Steel Heat & Temper Colors

[Jim Koepke]

Someone on another forum posted this and sent me the original scans.
This is just for interest or curiosity. Hope it comes through OK.

166538

166537

Tried uploading the original files, but they seem to be the original RGB scans and would not work. These files have been converted to smaller size jpegs.

jtk

[Johnny Kleso]

Thanks Jim,
I'll have to add those to my website one day :)

The Straw temper color not so true to what you really are looking for..
I'd like to add the steel must be polished and you really have to look for that faint yellow tint of the steel that you want just before it turns brown then blue to have the best temper for a cutting tool..

[Derek Cohen]

There are some interesting comments from Ron Hock on tempering colours in this article I recently wrote, "Low Tech Blade Heat Treating" ..

http://www.inthewoodshop.com/ShopMadeTools/LowTechHeatTreating.html

Regards from Perth

Derek

[george wilson]

Tempering colors in general are not very reliable because different steels will be at different hardnesses though showing the same colors. It is well for the beginner to stay with one steel for some time like I did. Over time,you will learn what that steel is capable of doing at various tempering colors.

There is NO ideal temper color for all different uses.

What I now have is an electric furnace with pyrometer control of temperature and soak times,plus the use of stainless steel foil wrap for oxygen free hardening of steels like A2,52100,etc.

All this takes money and commitment,but you can do a lot by just using one steel like 01 at first,and learning what it can do when tempered to different colors to increase toughness or hardness as needed. I did that for years.

[Jim Koepke]

Tempering colors in general are not very reliable because different steels will be at different hardnesses though showing the same colors.

...

There is NO ideal temper color for all different uses.



The chart mentions that it is for a particular type of steel. I should have mentioned that. To me it has an implication of different steels in different conditions may vary. (The inexact science of the old geezer watching the heat.)

Sometimes you want hard, sometimes you want malleable, sometime you want something in between.

jtk

[george wilson]

I saw it was for 1095 steel. I have had to heat some steels to 750º to get it to blue.

[Joseph Klosek]

Tempering colors in general are not very reliable because different steels will be at different hardnesses though showing the same colors. It is well for the beginner to stay with one steel for some time like I did. Over time,you will learn what that steel is capable of doing at various tempering colors.

There is NO ideal temper color for all different uses.

What I now have is an electric furnace with pyrometer control of temperature and soak times,plus the use of stainless steel foil wrap for oxygen free hardening of steels like A2,52100,etc.

All this takes money and commitment,but you can do a lot by just using one steel like 01 at first,and learning what it can do when tempered to different colors to increase toughness or hardness as needed. I did that for years.

Were you using a homemade temporary furnace or something more permanent?

J.P.

[Johnny Kleso]

I was talking about 0-1 Tool Steel...
I think most folks will not be heat treating A-2 in a back yard furnace but for A-2 and D-2 Straw is still a fine temper color for a cutter edge for wood just may need a higher temp to get there..

My Back Yard Method:
After heat treating 0-1 and cooling I polish the steel with a belt sander..
I then set the kitchen oven to 350º as mine runs a little hot and place steel up on high racks for about 30-45 mins and check for color.. If still not straw I leave in for another 15mins.. If its still not to color turn up temp 20º and check every 5 mins

Also: I say go for straw color as most back yard jobs do not reach the full hardness of steel sent out to a shop.. In the many places I worked with temp controled ovens we still sent most of the steel out to be hardened...

[Mark Baldwin III]

Would it be more accurate to use the temperature crayons?

[george wilson]

Early on all I had was a Mapp gas torch,and some bricks piled up to make a corner which I could put the end of a plane iron into. I could get a few inches of a 2" plane iron hot enough to harden that way. 2 Mapp gas torches are a lot better for a simple heating setup.

[Johnny Kleso]

Mark,
I think the color is the best way you just have to know what it looks like and how to creep up on it..

Even when in a temp controled industrial oven I always look for the color I want brfore checking it with a diamond hardness tester..

When doing something like a center punch you can use a torch and start by heating the hammered end and get that brown and let the heat run down to the point, once point turns straw colored quench it..

This way your hammered end is softer, it should be a brown-blue color and tip with a hint of the straw color.. This type of hardening is hard to do in a oven..

[george wilson]

In a kitchen oven,evenly heating something like a center punch is nearly impossible. In a proper heat treating oven it heats the steel quite evenly. At least mine does. I have one of those 22" deep knife maker's ovens .

I tried to fire blue a flintlock pistol barrel in a kitchen oven many years ago. I just could not get the thick breech to turn blue at the same time as the thinner muzzle. Kitchen ovens are also apt to be off by 75º. I put in a high temp thermometer from Brownell's gunsmithing supplies while doing the bluing. Usinf a heat treating oven has worked SO much better in every way.

I haven't used temp. CRAYONS,but I used Tempilac,which you paint on. It melts sharply when the temperature is reached. THE TROUBLE WAS,I tend to make nicely finished things. The Tempilac ETCHED the dickens out of the steel just like strong acid when it melted. Then,it was a bear having to polish down HARDENED steel!.

[Stephen Pereira]

This is a great thread..and timely..as I am making a few plane irons myself.

I would love to have a heat treating oven but as George says"all it takes is money". So for the moment I use an oxy acet torch, quench in oil and temper in a toaster oven.

Thanks to Derek for posting Ron Hock's suggestions..especially tempering immediately after quenching.

A question..I've been grinding most of the bevel before heat treating..easier to grind soft 01 steel before hardening. But I don't want the tip too thin as it is difficult to control temperatures with a gas torch. Is this an acceptable method.

Steve

[David Weaver]

A question..I've been grinding most of the bevel before heat treating..easier to grind soft 01 steel before hardening. But I don't want the tip too thin as it is difficult to control temperatures with a gas torch. Is this an acceptable method.

Steve

It's fine. If you start making a lot of irons, especially if they're odd shapes, you'll have to do that.

Just heat the iron from the center toward the tip, heating behind the edge first and then working the heat toward the edge just before quenching.

I would not want to grind a blunt square hard iron unless I had to. It's not difficult, but it takes longer than it needs to and it's not necessary.