Active-Controlled Passive Distribution of Power Offers Efficient Heat Treating Solution for Quality Arc Welding Joints of Steel Pipes

Abstract

Using high energy density welding arc, the joining process makes pipe joints involving melting of base metal. The thermal cycle could cause distortion and have residual stress around joints and there could be a prospect of hydrogen cracking. By employing proper heat treatment procedures, the physical, metallurgical, and mechanical properties of steel structures are regained for their long endurance under extreme operating conditions of pressure and temperature, particularly, in power industries. The joints need to undergo pre- and post-weld heat treatment. Induction heating is increasingly being used for heat treatment of pipes, tubes, pressure vessels, etc., made up of a special type of steel such as P91 Grade. As the popularity of the heat treatment process is on the rise, it is important to look into the energy efficiency and power delivery aspects of the system. This paper proposes an innovative method to configure the induction heating controller and the tank circuit so that the energy delivery to the pipe and its usage are inherently improved. The proposed ideas have been practically demonstrated using a 40–45 kW induction heater.