ArtMetal

To successfully solder to stainless steel you need theproper flux. I prefer Johnson's Stainless steel soldering flux that I get form the HVAC supply house. I use 60/40 lead/tin solder and have the solder pre-melted in an electric melting pot. I use a 350 or 500 watt Lenk soldering iron and keep the tip scrupously clean at all times.

The stainless should be sanded with 400 grit SiC paper immediately prior to soldering and wiped clean with acetone. The same for the copper wire. It also helps to have the end of the wire hammered flat to get increased contact patch.

The stainless takesmuch longer than the copper to heat, and is a poor conductor of heat, so I suggest you tin the contact spot before you introduce the copper wire. Once tinned, simply place the wire on the tinned spot, flux and re-heat the joint area and add a bit of additional solder.