High alloy steel components are preheated before welding for reducing

In spot welding of aluminium sheets, the welding current should be .........A........ and weld time should be kept ............B......... than for $$MS$$ sheet of same thickness.

(A). higher / lower, (B). higher / lower

....................... is the non-fusion method of joining dissimilar metals with metals whose melting temp is greater than $${400^ \circ }C$$.

Continuous rails for Indian railways are welded by ........ Welding process.