Project - Build a small steel frame - Braze/Weld?

[fossill]

Hello All. A bit of background:

Awhile back I came up with an idea for a lamp, however it required that I build sometype of frame. I began my project with square rods of steel from the local homedepot found in the welding area. The steel "bars" were probably 1-3 ft long and are probably 1/4" by 1/4". I cut all the steel to size and then it was time to join the pieces to construct the frame.

At the time I didn't realize what I was getting myself into, however I really wanted the project to come together. I also did not have a garage at the time so trying options that didn't require gas/torches would be first choice. After applying some jbweld to a few joints and having them break under any stress, I realized that that wasn't going to work (I guess just not enough area for the jb to take hold).

So, this brings us up to date. Before I knew what brazing was, I thought soldering/welding were my only options. From what I've read, it seems to me that welding would be overkill. I've tried some soldering, but either I don't have the right flux/solder or I didn't have the material clean enough...I'm not sure. In any case, that the soldering failure forced me to explore my options. After reading much about brazing, I figure that is what I need to do, however I'm coming up with some questions:

1) Is even brazing overkill? Should I be able to do this with solder? I can't be positive, but I believe that my steel is something called "welding steel"? Atleast that is what it was called at homedepot...so I'm not sure if its covered in any kind of alloy or what...but I'm pretty sure its not stainless.

2) If brazing is the best option, I've read that the steel to be joined should be heated broadly. Unfortunately, this frame is not that big and at some places joints may be as close as about 5". If i'm heating this area broadly after already making one joint, I believe that this will reheat the previous joint and cause that filler metal to remelt! What can I do about this (if anything)?

Thanks for the help! Lemme know if there is any more info I can provide that would be helpful to finding a solution.

 

[Metalguy]

Easiest way to go is buy/rent a small "wire-feeder" type welder and use "cored wire" to weld it together.

Brazing is much trickier than welding.

 

[mdighe]

Hi

The welding steel is most probably a low carbon steel such as 1008/1010.

How big is your part?
The best way to braze would be decided by the size of the part.

We have torch brazed parts that are as small as 1 inch long successfully. The advantage of brazing is that the joint strength is much better than solder joints and you do nto have to worry about HAZ as in case of welding. Also, the cosmetic appearance of brazed joint is much better than welded joints. You do not have a bead to worry about.

If the braze joint is designed correctly, the failure will occur in the base metal and not in the joint

Small pieces (5-6" cubes) can be brazed in continuous furnaces with copper.

If you are interested in torch brazing, silver tin alloys can be used at low temperatures. With torch brazing you will have to use a flux. The brazing temperatures used for this are about 1200-1400F. Furnace brazing temperatures are much higher.

Hope this helps

 

[tomwalz]

Here's an on line book. It is about brazing tungsten carbide to steel but the brazing basics are there.

http://www.carbideprocessors.com/Brazing/book/index.htm

Start with a short overview

http://www.carbideprocessors.com/Brazing/book/04.htm

Also look at the chapters on cleanliness and temperature as those seem to be two areas where problems frequently occur.

Tom

 

[fossill]

Thanks all for the info. A bit more on the steel pieces:

I'm going from memory but I would say they are 1/4" x 1/4" x varies (HxWxL). The length of the pieces vary from about 4" to maybe 12".

The goal for me is to accomplish this frame with as little $$ invested as possible, so if I can get away with torch brazing this sucker myself, that would be happiest. If it comes down to me having to take this thing and my plans to the local welder, I'd probably ditch the project as the rest of the material costs next to nothing (plus, what the fun of having somebody do it for you?).

It seemed that so far (from what I've read) that I was going to use pre-fluxed bronze. But like I said before, no matter the filler material, won't I run into problems when brazing another joint just inches away? In this case, do I just keep the heat more localized?

I'll have to check those links, thanks!

 

[strokersix]

You can use a heat sink on the previously brazed joint. It can be a simple as clamping another piece of steel on the joint or even the mass of a c-clamp itself will provide enough heat sink to protect the already brazed joint.

 

[fossill]

Ohhhhhh yeah! DUH......now thats a clever solution! Thanks stroker!