SNCM220 Forgings: JIS G4103 Ni-Cr-Mo Case-Hardening Steel
Forged rings, flanges, discs, shafts, gear blanks and bars in SNCM220, made to drawing at our open-die forging works in Jiangyin, China.
SNCM220 is a low-carbon nickel-chromium-molybdenum case-hardening steel specified in the Japanese standard JIS G 4103. It contains 0.17-0.23 % C, 0.40-0.70 % Ni, 0.40-0.65 % Cr and 0.15-0.30 % Mo. After carburising and hardening it gives a wear-resistant surface of about 58-62 HRC over a tough core, which is why it is specified for gears, drive shafts, bearing races, pins and bushings. Its closest international equivalents are AISI 8620, EN 20NiCrMo2-2 (1.6523), BS 805M20 and GB 20CrNiMo.
Jiangyin Jiangnan Metal Co., Ltd. supplies SNCM220 as open-die forgings and seamless rolled rings, EAF + LF + VD melted, ultrasonically tested to EN 10228-3 or ASTM A388, and certified to EN 10204 3.1 or 3.2.
- Standard
- JIS G 4103
- Steel type
- Ni-Cr-Mo carburising
- Carbon
- 0.17-0.23 %
- Case hardness
- 58-62 HRC
- Tensile (Q+T)
- min. 833 MPa
- Closest US grade
- AISI 8620
1. What is SNCM220 steel?
SNCM220 belongs to the SNCM series, the nickel-chromium-molybdenum steels for machine structural use covered by JIS G 4103. Within that series the 220 designation marks a low-carbon carburising grade, not a through-hardening grade such as SNCM439.
Carbon is held below 0.23 %, so the steel cannot be hardened much in its as-supplied condition. Hardness is produced at the surface by carburising. Carbon is diffused into the outer 0.5-1.5 mm at 900-930 °C, then the part is quenched so that the enriched case transforms to martensite while the low-carbon core stays tough. Nickel and molybdenum raise hardenability and core toughness. Chromium refines the carbide structure in the case.
Note on the standard. SNCM220 is sometimes listed as a chromium-molybdenum steel under JIS G 4105. That is wrong. JIS G 4105 covers the SCM series (SCM435, SCM440). SNCM220 is a nickel-bearing case-hardening steel under JIS G 4103, and enquiries and order documents should cite JIS G 4103.
2. SNCM220 chemical composition
Composition limits for SNCM220 to JIS G 4103, ladle analysis, weight %:
| Element | Symbol | Min % | Max % | Role in the steel |
|---|---|---|---|---|
| Carbon | C | 0.17 | 0.23 | Keeps the core tough and weldable; case carbon is added by carburising |
| Silicon | Si | 0.15 | 0.35 | Deoxidiser, slight solid-solution strengthening |
| Manganese | Mn | 0.60 | 0.90 | Hardenability, combines with sulphur |
| Phosphorus | P | - | 0.030 | Residual, limited to avoid temper embrittlement |
| Sulphur | S | - | 0.030 | Residual, limited for transverse toughness |
| Nickel | Ni | 0.40 | 0.70 | Core toughness and low-temperature impact strength |
| Chromium | Cr | 0.40 | 0.65 | Hardenability and case wear resistance |
| Molybdenum | Mo | 0.15 | 0.30 | Hardenability, resists temper embrittlement |
| Copper | Cu | - | 0.30 | Residual element |
Figures are the limits set by the standard and are given for reference. The governing document for any delivered lot is the EN 10204 3.1 or 3.2 certificate issued with it.
3. SNCM220 mechanical and physical properties
Values for SNCM220 in the quenched and tempered condition, measured on a standard test piece. Rows marked typical are commonly published reference figures rather than limits set by the standard.
| Property | Requirement (metric) | Requirement (JIS units) |
|---|---|---|
| Tensile strength, Rm | min. 833 MPa | min. 85 kgf/mm² |
| Yield point, ReH (typical) | approx. 588 MPa | approx. 60 kgf/mm² |
| Elongation, A | min. 17 % | min. 17 % |
| Reduction of area, Z | min. 40 % | min. 40 % |
| Charpy impact value | min. approx. 59 J/cm² | min. 6 kgf·m/cm² |
| Hardness, quenched and tempered | 248-341 HB | |
| Hardness, annealed delivery (typical) | max. 250 HB | |
| Case hardness after carburising | 58-62 HRC typical | |
| Typical case depth | 0.5-1.5 mm, to specification | |
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ (7.8-7.9) |
| Modulus of elasticity | 200-215 GPa |
| Poisson's ratio | approx. 0.29 |
| Melting range | approx. 1380-1530 °C |
| Machinability, annealed (1212 = 100 %) | approx. 60-65 % |
| Magnetic | Yes, ferromagnetic |
4. SNCM220 equivalent grades
SNCM220 sits in the 8620 / 20NiCrMo2 family of carburising steels. The table lists the designations normally accepted as equivalent, with our product page for each:
| Country or system | Standard | Grade | Notes |
|---|---|---|---|
| Japan | JIS G 4103 | SNCM220 | Reference grade on this page |
| USA | ASTM A29 / SAE J404 | AISI 8620 (UNS G86200) | Closest equivalent, most widely traded |
| USA, H-band | SAE J1268 | AISI 8620H | Specified when Jominy hardenability is controlled |
| Europe | EN 10084 | 20NiCrMo2-2 | Material number 1.6523 |
| Germany | DIN 17210 | 21NiCrMo2 | Former DIN designation of 1.6523 |
| United Kingdom | BS 970 | 805M20 | Former EN362 |
| France | AFNOR NF A35-551 | 20NCD2 | - |
| China | GB/T 3077 | 20CrNiMo | Widely available domestically |
| USA, near grades | SAE J404 | 8615, 8617, 8622 | Same family, different carbon band |
Equivalent here means generally interchangeable in engineering use. Chemistry bands and test requirements differ slightly between standards. Where a drawing names one standard, we buy and certify to that standard.
SNCM220 compared with neighbouring grades
| Grade | Type | Carbon | Typical choice for |
|---|---|---|---|
| SNCM220 | Case hardening | 0.17-0.23 % | A hard wear surface over a tough core: gears, pins, races |
| 18CrNiMo7-6 | Case hardening | 0.15-0.21 % | Heavier sections or higher core strength |
| 17CrNiMo6 | Case hardening | 0.15-0.20 % | Large gear rings with deep case depth |
| SNCM439 | Through hardening | 0.36-0.43 % | Uniform strength through the section, no case |
| AISI 4140 / 42CrMo4 | Through hardening | 0.38-0.43 % | General quenched and tempered shafts without carburising |
5. SNCM220 heat treatment and forging
| Operation | Temperature | Cooling | Result |
|---|---|---|---|
| Forging | Start 1150-1200 °C, finish above 850 °C | Slow cool, covered or in furnace | Refined wrought grain flow |
| Normalising | 850-900 °C | Air | Uniform structure before machining |
| Annealing | 830-870 °C | Furnace | Max. 250 HB, best machinability |
| Carburising | 900-930 °C | Per case-depth cycle | Carbon-enriched surface layer |
| Core hardening | 870-900 °C | Oil | Tough martensitic core |
| Case refining and hardening | 780-830 °C | Oil | Fine-grained hard case |
| Tempering after carburising | 150-200 °C | Air | Relieves stress, retains 58-62 HRC |
| Quench and temper, uncarburised | 870-900 °C, temper 550-650 °C | Oil, then air | 248-341 HB, min. 833 MPa |
| Stress relief | 550-650 °C | Furnace to 300 °C, then air | After heavy machining or welding |
Cycles above are starting points. Soak times depend on section thickness, commonly one hour per 25 mm of ruling section, and on the specified case depth.
Machining and welding
- Machining. Best carried out in the annealed or normalised condition, before carburising. Rough machine, stress relieve, then finish machine.
- Masking. Surfaces that must stay soft can be copper plated or coated with stop-off paint before carburising, or left with a machining allowance that is removed after the case is applied.
- Welding. Readily weldable in the uncarburised condition. Preheat 150-250 °C on heavy sections, use low-hydrogen consumables, stress relieve after welding at 550-650 °C. Do not weld onto a carburised surface.
- Grinding. Carburised and hardened surfaces are normally finish ground. Keep grinding gentle to avoid grinding burns and re-tempering of the case.
6. SNCM220 forged products we manufacture
All items are produced to customer drawing or to a rough-machined size list. Forms supplied in SNCM220:
- Seamless rolled rings and forged rings: bearing races, gear rims, slewing ring blanks
- Forged flanges, discs, blanks and forging disks
- Forged round bars, shafts, spindles and eccentric shafts
- Gear blanks, pinion blanks and sprocket blanks
- Sleeves, bushings, hubs and couplings
- Hollow forged pipes, forged tubes and tube sheets
- Rough-machined and finish-machined forged components
| Product form | Size range | Weight per piece |
|---|---|---|
| Seamless rolled rings | OD 200-3000 mm, wall 30-500 mm, height up to 1000 mm | 10-8000 kg |
| Forged discs and blanks | OD up to 2500 mm, thickness 50-800 mm | 20-10000 kg |
| Round bars and shafts | Dia. 80-800 mm, length up to 6000 mm | 20-12000 kg |
| Sleeves and hollow forgings | OD 150-1500 mm, ID from 80 mm | 10-6000 kg |
| Flanges | OD up to 2000 mm | 5-5000 kg |
Sizes outside these ranges are often still possible. Send the drawing and we will confirm feasibility before quoting.
7. Manufacturing route, testing and certification
Every SNCM220 forging follows the same controlled route:
- Melting. EAF + LF + VD (electric arc furnace, ladle furnace, vacuum degassing) for low gas content and clean inclusion ratings.
- Forging. Open-die forging or ring rolling with a controlled forging ratio to close porosity and develop grain flow along the principal stress direction.
- Heat treatment. Normalised, annealed, or quenched and tempered as ordered. Carburising performed to the specified case depth and hardness.
- Machining. As-forged with allowance, rough machined, or finish machined.
- Inspection. Dimensional check, chemical analysis, mechanical testing, hardness survey and NDT.
| Scope | Standard or detail |
|---|---|
| Ultrasonic testing (UT) | EN 10228-3, SEP 1921, ASTM A388 |
| Magnetic particle inspection (MT) | ASTM E709, EN 10228-1, on request |
| Chemical analysis | Ladle and product analysis |
| Mechanical testing | Tensile, impact including -20 °C and -46 °C, hardness |
| Metallurgical checks | Grain size, case depth traverse, Jominy hardenability |
| Material certificate | EN 10204 3.1, or 3.2 witnessed by TÜV, SGS, BV, LR or DNV |
8. Typical applications for SNCM220 forgings
| Industry | Typical SNCM220 parts |
|---|---|
| Power transmission and gearboxes | Gear blanks, pinion blanks, ring gears, shafts, splined couplings |
| Automotive and heavy vehicle | Differential gears, drive shafts, bearing races, king pins |
| Bearings | Case-hardened inner and outer rings, roller blanks |
| Oil, gas and offshore | Subsea connector components, wear sleeves, wellhead running tools |
| Pumps, compressors and valves | Rotor shafts, wear rings, valve stems, plungers |
| Mining, cement and sugar mills | Mill pinions, idler shafts, crusher components |
| Wind and marine | Gearbox rings, carrier shafts, thruster components |
| General machinery | Sprockets, cams, bushings, hardened wear pads |
SNCM220 is chosen where a surface has to resist rolling or sliding contact while the body of the part still has to take shock loading.
9. Frequently asked questions about SNCM220
What is SNCM220 steel?
SNCM220 is a low-carbon nickel-chromium-molybdenum case-hardening (carburising) steel specified in Japanese standard JIS G 4103. It contains 0.17-0.23 % C, 0.40-0.70 % Ni, 0.40-0.65 % Cr and 0.15-0.30 % Mo. After carburising and hardening it gives a hard, wear-resistant surface of about 58-62 HRC over a tough core, which is why it is specified for gears, shafts, bearing components and pins.
Is SNCM220 the same as AISI 8620?
They are close equivalents rather than identical grades. SNCM220 and AISI/SAE 8620 (UNS G86200) share the same Ni-Cr-Mo carburising design and overlap in every alloying element, so they are normally interchangeable for gear and shaft work. SNCM220 allows a slightly wider chromium band, 0.40-0.65 % against 0.40-0.60 %. If your drawing calls out one standard, order to that standard and we will certify to it.
Which standard covers SNCM220, JIS G4103 or JIS G4105?
JIS G 4103 covers SNCM220. JIS G 4103 is the standard for nickel-chromium-molybdenum steels for machine structural use, which is the SNCM series. JIS G 4105 covers chromium-molybdenum steels, the SCM series such as SCM435 and SCM440. Data sheets that place SNCM220 under G 4105 are incorrect.
What are the mechanical properties of SNCM220?
In the quenched and tempered condition JIS G 4103 requires a minimum tensile strength of 85 kgf/mm² (about 833 MPa), minimum elongation of 17 %, minimum reduction of area of 40 %, a minimum impact value of 6 kgf·m/cm² (about 59 J/cm²) and a hardness of 248-341 HB. The yield point is typically around 60 kgf/mm², about 588 MPa. After carburising, the case usually reaches 58-62 HRC while the core stays tough.
What is the equivalent of SNCM220 in EN, GB and BS standards?
The usual equivalents are AISI/SAE 8620 (USA), 20NiCrMo2-2 and 21NiCrMo2, material number 1.6523 (EN and DIN), 805M20 (BS 970, former EN362), 20NCD2 (AFNOR) and 20CrNiMo (GB/T 3077, China). AISI 8615, 8617 and 8622 are near neighbours in the same family, differing mainly in carbon.
How is SNCM220 heat treated?
Normalise at 850-900 °C and air cool. Anneal at 830-870 °C and furnace cool to a maximum of about 250 HB. Carburise at 900-930 °C to the required case depth, core harden from 870-900 °C in oil, case refine from 780-830 °C in oil, then temper at 150-200 °C. Where the part is used without carburising, quench from 870-900 °C in oil and temper at 550-650 °C.
Can SNCM220 be welded?
Yes, in the uncarburised condition. Carbon of 0.17-0.23 % gives a carbon equivalent low enough for normal welding practice, usually with preheat of 150-250 °C on heavy sections, low-hydrogen consumables and stress relief after welding at 550-650 °C. Carburised surfaces should not be welded because the high-carbon case is crack sensitive.
What forged shapes can be supplied in SNCM220?
Jiangyin Jiangnan Metal Co., Ltd. supplies SNCM220 as open-die forgings and seamless rolled rings: forged rings, flanges, discs and blanks, round bars, shafts and spindles, gear and pinion blanks, sleeves and bushings, hollow forged pipes and tube sheets. Parts are made to drawing or to a rough-machined size list.
What testing and certification is supplied with SNCM220 forgings?
Standard scope is chemical analysis, mechanical testing, hardness survey and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Certification is issued to EN 10204 3.1, or EN 10204 3.2 with third-party witness by bodies such as TÜV, SGS, BV, Lloyd's Register or DNV. Magnetic particle inspection, grain size, Jominy hardenability and low-temperature impact testing are available on request.
What information is needed to quote SNCM220 forgings?
Send the grade, the finished or rough-machined dimensions or a drawing in PDF or STEP, the quantity, the delivery condition (as-forged, normalised, annealed, quenched and tempered, or carburised), the required certificate level and any NDT or third-party requirement. Enquiries go to sales@steelforgepieces.com.
10. About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory based in Jiangyin, Jiangsu Province, China. The company forges rings, flanges, discs, shafts, bars, gear blanks and hollow sections in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, and supplies them with EN 10204 3.1 or 3.2 certification. SNCM220 and its equivalents, AISI 8620, 20NiCrMo2-2, 1.6523, 805M20 and 20CrNiMo, are among the case-hardening grades produced to customer drawing.
- Company Jiangyin Jiangnan Metal Co., Ltd.
- Business Open-die forging factory, seamless rolled rings
- Address No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Phone 0086-189-2135-9659
- Email sales@steelforgepieces.com
- Website www.steelforgepieces.com
Request a quotation for SNCM220 forgings
Send a drawing or a size list and we will come back with price, weight and lead time.
Standards referenced on this page
- JIS G 4103, nickel chromium molybdenum steels for machine structural use
- ASTM A29/A29M, steel bars, carbon and alloy, hot-wrought, general requirements
- EN 10084, case hardening steels, technical delivery conditions
- EN 10204, metallic products, types of inspection documents
- EN 10228-3, SEP 1921 and ASTM A388, ultrasonic testing of steel forgings
- GB/T 3077, alloy structural steels (China)
- BS 970, wrought steels for mechanical and allied engineering purposes
Page compiled and reviewed by the technical team of Jiangyin Jiangnan Metal Co., Ltd. Last reviewed . Property data is given for engineering guidance. The mill certificate issued with each delivery is the governing document.