Providing Welding Solutions
Over the last decade, Euroweld has learned that wire processing is critical to success and defect free welding, especially where orbital GTAW is used. Manual GTAW typically can tolerate more contaminants because the weld pool is somewhat more turbulent and assists the evolution of gases.
The composition of ER90S-B9 is lean on deoxidizing elements because of their detrimental effect on elevated temperature creep strength. Aluminum, silicon, titanium and manganese are traditionally used to deoxidize or “clean” the molten weld pool and assist the escape of gases, thus reducing or eliminating porosity. When lean on deoxidizing elements, any foreign material on or in the wire can jeopardize the cleanliness of the weld.
It has been demonstrated that “white glove clean” may not actually be clean. Using this approach, only the surface is examined. It is what is under the surface or trapped in the surface irregularities that need to be evaluated. Because of it’s strength and resistance to heating, ER90S-B9 goes through more draw-anneal-draw cycles between the hot rolled rod stage and the finished product diameter than most other alloys. Traditional pickling operations do not offer satisfactory cleaning. In many cases, actual material must be removed during the manufacturing process to ensure that contaminants have been reduced to the lowest possible levels. These extra measures plus the resulting loss of material attribute to additional costs. But, the 20 to 30 percent additional weld metal costs are significantly less than weld repairs.
The following figures illustrate the types of indications that result from using “standard” ER90S-B9 in orbital GTAW welds. Many appear small while some can get quite large. It is very common to experience rejectable porosity, both visually and by radiography. This is especially true when ultrasonic testing is used. The dots seem to be connected and show up as a rejectable linear indication. This is even more apparent where phased-array methods are employed.
Orbital GTAW Indications When Standard ER90S-B9 Wire is Used
(Etched and Magnified 8,50,100X)