Steel GS-42CrMo4 QT 34-38 HRC
Hardness band
AISI/SAE 4140 · EN 1.7231 · GB ZG42CrMo
Choose when wear resistance and high yield strength dominate and reduced impact toughness is acceptable.
Values for the QT 34-38 HRC condition
Other GS-42CrMo4 tempers and conditions
GS-42CrMo4 is listed in 9 conditions; see the grade overview at GS-42CrMo4.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for maximum machinability of rough castings before final Q&T. | 390 | 660 | 16 | 200 HB | — |
Normalized | Refines the as-cast dendritic structure and gives uniform medium strength for lightly loaded castings. | 470 | 780 | 13 | 19 HRC | 8 % IACS |
As fabricated | Raw casting condition, only for non-critical parts or as the starting point before annealing/Q&T. | 480 | 800 | 8 | 24 HRC | 8 % IACS |
Normalized and tempered | Use for large-section castings where full quenching is impractical but stable strength and toughness are needed. | 540 | 820 | 13 | 22 HRC | 7.9 % IACS |
Stress relieved | Sub-critical treatment (typically below the tempering temperature) to relieve casting/weld-repair stresses without changing strength much. | 740 | 960 | 12 | 28 HRC | 7.8 % IACS |
+QTDefault Quenched and tempered | Standard supply condition: best strength/toughness balance for gears, housings and heavily loaded machine castings. | 760 | 980 | 11 | 29 HRC | — |
+QT + flame/induction hardened surface | Q&T core with a hardened running surface — for cast gear teeth, tracks and journals needing wear resistance. | 760 | 980 | 10 | 54 HRC | 7.5 % IACS |
tempered to medium hardness | Common ordered hardness band for shafts, hubs and gear blanks that must still be machined after heat treatment. | 800 | 1,000 | 11 | 30 HRC | — |
QT 34-38 HRCThis page tempered to high hardness | Choose when wear resistance and high yield strength dominate and reduced impact toughness is acceptable. | 950 | 1,150 | 8 | 36 HRC | — |
What is GS-42CrMo4 QT 34-38 HRC?
GS-42CrMo4 QT 34-38 HRC is GS-42CrMo4 heat treated to QT 34-38 HRC — choose when wear resistance and high yield strength dominate and reduced impact toughness is acceptable. GS-42CrMo4 QT 34-38 HRC has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi). GS-42CrMo4 QT 34-38 HRC 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 is the default condition FabDigit quotes; QT 34-38 HRC is available on request or by drawing note.
Advantages
- High strength — 950 MPa (138 ksi), better than 91% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
- Difficult to machine — 35/100, worse than 84% of steel grades
GS-42CrMo4 QT 34-38 HRC properties
Typical room-temperature values for GS-42CrMo4 QT 34-38 HRC; 12 are specific to this condition. Other listed values are GS-42CrMo4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
GS-42CrMo4 QT 34-38 HRC 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
GS-42CrMo4 QT 34-38 HRC has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 8% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
GS-42CrMo4 QT 34-38 HRC 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).
Electrical3
GS-42CrMo4 QT 34-38 HRC conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of GS-42CrMo4 QT 34-38 HRC takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 80%.
Manufacturability7
GS-42CrMo4 QT 34-38 HRC's machinability is fair (35/100, worse than 84% of steel grades); weldability fair (35/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with GS-42CrMo4 QT 34-38 HRC
Is GS-42CrMo4 easy to machine?
Rough-machine in the annealed state (≈200 HB); at 280–330 HB use rigid setups, coated carbide, ~90–140 m/min and positive rake to control work hardening in casting skin.
Can GS-42CrMo4 be welded?
Weldable with low-hydrogen electrodes matching Cr-Mo composition; preheat 250–350 °C, keep interpass temperature and apply PWHT/temper at 600–680 °C to avoid cold cracking.
Can GS-42CrMo4 be formed, bent or molded?
Sand or investment cast with generous risering and controlled solidification; hot-tear prone at section changes — use fillets, chills and homogenize/normalize before final Q&T.
What surface finishes work on GS-42CrMo4?
No natural corrosion resistance: shot-blast then paint, phosphate, zinc-rich primer, or hard-chrome/nitride the wear surfaces; polishes reasonably well after Q&T.
GS-42CrMo4 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 | 0.38 – 0.45 | 0.42 |
| Si≤0.60 % | ≤ 0.6 | 0.4 |
| Mn | 0.6 – 1 | 0.8 |
| PEN 10293 casting limit | ≤ 0.02 | 0.01 |
| S | ≤ 0.02 | 0.01 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual | ≤ 0.4 | 0.15 |
| Fe | balance | — |
GS-42CrMo4 QT 34-38 HRC — frequently asked
What is GS-42CrMo4 QT 34-38 HRC used for?
GS-42CrMo4 QT 34-38 HRC is typically used for gear housings, heavy machinery parts, crankshaft supports and couplings. In short: cast 4140 equivalent; high-strength Cr-Mo casting; needs preheat and PWHT.
What is the yield strength of GS-42CrMo4 QT 34-38 HRC?
GS-42CrMo4 QT 34-38 HRC has a typical yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is GS-42CrMo4 QT 34-38 HRC easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Rough-machine in the annealed state (≈200 HB); at 280–330 HB use rigid setups, coated carbide, ~90–140 m/min and positive rake to control work hardening in casting skin.
Can GS-42CrMo4 QT 34-38 HRC be welded?
With care — weldability is rated fair (35/100). Weldable with low-hydrogen electrodes matching Cr-Mo composition; preheat 250–350 °C, keep interpass temperature and apply PWHT/temper at 600–680 °C to avoid cold cracking.
What surface finishes work on GS-42CrMo4 QT 34-38 HRC?
No natural corrosion resistance: shot-blast then paint, phosphate, zinc-rich primer, or hard-chrome/nitride the wear surfaces; polishes reasonably well after Q&T.
Can GS-42CrMo4 QT 34-38 HRC be formed, bent or molded?
Sand or investment cast with generous risering and controlled solidification; hot-tear prone at section changes — use fillets, chills and homogenize/normalize before final Q&T.
What is the maximum service temperature of GS-42CrMo4 QT 34-38 HRC?
GS-42CrMo4 QT 34-38 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 GS-42CrMo4 +QT and GS-42CrMo4-F?
+QT is the default condition — standard supply condition: best strength/toughness balance for gears, housings and heavily loaded machine castings. F: raw casting condition, only for non-critical parts or as the starting point before annealing/Q&T. Yield strength is 760 MPa in +QT versus 480 MPa in F.
Sources
- EN 10293 — Steel castings for general engineering uses (G42CrMo4, 1.7231) — CEN (2015)
- DIN 17205 — Quenched and tempered steel castings for general purposes — DIN (1992)
- GB/T 14408 — General purpose low-alloy steel castings (ZG42CrMo) — SAC (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
- SEW 685 / Stahlschlüssel data for 42CrMo4 — Verlag Stahlschlüssel (2019)
- ZG42CrMo 1688 / Mysteel — Mysteel / 1688 (2025)
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.