Q. Selection of Electrodes and Filler Metals?
Only low hydrogen electrodes shall be used for SMAW of all carbon and low alloy steels, except for root pass welding of single welded joints.
Electrodes and/or filler metals shall be selected such that:
a. The strength of deposited weld shall be at least equal to the specified minimum tensile strengths of the material being welded.
b. When joining similar materials, the chemical composition of the deposited weld metal shall match that of the base material as closely as possible. However, this shall not preclude the use of welding materials containing alloying elements of different types or in different amounts than those in the base materials, provided there is evidence that such elements are not harmful or are beneficial from the standpoint of achieving desirable weld metal properties, such as adequate tensile strength after post-weld heat treatment or adequate impact strength at low temperatures.
c. When joining two dissimilar materials of two different minimum UTS values, chemical composition and UTS value in the deposited weld from electrodes, shall be equal to the higher UTS value material, e.g. welding of SA 106 Grade B pipes shall not be welded to SA 516 Grade 70 plates by using E 6010 rods, instead E 7018 rods shall be used. The use of carbon and half-molybdenum rods to weld carbon steel are not permitted.
d. Filler metals falling in the F1 and F2 groups shall not be used. F4 electrodes shall not be used for the root pass of groove welds that will not be back-gouged.