Soldering a washer to a piece of steel

Hello, I am a soldering newbie. I've soldered on and off for years but am far from a pro. I am currently looking to attach a washer to a steel turn base that I have for a music box I am making. What are your thoughts on soldering steel? I bought a 2% nickel metal but can't get it to melt. My iron only goes to 999°. I'm looking for some advice on how to attach these two metals. What products and methods are reccomended? I did get them to stick but was hoping for a stronger bond.

Thanks! Kevin