Slag removal after HT

EdCaffreyMS

"The Montana Bladesmith"
When you say "slag", do you mean the scale that forms when heat treating/quenching? Unless you're doing something wrong, there should only be minimal scale, that is easily removed on the belt grinder. If you're talking about forge scale....that's a different animal. Trying to remove forge scale with belts will cost you a fortune in belts. For that process, I use a 7" angle grinder.
 

Nick Riggi

Well-Known Member
Yes. I don't get a thick scale after my quench, but I get the burnt oil stain that tskes some work to get back to clean ground metal.

Was wondering if anyone had some secrets to get that off easily or keep it from getting so baked on.

I was going to try some white vinegar after the quench and prior to the tempering cycle
 

C Craft

Well-Known Member
Go to the mission buy you and old crockpot heat some white vinegar. Let is soak on low over night. May want to put it outside because of the fumes. Next morning the majority will rinse off!! Neutralize with a baking soda bath and dry. Then if you choose to sand it won't eat up the paper!!
 

EdCaffreyMS

"The Montana Bladesmith"
Do you use a flap disc on the angle grinder?
For forge scale I use a "hard" disc..... a flap wheel generally won't touch forge scale.

I was going to try some white vinegar after the quench and prior to the tempering cycle

The problem I see there is the "prior to the tempering cycle" part. If you're achieving full hardening, there is a great deal of stress in a quenched blade. Generally you want to get a quenched blade into the tempering oven as soon as it's cool enough to handle after the quench. At least do what's called a "snap temper"...... minimum 1 hour soak at 350F. It's not at all uncommon for an untempered blade blade to crack of it's own volition, especially the thinner cross sections.

Vinegar will work.....but even when it removes the "stains", there's still going to be work. :)
 

C Craft

Well-Known Member
Vinegar will work.....but even when it removes the "stains", there's still going to be work. :)

Ed, I agree. I was told by a maker once that that is why they call it knife making, and not knife having! I stood there a second contemplating what he had just said, and busted out laughing. The play he had made on words, was funny but he really trying to say something!! In other words he was saying it is the work of making a knife, is what makes it worth having!!!
 

Kevin R. Cashen

Super Moderator
Yes. I don't get a thick scale after my quench, but I get the burnt oil stain that tskes some work to get back to clean ground metal.

Was wondering if anyone had some secrets to get that off easily or keep it from getting so baked on.

I was going to try some white vinegar after the quench and prior to the tempering cycle

Nick what is your heat treating oil? If you are getting this issue with an actual quench oil it is probably on its way to the graveyard. Quench oils are formulated to avoid this problem. It could be the result of over-heating the blade a bit or, as I mentioned, the oil has degraded and has started staining.
 

Nick Riggi

Well-Known Member
Nick what is your heat treating oil? If you are getting this issue with an actual quench oil it is probably on its way to the graveyard. Quench oils are formulated to avoid this problem. It could be the result of over-heating the blade a bit or, as I mentioned, the oil has degraded and has started staining.
I am currently using Peanut Oil- I know this may not be the best but it has been working so far--the oil is fairly new and clean.

From what I have seen in replies- I think I will start to combine some of the methods shared.
Thanks to all for the help and advice!
 

C Craft

Well-Known Member
Nick, when I first got into this game, my adopted mentor, (I adopted him :rolleyes:) told me two names. He said if you see either of these names, stop and pay strict attention to what they are saying. Kevin Cashen was one of those names. Believe me if Kevin is telling you something about HT, Quench, or anything else he shares, the info is worth listening too!!

Compared to others such as Ed, I feel like a pup in the woods! Ed, was one of the first I meant to jump and offer his help, back when I was first getting started.

There are some good folks on this forum and their advice is usually spot on!! Folks like me, make offers at advice because I know how hard it was to find this advice when I first started. I also remember I had to make some mistakes on my own to figure out,

Oh,................ that is what they were talking about!!:eek::D



I have this feeling the next question you are going to get asked is what kind of steel you are using?? Matching the steel to the process is very important. Different steels have different temps the like to be worked as well different steels have different needs when it comes to quench and HT!

Peanut oil probably is not as good as say Canola oil, and quenches such as Parks are better for other steels. Knowing your steel allows you to look up the parameters at which you can get maximum potential out of that particular steel! This is where mystery steel falls into the mix of information. If you have no sure way of knowing the steel you are using is a given type of steel, then it is just a shot in the dark to get the full potential of that steel.

So I know a bunch of folks are going to say, well I used transmission fluid, peanut oil, canola oil to quench my steel and I got real good results!! Did you how do you know that the steel reached the full potential of the steel possible. OK so enough of beating a dead horse!!
DeadHorse.gif


I will take a step back and let others that know more than I try to get you the answers you need!!!
 

Kevin R. Cashen

Super Moderator
To be honest I stopped concerning myself with what other people quench into, unless they specifically ask me to guide them, when I learned over the years that dead horses aren’t the only things that take a beating when you get too involved and, to continue with the metaphor, that horse could be dead because while you may lead a horse to water…

With that said the only reason I asked about the quenchant is that almost any oil, unless specifically engineered not to, will cook out and leave deposits on hot steel. But if an actual quenching oil starts to do it, it is starting to break down and polymerize to form sludge during the quench and it is sign of the quenchant going bad. So, the reason I really wanted to ask was that the quenchants ability to properly cool the steel will go off on you before it reaches this point. So, these are all good things to know.

Peanut oil is one of the worst I have seen for leaving cooked on, black scale. I am not an organic chemist so I can’t tell you why, but I have not been happy with it anytime I visited another shop that used it.

The mystery steel thing is another battle that I just side step anymore, if some folks have their lives enriched by the added challenges and extra time given to just having fun with the repeated process, who am I to rob them of years more fun. So, generally, if there is a mystery steel thread I simply move on to something I can help people with without guessing or breaking out a deck of Tarot cards to suggest a heat treatment.
 
I will back Kevin, with regard to engineered quench oils going bad and cooking into a sludge. My Houghton Quench K gave me 6 great years of use before I started noticing a black "skin" forming on the blade. It would come off almost like a sheath. I felt that it had to affect cooling and confirmed it with hardness testing. I bought another pail of HQK and as expected, no skin. I keep it in a military cannon projectile tube with a sealed lid in hopes to extend life. The first time I bought this stuff in was $250CND... the last time I paid just over $400CND.... and you know what? I would do it again for another inflated price... that is how much of a difference it made.
 
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