Steel 4042-HR vs 4042 QT-40-45HRC
Steel · 4042 temper comparison
4042-HR and 4042 QT-40-45HRC are two conditions of the same steel grade, 4042: HR (hot rolled) versus QT-40-45HRC. The chemistry is identical, so every difference below comes from the condition. 4042 QT-40-45HRC is the stronger of the two: yield strength 1,250 MPa (181 ksi) against 415 MPa (60.2 ksi) for 4042-HR, about 3.0 times as much; tensile strength follows at 1,380 MPa (200 ksi) vs 660 MPa (95.7 ksi). In exchange, 4042-HR is the more ductile: elongation 20% versus 12% for 4042 QT-40-45HRC, and 4042 QT-40-45HRC is harder (401 HB vs 197 HB). 4042-HR runs hotter in service (400°C vs 300°C continuous).
4042-HRChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
4042 QT-40-45HRCChoose it when strength drives the design.
4042-HR vs 4042 QT-40-45HRC: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Shear Strength 400 MPa58 ksi
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 42.6 W/m·K24.6 BTU/hr·ft·°F · Specific Heat Capacity 475 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.2 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 40 / 100 · Brazeability / Solderability 60 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 26 MJ/kg11,178 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg · Embodied Water 60 L/kg7.2 gal/lb · Typical Recycled Content 30%
Strength versus weight
Yield strength against density for every steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
4042-HR vs 4042 QT-40-45HRC — frequently asked
Is 4042 QT-40-45HRC stronger than 4042-HR?
Yes. 4042 QT-40-45HRC has a typical yield strength of 1,250 MPa (181 ksi) against 415 MPa (60.2 ksi) for 4042-HR — about 3.0 times as much. Tensile strength is 1,380 MPa (200 ksi) vs 660 MPa (95.7 ksi).
Which condition does FabDigit quote by default, HR or QT-40-45HRC?
A is the default 4042 condition in the FabDigit quote flow (neither HR nor QT-40-45HRC). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, 4042-HR or 4042 QT-40-45HRC?
4042 QT-40-45HRC, by a small margin. Both rate good for machinability — 60/100 against 55/100 for 4042-HR.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4042-HR and 4042 QT-40-45HRC side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.