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Post by runner42 on Oct 18, 2014 4:49:58 GMT
When is Silver Solder Silver Solder? Sung to the tune of When is a Sausage a Sausage by Billy Cotton and his Band.
Hi all,
how much silver content is required for a Silver Solder to be classified as Silver Solder? I have a 15% content Silver Solder that behaves strangely that I suspect that it has no place in Model Engineering particularly in Boiler making. This Silver Solder produces a dull grey sand like appearance and doesn't form fillets hardly at all. However, when filed it produces a hard steely appearance unlike the softer whitish appearance of higher silver content solders. Can a 45% or more silver solder be used to rework the joints established with a 15%?
TIA
Brian
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steam4ian
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Post by steam4ian on Oct 18, 2014 11:29:30 GMT
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Post by ejparrott on Oct 18, 2014 17:55:27 GMT
Keith is the best man I know to ask, he of CUP Alloys
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Post by runner42 on Oct 18, 2014 21:20:42 GMT
Hi Ian,
thanks for the cautionary advice, but no I haven't used it for any boiler-making tasks. Allan has already told me to use BOC ProSilver 45T which I shall use exclusively on the boiler. The reason I asked the question is that the AMBSC Code Part 1 allows 15% silver solder to be used, however I wasn't aware that it contains phosphorous which is not allowed by the code. In addition Martin Evans in his Model Locomotive Boilers book talks about using lower Silver content (but doesn't delineate their silver content) solders such as Argo-flo, Argo-swift or Argo-bond in affixing throatplates to barrels, backheads to wrappers, foundation rings, etc. But also cautions about minimising liquation when using these solders, another reason to avoid their use.
I agree Ed, that Keith from CupAlloys is the best person to provide a response from a purely scientific veiwpoint but he may not be aware of what silver solders are produced in Australia.
I would like an answer to the question of the possibility of reworking joints made with 15% silver solder with a 45% silver solder.
Brian.
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Post by Jim on Oct 18, 2014 22:31:28 GMT
I was advised by my boiler inspector to use 15% silver solder as specified in the code as a gap filler then to run the standard 45% silver solder over the joint and the two would blend which they did.
15% silver solder I used came from BOC and had a brazing temperature of 800c, there was mention or hint of it containing phosphorous.
Jim
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jma1009
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Post by jma1009 on Oct 18, 2014 22:52:19 GMT
i am rather surprised by this thread!
hard silver soldering i always understood to be the old easylflo 2 and above. easyflo 2 and easyflo (johnson matthey trade names) being ideal for boiler making plus a few grades above. some of the higher melting point silver solders were not suitable due to lack of ductility. in the cadmium free environment of the UK only silverflo 55 and silverflo 24 are now recommended by J-M for silver soldering of copper boilers.
unless someone like J-M advised that 15% silver solder was ok for running over i would regard this is extremely doubtful practice for boiler work.
cheers, julian
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Post by runner42 on Oct 19, 2014 4:18:38 GMT
Hi Jim, thanks for that very specific answer on the ability of two different silver solders' ability to blend and the application of it to a possible work around. Something to remember for the future and use, but only as a last resort. Hi Julian, thanks for the information but to compare apples with apples it would be of benefit to know the silver content of silverflo 55 and silverflo 24? Is it 55% and 24%? Those who followed the thread Doris versus the Code will note that I opted for a square firehole ring and I used the fabrication of silver soldering of pieces of shaped copper together since I don't having a milling capability. The silver soldering of the firehole ring was done with the 15% silver solder and affixed to the firebox flangeplate. To ensure a pressure tight connection I would like to run 45% silver solder on the connection of the firehole ring to the firebox doorplate. If this approach has overwelming opposition I can readily cut it out and make another. Brian PS you can see the sand like appearance on the RHS of the firehole ring. .
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Post by Jim on Oct 19, 2014 6:23:44 GMT
Brian I used the 15% silver solder on the advice of my boiler inspector just for filling a spot where there was a small irregular gap/hole left after plugging the corners of the foundation ring. I then cleaned and fluxed the corner and ran the silver solder(Comweld 245 Cad bearing) into the joints including the spot I'd treated with the 15% silver solder.
I'd strongly advise you look at Julian's excellent series of photos and accompanying descriptions of the stages in building his boiler for 'Boxhill'. You should also talk to your boiler inspector.
Jim
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Post by cupalloys on Oct 19, 2014 9:37:11 GMT
The expression silver solder is normally applied to alloys that started life originally as brass ie copper/zinc to which silver has been added. In the 30s' cadmium was also added but the name stuck.
Alloys based on tin/lead are referred to in the trade as silver bearing soft solders.
Alloys based on copper and phosphorus are referred to as "phos alloys" or "self-fluxing" copper alloys. The 15% silver alloy is one of these also containing about 5% phosphorus. As outlined above it should not be used to braze coal fired copper boilers. The sulphur in the coal will attack the joint leading to premature failure. Gas fired boilers - no problem
The silver content of JM silver solder is denoted by the number that follows their trade name. Silverflo 55 and Silverflo 30 contain 55% and 30% respectively.
CuP Alloys silver solders all begin with 4. The last two digits indicate the silver content eg 455 and 430.
The silver content of other cadmium bearing alloys sold by trade name are
Easiflo 50% Easiflo2 42% Easiflo3 50% Argoflo 38% Argoswift 30% Argobond 23%
Yes you can run a silver solder over a copper phosphorus alloy but that is all you will do. You will not blend them to recreate a new joint. The remelt temperature of the 15% alloy will be in excess of 800 degrees C depending on the level of phosphorus burnt out of the alloy when it is first applied.
The keys to keeping costs to a minimum do not lie with 15% silver. They lie in proper joint designs good heating technique and understanding what the brazing/silver soldering process is about - CAPILLARY FLOW.
Finally Ian makes a good point. Keep records of your alloy purchases. Get Certificates of Conformity. They cost nothing and are readily available - or should be ! That argument also applies in Australia!
Keith
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jma1009
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Post by jma1009 on Oct 19, 2014 13:28:50 GMT
hi brian,
i could write a lot here,
but perhaps best to keep it short and simple -
1. you will need to make a new flanged firebox doorplate
2. you will need to make a new firehole ring
3. you will need this time to use the correct grade of silver solder for boiler work
4. as the cadmium ban doesnt apply to 'down under' i would recommend using cadmium stuff
5. there is a lot to be said for not overly complicating boiler making. the more joints and complications the more potential problems. for your firehole ring, although non prototypically 'square' you simply turn a small rebate either end on a piece of thick wall copper tube of the correct grade (put it on a mandrel to avoid the copper squashing and working loose in the chuck) and then anneal and squash to shape. do not peen over (contrary to what LBSC advises) the rebate as this restricts the gap needed for the silver solder to flow and penetrate on what is an important structural joint on the boiler
6. as ian and keith very correctly point out phosphorous containing 'cheap' silver solder is NOT suitable for miniature boiler making
7. step silver soldering of copper boilers is very much restricted now in the UK since the cadmium ban, as the range of silver solders now available that are suitable is much reduced. step silver soldering in any event whilst it might appear logical and attractive isnt easy and not for ideal for a first attempt at miniature boiler making
cheers, julian
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Post by runner42 on Oct 19, 2014 22:21:25 GMT
Hi Keith,
thanks for your detailed response. It appears that all 15% silver content solders contain phosphorous, so it is somewhat irrational that the code allows the use of 15% silver solder when phosphorous is not allowed for good reason. I didn't use it for cheapness it was for more for the fact that lower silver content silver solder has a higher melting point so I didn't want my fabricated door ring reflowing at a higher level of assembly. But it was a mistake that I was concerned about so the reason for the post.
Hi Julian,
yes you are right that the door ring will have to go. However, I don't envisage having to make a new firebox flange plate I can cut the protruding piece off and file the remaining door ring off the firebox flange plate. My fabrication approach of silver soldering two pieces of shaped copper together IMHO is OK. The larger inner piece connects the firebox flangeplate to the backhead and the smaller outer piece is only as a spacer between the two plates to maintain the gap the same as the foundation ring. If there is an inherent weakness in my design please let me know.
Brian
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steam4ian
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Post by steam4ian on Oct 19, 2014 22:31:49 GMT
Brian
Julian's advice unfortunately is sound, not a sound you would want to hear.
There may yet be hope of salvaging the work done to date. Keith suggest the phosphorus may/will have burnt out of the existing braze. If the P is no longer there then it cannot be attacked by the sulphur. Equally running a high silver solder over the top of the work may serve to keep the sulphur away from the joint if any P remains in it particularly if you cut back much of the P braze as possible using a dremel or similar.
Can I suggest you approach either Allan W or Bill Coles. Allan is already known to you and Bill is a former club boiler inspector and very approachable and logical. They may be able to patch things up for you without causing embarrassment to the present boiler inspectors.
Regards Ian
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steam4ian
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Post by steam4ian on Oct 19, 2014 22:37:21 GMT
Brian
Regarding 15% silver solders the Code and the supplier's data is ambiguous regarding whether 15% silver solder contains Phosphorus. One is just left with the strong impression that such alloys do contain P.
I have done plumbing and related copper work with Copper/Phosphorus rods and found them excellent to work with and never experienced the granulation that your work shows.
I still think you should get some local advice.
Ian
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Post by Jim on Oct 19, 2014 23:20:27 GMT
Brian Regarding 15% silver solders the Code and the supplier's data is ambiguous regarding whether 15% silver solder contains Phosphorus. One is just left with the strong impression that such alloys do contain P. I have done plumbing and related copper work with Copper/Phosphorus rods and found them excellent to work with and never experienced the granulation that your work shows. I still think you should get some local advice. Ian Hi Ian, I must correct my earlier comment about not detecting any hint of phosphorus in 15% silver solder. Having now seen the post by cupalloys and the reference to 'self fluxing'phos alloys a comment by my boiler inspector that the 15% was self fluxing makes sense. His advice to run some 45% over it wasn't to blend it as I'd assumed but to keep the sulfur away by creating a protective coat. While my use of the 15% SS was restricted to two small yet difficult areas, neither of them in the fire box I now have a much better idea of the 'whys' and "hows' regarding the processes at work. Thanks for clarifying the whole issue Ian which is now stored for future reference. Jim
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Post by runner42 on Oct 20, 2014 0:30:34 GMT
Hi Ian,
it appears that 15% silver solder residue must be removed from the firebox flangeplate that is in contact with the fire for it to be re-used with a new fire door ring. The inboard face as shown in the photograph is not so important because it is not in contact with the burning coal and therefore sulphur production. This can easily be done so I am hopeful that the flange plate can be re-used. I am even hopeful of removing the residue from the inboard face. I am getting good at re-working items since that appears to be par for the course for me. The upside is making mistakes you learn things you wouldn't otherwise have known doing it right first time.
Brian.
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Post by runner42 on Oct 25, 2014 21:45:37 GMT
I have a simple question on the practice of silver soldering flanged plates and similar. When silver soldering flanged plates the common assembly practice is to rivet the flanged plates in situ to assist in the close up of the gaps and to keep the flange plates in position during the soldering operation. My concern is that prefluxing the areas to be silver soldered before rivetting is required but how long can the fluxed components be left before silver soldering?
Brian
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jma1009
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Post by jma1009 on Oct 25, 2014 21:57:31 GMT
hi brian, my own experience is to use as few rivets as possible, and only the minimum required to hold the parts in place. closing up gaps should be avoided with rivets both as the gap can close up completely thereby avoiding full penetration by the silver solder of the joint, plus the parts ought to be closed up with the relevant gap required without the use of rivets. there is no need to flux between the joints if the parts are clean and cross hatched before silver soldering, generous flux either side being ok. however i dont allow more than 6 hours between these stages ie silver soldering. cheers, julian
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Post by ejparrott on Oct 26, 2014 9:20:52 GMT
With a barrel to throatplate joint I'll pop in 3 or 4 rivets, but I don't close them over, I just use them to align everything and keep them in place. I also use bronze screws and drill and tap the plates, but don't do them up so tight the joint gets closed up
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Post by runner42 on Oct 26, 2014 22:20:50 GMT
I suppose like many facets of human endevour, there is never complete aggreement on ways of doing things in ME and gap distance required for silver soldering seems to be one such issue. A fellow member when asked by me is how do I loosely rivet as required by the code, his reply was that it was unneccessary, just close the rivets up as normal. His rationale is that he has done a number of test pieces where the gap was smaller than that required by current wisdom as would be achieved by normal rivetting and silver soldered. In sectioning these test pieces he found that even in a completely closed gap silver solder had microscopically entered and formed a bond. The conclusion was that capillary force of the silver solder is so large as to provide a bond. The smaller the gap the greater the capillary action.
I present this as another viewpoint, but don't know enough to be sure either way.
Brian
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jma1009
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Post by jma1009 on Oct 26, 2014 22:31:29 GMT
hi brian, i would ask your fellow SASMEE member to show you his test pieces! i think he's completely wrong! however regardless of the above each side of the rivet must have silver solder added to the heads which is extremely difficult to remember and see in the panic of brazing up the joints - easy to miss one or a few, hence why i use as few as possible. with your type of boiler very few will be required as the waisted sides of the firebox parts hold everything together. you should be able to get a 2 thou feeler gauge around all the joints. anything more than 4 thou you need to dress the joints again. cheers, julian
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