Jominy End Essay

To determine the hardenability of plain carbon firebrand. Theory Hardenability is the ability of a steel to be hardened and form martensite during quenching. Hardenability indicates the reason of hardness which is obtained from quenching process, and it is very important to the components of machine especially tool steel. One of the methods to determine the hardenability of steels is Jominy End-Quench Test. Hardening usually involves quenching where the steel is heated to austenite microscope stage and fast cooling in the quench medium such as water, oil, salt solution, or air to produce microstructure of martensite.The martensite gives hard and brittle properties of steel. Usually, for heavy steel components, the hardness decreases at the affectionateness of component because the microstructure formed is ferrite and pearlite. While at the surface of the component have higher hardness. The difference of the hardness between the core and surface flock be explained by Continuous C ooling Transformation or CCT diagram of the steel. If the cooling rate of steel does not cross the teddy curve of the diagram, then the hardness on the whole steel can be obtained.CCT diagrams allow prediction of the final microstructure of the steel taking into account the uninterrupted nature of the process during cooling of austenite. Other than that, CCT diagrams take into consideration continuous cooling during quenching the cooling curve assumes a constant cooling rate. As we can see from the diagram, martensite form at the temperature below than 200? C, it mean that the specimen with faster cooling rate will able to form more than martensite and higher hardness. Continuous Cooling Transformation diagram The above diagram show the time-temperature isothermal transformation diagram for the plain carbon steel machine Specimen of plain carbon steel, furnace, Jominy End-Quench Unit, and Vickers Harness Tester. Experimental Procedure (a) Heat the specimen to temperature of 850 C and soak at that temperature for 20 minutes.After that, its remain approximately constant while the distance increase. In our experiment, there are some test errors where we are having small rise in our reading of the hardenability value which speculate decrease continuously. This is due to the uneven surface of the tested specimen or cause by the unbalanced cooling rate throughout the specimen. (b) Gives your opinion on the correlation between cooling rate of specimen and the graph obtained. The cooling rate at the end of the plain carbon steel are more higher compare to the.Thus, in the graph it shows the highest hardness at the early stage and then slowly decreases when approaching to the core of the steel. We also can reckon that, at the end of the steel has the highest hardness which cause by the high content of martensite. However, the content of the martensite and hardness will drop when approaching to the centre of the steel. We can conclude that the cooling rate decre ases from the end-quench to the centre of the steel, resulting in decreasing of the hardness.