AISI 4140

Typical analysis

C	Mn	P	Si	Mo	Cr
0.38 - 0.43	0.75 - 1.00	max. 0.035	max. 0.04	0.15 - 0.35	0.8 - 1.10

This chromium molybdenum alloy steel is oil hardening steel of relatively high hardening ability and is among the most widely used versatile machinery steels. The chromium content provides good hardness penetration and the molybdenum imparts uniformity of hardness and high strength. This grade is especially suitable for forging as it has self scaling characteristics it responds readily to heat treatment and is comparatively easy to machine in the heat treated condition. In the heat treated condition tensile strengths of 170,000 PSI. for small section and 140,000 PSI for larger section are attended all combined with good ductility and resistance to shock. This steel resists creep in temperature up to 540 ^o C and maintain its properties even after long exposure at these relatively high working temperatures. The wear resistance can be considerably increased by flame hardening or induction hardening.   A very interesting and powerful surface hardening process could be a combinations of induction hardening with nirtiding obtaining a real improvement of surface.  

Typical applications. 

Shafts, gears, bolts, couplings, spindles, tool holders, sprockets, hydraulic machinery shafts, oil industry drill collars,Kelly bars, tools joints, so on. 

Mechanical properties 
 
1. Annealed conditions 

	unit	1"	2 - 1/4"	4 - 1/2"	7 - 3/4"
Tensile strength	PSI	98,000	101,500	100,000	100,000
Yield strength	PSI	61,000	62,000	57,000	58,500
Elongation	%	23	26	25	21
Reduction in area	%	54	55	56	59
Hardness	HB	197	212	202	197

2. Heat treated and stress relieved

	unit	3 - 1/4"	4 - 1/2"	6 - 1/4"	8"
Tensile strength	PSI	156,165	145,870	136,590	139,780
Yield strength	PSI	141,085	126,005	111,070	114,695
Elongation	%	17.1	16	18.1	15.5
Reduction in area	%	55.9	49.8	55.1	46.9
Hardness	HB	321	331	311	321

3. Heat treated at HRC 22 max. for sour gas.