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James Arlen Gillaspie

Best solder to color-match carbon steel?

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Hello, Gentlemen, I am not sure this is the right forum for this question, but I am wondering if anyone knows a good low temperature solder to join plain no alloy (except carbon, of course) steel to steel with minimum color difference.  I am attempting to fill in a crack in an antique piece, for cosmetic reasons only, no strength in the joint required. 

Edited by James Arlen Gillaspie
Needed to be more specific.

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For low temp solder to steel, I found that the paste solder works best, but is still a pain to flow properly.  I've had limited success with it.  Your steel must be decreased and perfectly clean.  Also take into consideration if there is a general 'patina' on what your working on, the solder will not look the same.  it will never match the natural patina - it may always look like solder.  You will be able to tell the difference in the two different metals over time - unless your project is polished. 

Others have good experience with soldering steel with low temp solders, but I've found that high temp solders work much more like you expect them too with steel. 

 

Also, for the low temp solder paste - my best results for bonding only happen when the solder was hot enough to stay molten and I placed another piece of material in that molten solder. 

Edited by Daniel W

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Tix brand solder is best for antiques, but no solder will match carbon steel.  Luckily, every brand of cold blue compound will produce a different shade of dark on solder.  And Birchwood-Casey Brass Black is even better.

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Thanks for the replies.  The weird thing about this particular piece is that someone already did extensive soft solder work on it, and the solder matches so well that I thought it was modern welding.  There really is no difference in the color.  I was surprised when I had to normalize a crushed section (a rusted out and restored 600 year old helmet that got dropped) to even begin to bump it back out, and some bits fell out.  I have already had some success for some restorations with tin-antimony solder, as it will take gun bluing, but it has a very slight greenish tint that is not quite right.  Perhaps it was someone's custom alloy. Oh, and in this case the finish is bright, but even so, as you know, solder usually looks a bit off, rather like TIG rod tends to produce a noticeably different tint from polished mild steel. 

Edited by James Arlen Gillaspie
Needed more detail.

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Aha!  Didn't know you were trying to match a 600-year old helmet finished bright, that makes a bit of a difference!  I'd suggest making your own lead/tin blends running anywhere from 90/10 to 50/50 and gently aging the different proportions with a quick dip in ferric chloride.  Somewhere in there you'll hit one that looks like the first stuff.  I suggested the Tix brand because it has a much lower melting point than any lead/tin mix and has a very thin line if used properly.  It's what they use on double shotguns to hold the barrels and ribs together.  

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2 hours ago, Alan Longmire said:

I suggested the Tix brand because it has a much lower melting point than any lead/tin mix and has a very thin line if used properly. 

Alan, what flux do you like to use with Tix?

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Thier proprietary flux, Tix flux.  They are unique for a reason.  It flows at something like 230 degrees F.  Which is also why you can't hot-blue a double...

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