Author Options:

High carbon steal annealing/tempering Answered

First off, I'm not entirely where to post this nor if it has been posted elsewhere (i did do a quick check but i didn't spend too much time on that endeavor). So if this is not the correct/best place to post this i will move it and if it is elsewhere then i will delete it.

This topic starts with a question from something I just recently did. I got a high carbon steel marking knife (its a Hock tool) and when i got it, it was bent and i heated it up to a nice red color, let it cool, tried bending it, and broke the tip off so i sharpened it back to a point and heated it up until it was no longer magnetic and heated it at 450F for about an hour. After doing this and checking some charts I was expecting a golden/brown color but instead got a blue color throughout most of it. So do i need to redo this or is it harder than i would expect from a blue colored steel?

So I'm sure there are plenty of resources out there for figuring all this out but i was hoping this could be a centralized area for anyone to get all the information they need on this topic.
  • what are some tips/tricks on annealing/heat treating/tempering iron, steel, and high carbon steels?
  • is there a difference between the three  (annealing, heat treating, and temper)?
  • what is the difference (if there is one)?
  • what should someone expect from doing something like this?
  • what would each color be useful for (which would be best for a drill bit or which would be best for woodworking tools etc.)?
  • any tricks of the trade?
  • any personal tricks that you wont find anywhere else?
  • anything else to add?
ANYTHING that is relevant would be helpful, im sure there are many people that could benefit from a list of tips from those who actually do these things.

if i remember to do so i will post this blue marking knife that i'm talking about.



4 years ago

http://www.amazon.com/Complete-Modern-Blacksmith-Alexander-Weygers/dp/0898158966 great author. Personally, I trust surface color more than the accuracy of my oven. When I anneal in oven, a baking pan of sand retains heat. Tool buried in sand wont air harden. (Sounds like you air hardened the tip, then broke it) A forge is nice, but propane torch is enough for small projects. There are lists of temper colors for different tools. One example: http://cedarriverforge.com/Photo-index/Blacksmithing/Color%20charts.jpg


Reply 4 years ago

that was one thing that i found strange, i looked at the temperature-color charts and it should have turned out a golden/straw color but ended up being a blue color and now (a few days later) it is more of a black/gray with a blue tint. im not sure how deep this oxide(?) layer is because i haven't done any work to it after the heating and cooling process.


Reply 4 years ago

the oxide colors are very thin. It will readily grind or polish off. Some smiths will harden and temper with 1 heat. After quenching the cherry red, quickly hone the black off, then watch the oxide colors chase, and quench again.


4 years ago

http://www.rakuten.com/prod/pocket-reference-guide-by-thomas-j-glover/247730483.html?listingId=301046642&sclid=pla_google_WholesaleGifts&adid=29963&gclid=CjwKEAjw5pKtBRCqpfPK5qXatWYSJABi5kTxL6XGpf-U1phcDWd8hBBfwlDQ0m6921q_5fkia3wAKhoCFe7w_wcB tons of info in yer back pocket.


4 years ago

I don't really go for color checking, the only time I do this is to color stainless steel that has esthetic purposes.
Not much time anymore for all hobbies but from my knife making days:
Cold forming only on soft steel or when you have to wrok-harden the surface - don't try to cold form, bend tool-, carbon- or other very hard steel varieties.
If forming hard steel then do while the piece is still hot, but never after it cooled down.

I know I am far from being perfect as a blacksmith but it basically comes down to knowing your steel and how to handle it. Takes some experience and then you don't even think about it anymore ;)
About the heat treatment:
Getting a piece to a nice orange glow with no magnetism is the best way to the material into the shape you desire.
All work is done like this until you get to filing, sanding and polishing.
Once you are happy with the result the re-heating to a glowing red followed by the dumping into cold water or oil gives the hardness.
But without further treatment you get a steel that is extremely hard and brittle - it will break easy.
In my case I used to put the hardened steel in the oven at 220-240° C for up to three hours - the heat treatment to get the "give" into the steel.
It is a sience on it's own and people argue about one or two degrees in the temp of the oil / water will affect the outcome, same for using water, normal oil, ice or old (polluted) oil from a diesel engine.
I used old diesel oil to add a bit more carbon into the surface of the steel surface.
Annealing is the process of softening a material through heat treatment, usually this is refered to when it comes to working with copper.
For steel, especially stainless varieties, it can be used to get specific properties or colors into the material but as I said I did not care too much about it.
In most cases on steel it is only used to get certain color into the material.
Be awar that it is very difficult to color steel this way while still getting the full hardness into the material.