Effects of welding/brazing on heat treatment

[Rotate]

When you weld or braze a steel part which was hardened, isn't it likely that the heat will anneal it? To get around this, are parts welded first and then heat treated? This wouldn't be possible for brazing since the curie point would be higher than the melting temperature of the brazing rod. Is brazing simply not compatible with heat treating?

Is is possible to braze HSS to normal steel similar to the way carbide is brazed? If I remember correctly, I think this is what bi-metal is, but how is this done so that HSS does not lose hardness?

Albert

[SGW]

You've got the basic idea, I think. I don't see how you can heat-treat and then braze (or vice-versa), because either the brazing will undo the heat treatment or the heat treatment will melt the brazing.

For welding, I guess you'd weld first, then heat treat.

HSS is pretty difficult to anneal, so you might get away with silver soldering (around 1200 degrees) HSS to carbon steel. I don't know if brass brazing (more like 1800 degrees) would mess it up or not.

[docsteve66]

This is pure speculation, so take it with a grain of salt.
1. many times the partis heat treated all for economic reasons- the treat is really needed in just one area. So maybe you can "get away" with a repair if the break is in the right place. Not a good idea for parts in a critical place unless the immediate need justifies the risk.

2. I have no experience brazing or silver soldering HSS. But band saw blades I have done. I can't weld nor braze them except with the welder thatcomes with the saw. And they make a brittle section that must be annealed before use (actualy you anneal before grinding). But silver solder lasts well and is easy to do.

BTW: I think a lot of bladebreakage isbecause of the smaller wheels the blade goes around. I think loosening tension on blade for small diameter whels might lengthen the life. I see many small cracks on broken blades, it may be imagination though.

[bdarin]

I once welded a piece of scrap to a piece of good stuff so I could hold it in the bandsaw vise to cut it. Fat chance...the blade wouldn't even scratch it. The welding process alone had hardened the steel too much to cut. Had to anneal it to cut it. I cooled it in water before I tried to cut it so I guess I inadvertently hardened it just by welding it. I was a bit green at all this back then, didn't realize what was happening here. Now I know everything!!!

[Thrud]

Bimetal blades are made by electron beam or laser welding the HSS teeth or strip to the softer backing steel and then grinding to profile.

Japanese Samurai swords are Bimetal by definition. A hard steel billet hammer welded to the softer backing billet and folded over and over so the hard steel (edge) is on one side and the soft on the other - then pounded out into a blade. It is amazing what they could do 1500 years ago.

[This message has been edited by Thrud (edited 06-12-2002).]

[Peter S]

I have many boring bars, slotting tools etc. that I have made by easi-flowing (using Oxy-Acetylene,) HHS to steel shanks. There is no other operation required, just easi flo on and use. HHS gets red hot, but doesn't seem to suffer. Also have used for carbide tools, eg home made drills for hardened steel.
If you don't have easi-flo as a trade name in your part of the world, let me know, and I will try and get a better description. It is a reasonably low temp. rod.
You know, its so long since I made one of these, I can't remember what type of flame you use, its not neutral, I think carburising is correct..?

[This message has been edited by Peter S (edited 06-13-2002).]

[Rotate]

Hi Peter,

Never heard of "easi-flo". Is it a type of brazing rod? My internet search has turn up empty also. Do you remember who made it? Thanks.

Albert

[JCHannum]

It is low temperature silver solder.