Steel 4063
AISI/SAE 4063 · UNS G40630
4063 is a high-carbon (0.63 % C) molybdenum alloy steel in the SAE-AISI 40xx family (UNS G40630), stocked annealed, hot-rolled, normalized, cold-drawn and oil-quenched-and-tempered from OQT205 to OQT650.
Reference datasheet — 4063 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the OQT425 condition
4063 tempers and conditions
4063 is supplied in 9 conditions, soft to hard. OQT425 is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
4063 is a high-carbon (0.63 % C) molybdenum alloy steel in the SAE-AISI 40xx family (UNS G40630), stocked annealed, hot-rolled, normalized, cold-drawn and oil-quenched-and-tempered from OQT205 to OQT650. It is specified for heavy-duty coil and leaf springs and torsion bars: in the reference temper it reaches 1365 MPa yield, 1660 MPa tensile, 470 HB (48 HRC) and 12 % elongation. The limits are no corrosion resistance, roughly 200 °C maximum service temperature and high weld crack sensitivity. Where welding or easier machining is required, 4140 is the nearest through-hardening alternative. 4063 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). 4063 has a yield strength of 1,365 MPa (198 ksi) and a tensile strength of 1,660 MPa (241 ksi) — stronger than 96% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4063 used for?
- coil springs
- leaf springs
- torsion bars
Advantages
- High strength — 1,365 MPa (198 ksi), better than 96% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
4063 properties
Typical room-temperature values for 4063-OQT425; bars are the position among steel grades.
Physical3
4063 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 has a yield strength of 1,365 MPa (198 ksi) and a tensile strength of 1,660 MPa (241 ksi) — stronger than 96% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4063 is rated for continuous service to 200°C (392 °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 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 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's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (15/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 4063 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4063
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4063 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G40630
How much does 4063 cost?
4063 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4063 — frequently asked
What is 4063 used for?
4063 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?
4063 has a typical yield strength of 1,365 MPa (198 ksi) and a tensile strength of 1,660 MPa (241 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 4063 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 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?
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 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?
4063 is rated for continuous use to about 200°C (392 °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.
How much does 4063 cost?
4063 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.