A weld sample is produced prior to commencing the final welding of the product. All welding variables are controlled and recorded when welding the weld sample or coupon. These welded coupons are then tested to ensure that the weld joint will be of acceptable quality.
The types of tests involved in weld testing are visual inspection, non-destructive testing such as Radiographic examination (RT), Ultrasonic testing ( UT or UFD), Magnetic Particle test (FMPI or MPI or MT) and Liquid Dye Penetrant Test ( DPI or PT) followed by appropriate mechanical test such as Weld tensile test, transverse test, longitudinal bend test, transverse bend test, impact test, macro examination or macro test, hardness survey or hardness test, weld fracture test, nick break test, fillet break test, corrosion resistance test, metallographic test, microstructure test, ferrite count test, ferrite number test, post weld heat treatment or stress relieving and chemical analysis.
The welded sample or coupon is often tested at various stages of fabrication such as for Welding Procedure Qualification Record (WPQR), to qualify Welding Procedure Specification (WPS), to qualify welder as Welder Qualification Record ( WQ or WQR) and to accept the final product in the form of Production Weld test.