17-4PH Stainless Steel
17-4PH stainless steel is a high strength, highly corrosion-resistant alloy containing nickel, chromium and molybdenum in addition to copper, and is capable of being heat-treated to extremely high levels of mechanical properties. It is commonly used in the medical and aerospace industries due to its superior strength and resilience. 17-4PH stainless steel is also known as Type 630, which is the grade designation of the American Iron and Steel Institute (AISI).
Physical Characteristics
17-4PH stainless steel has a high tensile strength of at least 140 ksi (965 MPa). It is also highly resistant to corrosion. It has a low magnetic permeability and high electrical resistivity. Its Youngs modulus is 29 million psi (200 GPa).
Chemical Characteristics
The chemicall composition of 17-4PH stainless steel is as follows: 17.0-19.0% chromium, 3.0-5.0% nickel, 3.0-5.0% copper, 0.05-0.15% iron, 0.07-0.15% manganese, 0.045-0.45% silicon, 0.03-0.08% carbon, and 0.15-0.45% molybdenum.
Heat Treatment
17-4PH stainless steel can be hardened through two different heat treatments. The first is a solution heat treatment, where the material is heated to between 1850°F (1010°C) and 1950°F (1065°C) for one hour and then quickly cooled in air, water, or oil. The second option is age-hardening, which involves heating the material to 1350°F (732°C) for four hours and then cooling it quickly followed by a slower cooling rate over a period of 24 hours. Both treatments will result in the material achieving its maximum strength and hardness.
Applications
17-4PH stainless steel is ideal for use in high temperature and corrosive environments, such as medical and aerospace applications. It is highly resistant to chloride-induced stress corrosion cracking and is used in applications that are exposed to high levels of salt spray, such as sea water environments. It is also ideal for use in industrial applications that require high strength and corrosion resistance, such as petrochemical processing and pharmaceutical production.
Advantages
17-4PH stainless steel has many advantages over other alloys. It is very resistant to corrosion, has good mechanical properties, and can be readily machined. Its strength and hardness properties can be enhanced through the use of heat treatments. Additionally, it is a cost-effective alloy and can be readily obtained in many forms, such as bars, rods, sheets and plates.
Disadvantages
The main disadvantage of 17-4PH stainless steel is that it is not suitable for welding. It is not readily weldable and should not be used in applications where welding is required. Additionally, it is susceptible to heat-induced embrittlement when it is heat treated at temperatures greater than 1500°F (815°C).
Conclusion
17-4PH stainless steel is a highly corrosion resistant alloy that is capable of being heat-treated to extremely high levels of mechanical properties. It is a popular choice for use in highly corrosive environments and applications that require high strength and corrosion resistance. The main disadvantage of 17-4PH stainless steel is that it cannot be welded and is susceptible to heat-induced embrittlement if heat-treated at temperatures greater than 1500°F (815°C).
