Lab report
Abstract
The objective of this experiment was to determine the influence of phase transformation on the microstructure and mechanical properties of plain carbon steel type AISI C1045. The testing of metals is necessary to learn what metal is suitable for construction of a specific item by testing how microstructures react during phase transformations. The metal used during the experiments was samples of AISI C1045 Steel also called carbon steel alloy. The samples each underwent tests for Heat Energy (ft-lb) and Hardness (HRC) at five temperatures; 70°F (assumed to be room temperature, 400°F, 700°F, 1000°F and 1200°F. Images were photographed so that a control was compared to the samples at 400°F, 700°F, 1000°F and 1200°F. The experiment determined that Impact Energy generally increased as temperatures increased and HRC generally decreased as temperatures increased. The images showed clearly the microstructure changes caused by the phase transformations of increasing the temperature. Errors were assumed to be due to the lab technicians’ inexperience in the procedures, in other words human error. Environmental error was possible due to changes in the air temperature.
Key words: carbon steel alloy, heat temperature, hardness, heat energy, microstructures, phase transformations)
Introduction
The purpose of this lab was to evaluate the reaction of AISI C1045 steel to high temperatures during phase transformations. AISI is the American Iron and Steel Institute in charge of classifying steel and steel alloys (Steel Works, 2016). Products built with parts constituted from C1045 must be able to withstand phase transformations while still retaining their strength. Carbon Steel is used for producing torsion bars, bolts, axles, crankshafts, light rods and similar items (AISI 1045, 2016, para. 3). Therefore this carbon steel alloy must be able to withstand a range of temperature from 70°F to 1200 1200°F applied in the experiment.
The main objective of the laboratory was to evaluate the impact of temperature on the Heat Energy, Hardness and microstructures created during phase transformations on plain carbon steel.
Theory
Heat treatment of metals is carried out in industry in order to make materials more suitable for mechanical parts by changing the material’s chemical or physical properties (pacmet, 2016). The temperature at which a metal or metal alloy is deformed gives important information towards predicting the “eventual properties” (ME 3244, 2016, p. 25). Heat is a by product of treatment with high temperatures but storage of heat in an alloy is also accomplished (Lab 4, p.26). Heat energy is stored in the alloy by forming microstructures (ME 3244, 2016, p. 25). Hardness is dependent on the rate of cooling from high temperatures (ME 3244, 2016, p 41).
The hardness in the degree the material can resist deformation from an outside stress that causes indentation (ME 3244, 2016, p. 25). Changes in the appearance of alloys after high temperatures followed by quenching can be a sign that decreased ductility or corrosion might occur along with the positive aspect of increasing strength (ME 3244, 2016, p. 24). The microstructures produced in an alloy by high temperatures and cooling provide information for “controlling the mechanical properties” of materials (ME 3244, 2016, p. 41).
Apparatus
The apparatus used in the experiment included furnaces to heat the samples, a Universal testing machine, a micrometer to measure changes in length, the Rockwell hardness test, a Charpy impact-testing machine, a cut-off saw and a mounting press to keep the samples stable when they are measured.
Procedure
The samples were made of AISI C1045, a plain carbon steel alloy and tested for impact and evaluated for microstructure changes. Samples of the C1045 were heat treated at temperatures of 400°F, 700°F, 1000°F and 1200°F for 45 minutes. After 45 minutes quenching in water at room temperature. Room temperature was assumed to be 70°F. Hardness measurements were carried out to determine the resistance to permanent or plastic deformation (ME 3244, 2016, p. 15). The averages of three repetitions of each measurement were used to represent the values in the resulting graphs that were produced.
Presentation and Discussion of Results
The impact energy of two samples showed increased changes as the temperatures increased. The Sample 2 showed no discernible change until the temperature was raised to 700°F, but an increase of 300°F to 1000°F raised the impact energy from 22.5 ft-lb to 254 ft-lb (See table A1). Sample 2 stayed at about the same Impact Energy, 274 lb-ft when the temperature was raised to 1200°F. (See fig. A1) Sample 3 showed a fairly consistent slow rise in impact energy with increase in temperature measured approximately 100 lb-ft at 700°F and 1000°F but then increased by approximately 159 ft-lb with an increased temperature to 1200°F.Sample 1 on the other hand increased to its highest value of impact energy of 160 lb-ft at 700°F/
The hardness with respect to temperature experiment demonstrated the negative effect of increasing temperatures on hardness. Sample 2 measured the highest hardness value at 70°F at 1200°F the hardness was equal to approximately 23.52 (See table A2). Sample 3 showed the highest hardness at 700°F and at 1200°F measured 28.04°F (See fig. A2). The highest hardness value for Sample 1 was measured at 700°F and the lowest hardness value was measured at 1200°F.
Photographs of the microstructure showed that the control group appeared a brownish-gold colour with straight lines (striations) of microstructure at an angle from the top to the left bottom of the sample (See fig. A3). The images from temperatures of 400°F and 700°F are similar in a mottled greyish-while colour (See fig. A4 & A5). Whereas the samples from 1000°F to 1200°F are similar and showing a bluish-white mottled appearance (See fig. A6 & A7).
The appearance of microstructures changes consistently from the control group as the temperatures are increased. The 400°F image shows a combination of striations and mottled appearance; the 700°F image shows a mottled appearance; whereas the 1000°F shows minimal striations with mottled appearance and a few larger possible black appearing indentations. The taken from the 1200°F example shows a mottled appearance in the background with three large black possible indentations and many small black circles.
Conclusions
The experiment used C1046, a plain carbon steel alloy for samples that each underwent tests for Heat Energy (ft-lb) and Hardness (HRC) at five temperatures; 70°F (assumed to be room temperature, 400°F, 700°F, 1000°F and 1200°F. Images were photographed so that a control was compared to samples that had been heat treated at 400°F, 700°F, 1000°F or 1200°F. The experiment determined that Impact Energy generally increased as temperatures increase. The finding about Impact Energy was confirmed by the images. The images showed clearly the microstructure changes caused by the phase transformations of increasing the temperature as described in the results section. Hardness generally decreased as temperatures increased. Human errors were assumed to be due to the lab technicians’ inexperience in the procedures. Environmental error was possible due to changes in the air temperature or furnace temperatures that were not reported.
References
AISI 1045. (n.d.). Metals and Forge Group. http://www.steelforge.com/aisi-104
ME 3244. (2016). Materials Engineering & Laboratory Course. Heat Treatment of Steel. Experiment 8. Materials Laboratory Engineering Manual. University of College of Engineering, Department of Mechanical Engineering. pp. 41-45
Pacmet. (2016). Basic Heat Treatment. Pacific Metallurgy. http://www.pacmet.com/index.php?h=basicheattreat
Steel Works. (2016). History of the American Iron and Steel Institute. AISI. http://www.steel.org/about-aisi/history.aspx
Appendices
Figure A 1 Graph for Average values of heat energy (ft-lb) at five temperatures 7
Figure A 2 Graph of averaged experimental values for hardness 9
Figure A 3 Control 10
Figure A 4 Influence of heat treatment process at 400°F 11
Figure A 5 Influence of heat treatment process at 700°F 12
Figure A 6 Influence of heat treatment process at 1000°F 13
Figure A 7 Influence of heat treatment process at 1200°F 14
Appendix 1
Figure A 7 Influence of heat treatment process at 1200°F
