Steel 4135
AISI/SAE 4135
AISI 4135 is a medium-carbon 1 % Cr–0.2 % Mo through-hardening alloy steel, sitting between 4130 and 4140 in carbon content, and is essentially equivalent to Chinese 35CrMo / EN 34CrMo4.
Values for the HR condition
4135 tempers and conditions
4135 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 |
|---|---|---|---|---|---|---|
full/subcritical anneal, softest machining condition | Pick for maximum machinability, cold forming or before further heat treatment. | 390 | 610 | 26 | 175 HB | — |
HRDefault Hot rolled | Default stock condition for bar and plate that will be machined and then heat treated by the user. | 460 | 700 | 20 | 200 HB | — |
Normalized and tempered | Use where normalized strength is enough but residual stress and hardness must be lowered for machining or welding. | 540 | 800 | 22 | 21 HRC | 7.8 % IACS |
austenitized ~870 °C, air cooled | Uniform fine-grain structure with higher strength than annealed; common for tube and forgings before machining. | 570 | 860 | 20 | 24 HRC | — |
Cold rolled | Thin sheet/strip form with smooth surface and tight gauge, usually formed then heat treated. | 620 | 760 | 11 | 20 HRC | 7.8 % IACS |
Cold drawn | Choose for close-tolerance bright bar with raised yield strength and good surface, machined without further heat treatment. | 680 | 790 | 12 | 230 HB | — |
Tempered to sour-service / bolting hardness band | Specified where a controlled hardness band is required (NACE-limited hardware, high-strength fasteners). | 820 | 960 | 16 | 30 HRC | 7.5 % IACS |
Quenched and tempered | Standard delivery condition for shafts, bolts and gears needing ~1000 MPa strength with good toughness. | 850 | 1,000 | 15 | 31 HRC | — |
Higher-strength tempered condition | Use for highly loaded shafts, torsion parts and tool holders where ~1150 MPa is needed and toughness can be traded down. | 1,010 | 1,150 | 13 | 36 HRC | — |
What is 4135?
AISI 4135 is a medium-carbon 1 % Cr–0.2 % Mo through-hardening alloy steel, sitting between 4130 and 4140 in carbon content, and is essentially equivalent to Chinese 35CrMo / EN 34CrMo4. It is chosen for shafts, bolts, gears, tube for high-pressure/aerospace structures and tooling holders where a good balance of strength, toughness and hardenability up to ~1000–1200 MPa is needed at low cost. Limits are poor corrosion resistance (must be plated or painted), need for preheat/post-weld tempering to avoid hydrogen and quench cracking, and loss of strength above about 400 °C. 4135 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 4135 has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 55% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4135 used for?
- Industrial drive and axle shafts
- High-strength bolts and studs
- Gears and pinions
- High-pressure cylinder and aerospace tube
- Hydraulic piston rods
- Tool holders and machine spindles
- Forged structural fittings
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
4135 properties
Typical room-temperature values for 4135-HR; bars are the position among steel grades.
Physical3
4135 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical15
4135 has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 55% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4135 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).
Electrical3
4135 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4135 takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
4135's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability fair (45/100).
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. 4135 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4135
Is 4135 easy to machine?
Machines well at 180–230 HB with carbide at 120–200 m/min; above 34 HRC use coated carbide/CBN, rigid setups and reduced feed, and prefer rough-machining before final temper.
Can 4135 be welded?
Weldable with low-hydrogen E80xx/ER80S-D2 filler but requires 200–320 °C preheat, controlled interpass and post-weld temper/stress relief at 600–650 °C to avoid HAZ cracking.
Can 4135 be formed, bent or molded?
Cold form only in annealed condition with generous radii; hot forge at 1150–1200 °C finishing above 900 °C, then normalize or anneal before machining.
Manufacturability
The process limits FabDigit applies to 4135. Every 4135 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better58 / 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 | Fair45 / 100 |
|---|---|
| Weldability | Better45 / 100 |
4135 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 J404 / ASTM A29 | 0.33 – 0.38 | 0.35 |
| Mn | 0.7 – 0.9 | 0.8 |
| 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; 4135H/resulfurized variants differ | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4135?
Not anodizable — protect with zinc, zinc-nickel or hard chrome plating, phosphate/oil or black oxide; bake after plating to relieve hydrogen; gas nitriding gives a hard wear surface without distortion.
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 4135 cost?
4135 is a standard-cost steel ($$), cheaper than about 62% 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.
4135 — frequently asked
What is 4135 used for?
4135 is typically used for industrial drive and axle shafts, high-strength bolts and studs, gears and pinions, high-pressure cylinder and aerospace tube, hydraulic piston rods and tool holders and machine spindles. In short: workhorse Cr-Mo bar.
What is the yield strength of 4135?
4135 has a typical yield strength of 460 MPa (66.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 55% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 4135 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines well at 180–230 HB with carbide at 120–200 m/min; above 34 HRC use coated carbide/CBN, rigid setups and reduced feed, and prefer rough-machining before final temper.
Can 4135 be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen E80xx/ER80S-D2 filler but requires 200–320 °C preheat, controlled interpass and post-weld temper/stress relief at 600–650 °C to avoid HAZ cracking.
What surface finishes work on 4135?
Not anodizable — protect with zinc, zinc-nickel or hard chrome plating, phosphate/oil or black oxide; bake after plating to relieve hydrogen; gas nitriding gives a hard wear surface without distortion.
Can 4135 be formed, bent or molded?
Cold form only in annealed condition with generous radii; hot forge at 1150–1200 °C finishing above 900 °C, then normalize or anneal before machining.
What is the maximum service temperature of 4135?
4135 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 4135-HR and 4135-CD?
HR is the default condition — default stock condition for bar and plate that will be machined and then heat treated by the user. CD: choose for close-tolerance bright bar with raised yield strength and good surface, machined without further heat treatment. Yield strength is 460 MPa in HR versus 680 MPa in CD.
How much does 4135 cost?
4135 is a standard-cost steel ($$), cheaper than about 62% 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 4135?
Yes — 4135 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 — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- GB/T 3077 — (35CrMo) — SAC (2015)
- EN 10083-3 — Quenched and tempered steels (34CrMo4) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
- 35CrMo — Mysteel (2025)
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.