This weekend, a friend and I attempted to produce crucible steel for the first time. It's something we've both been keen to try for a while so a couple weeks back we decided we'd put a plan together.
We were confident we could build the foundry but I wasn't sure my forge burner would be able to produce the heat required. We both have the same burner and they're sort of modular and could be easily transferred from a forge to a foundry so we figured why not use two burners and see how that goes.
We set out expectations at a realistic level and decided that this attempt would be to see if we could even melt steel.
We filled our crucible with cast iron (donated from resurfaced brake rotors) and small pieces of mild steel to bring the iron ratio up. The cast iron content was an unknown but we worked on the assumption of 2% carbon, aiming for a final level of 1.3%, though it could end up higher. Total mass was 600g.
Green glass was put on top.
Once it went in we were both surprised how quickly the glass melted. The crucible stayed in the foundry for a little over an hour before we killed the fuel supply and dropped in a little Aluminium. We left it sitting in the foundry for a few more minutes the took it out to cool.
An hour later the glass was cracked open and little puck fell out. It looked a little porous too it untrained eyes but we were still really happy we had seemingly pulled it off. High-fives were had.
I cut it in half to reveal what looked like a mostly solid puck but a quick polish and etch revealed that there were a couple pieces of unmelted mild steel in the bottom.
Despite that we were pretty pleased with ourselves. So we attempted melt number two. This didn't go nearly as well.
Melt #2 was 900g of small bits from oroshigane smelts. After 80-minutes only the glass had melted.
Here's what I think happened:
The first run had depleted our gas bottles somewhat so at the second run our 9kg gas bottles were low and quickly freezing, dropping gas pressure and heat. Essentially we just weren't as hot the second time around. That, and powdered cast iron probably melts a lot easier than chunks of carbon steel.
So in the end we determined we need a hotter fire source. LPG is expensive and will always have the freezing issue so well be exploring a waste oil burner for future attempts. When we've established a system that will reliably melt steel we'll begin looking closer at our recipes.
All in all, we're pretty happy with the mornings work.
All feedback welcome
*Edit* Photo seem to have published in the wrong order