Heat Treatment and Post Weld Heat Treatment of American Standard Pressure Cast
Steel
Introduction
In the industrial sector, American Standard Pressure Cast Steel (ASPCC) is one of the most widely used steels for structural applications. A major benefit of using ASPCC is that its properties are improved through heat treatment. Heat treatment is used to change the metallurgical structure of the steel, making it stronger and more reliable. Heat treatment can be used for hardening, stress relieving, tempering, and annealing. The most widely used heat treatment for ASPCC is hardening, followed by post weld heat treatment, which is necessary to ensure a stronger joint when welding.
Heat Treatment
Heat treatment is used to reduce stresses in steel and can be done either before or after welding. Heat treatments for ASPCC generally involve the application of heat, cooling, and tempering the steel. An example of heat treatment involves the following process:
Heating steel to a temperature between 813-987°C (1500-1800°F).
Allowing the steel to cool slowly by a natural process.
Tempering the steel in an oven at a temperature of 593-871°C (1100-1600°F).
The characteristics of ASPCC, such as its strength, toughness, and ductility, are all dependent on the heat treatment process used. Hardening is the most common heat treatment for ASPCC, providing a greater hardenability for the steel. Hardening is done by heating the steel to a higher than normal temperature quickly, followed by slow cooling and rapid cooling.
Post Weld Heat Treatment
After the steel has been heat treated, post weld heat treatment (PWHT) is a necessary step to ensure proper weld strength and performance. PWHT is done to relieve residual stresses in the steel and to prevent welding distortion. The process of PWHT involves slowly heating the steel to a specific temperature, followed by slow cooling.
For ASPCC, PWHT typically involves heating the welded area to between 593-871°C (1100-1600°F). The steel is left at the target temperature for a period of time and then allowed to cool slowly at a rate of approximately 25°C per hour.
Conclusion
Heat treatment is important for American Standard Pressure Cast Steel (ASPCC) to improve its properties and make it stronger and more reliable. The most common heat treatments involve heating, cooling, and tempering, and hardening is the most popular option for hardening of the steel. Post-weld heat treatment (PWHT) is also important for ASPCC, as it relieves residual stresses and prevents welding distortion. Heating the welded area to between 593-871°C (1100-1600°F) is typically the PWHT procedure used. By understanding the different heat treatment and PWHT processes, engineers can properly design and construct structures with ASPCC.
