It's not like I've never soldered before....

[Cedge]

I've got a small but important repair to make to make things right for a client who purchased what we both believed to be a class one condition steam engine. In order to fix the problem, I need to solder an end plug into a 3/4 brass tube which will then be soldered into a threaded bung. The whole assembly then has to be fitted and soldered into a toy engine boiler. I knew the repair was going to be a little tricky, so I've taken my time cogitating the most effect and safe way to approach the repair.

I've soldered brass parts and pieces together many times and consider my self to be relatively proficient, working with several grades of solder, ranging from old fashioned lead/tin all the way to Silver solder. Once I learned the process, few sessions ever gave me any problems.

That was the case, until last evening. I turned the plug to fit into the thin wall brass tube, leaving about .005 for the solder to have room to flow. I cleaned everything well, fluxed both pieces to get a nice clean etched surface and proceeded to heat the two fitted pieces with my hand held propane torch. This particular project really needs to use lead/tin, since the main body of the piece can't be heated hot enough to use silver solder. (don't get excited... the boiler is riveted for strength and is safety protected at less than 1 bar or 15 psi) By Hobson's choice, I opted to use the new fangled no lead solder we're having to put up with these days.

The subtantial brass plug took a very nice tinning and, with a bit of pressure, slipped into the thin wall brass tube. A light application of liquid flux and I began applying most of the heat to the solid plug with enough on the tube to get it glowing. I watched the solder go molten, gave the tube a 1/4 turn twist and left the heat on it for a little longer. I then let the assembly cool in the night air. When it cooled to touch, I picked it up, gave the end a tug and it slid right apart, in my hand.

For some reason, the brass tube never bonded to the solder. Upon closer inspection, it appeared perfectly clean, with zero residual solder on the inner surface. Two more attempts resulted in the same failure. I'm a little puzzled now as to what is causing the problem. Both pieces are brass, of unkown type, but they simply do not wish to be mated.

Any ideas?... anyone?

Steve

 

[hitandmissman]

Are you positive one of those pieces is not just brass coated and the base metal something else?? Can these be replaces with something new and known to be solid brass.

 

[Cedge]

Hit....
I'm considering switching to copper, but will need to check some tolerance requirements.

Steve

 

[Metal Butcher]

Might be the solder. I remember trying to solder 'something' together with Aim Free 97-3 wire solder and it wouldn't flow or stick. The stuff is poop on brass. I think Its plumbing solder for use on copper pipes.

-MB

 

[Metal Butcher]

I turned the plug to fit into the thin wall brass tube, leaving about .005 for the solder to have room to flow.

Any ideas?... anyone?

Steve

Steve, on brass I found that by using a gap of .001" with a 30% tin solder and rosin flux produces a very strong joint. The solder will flow through this thin gap towards the heat source. The thinner the solder the stronger the joint. No need to pile the stuff on like caulking.

Its the only solder and method that I use any more.

EDIT. I think I know what the problem is. The tube over heated by the time the plug got hot enough to melt the solder, and by then the flux had burned off the tube and its surface became oxidized. Try putting a piece of regular solder in the (cleaned) tube with plug and flux in place. Heat the end (of the plug) to melt and draw the solder towards the source of heat.

If you must tin, as a rule tin the smaller or thinner piece, and apply the heat 'only' to the larger piece.

I think the lead free stuff has a higher melt temp than regular leaded solder, and its easy to over heat and burn the flux.

With out seeing it my advise might be nothing more than a bad guess...



-MB

 

[js2112au]

I think the lead free stuff has a higher melt temp than regular leaded solder, and its easy to over heat and burn the flux.

I've a couple of spools of the old leaded solder (fine elctronics grade but I use it for just about everything) from many years ago when the service company I worked for would supply us field techs with everything we needed (and a lot extra that we didn't really need at the time). They say the lead free solder is better for us, less toxic apparently, but from the smell of it I'd disagree. Having both available to me now I still prefer the original.

I've used the older leaded solder on a few recent brass constructions and I never have any problems - it's very obliging and it just works.

 

[Spurry]

From the description given it sounds like the part overheated, as already stated. For soft soldering, either a large soldering iron or one of those teeny weeny torches are usually adaquate.

Would have to agree that the old tin/lead solder works best. I have read that if you try to use the old solder on something that has already been soldered with lead-free, the results are very poor.

Pete

 

[Ned Ludd]

Hi Steve,
I think you answered your own question.
"A light application of liquid flux and I began applying most of the heat to the solid plug with enough on the tube to get it glowing"
Soft solder should never get to glowing, think more like soldering iron rather than oxy-acetylene.
Ned

 

[jthulin]

I tend to agree with Ned; "glowing" jumped out at me too! A slow application of heat to the heavy part to the point where the solder flows and no more should do the trick.

 

[Cedge]

I think you guys are probably right about the heat. The metal is super thin so I'll have to try a different approach to heat application.

 

[krv3000]

HI you may all no this all redye but led free solder has a hire melting point than the old tin led solder and is not as flexible plus not all fluxes are compatibel with the led free stuf

 

[Admiral_dk]

The European Union decided that we have way too much lead, cadmium etc. going to our landfields and I can't object to that in any way - they're right - But the cure has been a huge problem for the electronic industry.
Lead free solder has noway near the strength of 60%/40% lead / tin solder or worse, the much more superior "silversolder" 57% / 40% / 3% (nothing to do with what you guys consider silversolder).

This has forced the electronic industry to evolve new and better coatings for components and the PCBs + different soldering profiles (preheat, solder temp, etc.) and new flux types, in order to cure these problems with leadfree solder. This has to a very large degree solved the problems in production, but a large number still exists in repair.

It's almost impossible to make a decent solder joint on a PCB or components that are a few weeks old, because of oxidation ...!

For that reason I'll try to keep a decent supply off the above mentioned "silversolder", it's simply superior to modern leadfree solder when doing repairs.

It must be said that soft solder - just as it's hard solder counterpart, doesn't like to be treated to too much heat.

I've NEVER been able to use soft solder on brass.

 

[Spurry]

Brass is one of the easiest materials to soft solder. ;D I suspect that you are trying to get things too hot. This item is split along the front slot and soldered from two parts.
(it's just a litle gadget to screw hooks in using a small battery drill)

Pete

 

[Ken I]

Please note that the beurocrats that came up with the lead free solder idea exempted Military, Aerospace and Medical applications.

Why ?

They knew damn well the stuff is problematical and don't want planes falling from the skies.

So we (who elected these morons) now have to pay to be used as guinea pigs for who knows how many years of shoddy unreliable electronics until the methodologies come right or they give up.

Screw that.

The lead free solders are proving extremely difficult to use in production environments and I don't see the point of even bothering from a hobby point of view.

The lead free solders are in fact consideraby more toxic - particularly the fumes.

I grew up in a house with 100% lead plumbing - and it hasn't affected me in the slightest - just ask any of the talking vegetables that follow me around all day.

Ken

 

[js2112au]

I got a new catalogue this week from an online supplier of test/measurement/scientific/electronics..... stuff.

I was interested to note in their tools section - solder & soldering equip, that the lead free solder has now been relegated to a subsection with a bunch of "if you really must buy this then be warned...." notes.

It seems as far as this supplier is concerned leaded solder is back in fashion.