With the primary and essential knowledge from the trials conducted based on trial and error method, further trials are conducted.However, subsequent trials are conducted according to a 2×5 design matrix. Two levels of current I2 and five levels of arc heating time T3 are considered for these trials. The other parameters are employed only for a short duration and hence are less significant and are maintained at levels specified by the manufacturer (similar to that of the trials 20 and 21). The design matrix with two levels of I2 current and five levels of T3 arc heating time are shown
in Table 4. The specimens welded as per the parameter settings provided in Table 4 for each trial are then tested for mechanical strength of the weld (discussed in following section). The surface