Alloy 17-4ph is a precipitation hardening martensitic stainless steel with cu & nb/cb additions. 17-4 ph combines high strength ,hardness and corrosion resistance. Mechanical properties can be optimized with heat treatment,Very High yield strength up to 1100-1300 Mpa can be achieved. ALLOY 17-4 PH 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.
Corrosion Resistance Alloy 17-4 PH withstands corrosive attacks better than any of the standard hardenable stainless steels and is comparable to Alloy 304 in most media. If there are potential risks of stress corrosion cracking, the higher aging temperatures then must be selected over 1022°F (550°C), preferably 1094°F (590°C). 1022°F (550°C) is the optimum tempering temperature in chloride media. 1094°F (590°C) is the optimum tempering temperature in H2S media. The alloy is subject to crevice or pitting attack if exposed to stagnant seawater for any length of time. It is corrosion resistant in some chemical, petroleum, paper, dairy and food processing industries (equivalent to 304L grade).
Heat Treatment Martensitic transformation ?Indicative values?Ms : 266°F (130°C)?Mf : 86°F (30°C) Solution annealing?1925°F+ /-50°F (1050°C +/-25°C)-30 min up to 1 hour. ?air cooling / oil quenching below 76°F (25°C) Aging / Tempering?The highest mechanical properties are obtained with the following heat treatment : 896°F (480°C)-1 hour-air cooling. Higher ductilities are obtained when using higher aging temperatures up to 1148°F (620°C). Image1.gif Hardness/Temperature tempered for 4 hours after austenitizing at 1904°F (1040°C) for 30 min quenched 212°F/sec (100°C/sec).
Welding Alloy 17-4 PH can be welded by the following welding processes: SMAW, GTAW, PAW and GMAW. SAW should not be used without preliminary testing (to check freedom of cracks and toughness of the weld metal). Due to a ferrite delta primary type of solidification, the hot cracking risk of the weld metal or the HAZ is reduced. Generally, no preheating must be done and interpass temperature must be limited to 248°F (120°C). The better toughness is obtained in the weld after a complete heat treatment (solution annealing + precipitation hardening). Due to the martensitic microstructure, a low oxygen content in the weld metal is preferable to increase ductility and toughness. To avoid cold cracking, the introduction of hydrogen in the weld must be limited. Alloy 17-4 PH can be welded with homogeneous filler metals such as E 630 (AWS A5.4) electrodes and ER 630 (AWS A5.9) wires. Austenitic filler material can be used when the mechanical properties of 17-4 PH steel are not required in the weld and, in this case, no post-weld heat treatment must be applied.
Machining Alloy 17-4 PH can be machined in both solution treated and precipitation hardened conditions. Machining condition may vary according to the hardness of the material. High speed steel tools or preferably carbide tools with standard lubrification are normally used. If very stringent tolerances are required, it is necessary to take into account the dimensional changes during heat treatment.
|Standard||ALLOY 17-4 PH|
|Melting Point||1440 °C (2552 °F)|
|Yield Strength (0.2%Offset)||Psi-155000-175000
|ALLOY 17-4 PH|