Steel ZG42CrMo-SR (Stress relieved)
Heat-treated state
Sub-critical soak after weld repair or heavy roughing to stabilise dimensions without changing hardness much.
Values for the SR 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 |
SRThis page 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-240-280HBDefault 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-SR?
ZG42CrMo-SR is ZG42CrMo heat treated to SR — sub-critical soak after weld repair or heavy roughing to stabilise dimensions without changing hardness much. ZG42CrMo-SR has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 79% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi). ZG42CrMo-SR 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). QT-240-280HB is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- High strength — 650 MPa (94.3 ksi), better than 79% of steel grades
Limitations
- Limited formability — 9/100, worse than 97% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
ZG42CrMo-SR properties
Typical room-temperature values for ZG42CrMo-SR; 22 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-SR 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-SR has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 79% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
ZG42CrMo-SR 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-SR 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-SR 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-SR's machinability is fair (44/100, worse than 71% of steel grades); weldability poor (30/100); formability not recommended (9/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZG42CrMo-SR
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-SR — frequently asked
What is ZG42CrMo-SR used for?
ZG42CrMo-SR 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-SR?
ZG42CrMo-SR has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is ZG42CrMo-SR easy to machine?
Not especially — machinability is rated fair (44/100, worse than 71% 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-SR 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-SR?
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-SR 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-SR?
ZG42CrMo-SR 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.