Steel 4063 OQT540
Heat-treated state
AISI/SAE 4063 · UNS G40630
OQT540 = q&T
Tougher, more machinable condition for large sections and shock-loaded spring or link parts.
Values for the OQT540 condition
Other 4063 tempers and conditions
4063 is listed in 9 conditions; see the grade overview at 4063.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose for cold coiling, machining or blanking before final quench-and-temper. | 420 | 730 | 22 | 210 HB | — |
Hot rolled | Mill supply condition for forging or hot coiling followed by heat treatment. | 540 | 950 | 14 | 28 HRC | 8.2 % IACS |
Normalized | Use to homogenize forgings and refine grain before hardening; not a service condition for springs. | 700 | 1,100 | 13 | 34 HRC | 8 % IACS |
Cold drawn | Pick for close tolerance bar or hard-drawn spring wire where no further hardening is planned. | 860 | 1,030 | 9 | 31 HRC | 8 % IACS |
Q&T | Softest quench-and-temper level: best toughness and machinability, lowest set resistance. | 910 | 1,060 | 19 | 31 HRC | — |
OQT540This page Q&T | Tougher, more machinable condition for large sections and shock-loaded spring or link parts. | 1,160 | 1,350 | 15 | 42 HRC | — |
OQT425Default Q&T | Standard service condition for heavy coil and leaf springs — best balance of strength, set resistance and fatigue life. | 1,365 | 1,660 | 12 | 48 HRC | — |
Q&T | High-strength spring and fastener condition where a little more ductility than 205 °C temper is needed. | 1,655 | 2,000 | 10 | 53 HRC | — |
Q&T | Maximum strength and wear resistance; very low toughness, use only for low-impact, high-stress parts. | 1,790 | 2,380 | 10 | 58 HRC | — |
What is 4063 OQT540?
4063 OQT540 is 4063 heat treated to OQT540 — tougher, more machinable condition for large sections and shock-loaded spring or link parts. 4063 OQT540 has a yield strength of 1,160 MPa (168 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 4063 OQT540 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F). OQT425 is the default condition FabDigit quotes; OQT540 is available on request or by drawing note.
Advantages
- High strength — 1,160 MPa (168 ksi), better than 94% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 15/100, worse than 91% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
4063 OQT540 properties
Typical room-temperature values for 4063 OQT540; 12 are specific to this condition. Other listed values are 4063 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4063 OQT540 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
4063 OQT540 has a yield strength of 1,160 MPa (168 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4063 OQT540 is rated for continuous service to 300°C (572 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
4063 OQT540 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 4063 OQT540 takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability6
4063 OQT540's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (15/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4063 OQT540
Is 4063 easy to machine?
Machine in the annealed or ≤33 HRC tempered state with carbide tooling, rigid setups and generous coolant; grinding is the practical route above 45 HRC.
Can 4063 be welded?
Not recommended as a welded grade — 0.63 %C gives high crack sensitivity; if unavoidable, preheat 250–350 °C, use low-hydrogen consumables and post-weld temper immediately.
Can 4063 be formed, bent or molded?
Cold coil or bend only in the spheroidize-annealed condition with generous radii; otherwise hot form at 900–1050 °C, then austenitize ~815–845 °C, oil quench and temper.
What surface finishes work on 4063?
Shot peen springs for fatigue life, then phosphate + oil, powder coat or zinc-rich paint; avoid unbaked electroplating (hydrogen embrittlement) at high hardness.
4063 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 |
|---|---|---|
| Chighest-carbon grade of the SAE 40xx series | 0.6 – 0.67 | 0.63 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Mohardenability and temper resistance | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
4063 OQT540 — frequently asked
What is 4063 OQT540 used for?
4063 OQT540 is typically used for coil springs, leaf springs and torsion bars. In short: high-strength spring steel; 48 HRC after oil quench; not a welding grade.
What is the yield strength of 4063 OQT540?
4063 OQT540 has a typical yield strength of 1,160 MPa (168 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 4063 OQT540 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine in the annealed or ≤33 HRC tempered state with carbide tooling, rigid setups and generous coolant; grinding is the practical route above 45 HRC.
Can 4063 OQT540 be welded?
Not readily — weldability is rated poor (15/100). Not recommended as a welded grade — 0.63 %C gives high crack sensitivity; if unavoidable, preheat 250–350 °C, use low-hydrogen consumables and post-weld temper immediately.
What surface finishes work on 4063 OQT540?
Shot peen springs for fatigue life, then phosphate + oil, powder coat or zinc-rich paint; avoid unbaked electroplating (hydrogen embrittlement) at high hardness.
Can 4063 OQT540 be formed, bent or molded?
Cold coil or bend only in the spheroidize-annealed condition with generous radii; otherwise hot form at 900–1050 °C, then austenitize ~815–845 °C, oil quench and temper.
What is the maximum service temperature of 4063 OQT540?
4063 OQT540 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4063 OQT425 and 4063-A?
OQT425 is the default condition — standard service condition for heavy coil and leaf springs — best balance of strength, set resistance and fatigue life. A: choose for cold coiling, machining or blanking before final quench-and-temper. Yield strength is 1,365 MPa in OQT425 versus 420 MPa in A.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Alloy H-Steels — SAE International (2019)
- ASTM A29/A29M — General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- SAE HS-788 / Spring Design Manual — SAE International (1996)
- MatWeb alloy steel data sheets (SAE 40xx series) — MatWeb LLC (2024)
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.