Alloy 17-4 PH is a precipitation hardening martensitic stainless steel with Cu and Nb/Cb additions. The grade combines high strength, hardness (up to 572°F / 300°C), and corrosion resistance.
Mechanical properties can be optimized with heat treatment. Very high yield strength up to 1100-1300 MPa (160-190 ksi) can be achieved.
The grade should not be used at temperatures above 572°F (300°C) or at very low temperatures. It has adequate resistance to atmospheric corrosion or in diluted acids or salts where its corrosion resistance is equivalent to Alloy 304 or 430.
Grade specifications for grade 630 stainless steels
Solution treatment (Condition A) — Grade 630 stainless steels are heated at 1040°C for 0.5 h, then air-cooled to 30°C. Small sections of these grades can be oil quenched.
Hardening — Grade 630 stainless steels are age-hardened at low temperatures to achieve the required mechanical properties. During the process, superficial discoloration occurs followed by shrinkage at 0.10% for condition H1150, and 0.05% for condition H900.
Why choose 17-4ph stainless steel
Reasons for choosing 17/4PH (630)
431 Has higher toughness than 17/4PH. Better availability in some sizes.
Higher corrosion resistance of 316 to resist more severe environments, but with much lower strength than 17/4PH.
Much better corrosion resistance than 17/4PH, with a lower strength (but not as low as 316).
Grade 630 stainless steels are martensitic stainless steels that are precipitation hardened to achieve excellent mechanical properties. These steel achieve high strength and hardness following heat treatment. The heat and corrosion resistance of grade 630 are similar to that of grade 304 steels. This grades is also commonly referred to as grade 17-4PH.
One of the key benefits of this grade is that it is available in solution treated conditions, at which they can be easily machined and age-hardened to attain high strength. The age treatment of grade 630 is carried out at low temperatures, to avoid significant distortion. Therefore, this grade is used for applications such as the manufacture of long shafts that do not require re-straightening after heat treatment.