Investigating the effects of heat treatment on metals Essay Example for Free

Investigating the effects of heat treatment on metals Essay Metals have various uses in a wide range of industry, where the properties of each metal determine what the metal will be used for. When a metal properties need to be changed to satisfy particular needs, it can be modified by processing the metals with treatments such as cold working and heat treatments. Structure of metals Metals are made from their ore, at extremely high temperature. In this form, metals are in a liquid form. The liquid metals are cast by pouring it into moulds where it is cools down and solidifies. When metals are frozen, crystals start forming. These crystals begin to form throughout the metal, where they keep they keep rapidly growing until they reach a neighboring growing crystal structure. These crystals are called grains, where crystals that meet with one another are called grain boundary. Dislocation Dislocation are formed when defects are found in the crystal structures. This is often caused by when atoms are missing in a layer, This is shown in figure one. Secondly, the metal trip should be placed on top of the hottest part of bunsen burner. The metal should be kept there until is is seen glowing red. Once the metal has gone red, it should immediately be plunged into the previously filled beaker in step 1. Lastly swirl the beaker vigorously for thirty seconds. Tempering With any metal strip that has been quenched, place the strip unto a bunsen flamer until the metal strip goes a dull red. Once the metal has gone dull red, slowly remove the metal from the bunsen flame and pace on a heat proof mat, where it should be left to cool to room temperature. Annealing Firstly, heat metal strip for five minutes on the hottest part of bunsen flame. the whole length should of the strip metal should be heated. Next, half close the bunsen flame and continue heating the metal on the non luminous flame. When a minute or two has passed, starting moving the metal strip in and out of the flame, top start cooling down the metal. After a couple of minutes, remove the strip from the flame and place it on a heat proof mat, where it can cool to room temperature. Cold working Once the metal has been cooled down, a marker should be made 30mm from the tip of the metal suing a felt tip pen. The shorter end of the metal strip should then be put in between two wooden blocks(the marker line should still be visible). The wooden blocks should be clamped firmly on the table or bench to keep the two blocks in place. With leather gloves, bend the metal strip through 90 degrees where the strip is lying alongside the wooden block ( shown in picture B). The metal should be bending where the marker was made. Now the metal should be bent 180 degrees from its position, this is shown in picture C. This in total counts as two bends. To conclude, the strongest metal in the cold working was steel where it snapped after 44 bends. This changed when the metals where quenched, copper showed the most significant change, where the metal bent 64 times before snapping; indicating an increase in strength of copper. Significant changes was also present in aluminum. Quenching on the other hand had very little affect on steel, as the data shows that steel bent 43, slight decrease compared to cold working where the steel bent on average 44 times. Overall the most affected by quenching was copper, followed closely by aluminum, with the lowest being aluminum which has broke on average after 42 bends. In annealing, copper by far was the strongest metal where the average number of bends was 75. Aluminum and steel however, only bent 32 and 35 times, respectively. This shows that annealing heat treatment does little in increasing the strength of steel and aluminum. The heat treatment tempering, managed to increase the strength of copper and aluminum by a large margin, compared to the other two treatments. This indicates that tempering may be the best heat treatment due to it making copper bend on average 84 times and aluminum 64 times, which are the highest average for both metals. The strength of steel on the other hand decreased under tempering. Generally, aluminum showed the most changes on all three treatment, with tempering having the most effect. Copper strength also increased under all heat treatment, with it also showing the most significant change under tempering. Steel however, was either unaffected or decreased under all heat treatments, this may due to experimental errors Evaluation The procedure for each metal on the table above was repeated three times, to ensure that the experiment was reliable. New strips of metals were used for each new treatment to ensure that the accuracy of the results is not changed. In addition, the length was each metal was made the same, to make the results valid. The metals also needs to be bent as close to the strip as possible, as bending the strips to far may cause the metal to bend quicker, affecting the accuracy of the results.