Quote:
Originally Posted by glatt
Impressive! So what's that glowing liquid dripping out when it was first being heated up with flux?
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That's slag. It's a combination of flux and oxides/scale.
Flux just lowers the melting point of the oxides and allows them to run off the metal. If you don't use flux and have any oxides or anything in the weld you will create cold shuts (or inclusions) which pretty much ruin your weld. Cold shuts can cause the weld to break, which in laminated steel can be pretty spectacular/dangerous.
I hear British blacksmiths must make a clean weld without flux for their master test.