The ageing condition: aged at about 900 °F (480 °C). H900 gives the highest strength; H1025 and H1150 trade some strength for toughness.

Yes, it is martensitic and magnetic.

Can 17-4 PH be machined?

Yes, usually in the solution-treated or an over-aged condition, then aged to final strength with very little size change.

17-4 PH stainless steel: conditions, strength and uses

17-4 PH is a precipitation-hardening stainless steel (also called SS 630) with chromium, nickel and copper. A simple low-temperature ageing treatment makes it very strong while it keeps corrosion resistance close to 304, so it is used for pump shafts, valve parts and aerospace components.

Quick facts

Type: Martensitic precipitation-hardening stainless steel
Main alloys: About 15–17.5% Cr, 3–5% Ni, 3–5% Cu
Hardness: About 40–44 HRC in H900; lower in H1025–H1150
Corrosion resistance: Good, close to SS 304 in many conditions
Heat treatment: Solution treat, then age at about 480–620 °C
Size change on ageing: Small

Common conditions

Condition	Ageing temperature	Character
H900	About 480 °C	Highest strength and hardness, lower toughness
H1025	About 550 °C	High strength, better toughness
H1150	About 620 °C	Lower strength, best toughness and stress-corrosion resistance

Name the condition on the drawing (e.g. 17-4 PH H1025).

Equivalent grades

Standard	Grade
AISI / UNS	630 / S17400
EN / W.Nr.	X5CrNiCuNb16-4, 1.4542
Cast version	CB7Cu-1

Typical uses

Pump and propeller shafts
Valve stems, seats and trim
Aerospace and defence fittings
Moulds and dies for corrosive plastics
Food and chemical machinery parts

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Questions

What does H900 mean?: The ageing condition: aged at about 900 °F (480 °C). H900 gives the highest strength; H1025 and H1150 trade some strength for toughness.
Is 17-4 PH magnetic?: Yes, it is martensitic and magnetic.
Can 17-4 PH be machined?: Yes, usually in the solution-treated or an over-aged condition, then aged to final strength with very little size change.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 9 October 2026.