Heat Treatment of Steel – Lab Report Example
Heat Treatment of Steel Introduction Physical and mechanical properties of metals can be altered without necessarily changing their shape. This is achieved through a process referred to as heat treatment. Heating and cooling of metals during heat treatment is done in a controlled process. This is done to manipulate their properties (physical and mechanical), ensuring that their shape remains unchanged. There are instances where such heating and cooling is done inadvertently, for example in welding. Heat treatment is undertaken to achieve various objectives, the most common being increase material strength or alter specific manufacturability objectives. This experiment examined plain carbon steel 1045, with the objective being to determine the processing-microstructural relationship for the metal.
Determining the processing-microstructural relationship required the use of a material that would respond quite well to heat treatment. Steels are widely used more than other metal materials, both in low scale and commercially. Heat treating steel is done for multiple reasons, among them softening the metal, hardening or modifying the material. In so doing, it is possible to examine processing-microstructural relationship of the metal. This provided for the ability to determine the underlying objective, subject to undertaking heat treatment on plain carbon steel 1045.
Steels depict various properties due to the fact that they are characterized by numerous microstructures. Different types of steel react differently to heat treatment. Their microstructure composition is a critical determinant of this reaction. In the experiment’s context, phase transformation through heat treatment was employed to heat and cool the steel sample in its solid state. It was evident that its microstructure would remain the same after heat treatment. It was therefore expected to change, paving way for the examination of processing-microstructural relationship for the metal material.
Thermal processing in heat treatment was entirely employed. This was the case because the interest was not to change the shape of the metal, but to alter steel’s physical and mechanical properties. The objective of carrying out the experiment relied on the structure of the material as opposed to its shape. The thermal processing employed would have the structure of steel modified, while its shape remained unchanged. Thermomechanical and thermochemical processes are other approaches that fall into the domain of heat treatment (Askeland Ch.12). Thermomechanical processing alters both shape and structure in a material, while surface chemistry and structure of a material can be altered through thermochemical treatment. The structure of the material was the main interest in pursuit of determining the processing-microstructural relationship for the plain carbon steel 1045, and thus the use of thermal processing during the experiment.
The controlled heating and cooling was employed to make it possible to examine the heating rate and cooling rate during the process. The importance of cooling rate was fundamental to observe. This is because cooling rate categorizes heat treatment into two; annealing and quenching. Annealing is associated with a slow rate of cooling, which is either done in air or with a furnace (Callister 207). Quenching on the other hand is associated with a fast rate of cooling. Oil or water is used for quenching. Both annealing and quenching were employed in the experiment and relevant observations made in regard to the experiment objective.
Askeland, D. R., The Science and Engineering of Materials, Boston, MA: PWS Engineering,
1984, Chapters 11 and 13.
Callister, W.D., Materials Science and Engineering, An Introduction, New York, NY: John
Wiley & Sons, 1985, pp. 165-178, 195-218.