Steel 50B50-QT315
Heat-treated state
EN 50B50 · UNS G50501
High-hardness spring/wear condition with slightly improved ductility over 205 °C temper.
Values for the QT315 condition
Other 50B50 tempers and conditions
50B50 is listed in 13 conditions; see the grade overview at 50B50.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Best condition for cold heading, thread rolling and deep machining of this 0.50 %C grade. | 350 | 640 | 25 | 180 HB | 8 % IACS |
ADefault Solution annealed | Standard stocking condition: softest state for machining, cold forming and subsequent hardening. | 380 | 700 | 21 | 197 HB | — |
Hot rolled | Cheapest mill condition for parts that will be re-heat-treated after forming or machining. | 460 | 800 | 16 | 22 HRC | 8 % IACS |
Normalized | Uniform fine-grain structure before hardening, or a moderate-strength as-supplied condition. | 550 | 900 | 19 | 26 HRC | — |
Cold drawn | Close tolerance, bright finish and higher yield for machined pins and shafts not needing full hardening. | 660 | 790 | 12 | 20 HRC | 8 % IACS |
oil quenched, tempered 650 °C | Softest Q&T condition — best ductility and impact energy for heavily loaded but shock-prone parts. | 760 | 870 | 20 | 27 HRC | — |
oil quenched, tempered 540 °C | Tough machine-part temper (~35 HRC) for shafts, pins and links loaded in shock. | 1,060 | 1,150 | 15 | 35 HRC | — |
hardness-specified quench & temper | Purchase-by-hardness condition for gears, links and moderate-wear components needing residual toughness. | 1,180 | 1,300 | 13 | 40 HRC | — |
oil quenched, tempered 425 °C | Classic leaf-spring / high-strength fastener temper balancing strength and fatigue life. | 1,350 | 1,450 | 11 | 43 HRC | — |
hardness-specified quench & temper | Typical spring and abrasion-service hardness band for 50B50 plate and bar. | 1,420 | 1,570 | 10 | 46 HRC | — |
QT315This page oil quenched, tempered 315 °C | High-hardness spring/wear condition with slightly improved ductility over 205 °C temper. | 1,570 | 1,740 | 9 | 49 HRC | — |
hardness-specified quench & temper | Maximum-wear condition for plow shares, sweeps, cutting edges and wear strips; avoid impact/notches. | 1,650 | 1,880 | 7 | 52 HRC | — |
oil quenched, tempered 205 °C | Maximum hardness and wear resistance for tillage tools and wear plate; very low toughness. | 1,700 | 1,930 | 6 | 53 HRC | — |
What is 50B50-QT315?
50B50-QT315 is 50B50 heat treated to QT315 — high-hardness spring/wear condition with slightly improved ductility over 205 °C temper. 50B50-QT315 has a yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,740 MPa (252 ksi) — stronger than 98% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi). 50B50-QT315 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). A is the default condition FabDigit quotes; QT315 is available on request or by drawing note.
Advantages
- High strength — 1,570 MPa (228 ksi), better than 98% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Low fracture toughness — 42 MPa·√m (38.2 ksi·√in), worse than 92% of steel grades
- Limited service temperature — 260°C (500 °F), worse than 82% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
50B50-QT315 properties
Typical room-temperature values for 50B50-QT315; 12 are specific to this condition. Other listed values are 50B50 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
50B50-QT315 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).
Mechanical16
50B50-QT315 has a yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,740 MPa (252 ksi) — stronger than 98% of steel grades. Elongation at break is 9% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
50B50-QT315 is rated for continuous service to 260°C (500 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
50B50-QT315 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 50B50-QT315 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
50B50-QT315's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (25/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 50B50-QT315
Is 50B50 easy to machine?
Machine in the annealed or spheroidized state (~60 % of 1212) with rigid setups and coated carbide; above 45 HRC switch to CBN/grinding.
Can 50B50 be welded?
Poor weldability — CE ≈ 0.75; use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate PWHT, and expect a hard, crack-prone HAZ.
Can 50B50 be formed, bent or molded?
Cold form or coil only when annealed/spheroidized with generous bend radii; hot work at 1050–1200 °C, austenitize 830–860 °C (do not overheat — boron effect is lost) and quench in oil.
What surface finishes work on 50B50?
No natural corrosion protection: use phosphate-and-oil, black oxide, paint or zinc; bake plated parts above 40 HRC at 190–220 °C to relieve hydrogen embrittlement.
50B50 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 | 0.48 – 0.53 | 0.5 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.4 – 0.6 | 0.5 |
| Bboron addition for hardenability; requires fully killed, Ti/Al-treated steel | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
50B50-QT315 — frequently asked
What is 50B50-QT315 used for?
50B50-QT315 is typically used for leaf springs, high-strength bolts and wear plates. In short: boron-boosted hardenability; through-hardening spring steel; hardness bands to 55 HRC.
What is the yield strength of 50B50-QT315?
50B50-QT315 has a typical yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,740 MPa (252 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is 50B50-QT315 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine in the annealed or spheroidized state (~60 % of 1212) with rigid setups and coated carbide; above 45 HRC switch to CBN/grinding.
Can 50B50-QT315 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability — CE ≈ 0.75; use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate PWHT, and expect a hard, crack-prone HAZ.
What surface finishes work on 50B50-QT315?
No natural corrosion protection: use phosphate-and-oil, black oxide, paint or zinc; bake plated parts above 40 HRC at 190–220 °C to relieve hydrogen embrittlement.
Can 50B50-QT315 be formed, bent or molded?
Cold form or coil only when annealed/spheroidized with generous bend radii; hot work at 1050–1200 °C, austenitize 830–860 °C (do not overheat — boron effect is lost) and quench in oil.
What is the maximum service temperature of 50B50-QT315?
50B50-QT315 is rated for continuous use to about 260°C (500 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50B50-A and 50B50-QT205?
A is the default condition — standard stocking condition: softest state for machining, cold forming and subsequent hardening. QT205: maximum hardness and wear resistance for tillage tools and wear plate; very low toughness. Yield strength is 380 MPa in A versus 1,700 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Boron H-Steels — SAE International (2018)
- 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.4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
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.