40CrNiMo hot rolled steel round bars

40CrNiMoA steel is used after quenching and tempering, and is used to manufacture important parts requiring good plasticity, high strength and large size. For example, heavy-duty shafts in heavy-duty machines, steam turbine shafts with diameters greater than 250 mm, blades, transmissions, fasteners, crankshafts, gears, etc., can also be used for rotor shafts and blades operating at temperatures exceeding 400 °C.
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.

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

 

40CrNiMoA Alloy Steel Mechanical Properties

• Yield strength: ≥ 835 MPa
• Tensile strength: ≥ 980 MPa
• Elongation: ≥12%
• Rate of reduction in area: ≥55%
• Impact absorbing energy: ≥ 78 J
• Material Brinell Hardness: ≤ 269 (Annealed or high temperature tempered steel rod)
• Sample size: 25mm

Heat treatment specification

• First quenching heating temperature: 850 °C (Quenchant– oil)
• Tempering heating temperature: 600 °C (Quenchant– water, oil)

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.