40CrNiMoA, 4340, and SNCM439 are all types of high-strength alloy steel that contain similar chemical compositions, making them somewhat interchangeable for certain applications.
Chrome-Moly low alloy steel series contains 0.5% – 9% Cr and 0.5% – 1% Mo and lower than 0.20% carbon. 40CrNiMoA, 4340 and SNCM439 are the low alloy chromoly steel materials from the different standards. 40CrNiMoA steel is a Chinese standard chromium-molybdenum high strength steel with good hardenability and toughness. 4340 and SNCM439 are standards from American and Japanese respectively. In most situation they can be alternative materials, unless there is a special note or used for special purpose. Their differences are mainly existed in chemical elements, details showed as follows:
| Standards | GB | AISI | JIS |
|---|---|---|---|
| Material | 40CrNiMoA | 4340 | SNCM439（SNCM8） |
| C | 0.37~0.44 | 0.38~0.43 | 0.36~0.43 |
| Si | 0.17~0.37 | 0.15~0.35 | 0.15~0.35 |
| Mn | 0.50~0.80 | 0.60~0.80 | 0.60~0.90 |
| P | ≤0.025 | ≤0.035 | ≤0.030 |
| S | ≤0.025 | ≤0.040 | ≤0.030 |
| Cr | 0.60~0.90 | 0.70~0.90 | 0.60~1.00 |
| Ni | 1.25~1.65 | 1.65~2.00 | 1.60~2.00 |
| Mo | 0.15~0.25 | 0.20~0.30 | 0.15~0.30 |
It was used where require high tensile and good wear-resistance property parts such as heavy-duty axles, shafts, heavy-duty gears, spindles, pins, studs, bolts, couplings, sprockets, pinions, torsion bars, connecting rods. These high tensile alloy steel has been widely used in the areas such as petrol chemical industry, automotive, steam power equipment and other high temperature services.
| C(％) | Si(％) | Mn(％) | P(％) | S(％) | Cr(％) | Ni(％) | Cu(％) | Mo(％) |
|---|---|---|---|---|---|---|---|---|
| 0.37～0.4 | 0.17 ~ 0.37 | 0.50 ~ 0.80 | ≤0.025 | ≤0.025 | 0.60～0.90 | 1.25 ~ 1.65 | ≤0.25 | 0.15 ~ 0.25 |
| Yield Strength Rp0.2(MPa) |
Tensile Strength Rm(MPa) |
Impact Energy AKV(J) |
Elongation A(%) |
Impact toughness | Reduction of area ψ (%): |
Hardness |
|---|---|---|---|---|---|---|
| ≥ 835(85) | ≥ 980(100) | ≥ 78 | ≥ 12 | ≥ 98(10) | ≥ 55 | ≤ 269 HBW |
SNCM439 is a nickel-chromium-molybdenum tempered alloy structure steel. SNCM439 boasts superior strength, hardness, wear resistance and toughness.
Its hardenability is slightly higher than that of 40Cr steel, with a critical quenching diameter in oil of up to 18 ~ 33mm. It is an ideal replacement for 40Cr steel. Once normalised, it displays excellent machinability, cold drawing, rolling, tapping, forging and heat treatment characteristics. At high temperatures, the decarburisation tendency and quenching deformation tendency are minimal, although the tempering property is not as robust as that of 40Cr steel. SNCM439 steel rod is typically employed in tempered conditions and can withstand temperatures between -20 and 425°C.
SNCM439 is widely used in high toughness alloy structural steel.
| EU/EN | INTER/ISO | USA/AISI | JAPAN/JIS | GERMANY/DIN | CHINA/GB | FRANCE/AFNOR | ENGLAND/BS |
|---|---|---|---|---|---|---|---|
| -- | -- | 4340 9840 |
SNCM439 | -- | 40CrNiMoA 45CrNiMoVA |
-- | -- |
*This comparison table is for reference only. The standards and grades of various countries have slightly different chemical compositions. Please refer to the database for details.*
The chemical composition of SNCM439 is as follows:
| C(%) | Si(%) | Mn(%) | P(%) | S(%) | Ni(%) | Cr(%) | Mo(%) | Cu(%) |
|---|---|---|---|---|---|---|---|---|
| 0.36 - 0.43 | 0.15 - 0.35 | 0.6 - 0.9 | 0 ≦ 0.03 | 0 ≦ 0.03 | 1.6 - 2.0 | 0.6 - 1.0 | 0.15 - 0.30 | 0 ≦ 0.3 |
| Property | Value |
|---|---|
| Tensile strength (kgf/mm²) | ≧100 |
| Yield strength (kgf/mm²) | ≧90 |
| Elongation (%) | ≧16 |
| Cross section reduction rate (%) | ≧45 |
| Impact value (J/cm²) | ≧7 |
| Hardness (Hb) | 293 - 352 |
SNCM439 has excellent hardenability, and it can be heat-treated to achieve high hardness and strength. It is commonly used in the manufacturing of gears, shafts, and other components where high strength and resistance to wear and fatigue are required.
Compared to other types of steel, SNCM439 offers superior mechanical performance at higher temperatures, making it an ideal material for use in high-temperature applications.
Overall, SNCM439 is a highly durable and versatile alloy steel that is widely used in various industries, including automotive, aerospace, marine, and construction.
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