Steel ZG42CrMo QT-240-280HB
Hardness band · default condition
Standard supply condition for gear blanks, ring gears and heavy machine castings needing balanced strength and toughness.
Values for the QT-240-280HB condition
Other ZG42CrMo tempers and conditions
ZG42CrMo is listed in 10 conditions; see the grade overview at ZG42CrMo.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for heavy rough machining or to relieve casting stresses before final quench and temper. | 380 | 650 | 18 | 11 HRC | 7.9 % IACS |
As fabricated | Raw casting before heat treatment; used only for rough-machining stock or parts to be treated later. | 420 | 720 | 7 | 20 HRC | 7.8 % IACS |
Normalized | Grain refinement of the cast structure; intermediate strength without the cost of quenching large sections. | 500 | 830 | 10 | 23 HRC | 7.8 % IACS |
Normalized and tempered | Economical route for very heavy or complex castings where through-quenching is impractical. | 530 | 790 | 13 | 21 HRC | 7.8 % IACS |
quenched and high-temperature tempered (soft) | Pick when toughness and machinability matter more than strength, or when the part is later surface hardened elsewhere. | 560 | 750 | 17 | 19 HRC | 7.8 % IACS |
Stress relieved | Sub-critical soak after weld repair or heavy roughing to stabilise dimensions without changing hardness much. | 650 | 860 | 14 | 25 HRC | 7.8 % IACS |
QT-240-280HBDefaultThis page quenched and tempered (standard ) | Standard supply condition for gear blanks, ring gears and heavy machine castings needing balanced strength and toughness. | 680 | 880 | 13 | 26 HRC | — |
Q&T + induction/flame surface hardened | Tough Q&T core with a 50–56 HRC hardened skin on gear teeth, journals or track surfaces. | 680 | 880 | 12 | 54 HRC | 7.8 % IACS |
quenched and tempered (high strength) | Chosen for higher contact/bending load capacity in gear rims and rolls where some ductility can be traded away. | 780 | 980 | 11 | 31 HRC | — |
quenched and low-temperature tempered | Maximum through-hardness for wear-loaded castings; impact toughness and weld repairability become marginal. | 900 | 1,100 | 8 | 36 HRC | — |
What is ZG42CrMo QT-240-280HB?
ZG42CrMo QT-240-280HB is ZG42CrMo heat treated to QT-240-280HB — standard supply condition for gear blanks, ring gears and heavy machine castings needing balanced strength and toughness. ZG42CrMo QT-240-280HB has a yield strength of 680 MPa (98.6 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 80% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi). ZG42CrMo QT-240-280HB 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).
Advantages
- High strength — 680 MPa (98.6 ksi), better than 80% of steel grades
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
ZG42CrMo QT-240-280HB properties
Typical room-temperature values for ZG42CrMo QT-240-280HB; 12 are specific to this condition. Other listed values are ZG42CrMo reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
ZG42CrMo QT-240-280HB 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
ZG42CrMo QT-240-280HB has a yield strength of 680 MPa (98.6 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 80% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
ZG42CrMo QT-240-280HB is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical2
ZG42CrMo QT-240-280HB has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of ZG42CrMo QT-240-280HB takes about 24 MJ of energy and emits 2 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 75%.
Manufacturability8
ZG42CrMo QT-240-280HB's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (30/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZG42CrMo QT-240-280HB
Is ZG42CrMo easy to machine?
Machine in annealed or 200–280 HB Q&T condition with rigid setups, coated carbide and moderate speeds; expect abrasive scale and sand inclusions on as-cast skin — take a heavy first cut.
Can ZG42CrMo be welded?
Weldable only with care: preheat 250–350 °C, low-hydrogen or matching Cr-Mo consumables, maintain interpass temperature and follow with 600–650 °C PWHT to avoid cold cracking.
Can ZG42CrMo be formed, bent or molded?
Sand or investment cast with generous fillets, chills and risers on heavy sections; alloy is hot-tear sensitive and needs homogenising/normalising to break down the as-cast dendritic structure.
What surface finishes work on ZG42CrMo?
No anodizing; use shot blast plus paint, phosphate, black oxide, zinc or hard-chrome plating, and induction hardening plus grinding on wear surfaces.
ZG42CrMo 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 |
|---|---|---|
| Ccast equivalent of 42CrMo | 0.38 – 0.45 | 0.42 |
| Si | 0.2 – 0.6 | 0.4 |
| Mn | 0.5 – 1 | 0.75 |
| Cr | 0.8 – 1.2 | 1 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual, often restricted | ≤ 0.4 | — |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Fe | balance | — |
ZG42CrMo QT-240-280HB — frequently asked
What is ZG42CrMo QT-240-280HB used for?
ZG42CrMo QT-240-280HB is typically used for gears, crankshaft supports and high-strength machine bases. In short: highest strength Cr-Mo casting; cast equivalent of 42CrMo; deep-hardening cast steel.
What is the yield strength of ZG42CrMo QT-240-280HB?
ZG42CrMo QT-240-280HB has a typical yield strength of 680 MPa (98.6 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 80% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is ZG42CrMo QT-240-280HB easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in annealed or 200–280 HB Q&T condition with rigid setups, coated carbide and moderate speeds; expect abrasive scale and sand inclusions on as-cast skin — take a heavy first cut.
Can ZG42CrMo QT-240-280HB be welded?
Not readily — weldability is rated poor (30/100). Weldable only with care: preheat 250–350 °C, low-hydrogen or matching Cr-Mo consumables, maintain interpass temperature and follow with 600–650 °C PWHT to avoid cold cracking.
What surface finishes work on ZG42CrMo QT-240-280HB?
No anodizing; use shot blast plus paint, phosphate, black oxide, zinc or hard-chrome plating, and induction hardening plus grinding on wear surfaces.
Can ZG42CrMo QT-240-280HB be formed, bent or molded?
Sand or investment cast with generous fillets, chills and risers on heavy sections; alloy is hot-tear sensitive and needs homogenising/normalising to break down the as-cast dendritic structure.
What is the maximum service temperature of ZG42CrMo QT-240-280HB?
ZG42CrMo QT-240-280HB 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 ZG42CrMo QT-240-280HB and ZG42CrMo-A?
QT-240-280HB is the default condition — standard supply condition for gear blanks, ring gears and heavy machine castings needing balanced strength and toughness. A: softest condition for heavy rough machining or to relieve casting stresses before final quench and temper. Yield strength is 680 MPa in QT-240-280HB versus 380 MPa in A.
Sources
- GB/T 3077 (42CrMo wrought reference) — SAC (2015)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys (Cast Low-Alloy Steels) — 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.