65Mn hot rolled steel round bars

65Mn steel is a Chinese GB standard spring steel grade, Manganese (Mn) improves hardenability, so the strength, hardness, elasticity and hardenability are higher than that of 65# steel, but it has overheat sensitivity and temper brittleness. Water quenching tends to form cracks. The annealed state has good machinability, low cold deformation plasticity, and poor weldability.
65Mn high carbon steel is mainly used in the manufacture of various small-section flat springs, round springs, clockwork, etc. It can also be used to manufacture spring rings, valve springs, shock absorbers, clutch reeds and brake springs.

Chemical Composition

The table below lists 65Mn high carbon steel chemical composition based on heat analysis.

Chemical Composition, %
Standard	Grade	C	Si	Mn	P, ≤	S, ≤	Cr, ≤	Ni, ≤	Cu, ≤
GB/T 1222	65Mn	0.62-0.70	0.17-0.37	0.90-1.20	0.030	0.030	0.25	0.35	0.25

65Mn Material Properties

Density: 7.85 g/cm3

		Mechanical Properties
Standard	Grade	Tensile Strength, MPa, ≥	Yield Strength, MPa, ≥	Elongation, %, ≥	Reduction in Area, %, ≥	Brinell Hardness, HBW, ≤
GB/T 1222	65Mn	980	785	8.0	30	302

Notes: Bars with a diameter and side length of not more than 80 mm and flat steels with a thickness of not more than 40 mm.

Heat Treatment Specification

		Heat Treatment
Standard	Grade	Quenching temperature, °C	Quenching medium	Tempering temperature, °C
GB/T 1222	65Mn	830 ± 20	Oil	540 ± 20

Annealing process: Annealing temperature (860 ± 10) °C, heat preservation for 45-60min, furnace cooling to (750 ± 10) °C, heat preservation for 3-3.5h, and furnace cooling to 650-660 °C, then cooling out of the furnace or slow cooling in a heat preservation pit.