School me on Quench Temper

Lanse

Well-known Member
Hey everyone!!

Hope y'all are having a great weekend...

Anyway, I just got a nice torch set on loan to make some videos with...

And there's something I really want to learn more about, practice a little, and then hopefully make a video about...

Back in high school, we learned a little about the Quench and Temper process... Basically, we welded up these chisels from scrap mild steel, then took a rosebud to the tip, got it glowing red hot, and dunked it in water, which we repeated several times...

The steel had a different "ring" to it when struck after the redneck heat treatment, and was much harder... It would actually take a bite out of mild steel instead of just smashing into it...

I still have my chisel...

Anyway, Its something I've only done once, but it fascinated me. I really want to try it again, but I want to understand HOW it works a little better before I make the video, not just how to do it...

Really, if anyone has any good information to share, I'm interested... I've read that some people use oil instead of water... I'd be concerned about the potential fire hazard... And what difference does it make? Maybe the oil doesn't infuse the steel with hydgren which would make it brittle? Thats my best theory...

I also wonder if you can "over-temper" something, ya know, heat it and dunk it too many times, and mess it up somehow...

IDK, just like spark testing and welding cast iron, its something I want to learn more about, and get good at...

Just curious... Thanks in advance... Have an awesome weekend!! :)
 
You need to look up Air hardening steel, water hardening steel and oil hardening steel. All tool steels. I don't think you was testing mild steel in shop class. You can find tempering charts on line. Hot roll steel with surface hard where you torch cut. I buy 2" and 3" thick burnouts that take carbide to clean up the torch marks. After it is clean it is soft. When I take tool steel to heat treat they need to know what steel it is to know how to harden it as well as how hard I need it when done.
 
I posted a link to some basics....some of the fault with using water to quench is that it creates steam bubbles around the piece you are quenching and doesn't cool as quick as is preferred....I usually use water and keep the piece moving quickly while immersed. Metallurgy is quite a vast subject and you should cover some of it in your welding classes. Quenching will harden the work and tempering is an additional process to relieve the brittleness created while hardening. When you temper, you will be watching the colors as they change in the piece you working on. Different colors for different functions of your finished piece. I will look for a color chart and post that link in another post.
link
 
Lanse, heat treating is a subject that could probably fill a pretty good sized book. What you're doing when you heat the metal is altering the grain structure, and when you quench it, you change it yet again, especially at the surface. You really aren't affecting the chemical composition of the steel at all. The different quenching mediums are used (air, oil, water and brine) to control the rate of cooling, with air being slowest and brine being fastest. Id suggest checking with your local community college and seeing if they offer an introduction to metallurgy class. I suspect you'd really enjoy it.
 
Here is a color chart link....when making a chisel I would run the colors until the cutting edge was purple..if tempering a lathe bit, I would run the colors until it was straw colored. Everything will be tempered to a different color, just depends on the hardness desired. The really hard things like a lathe bit will shatter if it is smashed and of course a chisel you don't want to shatter as you are using it. The brittleness goes away with the higher temperatures you temper it at...and as you look at the chart..the further you go past the yellow and towards the blue. One thing I noticed on the last link I posted is that they were not quenching after running the colors..I always quench at that step to stop the running colors. When you run the colors, use minimal heat, as it is easy to go past the color you want!
color chart
 
In high school shop class 50 yrs ago. We made chisels out of tool steel (I think) heated them red/ yellow hot and quenched them in oil , it was 8 figure eights in oil, and remove.
 
The best short education I can give you is as follows.

Hardenable alloys and tool steels are the only type of steels that can be correctly/throughly heat treated.
I would be typing for an hour to explain all there is to know you for just the basics. (and I am not a metallurgist)
There are a dozen or so tool steels each with its own specific use and application.

I highly suggest that you go to a library or search the web to educate yourself in the science and art of metal alloys/tool steels and heat treatment of it.

Have fun.
 
Dick L,

I too, have machined many burn-outs in die sets which were made of hot roll. Sometimes they were soft, sometimes hard. The only logic I could come up with was flame adjustment. Carburizing = hard and oxidizing = soft.

Just one of my many unproven theories......

Maybe Lanse could make a video to prove/disprove my theory ??
 
Some of today's mild steels will harden... guessing it has to do with what was in the recycle pot that day. One trick for hardening is to use a magnet to check temperature. When it doesn't stick anymore quench the piece. Old spring stock and files make good material for homebrew tools.
 
Mild steel(1018 through 1030) will not harden. It has to have enough carbon or alloying element to harden. Springs are normally 1085 steel which is not mild steel.
When remelting scrap they add whatever is needed to make it a particular alloy.
 
Mild steel(1018 through 1030) will not harden by jost quenching. It has to have enough carbon or alloying element to harden. You can case harden any steel.
 
I am going too add my 2 cents here.

I can't tell you what steels will harden but I was taught that different metals like different quench speeds. Oil is slow and brine is fast leaving water in the middle.

We hardened a chisel that we first had to forge out without cracking it by cold forging. (Throw it on the floor, listen for the ring)

Then we heated it until a magnet would not stick to it (1350F?) at which point it was dropped into water. It was extremely hard at this point (was told it could crack) and we ran to the other side of the shop and ground a bright place on the side of the chisel end.

It was then tempered by laying handle first at the edge of the forge to let the heat soak in from that end so that it (the handle end) would be softer. When the bright spot got to a straw color it was quenched again. (I think it was light straw.)

If you do it right it will be hard. I got a good grade but was docked a few points for the length dimension being off slightly. He was a stickler for accuracy.

Yes I think there are quicker ways but this did work.

RT
 
There is a lot of information and help aviable on the I Forge Iron forum. Also it high time for you to look into blacksmithing and forgeing. Using a forge (either gas or coal fired) is a lot cheaper way to heat metal. Also they have information on welding, machineing, and the business side of running a shop. A good place to visit and lots to learn! Armand
 
I don't know much about heat treating cause I was never involved with it. I know you can change the color of steel by heating it to different temperatures in an oven.

I'm more curious about the Hobart school. I was expecting you'd be giving updates on what you were learning and new techniques they've shown you but you've hardly said anything other than that you really enjoy it. I think it would be of great benefit to the users of this forum who want to improve their welding skills.
 
Quenching mild steel doesn't turn it into tool steel. What you did was to case harden the exterior of your homemade chisel, leaving a hard, brittle coating. Proper heat treatment is a complex process, and starts with using a heat-treatable alloy.
 
Lanse,

It sounds like you are ready to look at a "Machinery's Handbook" and a steel catalog: Ryerson, Jorgenson, and Central used to be good steel catalogs. The Carpenter Tool used to specialize in tool steels. Ask your instructor who are the current brands and where you can get/borrow one.

Tool and die makers work with tool steels.
 

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