soft soldering question

Discussion in 'Metals' started by werowance, Feb 28, 2018.

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  1. Feb 28, 2018 #1

    werowance

    werowance

    werowance

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    can you soft solder (plumbers solder) steel? just regular CRS if its cleaned up?
    if so any particular color to heat it up to? like silver brazing I know the particular red I'm looking for before the silver will start to flow, but I tested a little plumbers solder on a scrap piece and never could get it to stick. [edit] I tried just cool enough to melt it on up to where the steel was starting to turn dark red. [end edit]

    would be nice to soft solder maybe say a sheet metal cover together or something. would be much cheaper than brass or copper sheet as long as it didn't need to hold preasure or anything. example maybe a sheet metal funnel for filling the little fuel tanks.
     
    Last edited: Feb 28, 2018
  2. Feb 28, 2018 #2

    goldstar31

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    Far too hot!

    With a copper soldering iron you should be able to place it just away from your cheek- without it burning you. I suppose that I was about 7 or 8 at the time- so I've been doing it for 80 years.

    With a fancier electric gadget, you should be able to see a bit of solder melt as it warms up.

    With a blow torch, you should SEE the solder melt and with care and a decent killed spirits of salts flux you should be able to 'tin' your steel sheet- BEFORE you join it to another one.
    You should be able to spread the molten tin/lead solder with a cloth which has been dipped in fat or resin flux or say cooking oil.

    I can or could do 'lead loading' car panels using an oxygen/acetylene torch- without the tissue or rag. That's a knack but even a ordinary electric soldering iron will give confirmation of the principles suggested.

    Get a bit of electrical wire, strip the covering and put the hot iron underneath it and go from the top with a fluxed bit of solder and watch it tin the copper wire. Then join wires the same way.
    Your iron or the job is FAR too hot.

    What you MUST ensure is that everything must be scrupulously clean to be joined. Yea, I can weld dirty rusty steel and blow molten steel along a track raising the dross as I go but it isn't the way for soft solder.


    Does this help?

    N
     
  3. Feb 28, 2018 #3

    dnalot

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    yes you can soft solder steel. Today's plumbers solder is aluminum based and is a little more difficult to use with steel so I use lead based solder for fabricating with steel. The part must be very clean and not shinny. Scuff it up with sandpaper or sand blast it. For steel I like to use a liquid flux. Depending on the melting temp of the solder the metal when heated will be slightly dark. Just bring up the heat until the solder melts when touched to the part. A little more heat and the solder will flow, use your torch to draw the solder along the joint.

    Mark T
     
  4. Feb 28, 2018 #4

    Blogwitch

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    Don't try to do it with your electronic iron, it just won't be hot enough.

    I use either a 200 watt iron or a plumbers soldering torch which I normally use for silver solder. The torch being preferred.

    Because things have changed a little over the last few years, you will be lucky to find leaded solder, so just buy the new stuff and the recommended flux to go with it.


    John
     
  5. Feb 28, 2018 #5

    fcheslop

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    Use a liquid flux when possible if it beads on the surface it need further cleaning until it completely wets the surface
    Tin each surface to be joined first then sweat them together with a bit more solder
    Im not sure about the new lead free stuff and prefer tinsmiths solder over electrical although Iv been known to use whats available
     
  6. Feb 28, 2018 #6

    bazmak

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    A small torch rather than a soldering iron.For steel you must coat it with solder first or TIN using hydrochloric acid to etch the steel Once the steel is tinned or galvanised then normal soldering can be done with iron or low heat
     
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  7. Feb 28, 2018 #7

    packrat

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    Try and find some 50/50 solder..{50 lead/50 tin} it might be hard to find now days.??
    If you are getting the steel red hot just use flux and silver solder rod. no flux needed on copper with
    silver solder rod, like copper pipe. {buy the silver solder rod at your HVAC/Refrigeration workers outlet..it is not cheep}..
     
  8. Feb 28, 2018 #8

    goldstar31

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    Of course, Hydrochloric/Muriatic acid ( HCl) reacts with galvanized (zinc coated) steel to form Zinc Chloride which is a recommended flux- for tinning and cleaning steel prior to the joining process. I was taught by Alan Robinson author of the Repair of Vehicle Bodies to use solder paste( with HCl, obviously) to tin prior to lead loading car body work.

    Well said, Barry!

    Cheers

    Norm

    NB

    Just a think about those elusive but knackered simmered( spell check-- should read Sintered) bronze bearings.
    You could tin them!!!!

    I recall when I was a manure student with a worn set of feed screw nuts, recycling lead/tin indium bearings for the 'solder', using candle soot as a release agent on the feed screws--- and I expect that you know the rest.
    Just the odd thought as it is still in the grips of Siberia here with more to come.:thumbup:

    Cheers

    N
     
  9. Feb 28, 2018 #9

    goldstar31

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  10. Mar 1, 2018 #10

    Naiveambition

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    First off I am NO expert on soldering by any means, with that said I have been able to use soft solder or 50/50 to get steel to stick, but on same note it was steel that was solder able. Like what you see in home improvement store which I'm sure is low grade. So if the same material is used I see no problem. Outside of that , listen to the previous posters for more knowledgeable people

    When doing my peices I will flux the entire joint, clamp together for holding then heat the joint till the temp will melt the solder by touch.. Much like doing plumbing pipes, just run a bead around or on the joint, Red hot for me was way to much heat
     
  11. Mar 1, 2018 #11

    bazmak

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    Some one mentioned red heat,thats a no no way too hot
    Just heat until the solder melts.The first coat is just a tinning
    to form galvanised finish.Aftre cleaning soldering can be done with iron
    sike etc depends on steel thickness
     
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  12. Mar 1, 2018 #12

    werowance

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    Thank you. I'm using a propane plumbers torch for soldering. but no flux.
    and was not tinning the parts before hand. and the parts when I said shiney clean, I meant scuffed with about 600 grit sand paper like I do for copper soldering. I just was saying that the rust and the grease etc was cleaned off cause I know copper doesn't like to solder unless its bright clean and free of oil.

    I'm doubting Ill find leaded solder anywhere in the USA unless its old stock somewhere. I cant even buy vented gas cans anymore because of the environmentalists. I guess they are smarter than I am though idk.

    now I have a tin of soldering paste that came with one of the rolls of plumbers solder for flux, will that work ok? its thick and dark like dirty Vaseline.

    then last question, high temp vs regular plumbers solder, any metalergical properties of the high temp that would make it stick any better? aside from it being able to withstand higher temperatures and is probably harder I understand. I'm just wondering about would it be easier to make it stick or would it be about the same as the regular soft solder?

    and thank you all for the replies
     
  13. Mar 1, 2018 #13

    BobsModels

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    Hi

    Not sure how much strength you need but if soft soldering not much. Here is a product I use for all my soft soldering.

    Its called Stay Brite. It melts at about 450. It is tough stuff. It has a real high surface tension. They have all kinds of sizes. It must be used with its flux called Stay Clean, use very little.

    Here is a link to the site so you can check out its technical data.

    http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Lead-Free-Solders/stay-brite.aspx

    Here are two links to buy some:

    A complete package:

    https://www.ebay.com/itm/Harris-Sta...438625&hash=item3d12d06ad8:g:FXEAAOSwPpFXML5a

    If you want real small stuff here is 1/32 diameter but you need to buy the flux - do not try it without their flux

    https://www.ebay.com/itm/STAY-BRITE...450186?hash=item5b341eaf8a:g:DuEAAOSw4A5YtOel

    I only use the 1/32 or 1/16 size for my model work. Much better stuff than plumbers solder.

    Good Luck

    Bob
     
  14. Mar 2, 2018 #14

    GLCarlson

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    Amazon. Lots of options, but the one you want is the 63/37 (or as close to that as you can get) eutectic tin/lead solder. Avoid rosin core, it's intended for electronic use (or use it, but with a good metal flux). Another good source is any stained glass supply house. That tends to be 50/50. I'm still working on a 25 lb roll from decades ago, but it's available. The nannies haven't won, they've just driven the useful stuff out of the big box hardware stores.

    (Ditto on vented gas cans- see youtube for many conversions, and e-bay or Amazon for the parts. Yeah, it's a pain, but only about 15 minutes work to convert a crappy gas can to one that works.)

    BTW: Bob (above) is right. The stuff he recommends works much better.
     
  15. Mar 3, 2018 #15

    dnalot

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    McMaster Carr has solder with lead in a number of grades from low temp melt to high temp melt. They also have solder for soldering aluminum.

    Mark T
     
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  16. Apr 19, 2018 #16

    Engineeringtech

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    Are you wedded to plumbers solder? The modern stuff (legal to use in water lines) has antimony and other elements in it, that in my opinion, makes it much more difficult to use than leaded solder. Of course these days, it is difficult to find leaded plumbers solder. You can still easily find electronic solders like 63/37 and 60/40 alloys, which melt at temperatures from 361-374 deg. F. I've been working in the electronic field for 35 years, and have in this time used at LEAST a hundred pounds of rosin core lead solder.. It WILL solder steel, as long as you clean the steel thoroughly and a paste flux (like NoKorode). Better yet, find a mildly acid tinners flux MADE for joining steel with solder. (I'd bet Eastwood Automotive has tinners solder, as people use solder for car body work. I believe leaded solder is also still used to join the barrels on double barrel shotguns.) Eastwood would probably have 60/40 and 63/37 solder bar. What is the difference between the two alloys? 60/40 transitions from liquid to solid over a range of temperature. If you accidently move the pieces during this transition, you'll get a "cold joint", which is not strong, or attractive. 63/37 is a Eutectic alloy which transitions from liquid to solid phase at one temperature. Much harder to get a cold joint with 63/37 alloy.

    Soft solder is not as strong as silver soldering, hard solder or brazing. BE VERY CAREFUL when working with leaded solder not to heat the steel much beyond the temperature needed to melt the solder, as that will cause lead fumes, which can hurt your health. Red hot steel is WAY too hot. Ever heat a piece of shiny steel to the point where it turns blue (500 - 600 degrees)? That's probably as hot as you want to go.
     
  17. Apr 19, 2018 #17

    werowance

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    I also use electronics solder a lot of times, and happen to have an ancient very soft very thin roll of it, its probably leaded. but its not as strong either. but it does seem to flow a lot better. (certainly i don't use it on food grade or water pipes for obvious reasons)

    I just had not had very much luck soft soldering steel or iron is all. the tinning method has helped and the stay brite flux has helped to, I'm thinking the stay brite is the key and not using that brown goo that comes with the plumbers solder. not to be confused with stay silv flux which i was already using for silver brazing. its still not like sweating copper pipe (that's easy) but I have managed to stick steel parts together now with it following all the help received.

    i really appreciate all the help with this to. something to point out, i noticed after posting this that my old farmall tractor radiator is copper with a cast iron neck on it soldered in place, which is starting to crack. i may give a go at repairing that now that i know i can stick to pieces of steel together. - just want to see if i can figure out a way to pickle that area without pulling the whole radiator since its on top. i was thinking a putty or playdough dam around the neck to hold the pickle solution on it?
     
  18. Jun 26, 2018 #18

    OrangeAlpine

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    While getting leaded solder has not been a problem, I have found some big name brands found at "big box store" solder to be fit only for making fishing weights. It will melt and bead up, regardless of the prep and flux used. Just will not flow or "suck" into a joint. Some nonleaded solder is very good, much better than some of the leaded junk. I like to use electrical solder. Very nice stuff to work with.

    BTW, steel is easy to solder. Soldered some this morning, using Kester solder. Just get it clean, use flux and good solder.
     

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