Puck welding problems

Having a Puck Welder is wonderful.

Unfortunately these things attract friends with more challenges.

Can anyone direct me on finding ways to join two steel wires about
1.5 mm diameter or build up one of the wires to 2.5 mm.

Puck has stainless steel wire and I have fine binding wire. The
sample is probably a low carbon steel. What is happening is that the
tip is blowing holes in the metal or covering up an area leaving a
cavity within the weld.

Best wishes to all.
John Stapleton