Steel 50B44-QT540
Heat-treated state
EN 50B44 · UNS G50441
QT540 = q&T 540 °C
General machinery condition for shafts, links and high-strength fasteners needing toughness.
Values for the QT540 condition
Other 50B44 tempers and conditions
50B44 is listed in 11 conditions; see the grade overview at 50B44.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick for cold heading, deep drawing or heavy cold forming of blades and fasteners. | 350 | 600 | 25 | 174 HB | 8 % IACS |
ADefault Solution annealed | Standard stocking condition for machining, cold forming and blanking before hardening. | 380 | 640 | 22 | 187 HB | — |
Hot rolled | Cheapest mill condition for parts that will be re-austenitized and quenched anyway. | 430 | 725 | 16 | 207 HB | — |
Normalized | Uniform fine grain and predictable response before hardening; also used as a supply condition for forgings. | 520 | 840 | 20 | 24 HRC | — |
Cold drawn | Tighter tolerance and better surface for machined shafts and pins; higher strength, lower ductility. | 640 | 760 | 12 | 17 HRC | 8 % IACS |
Q&T 650 °C | Softest quenched-and-tempered condition — maximum ductility and machinability, still through-hardened structure. | 830 | 950 | 20 | 30 HRC | — |
QT540This page Q&T 540 °C | General machinery condition for shafts, links and high-strength fasteners needing toughness. | 1,100 | 1,210 | 15 | 38 HRC | — |
Q&T 425 °C | Balance of strength and shock resistance for plow shares, mower blades and track components. | 1,380 | 1,500 | 12 | 44 HRC | — |
commercial hardened wear-part condition | The hardness band most agricultural-tool suppliers ship 50B44 strip/blades in; buy this when hardness, not a tempering recipe, is specified. | 1,450 | 1,620 | 11 | 47 HRC | — |
Q&T 315 °C | Standard wear-part condition: still very hard but with usable impact resistance. | 1,580 | 1,790 | 10 | 50 HRC | — |
Q&T 205 °C | Maximum hardness and wear resistance for tillage points and cutting edges; lowest toughness. | 1,650 | 2,000 | 9 | 55 HRC | — |
What is 50B44-QT540?
50B44-QT540 is 50B44 heat treated to QT540 — general machinery condition for shafts, links and high-strength fasteners needing toughness. 50B44-QT540 has a yield strength of 1,100 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 50B44-QT540 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; QT540 is available on request or by drawing note.
Advantages
- High strength — 1,100 MPa (160 ksi), better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Difficult to machine — 38/100, worse than 80% of steel grades
50B44-QT540 properties
Typical room-temperature values for 50B44-QT540; 14 are specific to this condition. Other listed values are 50B44 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
50B44-QT540 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
50B44-QT540 has a yield strength of 1,100 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
50B44-QT540 is rated for continuous service to 425°C (797 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
50B44-QT540 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 50B44-QT540 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
50B44-QT540's machinability is fair (38/100, worse than 80% of steel grades); weldability poor (30/100); formability fair (45/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 50B44-QT540
Is 50B44 easy to machine?
Machine in the annealed or spheroidized condition (~62 % of 1212) with carbide at moderate speed; above 45 HRC switch to grinding, CBN or hard turning.
Can 50B44 be welded?
Poor weldability — boron plus 0.45 % C gives high carbon equivalent; use low-hydrogen consumables, 200–300 °C preheat, controlled interpass and immediate temper or post-weld heat treatment.
Can 50B44 be formed, bent or molded?
Cold form, blank, roll or press only in the annealed/spheroidized state; hot forge 1150–1200 °C, finish above 900 °C, then normalize or anneal to restore uniform grain before hardening.
What surface finishes work on 50B44?
Austenitize 830–860 °C, quench in oil (thin sections) or water/polymer, temper 175–650 °C; protect with paint, phosphate-and-oil, black oxide or zinc — avoid acid pickling of hardened parts to prevent hydrogen embrittlement.
50B44 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 | 0.43 – 0.48 | 0.46 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.4 – 0.6 | 0.5 |
| Bhardenability boron; requires Ti/Al to fix nitrogen | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
50B44-QT540 — frequently asked
What is 50B44-QT540 used for?
50B44-QT540 is typically used for springs, high-strength bolts and wear parts. In short: deep hardening, low alloy cost; chromium-boron spring steel; anneal before cold forming.
What is the yield strength of 50B44-QT540?
50B44-QT540 has a typical yield strength of 1,100 MPa (160 ksi) and a tensile strength of 1,210 MPa (175 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 50B44-QT540 easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Machine in the annealed or spheroidized condition (~62 % of 1212) with carbide at moderate speed; above 45 HRC switch to grinding, CBN or hard turning.
Can 50B44-QT540 be welded?
Not readily — weldability is rated poor (30/100). Poor weldability — boron plus 0.45 % C gives high carbon equivalent; use low-hydrogen consumables, 200–300 °C preheat, controlled interpass and immediate temper or post-weld heat treatment.
What surface finishes work on 50B44-QT540?
Austenitize 830–860 °C, quench in oil (thin sections) or water/polymer, temper 175–650 °C; protect with paint, phosphate-and-oil, black oxide or zinc — avoid acid pickling of hardened parts to prevent hydrogen embrittlement.
Can 50B44-QT540 be formed, bent or molded?
Cold form, blank, roll or press only in the annealed/spheroidized state; hot forge 1150–1200 °C, finish above 900 °C, then normalize or anneal to restore uniform grain before hardening.
What is the maximum service temperature of 50B44-QT540?
50B44-QT540 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50B44-A and 50B44-QT205?
A is the default condition — standard stocking condition for machining, cold forming and blanking before hardening. QT205: maximum hardness and wear resistance for tillage points and cutting edges; lowest toughness. Yield strength is 380 MPa in A versus 1,650 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 — ASTM International (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (boron steels, hardenability) — ASM International (1991)
- 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.