AISI 4135 forgings
Also designated SAE 4135, UNS G41350, 34CrMo4, 1.7220, SCM435, 35CrMo
AISI 4135 is a low-alloy chromium-molybdenum structural steel with 0.33 to 0.38 % carbon, 0.80 to 1.10 % chromium and 0.15 to 0.25 % molybdenum. It hardens through section and is normally supplied quenched and tempered, for shafts, gears, rings, flanges and valve components. Jiangyin Jiangnan Metal Co., Ltd. open-die forges AISI 4135 to customer drawing at its plant in Jiangyin, Jiangsu, China.
AISI 4135 at a glance
- Steel type
- Low-alloy chromium-molybdenum through-hardening steel
- UNS number
- G41350
- Closest EN grade
- 34CrMo4 (1.7220), EN 10083-3
- Melting route
- EAF + LF + VD (vacuum degassed)
- Forging temperature
- 1150 to 1250 °C, finish above 850 °C
- Hardening
- 830 to 870 °C, oil quench; temper 540 to 680 °C
- Tensile strength
- 700 to 1200 MPa, by ruling section
- Carbon equivalent CE(IIW)
- about 0.72 at mid-range composition
- Density
- 7.85 g/cm³
- Forged by
- Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China
What is AISI 4135 steel?
AISI 4135 belongs to the SAE 41xx chromium-molybdenum series and carries the UNS number G41350. The last two digits of the designation give the nominal carbon content of 0.35 %.
Chromium at around 1 % raises hardenability and resistance to tempering. Molybdenum at 0.20 % holds strength at elevated temperature and cuts susceptibility to temper embrittlement. A section of 100 mm or more will therefore transform to tempered martensite right through, instead of hardening only near the surface. Plain carbon steel cannot hold the property requirement at that depth, so heavy forging drawings call up 4135 instead.
Against AISI 4140, the carbon range of 4135 sits 0.05 % lower. Peak hardness drops slightly, while weldability and impact toughness improve. Welded assemblies, thick-walled pressure parts and components that see shock loading are commonly specified in 4135 for that reason.
The grade offers no corrosion resistance. Wet or sour service calls for a coating, liner, cladding or corrosion allowance. For sour service under NACE MR0175 and ISO 15156, hardness is held at or below 22 HRC by tempering high.
AISI 4135 chemical composition
Composition limits for AISI 4135 are given in mass percent below. Jiangyin Jiangnan Metal Co., Ltd. melts the grade by electric arc furnace with ladle refining and vacuum degassing (EAF + LF + VD). The vacuum stage pulls hydrogen, oxygen and sulfur down before the ingot goes to the press.
| Element | Symbol | Content, % | Function in the steel |
|---|---|---|---|
| Carbon | C | 0.33 – 0.38 | Sets attainable hardness and strength after quenching |
| Silicon | Si | 0.15 – 0.35 | Deoxidiser, raises yield strength |
| Manganese | Mn | 0.70 – 0.90 | Increases hardenability, fixes sulfur |
| Chromium | Cr | 0.80 – 1.10 | Deep hardening, tempering resistance |
| Molybdenum | Mo | 0.15 – 0.25 | Hot strength, resists temper embrittlement |
| Phosphorus | P | ≤ 0.035 | Residual, restricted to protect toughness |
| Sulfur | S | ≤ 0.040 | Residual, restricted to protect transverse ductility |
| Iron | Fe | 97.33 – 97.87 | Balance |
Sulfur and phosphorus can be held below the limits shown. Where a forging needs high transverse toughness or a tight ultrasonic acceptance class, Jiangyin Jiangnan Metal Co., Ltd. works to S at or below 0.015 % and P at or below 0.020 %.
AISI 4135 equivalent grades
34CrMo4, material number 1.7220 in EN 10083-3, is the nearest equivalent to AISI 4135. Carbon and manganese limits differ slightly between the grades listed below, so acceptance follows the standard named on the order rather than the cross-reference.
| Region | Standard | Grade | Nominal C, % |
|---|---|---|---|
| USA | ASTM A29/A29M, SAE J404 | AISI 4135 / SAE 4135 / UNS G41350 | 0.33 – 0.38 |
| Europe | EN 10083-3 | 34CrMo4, 1.7220 | 0.30 – 0.37 |
| Germany | DIN 17200 (superseded) | 34CrMo4 | 0.30 – 0.37 |
| Japan | JIS G4105 | SCM435 | 0.33 – 0.38 |
| China | GB/T 3077 | 35CrMo | 0.32 – 0.40 |
| France | NF A35-552 | 35CrMo4 | 0.32 – 0.38 |
| Russia | GOST 4543 | 35KhM | 0.32 – 0.40 |
| International | ISO 683-2 | 34CrMo4 | 0.30 – 0.37 |
Jiangyin Jiangnan Metal Co., Ltd. supplies forgings against whichever of these standards the purchase order names, and states the governing standard on the EN 10204 certificate.
AISI 4135 mechanical properties
Ruling section and tempering temperature set the mechanical properties of AISI 4135, not the grade designation on its own. A 40 mm shaft and a 250 mm shaft from the same heat will not reach the same strength, because cooling rate at the test position differs. Values below are the minima specified for 34CrMo4 in the quenched and tempered (+QT) condition.
| Ruling section d, mm | Yield Rp0.2, MPa min | Tensile Rm, MPa | Elongation A, % min | Impact KV, J min |
|---|---|---|---|---|
| d ≤ 16 | 800 | 1000 – 1200 | 11 | 35 |
| 16 < d ≤ 40 | 650 | 900 – 1100 | 12 | 40 |
| 40 < d ≤ 100 | 550 | 800 – 950 | 14 | 45 |
| 100 < d ≤ 160 | 500 | 750 – 900 | 15 | 45 |
| 160 < d ≤ 250 | 450 | 700 – 850 | 16 | 45 |
These are the specified minima of the equivalent European grade, quoted for guidance. Properties applying to a delivered forging are the ones recorded on its own mill test certificate, from a test piece taken at the position and depth agreed on the order.
Hardness in other delivery conditions
- Annealed: 241 HBW maximum. The softest condition, used when the customer machines heavily before final heat treatment.
- Normalized: roughly 179 to 229 HBW, with a fine and even grain.
- Quenched and tempered: roughly 220 to 340 HBW, set by tempering temperature.
- Sour service to NACE MR0175: capped at 22 HRC, about 237 HBW, by tempering high.
Heat treatment and forging parameters for AISI 4135
Every AISI 4135 forging leaving Jiangyin Jiangnan Metal Co., Ltd. is heat treated. As-forged structure is coarse and directional. Properties only become predictable once the part has been through the post-forging treatment.
| Operation | Temperature | Cooling | Purpose |
|---|---|---|---|
| Open-die forging | 1150 to 1250 °C, finish above 850 °C | Slow, covered | Close porosity, develop grain flow |
| Soft annealing | 680 to 720 °C | Furnace cool | Bring hardness to 241 HBW or below for machining |
| Normalizing | 850 to 880 °C | Still air | Refine and even out grain after forging |
| Hardening | 830 to 870 °C | Oil quench | Transform to martensite through section |
| Tempering | 540 to 680 °C | Air or oil | Set final strength, hardness and toughness |
| Stress relief | 550 to 650 °C | Furnace cool to 300 °C | Remove machining and welding stresses |
Tempering between 350 °C and 500 °C is avoided. AISI 4135 is susceptible to temper embrittlement in that window, so tempering is carried out above 540 °C and the part is cooled reasonably quickly back through it. Heavy sections get a slow controlled cool after forging rather than being left in still air, which guards against hydrogen flaking in thick ingot-derived forgings.
Physical properties, machining and welding
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Modulus of elasticity | about 210 GPa |
| Poisson's ratio | about 0.29 |
| Thermal conductivity | about 42 W/(m·K) |
| Specific heat capacity | about 473 J/(kg·K) |
| Coefficient of thermal expansion, 20 to 300 °C | about 12.3 × 10−6 /K |
| Carbon equivalent CE(IIW), mid-range | about 0.72 |
Machining
AISI 4135 machines best annealed or normalized. Above roughly 300 HBW it needs carbide tooling, reduced feed rates and rigid fixturing. Where a part calls for deep cuts and high final strength, the usual sequence at Jiangyin Jiangnan Metal Co., Ltd. is rough machining after normalizing, then quench and temper, then finish machining. The finishing pass also takes off the decarburized surface layer.
Welding
AISI 4135 welds with a qualified procedure. Carbon equivalent CE(IIW) runs at about 0.72 on mid-range composition, so the heat-affected zone hardens and becomes prone to hydrogen cracking. Normal practice is preheat and interpass temperature of 200 to 300 °C, low-hydrogen consumables kept in a heated quiver, and post-weld heat treatment at 600 to 680 °C followed by controlled cooling. Welding onto a part already quenched and tempered will over-temper it locally, so weld sequence and final heat treatment are planned together.
AISI 4135 forged shapes supplied
Jiangyin Jiangnan Metal Co., Ltd. produces the following shapes in AISI 4135 by open-die forging and ring rolling, all to customer drawing. Surface condition on delivery is as-forged, shot blasted, rough machined or finish machined.
| Product form | Also called | Typical parts |
|---|---|---|
| Seamless rolled rings | Forged rings, ring-rolled rings | Bearing races, retaining rings, flange blanks, gear rims |
| Shafts | Stepped shafts, pinion shafts, spindles | Gearbox shafts, eccentric shafts, crankshafts, roller shafts |
| Flanges | Forged flanges, blind flanges | Weld-neck blanks, blind and slip-on flange blanks |
| Discs and blocks | Forged disks, discs, plates, blanks | Gear blanks, cover plates, die blocks |
| Sleeves and hollow bars | Bushings, bushes, cases, shells, housings | Bearing sleeves, wear bushings, cylinder liners, barrels |
| Bars | Round, square, flat and rectangular bars | Machining stock for shafts, pins and connectors |
| Gear blanks | Gear wheels, ring gears, pinion blanks | Mill pinions, ring gear segments, transmission gears |
| Tubes and tube sheets | Forged pipes, tubings, tube plates | Heat exchanger tube sheets, nozzles, forged piping |
| Valve components | Bodies, bonnets, seat rings, stems, blocks | Ball, gate, globe, check and plug valve parts |
Manufacturing and inspection route for AISI 4135 forgings
This is the sequence Jiangyin Jiangnan Metal Co., Ltd. follows for AISI 4135 open-die forgings.
- Melting by EAF, LF and VDElectric arc furnace melting, ladle furnace refining, then vacuum degassing. The vacuum stage brings hydrogen down. Heavy sections are liable to flake if it is skipped.
- Ingot or billet to forgingHeating to 1150 to 1250 °C, then upsetting and drawing under the press with the forging finished above 850 °C. Upsetting and drawing breaks the cast dendritic structure and lines grain flow up with the part.
- Ring rollingFor rings, the pierced blank is rolled out to final diameter. This produces continuous circumferential grain flow that a ring machined from plate cannot match.
- Heat treatmentAnnealing, normalizing, normalizing and tempering, or quenching and tempering, in furnaces with calibrated and recorded temperature profiles.
- Mechanical testingTensile, impact and hardness tests on pieces cut from prolongations or sacrificial rings, at the position and depth the order specifies.
- Ultrasonic testingVolumetric inspection to ASTM A388/A388M, EN 10228-3 or SEP 1921, to the acceptance class named on the order. Magnetic particle inspection to ASTM E709 on request.
- Dimensional check and certificationDimensional report plus an EN 10204 3.1 mill certificate, or a third-party EN 10204 3.2 certificate witnessed by TUV, SGS, BV or Lloyd's Register.
What AISI 4135 forgings are used for
AISI 4135 is specified where a part has to carry high stress through a thick section and still take shock loading or welding.
| Industry | AISI 4135 forged components |
|---|---|
| Oil, gas and offshore | Subsea and deepwater production components, wellhead and Christmas tree parts, drill collars, forged blocks and bodies |
| Valves | Valve bodies and bonnets, seat rings, stems, forged blocks for ball, gate, globe, check and plug valves |
| Pressure vessels and heat exchangers | Forged flanges, tube sheets, shells, nozzles, forged tubes, air receiver components |
| Power transmission | Gear blanks, ring gears, pinion shafts, spindles, couplings, gearbox shafts |
| Power generation and turbines | Turbine and generator shafts, compressor components, nitrogen generator parts |
| Cement, mining and sugar mills | Mill pinion shafts, rotary kiln components, roller shafts, crusher parts, mixer shafts |
| Pumps and compressors | Chemical and plunger pump shafts, sleeves, bushings, crankshafts, air compressor components |
| Shipbuilding and heavy machinery | Forged wheels, manifolds, rolls, crane wheels, heavy machine shafts |
| Process plant | Columns and towers, tanks, silos, preheaters, process modules, crystallizer equipment |
About the forging factory
Jiangyin Jiangnan Metal Co., Ltd. runs an open-die forging plant at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The site sits inside the Jiangyin forging cluster on the lower Yangtze, within road distance of the ports of Shanghai and Ningbo.
Work covers alloy steel, carbon steel, tool steel, stainless steel and nickel alloys, forged to customer drawing as rings, shafts, flanges, discs, sleeves, bars, gear blanks and valve components. Material goes out against EN 10204 3.1 certification, or third-party 3.2 certification where the order calls for it.
Grades ordered most often alongside AISI 4135: AISI 4140, 42CrMo4, 34CrMo4, AISI 4130 and 35KhM.
How to request a quotation for AISI 4135 forgings
Send the items below to sales@steelforgepieces.com. Price, forging weight, lead time and Incoterms normally come back within one working day.
- Drawing or dimensionsA 2D drawing, a 3D model, or rough forging dimensions. For rings, give outside diameter, inside diameter and height. For shafts, give diameter and length.
- Ordering standard and delivery conditionWhich standard governs, whether ASTM A29/A29M, EN 10083-3, EN 10250-3 or your own specification, and whether the forging is to be annealed, normalized, normalized and tempered, or quenched and tempered.
- Testing and certificationMechanical test requirements and test piece location, the ultrasonic standard and acceptance class under ASTM A388, EN 10228-3 or SEP 1921, and whether EN 10204 3.1 or third-party 3.2 certification is needed.
- Quantity and machiningOrder quantity, and whether the part is wanted black, shot blasted, rough machined or finish machined, with the machining allowance you expect.
- DestinationPort or delivery address and preferred Incoterms, so freight can be included in the quotation.
Frequently asked questions about AISI 4135
What is AISI 4135 steel?
AISI 4135 is a low-alloy chromium-molybdenum structural steel with 0.33 to 0.38 % carbon, 0.80 to 1.10 % chromium and 0.15 to 0.25 % molybdenum. It carries the UNS number G41350 and is also written SAE 4135. The grade hardens through section and is normally supplied quenched and tempered, for shafts, gears, rings, flanges, valve bodies and pressure-containing forgings.
What is the equivalent of AISI 4135?
The nearest equivalents to AISI 4135 are 34CrMo4, material number 1.7220, in EN 10083-3; SCM435 in JIS G4105; 35CrMo in GB/T 3077; 35CrMo4 in AFNOR NF A35-552; and 35KhM in GOST 4543. The grades are close but not identical, so chemistry and mechanical acceptance limits follow the standard named on the order.
What is the difference between AISI 4135 and AISI 4140?
Carbon content is the difference. AISI 4135 runs 0.33 to 0.38 % carbon and AISI 4140 runs 0.38 to 0.43 %, with both holding around 1 % chromium and 0.20 % molybdenum. The lower carbon of AISI 4135 gives slightly lower attainable hardness and strength, with better weldability and impact toughness. AISI 4135 therefore suits welded and thick-section forgings, while AISI 4140 is chosen where higher strength is required.
Can AISI 4135 be welded?
Yes, with a qualified procedure. Carbon equivalent CE(IIW) runs at about 0.72 on mid-range composition, so the heat-affected zone hardens and becomes prone to hydrogen cracking. Preheat and interpass temperature of 200 to 300 °C, low-hydrogen consumables and post-weld heat treatment at 600 to 680 °C are normally required.
What is the forging temperature of AISI 4135?
AISI 4135 is heated to 1150 to 1250 °C for open-die forging, with the forging operation finished above about 850 °C and followed by slow cooling. Jiangyin Jiangnan Metal Co., Ltd. then normalizes or quenches and tempers the forging to refine the grain and reach the specified mechanical properties.
Does AISI 4135 have to be heat treated after forging?
Yes. As-forged AISI 4135 has a coarse and uneven structure, so a post-forging heat treatment is always specified: annealing at 680 to 720 °C for machinability, normalizing at 850 to 880 °C, or hardening from 830 to 870 °C in oil followed by tempering at 540 to 680 °C for final strength and toughness.
Who supplies AISI 4135 open-die forgings and rolled rings?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, produces AISI 4135 forged rings, shafts, flanges, discs, sleeves, blocks and bars to customer drawing. Enquiries go to sales@steelforgepieces.com or telephone +86-189-2135-9659.
What certification is supplied with AISI 4135 forgings?
Jiangyin Jiangnan Metal Co., Ltd. supplies AISI 4135 forgings with an EN 10204 3.1 mill test certificate showing heat chemistry and mechanical test results. Where the order calls for it, a third-party EN 10204 3.2 certificate witnessed by an inspection body such as TUV, SGS, BV or Lloyd's Register is provided instead.
What ultrasonic testing standards apply to AISI 4135 forgings?
AISI 4135 forgings are ultrasonically tested to ASTM A388/A388M, EN 10228-3 or SEP 1921, with the acceptance class agreed at order. The quality class, for example EN 10228-3 class 2 or class 3, should be stated on the purchase order. It affects the required forging ratio as well as the price.
What shapes can be open-die forged in AISI 4135?
AISI 4135 is open-die forged into seamless rolled rings, round and square bars, stepped shafts, pinion and gear blanks, discs and blocks, flanges, hollow bars, sleeves, bushings, tube sheets, valve bodies and bonnets. Jiangyin Jiangnan Metal Co., Ltd. forges these shapes to customer drawing in black, rough-machined or finish-machined condition.
Standards referenced on this page
- ASTM A29/A29M: general requirements for steel bars, carbon and alloy, hot-wrought
- SAE J404: chemical compositions of SAE alloy steels
- EN 10083-3: steels for quenching and tempering, alloy steels (34CrMo4, 1.7220)
- EN 10250-3: open-die steel forgings for general engineering, alloy special steels
- JIS G4105: chromium molybdenum steels (SCM435)
- GB/T 3077: alloy structural steels (35CrMo)
- GOST 4543: structural alloy steels (35KhM)
- ISO 683-2: heat-treatable steels, alloy steels
- EN 10204: types of inspection documents, 3.1 and 3.2
- ASTM A388/A388M: ultrasonic examination of steel forgings
- EN 10228-3: non-destructive testing of steel forgings, ultrasonic testing of ferritic or martensitic steel forgings
- SEP 1921: ultrasonic testing of steel forgings, quality classes
- NACE MR0175 and ISO 15156: materials for use in H2S-containing environments
Document reference
Published by Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.
Page: AISI 4135 forgings, composition, properties and equivalents. https://www.steelforgepieces.com/Alloy-Steel/AISI-4135.html. Last reviewed 13 September 2026. A plain-text version is available at AISI-4135.md.
Figures on this page are for guidance. The mill test certificate governs a delivered forging.
Get an AISI 4135 forging quoted
Send a drawing or the rough dimensions. Jiangyin Jiangnan Metal Co., Ltd. quotes price, forging weight and lead time, normally within one working day.
Open-die forging factory
Jiangyin City, Jiangsu Province, China