1095 steel heat treatment

Carbon steel springs are tempered blue.

Define "small".

The classic way to heat treat objects small enough to burn in the torch flame is to put them on a larger piece of iron. which is heated to the necessary temperature, and is then tipped so the parts fall directly into the waiting oil or water quench bath.

Tempering is much the same, except no abrupt dump into fluid.

Joe Gwinn

I've seen this term. Doesn't mean anything to me. I have a heat treat oven. So far, I know to heat to 1650 and quench in water. No clue on temper.

The part is 0.187 X 0.5 X 4.0 inches

Karl

From Machinery's temper colour temperatures for plain carbon steel, full blue 560F (293C), dark blue 570F (299C). IIRC a usual recommendation is to hold the part at the tempering temperature for 1 hour per inch of thickness.

That can be done with a torch, with care. But it will be easier on a larger hunk of iron.

What they mean by tempering to a color is that after heating to incandescence and quenching, one cleans the black scale off a convenient surface (or all surfaces) down to bare metal, and then reheats the metal while watching the color of light reflected off a clean spot.

At something like 600 to 700 degrees F, the color will be a deep blue. These colors are generated by optical interference in the oxide film grown on the hot steel, and are a measure of the thickness of the oxide film. The steel is not emitting visible light during tempering.

Tempering to straw color can be done in a domestic oven, as this requires only 400 to 500 degrees F.

There is a good writeup in Machinery's Handbook.

Joe Gwinn

The page you mentioned showed tempering temps from 700 to 1300F, quite a range. Take a look at the various tempering temps on these links

What you are looking for is a plot of RC and Kpsi against ductility. Straight from the oil bath is 46 RC and extremely brittle. Temper at

700F will relieve the stresses, not much else. Here's the range you want to look at:

900F 39 RC 176 kpsi 10% elongation (ductility) pretty brittle!

1000F 35 RC 160kpsi 13% elongation 1100F 28 RC 140kpsi 17% elongation (getting softer)

Sounds like you want something right around 1000F

I had a good chart of the oxide colors, it disappeared.Next best

here is the red heat chart

1000F will be the very dark blue but not getting close to glowing red.

Karl Townsend wrote:

"> Does anyone have information for a procedure to treat this for best spring

Karl, Do you need some material? I've got a bit of C1075 that I used to make a few thousand greenhouse clips out of last year. It's .045 (I think) by 1/2" wide.

Got it from Mead Metals. Here is a link to their heat treat chart--at the bottom of the page.

Bill

The ideal temper will depend on the stress and the number of cycles the spring will experience. If the stress is relatively low, less than

90,000 psi, then tempering around 950F would give maximum life. The 700F temper would be appropriate if stresses are higher and shorter life is acceptable.

I don't have any straightforward data on time, but 1/2 to 1 hour for a small part would probably be safe.

Thanks, everybody

I'll heat 1475, quench in oil, temper at 950.

Karl

------------------------------------- Karl,

Did you try this heat treatment as mentioned above? Did it work as intended? How long did you hold the part at 1475 F, quench in oil, and temper at 950 F?

Thanks, Sarah

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I've lost the original question, but in general, you need to read the specs for the metal in question to determine these factors.

Typically -- how long is determined by the thickness, usually specified as "N minutes per inch of thickness". The temper is also held for a time proportional to thickness (to allow the full piece of metal, from outside to center to reach the desired temperature).

And the *temperature* for the tempering is determined in part by the desired final hardness.

If you can get the book from the manufacturer, it will have good information on this.

I've not hardened 1095 -- but most recently hardened D2 (an air hardening steel which still requires a few tricky steps during hardening.

Good Luck, DoN.

As an apprentice boy one of the things we learned was how to make our own tools and particularly for boring bars it was common to find them in the shop, mainly bars made for some particular task that a commercial bar wouldn't handle.

The accepted technique was to forge the bar to shape, rough grind it and then harden and temper. As we had no ovens and did it all in a forge the hardening was by heating to "cherry red" and quenching and then polishing and tempering to a "light straw" color and re-quench.

An accomplished tool maker could harden and temper in a single heat by quenching the cutter portion of the tool and then quickly hit it on the grinder (to see the colors) and let the colors run down the shank

- from the unquenched portion - and when the correct color reached the cutting edge stick it back in the water.

I am certain that we never got as constant result in dong it this way but I will say that it was a common method for making tools for a hundred years or more.

Cheers,

John D. Slocomb (jdslocombatgmail)