Material Properties

Standard specifications for heat-treatable, alloy, and free-cutting steels

Category: Machined steel

Document reference: ISO 683-2:2012

Document title: Heat-treatable steels, alloy steels and free-cutting steels

This classification covers the primary steels used in mechanical engineering and heavy machinery fabrication. Through quenching and tempering, these materials achieve a precise balance of high tensile strength, core toughness, and surface wear resistance. Certain grades in this group are specifically designed as free-cutting steels, meaning they are optimized for rapid, clean CNC machining without sacrificing structural integrity.

Mechanical properties of alloy heat-treatable steels in quenched and tempered condition (+QT). Values specify proof strength Re and tensile strength Rm separated by product form (round bars vs flat products).

Round bars — governing diameter (d)

Steel Grade	d ≤ 16 mm		16 < d ≤ 40 mm		40 < d ≤ 63 mm		63 < d ≤ 100 mm		100 < d ≤ 160 mm		160 < d ≤ 250 mm
Steel Grade	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)
34Cr4	700	900	590	800	460	700	460	700	-	-	-	-
34CrS4	700	900	590	800	460	700	460	700	-	-	-	-
37Cr4	750	950	630	850	510	750	510	750	-	-	-	-
37CrS4	750	950	630	850	510	750	510	750	-	-	-	-
41Cr4	800	1000	660	900	560	800	560	800	-	-	-	-
41CrS4	800	1000	660	900	560	800	560	800	-	-	-	-
25CrMo4	700	900	600	800	450	700	450	700	-	-	-	-
25CrMoS4	700	900	600	800	450	700	450	700	-	-	-	-
34CrMo4	800	1000	650	900	550	800	550	800	500	750	450	700
34CrMoS4	800	1000	650	900	550	800	550	800	500	750	450	700
42CrMo4	900	1100	750	1000	650	900	650	900	550	800	500	750
42CrMoS4	900	1100	750	1000	650	900	650	900	550	800	500	750
50CrMo4	900	1100	780	1000	700	900	700	900	600	850	550	800
41CrNiMo2	840	1000	740	900	640	800	640	800	540	750	-	-
41CrNiMoS2	840	1000	740	900	640	800	640	800	540	750	-	-
51CrV4	900	1100	800	1000	700	900	700	900	650	850	600	800
36CrNiMo4	900	1100	800	1000	700	900	700	900	600	800	-	-
34CrNiMo6	1000	1200	900	1100	800	1000	800	1000	700	900	600	800
30CrNiMo8	850	1030	850	1030	800	980	800	980	800	980	750	930
20MnB5	700	900	600	750	-	-	-	-	-	-	-	-
30MnB5	800	1000	650	800	-	-	-	-	-	-	-	-
39MnB5	900	1100	700	850	-	-	-	-	-	-	-	-
27MnCrB5-2	800	1000	750	900	700	800	-	-	-	-	-	-
33MnCrB5-2	850	1050	800	950	750	900	-	-	-	-	-	-
39MnCrB6-2	900	1100	850	1050	800	1000	-	-	-	-	-	-

Flat plates — governing thickness (t)

Steel Grade	t ≤ 8 mm		8 < t ≤ 20 mm		20 < t ≤ 35 mm		35 < t ≤ 60 mm		60 < t ≤ 100 mm		100 < t ≤ 160 mm
Steel Grade	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)	fy (MPa)	fu (MPa)
34Cr4	700	900	590	800	460	700	460	700	-	-	-	-
34CrS4	700	900	590	800	460	700	460	700	-	-	-	-
37Cr4	750	950	630	850	510	750	510	750	-	-	-	-
37CrS4	750	950	630	850	510	750	510	750	-	-	-	-
41Cr4	800	1000	660	900	560	800	560	800	-	-	-	-
41CrS4	800	1000	660	900	560	800	560	800	-	-	-	-
25CrMo4	700	900	600	800	450	700	450	700	-	-	-	-
25CrMoS4	700	900	600	800	450	700	450	700	-	-	-	-
34CrMo4	800	1000	650	900	550	800	550	800	500	750	450	700
34CrMoS4	800	1000	650	900	550	800	550	800	500	750	450	700
42CrMo4	900	1100	750	1000	650	900	650	900	550	800	500	750
42CrMoS4	900	1100	750	1000	650	900	650	900	550	800	500	750
50CrMo4	900	1100	780	1000	700	900	700	900	600	850	550	800
41CrNiMo2	840	1000	740	900	640	800	640	800	540	750	-	-
41CrNiMoS2	840	1000	740	900	640	800	640	800	540	750	-	-
51CrV4	900	1100	800	1000	700	900	700	900	650	850	600	800
36CrNiMo4	900	1100	800	1000	700	900	700	900	600	800	-	-
34CrNiMo6	1000	1200	900	1100	800	1000	800	1000	700	900	600	800
30CrNiMo8	850	1030	850	1030	800	980	800	980	800	980	750	930
20MnB5	700	900	600	750	-	-	-	-	-	-	-	-
30MnB5	800	1000	650	800	-	-	-	-	-	-	-	-
39MnB5	900	1100	700	850	-	-	-	-	-	-	-	-
27MnCrB5-2	800	1000	750	900	700	800	-	-	-	-	-	-
33MnCrB5-2	850	1050	800	950	750	900	-	-	-	-	-	-
39MnCrB6-2	900	1100	850	1050	800	1000	-	-	-	-	-	-

Note: The properties presented on this page are based on standard specifications, which should be consulted for compliance. The information presented here is for reference purposes only.

Standard specifications for heat-treatable, alloy, and free-cutting steels

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