Welding Test Coupon Procedures
Follow a clear example of test coupon welding procedures for a 3G welding certification.
In this 3G welding procedure, the notes were taken from the same section of the AWS code that is used for the 3/8 inch limited thickness test procedure.
The test coupons shall be pre-cut and ready to prepare.
The welder shall grind the face of the test plates a minimum of one inch back from the bevel and a minimum of a quarter of an inch.
Next, the backing bar to bare metal shall be cleaned with a grinder, and the oxidation off of the bevel, to bare metal. After the Welding Inspector will check the bevel angles with a protractor.
1. The Root Pass:
The welder shall set to root opening with two 1/8 inch welding electrodes and then the test plate shall be inspected for fit-up.
The test coupon shall be put in a vertical position and marked with a white marker to make sure not to move the plate anytime during Welding or cleaning. This is done because the AWS Procedure notes state:
“Now the test will be placed in the fixed position. The test piece will be marked in position with a marker and the NDT Inspector may see the test anytime during the testing. During the test, the pieces shall not be moved in any direction and or removed from the testing place without the Inspector's approval”.
After the root, the welding procedure states:
“The root of the weld shall be inspected, and there shall be no evidence of cracks, incomplete fusion, or inadequate joint penetration.
A concave root surface is permitted within the limits shown below, providing the total weld thickness is equal to or greater than that of the base metal.
The maximum root surface concavity shall be 1/16 in. (1.6 mm) and a maximum melt-through shall be 1/8 in. (3 mm)”
2. The Hot Pass:
The hot pass shall be done using the same technique as the root pass. A single pass shall be filled with no restarts. The slag shall be cleaned.
3. The Cap Weld:
The plate shall be left to cool down till the welder can almost touch it.
The cap of the weld shall be done using the weave technique while washing the weld about 1/16 of an inch past the edge of the bevel.
The sides must be held for about a second before moving back to the other side.
The cap shall be also done in a single pass just like the root and hot pass. The welder must give good weld penetration, preventing face bend failure and undercut.
The acceptance criteria for the face of the weld are as follows, according to AWS:
“The face of the weld shall be flush with the surface of the base metal, and the weld shall merge smoothly with the base metal. Undercut shall not exceed 1/32 in. (1 mm). Weld reinforcement shall not exceed 1/8 in. (3 mm)”
The first picture below is the weld still covered in slag. The second picture is the slag lifting itself off of the cap. The last picture is the cap cleaned with a wire brush.
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References
1. AQC Inspection
