AISI 4140H is the hardenability-guaranteed version of AISI 4140 chromium-molybdenum alloy steel. It carries the UNS number H41400 and is specified in SAE J1268 and ASTM A304. The H suffix means the steel is ordered against a guaranteed Jominy end-quench hardenability band instead of a narrow chemical analysis, so that heavy sections respond to quenching and tempering consistently from heat to heat.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company supplies AISI 4140H as forged rings, seamless rolled rings, shafts, discs, flanges, blocks, sleeves and bars. Material is EAF + LF + VD melted, ultrasonically tested and certified to EN 10204 3.1 or 3.2. Enquiries: sales@steelforgepieces.com, +86-189-2135-9659.
- Grade designationAISI 4140H, SAE 4140H
- UNS numberH41400
- Steel familyLow-alloy chromium-molybdenum quench and temper steel, 41xx series
- Governing standardsSAE J1268, ASTM A304, ASTM A29/A29M. Forging requirements to ASTM A788
- Nearest equivalents42CrMo4, 1.7225, 42CrMoS4, SCM440, 708M40, 42CrMo
- Typical Q&T strength1150 MPa tensile, 1050 MPa yield, measured on a test piece
- Supplied hardness197 HB maximum annealed, 269 to 341 HB quenched and tempered
- Main usesShafts, gears, rings, valve parts, pressure equipment, drilling and mill components
Technical data reviewed 13 September 2026. Source standards: SAE J1268, ASTM A304, ASTM A255, ASTM A29/A29M.
Difference between AISI 4140 and AISI 4140H
AISI 4140 is ordered against a chemical composition. The mill certifies the analysis and the buyer estimates from it how the steel will respond to quenching. This estimate is reliable in a 60 mm shaft. It is less reliable in a 400 mm forged block, where the centre of the section may not cool quickly enough to transform to martensite.
AISI 4140H is ordered against a published hardenability band. The band sets a minimum and a maximum Rockwell C hardness at each measured position along a Jominy end-quench specimen tested to ASTM A255, and every heat must fall inside it. To make the band achievable in production, ASTM A304 permits 4140H a wider composition range than 4140.
| Item | AISI 4140 | AISI 4140H |
|---|---|---|
| UNS number | G41400 | H41400 |
| Ordered against | Chemical composition | Jominy hardenability band |
| Carbon, C | 0.38–0.43 | 0.37–0.44 |
| Manganese, Mn | 0.75–1.00 | 0.65–1.10 |
| Chromium, Cr | 0.80–1.10 | 0.75–1.20 |
| Molybdenum, Mo | 0.15–0.25 | 0.15–0.25 |
| Silicon, Si | 0.15–0.35 | 0.15–0.35 |
| Governing standard | ASTM A29/A29M, SAE J404 | ASTM A304, SAE J1268 |
| Usual reason to specify | General quench and temper parts | Heavy sections requiring proven through-hardening |
Both grades reach comparable strength after the same quench and temper cycle. The difference lies in the guarantee attached to the order. Where a drawing calls for a core hardness at a defined depth in a section above approximately 150 mm, ordering to ASTM A304 allows that requirement to be verified before heat treatment rather than after it.
Chemical composition of AISI 4140H
| Element | Symbol | Content, wt % | Function |
|---|---|---|---|
| Carbon | C | 0.37–0.44 | Sets the maximum attainable martensite hardness |
| Manganese | Mn | 0.65–1.10 | Increases hardenability, deoxidises, binds sulfur |
| Chromium | Cr | 0.75–1.20 | Increases hardenability and tempering resistance |
| Molybdenum | Mo | 0.15–0.25 | Reduces temper embrittlement, retains strength at temperature |
| Silicon | Si | 0.15–0.35 | Deoxidiser, minor solid solution strengthening |
| Phosphorus | P | 0.035 max | Residual element, limited for toughness |
| Sulfur | S | 0.040 max | Residual element, limited for transverse ductility |
| Iron | Fe | Balance | – |
Jiangyin Jiangnan Metal melts AISI 4140H by electric arc furnace, ladle furnace refining and vacuum degassing. Vacuum degassing reduces hydrogen to a level at which flaking in heavy sections is not a practical risk, and lowers oxygen and inclusion content, which governs ultrasonic acceptance to EN 10228-3 quality class 3 or 4. Where a project restricts residual elements such as Cu, Ni, Sn, As or Sb, or requires sulfur below 0.015 %, the limits should be stated on the enquiry so that they can be applied to the heat.
Mechanical properties of AISI 4140H
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, Rm | 1150 MPa | 167,000 psi |
| Yield strength, Rp0.2 | 1050 MPa | 152,000 psi |
| Elongation at break, A | 17.5 % | 17.5 % |
| Reduction of area, Z | 55 % | 55 % |
| Hardness, Brinell | 341 HB | 341 HB |
| Hardness, Rockwell C | 37 HRC | 37 HRC |
| Hardness, Vickers | 361 HV | 361 HV |
| Modulus of elasticity, E | 205 GPa | 29,700 ksi |
| Shear modulus, G | 80 GPa | 11,600 ksi |
| Bulk modulus, K | 140 GPa | 20,300 ksi |
| Poisson's ratio | 0.29 | 0.29 |
The values in Table 3 are measured on a small quenched and tempered test piece. A 900 mm forged ring will not reach them at mid-wall, because the cooling rate at the centre of the section is considerably slower.
For a production forging, specify the property class required, for example Rm 850 to 1000 MPa with a minimum 40 J at −20 °C, together with the test location and the acceptance standard such as EN 10083-3 practice or an ASTM A668 class. The quench and temper cycle is then designed to meet that requirement.
Physical and thermal properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.85 g/cm³ | 0.284 lb/in³ |
| Thermal expansion, 0–100 °C | 12.2 µm/m·°C | 6.78 µin/in·°F |
| Thermal conductivity | 42.6 W/m·K | 296 BTU·in/hr·ft²·°F |
Approximate weight of a forged ring in kilograms: π ÷ 4 × (OD² − ID²) × height × 7.85 ÷ 1,000,000, with all dimensions in millimetres. This gives a sufficient estimate for budget pricing.
Hardenability and the 4140H hardenability band
Hardenability describes the depth to which hardness extends from the quenched surface. It is a separate property from hardness, which describes the maximum level reached. Hardenability is measured by the Jominy end-quench test to ASTM A255. A 25 mm diameter bar is austenitised, water quenched from one end only, then hardness tested in 1/16 inch steps along its length. Results are reported as J values, so J8 is the hardness at 8/16 inch, or 12.7 mm, from the quenched end.
SAE J1268 and ASTM A304 publish a maximum and a minimum curve for AISI 4140H at each J position, and a heat is acceptable only if its curve falls between them. As an indication, the band at J8 runs from approximately 42 to 54 HRC. The full band table is issued with the material certificate on request.
Each Jominy position corresponds to a cooling rate, and each cooling rate corresponds to a depth in a quenched bar of known diameter. Core hardness in a 300 mm shaft can therefore be predicted from the band before machining begins, which is the main reason the H grade is specified on heavy sections.
Heat treatment of AISI 4140H forgings
| Operation | Temperature | Cooling | Result |
|---|---|---|---|
| Forging | 1200–1230 °C start 850 °C minimum finish | Slow cool, or direct to heat treatment | Worked structure, porosity closed |
| Annealing | 815–845 °C | Furnace cool at approximately 15 °C/h to 480 °C, then air | 197 HB maximum, best machinability |
| Normalising | 870–900 °C | Still air | Refined, uniform grain before Q&T |
| Hardening | 830–860 °C | Oil quench, polymer for large sections | Martensitic, 55 to 58 HRC in thin sections |
| Tempering | 540–650 °C typical | Air, or accelerated through 550–400 °C on heavy sections | Final strength and toughness |
| Stress relieving | 550–650 °C | Slow, controlled | Removes machining and welding stress |
Temper embrittlement
Tempering or slow cooling through approximately 250 to 450 °C reduces impact toughness in chromium-molybdenum steels. Finishing in that range should be avoided, and heavy sections should be cooled quickly through it after the high temper. The molybdenum content of 0.15 to 0.25 % improves resistance to this effect but does not remove it.
Quench cracking
Sharp internal corners, abrupt changes of section and unradiused keyways concentrate stress during oil quenching. A radius of 3 to 5 mm applied to these features at the design stage reduces the risk.
AISI 4140H equivalent grades
| Region and standard | Designation | Material number |
|---|---|---|
| USA, UNS | H41400 | – |
| USA, SAE / AISI | 4140H | – |
| USA, ASTM | A304 grade 4140H | – |
| Europe, EN 10083-3 | 42CrMo4, 42CrMoS4 | 1.7225, 1.7227 |
| Germany, DIN | 42CrMo4 | 1.7225 |
| Japan, JIS G4053 | SCM440, SCM440H | – |
| China, GB/T 3077 | 42CrMo, 42CrMoH | – |
| United Kingdom, BS 970 | 708M40, 708A42, 709M40 | – |
| France, AFNOR | 42CD4, 42CrMo4 | – |
| Italy, UNI | 40CrMo4, 38CrMo4 KB | – |
| Sweden, SS | 2244 | – |
| Russia, GOST | 38KhM | – |
42CrMo4 and 4140H overlap closely in composition, but only the H grade carries a hardenability guarantee, and only 42CrMo4 to EN 10083-3 carries the European mechanical property classes by ruling section. Confirm which document governs the drawing before ordering. Send the specification with the enquiry and we will confirm whether a substitution is acceptable for the part concerned.
AISI 4140H forged product forms and size range
| Product form | Indicative size range | Typical end use |
|---|---|---|
| Seamless rolled rings | OD 200–3000 mm | Bearing races, gear rims, flanged connections, tower sections |
| Forged rings and sleeves | OD 150–2500 mm | Bushings, wear sleeves, cylinder liners |
| Shafts and spindles | Ø 80–1200 mm, length to 8000 mm | Pump and compressor shafts, eccentric shafts, crankshafts |
| Discs, blanks and gear blanks | Ø 200–2500 mm | Gears, pinions, couplings, turbine discs |
| Flanges and tube sheets | Ø 150–3000 mm | Pressure vessels, heat exchangers, piping |
| Blocks and slabs | To drawing | Die holders, valve blocks, machine bases |
| Round bars and hollow bars | Ø 60–800 mm | Machining stock, stems, pins |
| Forged tubes and nozzles | To drawing | Pressure parts, wellhead components |
| Valve bodies and seat rings | To drawing | Ball, gate, globe, check and plug valves |
| Unit weight | 50 kg to 30 t per piece | – |
Forgings are supplied as forged, rough machined with allowance, or finish machined to drawing. The required machining allowance should be stated on the enquiry. On a quenched and tempered part the allowance must be sufficient to remove the decarburised layer.
Testing, inspection and certification
Non-destructive testing
- Ultrasonic testing to EN 10228-3, SEP 1921, or ASTM A388/A388M, with the acceptance class stated on the order
- Magnetic particle inspection to EN 10228-1 or ASTM A275/A275M on machined surfaces
- Dye penetrant inspection to ASTM E165 where specified
Destructive and metallurgical testing
- Heat analysis and product analysis by spectrometer
- Tensile test at room temperature, with elevated-temperature tensile on request
- Charpy V-notch impact at ambient, −20 °C, −40 °C or as specified
- Brinell hardness survey, with the number and location of readings agreed in advance
- Grain size to ASTM E112, macro-etch to ASTM E381, micro examination
Certification
- EN 10204 3.1 material certificate issued with every forging as standard
- EN 10204 3.2 certificate counter-signed by a third-party inspection body on request
- Dimensional report, heat treatment charts and NDT reports supplied with the certificate
- Heat number traceability from melt through to the marked and packed part
Applications of AISI 4140H forgings
Oil, gas and subsea
Wellhead components, Christmas tree bodies, drill collars, subsea connectors, valve bodies and seat rings, and forged blocks for deepwater production systems. For sour service, the applicable NACE MR0175 and ISO 15156 hardness limits must be stated on the order. These limits cap hardness well below the level AISI 4140H can reach, and the quench and temper cycle is designed around them.
Power transmission and rotating equipment
Gear blanks, pinion shafts, turbine and compressor shafts, couplings, gearbox components and eccentric shafts for presses.
Pressure equipment
Forged flanges, tube sheets, shell rings, nozzles and forged tubes for pressure vessels, air receivers, shell and tube heat exchangers, columns, towers and process modules.
Heavy machinery and mills
Rolls, crankshafts, forged wheels, manifolds and drive components for cement mills, sugar mills, concrete mixers, mining equipment, shipbuilding, and pulp and paper plant.
Pumps and fluid handling
Chemical pump shafts, plunger pump components, valve stems and valve blocks for ball, gate, globe, check, plug and strainer assemblies.
Frequently asked questions about AISI 4140H
What is the difference between AISI 4140 and AISI 4140H?
AISI 4140 is ordered against a chemical composition. AISI 4140H is ordered against a guaranteed Jominy end-quench hardenability band. To make the band achievable in production, ASTM A304 allows 4140H a wider composition range: carbon 0.37 to 0.44 % instead of 0.38 to 0.43 %, manganese 0.65 to 1.10 % instead of 0.75 to 1.00 %, and chromium 0.75 to 1.20 % instead of 0.80 to 1.10 %. The H grade is normally specified where a heavy section must be proven to through-harden.
What does the H in 4140H mean?
The H suffix identifies an H-steel, which is supplied to a hardenability requirement verified by the Jominy end-quench test to ASTM A255. Each H grade has a published band of minimum and maximum Rockwell C hardness values at set distances from the quenched end, and every heat must fall inside that band. The H suffix does not indicate higher strength or a different heat treatment.
What is the UNS number for AISI 4140H?
AISI 4140H is UNS H41400. The corresponding non-H grade, AISI 4140, is UNS G41400.
What is the chemical composition of AISI 4140H?
Heat analysis per SAE J1268 and ASTM A304 is carbon 0.37 to 0.44 %, manganese 0.65 to 1.10 %, silicon 0.15 to 0.35 %, chromium 0.75 to 1.20 %, molybdenum 0.15 to 0.25 %, phosphorus 0.035 % maximum, sulfur 0.040 % maximum, balance iron. Jiangyin Jiangnan Metal Co., Ltd. melts 4140H by EAF + LF + VD and reports the actual heat analysis on the EN 10204 3.1 certificate supplied with every forging.
What is AISI 4140H equivalent to in EN, DIN, JIS and GB standards?
The nearest equivalents are 42CrMo4 and material number 1.7225 in EN 10083-3, 42CrMo4 and 42CrMoS4 in DIN, SCM440 and SCM440H in JIS G4053, 42CrMo and 42CrMoH in GB/T 3077, 708M40 and 708A42 in BS 970, 42CD4 in AFNOR and 40CrMo4 in UNI. Hardenability guarantees and permitted element ranges differ between these standards, so the governing specification on the drawing should be confirmed before substitution.
What hardness can AISI 4140H reach?
In thin sections that transform fully to martensite, AISI 4140H reaches approximately 55 to 58 HRC as quenched. The maximum is set by the carbon content of 0.37 to 0.44 %. Forgings are normally supplied quenched and tempered between 28 and 36 HRC, which is approximately 269 to 341 HB, or annealed to 197 HB maximum for machining.
Can AISI 4140H be welded?
AISI 4140H can be welded with controlled procedures. The carbon equivalent is approximately 0.85, so the grade is sensitive to cold cracking. Welding normally requires preheat and interpass temperature of 250 to 350 °C depending on section thickness and joint restraint, low-hydrogen consumables, and post-weld heat treatment at 600 to 680 °C followed by slow cooling. The post-weld temperature must remain below the original tempering temperature so that the parent material retains its properties.
What is the maximum service temperature of AISI 4140H?
AISI 4140H is generally used up to approximately 400 °C. Service temperature should remain at least 30 to 50 °C below the tempering temperature used, otherwise the part continues to temper in service and loses strength. For sustained duty above approximately 450 °C, a creep-resistant grade such as 1.7715 or a nickel alloy is more suitable.
Which forged shapes are available in AISI 4140H?
Jiangyin Jiangnan Metal Co., Ltd. produces AISI 4140H as seamless rolled rings, forged rings, shafts, spindles, eccentric shafts, crankshafts, discs and blanks, flanges, tube sheets, blocks, slabs, sleeves, bushings, hollow bars, round bars, gear blanks, valve bodies, valve seat rings and forged tubes. All shapes are produced to customer drawing. A drawing or a sketch with outline dimensions is sufficient for a quotation.
What certification and testing are supplied with 4140H forgings?
Every AISI 4140H forging is supplied with a material certificate to EN 10204 3.1, or to EN 10204 3.2 counter-signed by a third-party inspection body when required. Standard testing covers heat and product chemical analysis, tensile, impact and hardness testing, and ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388/A388M as specified on the order. Magnetic particle inspection, grain size determination and macro or micro examination can be added.
How do I get a quotation for AISI 4140H forgings?
Send a drawing or outline dimensions, the quantity, the required delivery condition such as annealed, normalised or quenched and tempered, the acceptance standard and the certificate level to sales@steelforgepieces.com, or call +86-189-2135-9659. Jiangyin Jiangnan Metal Co., Ltd. normally returns a price and lead time within one working day. Where a drawing is not available, outline dimensions and unit weight are sufficient for pricing.
Request a quotation for AISI 4140H forgings
Information required
- Drawing, or outline dimensions and unit weight
- Quantity and required delivery date
- Delivery condition and required properties
- Acceptance standard and certificate level
- Destination port
Jiangyin Jiangnan Metal Co., Ltd.
AddressNo.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone+86-189-2135-9659