What’s up guys?!?!?!?! Michael here with Michael Talks Metal. Our video today is number 104 overall and the second in our series on case hardening of steel……. Carburizing. Huh, You would think that adding carbon to the surface of a steel would be called carbonizing but as the title of the video says, it’s carBURizing.
Back to steel basics…. the hardness that a steel can achieve in heat treatment is dependent on the carbon content. Higher carbon … higher hardness.
So if carbon is added to the surface of a low carbon steel, a normal quench and temper heat treatment will result in a higher hardness at the surface and a lower hardness in the core just due to the difference in the carbon content.
The most common method of carburizing involves heating parts in a furnace environment with a controlled carbon level. Steel parts are typically heated to approximately 1700 deg F where the austenitic steel structure readily accepts carbon and diffusion occurs at an acceptable rate.
Simplifying the process…… the carbon content of the case is controlled by the amount of carbon made available to the steel by the furnace atmosphere. The depth of the carbon penetration by the time at heat.
Since this process is performed at temperatures where the steel is austenitic, the final part properties require a quench and temper either as part of the carburizing process or in a separate heat treatment.
Typical process verification is by hardness testing of the case at the surface and/or at a specific depth. Case depth can also be evaluated using samples that are polished and etched to allow visual measurement with a microscope.
Needless to say, this process has a lot of variables to be specified…… steel alloy, desired case hardness and its desired depth. And we also have core hardness and strength properties. All the responsibility of the part design.
So Check The Specs…. right?
This is Michael with Micahel Talks Metal, thanks for watching and don’t forget to visit our website www.michlinmetals.com. If you made it this far and haven’t subscribed, click here. Missed last weeks? Click here. Thanks for watching, this is Michael with Michael Talks Metal, see you next Thursday, 10am. I’m out!