that is, soldering iron welding, you need to use a special flux to weld stainless steel.
(Flux to Taobao search --- stainless steel flux, counting the postage more than 10 dollars to get. (Beijing Zhongfa also sells)
Note: Copper pieces of larger words can be heated first, otherwise the temperature is not enough to weld.
(2) emergency quick treatment (the simplest):
Take some fine copper wire (no insulating paint, must be very fine) wrapped around the capillary.
This way, ordinary solder can be directly soldered on the stainless steel capillary tube.
(This program I personally practice, the effect can be oh)
Note: This method requires welding a longer capillary tube, taking up more space
(C) professional welding - resistance welding (than brazing resistance to high temperatures)
What are you going to do?