17-4ph-CopelandBallValves.doc

White Paper WP120501 17-4ph Background Copeland Industries uses the parcipitation hardened stainless 17-4 ph material for a variety of components including shafts, balls and seats and valve stems. The application temperature limitation we suggest for this material is normally 800 oF. Coal slurries, ore transport and low pressure valves (150# and 300# Class) valves with carbon steel bodies are common candidates for 17-4ph stems, normally utilized with 316ss balls and seats hardened with HVOF applied chrome carbide (CFS131). Precipitation hardening stainless steels are chromium and nickel containing steels that provide an optimum combination of the properties of martensitic and austenitic grades. Like martensitic grades, they are known for their ability to gain high strength through heat treatment and they also have the corrosion resistance of austenitic stainless steels. The high tensile strengths of precipitation hardening stainless steels come after a heat treatment process that leads to precipitation hardening of a martensitic or austenitic matrix. Hardening is achieved through the addition of one or more of the elements Copper, Aluminium, Titanium, Niobium, and Molybdenum. The most well known precipitation hardening steel is 17-4 PH. The name comes from the additions 17% Chromium and 4% Nickel. It also contains 4% Copper and 0.3% Niobium. 17-4 PH is also known as stainless steels grade 630. The advantage of precipitation hardening steels is that they can be supplied in a “solution treated” condition, which is readily machineable. After machining or another fabrication method, a single, low temperature heat treatment can be applied to increase the strength of the steel. This is known as ageing or age-hardening. As it is carried out at low temperature, the component undergoes no distortion. Characterisation of Stainless Steels Precipitation hardening stainless steels are characterised into one of three groups based on their final microstructures after heat treatm