Hello Folks

I'm playing with some scope mount bases that I think are sintered "steel" metal.

I need to solder them to a mild steel adaptor that I've made up.

Does sintered metal play any special tricks when one solders (or TIGs) on it ??

Cheers - Foster

If they are fully dense MIM parts, soldering and TIG welding is the same as for a conventional steel of the same alloying composition.

If they are pressed and sintered, they are porous and require some special considerations for soldering and welding. In soldering, the main problem is the solder wicking into the porosity instead of staying in the joint area. Special soldering (or more commonly brazing) alloys for sintered steels are available, which have a tendency to seal the porosity in the vicinity of the joint, instead of wicking into the whole sintered part.

For TIG welding, it would be useful to know the exact material used. Many sintered steels have high carbon contents like 0.6% or 0.8% and are not suitable for welding. Structural parts like scope bases would most likely fall into that category.

Low carbon sintered steels (below app. 0.25%) can be welded without difficulty if they are absolutely clean and dry. Even smallest traces of oil or humidity in the part tend to cause blowholes and cracks. For that reason, we like to anneal all parts intended for welding before shipping them sealed in plastic bags.

Powder metal parts can vary considerably in density.Remington specialized in very high density PM.They can be alloys ,they can be carburized .
If they are expendable you can try to braze them [hard solder].Even high density PM [98-99 %] can hold significant oil as JV says. You might heat the parts at ~ 800F to remove oil and moisture before brazing.

I welded on a lower tang for a Win 94. The tang is a MIM part and welded just fine. It did shrink more than I expected.