17-4 Stainless Steel
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17-4 Stainless Steel

SAE Type 630 stainless steel (more commonly known as 17-4 PH, or simply 17-4; also known as UNS 17400) is a grade of martensitic precipitation hardened stainless steel. It contains approximately 15-17.5% chromium and 3-5% nickel, as well as 3-5% copper.[1] The name comes from the chemical makeup which is approximately 17% chromium and 4% nickel.


17-4 can be heat treated to high levels of strength and hardness, and features corrosion resistance[1] and machinability[2] comparable to austenitic 304 stainless. Being martensitic, 17-4 is magnetic.

17-4 is capable of being hardened up to approximately 44 Rc when heat treated to condition H900.[1]

Overaging (aging beyond the peak strength condition) improves resistance to stress corrosion cracking.[3]


Uses for 17-4 stainless steel include components which require high hardness and/or corrosion resistance at temperatures of up to 600 °F (316 °C).[2] Specific applications for 17-4 include the petroleum and chemical industries, as well as use in aircraft parts.[1]


Proportion by mass (%)[1][2]
C Mn P S Si Cr Ni Cu Nb, Ta
0.07 max. 1.0 max. 0.04 max. 0.03 max. 1.0 max. 15.0-17.5 3.0-5.0 3.0-5.0 0.15-0.45


  1. ^ a b c d e "Type 630; 17 Cr-4 Ni; UNS 17400" (PDF). Outokumpu.com. Archived from the original (PDF) on December 23, 2015. Retrieved 2016.
  2. ^ a b c "North American Stainless - Long Products Stainless Steel Grade Sheet" (PDF). North American Stainless. Retrieved 2016.
  3. ^ "Stress Corrosion Properties of High-Strength Precipitation Hardening Stainless Steels in 3.5% Aqueous Sodium Chloride Solution" (PDF). Retrieved 2016.

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  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.



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