Don Bruder wrote:

.. you don't solder steel .. Period.

I have also had terrible luck getting anything to wet steel. However, I
found that a lot of my problem was that I was sanding the steel shiny,
and something about the abrasives was leaving an invisible layer covering
the steel and preventing the flux from working. I had success when I first
scrubbed with steel wool and then washed with acetone, also I had to get
"black flux" which operated at a higher temp. Then I could get it to wet
but it still wasn't easy. Sure wish someone would come teach me.

Grant Erwin
Kirkland, Washington