June 26, 2014
Q: We performed an AWS D1.1 procedure qualification test using gas-shielded FCAW. We used a 0.052-in. E71T-9C electrode with 100 percent CO2 shielding at 200 amps and 26 V on 1-in. thick plate. We used a preheat and interpass temperature of 70 degrees F. Our pass layer sequence was three full layers, three split-pass layers, and one triple-pass layer. We passed a radiograph test but failed the Charpy V-notch impact test with a combined average of 18 ft.-lbs. Can you guys shed some light on why we failed with a FCAW electrode that meets the AWS A5.20 requirements for a T-9?
A: There are several potential reasons for the Charpy V-notch impact testing failure. Let’s take a look at the differences between the AWS A5.20 specification for carbon steel FCAW electrodes and the actual test you conducted.
The A5.20 specification requires that the filler metal be tested in the flat position with an interpass temperature of 275 to 325 degrees F. If the interpass temperature falls below 275 degrees, the plate has to be reheated to the 275-325 range before you can continue to weld.
You didn’t specify what type of material you were welding on. Material type can affect the mechanical properties of the weld based on the amount of dilution in the weld metal.
Additionally, the A5.20 specification states the total number of allowable weld layers for 0.052-in.-dia. electrodes is five to eight. This specification is for a test plate that is ¾ in. thick. Your procedure test plate was 1 in. thick and you had a total of seven layers. This indicates that your weld layer thicknesses may have been excessive.
Here are some suggestions based on the information that you provided:
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