Heat treatment could be any of several controlled heating operations used to change the physical properties of a metal; There are five different types of heating processes. These would be carburizing, normalizing, quenching and tempering. While they all differ in results, they all share three simple steps: heating, soaking, and cooling. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Warm-up. The first step in a heat treatment process would be heating. The steal is heated to its final temperature. This helps maintain a uniform temperature in the part being heated. This reduces cracks and distortions. Soaking. When a piece of metal is heated to the temperature at which a change in structure occurs, it must remain at that particular temperature until the entire part has been heated uniformly. The greater its mass, the longer it will take for it to be fully submerged, this is known as soaking. Cooling. After the metal part is immersed, the last step is cooling. This process can force the structure to stay the same, return to its original shape, or even change from one chemical composition to another. These changes are all predictable and for this reason metals can now be adapted to certain structures to increase their level of hardness, strength and ductility. Surface hardening. This is the process of hardening the surface of metal objects while the deeper metal underneath remains soft, this will form a thin layer of harder metal called case. For other metals such as iron and steel that have a low carbon content, the process would involve infusing additional carbon into the surface layer. Generally carburizing is done after it has been shaped into its final shape, carbon and alloy steels are suitable for carburizing. Please note: this is just a sample. Get a custom paper from our expert writers now. Get a custom essay Annealing. Annealing is the exact opposite of hardening, it relieves internal tensions, softens them and makes it more ductile. It is the process in which a metal is heated to a very high temperature; it was kept there for a period of time usually ranging from hours to days and allowed to cool. For this process to work perfectly, it is necessary to slow down the process in steels and other ferrous metals. Conditions in the kiln are tightly controlled to ensure that expected changes occur.