Hi left seat, I thought a picture of what I use to solder piano wire gear or mounts made from it would help.

Bernzomatic torch comes with a solder tip also, I use and enjoy mine a lot. Stay-Bright soldering kit will solder a lot of stuff and make a solid solder joint on brass & steel metals. I use Bernsomatic water soluble flux for it's easy water clean up after the solder joints are cooled, the liquid flux really works well and all flux is a corrosive so needs to be cleaned off as best as possible, steel will rust as well. Hot soapy water and a small wire brush will clean most of it off.

Some practice using this will go a long way, don't apply the solder until the metal is hot enough to melt it then remove the heat, allow to cool before handling your work.

Hope this helps