A Study on Cladding Characteristics Using the Laser-Arc Hybrid Welding Process

For safety, transport pipes such as process steel pipes related to oil and gas mining/refining have recently been required to be corrosion resistant, to protect against acidity in the moving fluid, such as high concentrations of hydrogen sulfide (H2S). Accordingly, there has been a rapidly increase in demand for clad steel pipes, made of ordinary steel with a welded overlay on the inner wall. However, clad welding the entire pipe inner wall reduces productivity and increases unit price. One solution to the problem is the double pipe manufacturing method, where an inner pipe of a corrosion-resistant material and an outer general steel pipe are separately formed. To fabricate a clad steel pipe using the dual pipe manufacturing method requires cladding welding of the remaining section after the inner pipe end of the inserted pipe is joined. However, when cladding welding is performed using a conventional welding process, problems such as high heat input, difficulty in technique, low productivity and control of dilution ratio occur. To overcome this problem, we conducted research on the use of laser arc hybrid welding to perform cladding welding. Key words: Laser-Arc hybrid welding, Cladding, Overlay welding, Inconel 625, Dilution ratio