Checking what I am watching-Forge Welding

[WL smith]

I once drove 200 miles one way to ask a question of Francis whittiker (sp). His answer was blacksmiths used files to solve that problem. I had my answer but it was a long drive home. whatever it is worth to you. Hammer on

[natenaaron]

What do you mean not hardly.  It is 126 miles to the next "town" and a hundred more miles to where a black smith is.  Unless there is a secret list of blacksmith locations somewhere.

[gote]

Well Frosty are you not a little bit categorical here. If the flux is ONLY used to keep oxygen out, why use Borax? Besides technically a flux is something that makes tings fluid, hence the word. Borax (and some other boron containing compounds) have the property of combining with metal oxides to compounds with lower melting point that can be squeezed out from the joint.

Some smiths use sand, some use glass, some use a mixture that in reality is a recipy for glass. Japanese swordsmiths use rice straw ash that contains a lot of silica and will kind of fuse to a glass. All these do what you say: keep the oxygen out but do not fluidise oxides. However fluxes containing borax will dissolve the oxides. Alaska flux will in addition take care of oxygen - maybe also oxygen in the iron oxide. Technicus Joe keeps the temperature at a level where the oxide is fluid even without flux.

 Unless it is kept in reducing atmosphere there aint no such animal as an oxide free iron/steel surface. It happens immediately even at room temperature but a very thin layer will perhaps not interfere when welding. If you are using borax the way you describe you are squeezing fluidised oxides out together with the borax just as I do - even if it is very little from a newly filed surface.

    

[Frosty]

On 8/23/2016 at 8:03 AM, natenaaron said:

What do you mean not hardly.  It is 126 miles to the next "town" and a hundred more miles to where a black smith is.  Unless there is a secret list of blacksmith locations somewhere.

Well, lots of guys weld with the joint surfaces cruddy enough they need the molten flux to carry the crud out of the joint. I don't know about borax lowering the melting temperature of iron oxide but Ill put the factoid in my maybe files. Charcoal or any carbon in the joint say rice paper will deoxidize the scale provided it isn't too cruddy. Stuff like sand, ground glass, etc. form a layer that keeps air off the steel AND carries crud out when struck.

When possible I shine my joint surfaces up with a file give it a light sprinkle of flux then close the joint long before bring it near red heat. I've watched guys weld at pretty low temps with a couple drops of 3 in 1 oil for the flux.

I had to look up "flux" to see how it "makes things fluid". In all the definitions I read it referred to flux as a description and quantification of flow. I didn't find a definition where flux even implied making things fluid.

Perhaps "flux" applies to casting, soldering, forge welding, etc. by describing how a material carries crud out of a joint or molten material. I don't know about others but I've never fluxed a melt before it was melted.

Frosty The Lucky.

[gote]

Flux  late Middle English: from Latin fluxus, from fluere ‘to flow’. In my corner of the world it is "flussmedel" and it definitely means a substance that lowers the melting point/makes things flow (It may also prevent oxygen ingress but if that is the sole reason, other words are used.).

Borax has been used to identify metal oxides for some two hundred years. The process is simple: First the borax is heated until anhydrous then the oxide is dissolved in the borax and the resulting colour is an aid to identification. This works because the metal oxide is dissolved - a process that obvioulsy has been known to chemists for a very long time. Boron compund have been used for lowering the melting point in the glass/ceramic industry for a long time.  

As I understand it, the process goes via diborontrioxide that combines with the metal oxide. The trioxide is formed at lower temperature if the source of the boron is boric acid (575°C) rather than borax. (765°C). A flux containing boric acid should thus be useful for welding at lower temperatures (provided that the dissolving of the metal oxide can take place at the lower temperature).

The metal oxides are the problem in all welding/brazing/soldering. If there were no oxides we would be able to weld at room temperature. Paper, oil etc. may combine with the oxygen in the oxide layer to form carbon oxides and dihydrogenoxide which of course will disappear. Surplus carbon will dissolve in the iron if in small amounts. One could say that this is a smelting process on the microscopical scale.  

[JHCC]

10 minutes ago, gote said:

As I understand it, the process goes via diborontrioxide that combines with the metal oxide. The trioxide is formed at lower temperature if the source of the boron is boric acid (575°C) rather than borax. (765°C). A flux containing boric acid should thus be useful for welding at lower temperatures (provided that the dissolving of the metal oxide can take place at the lower temperature).

In other words, it's not that the flux lowers the melting point of the oxide, but that it dissolves the oxide while itself remaining liquid. (Like nitric acid dissolving a penny: the acid doesn't lower the melting point of the copper.) 

[Frosty]

I guess we're just reading different definitions. We certainly seem to have different styles of forge welding, there aren't any significant oxides in my joints so a flux or whatever doesn't need to carry out or dissolve scale, dirt or such.

I've said it before and this is the last time. Boric acid has a lower melting temp so it can form an air barrier at a lower temperature so less oxide can form.

I'm done.