The terms, brazing, soldering, welding, bronze, brass and so on are often confusing, especially when dealing with US and British common usage and technical descriptions.
Technically, at least in the US, brazing means heating an alloy filler metal until it reaches a liquidus state and "wetts" or freely flows over the heated surfaces of the pieces being joined.
The flow of molten filler can be via capillary action into a gap between pieces such as a lug and tube or it can also mean forming a joint by building up a fillet between the pieces.
In US terminology brazing is synonymous with brass filler rod but there are a lot of different filler materials used for joining various metals. For example there are special alloys for joining aluminum, copper, nickel, cast iron and so on.
The modern definition of Brass is a gold colored alloy composed of Copper with as much as 45% Zinc. Other alloys can be added for corrosion resistance, strength etc.
Most common "Brazing" rod sold in the US is made of a "Brass" alloy unless differentiated.
Bronze on the other hand has been in use for at least 5000 years and was originally an alloy of Copper with up to 12% Tin. You've heard of the Bronze Age, ever hear of the Brass Age? ;-)
In the US there are a wide variety of alloys referred to as Bronze: Aluminum Bronze, Phosphor Bronze, Manganese Bronze, Nickel Bronze.
Commercial Bronze and Architectural Bronze are actually forms of Brass because they contain Zinc instead of Tin.
Back in the mid 70s I bought about 5 pounds of Bronze filler rod that Proteus Design was importing from the UK. I found that the melting temperature was much higher than the standard Brass rod that I got from the local welding supply companies. I didn't measure the temperature but it took a lot longer to reach the liquidus stage and flow into lugs and dropouts.
Welding usually indicates heating metal parts at the contact area until they melt and fuse.
The term welding is frequently used (or misused) to describe any form of joining materials that involves the application of heat for example welding plastics. So, "brazing" could mistakenly be called "welding".
The heat generated from any form of electric arc welding causes some of the carbon in the steel near the weld to migrate into the weld itself.
This results in decarburization of the steel in the heat affected zone around the weld which reduces it's strength plus the additional carbon in the weld area can cause embrittlement.
It's not as big problem in thicker wall tubing or larger cross section parts. It's also less of a problem with low carbon steels such as 1018.
Thin cross section parts made of welded medium carbon steels such as 4130 and 531 should be heat treated after welding to prevent cracking.
This link talks about welding 4130 race car frames:
http://www.netwelding.com/
The UK and the US - two peoples separated by a common language...
Chas. Colerich Oakland, Ca USA
Paul Grosvenor wrote:
> "Reynolds itself says, "Don't weld Reynolds 531 or 753 tubing. It's no good
> for this purpose.""
>
> I have also seen that, in Reynolds literature/spec sheets. Also you cannot
> braze 531, but you can "bronze weld" it. Apparently brazing gets the 531
> too
> hot & it can go brittle, with potentially disastrous results! So Reynolds
> recommend "Bronze Welding", where the bronze is used as a filler metal,
> which holds the 531 tubing in place. Before you all think I am talking
> rubbish, I can tell you that I don't quite understand the difference
> between
> "Brazing" & "Bronze Welding" either!!
>
> Now, having said all that, remember "THRUST" the world speed record car
> driven by Richard Noble back in the eighties? The chassis/space frame of
> that car was made from Reynolds 531 (that's why the car carried TI Reynolds
> logo's). Well, I met Ken Sedgeley, the guy who built the chassis for the
> car, and he told us that the complete chassis was open-arc, or stick,
> welded. That is electric welded, no argon shield, not MIG, nor TIG.
> Because they were using rectangular section tube it was a better way of
> construction, according to Ken.
>
> Which defeats all the Reynolds advice and folklore.
>
> You go figure!!!!!!
>
> But 531 is definitely seamless
> Sorry if it is "Off Topic" but it definitely has a bearing on the
> subject - and it was back in the (early) eighties!!!!
>
> Regards
> Paul,
> Stourbridge, West Midlands
> ENGLAND