Steel 4130 · heat-treated state
Steel 4130 Q&T 205
Properties of the Q&T 205 condition, compared with the other 4130 tempers.
Maximum-strength condition (~1550 MPa) for small highly stressed parts; brittle, notch- and hydrogen-sensitive, not for welding.
What is 4130 Q&T 205?
4130 Q&T 205 is 4130 heat treated to Q&T 205 — maximum-strength condition (~1550 MPa) for small highly stressed parts; brittle, notch- and hydrogen-sensitive, not for welding. 4130 Q&T 205 has a yield strength of 1,340 MPa (194 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi). 4130 Q&T 205 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,432°C (2,610 °F). HR is the default condition FabDigit quotes; Q&T 205 is available on request or by drawing note.
Advantages
- High strength — 1,340 MPa (194 ksi), better than 95% of steel grades
Limitations
- Limited service temperature — 175°C (347 °F), worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 79% of steel grades
4130 Q&T 205 properties
Typical room-temperature values for 4130 Q&T 205 — 14 properties are specific to this condition; the rest are grade-level values shared by every 4130 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
4130 Q&T 205 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,432°C (2,610 °F).
Mechanical16
4130 Q&T 205 has a yield strength of 1,340 MPa (194 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4130 Q&T 205 is rated for continuous service to 175°C (347 °F). It conducts heat at 42.7 W/m·K (24.7 BTU/hr·ft·°F), better than 50% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
4130 Q&T 205 conducts electricity at 7.7 % IACS, worse than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 4130 Q&T 205 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability7
4130 Q&T 205's machinability is good (55/100, better than 62% of steel grades); weldability poor (20/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 4130 tempers and conditions
4130 is also supplied in 11 other conditions. The full side-by-side table is on the 4130 overview.
- HRDefaultCheapest mill condition for bar and plate that will be heat treated or machined afterwards; scaled surface and variable properties.440 MPa yield · 210 HB
- Q&T 205Maximum-strength condition (~1550 MPa) for small highly stressed parts; brittle, notch- and hydrogen-sensitive, not for welding.1,340 MPa yield · 48 HRC
- Q&T 40-44 HRCUse for wear-loaded pins, tooling and drill components; toughness and weldability drop sharply at this hardness.1,150 MPa yield · 42 HRC
- Q&T 32-36 HRCHigher-strength band (~1150 MPa) for gears, sprockets and highly loaded fasteners where some toughness is still needed.1,040 MPa yield · 34 HRC
- Q&TGeneral-purpose hardened condition for shafts, fittings and pressure parts needing ~1000 MPa with retained toughness.910 MPa yield · 31 HRC
- Q&T 28-32 HRCMost common ordered hardness band for machined 4130 shafts, flanges and hydraulic bodies.910 MPa yield · 30 HRC
- Q&T 22-26 HRCPick when hardness must stay ≤22–26 HRC for H₂S/sour service or maximum ductility in a hardened part.700 MPa yield · 24 HRC
- CRThin strip and sheet with tight thickness tolerance and smooth surface; strength raised and ductility cut by the cold reduction.690 MPa yield · 22 HRC
- CDChoose for straight, on-size shafting with good surface finish where no further heat treatment is planned.600 MPa yield · 17 HRC
- N&TNormalized then high-temper for lower hardness and better dimensional stability/toughness in welded or machined structures.500 MPa yield · 197 HB
- NormalizedDefault stock condition for aircraft-quality 4130 sheet and seamless tube: uniform fine grain, good toughness and weldability at ~730 MPa.460 MPa yield · 217 HB
- AnnealedSoftest and most machinable/formable condition; use for deep machining, cold bending or as the starting point before hardening.361 MPa yield · 156 HB
Working with 4130 Q&T 205
Is 4130 easy to machine?
Machines best annealed or normalized (~200 HB) with carbide at moderate speed and heavy positive feed; above 32 HRC expect tool wear, so rough before hardening and finish-grind after.
Can 4130 be welded?
Readily TIG/MIG welded with ER80S-D2 or ER70S-2 filler; preheat 150–250 °C for sections over ~3 mm, avoid quench-hard HAZ by slow cooling and stress relieve 590–650 °C, then re-normalize if full properties are required.
Can 4130 be formed, bent or molded?
Cold bend only in annealed/normalized thin sheet and tube with generous radii (≥3t); hot form 850–1150 °C and re-normalize afterwards, hardened material must not be cold formed.
What surface finishes work on 4130?
No natural corrosion resistance — specify zinc, cadmium or nickel plate, phosphate-and-oil, black oxide or epoxy paint; bake plated high-strength parts at 190 °C to relieve hydrogen.
4130 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 |
|---|---|---|
| CGB 30CrMo: 0.26–0.34 | 0.28 – 0.33 | 0.3 |
| Mn | 0.4 – 0.6 | 0.5 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.8 – 1.1 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | — |
| Smax; 0.025 max for aircraft quality | ≤ 0.04 | — |
| Fe | balance | — |
4130 Q&T 205 — frequently asked
What is 4130 Q&T 205 used for?
4130 Q&T 205 is typically used for roll cages and tube space frames, aircraft engine mounts, high-pressure gas cylinders, drill collars and downhole tools, machine shafts and spindles and hydraulic cylinder rods. In short: tough aerospace chromoly.
What is the yield strength of 4130 Q&T 205?
4130 Q&T 205 has a typical yield strength of 1,340 MPa (194 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 4130 Q&T 205 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines best annealed or normalized (~200 HB) with carbide at moderate speed and heavy positive feed; above 32 HRC expect tool wear, so rough before hardening and finish-grind after.
Can 4130 Q&T 205 be welded?
Not readily — weldability is rated poor (20/100). Readily TIG/MIG welded with ER80S-D2 or ER70S-2 filler; preheat 150–250 °C for sections over ~3 mm, avoid quench-hard HAZ by slow cooling and stress relieve 590–650 °C, then re-normalize if full properties are required.
What surface finishes work on 4130 Q&T 205?
No natural corrosion resistance — specify zinc, cadmium or nickel plate, phosphate-and-oil, black oxide or epoxy paint; bake plated high-strength parts at 190 °C to relieve hydrogen.
Can 4130 Q&T 205 be formed, bent or molded?
Cold bend only in annealed/normalized thin sheet and tube with generous radii (≥3t); hot form 850–1150 °C and re-normalize afterwards, hardened material must not be cold formed.
What is the maximum service temperature of 4130 Q&T 205?
4130 Q&T 205 is rated for continuous use to about 175°C (347 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4130-HR and 4130-CR?
HR is the default condition — cheapest mill condition for bar and plate that will be heat treated or machined afterwards; scaled surface and variable properties. CR: thin strip and sheet with tight thickness tolerance and smooth surface; strength raised and ductility cut by the cold reduction. Yield strength is 440 MPa in HR versus 690 MPa in CR.
Can FabDigit make parts in 4130 Q&T 205?
Yes — 4130 Q&T 205 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
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (2020)
- ASTM A519 — Seamless Carbon and Alloy Steel Mechanical Tubing — ASTM International (2022)
- AMS 6345 / AMS 6360 — 4130 sheet, plate and tubing (normalized) — SAE International (2019)
- GB/T 3077 — (30CrMo) (2015)
- EN 10083-3 — Quenched and tempered steels, 25CrMo4 (1.7218) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- MMPDS-17 Metallic Materials Properties Development and Standardization — Battelle/FAA (2022)
- Atlas of Stress-Strain Curves / ASM Fatigue Data Book — ASM International (2002)
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.