For practice, I am trying to forge weld 2 pieces of 1/8" x 1 1/2" mild steel. I am using detergent type borax bought at the store. The color of the steel before hammering is an orange/light orange. It will not weld. What am I doing wrong?

with those thin sections, it's likely that your loosing too much heat before you make it to the anvil. Give me a call, and we'll set up some time for you to come over and I'll help you with it.