Steel 15MnB-HR (Hot rolled)
Supply condition · default condition
GB 15MnB
Default mill stock condition for bar and plate before machining and heat treatment.
Values for the HR condition
Other 15MnB tempers and conditions
15MnB is listed in 8 conditions; see the grade overview at 15MnB.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold-forged bolts, nuts and rivets where maximum cold upsettability is required. | 270 | 450 | 30 | 135 HB | 8.5 % IACS |
Solution annealed | Pick for maximum softness and dimensional stability before heavy machining or deep drawing. | 310 | 510 | 26 | 156 HB | 8.5 % IACS |
HRDefaultThis page Hot rolled | Default mill stock condition for bar and plate before machining and heat treatment. | 380 | 590 | 21 | 187 HB | — |
Normalized | Standard pre-treatment for uniform fine grain and predictable case-hardening response. | 400 | 610 | 22 | 190 HB | 8 % IACS |
Cold drawn | Pick for close-tolerance, bright-finish shafting where strength is raised by drawing rather than heat treatment. | 560 | 680 | 11 | 210 HB | 8 % IACS |
Quenched and tempered | Use for through-hardened shafts, links and structural parts needing balanced strength and toughness. | 660 | 830 | 16 | 24 HRC | — |
Carburized and hardened | Primary service condition for gears, pins and sprockets: hard 0.6–1.2 mm case on a tough low-carbon core. | 780 | 1,000 | 11 | 60 HRC | — |
Quenched and low-temperature tempered | Direct-hardened condition for thin wear parts, tines, blades and chain links needing high hardness at low cost. | 950 | 1,250 | 10 | 41 HRC | — |
What is 15MnB-HR?
15MnB-HR is 15MnB supplied in the HR condition — default mill stock condition for bar and plate before machining and heat treatment. 15MnB-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 68% of steel grades. Elongation at break is 21% and the elastic modulus is 210 GPa (30.5 Msi). 15MnB-HR 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).
Advantages
- Forms and bends easily — 62/100, better than 78% of steel grades
- Readily welded — 72/100, better than 75% of steel grades
15MnB-HR properties
Typical room-temperature values for 15MnB-HR; 10 are specific to this condition. Other listed values are 15MnB reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15MnB-HR 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
15MnB-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 68% of steel grades. Elongation at break is 21% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
15MnB-HR is rated for continuous service to 350°C (662 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
15MnB-HR conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 15MnB-HR takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
15MnB-HR's machinability is good (58/100, better than 75% of steel grades); weldability very good (72/100); formability good (62/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15MnB-HR
Is 15MnB easy to machine?
Machine in the annealed or normalized state (~160–200 HB) with carbide at 120–180 m/min; the gummy low-carbon matrix needs positive rake and good chip control, and finish-machining after case hardening requires grinding.
Can 15MnB be welded?
Weldable by MIG/MAG, SMAW or resistance welding with CE(IIW) ≈ 0.40; preheat 100–150 °C on sections over ~20 mm, use low-hydrogen consumables, and avoid welding after carburizing.
Can 15MnB be formed, bent or molded?
Excellent cold heading and bending in the spheroidize-annealed condition; hot forge 1150–850 °C and avoid soaking above ~1200 °C or repeated high-temperature austenitising, which destroys the boron hardenability effect.
What surface finishes work on 15MnB?
No natural corrosion resistance — specify zinc or zinc–nickel plating, phosphate + oil, black oxide, hot-dip galvanizing (avoid for hardened parts due to hydrogen/temper risk) or painting; bake after plating to prevent hydrogen embrittlement in hardened conditions.
15MnB 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 |
|---|---|---|
| Ccase-hardening carbon level | 0.12 – 0.18 | 0.15 |
| Si | 0.17 – 0.37 | 0.27 |
| Mnmain hardenability element | 1 – 1.4 | 1.2 |
| Beffective (acid-soluble) boron | 8×10⁻⁴ – 0 | 0 |
| AlAlt, added to fix nitrogen and protect boron | 0.02 – 0.06 | 0.04 |
| Tioptional nitrogen fixer in some mill practices | ≤ 0.05 | — |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Crresidual | ≤ 0.25 | — |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
15MnB-HR — frequently asked
What is 15MnB-HR used for?
15MnB-HR is typically used for small gears, pins and bushings. In short: economical Cr-Mo case-hardening substitute; high weldability for boron steel; cold-heading quality available.
What is the yield strength of 15MnB-HR?
15MnB-HR has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 15MnB-HR easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in the annealed or normalized state (~160–200 HB) with carbide at 120–180 m/min; the gummy low-carbon matrix needs positive rake and good chip control, and finish-machining after case hardening requires grinding.
Can 15MnB-HR be welded?
Yes — weldability is rated very good (72/100). Weldable by MIG/MAG, SMAW or resistance welding with CE(IIW) ≈ 0.40; preheat 100–150 °C on sections over ~20 mm, use low-hydrogen consumables, and avoid welding after carburizing.
What surface finishes work on 15MnB-HR?
No natural corrosion resistance — specify zinc or zinc–nickel plating, phosphate + oil, black oxide, hot-dip galvanizing (avoid for hardened parts due to hydrogen/temper risk) or painting; bake after plating to prevent hydrogen embrittlement in hardened conditions.
Can 15MnB-HR be formed, bent or molded?
Excellent cold heading and bending in the spheroidize-annealed condition; hot forge 1150–850 °C and avoid soaking above ~1200 °C or repeated high-temperature austenitising, which destroys the boron hardenability effect.
What is the maximum service temperature of 15MnB-HR?
15MnB-HR is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15MnB-HR and 15MnB QT-LT?
HR is the default condition — default mill stock condition for bar and plate before machining and heat treatment. QT-LT: direct-hardened condition for thin wear parts, tines, blades and chain links needing high hardness at low cost. Yield strength is 380 MPa in HR versus 950 MPa in QT-LT.
Sources
- GB/T 3077 (alloy structural steels, boron grades) (2015)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating (boron steels, carburizing) — ASM International (1991)
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.