Steel 4350
AISI/SAE 4350
4350 is the highest-carbon member of the AISI/SAE 4340 Ni-Cr-Mo family, with about 0.50% C and very high hardenability: oil quenching and tempering can reach over 1700 MPa tensile and around 50 HRC, while the default Q&T data here is 650 MPa yield, 1000 MPa tensile, 12% elongation and 295 HB.
Values for the HR condition
4350 tempers and conditions
4350 is supplied in 9 conditions, soft to hard. HR 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 |
|---|---|---|---|---|---|---|
Spheroidize Annealed | Choose when maximum softness and best cold-heading / cold-extrusion behaviour is needed from this high-carbon grade. | 470 | 740 | 22 | 16 HRC | 7.5 % IACS |
Temper | Softest supply condition — best for heavy machining, deep boring or cold forming before hardening. | 520 | 800 | 18 | 235 HB | — |
HRDefault Hot rolled | Most commonly stocked bar condition — as-rolled blanks for subsequent machining and heat treatment. | 650 | 1,000 | 12 | 31 HRC | — |
Cold drawn | Bright, close-tolerance bar with raised strength — for shafts and parts finished without further heat treatment. | 900 | 1,050 | 10 | 33 HRC | — |
Heat Treat State | Uniform fine-grained structure before final hardening; also used where high as-supplied strength is acceptable without Q&T. | 900 | 1,320 | 10 | 41 HRC | — |
Cold rolled | Cold-rolled strip/flat stock for blanked and later hardened parts (springs, blades, wear plates). | 930 | 1,080 | 8 | 34 HRC | 6.9 % IACS |
Q&T to 40–45 HRC | Higher-temper option when some toughness and machinability must be retained (heavy shafts, gear blanks). | 1,250 | 1,400 | 11 | 42 HRC | — |
Q&T to 48–52 HRC | Low-temper, high-wear condition for tool shanks, dies and highly loaded pins; finish grinding usually required. | 1,520 | 1,760 | 8 | 50 HRC | — |
Quenched and tempered | Standard high-strength condition: oil quench from ~830 °C and temper 200–450 °C for maximum strength/wear resistance. | 1,550 | 1,800 | 8 | 50 HRC | — |
What is 4350?
4350 is the highest-carbon member of the AISI/SAE 4340 Ni-Cr-Mo family, with about 0.50% C and very high hardenability: oil quenching and tempering can reach over 1700 MPa tensile and around 50 HRC, while the default Q&T data here is 650 MPa yield, 1000 MPa tensile, 12% elongation and 295 HB. It suits heavily loaded shafts, gears, die holders, tool shanks and high-strength fasteners where 4340 lacks strength or wear resistance. Ductility, toughness and weldability are lower than 4340, the high carbon equivalent needs preheat and post-weld tempering, and hardened sections are sensitive to hydrogen embrittlement and stress raisers. 4350 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). 4350 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 79% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4350 used for?
- Shafts
- Gears
- Axles
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 650 MPa (94.3 ksi), better than 79% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 22/100, worse than 81% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
- Limited formability — 22/100, worse than 76% of steel grades
4350 properties
Typical room-temperature values for 4350-HR; bars are the position among steel grades.
Physical3
4350 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).
Mechanical14
4350 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 79% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4350 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).
Electrical2
4350 has an electrical resistivity of 2.5×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4350 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
4350's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (22/100); formability poor (22/100).
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. 4350 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4350
Is 4350 easy to machine?
Machine in the annealed or spheroidized state (~50% of AISI 1212); above 40 HRC use carbide/CBN, rigid setups, low speeds or grind to finish.
Can 4350 be welded?
Poor weldability — high carbon equivalent; preheat 300–400 °C, low-hydrogen or matching filler, immediate post-weld temper below the part's tempering temperature, and avoid welding on fully hardened sections.
Can 4350 be formed, bent or molded?
Cold forming only in spheroidized condition and with generous radii; hot forge 1050–1200 °C, finish above 900 °C, then slow-cool or normalize to prevent quench cracking.
Manufacturability
The process limits FabDigit applies to 4350. Every 4350 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better42 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair22 / 100 |
|---|---|
| Weldability | Better22 / 100 |
4350 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 |
|---|---|---|
| CSAE 4350 carbon range | 0.48 – 0.53 | 0.5 |
| Mn | 0.75 – 1 | 0.87 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 1.65 – 2 | 1.82 |
| Cr | 0.7 – 0.9 | 0.8 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | |
| Smax; lower for aircraft-quality (E-grade) material | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4350?
No anodizing; protect with black oxide, manganese phosphate, oil, or zinc/nickel plating — bake at 190–210 °C after acid pickling or electroplating to avoid hydrogen embrittlement. Nitriding and hard chrome are common for wear surfaces.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
How much does 4350 cost?
4350 is a standard-cost steel ($$), cheaper than about 61% 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.
4350 — frequently asked
What is 4350 used for?
4350 is typically used for shafts, gears and axles. In short: premium Ni-Cr-Mo bar.
What is the yield strength of 4350?
4350 has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 4350 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in the annealed or spheroidized state (~50% of AISI 1212); above 40 HRC use carbide/CBN, rigid setups, low speeds or grind to finish.
Can 4350 be welded?
Not readily — weldability is rated poor (22/100). Poor weldability — high carbon equivalent; preheat 300–400 °C, low-hydrogen or matching filler, immediate post-weld temper below the part's tempering temperature, and avoid welding on fully hardened sections.
What surface finishes work on 4350?
No anodizing; protect with black oxide, manganese phosphate, oil, or zinc/nickel plating — bake at 190–210 °C after acid pickling or electroplating to avoid hydrogen embrittlement. Nitriding and hard chrome are common for wear surfaces.
Can 4350 be formed, bent or molded?
Cold forming only in spheroidized condition and with generous radii; hot forge 1050–1200 °C, finish above 900 °C, then slow-cool or normalize to prevent quench cracking.
What is the maximum service temperature of 4350?
4350 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 4350-HR and 4350-CR?
HR is the default condition — most commonly stocked bar condition — as-rolled blanks for subsequent machining and heat treatment. CR: cold-rolled strip/flat stock for blanked and later hardened parts (springs, blades, wear plates). Yield strength is 650 MPa in HR versus 930 MPa in CR.
How much does 4350 cost?
4350 is a standard-cost steel ($$), cheaper than about 61% 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.
Can FabDigit make parts in 4350?
Yes — 4350 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- 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)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
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.