708M40 Steel Bar-BS 970

708M40 steel belongs to the CrMo series alloy steel in the BS970 standard, and its mechanical properties need to be guaranteed.

Similar to 4140 steel, after heat treatment, 708M40 steel has excellent comprehensive properties: high strength, high hardness and excellent wear resistance and impact resistance.

708M40 steel is usually used in the quenched and tempered condition, the most common one is 708M40T(Hardenss:248-302HBW).

708M40 STEEL CHEMICAL COMPOSITION

Grade	C	Si	Mn	P	S	Cr	Mo
708M40	0.36-0.44	0.1-0.4	0.7-1.0	≤0.035	≤0.04	0.9-1.2	0.15-0.25

708M40 STEEL RELATED STANDARD & EQUIVALENT GRADE

China/GB 3077: 42CrMoA

USA/ASTM A29:4140

Europe/EN 10083: 42CrMo4

Japan/JIS G4105:SCM440

IS 708M40 STEEL SAME AS EN19 STEEL?

In fact, they both belong to the BS970 standard. The difference is that EN19 is from the 1955 version, while 708M40 is from the 1991 version.The difference in versions also leads to certain differences in elements between them. We can compare them item by item in the table below.

Grade	C	Si	Mn	P	S	Cr	Mo
708M40	0.36-0.44	0.1-0.4	0.7-1.0	≤0.035	≤0.04	0.9-1.2	0.15-0.25
EN19	0.35-0.45	0.10-0.35	0.5-0.8	≤0.05	≤0.05	0.9-1.5	0.2-0.4

708M40 STEEL FORGING

Initial Forging Temperature：1150-1200℃
Final Forging Temperature：>850℃
Forging Ratio：above 4:1
Cooling Method After Forged:708M40 has a certain sensitivity to white spots. For small sizes, burying in a sand pit for slow cooling after forging is the recommended practice.For large sizes, annealing heat treatment after forging is more recommended.