What is AISI 4130 steel?
The definition first, then the numbers behind it.
AISI 4130 is a low-alloy chromium-molybdenum steel. The aerospace trade calls it chromoly. In the SAE designation, 41 identifies the Cr-Mo family and 30 gives the nominal carbon content of 0.30%. Chromium raises hardenability and tempering resistance. Molybdenum reduces temper embrittlement and holds strength at elevated temperature.
Carbon near 0.30% is what makes the grade weldable. Grades carrying 0.40% carbon, such as AISI 4140, need tighter preheat control and are harder to fabricate after heat treatment. Engineers specify 4130 where a part has to be welded, formed or machined after heat treatment, and move to 4140 or 42CrMo4 where a heavy section has to reach higher strength.
Jiangyin Jiangnan Metal Co., Ltd. melts AISI 4130 by the EAF + LF + VD route (electric arc furnace, ladle furnace refining, vacuum degassing) and forges it to ASTM A29/A29M. Vacuum degassing keeps hydrogen low enough to avoid flaking in heavy sections. Ask for the hydrogen result on any 4130 forging above roughly 300 mm ruling section.
Selection guide. For weldability, good toughness and moderate strength, use AISI 4130. For higher strength in a section above roughly 200 mm, use AISI 4140 or 42CrMo4. For corrosion resistance, 4130 is the wrong family; look at 17-4PH, F51 duplex or a nickel alloy.
Chemical composition of AISI 4130
To SAE J404 and ASTM A29/A29M, weight %, balance iron.
| Element | Symbol | Min % | Max % | Role in the grade |
|---|---|---|---|---|
| Carbon | C | 0.28 | 0.33 | Sets strength and hardenability, kept low for weldability |
| Silicon | Si | 0.15 | 0.35 | Deoxidiser, raises yield strength slightly |
| Manganese | Mn | 0.40 | 0.60 | Hardenability, ties up sulphur |
| Chromium | Cr | 0.80 | 1.10 | Hardenability and tempering resistance |
| Molybdenum | Mo | 0.15 | 0.25 | Resists temper embrittlement, hot strength |
| Phosphorus | P | - | 0.035 | Residual, embrittles grain boundaries |
| Sulphur | S | - | 0.040 | Residual, lowers transverse ductility |
| Iron | Fe | Balance | - | |
Residual elements are set by mill practice rather than by the base specification. Jiangyin Jiangnan Metal normally holds Ni at 0.25% max and Cu at 0.35% max. P and S can be restricted further, typically P 0.020% max and S 0.015% max, for sour service or for low-temperature impact values. State the restriction on the enquiry. It has to be built into the heat and cannot be screened in afterwards.
Mechanical properties of AISI 4130
Values follow the heat treatment condition and the section size, not the grade alone.
| Condition | Tensile strength | Yield, 0.2% proof | Elongation | Reduction of area | Hardness |
|---|---|---|---|---|---|
| Annealed | 560 MPa (81 ksi) | 360 MPa (52 ksi) | 28% | 56% | 156 HB |
| Normalised | 670 MPa (97 ksi) | 435 MPa (63 ksi) | 25% | 60% | 197 HB |
| Quenched & tempered | 655-896 MPa (95-130 ksi) | 517-758 MPa (75-110 ksi) | 20% min | 40% min | 217-235 HB (18-22 HRC) |
Why forgings are supplied at 18-22 HRC
ANSI/NACE MR0175 and ISO 15156-2 cap carbon and low-alloy steels at 22 HRC for service in environments containing H2S, because harder martensite is prone to sulphide stress cracking. Forgings for wellhead equipment, subsea trees, choke bodies and sour-service valves have to fall inside that limit. Jiangyin Jiangnan Metal takes hardness surveys on the finished forging as well as on the test coupon.
Impact testing is available on request. For 4130 quenched and tempered to this hardness range, Charpy V-notch values of 40 to 60 J at -29 degrees C are normally achievable. Confirm the test temperature and the acceptance values before the heat is melted, because low-temperature toughness constrains both the chemistry and the tempering practice.
Physical properties of AISI 4130
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.85 g/cm3 | 0.284 lb/in3 |
| Modulus of elasticity | 205 GPa | 29,700 ksi |
| Shear modulus | 80 GPa | 11,600 ksi |
| Poisson's ratio | 0.29 | |
| Thermal conductivity | 42.7 W/m.K | 296 BTU.in/h.ft2.F |
| Specific heat, 0-100 C | 477 J/kg.K | 0.114 BTU/lb.F |
| Thermal expansion, 20-100 C | 12.2 um/m.C | 6.8 uin/in.F |
| Electrical resistivity | 0.223 uohm.m | - |
| Melting range | 1432 C | 2610 F |
To estimate the weight of a rolled ring, calculate pi/4 x (OD squared minus ID squared) x height x 7.85 g/cm3, then add the machining allowance on every surface. Send the machined drawing and Jiangyin Jiangnan Metal returns the rough forging weight with the quotation.
AISI 4130 equivalent grades
Chemically close, but the acceptance criteria differ. Name the governing standard on the purchase order.
| Country or body | Standard | Grade designation |
|---|---|---|
| USA, SAE / AISI | SAE J404 | 4130 |
| USA, UNS | UNS | G41300 |
| USA, ASTM | A29/A29M, A322, A331, A519 | 4130 |
| USA, aerospace | AMS 6345, 6346, 6348, 6350, 6370, 6371 | 4130 |
| Germany | DIN EN 10083-3, W.-Nr. | 25CrMo4, 1.7218 |
| International | ISO 683-2 | 25CrMo4 |
| Japan | JIS G4105 | SCM430 |
| China | GB/T 3077 | 30CrMo |
| France | AFNOR NF A35-552 | 25CD4 |
| United Kingdom | BS | CDS 110, 1717 CDS 110 |
| Russia | GOST 4543 | 30KhMA |
Jiangyin Jiangnan Metal forges all of these designations from the same 4130-family chemistry, certified to whichever standard the order names. Where a drawing calls out 25CrMo4 but the inspection body works to ASTM, ask for a dual certificate. That prevents a rejection at incoming inspection caused only by a difference in nomenclature.
Forging and heat treatment of AISI 4130
| Operation | Temperature | Cooling | Result |
|---|---|---|---|
| Forging | Heat to 1150-1200 C, finish above 850 C | Slow cool in ash | Wrought grain flow following the part contour |
| Full annealing | 830-860 C | Furnace cool at 15 C/h max to 600 C | 156-197 HB, best machinability |
| Normalising | 870-900 C | Still air | Uniform fine grain before quenching |
| Hardening | 860-880 C | Oil quench, water for thin sections | Martensitic structure |
| Tempering | 480-650 C | Air | Higher temperature gives lower hardness, 217-235 HB near the top of the range |
| Stress relieving | 550-650 C | Slow furnace cool | Removes machining and welding stress |
Welding AISI 4130
AISI 4130 welds more readily than most low-alloy steels, and that is often the reason it gets specified. For sections above roughly 10 mm, preheat to 150-260 degrees C, use low-hydrogen consumables, and apply post-weld heat treatment at 590-675 degrees C. Omitting post-weld heat treatment on a hardened 4130 weldment is a common cause of hydrogen cracking in the heat-affected zone.
AISI 4130 forging capability at Jiangyin Jiangnan Metal
Open-die forging and ring rolling at Zhouzhuang Town, Jiangyin, Jiangsu Province, China.
Piece weight
20 kg to 20,000 kg per forging in AISI 4130.
Seamless rolled rings
200 mm to 4,000 mm outside diameter, wall and height to drawing.
Shafts and bars
Up to 12 m long, forged and rough-machined to your allowance.
Discs and blocks
Up to 2,500 mm diameter, rectangular blocks to drawing.
Melting route
EAF + LF + VD, with ESR available for critical sections.
Machining
As-forged, rough-machined or finish-machined to print.
Product forms we forge in AISI 4130
Seamless rolled rings, forged rings, forged discs and disks, shafts and eccentric shafts, spindles, forged components, flanges, round bars, blocks, sleeves and bushings, hollow forgings and forged pipe, tube sheets, valve bodies, bonnets, seat rings and stems, gear blanks, crankshafts, nozzles, manifolds, forged rolls and wheels.
Where AISI 4130 forgings are used
Listed by industry, with the forms most often ordered in each.
| Industry | Typical AISI 4130 forgings | Reason for the grade |
|---|---|---|
| Oil and gas, subsea | Wellhead and Christmas tree bodies, subsea connectors, valve blocks, crossovers | Fits the 22 HRC sour-service limit in NACE MR0175 |
| Valves | Ball, gate, globe, check and plug valve bodies, seat rings, stems, bonnets | Takes weld overlay on seats, good pressure-boundary toughness |
| Pressure vessels and heat exchangers | Shells, tube sheets, forged flanges, nozzles, air receivers | Weldable at code-acceptable strength |
| Aerospace and defence | Structural fittings, landing gear components, tube assemblies | The original chromoly aircraft steel, covered by AMS specs |
| Power transmission | Gear blanks, turbine and compressor shafts, gearbox parts | Even hardenability in medium sections |
| Pumps and compressors | Rolled rings, plunger and chemical pump shafts, casings | Fatigue strength at a machinable hardness |
| Process and chemical plant | Columns, towers, silos, preheaters, crystalliser parts, process modules | Fabricable and weldable after forging |
| Heavy machinery and marine | Forged rolls, wheels, manifolds, mill and mixer parts, shipbuilding components | Toughness under shock loading |
Testing, NDT and certification
Every AISI 4130 forging leaves Jiangyin with an EN 10204 3.1 mill certificate as standard, showing the heat number, ladle analysis, heat treatment record and mechanical results. EN 10204 3.2 certification countersigned by TUV, SGS, BV, Lloyd's Register or DNV is available where the end client requires a third-party witness.
| Test | Standard | Notes |
|---|---|---|
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 | State the acceptance class, for example SEP 1921 Class C/c, on the order |
| Magnetic particle | ASTM E709, EN 10228-1 | Surface and near-surface indications |
| Chemical analysis | ASTM E415, optical emission spectrometer | Ladle and product analysis |
| Tensile and impact | ASTM A370, EN ISO 6892-1, ISO 148-1 | Charpy V-notch at ambient or low temperature |
| Hardness survey | ASTM E10, ASTM E18 | Multiple points on the finished forging for NACE work |
| Grain size | ASTM E112 | Typically ASTM 5 or finer |
| Dimensional | Per drawing | Report issued with the certificate |
AISI 4130 vs AISI 4140: which to specify
The two grades sit next to each other in the same Cr-Mo family and are often confused on drawings.
| Criterion | AISI 4130 | AISI 4140 |
|---|---|---|
| Nominal carbon | 0.30% | 0.40% |
| Chromium and molybdenum | 0.80-1.10% Cr, 0.15-0.25% Mo | 0.80-1.10% Cr, 0.15-0.25% Mo |
| Tensile, quenched and tempered | 655-896 MPa | 850-1,100 MPa typical |
| Hardenability | Mild, suits sections under about 150 mm | Deeper, suits heavy sections |
| Weldability | Good, the main reason to choose it | Limited, needs strict preheat and PWHT |
| Toughness at a given strength | Higher | Lower |
| European equivalent | 25CrMo4, 1.7218 | 42CrMo4, 1.7225 |
| Typical use | Weldable pressure parts, sour-service bodies, aircraft structures | Highly stressed shafts, gears, heavy rings |
Jiangyin Jiangnan Metal forges both grades on the same equipment. Send the drawing with the duty and the required section size and we will say which grade reaches your acceptance values at lower cost. See also AISI 4140 forgings, 42CrMo4 and SCM440.
AISI 4130 frequently asked questions
Questions buyers and design engineers send us most often.
What is AISI 4130 steel?
AISI 4130 is a low-alloy chromium-molybdenum steel, often called chromoly, with about 0.30% carbon, 0.95% chromium and 0.20% molybdenum. It offers good weldability, easy machining and mild hardenability, and is used for aircraft structures, pressure vessels, valve bodies and oilfield components. Jiangyin Jiangnan Metal Co., Ltd. supplies AISI 4130 as open-die forgings and seamless rolled rings to ASTM A29/A29M.
What is the chemical composition of AISI 4130?
To SAE J404 and ASTM A29/A29M: carbon 0.28 to 0.33%, manganese 0.40 to 0.60%, silicon 0.15 to 0.35%, chromium 0.80 to 1.10%, molybdenum 0.15 to 0.25%, phosphorus 0.035% max, sulphur 0.040% max, balance iron. Jiangyin Jiangnan Metal melts AISI 4130 by EAF + LF + VD and reports the actual heat analysis on every EN 10204 3.1 certificate.
What is AISI 4130 equivalent to?
AISI 4130 is equivalent to UNS G41300 in the USA, 25CrMo4 or 1.7218 in Germany and EN 10083-3, SCM430 in Japan, 30CrMo in China, 25CD4 in France, CDS 110 in the UK and 30KhMA in Russia. These are close chemical equivalents, but their mechanical acceptance criteria differ, so the purchase order should state which standard governs.
Is AISI 4130 stronger than AISI 4140?
No. AISI 4140 is stronger and more hardenable because it carries about 0.40% carbon against 0.30% for 4130. AISI 4130 is chosen where weldability and toughness matter more than peak strength, or where the section is thin enough that the deeper hardenability of 4140 buys nothing. Above roughly 200 mm ruling section, Jiangyin Jiangnan Metal usually recommends 4140 or 42CrMo4.
Can AISI 4130 be welded?
Yes. It is one of the more weldable low-alloy steels, which is why aircraft tube frames and pressure vessel nozzles use it. Sections above roughly 10 mm need preheat of 150 to 260 degrees C and post-weld heat treatment at 590 to 675 degrees C to avoid hydrogen cracking in the heat-affected zone. Low-hydrogen consumables should always be used.
Is AISI 4130 suitable for sour service under NACE MR0175?
Yes, provided hardness is controlled. ANSI/NACE MR0175 and ISO 15156-2 limit carbon and low-alloy steels to 22 HRC maximum in service containing H2S. Jiangyin Jiangnan Metal supplies AISI 4130 forgings quenched and tempered to 18 to 22 HRC, or 217 to 235 HB, for this window, with hardness surveys taken on the finished forging as well as on the test coupon.
What size AISI 4130 forgings can you supply?
From 20 kg to 20,000 kg per piece, with seamless rolled rings from 200 mm to 4,000 mm outside diameter and forged bars and shafts up to 12 metres long. Send the drawing, or the finished dimensions plus the machining allowance, to sales@steelforgepieces.com and we will confirm feasibility and rough forging weight.
In what heat treatment condition are AISI 4130 forgings supplied?
Annealed, normalised, normalised and tempered, or quenched and tempered, depending on the order. Quenched and tempered is the usual condition for valve bodies, wellhead components and pressure parts. Where the order does not state a condition, Jiangyin Jiangnan Metal asks before starting production rather than assuming one.
What certificates and testing come with AISI 4130 forgings?
Every forging ships with an EN 10204 3.1 mill certificate, or EN 10204 3.2 countersigned by TUV, SGS, BV, Lloyd's or DNV on request. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 at the acceptance class stated on the order. Magnetic particle, hardness, impact and grain size testing can be added.
What is the density and weight of AISI 4130?
The density of AISI 4130 is 7.85 g/cm3, or 0.284 lb/in3. For a ring, calculate pi/4 x (OD squared minus ID squared) x height x 7.85 g/cm3 and add the machining allowance on every surface. Send the machined drawing and we will calculate the rough forging weight for you.
What is the minimum order quantity and lead time for AISI 4130 forgings?
There is no fixed minimum order quantity. Jiangyin Jiangnan Metal takes single-piece prototypes as well as series production. Lead time runs 25 to 45 days from order confirmation where AISI 4130 billet is available in the required size, and longer where a dedicated heat has to be melted.
Does AISI 4130 rust?
Yes. AISI 4130 is a low-alloy steel, not a stainless steel, and its 0.95% chromium sits well below the level needed for passivity. It corrodes in humid air and needs paint, phosphating, oil, plating or weld overlay in service. Where corrosion resistance is the driver, look at 17-4PH or Inconel 625 forgings instead.
About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone, WhatsApp and WeChat: +86 189 2135 9659, or 0086-189-2135-9659
Email: sales@steelforgepieces.com
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging manufacturer in Jiangyin, Jiangsu Province, China, in the Yangtze River delta forging cluster about 150 km from the Port of Shanghai. The plant produces forged rings, seamless rolled rings, discs, shafts, flanges, blocks, sleeves and near-net-shape components in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys. Customers are in oil and gas, valve manufacturing, power generation, petrochemical, marine and heavy machinery.
Technical content prepared by the Jiangyin Jiangnan Metal engineering team. Last reviewed . Values on this page are nominal and given for guidance. The mill certificate for the heat supplied always governs.