soldering problem

[DJones]

OK, how do I clean a fitted steel part that refuses to tin. I'm using Brownells HI-TEMP Hi-Force 44 and copper bond flux. My first try ended in total disaster, after talking with a Tech at Brownells we decided that the flux was not working. I later checked and discovered the flux has a one year shelf life. Replaced the flux and the new bottle works much better, but I'm still having trouble with getting the parts to tin, very spotty coverage. I did some practice runs on scrap pieces with low temp Hi-Force 44, common soft solder and some silver just to check myself and had no problems. I tried the High Temp, Hi-Force 44 on my parts and later a test piece and still no go. I'm thinking it's a cleaning problem. I've scrubbed both parts with cleanser and water and then denatured alcohol. I've tried to think of what I've done that would have contaminated the surface of both parts and how to correct it. I need to clean the parts with changing the dimensions significantly.

Any thoughts would be appreciated.

[mwechtal]

OK, how do I clean a fitted steel part that refuses to tin. I'm using Brownells HI-TEMP Hi-Force 44 and copper bond flux. My first try ended in total disaster, after talking with a Tech at Brownells we decided that the flux was not working. I later checked and discovered the flux has a one year shelf life. Replaced the flux and the new bottle works much better, but I'm still having trouble with getting the parts to tin, very spotty coverage. I did some practice runs on scrap pieces with low temp Hi-Force 44, common soft solder and some silver just to check myself and had no problems. I tried the High Temp, Hi-Force 44 on my parts and later a test piece and still no go. I'm thinking it's a cleaning problem. I've scrubbed both parts with cleanser and water and then denatured alcohol. I've tried to think of what I've done that would have contaminated the surface of both parts and how to correct it. I need to clean the parts with changing the dimensions significantly.

Any thoughts would be appreciated.

I have at times used a Stainless Steel brush on the hot part. I just pull the torch away, and scrub a few strokes, put the torch back on, and maybe add some solder. With ordinary 50/50 Lead/Tin solder it has worked for me.

[RWO]

I have always used the regular Hi-Force 44 solder and Comet # 4 flux. I have never had a problem with any kind of steel, brass, etc. Comet #4 has no shelf life problem. I have a big bottle that is at least 10 years old and it still works perfectly.

As for activating your surfaces to take the solder, dipping the degreased parts in 50-50 muratic acid-water solution for 20 or 30 sec with make them chemically clean and ready to solder. Just be sure to neutralize the dipped parts in a baking soda -water solution afterwards as they will rust in a flash.

RWO

[rolland]

If you are using oxy/ace torch you may be too hot I have always found that you clean the part and get all the oil out of it ( I soak in acetone). after cleaning flux the parts and apply indirect heat don't put the flame any where near the surface you want solder on. tin the part and wipe with some flux I
use a "Q" tip soaked in flux to wipe after the solder melts so you have a good clean tinned surface. clamp the parts together and heat and watch for the solder to flow if you need a little more then you can add solder you should get a capillary action .
I have found the biggest problem with silver solder is you can easily get it too hot then it will bead up and not work. I use map gas for most of my silver soldering and stay away from the oxy/ace as it gets too hot to quick (at least for me.
Hope that makes sense, of course it does to me but then I wrote it

[bob_s]

If your original flux was old, was the solder also old?

Could be oxides on the solder itself, try cleaning it!

[DJones]

Thanks for the replies.

I am using my propane torch and heating the part and touching the solder to the part. I am quite sure I'm not getting the material too hot as there is no beading, the solder spreads, but simply refuses to penetrate/displace the flux and tin the surface. The solder is a fresh batch.

I've not used this solder before but want to use it for it's high strength, 38,000 psi, and the temperature range, 650 degrees, will allow me to go back and soft solder some of the remaining parts on without having to fixture up quite so tight to keep this part in place.

I'm no expert, but I don't normally have any significant problems when soldering or brazing. I'm still thinking it is a contamination problem, but can't put my finger on what I did that is causing the problem or how to clean it well enough to get the solder to flow and stick.

I guess I'll just keep trying and see what develops.

Again, thanks for the replies.

[Stepside]

Whenever I use a silver bearing solder I dip the solder in the same flux I use on the parts. I also use a barely carburizing OxAcet flame. As to "too hot", never stop moving your flame and put more of the heat into the heavier part.

[38_Cal]

Try taking some new 320 grit paper and wrapping it around a wood block shaped to the area you're trying to tin. Lightly sand the area on the hot part, quickly flux it and add solder. You can get things too hot even without the solder beading...the flux will essentially burn in and contaminate the part rather than clean it.

David

[Kibby]

I also soak in acetone. Preheating, and a quick wipe with a clean wet cotton rag also works to remove any residue. It literally steams any dirt right off.

[DJones]

Well guys I hate to admit it, but I finally gave up, cleaned the parts and used the lower temp, 475 degree Hi-Force 44 instead of the 650 degree version. Both parts tinned easily and the parts went together with no problems. I guess I'll never know what was wrong, but I couldn't get the higher temp stuff to work no matter what I did.

Thanks for all the advice. Sorry that I can't report success with the original problem.