How do I harden a steel bush?
Answer:
1) Clean the bush with a wire brush until the steel is shiny.
2) Heat the bush until 'Cherry Red'.
3) Quench (cool) the bush in oil or water.
4) Clean the bush again.
You will probably need to temper it as it will be quite brittle after hardening.
5a) For a small bush - Place the bush on a scrap piece of plate.
5b) Heat the bush (or plate) until it turn blue. This may not take long.
6) Quench the bush again in oil or water.
7) Clean the bush again.
You will probably need to machine the bore of the bush as the heating will alter its diameter.
make everything in the entire universe except the brush softer
Vacuum heat-treat...expensive, but it works.
slap it around regularly and take it down the gym
What sort of steel?
Normally just heating with gas torch or in oven followed by oil quench should do the trick, but does depend on how hard you require the bush to be.
You may well have to carburise it or even nitride it to get it to full hardness. May be better to purchase pre hardened bush...
Harden carbon steel by heating to red heat then quenching in water. You will have to be very quick with a brush as the thin wires will cool very quickly in air and you must quench them while red hot.
This will make carbon steel very hard but brittle so you may need to temper it by heating again, this time to a critical temperature and quenching again. The critical temp can be gauged from the colour something between "light straw and blue". This will be very difficult with a brush as you will not be able to apply the heat evenly.
Nighthawk has basically got it right- heat until red hot and quench in oil or water, but why would he want to harden a brush?
Not all steel will harden easily. You have to use carbon steel or similar otherwise you will need to quench in a hardening compound , maybe more than once. Harden carbon steel by heating to red hot then quenching in oil. You will need to let the hardness down a bit by tempering. To do this clean the bush back to shining metal then place on to a larger piece of scrap metal. Heat the metal until the bush turns a light straw colour then quench again in the oil.
It is usual to have metals of a different hardness if you are going to use it as a running bearing. Hard running in soft is the usual way. Car crankshaft bearings in the engine block are a soft aluminium type of metal. If the bush is for a drilling jig then hardened steel will be fine. You can soften the bearing down again by heating to red hot, maybe on the scrap plate, then allowing to cool very very slowly without quenching.
Don't forget that metal distorts in hardening so may need further treatment afterwards if you are working to tight limits
There are firms out there that specialise in hardening but a small bush would not be worth while. You could try calling into any local toolmakers and asking a favour for a bottle of wine. Who knows.
Steel is hardened by a heating process.
However, "high Carbon" steels can be heated to harden them (like induction hardening, which is done with a heating coil). "Low carbon" steels cannot be hardened until carbon is added, normally done by heating the component in a carbon-rich environment.
I see your problem is that you have steel bush, and you want to harden it.
Unfortunately the hardening process involves heating, and heating the component causes distortion in the component. Hence the bush will no longer be the same dimensions as before hardening, and worse, it will no longer be truly round. Also, the hardening process will leave the bush surface rough and scaly. Therefore you would have to grind the bush after hardening to achieve desired dimensions and surface finish. In order to have spare material to grind off, your "soft" bush must be made so that the I.D. is more than finished requirements, and the bore is less than finished requirements. This is the "grinding allowance".
The manufacturing operations are therefore 1) sawing the bar to length; 2) Turning inside diameter and outside diameter to dimension which allows "grinding allowance", turning ends square and to length; 3) hardening process (not expensive if you have used a high-carbon steel; 4) grinding of bore and outside diameter to finished size.
I don't know what you're trying to do, but it would be very expensive to make one hardened steel bush, either use a standard hardened bush from a transmission components supplier, or use another bearing arrangement.
If it is ordinary mild steel it will not harden very well but if it is Carbon steel. You should start by cleaning it up, heating until it is red hot then quench in oil or if you dont have any water will do. You will need to put it under the surface as fast as you can because if you leave it half in half out it can affect the levels of hardness. You should then procede to temper the material to regain some flexibility. Do this by cleaning the materal again and heating you should watch it change colour as another poster said. I'm afraid i cannot remember what colour means what as it is years since i have done this. When you get the colour you want quench it again. There is also a process called annealing where you heat the material up and leave it to cool down its self. This will restore the metal back to or as close as it can be to its original hardness level.
Depends on the amount of carbon in the steel. Heat until 'Cherry Red' if its a high carbon steel (it will progress through various stages of yellows / blues and purples and red until its there) and drop it into cold water. If its not a carbon steel it needs to be sealed into a carbon filled container for several hours at around 1300 degrees C to absorb the carbon or heated to the same and dipped in cyanide to give the outer skin a hard layer.
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: