Steel 15B62 QT 45-50 HRC
Hardness band
EN 15B62 · UNS G15621
Classic spring condition — highest usable elastic limit for coil and leaf springs, spring clips and track components.
Values for the QT 45-50 HRC condition
Other 15B62 tempers and conditions
15B62 is listed in 10 conditions; see the grade overview at 15B62.
- A
- HR
- N
- CD
- QT 33-38 HRC
- QT 40-45 HRC
- AT
- QT 45-50 HRC
- QT 50-55 HRC
- AQ
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for cold heading of fastener blanks, deep machining or cold forming before hardening. | 420 | 700 | 22 | 200 HB | — |
HRDefault Hot rolled | Standard mill supply condition for bar and coil that will be formed and then quenched and tempered by the part maker. | 520 | 930 | 12 | 270 HB | — |
Normalized | Use to refine and homogenise structure after forging, before hardening or machining. | 570 | 1,000 | 11 | 30 HRC | 8 % IACS |
Cold drawn | Choose for close-tolerance bright bar and wire that needs straightness and higher as-supplied yield. | 730 | 860 | 10 | 24 HRC | 8 % IACS |
oil quenched, tempered ~575 °C | Tough medium-hardness setting for heavy-duty bolts, pins and shafts where impact matters more than peak strength. | 980 | 1,120 | 15 | 35 HRC | — |
oil quenched, tempered ~480 °C | Balanced spring/structural setting for leaf springs, clips, tillage tools and 10.9-class fasteners. | 1,250 | 1,400 | 10 | 43 HRC | — |
Austempered | Salt-bath bainitic route for thin springs and clips needing high strength with better ductility and less distortion than martensite + temper. | 1,250 | 1,500 | 11 | 45 HRC | 8 % IACS |
QT 45-50 HRCThis page oil quenched, tempered ~400 °C (spring temper) | Classic spring condition — highest usable elastic limit for coil and leaf springs, spring clips and track components. | 1,450 | 1,620 | 8 | 48 HRC | — |
oil quenched, tempered ~300 °C | Wear-oriented setting for plough shares, cultivator points and cutting edges; low toughness, avoid shock and notches. | 1,650 | 1,900 | 6 | 53 HRC | — |
As-quenched | Intermediate condition only — boron gives near-full martensite in sections up to ~25 mm; must be tempered immediately. | 1,700 | 2,200 | 1 | 62 HRC | 7 % IACS |
What is 15B62 QT 45-50 HRC?
15B62 QT 45-50 HRC is 15B62 heat treated to QT 45-50 HRC — classic spring condition — highest usable elastic limit for coil and leaf springs, spring clips and track components. 15B62 QT 45-50 HRC has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,620 MPa (235 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi). 15B62 QT 45-50 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). HR is the default condition FabDigit quotes; QT 45-50 HRC is available on request or by drawing note.
Advantages
- High strength — 1,450 MPa (210 ksi), better than 97% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Low fracture toughness — 52 MPa·√m (47.3 ksi·√in), worse than 84% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
15B62 QT 45-50 HRC properties
Typical room-temperature values for 15B62 QT 45-50 HRC; 13 are specific to this condition. Other listed values are 15B62 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15B62 QT 45-50 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
15B62 QT 45-50 HRC has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,620 MPa (235 ksi) — stronger than 97% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
15B62 QT 45-50 HRC is rated for continuous service to 250°C (482 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
15B62 QT 45-50 HRC 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 15B62 QT 45-50 HRC takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 35%.
Manufacturability7
15B62 QT 45-50 HRC's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (20/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15B62 QT 45-50 HRC
Is 15B62 easy to machine?
Machine in the spheroidise-annealed condition with carbide tooling and rigid setups; above ~40 HRC switch to grinding, CBN or EDM.
Can 15B62 be welded?
Effectively unweldable as a structural joint — 0.60 % C plus boron gives crack-prone martensite; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and immediate stress relief/temper.
Can 15B62 be formed, bent or molded?
Cold head or bend only in the annealed state with generous radii; otherwise hot form at 950–1150 °C and re-harden — do not austenitise above ~950 °C or boron hardenability drops.
What surface finishes work on 15B62?
Shot peen springs for fatigue life, then phosphate + oil, zinc or zinc-flake coating; bake at 190–220 °C within 4 h of electroplating to avoid hydrogen embrittlement.
15B62 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 15Bxx high-carbon grade | 0.54 – 0.67 | 0.6 |
| Mn | 1 – 1.3 | 1.15 |
| Si | 0.15 – 0.35 | 0.25 |
| Bhardenability booster; requires Ti/Al to fix free nitrogen | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.03 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
15B62 QT 45-50 HRC — frequently asked
What is 15B62 QT 45-50 HRC used for?
15B62 QT 45-50 HRC is typically used for leaf springs, heavy fasteners and washers. In short: highest-carbon boron grade here; spring-capable through-hardening steel; lowest formability, 30/100.
What is the yield strength of 15B62 QT 45-50 HRC?
15B62 QT 45-50 HRC has a typical yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,620 MPa (235 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 15B62 QT 45-50 HRC easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in the spheroidise-annealed condition with carbide tooling and rigid setups; above ~40 HRC switch to grinding, CBN or EDM.
Can 15B62 QT 45-50 HRC be welded?
Not readily — weldability is rated poor (20/100). Effectively unweldable as a structural joint — 0.60 % C plus boron gives crack-prone martensite; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and immediate stress relief/temper.
What surface finishes work on 15B62 QT 45-50 HRC?
Shot peen springs for fatigue life, then phosphate + oil, zinc or zinc-flake coating; bake at 190–220 °C within 4 h of electroplating to avoid hydrogen embrittlement.
Can 15B62 QT 45-50 HRC be formed, bent or molded?
Cold head or bend only in the annealed state with generous radii; otherwise hot form at 950–1150 °C and re-harden — do not austenitise above ~950 °C or boron hardenability drops.
What is the maximum service temperature of 15B62 QT 45-50 HRC?
15B62 QT 45-50 HRC is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15B62-HR and 15B62-AQ?
HR is the default condition — standard mill supply condition for bar and coil that will be formed and then quenched and tempered by the part maker. AQ: intermediate condition only — boron gives near-full martensite in sections up to ~25 mm; must be tempered immediately. Yield strength is 520 MPa in HR versus 1,700 MPa in AQ.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J403 / J1268 — Carbon and Alloy Steel Chemical Compositions and Hardenability Bands — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4 — Heat Treating (boron steel hardenability) — ASM International (1991)
- ASM Handbook Vol. 16 — Machining — ASM International (1989)
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.