempered martensite and cracks; if unavoidable, preheat 300–400 °C, low-hydrogen filler and immediate stress relief.
What surface finishes work on EN31 QT-HT?
Cannot be anodized; typical finishes are hard grinding/lapping to mirror plus preservative oil, black oxide, manganese phosphate, zinc or hard chrome plating — bake after plating to avoid hydrogen embrittlement.
Can EN31 QT-HT be formed, bent or molded?
Cold heading/ball rolling is done only on soft annealed stock; hot forge 1050–1150 °C, do not finish below ~880 °C, then slow cool and spheroidize anneal.
What is the maximum service temperature of EN31 QT-HT?
EN31 QT-HT 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 EN31-ANN and EN31 QT60-64?
ANN is the default condition — standard stocked condition — soft, spheroidised carbides for machining and cold forming before hardening. QT60-64: the classic bearing condition — maximum hardness and rolling contact fatigue life; low toughness, service ≤120–150 °C. Yield strength is 420 MPa in ANN versus 1,900 MPa in QT60-64.
Sources
- BS 970: Wrought steels — EN31 / 535A99 — BSI (1991)
- ASTM A295 — High-Carbon Anti-Friction Bearing Steel (52100) — ASTM (2020)
- GB/T 18254 (GCr15) — SAC (2016)
- DIN EN ISO 683-17 / Werkstoff 1.3505 — DIN/ISO (2014)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture (rolling contact fatigue) — ASM International (1996)
- Bearing steel 100Cr6 / 52100 datasheet — Ovako / Sandvik (2021)
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.