We are always looking at ways to reduce our operating cost for materials.  Instead of using the traditional stamped 1018 mild steel parts, we are testing powdered metal mild steel parts for some flanges on our thin wall 409 tubular products.  409 powdered metal has been the norm for all of the parts that require stainless flanges, and stamped 1018 has been the norm for parts requiring mild steel flanges.  The sintering process for 409 is very well known in our industry, and produces parts that have good weldability.  The sintering process for mild steel is yet to be proven out.  I have many different material compositions that I have been testing, and see as the as the Carbon and Oxygen content goes up (.002%-1.9% and .02%-.07% respectively), the welding consistency goes down.  The welding process is automated GMAW with 409 metal core wire, pulse spray, 98-2.  The density is consistent for all alloy's tested.  Any insight as to why??  Anybody else use similar products??
Thanks,
Mark