heat treating steel

[Overs Pianos]

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----- Original Message ----- From: "Carl Meyer" <cmpiano@comcast.net>
To: <pianotech@ptg.org>
Sent: Wednesday, January 05, 2005 6:08 PM
Subject: heat treating steel


>Almost any alloy of steel can be checked on the net for the specs 
>for annealing, hardening and tempering.
>
>My question is:  Is there an easy way to guess the approx temp of 
>steel? Cherry red, or what?

There are color charts published in various handbooks which give an 
approximate indication of color due to temperature

>If it says quench with oil, what will happen if you use water?

Oil quenching grades of alloy steel are designed to achieve an 
appropriate level hardness when being quenched from cherry red in 
oil, in which there will be a much less severe rate of cooling 
relative to water quenching. Oil quenching grades of steel are more 
expensive than straight carbon steels, through the addition of other 
alloying elements which improve the hardenability of the alloy. To 
quote from the "Marks Handbook" (fourth edition 1941);

The oil-hardening steels, sometimes called non-deforming steels, have 
sufficient alloy content to be hardened on quenching in oil: 
distortion and cracking is therefore minimised. They usually contain 
up to 1.75 percent Manganese with small percentages of Chromium, 
molybdenum, vanadium, or tungsten and have the same general 
performance characteristics as plain carbon tool steels.

>If it says quench with water, what will happen if you use oil?

Water quenching steels are usually a straight alloy of carbon and 
iron. These alloys will not achieve an appropriate level of hardness 
if they are oil quenched. They require the faster cooling rate of 
water.

>If you didn't heat it quite so hot and quenched it, would it be less 
>hard and not so brittle?

Indeed. But the idea of quenching is to attain maximum hardness, to 
be followed by the annealing process, in which the object is heated 
only to a temperature which allows the grain size to increase until 
the desired balance between hardness and toughness is achieved.

>I wish I knew more about this, but I'm too old to go take a masters 
>degree on it.

Get hold of a good hand book. I have two which were published by the 
former Australian Steel supply Co. Eagle & Globe, "More hints on 
steel".

>The instacoilers sold by Schaff have cracked because they were not tempered.

Possibly.

At 1:38 AM -0700 10/1/05, Dave Nereson wrote:
>
>
>    I had a blacksmith friend who helped me make a custom backcheck 
>bender that actually fit around the bridle wire.  We used "tool 
>steel," whatever that is, heated it up to red hot, I think, to 
>anneal it (make it soft) in order to file, grind and shape the tool 
>to how I wanted it.  Then to temper it, we re-heated it slowly, 
>watching the subtle (VERY subtle) changes in the color of the metal 
>and when it got to straw yellow, we quenched it, in water I think. 
>I forget the sequence of colors and it would take me a while to look 
>it up.

Hi Dave,

A slow cooling process is the usual procedure once the desired 
annealing temperature has been reached. The heating and quenching 
part is quite easy. The harder bit is heating the object to an 
even-annealing-temperature before letting it cool slowly. A electric 
oven is better for the annealing stage than trying to heat the object 
with a naked flame and judging its temperature by eye.

Before annealing by eye, the object should be highly polished and 
heated against a good light source, so that the level of oxidation 
which reveals the annealing temperature can be seen.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron@overspianos.com.au
_______________________
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