Steel 30MnB5 QT-40-45HRC
Hardness band
EN 30MnB5
Pick where wear resistance and high strength matter more than toughness (tillage parts, links, pins).
Values for the QT-40-45HRC condition
Other 30MnB5 tempers and conditions
30MnB5 is listed in 8 conditions; see the grade overview at 30MnB5.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Choose for cold heading, cold extrusion and severe upsetting of fastener blanks. | 350 | 570 | 22 | 175 HB | — |
Normalized | Use to refine grain and homogenise structure before machining or final hardening. | 430 | 680 | 18 | 14 HRC | 9 % IACS |
Hot rolled | Mill-supply condition of wire rod and bar before annealing or heat treatment. | 450 | 720 | 16 | 215 HB | — |
Cold drawn | Drawn-to-size wire or bright bar for cold heading lines and automatic machining. | 590 | 690 | 11 | 15 HRC | 8.5 % IACS |
+QTDefault Quenched and tempered | Standard delivered/finished strength condition for high-strength bolts, pins and wear parts. | 900 | 1,100 | 12 | 35 HRC | — |
Q&T to property class 10.9 | Fastener-specific temper for ISO 898-1 class 10.9 bolts and screws. | 980 | 1,100 | 11 | 35 HRC | — |
QT-40-45HRCThis page Q&T 40–45 HRC (low-temperature temper) | Pick where wear resistance and high strength matter more than toughness (tillage parts, links, pins). | 1,250 | 1,400 | 9 | 43 HRC | — |
Hardened | Intermediate condition only — full martensite, maximum hardness, must be tempered before service. | 1,400 | 1,800 | 3 | 50 HRC | 6.5 % IACS |
What is 30MnB5 QT-40-45HRC?
30MnB5 QT-40-45HRC is 30MnB5 heat treated to QT-40-45HRC — pick where wear resistance and high strength matter more than toughness (tillage parts, links, pins). 30MnB5 QT-40-45HRC has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 210 GPa (30.5 Msi). 30MnB5 QT-40-45HRC 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). +QT is the default condition FabDigit quotes; QT-40-45HRC is available on request or by drawing note.
Advantages
- High strength — 1,250 MPa (181 ksi), better than 95% of steel grades
Limitations
- Limited ductility — 9%, worse than 93% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
30MnB5 QT-40-45HRC properties
Typical room-temperature values for 30MnB5 QT-40-45HRC; 12 are specific to this condition. Other listed values are 30MnB5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30MnB5 QT-40-45HRC 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).
Mechanical16
30MnB5 QT-40-45HRC has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
30MnB5 QT-40-45HRC is rated for continuous service to 200°C (392 °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
30MnB5 QT-40-45HRC conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 30MnB5 QT-40-45HRC takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
30MnB5 QT-40-45HRC's machinability is poor (25/100, worse than 93% of steel grades); weldability poor (30/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 30MnB5 QT-40-45HRC
Is 30MnB5 easy to machine?
Machine in the annealed/cold-drawn state (~180–210 HB); at 33–39 HRC after Q&T use coated carbide, rigid setups and reduced feeds, or finish-grind.
Can 30MnB5 be welded?
Poor — CEV ~0.55–0.65 plus boron; if unavoidable use low-hydrogen consumables, 200–300 °C preheat and immediate stress relief, and expect a hard, crack-prone HAZ.
Can 30MnB5 be formed, bent or molded?
Designed for multi-station cold heading and extrusion in the spheroidize-annealed (≤207 HB) condition; hot forming 1100–850 °C, then normalize or re-anneal before Q&T.
What surface finishes work on 30MnB5?
No inherent corrosion resistance — use zinc or zinc-nickel plating (bake 190–230 °C to relieve hydrogen), zinc-flake dip-spin, phosphate+oil or black oxide; avoid aggressive acid pickling on hardened parts.
30MnB5 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 | 0.27 – 0.33 | 0.3 |
| Sicold-heading grades often ≤0.30 | ≤ 0.4 | 0.2 |
| Mn | 1.15 – 1.45 | 1.3 |
| P | ≤ 0.03 | — |
| S≤0.025 for cold-heading wire per EN 10263-4 | ≤ 0.04 | — |
| Crresidual | ≤ 0.3 | 0.15 |
| Beffective (soluble) boron; Ti/Al added to fix nitrogen | 8×10⁻⁴ – 0.01 | 0 |
| Tinitrogen-fixing addition, producer practice | ≤ 0.05 | 0.03 |
| Fe | balance | — |
30MnB5 QT-40-45HRC — frequently asked
What is 30MnB5 QT-40-45HRC used for?
30MnB5 QT-40-45HRC is typically used for property class 10.9 bolts and screws, cold-headed high-strength fasteners, wheel bolts and studs, chassis and suspension fasteners, socket-head cap screws and threaded rod and stud bolts. In short: more hardenable than 20MnB4; class 10.9 cold-heading steel; poor weldability.
What is the yield strength of 30MnB5 QT-40-45HRC?
30MnB5 QT-40-45HRC has a typical yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 30MnB5 QT-40-45HRC easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine in the annealed/cold-drawn state (~180–210 HB); at 33–39 HRC after Q&T use coated carbide, rigid setups and reduced feeds, or finish-grind.
Can 30MnB5 QT-40-45HRC be welded?
Not readily — weldability is rated poor (30/100). Poor — CEV ~0.55–0.65 plus boron; if unavoidable use low-hydrogen consumables, 200–300 °C preheat and immediate stress relief, and expect a hard, crack-prone HAZ.
What surface finishes work on 30MnB5 QT-40-45HRC?
No inherent corrosion resistance — use zinc or zinc-nickel plating (bake 190–230 °C to relieve hydrogen), zinc-flake dip-spin, phosphate+oil or black oxide; avoid aggressive acid pickling on hardened parts.
Can 30MnB5 QT-40-45HRC be formed, bent or molded?
Designed for multi-station cold heading and extrusion in the spheroidize-annealed (≤207 HB) condition; hot forming 1100–850 °C, then normalize or re-anneal before Q&T.
What is the maximum service temperature of 30MnB5 QT-40-45HRC?
30MnB5 QT-40-45HRC is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10263-4 Steel rod, bars and wire for cold heading and cold extrusion — Steels for quenching and tempering — CEN (2018)
- ISO 898-1 Mechanical properties of fasteners — Bolts, screws and studs — ISO (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Boron cold-heading steel wire rod datasheets (30MnB5 / 30MnB4) — European and Chinese wire-rod producers (2023)
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.