Pre heat and weld took 2.7 hours total . These weighed around 700 Lbs each and were very hard to move about to get a good spot on the lower weld !
In the lathe being finished to fit the new gear cog.
The new cog in place (heated than press fit )
The upper weld ,
this piece is smoking hot as it was pre heated and a inter-pass temp of around 600 Degrees had to be maintained.
4140 is not a tool steel , technically it is a chrom-molly alloy. What happens if it is cooled to rapidly ? It enters the martensitic phase - refer to metallurgy .
What was not done properly during this weld adventure was no one in the shop knew the proper weld procedure for the parts . I pre-heated them to about 350 - 400 degrees F. using a gas torch than , welded the pieces in place using ER 70-2 filler metal while maintaining an inter-pass temp of around 600 degrees F. Than, when finished quickly covered the welded piece in a heat blanket to allow to cool as slowly as time would allow !
This helped to avoid cracking due to hydrogen embrittelment . Overall the welds turned out great !
These were all multi-pass welds , the upper (top) was 3 passes , the lower was 2 .
HAPPY WELDING !!!!
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