Alloy Information for PH Grades 17-4PH


Chemical Analysis
Mn Manganese
1.00 max
P Phosphorus
0.04 max
S Sulfur
0.03 max
Si Silicon
Cr Chromium
15.0 – 17.5
Ni Nickel
3.0 – 5.0
Cu Copper
3.0 – 5.0
Cd + Ta Cadmium + Tantulum
0.15 – 0.45

General Characteristics

17 – 4 PH steel is a martensitic precipitation or age-hardening stainless steel that combines high strength and hardness with excellent corrosion resistance. It may be age hardened by a single- step low- temperature treatment.

Alloy 17-4PH is a versatile precipitation-hardening steel showing excellent strength and corrosion-resisting characteristics. It is readily machinable, weldable and formable.

Applications of AISI / SAE 4340

This grade of steel is used for a variety of applications including oil field valve parts, chemical process equipment, forged aircraft fittings, fasteners and pump shafts, gears, nuclear reactor parts and jet engine parts.

Forging 4340 Alloy Steel

Forging of this grade should be carried out between 2150/2200 º F (1180/1200 º C) and 1850 º F (1010 º C.) For optimum grain size and mechanical properties, forgings should be air cooled to below 90 º F (32 º C) prior to further processing. Forgings must be solution treated prior to hardening.

Heat Treatment

Type 17 – 4 PH alloy is hardened by heating solution-treated material, condition A, to between 900 º F (480 º C) and 1150 º F (620 º C) for one to four hours, depending upon the temperature, then air cooling.

Solution Treatment

Heat at 1900 º F (1040 º C) for 30 minutes and cool to below 90 º F (32 º C) to allow complete transformation to martensite. Sections less than 3” may be quenched in a suitable liquid while those sections over 3” should be rapidly air cooled. Parts should not be used in the solution – treated condition due to possible problems with stress corrosion cracking.

Age Hardening

For condition H900 heat solution-treated material at 900 º F (480 º C) for 1 hour and air cool.

For conditions H925, H1025, H1075, H1100, H1150: heat solution-treated material at appropriate temperature ± 15ºF (± 8ºC) for 4 hours and air cool.


17 – 4 PH grade is readily machinable in both the solution-treated and various age-hardened conditions. It machines similar to stainless 304 in the solution-treated condition. The machinability improves as the hardening temperature increases.


17 – 4 PH grade can be satisfactorily welded by the shielded fusion and resistance welding processes. Oxyacetylene welding is not recommended since carbon pick up may occur in the weld. If a filler metal is required a 17-4PH type welding rod should be used to provide welds with base-metal properties. If high strength is not required an austenitic stainless filler metal is satisfactory.

Welding in the solution-treated condition is normally satisfactory, but if high welding stresses are a possibility it may be best to weld in the overaged (H1150) condition. Preheating is not normally required to prevent cracking.

If welded in the solution-treated condition, 17-4PH alloy may be aged to the desired strength level after welding, but the optimum strength-ductility-corrosion resistance combination is obtained by solution treating the welded part before aging. Welding in the overaged conditioned must be followed by solution treating then aging.

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