300M ALLOY STEEL

300M is a low alloy, vacuum melted, steel of very high strength. Essentially it is a modified AISI 4340 steel with silicon, vanadium and slightly greater carbon and molybdenum content than 4340. 300M alloy steel (AMS 6257, AMS 6417, AMS 6419) has a very good combination of strength (1900-2100 MPA after final heat treatment), toughness, fatigue strength and good ductility. 300M is a through hardening alloy.

Specific Gravity

7.83 g/cm3

Typical Applications

Related Specifications

Aircraft Landing Gear

Driveshafts

High Strength bolts

Gears

AMS 6257

AMS 6417

AMS 6419

BS S155

BMS 7-26

MTL 1201

MIL S 8844

Chemical Composition (Wt %)

	C	Si	Mn	P	S	S+P	Cr	Mo	Ni	V
Min	0.39	1.5	0.6	–	–	–	0.7	0.3	1.65	0.05
Max	0.44	1.8	0.9	0.015	0.015	0.025	0.95	0.45	2	0.10

Typical Mechanical Properties

	0.2% Proof Stress	Tensile Strength		Elongation	Reduction of area
	MPA	MPA		%	%
	Min	Min	Max	Min	Min
Longitudinal	1550	1900	2100	8	30
Transverse	1550	1900	2100	5	20

Hardness after Heat Treatment

534 – 601 HB

52 – 55 HRC

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