First, heat the work piece to dull red heat. A process to case harden that I have used in the past with success is to use “case-hardening powder” Jack Bodenmann describes the process quite well When case hardening you should wear gas welding glasses. With all those little teeth on the quadrant the laser had to cut maybe three teeth, go to another section of the quadrant, and then come back where it left off to avoid overheating and burning off those small teeth in a given area. One part that comes to mind is the throttle lever quadrant. They will require at least a case-hardening treatment before they are applied to the locomotive to make sure that they will wear well during use. Some of the parts that you will make while building a live steam locomotive will be made out of ordinary soft carbon steel. Jim Kreider posted the following Facebook, 1 April 2020: In glass, tempering is performed by heating the glass and then quickly cooling the surface, increasing the toughness. For instance, very hard tools are often tempered at low temperatures, while springs are tempered to much higher temperatures. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Older formulations of these compounds contain potentially toxic cyanide compounds, while the more recent types such as Cherry Red do not. Small items may be case hardened by repeated heating with a torch and quenching in a carbon rich medium, such as the commercial products Kasenit / Casenite or Cherry Red. It is possible to carburize only a portion of a part, either by protecting the rest by a process such as copper plating, or by applying a carburizing medium to only a section of the part. The carburized section will have a carbon content high enough that it can be hardened again through flame or induction hardening. In this process steel is introduced to a carbon rich environment and elevated temperatures for a certain amount of time, and then quenched so that the carbon is locked in the structure one of the simpler procedures is repeatedly to heat a part with an acetylene torch set with a fuel-rich flame and quench it in a carbon-rich fluid such as oil.Ĭarburization is a diffusion-controlled process, so the longer the steel is held in the carbon-rich environment the greater the carbon penetration will be and the higher the carbon content. In such applications, case hardening can provide a part that will not fracture (because of the soft core that can absorb stresses without cracking) but also provides adequate wear resistance on the surface.Ĭarburizing is a process used to case harden steel with a carbon content between 0.1 and 0.3 wt% C. The term face hardening is also used to describe this technique, when discussing modern armour.īecause hardened metal is usually more brittle than softer metal, through-hardening (that is, hardening the metal uniformly throughout the piece) is not always a suitable choice for applications where the metal part is subject to certain kinds of stress. Case hardening is usually done after the part has been formed into its final shape, but can also be done to increase the hardening element content of bars to be used in a pattern welding or similar process. For iron or steel with low carbon content, which has poor to no hardenability of its own, the case hardening process involves infusing additional carbon into the case. Case hardening or surface hardening is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal (called the "case") at the surface.
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