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Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Carl,
I work with, on occasion, a One-Eyed Electroplater, who has been handling everything under the Sun for more than 60 years. He was careless, like not using rubber gloves rated for HF, which is important by the way.
I work with chemicals a lot as well, as I am an avid Inorganic Chemistry fan, take what you will from what I say, or Ignore it completely, I was just trying to say that I think you're being careless and might want to consider the risks you're taking, and that you might be causing harm to yourself and don't realize it.
We're not indestructable, accidents happen, but remember "An ounce of prevention, is worth a pound of cure."
Registered Member #9640
Joined: Wed Jan 16 2013, 07:53AM
Location: Albuquerque, New Mexico
Posts: 26
So kind of you to draw attention to my carelessness (and remind other readers that you're looking out for me). Ah, if only my close friends and neighbors and my dear mother were so attuned to the situational risk decisions in my life, I might never need to think for myself. Shoot, if my tastes in safety were really downmarket, I could even crowdsource the ol' judgment thing to people online whose names or backgrounds I didn't even know, and get them to do it for free. La vie facile!
Earlier in this thread I dispensed some gratuitous safety advice myself (about wearing gloves now and then, and maybe even goggles, blah blah blah). I offer analogous platitudes more frequently in the context of someone getting ready to leave my place, when I will tell that person to "Drive Safely." I mean it, I really do! Nothing kills like road hazards. And yet for some reason nobody pays much heed to my admonition: they peel out of there like nothing had just been said about safety. I wonder why that is. I'm shocked to see those people return alive, again and again. You'd almost think that something besides my smarmy expression of concern for life and vehicle was responsible for keeping them alive. Maybe Jesus.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Continuing our drift away from the thread topic, I respectfully think that conservative safety admonitions do belong here. Many readers are young and smart, and (like most teens) think they are indestructible. Better to point out risks that would never occur to them. And occasionally offer firsthand examples of life-changing injuries or very close calls, just from bad luck during some ill-advised procedure that is harmless 99% of the time.
On the other hand, dumbing things down too much is like crying wolf.
Old timers who know and understand the risks should be careful not to project a cavalier attitude toward safety. A noob might repeat the experiment with an apparently inocuous change, that turns something truly safe into something with 1% chance of biting really hard, or creating a latent injury. "Proud Mary" thinks we are collectively too eager to help when kids want to make x-rays at home. Is it right to just say, "online forums are part of today's environment for Darwinian selection"?
One of my favorite examples is a website of one John DeArmond, "Neon John", whom some of our plasma globe makers might know, or be. Check out the picture at upper left of , which I have reproduced below.
That thing on the table is an energized magnetron from a MWO. Shall we cry out in horror? At lower left of the page, John states that it's a safe demo, that he knows what he's doing, and enjoys the hand-warming aspect (aka diathermy). I believe him, but need to repeat: "Professional driver on closed course. Do not try this at home."
Registered Member #230
Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284
Okay Guys From 40 years experience in working with stainless
Hard solders should be avoided they will eventually let go --usually at the most inappropriate time. The welds look good but a bit of thermal cycling will fracture the weld leaving a perfectly clean surface on one or the other surfaces --proof of non compatibility.
your options are soft solder 60:40 is ok but you need a good acid flux -killed spirits of salts (ZnCl) works well with clean stainless. --do not over heat while using this otherwise you have to re-clean the SS. Soft solder with added silver also good same flux as above but wash it very carefully after soldering.
do not use lead free solders these are worse than hard solders as far as joint strength stickability goes
Stick welding with 316L arc rods is good but you need a good welder to use 1.6mm arc rods --I have used these for UHV work.
MIG welding for heavier sections works well pays to use a bit of shielding gas on the inside to minimise oxidization.
Tig the preferred option this again needs a good welder capable of running down to 2-5 amps with HF start (especially good for very thin stuff like bellows) again use some of the shielding gas on the inside to minimise oxidisation.
If you cannot do any of these things wel,l two pot epoxy is good.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've found a paper here on brazing stainless steel using copper:
While, in this instance, a vacuum furnace is used, it is possible using other methods.
The paper goes into some detail regarding why using copper is the preffered method in critical applications. I'm surprised no-one else has come accross this method of joining stainless, and it's quite possibly not required in this instance, but using copper to braze stainless is the preffered option in critical applications.
Regarding the OT posts in this thread, if you don't know what you are doing with HF, a splash on your hand often results in amputation of the whole arm. Calcium glutonate injections (even if given immediately, and how many of us have a syringe of it on the bench?) doesn't always prevent amputation.
As far as I'm aware, the only substances resistant to HF are guttapercha (natural rubber) and polythene (polyethylene). I usually put polythene bags over my hands when using it, even when very dilute.
Registered Member #3272
Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101
Hazmatt_(The Underdog) wrote ...
You will probably have to TIG it.
Oxy-Acetylene will cause the stainless to catch fire.
A big problem with torching stainless, and exposing it to an oxygen atmosphere, is that the Nickle content oxidizes, which you cannot solder to, and the Chromium diffuses, causing the metal to become brittle and crack. Get it too hot, and it will combust.
I was researching how to repair one of my stainless vacuum traps and found that oxidation is avoided by industry during welding/soldering by the use of an ammonia or intert gas atmosphere, and intense heating, but who has that capability in their backyard!
Most of us dont.
But if you TIG your workpiece, you should be okay.
I am sorry, but this is utter BS. Stainless is silver brazed all the time. Done it many, many times at work and I have also worked in the welding industry (I was a Miller certified tech). I have never, ever heard of stainless combusting.
Ammonia as a purge gas? You have got to be kidding. We use anhydrous ammonia for refrigeration at work and you dont want to be anywhere near that stuff. You can back purge with any inert gas. The simplest thing to do is put a splitter on the argon line if you are tigging and run a line to the inside of the pipe you are welding.
The main thing is dont overheat your metal, thats when you can sugar the stainless, this happens with tig as well. The best way is to preflux your parts. Cut silver brazing strips and set the up along the joint. Heat the parts evenly and the metal will flow. The braze will follow the torch though the joint as you make a good bond.
Use oxy-acet or oxy-propane. Either will do fine. I like the white flux, some people use the black flux, it is better for stainless. Stainless is very easy to solder braze. The right tools will help. If you dont have an oxy-fuel setup look on craigslist. There are people selling them all the time. I have two, One with a medium size acet bottle and a 150cu ft O2 bottle and a little portlable set with a MC and a 20cuft O2 bottle.
Bit of acetylene trivia, the two smallest bottles are called MC and B bottles. MC being the smallest. The name came from what they were used on as a source of lighting, MC was used for motorcycles, B bottles were used on buses. This is the reason for the angled valve as well on the MC, they were intended to be run with the bottle at an incline.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
I wanted to see if my stainless steel mesh "Chicken Wire" could be brazed, its 304 stainless, and as I used Oxy-propane, it burst into flames, much like overheating a Cerium "flint" striker. So yea, it can ignite, try it for yourself.
The Ammonia gas atmosphere is used on high production intense heating oven assembly lines as a purge gas. Not sure how they managed, but when I was looking at a company profile, that's what they said they did for their process. If that's not true, then that's fine, it's the way they did things. And they could have chosen any gas I guess, its what they used.
I've also used the white Sodium Flouride flux and silver bearing solder to try to fix my SS condensation trap, and it was garbage. Bought it from Cameron welding supply, brand new, never worked. As soon as it got hot, the Boric Acid in the mix became all gummy and prevented brazing.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Hazmatt_(The Underdog) wrote ...
I wanted to see if my stainless steel mesh "Chicken Wire" could be brazed, its 304 stainless, and as I used Oxy-propane, it burst into flames, much like overheating a Cerium "flint" striker. So yea, it can ignite, try it for yourself.
The Ammonia gas atmosphere is used on high production intense heating oven assembly lines as a purge gas. Not sure how they managed, but when I was looking at a company profile, that's what they said they did for their process. If that's not true, then that's fine, it's the way they did things. And they could have chosen any gas I guess, its what they used.
I've also used the white Sodium Flouride flux and silver bearing solder to try to fix my SS condensation trap, and it was garbage. Bought it from Cameron welding supply, brand new, never worked. As soon as it got hot, the Boric Acid in the mix became all gummy and prevented brazing.
Phosphoric Acid worked for me, with 60/40.
Boric acid does require hotter temperatures, but it does clean very well, due to it being more aggressive (and gets thicker as it does it's job).
I used to use a borax/boric acid mix, and just keep adding more borax as it thickened, or wiped it off and added more boric acid, but at the time I had a 50 kilo sack of each, and I used to use a carbon arc flame. Boric acid, once it's full of oxides, etc. does tend to come off as flying glass as the workpiece cools, though.
I think, when I was brazing copper to stainless, it was so that I could then solder to the copper, I do remember that it was surprisingly easy to get the copper to flow and stick, though.
Registered Member #3272
Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101
Hazmatt_(The Underdog) wrote ...
I wanted to see if my stainless steel mesh "Chicken Wire" could be brazed, its 304 stainless, and as I used Oxy-propane, it burst into flames, much like overheating a Cerium "flint" striker. So yea, it can ignite, try it for yourself.
The Ammonia gas atmosphere is used on high production intense heating oven assembly lines as a purge gas. Not sure how they managed, but when I was looking at a company profile, that's what they said they did for their process. If that's not true, then that's fine, it's the way they did things. And they could have chosen any gas I guess, its what they used.
Just about any metal will burn at high temps when it is chicken wire size. It will overshoot brazing temperature quickly and start vaporizing unless you are very careful.
Ammonia might be used in something like a massive welding furnace. To fill something like that with argon would cost a small fortune. It is also possible they are going for a specific reaction with the metal since ammonia is definitely reactive.
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Brazing Stainless Steel...
