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Mini anvil brazing project

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Can anyone tell me what the steps for doing a brazed face to a cast iron anvil are? It's tiny. Maybe twenty pounds.  At most.  Not worth it for the size, just for the experience.  Face area is 2x6". I have some 1/2" AR500 plate I was thinking of using a piece of as a surface. Did a search of the forums, came up with a bit of info, but if anyone's willing to walk me through a step by step on this I'd be grateful.

Here's hoping my request was not too brazin'.

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im no expert so wait till others who know more comment.


this is what I think......

maybe mill the top so when you have added the new plate it is about the same height as now or a little bit taller,

flux and cover both surfaces in braze.

when cooled place the new plate on top and heat evenly till braze melts

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Yup you want dead flat to dead flat; what will the brazing temps do to the heat treat of the plate?  Brazing followed by quenching is NOT a good idea when you are using different materials as they contact at a different rate.

I'd search on furnace brazing as that's what you really plan on doing.

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Did a bit of looking at furnace brazing, though a lot of the initial info has to do with automated processes..  Also found a manufacturer recommendation to keep the working temp around 400F in order to preserve the properties of the AR500. Suffices to say that the temp range for brazing/silver soldering is past that.. 

What about controlling the HAZ so as to preserve the properties of the steel plate to at least some extent?  

Are there ways to manage this? Heating the whole mess to brazing temp doesn't look like a very viable option...?

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That is sort of what I'd assumed.  The smaller scale of this project doesn't make it simpler!

Edit: I'm seeing numbers for soft solders that put the tensile strength in the 4000+ psi range, and the temps are close. Thoughts?

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We used to braze high carbon steel calks onto low carbon horseshoes. We used a length of copper wire for the solder. We used borax for flux. The calk and shoe were held tightly together with specially made tongs or a sharp nib was drawn at a right angle on the end of the calk, and the cold nib was driven into the hot shoe to hold them together. When the copper melted at about 1,985F we withdrew the piece from the forge fire and applied steady pressure on the calk with a hammer, not hitting, just applying pressure. This enhances the capillary action which is taking place. The to-be brazed surfaces must be clean and a tight fit. If there is daylight, the capillary action won't take place. To get a clean looking finished job, we gave the piece a one second quench. The quench popped cuprous oxides to the surface and these "flakes" were quickly wire brushed off.

I say all this just because it needed to be in print. It won't solve your anvil problem. Proprietary brass brazing rod is easier to use than copper because it melts at about 1,600F. There are special alloy fluxes which are available, one called a white flux and one, a black flux. They might serve better than plain borax. In any event, both anvil and face should be at a bright cherry red to allow the brass to flow, and again, steady pressure should be applied once the brass is liquid and is wetting both surfaces to be brazed.

Sorry I can't give you a blow by blow description of what exactly to do.

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Exo MY MAN! I've been wanting to do exactly that for years I just don't have a reasonable size test subject. 

I can't give you a blow by blow how to but I'll more than happily offer my musings. : Match the joint surfaces as closely as possible, the thinner the solder layer the stronger the bond. Braze is a hard solder and there are softer versions that work just fine on steels. There are silver solders with a great deal of thermal shock resistance, you can drop them in water as soon as it solidifies without ill effect. I haven't looked into silver solders in a bunch of years so can't suggest one in particular.

I did however do some experimenting when I got the joyous job of silver soldering new carbides on worn drill bits. I tried dropping common brazed steel in water as soon as it solidified with no ill effects. Heck I experimented with all the rods I tried and very few joins failed. 

IIRC the ASO I was going to experiment with weighs around 100lbs. and quenching the steel face was a concern. I'd planned on spending a night on a sand bar of a local river and watching a large fire all night. When close to brazing temp, break it out of the fire and heat the face plate with a rose bud torch to complete the braze. Let it cool to a suitable temp and use a 2" trash pump and river water to quench. Let residual heat in the body draw the temper and stop the draw with the trash pump.

I'd planned on using a clamp similar to what you use for Mokume Gane and my air impact wrench to keep the pressure on as everything heats up. However if I used the torch simply wiring it together probably would've worked just fine.

Sheet brazing material and paste flux is a good maybe but I'd experimented with pre fluxed rod: filings, clippings and various length pieces clamped in the join, they worked okay. 

I just couldn't convince enough minions it'd be fun to haul a couple pickup loads of cut firewood out on the river bar, keep watch and tend fire all night. I'd look for a hard solder with a brazing temp JUST below the critical temp of the steel I was going to use for the face. Use enough silver solder it'd squeeze out out of the join as an indicator.  

A 2" trash pump will produce about 200 gl/min and they're called "trash" pumps because they will pass solid junk of reasonable size, say around 1/4" +/- so stuff in the river is less likely to stop your quench. This strong a flow will prevent steam from forming pockets on the face's surface causing uneven hardening.

So yeah, I've given brazing a steel face on a cast iron ASO some thought. Heck it might even be something I can use a piece of grader blade for!:o Hmmmm, I wonder if my latest bunch of minions are more gullible? :ph34r:

Frosty The Lucky.

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