Weld Testing Methods

Destructive testing proves weld quality by physically stressing the weld to failure or to a specified deformation. The guided bend test is the most common qualification test specified by AWS D1.1 and ASME Section IX. A coupon is cut from the test weld and bent around a die with a specific radius (typically 1.5× the material thickness for 3/4" and thinner steel). Face bend tests are bent with the weld face in tension; root bend tests are bent with the root in tension. The weld passes if, after bending to the specified angle (typically 180 degrees), no cracks or open defects larger than 1/8" appear in the weld or heat-affected zone. A root bend test is particularly revealing — if the root pass has any lack of fusion or porosity, it will open and appear as a crack during bending. The transverse tensile test pulls the specimen across the weld and measures ultimate tensile strength — for welder qualification, the tensile strength must equal or exceed the minimum tensile strength of the base metal. For longitudinal bends (cut parallel to the weld), the entire weld cross-section is in tension, revealing defects anywhere in the joint. Destructive tests are performed on qualification coupons and procedure qualification records (PQRs) to establish that a welding procedure produces acceptable mechanical properties.