Moran Iron Works, a US-based “dynamic and flexible fabrication facility,” created a video some months back on how the SMAW 4G Overhead Welding Certification process works. Full transcript is below the video.
The following test is used by Moran Iron works to certify our welders in the shielded metal arc welding 4G overhead process.
1. The first step in the certification process is to make the test pieces, called coupons. The coupons consist of two pieces of plate, which will be welded together. The weld is tested by bending it to reveal any flaws or cracks. Each piece of plate will be beveled at a 22 1/2 degree angle. Two beveled plates side by side make up one 45 degree angle. This is the weld joint.
2. The welder cleans up his own test pieces with a grinder. All mill scale and other debris should be removed from the coupon, as such items may cause the weld to fail. The backing bar should be cleaned with a grinder as well.
3. The 3/8 inch thick test plate are welded to the backing bar. It's very important to note that there is no gap between the test plates and the backing bar, or the welder will not achieve a full penetration weld.
4. To keep the root opening between test plates one-quarter inch wide, a piece of plate with that thickness is used as a gage.
5. Once the test plate is tack-welded into place, the welder adjusts the test plate to a comfortable position. Then the welder fine tunes the welding machine within certain parameters to make sure the settings and temperatures are correct.
6. Once the test piece is in place, it cannot be removed until the test is finished.
7. After each pass, the weld piece is cleaned up by either grinding or using the wire wheel.
8. After multiple passes the test piece is finished and removed from its jig.
9. The test piece is marked where it will be cut and the ends are scraped. One piece will get a face bend; the other will receive a root bend. A center section is kept for both visual reference and backup, in case one coupon is damaged or destroyed.
10. After the coupons are cut, a torch is used to cut of the backing bar. The coupon is then ground smooth to prepare for testing.
11. The coupons are bent in half by a hydraulic press. One coupon gets bent to a radius of 1 1/2 inches on the root pass, and the other gets bent to the same radius on the face pass to expose any flaws or cracks in the weld.
Specific criteria are set forth by the American Welding Society to determine whether the welder passes or fails the certification.
