[TheForge] Re: New Discoveries: Ersatz EZ Weld

[Mike Spencer]

A mixture of two substances fused together typically has a lower
melting point than either of the components.

> The data I have says iron oxide as Fe2O3 has a melt point of 1566 C
> and iron (pure) at 1538 C.  Alloy steels should be lower including
> carbon steel.

My understanding of how forge-weld flux works is this: the oxides that
form at high temp have a *higher* melting point than the iron/steel.  So
when you get the surface of the workpieces just barely at the melting
point, any oxides present or that form on the trip from fire to anvil
are solid.  The solid oxides remain in the joint and weaken it or
cause total weld failure.

If you apply flux -- pretty much anything that will fuse with the
oxides and won't decompose or react furiously with iron or air -- the
flux fuses with the oxides (scale).  The fused mixture of scale and
flux has a lower melting point than the iron and becomes liquid when
the iron is at welding heat.  When the weld is hammered home, the
flux/scale squirts out of the joint and permits a good weld.

But that doesn't answer the question:

> ...why putting Fe2O3 in a flux makes a better flux -- but it seems
> to.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^