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The Scale of Hardness by Rockwell Scale - Lab Report Example

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This paper explores a report on the use of the Rockwell test to determine the hardness of various materials. The key objectives of this experiment are: to establish the hardness measurements of aluminium, brass, steel, and iron, and to compare and contrast the hardness…
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The Scale of Hardness by Rockwell Scale
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The scale of hardness by Rockwell scale
Hardness refers to a measure of the extent of resistance for a solid matter towards different types of permanent shapes whenever some amount of force is applied to the solid matter. The macroscopic hardness is hardness with intermolecular bonds that are strong. It occurs whenever the character of the solid matter under force appears to be complex. In this respect, there are a variety hardness measurements. These include indentation hardness, scratch hardness, and rebound hardness. Hardness does not depend on elastic stiffness, ductility, strength, strain, plasticity, toughness, viscosity, and viscoelasticity (Anyalebechi 1). In order to understand the hardness of different materials, an experiment was set to investigate the hardness of various materials using the Rockwell Hardness test. The materials that were tested in this experiment include brass, aluminum, steel, and iron. Using the Rockwell scale, the measurements of the hardness of each material were determined. The same process was repeated five times and an average for the measurements determined. The key objectives of this experiment are; to establish the hardness measurements of aluminum, brass, steel, and iron, and to compare and contrast the hardness of aluminum, brass, 1018 steel, and cast iron. Cast iron was found to have a higher hardness value than the other metals.
Rockwell scale involves a scale of hardness that relies on hardness indentation of a material. This test is used to determine the extent of hardness through taking the measurements of the penetration depth of an indenter on a load that is large in comparison to the preload’s penetration. During testing, the hardness indentation is linearly correlated to the tensile strength. These traits are vital because they allow the non-destructive bulk metal testing to occur. This paper explores a report on the use of the Rockwell test to determine the hardness of various materials.
All the data collected in the experiment were recorded in table 1.
Table 1.
Material
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
AVg
Brass
74.2
76.6
64.0
70.3
72.3
71.5
Aluminum
43.5
52.7
51.3
49.7
46.7
48.8
1018 steel
93.6
90.5
93.4
91.7
92.3
92.3
Cast iron
97.9
98.4
97.2
98.5
97.7
97.9

Table 2.
Material
Experimental
Published
% Difference (+/-)
Brass
71.5
69.4
2.1
Aluminum
48.8
40
8.8
1018 steel
92.3
98.7
-6.4
Cast Iron
97.9
100.8
-2.9
Graph: Average hardness values of four metals ordered like in table 1.

Graph 2: average values versus published values of hardness.

The obtained data is consistent with the hardness tester calibrations. The experiment was done by performing the different tests on metals having a hardness that is known. There was a close similarity between the experimental values and the published values of hardness. From the results, it is evidenced that cast iron was the hardest material followed by 1018 steel, brass and lastly aluminum. Aluminium is considered to be relatively durable, soft, lightweight, malleable and ductile metal having an appearance that ranges from silver towards dull gray. Its appearance is dependent on the roughness surface. Aluminium is nonmagnetic and has a low potential for ignition. An aluminum fresh field acts as a good visible light reflector and a delightful reflector of far and medium infrared radiations. Pure aluminum has a yield strength of 7 to 11 MPa whereas its alloy has a yield strength of about 200MPa-600MPa. Studies conducted on the hardness of aluminum found out that aluminum’s hardness is one third that of steel. This research argued out that aluminum was less hard than steel. The hardness of cast iron was close to that of 1018 steel.
On the other hand, the hardness of brass changes according to its treatment and preparation and treatment. The hardness will be high in the presence of cold work like swaging, rolling, and bending. The hardness may reduce whenever the annealation is done at temperatures that are elevated (Zhang 2). The acoustic and malleability characteristics of brass make the metal be extremely useful in musical instruments such as trumpets (Anyalebechi 2). The strips of brass are used in organic pipes as reeds that beat over the shallot. Brass is considered to be a highly malleable component. It has a melting point that is relatively low. It also has a property of flow which makes it relatively easy to be casted. Since the metal is an alloy of copper and zinc, varying the proportion of its components alters the properties of brass giving room for soft and hard brass. It is a component that is not ferromagnetic hence could be separated from a scrap that is ferrous through passing the scrap close to a powerful magnet. The addition of aluminum on brass makes it increase its hardness hence become resistant to corrosion. Aluminium establishes a hard layer (aluminum oxide) that is self-healing, transparent, thin and beneficial on the surface of brass.
Steel is an alloy that is obtained from the combination of iron and other elements like carbon. In this respect, carbon and other elements in steel have a function of hardening the component hence preventing the crystal lattice of the iron atom from dislocating and sliding past another (Dieter 4). The extent of the hardness of steel is controlled by varying the quantities of the alloying elements and their present form inside the steel. Steel that has a high amount of carbon content is harder than iron, but it may have less ductility than iron. In this respect, cast iron is an alloy having a carbon content that is higher than 2.1%. In this experiment, cast iron was found to be harder than the other 1018 steel, aluminum and brass because of its amount of carbon. The quantity of carbon in cast iron made it have a high hardness score on the Rockwell Scale test. This implies that the content of carbon in cast iron was higher than that in 1018 steel.
The experiment established that cast iron had the highest harness score compared to the other metals. All the objectives of the experiment were achieved. Aluminium was found to have a minimum score of hardness compared to the other metals. The experimental values were found to be different to the published values due to the errors during the experiment. Some of the experimental errors came about due to air resistance, the heterogeneous trait of the calibration plate, faultiness of the Rockwell scale, and wrong calculation. The experimental errors due to parallax were minimised by conducting the experiment five times. The other errors could be reduced by conducting the experiment in a room that has vacuum conditions, and ensuring that the testing scale is accurate before beginning the experiment. The merit of using this method in testing hardness is that it has a direct number of Rockwell hardness and a fast time of testing (Zhang 3). Its demerits are that the method has arbitrary scales that are nonrated and specimen influence may support anvil.



Work Cited
Anyalebechi, A. Materials Science, and Engineering. New York: Oxford publishers. 2007. Print.
Dieter, E. Mechanical Metallurgy. New: York: McGraw-Hill. 2008.Print.
Zhang, S. Frankel: Transitions Between Pitting and Intergranular hardness in metals, Electrochimica Act. 2005. pp. 1193-1210.














Appendix.
Table 1.
Material
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
AVg
Brass
74.2
76.6
64.0
70.3
72.3
71.5
Aluminum
43.5
52.7
51.3
49.7
46.7
48.8
1018 steel
93.6
90.5
93.4
91.7
92.3
92.3
Cast iron
97.9
98.4
97.2
98.5
97.7
97.9

Table 2.
Material
Experimental
Published
% Difference (+/-)
Brass
71.5
69.4
2.1
Aluminum
48.8
40
8.8
1018 steel
92.3
98.7
-6.4
Cast Iron
97.9
100.8
-2.9 Read More
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