Steel 50B46-QT315
Heat-treated state
EN 50B46 · UNS G50461
QT315 = q&T 315 °C
High-strength spring/tool condition; keep out of the 260–370 °C temper-embrittlement window if impact matters.
Values for the QT315 condition
Other 50B46 tempers and conditions
50B46 is listed in 11 conditions; see the grade overview at 50B46.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Pick for cold-headed bolts and screws: softest, most ductile carbide morphology. | 390 | 620 | 25 | 174 HB | 8.5 % IACS |
ADefault Solution annealed | Standard stocked soft condition for machining, cold forming and subsequent quench-and-temper. | 420 | 700 | 20 | 197 HB | — |
Hot rolled | Cheapest mill condition for bar/coil that will be re-heat-treated by the fabricator. | 470 | 800 | 16 | 20 HRC | 8 % IACS |
Normalized | Use to homogenize grain structure after forging before final hardening; note boron steels air-harden more than plain carbon steels. | 560 | 900 | 15 | 26 HRC | 8 % IACS |
Cold drawn | Choose for close-tolerance, bright-finish bar going straight to machining without further heat treatment. | 700 | 830 | 12 | 23 HRC | 8 % IACS |
Q&T 650 °C | Toughest quenched-and-tempered option (~950 MPa) where impact and machinability outrank strength. | 860 | 960 | 20 | 29 HRC | — |
Q&T 540 °C | General machined-component condition (~1150 MPa) with good ductility and impact. | 1,070 | 1,170 | 16 | 36 HRC | — |
Austempered | Use for thin springs, clips and tool blades where distortion and quench cracking must be minimized at high hardness. | 1,200 | 1,450 | 12 | 44 HRC | 7.5 % IACS |
Q&T 425 °C | Common bolt/spring balance of strength and toughness around 1400 MPa. | 1,310 | 1,430 | 13 | 44 HRC | — |
QT315This page Q&T 315 °C | High-strength spring/tool condition; keep out of the 260–370 °C temper-embrittlement window if impact matters. | 1,520 | 1,720 | 10 | 50 HRC | — |
Q&T 205 °C | Maximum hardness and wear resistance for tillage tools and springs; very low toughness, avoid stress raisers. | 1,590 | 1,960 | 9 | 54 HRC | — |
What is 50B46-QT315?
50B46-QT315 is 50B46 heat treated to QT315 — high-strength spring/tool condition; keep out of the 260–370 °C temper-embrittlement window if impact matters. 50B46-QT315 has a yield strength of 1,520 MPa (220 ksi) and a tensile strength of 1,720 MPa (249 ksi) — stronger than 97% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi). 50B46-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 — 1,520 MPa (220 ksi), better than 97% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
50B46-QT315 properties
Typical room-temperature values for 50B46-QT315; 12 are specific to this condition. Other listed values are 50B46 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
50B46-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
50B46-QT315 has a yield strength of 1,520 MPa (220 ksi) and a tensile strength of 1,720 MPa (249 ksi) — stronger than 97% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
50B46-QT315 is rated for continuous service to 250°C (482 °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 µm/m·K (6.67 µin/in·°F).
Electrical3
50B46-QT315 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 50B46-QT315 takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability8
50B46-QT315's machinability is good (55/100, better than 62% of steel grades); weldability poor (30/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 50B46-QT315
Is 50B46 easy to machine?
Machine in the annealed or spheroidized condition (~60 % of 1212); above 40 HRC switch to carbide/CBN, rigid setups and low feeds, or grind.
Can 50B46 be welded?
Poor weldability — carbon equivalent ≈0.75; if unavoidable use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate post-weld temper.
Can 50B46 be formed, bent or molded?
Cold-head and cold-form only in spheroidize-annealed wire; hot forge 1100–1200 °C and normalize afterwards, then oil quench from 830–860 °C and temper to the target hardness.
What surface finishes work on 50B46?
No inherent corrosion resistance — specify zinc, zinc-nickel or Zn-flake coating, phosphate+oil or black oxide; bake plated parts ≥190 °C/4 h to relieve hydrogen when above ~1000 MPa.
50B46 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 | 0.44 – 0.49 | 0.46 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| CrSAE 50B46 chromium range (some sources/orders to 0.40–0.60 for 5046-type) | 0.2 – 0.35 | 0.28 |
| Bboron addition for hardenability; effective B requires Ti/Al N-fixing | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
50B46-QT315 — frequently asked
What is 50B46-QT315 used for?
50B46-QT315 is typically used for fasteners, springs and clutch parts. In short: through-hardening fastener steel; cheaper than 5146 equivalents; coating required for corrosion.
What is the yield strength of 50B46-QT315?
50B46-QT315 has a typical yield strength of 1,520 MPa (220 ksi) and a tensile strength of 1,720 MPa (249 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 50B46-QT315 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed or spheroidized condition (~60 % of 1212); above 40 HRC switch to carbide/CBN, rigid setups and low feeds, or grind.
Can 50B46-QT315 be welded?
Not readily — weldability is rated poor (30/100). Poor weldability — carbon equivalent ≈0.75; if unavoidable use low-hydrogen consumables, 250–350 °C preheat, controlled interpass and immediate post-weld temper.
What surface finishes work on 50B46-QT315?
No inherent corrosion resistance — specify zinc, zinc-nickel or Zn-flake coating, phosphate+oil or black oxide; bake plated parts ≥190 °C/4 h to relieve hydrogen when above ~1000 MPa.
Can 50B46-QT315 be formed, bent or molded?
Cold-head and cold-form only in spheroidize-annealed wire; hot forge 1100–1200 °C and normalize afterwards, then oil quench from 830–860 °C and temper to the target hardness.
What is the maximum service temperature of 50B46-QT315?
50B46-QT315 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 50B46-A and 50B46-QT205?
A is the default condition — standard stocked soft condition for machining, cold forming and subsequent quench-and-temper. QT205: maximum hardness and wear resistance for tillage tools and springs; very low toughness, avoid stress raisers. Yield strength is 420 MPa in A versus 1,590 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — 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)
- Machinery's Handbook, 31st ed. — Industrial Press (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.