Re: Welders, start your drooling
 

Brazing and soldering use essentially the same principle, it's just the material which is different. Braze is much stronger than lead or tin based solders, and needs a much higher temperature to do it.

There is a sort of half-way house which is "silver solder", that has much more strength than tin/lead solder but doesn't need quite the temperature of regular brazing. Silver solders come in a variety with melting points in the realms of 650-800C depending on the mix.

Just for info, this shows typical temperatures for tin/lead solder of different percentage mix

Tin/Lead Melting Point

40/60 460ºF (230ºC)
50/50 418ºF (214ºC)
60/40 374ºF (190ºC)
63/37 364ºF (183ºC)

95/5 434ºF (224ºC)

Re: Welders, start your drooling
 

That IS interesting, I expected a uniform slope to the mixes but not a curve, why is that? anyone know off the top of their heads? no worries if not, just a random question I was throwing out there.

Re: Welders, start your drooling
 

Essentially they are the same principle - a filler metal is melted into the joint between the parts to be joined, and the joined parts aren't disturbed. Welding is where the parts are brought to, or very near to, their melting point and become part of the joint themselves, whether or not a wire or rod is used.
There are several welding processes that use no wire or rods at all, the parts are joined directly, for example spot welds - where two electrodes are pressed together firmly either side of two sheets to be joined, a high current is passed between them causing localised melting and the metal to run together and be joined. With a spot weld the electrodes are two pins that make a small roughly circular welds, a variation is where the pins are replaced by wheels that roll across the surface making a seam weld.
There are other processes such as friction welding where the two parts are spun against each other with such force that the resulting friction causes heat, melting and thus a join is made. Forge welding, (the original kind of welding), where two hot parts are hammered together such that they fuse.

Re: Welders, start your drooling
 

The minimum is called the Eutectic. A common characteristic of metal alloys etc. Try Wiki.

adjective

adjective: eutectic

1. 1.
   relating to or denoting a mixture of substances (in fixed proportions) that melts and freezes at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them.
   
   
   
   

Re: Welders, start your drooling
 

For me, the difference is even more straightforward. I can't weld, I can't braze but I can solder! Wish I could weld like that though, however said it was almost art wasn't wrong.

Re: Welders, start your drooling
 

:smt104 :smt115 :cheers:

Cool! Thank you!

Re: Welders, start your drooling
 

I used to have to silver solder carbide tips in to stainless thin wall tubes, that was tricky, some of the trickiest joining two thingies I've ever had to do, had to be careful getting the carbide too hot or it went brittle.

I've done a fair bit of brazing too, getting the material very clean really helps, or it won't run very good.

Interesting thread for a change :)

Re: Welders, start your drooling
 

Just to add strange metal joining techniques.

I used to have to braze tips to cutting tools as a 16 yr old using induction brazing. No flames, no heat, just put the workpiece in the coil and it glows.

So let some impressionable kid, see you doing it. then put your hand in. see if they will put theirs in the ring.

But make sure they are not wearing a cheap ring.

Re: Welders, start your drooling
 

Eutectic mixtures are interesting when they cool because frequently one component will crystallise out of the melt until what remains is the euctectic mixture at which point the whole melt solidifies.

So if you melted 90% tin/10% lead and then cooled it slowly you would get slushy crystals of tin until you reached 183C when the remaining material would solidify. If you cool it quickly the tin crystals don't get time to grow and it appears to be a homogeneous alloy.

A nice example of how properties change depending on how quickly materials cool.