welding 4140,parts breaking

[glenncad]

I recieved some 4140 pins that needed tabs welded on the ends,tabs are 572 material. I pre-heated the pins to 450 degrees and air cooled in room temp. The tabs are breaking off in the field. Should the tabs be welded on and then harden the pins to prevent this,,, or what?????Thank you.

 

[unclesyd]

Where is the break?
What was the welding process and electrode material?

 

[stanweld]

In addition to unclesyd's questions, what is the thickness of each material?