Steel 50# · hardness band
Steel 50# QT 38-42 HRC
Properties of the QT 38-42 HRC condition, compared with the other 50# tempers.
High-strength condition for spring washers, wear plates and highly loaded pins; toughness and machinability drop sharply.
What is 50# QT 38-42 HRC?
50# QT 38-42 HRC is 50# heat treated to QT 38-42 HRC — high-strength condition for spring washers, wear plates and highly loaded pins; toughness and machinability drop sharply. 50# QT 38-42 HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 93% of steel grades. Elongation at break is 10% and the elastic modulus is 207 GPa (30 Msi). 50# QT 38-42 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; QT 38-42 HRC is available on request or by drawing note.
Advantages
- High strength — 1,080 MPa (157 ksi), better than 93% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
50# QT 38-42 HRC properties
Typical room-temperature values for 50# QT 38-42 HRC — 11 properties are specific to this condition; the rest are grade-level values shared by every 50# temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
50# QT 38-42 HRC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
50# QT 38-42 HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 93% of steel grades. Elongation at break is 10% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
50# QT 38-42 HRC is rated for continuous service to 400°C (752 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
50# QT 38-42 HRC conducts electricity at 9.5 % IACS, better than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 50# QT 38-42 HRC takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
50# QT 38-42 HRC's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (15/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 50# tempers and conditions
50# is also supplied in 7 other conditions. The full side-by-side table is on the 50# overview.
- HRDefaultDefault stock condition for 50# round bar and plate; machined then heat treated by the user.400 MPa yield · 210 HB
- QT 38-42 HRCHigh-strength condition for spring washers, wear plates and highly loaded pins; toughness and machinability drop sharply.1,080 MPa yield · 40 HRC
- QT 28-32 HRCSpecify when a defined medium hardness is required for wear-loaded shafts and gears that still need machining.780 MPa yield · 30 HRC
- QTGeneral-purpose toughened condition for shafts, gear blanks and rolls needing strength with usable ductility.620 MPa yield · 25 HRC
- IHPick for gear teeth, spline and journal surfaces needing 50–58 HRC wear resistance with a tough tempered core.620 MPa yield · 55 HRC
- CDChoose for straight, close-tolerance bright bar with raised yield strength; low ductility and residual stress.600 MPa yield · 210 HB
- NStandard GB/T 699 reference condition — uniform fine pearlite, better strength and consistency than as-rolled.430 MPa yield · 217 HB
- ASoftest condition, used before heavy machining or cold forming of 50# stock.365 MPa yield · 190 HB
Working with 50# QT 38-42 HRC
Is 50# easy to machine?
Machine in annealed/normalized state at ~50 % of 1212 speeds; carbide tooling, positive rake, generous coolant — above 30 HRC use CBN/coated carbide and lower feeds.
Can 50# be welded?
Poor weldability at 0.50 % C: use low-hydrogen electrodes, 150–260 °C preheat, controlled interpass and 600 °C stress relief to avoid martensitic cracking in the HAZ.
Can 50# be formed, bent or molded?
Hot forge/roll at 1150–850 °C then normalize; cold bending only in annealed condition with generous radii (≥3 t).
What surface finishes work on 50#?
No anodizing — protect with phosphating + oil, blackening, zinc/chrome plating or paint; hardened surfaces grind and polish well but rust quickly unprotected.
50# 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 | 0.47 – 0.55 | 0.5 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Crresidual max | ≤ 0.25 | — |
| Niresidual max | ≤ 0.3 | — |
| Curesidual max | ≤ 0.25 | — |
| Fe | balance | — |
50# QT 38-42 HRC — frequently asked
What is 50# QT 38-42 HRC used for?
50# QT 38-42 HRC is typically used for shafts, cold work blanks and springs. In short: medium-carbon plate stock.
What is the yield strength of 50# QT 38-42 HRC?
50# QT 38-42 HRC has a typical yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 50# QT 38-42 HRC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine in annealed/normalized state at ~50 % of 1212 speeds; carbide tooling, positive rake, generous coolant — above 30 HRC use CBN/coated carbide and lower feeds.
Can 50# QT 38-42 HRC be welded?
Not readily — weldability is rated poor (15/100). Poor weldability at 0.50 % C: use low-hydrogen electrodes, 150–260 °C preheat, controlled interpass and 600 °C stress relief to avoid martensitic cracking in the HAZ.
What surface finishes work on 50# QT 38-42 HRC?
No anodizing — protect with phosphating + oil, blackening, zinc/chrome plating or paint; hardened surfaces grind and polish well but rust quickly unprotected.
Can 50# QT 38-42 HRC be formed, bent or molded?
Hot forge/roll at 1150–850 °C then normalize; cold bending only in annealed condition with generous radii (≥3 t).
What is the maximum service temperature of 50# QT 38-42 HRC?
50# QT 38-42 HRC is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50#-HR and 50#-QT?
HR is the default condition — default stock condition for 50# round bar and plate; machined then heat treated by the user. QT: general-purpose toughened condition for shafts, gear blanks and rolls needing strength with usable ductility. Yield strength is 400 MPa in HR versus 620 MPa in QT.
Can FabDigit make parts in 50# QT 38-42 HRC?
Yes — 50# QT 38-42 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
- GB/T 699 Quality carbon structural steels (grade 50) — SAC (2015)
- GB/T 702 Hot-rolled steel bars — dimensions and tolerances — SAC (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels (SAE 1050 data) — ASM International (1990)
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.