Steel 4068
AISI/SAE 4068 · UNS G40680
4068 is a very high-carbon (0.68 % C) molybdenum alloy steel in the SAE-AISI 40xx family (UNS G40680), stocked hot-rolled, annealed, normalized, cold-drawn and quenched-and-tempered (QT205–QT650).
Reference datasheet — 4068 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 A condition
4068 tempers and conditions
4068 is supplied in 9 conditions, soft to hard. A 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 |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Softest, most machinable and formable state — the stocking condition before hardening. | 420 | 700 | 22 | 201 HB | 42 W/m·K |
Hot rolled | Mill as-rolled bar for parts that will be fully heat treated after rough machining or forging. | 520 | 880 | 14 | 25 HRC | 8 % IACS |
Normalized | Uniform fine pearlitic structure for forgings before final hardening or for moderate-strength wear parts. | 620 | 1,010 | 12 | 31 HRC | — |
Cold drawn | Cold-finished bar with tight size and better surface for machined parts that are hardened later. | 690 | 830 | 11 | 22 HRC | 8 % IACS |
Oil quenched and tempered at 650 °C | Softest Q&T condition — best ductility and machinability while keeping tempered-martensite fatigue behaviour. | 800 | 950 | 18 | 30 HRC | — |
Oil quenched and tempered at 540 °C | Balanced strength/toughness for shafts and highly loaded machine parts that must resist shock. | 1,100 | 1,250 | 13 | 39 HRC | — |
Oil quenched and tempered at 425 °C | Typical heavy-spring temper: high elastic limit with usable fatigue and set resistance. | 1,350 | 1,550 | 10 | 46 HRC | — |
Oil quenched and tempered at 315 °C | Very high strength spring/wear condition with slightly improved toughness over 205 °C temper. | 1,550 | 1,900 | 7 | 54 HRC | — |
Oil quenched and tempered at 205 °C | Maximum hardness and wear resistance for punches, blades and cutting edges; very low ductility. | 1,650 | 2,100 | 5 | 58 HRC | 35 W/m·K |
What is 4068?
4068 is a very high-carbon (0.68 % C) molybdenum alloy steel in the SAE-AISI 40xx family (UNS G40680), stocked hot-rolled, annealed, normalized, cold-drawn and quenched-and-tempered (QT205–QT650). It is used for heavy springs, wear parts and high-strength fasteners that need extra hardness after heat treatment; annealed reference values are 420 MPa yield, 700 MPa tensile, 22 % elongation, 201 HB (94 HRB) and 42 W/m·K thermal conductivity. Machinability (45) and formability (30) are low, maximum service is about 200 °C, corrosion resistance is nil and the grade is essentially unweldable. Use 4063 where slightly lower carbon eases processing. 4068 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). 4068 has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4068 used for?
- heavy springs
- wear parts
- high-strength fasteners
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
4068 properties
Typical room-temperature values for 4068-A; bars are the position among steel grades.
Physical3
4068 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
4068 has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4068 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
4068 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 4068 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
4068's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (12/100); formability poor (30/100).
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. 4068 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4068
Is 4068 easy to machine?
Machine in the spheroidize-annealed condition with sharp carbide or coated-carbide tooling and rigid setups; above ~45 HRC use CBN/ceramic hard turning or grinding only.
Can 4068 be welded?
Essentially unweldable in structural use (CE well above 0.9) — if unavoidable, preheat 300–400 °C, use low-hydrogen consumables and post-weld temper immediately.
Can 4068 be formed, bent or molded?
Cold forming limited to gentle bends on spheroidized stock; forge 1100–1200 °C, finish above 900 °C and slow-cool/anneal to avoid cracking, quench in oil from 800–830 °C.
4068 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 of the SAE 40xx series | 0.64 – 0.72 | 0.68 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4068?
No natural corrosion resistance — apply oil, black oxide, manganese phosphate, zinc or Zn-Ni plating (bake at 190 °C for 4 h after plating to avoid hydrogen embrittlement); shot peen springs for fatigue life.
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 4068 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G40680
How much does 4068 cost?
4068 is a budget-cost steel ($), cheaper than about 90% 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.
4068 — frequently asked
What is 4068 used for?
4068 is typically used for heavy springs, wear parts and high-strength fasteners. In short: higher carbon than 4063; hardest 40xx spring grade; grind rather than weld.
What is the yield strength of 4068?
4068 has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 4068 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the spheroidize-annealed condition with sharp carbide or coated-carbide tooling and rigid setups; above ~45 HRC use CBN/ceramic hard turning or grinding only.
Can 4068 be welded?
Not readily — weldability is rated not recommended (12/100). Essentially unweldable in structural use (CE well above 0.9) — if unavoidable, preheat 300–400 °C, use low-hydrogen consumables and post-weld temper immediately.
What surface finishes work on 4068?
No natural corrosion resistance — apply oil, black oxide, manganese phosphate, zinc or Zn-Ni plating (bake at 190 °C for 4 h after plating to avoid hydrogen embrittlement); shot peen springs for fatigue life.
Can 4068 be formed, bent or molded?
Cold forming limited to gentle bends on spheroidized stock; forge 1100–1200 °C, finish above 900 °C and slow-cool/anneal to avoid cracking, quench in oil from 800–830 °C.
What is the maximum service temperature of 4068?
4068 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 4068-A and 4068-QT205?
A is the default condition — softest, most machinable and formable state — the stocking condition before hardening. QT205: maximum hardness and wear resistance for punches, blades and cutting edges; very low ductility. Yield strength is 420 MPa in A versus 1,650 MPa in QT205.
How much does 4068 cost?
4068 is a budget-cost steel ($), cheaper than about 90% 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 / ASTM A29 — Hardenability and general requirements for alloy steel bars — SAE / 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)
- Machining Data Handbook — Metcut Research Associates (1980)
- UNS G40680 alloy steel data records — SAE/ASTM UNS Metals & Alloys (2019)
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.