Steel 15B30 · hardness band
Steel 15B30 QT 45-50 HRC
Properties of the QT 45-50 HRC condition, compared with the other 15B30 tempers.
Highest practical hardness for this carbon level — wear plates, harrow discs, cutting edges where impact loads are modest.
What is 15B30 QT 45-50 HRC?
15B30 QT 45-50 HRC is 15B30 heat treated to QT 45-50 HRC — highest practical hardness for this carbon level — wear plates, harrow discs, cutting edges where impact loads are modest. 15B30 QT 45-50 HRC has a yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi). 15B30 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 — 1,330 MPa (193 ksi), better than 95% of steel grades
Limitations
- Limited formability — 8/100, worse than 97% of steel grades
- Difficult to machine — 22/100, worse than 96% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
15B30 QT 45-50 HRC properties
Typical room-temperature values for 15B30 QT 45-50 HRC — 15 properties are specific to this condition; the rest are grade-level values shared by every 15B30 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
15B30 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).
Mechanical13
15B30 QT 45-50 HRC has a yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
15B30 QT 45-50 HRC is rated for continuous service to 250°C (482 °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
15B30 QT 45-50 HRC conducts electricity at 9 % IACS, better than 70% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 15B30 QT 45-50 HRC takes about 24 MJ of energy and emits 2 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 30%.
Manufacturability7
15B30 QT 45-50 HRC's machinability is poor (22/100, worse than 96% of steel grades); weldability poor (20/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 15B30 tempers and conditions
15B30 is also supplied in 7 other conditions. The full side-by-side table is on the 15B30 overview.
- HRDefaultDefault stock condition for bar, coil and plate that will be formed/machined and then quench-and-tempered.380 MPa yield · 179 HB
- QT 45-50 HRCHighest practical hardness for this carbon level — wear plates, harrow discs, cutting edges where impact loads are modest.1,330 MPa yield · 48 HRC
- QT 38-42 HRCBalance of hardness and toughness typical of track links, tillage tools and grade-8 style fasteners.1,100 MPa yield · 40 HRC
- QT 28-32 HRCTough, moderately hard condition for shafts, links and structural parts needing impact resistance.800 MPa yield · 30 HRC
- CDChoose for straight, size-accurate bright bar with higher as-supplied yield strength for machined parts.630 MPa yield · 217 HB
- CRPick for tighter thickness tolerance and better surface on strip that is blanked then heat treated.580 MPa yield · 207 HB
- NormalizedPick to homogenize forged or hot-rolled structure and get uniform mid-range strength before final machining.390 MPa yield · 179 HB
- AnnealedUse when maximum cold formability, deep drawing or heavy machining precedes final hardening.320 MPa yield · 156 HB
Working with 15B30 QT 45-50 HRC
Is 15B30 easy to machine?
Machine in the annealed or hot-rolled state (~60% of AISI 1212); carbide tooling and rigid setups above 30 HRC, and expect rapid tool wear beyond 40 HRC.
Can 15B30 be welded?
Weldability is limited by high Mn plus boron — use low-hydrogen consumables, 150–250 °C preheat, controlled interpass and post-weld tempering to avoid HAZ martensite cracking.
Can 15B30 be formed, bent or molded?
Hot forge 1100–1200 °C; cold bending and roll forming are practical only in the annealed/spheroidized condition with generous bend radii, then quench and temper.
What surface finishes work on 15B30?
No natural corrosion protection — phosphate + oil, black oxide, paint/e-coat, zinc or Zn-Ni plating; bake after plating to relieve hydrogen embrittlement risk above 35 HRC.
15B30 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 | 0.28 – 0.33 | 0.3 |
| Mnhigh-Mn 15xx series | 1.2 – 1.5 | 1.35 |
| Sitypical killed-steel range (SAE J403 heat analysis) | 0.15 – 0.3 | 0.22 |
| P | ≤ 0.03 | — |
| S | ≤ 0.05 | — |
| Bboron addition for hardenability; requires Ti/Al N-control | 5×10⁻⁴ – 0 | 0 |
| Fe | balance | — |
15B30 QT 45-50 HRC — frequently asked
What is 15B30 QT 45-50 HRC used for?
15B30 QT 45-50 HRC is typically used for bolts, threaded fasteners and inserts. In short: hot-stamping boron steel.
What is the yield strength of 15B30 QT 45-50 HRC?
15B30 QT 45-50 HRC has a typical yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 15B30 QT 45-50 HRC easy to machine?
Not especially — machinability is rated poor (22/100, worse than 96% of steel grades). Machine in the annealed or hot-rolled state (~60% of AISI 1212); carbide tooling and rigid setups above 30 HRC, and expect rapid tool wear beyond 40 HRC.
Can 15B30 QT 45-50 HRC be welded?
Not readily — weldability is rated poor (20/100). Weldability is limited by high Mn plus boron — use low-hydrogen consumables, 150–250 °C preheat, controlled interpass and post-weld tempering to avoid HAZ martensite cracking.
What surface finishes work on 15B30 QT 45-50 HRC?
No natural corrosion protection — phosphate + oil, black oxide, paint/e-coat, zinc or Zn-Ni plating; bake after plating to relieve hydrogen embrittlement risk above 35 HRC.
Can 15B30 QT 45-50 HRC be formed, bent or molded?
Hot forge 1100–1200 °C; cold bending and roll forming are practical only in the annealed/spheroidized condition with generous bend radii, then quench and temper.
What is the maximum service temperature of 15B30 QT 45-50 HRC?
15B30 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 15B30-HR and 15B30-CD?
HR is the default condition — default stock condition for bar, coil and plate that will be formed/machined and then quench-and-tempered. CD: choose for straight, size-accurate bright bar with higher as-supplied yield strength for machined parts. Yield strength is 380 MPa in HR versus 630 MPa in CD.
Can FabDigit make parts in 15B30 QT 45-50 HRC?
Yes — 15B30 QT 45-50 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
- SAE J403 — Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- SAE J404 / J1268 — Alloy & Hardenability of Boron Steels — SAE International (2019)
- 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)
- ASM Handbook Vol. 16: Machining — ASM International (1989)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
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.