Post Tensioning Bar
Courtesy of Macalloy
Grade 17-4 PH (1.4542) is perhaps the most common example of the precipitation hardening stainless grades. It combines good corrosion resistance with high strength and good impact toughness.
Approximate Composition – 16% Cr, 4% Ni, 4% Cu plus Nb (niobium) (Exact composition ranges vary between EN and ASTM standards).
This grade combines the following characteristics:
• Good corrosion resistance (just below that of 304)
• High hardness and strength
• Controlled balance of mechanical properties by ageing (precipitation hardening)
• Improved toughness compared to 431 including use at sub-zero temperatures for the softer conditions
• Thermal expansion comparable to carbon steel
• Easier to weld than martensitic grades like 420 and 431
17-4 PH develops its high strength from the precipitation of copper particles in its martensitic matrix. It comes in various conditions denoted by H plus ageing temperature in °F, for example H900, H1025 etc. The higher the ageing temperature, the lower is the strength and the higher are the ductility and toughness. The minimum 0.2% PS varies from 520 MPa to 1170 MPa depending on the condition. The combination of high strength and good corrosion resistance finds uses in:
Drive shafts, bearings, gears, hydraulic rams, valve stems, load cells, bridge bearings, tensioning systems, golf clubs, quick release pins, fasteners, aerospace, medical devices, food processing, conveying equipment, fall arrest systems
17-4 PH is the natural choice of high strength, corrosion resistant steel particularly where standard martensitic grades like 431 aren’t quite good enough.