Talk:Brazing

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Hi Folks, I just wanted to say something about what Brazing was good for. Why use it instead of welding? - Lobstericus.

Welding will often distort the original metal part, although the final (warped) item will have nearly uniform strength with the original metal part. Brazing, on the other hand, causes no distortion of the original metal part, but is still roughly 1/3 as strong as if welded. In many cases, this is strong enough, and the avoidance of distortion in the original metal parts is the key reason for using brazing instead of welding. Yaf 22:46, 8 February 2006 (UTC)

[edit] Soldering

Looking at this article and at Soldering, I can't see a specific difference between brazing and soldering. What is it, asside from being a different filler material with a hotter melting point? ―BenFrantzDale 05:50, 10 February 2006 (UTC)

The traditional difference is 800F. For fillers that melt above this temperature, it is considered brazing. For fillers that melt below this temperature, it is considered soldering. Arbitrary, yes, but it is what Manko and other reference books have always defined as the difference. Yaf 05:58, 10 February 2006 (UTC)

Thanks. Aside from that magic temperature, is there a qualitative difference between the processes? I'd imageine the important qualitative difference is the degree to which diffusion occurs between the filler and the material being brazed. Does that sound plausible?

I imagine there is another cutoff temperature to deliniate "braze welding" from "brazing". Is that correct? Do you know what temperature that is? Since it is "welding", I assume it is done hot enough to begin to melt the base material, or if not, at least cause significant diffusion. Is that right? ―BenFrantzDale 07:22, 10 February 2006 (UTC)

What follows is the defintion from the AWS Brazing Handbook

"BRAZING

DEFINITION AND GENERAL DESCRIPTION

Brazing joins materials by heating them in the presence of a filler metal having a liquidus above 84O0F (4500C) but below the solidus of the base metals. Heating may be provided by a variety of processes. The filler metal distributes itself between the closely fitted surfaces of the joint by capillary action. Brazing differs from soldering, in that soldering filler metals have a liquidus below 8400F (4500C).

Brazing with silver alloy filler metals is sometimes called silver soldering, a nonpreferred term. Silver brazing filler metals are not solders; they have liquidus temperatures above 8400F (4500C).

Brazing does not include the process known as braze welding. Braze welding is a method of welding with a brazing filler metal. In braze welding, the filler metal is melted and deposited in grooves and fillets exactly at the points where it is to be used. Capillary action is not a factor in distribution of the brazing filler metal. Indeed, limited base metal fusion may occur in braze welding."

My comments There are definite metallurgical reasons to use the 840 F figure. Others are used but this is the official AWS definition.

Brazing uses heat and , as with any other process involving heating metal, the possible distortion of the metal(s) involved as well as changes in the grain structure and other changes in basic material properties must be considered.

The flux does not interact with the materials being brazed but serves as a barrier and oxygen interceptor. It often has some cleaning properties including the ability to remove oxides but should not be counted on for this.

Titanium can be brazed several different ways. Titanium’s reactivity can make for very strong joints.

Ceramics can be brazed with a torch, induction, etc.

Using an abrasive to clean oil or grease physically removes some of it just as any wiping would. However to get the parts clean you need to use a saponifier that will change the oils and greases to soap. Oven cleaner woks well as do detergents.

The flux chars and adheres to the workpiece when it is used up and / or overheated. Warm flux can be extremely tenacious. Once the flux has cooled to room temperature it is much easier to remove. The goal is to use enough flux and a proper heating cycle so that the flux is not all used up.

When hot quenching remember that you are in effect, heat treating the materials. Quenching will change material properties.

Remember, also, that different materials have different coefficients of expansion and slow cooling will allow the joints to adjust slowly while fast quenching will lock in stress.

Pickling is widely used to remove oxides but pickling baths are generally not well maintained. Because it is a chemical reaction the bath gets used up and becomes less effective as does dishwater.

Tom Walz www.carbideprocessors.com Nov 7, 2006

[edit] External links

I'm moving the following links here: [1] [2] for discussion, as they seemed to have clear WP:COI issues, and possibly WP:EL issues. If there's support to add them back, then please do so. I'm neutral regarding the links... I'm not an expert on the topic, but it seems like if there's extra encyclopedic information there, it should be integrated into the article instead of relying on people to visit the other pages. --Interiot 20:47, 21 November 2006 (UTC)