soldering stainless steel

John

I am sorry have not replied earlier but I have been out all day.

The phosphoric acid was concentrated. By now you have probably realised it is not a very strong acid and is relatively safe. It does corrode stainless steel as British Steel discovered when they tried to introduce stainless steel domestic water piping - they could not successful get clean (flux free) soldered fittings after assembly.

I have no comment on the strength of the joints I produced. I was making small boundary layer total pressure tubes that had a life of less than an hour.

JA

Hi Thank you JA. The general consensus seems to be that soldering stainless is not easy at the best and impossible at worst. If I can get some phosphoric acid cheaply I'll try it but I don't think it's worth pursuing othethwise. I think a major problem with making a large assembly like a tender would be the poor heat conductivity which would lead to distortion. I made a steel guitar once and that was very difficult to solder all the seams - the thing bent every.way. Didn't matter too much, I wanted curves but it wouldn't suit a loco tender.

Bakers fluid was bought through ebay & delivered. No problem.

General consensus?

Soldering stainless steel is no more difficult than soldering copper.

You just need the right materials. Beware the cheap products and bargains available on eBay. If they don't work, they are very expensive and make the job difficult or impossible!

I bet the royal mail don't know that acid is being sent through the post!

Best of luck with the bakers fluid.

Keith

Im with Keith CuP alloys on this. Its not easy and you need the correct stuff to do the job. No short cuts or bodges seem to work , so why try.

bakers fluid is good stuff on the right material, not stainless

As usual, with all things soldering and brazing Keith is always right. Stainless steel does have some challenges when compared to eg brass, copper, mild steel, however you join it, whether soldered, brazed or welded. However, as Keith says using the right materials when coupled with the right techniques and principles will lead to success. A good start is to speak to someone with over 100 years of soldering and brazing experience available to them!

The Stayclean Stainless Liquid Flux supplied by CuP has a proven track record when soldering stainless. It appears to be expensive because it must be shipped by special carrier. Again, as Keith says if you can collect at the exhibitions such as Ally Pally next week you will more or less halve the cost.

Declaration of interest - I now own CuP Alloys.

Looks like another sale coming you way. Haha. Question : Could stainless be silver soldered & would that need any type of flux.

To Silver solder (braze) stainless you would need CuP's HT5 flux or Tenacity No5