Welding quality inspection

(1) Visual Inspection of Weld Seam Appearance During the production process, quality control involves operators visually inspecting the weld quality inside and outside the tank. Visual inspection can only identify very obvious defects, such as weak welds, cold soldering, burned-through welds, overheated welds, uneven welds, missed welds, spatter marks, insufficient or excessive lap joint overlap at the tank's start or end, etc.

(2) Weld seam strength inspection (ball tester) method: Place the sample tank on the ball tester, align the ball with the weld seam in a straight line, move the ball along the tank body weld seam to expand and protrude the weld by 1~2mm (adjustable). Remove the tank body from the ball tester and inspect for any cracks or fractures in the weld seam.

(3) The tear test method is as follows: Take two sample cans, cut a 5mm notch at one end of the can body with scissors or pliers, and bend the cut surface upward. Then, fit the can body onto the test mandrel, clamp the cut surface with pliers, and continuously and evenly tear the weld seam upward (at a 45° angle to the body seam—avoid pulling forcefully). Repeat the process with the second can, but tear from the opposite end. Visually inspect the torn weld seam: If the entire weld seam tears cleanly and feels smooth when shaken between the index and middle fingers, the weld quality is good; if the weld seam breaks at a certain point during tearing, it indicates weak welding current; if the edges of the torn weld seam are uneven and rough to the touch, it suggests spatter or overheating at the weld point, as well as excessive welding current. Bend the torn weld seam strip—it should not be brittle or break. Twist and knot the weld seam—it should not break but remain flexible. If it is brittle or breaks, it indicates excessive welding current. This method is highly effective for testing cold or hot welds.

(4) The primary purpose of the conical test is to evaluate the extensibility of the front and rear weld points. The testing method is as follows: Place the test can body on the conical testing instrument, insert a proportionally sized cone at a constant speed into the welded can body and expand it into a conical shape. Remove the can body and observe the expansion: If the expansion exceeds 20%, the flanging performance is satisfactory; an expansion between 10% and 20% is acceptable; if the expansion is ≤10%, the result considered unqualified.

(5) The purpose of the weld seam flip and curl test is primarily to inspect the extensibility of the front and rear weld points. The testing method is as follows: Remove one can body from the welding machine, fix the corresponding mold on the base plate of the flip and curl testing device, and place the can body on the mold on the flip testing base plate. Operate the piston valve to push the pressure plate against the can body for edge curling. After curling approximately 10mm, remove the can body and inspect the curled portion for cracks. If cracks are present, the can body is deemed unqualified.

(6) Before welding, the overlap, width, and thickness of the weld are typically measured using a magnifying glass with a scale or a projector to determine the pre-weld overlap width and post-weld seam width. The weld thickness is measured using a conical micrometer.

(7) Inspection of the inner diameter: Use an internal diameter caliper, with a front-to-back diameter difference of less than 0.10mm.