Case hardening question

[Mark TyldesleyParticipant @marktyldesley75376]

Hi,

i have some slide bars to case harden,and i will be using Beta no1 case hardening compound, i understand the principle, just i would like it clarified that after heating and covering in powder and reheating, do i quench prior to repeating a second application, or can i apply more powder after second reheat?

thanks

Mark

Edited By Mark Tyldesley on 29/11/2014 15:10:24

[Mark TyldesleyParticipant @marktyldesley75376]

[Brian WoodParticipant @brianwood45127]

Hello Mark,

I am not familiar with the Beta 1 hardening compound you plan to use, but the general principles of case hardening are to introduce additional carbon into the steel to a depth that is governed by the length of time the component is heated in contact with the compound.

Allowing it all to cool naturally still leaves the job soft and those areas which you wish to remain soft can then have the casing layer machined away.

After this, on reheating [with no more compound] to red heat and then quenching in water will leave the carbon rich surfaces glass hard. A softer quench can be into oil and the surfaces will still be hard but maybe 10 Rockwell points softer.

Now the component will need tempering to reduce the brittleness [certainly after water quenching] by careful and gentle re-heating to rapidly quench again into water when the tempering colour is as you want it. Straw is the hardest temper, dark blue the softest. For the hardest result boiling in water for perhaps 1 hour will still improve the resistance to cracking.

What you are doing here is also stress relieving and improving the fracture toughness by trading in some of the hardness imparted by the quench. Oil quenched parts may not need that treatment as the rate of cooling in oil is nowhere near as fierce.

I hope that answers your question.

Brian

[norman valentineParticipant @normanvalentine78682]

When case hardening there is no need to temper the metal as it is only a surface skin that is hard. The metal under the skin remains soft giving the component the toughness that you need.

[Mark TyldesleyParticipant @marktyldesley75376]

Thanks,

so basically once i have re heated after covering in power, i can apply more powder to increase thickness ? If i do this two or three times then quench i should be ok

[JasonBModerator @jasonb]

Yes. Make sure when you quench it that you keep the bar vertical, if you put it in at an angle it may come out like a banana

[ronan walshParticipant @ronanwalsh98054]

Will you tell us how you got on with the beta CH powder ? If it worked out for you or not. I have heard since the 'elf and safety brigade meddled in the ingredients of case hardening powder it isn't so effective.

[Mark TyldesleyParticipant @marktyldesley75376]

Hi ronan

i did a test on a washer last night, after three sessions the washer surface was hard, took a file to it, and was unable to score it, so first results are good, i shall let you know how i get on with theses larger items hopefully today

mark

[Mark TyldesleyParticipant @marktyldesley75376]

Hi

i managed to CH the slideways, first one turned out fine, the second decided to revert to a banana! Very slightly, managed to straighten it and have now began rebuild, a few mods to refit but nothing to serious all due to the milling i had to perform on bars, so hoping it will be back in steam anyday now.

thank you all for your advice ect

mark

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