PROCEDUREJominy End QuenchMicrostructureDATAJominy End QuenchMicrostructureANALYSIS OF DATADISCUSSION OF EXPERIMENTAL RESULTSJominy End QuenchMicrostructuresLab 2 – End Quenching for Jominy Hardness and MicrostructuresEGR 367 – Manufacturing ProcessesPerformed: 1/18/00Completed: 1/25/00Eric KernTable of ContentsOBJECTIVETo quantify the effects of heating and cooling on the properties of steel. Specifically the hardness and microstructures resulting from the heating and cooling processes.PROCEDUREJominy End QuenchTwo steel specimens, 1045 and 4140 steel bars were heated past 1700degF for several hours to fully Austenitize them. They were then removed and held directly over a 2” stream of water for 10 minutes, after which they were quenched in a bucket of water. This was all done according to the ASTM standards. A flat was ground on the surface so that the Rockwell “C” hardness-testing machine could be used to measure the hardness every 1/16” for the first inch, and every 1/8” thereafter.MicrostructureFour buttons of 1045 steel, and four of 4150 steel were used in this part of the experiment. One of each steel sample was left untreated to use as a control. The other three were heated to Austenitizing temperature and held. Then, one of each steel was quenched with water, one air cooled, and one cooled in the oven. The surfaces were prepared to a mirror finish and the microstructures were analyzed under a specimen microscope. The hardnesses were also measured using the Rockwell “C” hardness tester.DATAJominy End QuenchTable 1, attached in the appendix, contains the data collected for the Jominy end quench hardness test.MicrostructureTable 2, also attached, contains hardness results for the test buttons. Figures 2 through 7 are the illustrations used in the analysis section of this report.ANALYSIS OF DATAFigure 1, attached, is the graph of the Jominy end quench hardness test using Rockwell “C”. DISCUSSION OF EXPERIMENTAL RESULTSJominy End QuenchWhen observing the TTT graphs, it is evident that the rate of cooling makes a significant difference in the microstructure of the material. In turn, the hardness of the material will also be different. Since water will be applied only to the end of the specimen, there should be a hardness gradient up the bar. I think that if the points were graphed, that there will be a rapid change on the end, and it will slope off to asymptotically approach the hardness of an air-cooled part. The 4140 specimen should react identically, but with an overall higher hardness.After observing the results on figure 1, it is evident that this is not the case. The 1045 steel is close to linear, and the 4140 steel is almost opposite of my hypothesis. The hardness actually has a larger delta halfway down the bar. Also, the harness appears to go up slightly for the first inch. There are some obvious erroneous points taken here, and some of the data could be skewed. Overall, this shows that the faster the cooling rate, the higher hardness can be expected.MicrostructuresUsing the TTT curves, we can predict the resulting microstructures from the heat treatments. The water-quenched specimens were probably cooled in a little over 10 seconds, so in addition to Martensite, a small amount of pearlite and/or Bainite has formed. The air-cooled sample probably cooled in about 2 or 3 hours. Here we can expectto see mostly pearlite and some Bainite. In the furnace-annealed sample, it took nearly a full day to cool, and a higher amount of Bainite should be present. The Pearlite should be coarser than the air-cooled piece. I do not know how the specimens were originally made so I do not know what to expect from the untreated samples.For both of the types of steels in the water-quenched samples, there seem to be a lot of smaller details in the sketches. This is proof that the faster the cooling rate, the smaller, and tighter the microstructure. Although you cannot see the Martensite, I believe that I can still observe the very fine pearlite found throughout the specimen. Figure 2 shows this better that figure 3. These both have the highest hardness in they’re category, indicating a higher level of Martensite. Figures 4 and 5 have long, thin details that appearto be pearlite. These are the air-cooled samples. The hardness data for the 1045 steel doesnot seem to be correct. Figures 6 and 7 show the structures of the furnace-annealed samples. These large, somewhat round clumps are probably very coarse Pearlite formations. The untreated samples are unknown in structure, but can be used as a baseline for hardness comparisons.CONCLUSIONIn this lab we were able to make tables and graphs of the hardness of different heat treatments. We were also able to see and compare microstructures. I think that in the future, some actual slides of the microstructures should be used in lab, to compare with what we are seeing in the scopes. Drawing a realistic picture is very difficult and not veryaccurate. Some error in the Jominy end quench portion came from the grinding of the flats on the bars. Even though a surface grinder was used with coolant, you could still seewhere the metal heated up and scorched it, changing the hardness of