A NEW METHOD FOR REDUCING DIFFUSIBLE HYDROGEN IN WELD METAL

The effect of hydrogen on weld metal and weld heat-affected zones (HAZ) has been well established over many years. The potential for hydrogen-assisted cracking increases as the strength of the steel increases. High fuel costs have driven the need for lower weights in the transportation and shipbuilding industries, and increased regulations have driven the need for higher safety factors in the pipeline industry. As a result, many industries are requiring higher and higher base metal strengths. The push for higher strength steels has resulted in an increased demand for ultra-low hydrogen welding consumables and processes. Manufacturers of flux-cored arc welding (FCAW) electrodes have generally attacked the problem of weld metal hydrogen through the use of raw materials that react with hydrogen to take it out of solution, by baking the wires in-process, and by using special drawing techniques and lubricants to minimize hydrogen pick-up. Unfortunately, many of the potential solutions result in electrodes that have poor operability, wire feeding problems, and/or increased welding fume. Hobart Brothers has recently developed a method of producing very low-hydrogen weld deposits, which utilizes fluorine-containing gas compounds in the weld shielding gas. The modified shielding gas has no effect on the weld metal properties or the operation of the welding electrodes. This paper provides details of the method, along with test results that have been achieved using a number of flux- and metal-cored electrodes representing a variety of American Welding Society (AWS) classifications.