FIELD WELDABILITY TEST FOR PIPELINE STEELS

An investigation requested and supported by the American Petroleum Institute to develop a simple weldability test for pipeline steels that could be conducted in the field as a measure of their susceptibility to hydrogen-induced cracking is reported. The goal was a quantitative and reproducible test that could be prepared and evaluated with a hammer, vise and power saws. A 150 x 200 mm specimen cut from formed pipe with a central sawed slot in the girth direction and welded with a cellulosic electrode at welding conditions matching those used in the field was found to develop hydrogen-induced cracks. Easy measurement of the extent of cracking was accomplished by tempering and heat tinting any cracks formed and then cutting slits into the weld from one side of the specimen and hammering off one side of the plate to expose any part of the fracture previously heat tinted. The test was examined for sensitivity and reproducibility by testing a wide range of pipe steel compositions and thicknesses and was found to respond, as expected, to carbon, alloy content and gage. The test was used to study the extent of cracking as a function of time lapse up to 20 min after welding.more » Not only was there a strong effect of time lapse, but some of the more sensitive steels developed cracks in less than 5 min. The effect of preheat on cracking was also clearly shown by the test. Thus the test appeared potentially useful for determining the time limit between the root pass and hot pass and the necessary preheat. It should have applicability to testing structural steels, generally, as well.« less