Understand how heat input and shielding gas impact weld deposit properties When engineers design a structure — whether it is a bridge, building, or vehicle — they do so according to the strength of the base material. Every finished product must meet certain requirements, including how much weight it can withstand and the amount of force it can resist. During welding, it is usually important the filler metal match or slightly overmatch the base material’s mechanical properties to achieve those requirements and prevent weld failures that could be potentially catastrophic. To that end, filler metal manufacturers rigorously test products to guarantee they meet minimum specifications, based on American Welding Society (AWS) and other industry standards. Filler metals’ typical mechanical values are some degrees higher than the AWS minimums. There are welding variables, however, that can impact the finished weld properties, even when using the same filler metal. Mechanical properties such as tensile strength, ductility, and yield strength (see sidebar) can vary greatly from weld to weld as a result. Consider this example: An AWS E71T-1 gas-shielded carbon steel fluxcored wire typically provides 74,000- lb/in.2 tensile strength. Changing the shielding gas and welding parameters can make the weld possess over 90,000-lb/in.2 tensile strength — with that same filler metal. Understanding the ways in which variations in heat input and shielding gases, in particular, affect weld deposit properties is important. It helps ensure the weld stands up to the necessary strength and quality requirements. JULY 2016 / WELDING JOURNAL 43
Welding Journal | July 2016
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