17-4PH Stainless Steel Mechanical Properties: H900 to H1150 Conditions

How 17-4PH Gets Its Mechanical Properties

17-4PH, UNS S17400, is a martensitic precipitation-hardening stainless steel. After solution treatment the alloy is delivered in Condition A, a soft and formable state, and a subsequent aging step precipitates copper-rich particles in the martensitic matrix. The aging temperature sets the final balance of properties: lower aging temperatures give the highest strength, while higher temperatures trade some strength for ductility and impact toughness. This article lists the mechanical properties published for bar, wire and forgings in AMS 5643, for sheet, strip and plate in AMS 5604, and for plate in the same treatment family, so that a designer can specify a condition with known numbers.

Condition codes such as H900 and H1150 state the aging temperature in degrees Fahrenheit: H900 is aged at 900 ℃F (482 ℃), H925 at 925 ℃F (496 ℃), H1025 at 1025 ℃F (552 ℃), H1075 at 1075 ℃F (579 ℃), H1100 at 1100 ℃F (593 ℃) and H1150 at 1150 ℃F (621 ℃). Aging time is one hour followed by air cooling. The suffix M denotes the minimum-tensile H1150 treatment and D the double-aged H1150 treatment; both improve stress-corrosion cracking resistance compared with single aging. Each condition also controls hardness, so the code fully describes the expected mechanical state.

Mechanical Properties of 17-4PH Bar (AMS 5643)

		0.2% yield strength (ksi / MPa)	Elongation % (2 in. / 4D)
	–	–	–	–	39 max
H900	190 / 1310	170 / 1172	10	40	40–47
H925	170 / 1172	155 / 1069	10	44	38–45
H1025	155 / 1069	145 / 1000	12	45	34–42
H1075	145 / 1000	125 / 862	13	44	31–38
H1100	140 / 965	115 / 793	14	45	30–37
H1150	135 / 931	105 / 724	16	50	28–37

Values follow AMS 5643 and are minimums for the size ranges covered by the specification. MPa conversions are rounded.

Mechanical Properties of 17-4PH Sheet, Strip and Plate (AMS 5604)

Sheet, strip and plate are covered by AMS 5604. Strength minimums match the bar values, while minimum elongation is lower because thin material is tested in the transverse direction; hardness ranges are the same as for bar.

		0.2% yield strength (ksi / MPa)	Elongation % (2 in., sheet under 0.1874 in. thick)
	–	–	–	38 max
H900	190 / 1310	170 / 1172	5	40–47
H925	170 / 1172	155 / 1069	5	38–45
H1025	155 / 1069	145 / 1000	5	35–42
H1075	145 / 1000	125 / 862	5	33–39
H1100	140 / 965	115 / 793	5	32–38
H1150	135 / 931	105 / 724	8	28–37

Published plate data at H900 show 190,000 psi tensile, 170,000 psi yield, 10% elongation, 40% reduction of area, 388 Brinell hardness and 40 Rockwell C; at H1150 the same source lists 135,000 psi tensile, 105,000 psi yield, 16% elongation, 50% reduction of area, 277 Brinell and 28 Rockwell C. The overaged treatments extend the range further: H1150-M offers a minimum tensile strength of 115,000 psi with 18% elongation and 55% reduction of area, and H1150-D gives 125,000 psi minimum tensile with 16% elongation and 50% reduction of area, with Brinell hardness from about 255 up to 311 for the double-aged condition.

Use H900 when maximum strength and hardness are required and some loss of ductility is acceptable, for example shafts, pins, fasteners and wear parts. Move to H1025–H1100 for a middle ground between strength and toughness. Choose H1150, H1150-M or H1150-D for impact-loaded components and for applications where stress-corrosion cracking resistance is critical. Parts machined in Condition A and aged afterwards will see a small dimensional change during aging, so finishing allowances should follow the same practice used for other precipitation-hardening grades.

What is the tensile strength of 17-4PH at H900? Minimum 190 ksi (1310 MPa), with 0.2% yield strength of 170 ksi (1172 MPa), 10% elongation and 40% reduction of area for bar per AMS 5643.

How does H1150 compare with H900? H1150 trades about 55 ksi of tensile strength for roughly double the minimum elongation and better impact toughness, which is why it is preferred for dynamic loads.

Sheet, strip and plate are tested in the transverse direction with a shorter gauge, so minimum elongation values of 5% at H900 are lower than the 10% shown for longitudinally tested bar.

What hardness can be expected at H900? Rockwell C 40–47 for bar and sheet; plate values are commonly reported as 388 Brinell and 40 Rockwell C.

What do H1150-M and H1150-D mean? M and D are modified H1150 treatments, minimum-tensile and double-aged, that improve stress-corrosion cracking resistance with slightly reduced strength.

Can 17-4PH be supplied in Condition A? Yes, in solution-annealed Condition A with hardness up to about 38–39 Rockwell C, so fabricators can machine the part before aging.

Which specifications govern 17-4PH? Bar, wire and forgings are covered by AMS 5643 and ASTM A564 Type 630; sheet, strip and plate by AMS 5604; the European designation is EN 10088-3, 1.4542 (X5CrNiCuNb16-4).