Metal and Fire

[Osvaldd]

Was given this burned vice, literally picked out off a pile of ashes. It looks pretty bad. Was wondering if fire changes metal properties, like make it brittle or something?I noticed the spring for quick release has lost its springiness due to fire I presume.

 

[Trevanion]

If the fire was hot enough it would ruin any hardness and tempering in any parts that had it, like the spring you mentioned. The castings may have also distorted from the heat and any ferrous material that's been in a fire seems to rust really badly after the fact, as is the case here. I don't believe the slider bars or the thread are hardened so not much might have happened to them.

Should be ok to use so long as you get a new spring and give it a good clean! You will also need the plate at the back end that bridges the two slider bars and the threaded rod otherwise the thread will just unwind itself.

 

[ED65]

There is a chance the steel parts, other than the spring and components of the QR, are all fine on this if they're mild steel. The cast iron is another story.

It's quite a lot of work to get the vice clean enough to test, to check if the castings will crack under pressure and I think you'd want to do that if you intend to use the vice and trust it.

 

[MusicMan]

The cast iron should also be fine as long as it has not cracked. Could even have improved the microstructure a bit. Yes, heating the spring will have caused it to soften. It implies the fire was fairly hot, several hundred degrees. If it isn't cracked and can still be aligned go ahead. As Trevanion said, there are some parts missing.

 

[Craig Marsh]

I asked a similar question about some engine parts that had suffered the same fate. Interestingly, a big concern was whether the firefighters blasted water into the shed while everything was hot. If so, the concern is the uncontrolled quenching process may have cracked items, and only magnafluxing the pieces would tell the full story of any damage.

 

[heimlaga]

Cast iron stands up to heat very well.

What can happen to cast iron in a fire is:
1. The heat releases residual stresses from the casting process and makes the cast iron warp or creates new stresses through uneven heating and cooling. This may happen or not. In general there is a lot less warpage if the piece has been heated equally from all sides which is likely to happen to avice mounted to a bench.
2. Cracks that form when the iron is hot and the firefighters spray water on it.
3. Some spots are hardened and become very brittle by rapid cooling when hot and sprayed with water.

You can check for warpage using common layout tools to chech whether parts still align and fit together.

You can check for cracks by suspending the part from a rope and knocking on it very lightly vith a hammer while listening to the ring. The method isn't 100% but you are likely to detect cracks if there are any.

You can check for hardening with a very light stroke with a not very good file. It will just skid on hardened cast iron which is hard enough to dull the file. If you find any you can use a blow torch or wood fire to heat the part so it goes soft.

In my oppinion that vice is certainly worth a try at rebuilding it!

 

[Osvaldd]

Well, finally managed to clean that vice, some of that red colour which I assume it burned paint, is very stubborn. I tried soap, wire brush, power washing, kerosene, white spirit - it doesn’t want to come off completely but it looks better now. Discovered a hairline crack next to the rods, not sure if its to do with fire or abuse. Strengthened with two bolts, will see if it lasts. And decided to forgo the quick release mechanism, that's why there’s a wee white pipe holding the nut in place. Working great now.

 

[ED65]

That's looking a lot better, nice job!

...some of that red colour which I assume it burned paint, is very stubborn. I tried soap, wire brush, power washing, kerosene, white spirit - it doesn’t want to come off completely but it looks better now.

Burnt paint would probably flake off under fingernail pressure, it's rust. Rust can be incredibly tenacious and only chemical removal, electrolysis, wire wheeling or sanding will reveal the native metal colour. You don't have to go that far naturally, pieces are perfectly serviceable with some rust remaining, and how the vice looks in the first pic is exactly how some like an old vice to look prior to oiling or waxing.

 

[Trevanion]

That crack almost looks like it had been brazed at some point with the splotchiness and porosity around it. You should try sanding or filing a little bit of the surface over the crack and see if any brass colours start showing, it would have been a repair then. The heat of the fire probably expanded the casting so much causing it to crack worse if there was already a hairline crack or a repair. But the bolts will hold it together just fine!

 

[Osvaldd]

That crack almost looks like it had been brazed at some point!

It's super glue before tightening the bolts I poured some glue in the crack.

 

[Osvaldd]

Burnt paint would probably flake off under fingernail pressure, it's rust. .

I did soak smaller parts in citric acid solution for a few days, It didn't do anything, this red patchy colour still remained. If it's rust it should've been gone by now, but its not paint either since I don't think the spring was painted. It also stains your fingers a little. Very odd.

 

[Osvaldd]

Another one arrived last night, considerably worse condition, hairline crack in the exact same place as the other one.

 

[ED65]

I did soak smaller parts in citric acid solution for a few days, It didn't do anything, this red patchy colour still remained.

Some of that may be fire scale/mill scale (tough stuff) but rust generally is an odd duck, it comes in multiple forms and structurally it can be very variable. Individual patches can be incredibly recalcitrant, when similar-looking rust elsewhere on the same piece (sometimes right beside it!) releases early to an acid or molasses soak the stubborn bits remain firmly adhered, and they're hard as heck.

On stuff that was very heavy rusted or was rusty for a long time I frequently find small patches or indicvidual flakes of rust like this. Even after many days in a vinegar+salt solution or a fortnight in molasses, with periodic wire brushings to help the process along, some still won't submit to a drill-powered wire wheel.

If using electrolysis you see them too, small bits that hold out long after the rest of the rust has flaked away or been turned to black sludge.

If it's rust it should've been gone by now...

Rust removal doesn't go by a set timescale, it takes as long as it takes. Sometimes you have to leave something soaking for longer.

I just finished sharpening an Aven Filemaster, which had previously been de-rusted, and even after five more days in vinegar there were still four stubborn bits of rust near the tip. So perhaps nine days total in vinegar and they clung well enough to resist a good wire brushing and needed to be flaked off with a sharp tool.