The differences between 17-4PH and 304 stainless steel are as follows: 17-4PH focuses on high strength (precipitation-hardening type), while 304 emphasizes corrosion resistance and general-purpose use (austenitic type), leading to distinct application scenarios.
Mechanical Strength: After aging treatment, 17-4PH has a tensile strength of 1000–1400 MPa, more than twice that of 304 (around 515 MPa). Its hardness and yield strength are also higher, making it suitable for high-strength load-bearing applications.
Corrosion Resistance: 304 has superior corrosion resistance, especially against organic acids and chloride ions, making it ideal for humid or acidic/alkaline environments. 17-4PH performs well in atmospheric and freshwater conditions but is less resistant to chloride-induced pitting than 304.
Microstructure and Heat Treatment: 17-4PH is a martensitic precipitation-hardening steel that requires “solution treatment + aging” to strengthen. 304 is an austenitic steel, non-magnetic, and cannot be strengthened by heat treatment—only by cold working.
Machining and Welding:304 has better cold workability and weldability, requiring no post-processing after forming. 17-4PH is machinable in the solution-treated state, but welding requires post-aging to restore strength.
Application Comparison:
17-4PH: Aerospace components, high-strength bolts, gears, high-pressure valves in petrochemical industry, medical implants—applications demanding high strength.
304: Food equipment, chemical containers, architectural decoration, home appliances, piping—applications prioritizing corrosion resistance and versatility.