Surface TextureJason ScholtenEric KernTable of ContentsTopic PagePart AObjective 1Part BDiscussion of ResultsSurface TextureJason ScholtenEric KernDate Completed: 1/25/00Date Reported: 2/1/00Table of ContentsTopic PagePart AObjective 1Procedure 1Data, Print-outs, Observations Gathered 1Discussion of Experimental Results 2Overall Conclusions 3Part BProcedure 3Data, Print-outs, Observations Gathered 3Discussion of Experimental Results 4Overall Conclusions 5Objective: To investigate the relationship of the cutting variables and surface roughnessProcedure: - Choose 3 factors on the mill to perform a 23 factorial DOE (speed, feed, & depth of cut).- Calculate speed of automatic feed rate using ruler and stop watch.- Choose a high and a low for each of the three factors above.- Perform 23 cuts on an alluminum block (one for each combination of the three factors) with a ¼” cutter.- Measure the surface texture using a Profilometer.- Record the Ra and Rz values from the Profilometer for each of the 8 cuts.Data: (See attached spread sheet and graph in appendix)Discussion of Results When the steel was heated up to 1700-F, all the microstructures in the steel will become evenly distributed. This turns the metal into Austenite which basically erases the history of the part’s previous heat treatments. From this Austenite, several different structures can be formed depending mostly on how quickly the material is cooled.The bottom of the bar (as it sat in the cooling apparatus) cooled thequickest. This means it is expected that this end of the bar will most likely be Martensite according to the TTT diagram. Points farther up the bar were cooled slower and slower as the points get farther from the water quenched end. Therefore, these points follow a different path on the TTT diagram. Since the top of the bar was cooled the slowest, it would most likely have some pearlite and bainite present. Martensite is a very hard microstructure and therefore, the end of the bar with Martensite present is going to have the highest reading on thehardness scale and this is shown on the attached graph for both steels. The graph shows the hardness to be fairly consistent up to a point 1.0 in. from the end of the bar for the 4140 steel. Therefore, this much of the bar probably cooled off fast enough to form all Martensite. The graph also shows that as the points move from the quenched end of the bar, the hardness drops. This is because the microstructures here are softer than Martensite.The 4140 seems to have an overall higher value of hardness than the 1045 steel. This is probably because it has a higher concentration of carbon. Also, the two materials seem to follow the same trend of having softer microstructures in the areas that are cooled slower.Overall Conclusions:From these results it can be concluded that 4140 is a harder steel and thatdifferent types of steels seem to have the same response to specific heat treatments.PART B:Procedure:- Expose several samples (5) of two different metals (1045 & 4150) to different quenching rates from 1700-F (water cooled, air cooled, furnace annealed)- Polish one end of the sample to a mirror finish by stepping through five increasingly finer grit wet sand paper machines and two polishing wheels.- Pour a drop of acid on the mirror surface to etch it and rinse with water.- Look at etched area through microscope and sketch the microstructure.Data: (See attached sketches of microstructures in the appendix)Discussion of Results:It is expected that overall the 4150 steel will be harder than the 1045 because it has a higher content of carbon. The water cooled buttonstook about 10 sec. to cool which means it is expected to have Martensite microstructure. This is because there was not enough time for other microstructures to begin forming. It is also expected that it will have thehighest hardness value because of its Martensite microstructure. The air cooled samples took about 30 min. to cool. According to the TTT diagram,this cooling path would result in some pearlite and some Martensite. The furnace annealed samples took the longest time to cool (about 1 day) and are expected to result in pearlite with larger grains of ferrite than the air cooled samples.The water cooled sample of 4150 seems to show some random patterns of light and dark which is characteristic of Martensite. The water quenched 1045 seems to have some larger sections of darker areas that could be some retained Austenite from cooling so fast.The next fastest cooled samples were the air cooled samples. Air cooled could result in some pearlite which has ridges of dark and light areas (ferrite and cementite). The 4150 seems to have some lighter areasthat could possibly be the ferrite. The 1045 has some long narrow sections that could be the pearlite microstructure.The furnace annealed samples seem to have some large sections of white. This could be the ferrite which is expected in slower cooling rates.The untreated samples seem to have random shades of light and dark areas. Since these were not heat treated, it is not possible to tell from the TTT diagram which cooling path they follow and therefore what microstructures are expected. Also, overall the 4150 samples were hardersteels than the 1045 samples.Overall Conclusion:This experiment showed the effects of cooling rates on the properties of two different materials.The samples that were cooled rapidly ended up being harder materials. This is benificial when a harder steel is needed. The cooling rate must happen quick enough to not allow any microstructures other than Martensite to formE.C. The samples that cooled the slowest had the largest areas of dark and light shades in their microstructure. The larger areas of light shade were probably ferrite. These microstructures with larger areas seemed to be softer when measured on the Rockwell C hardness test. Therefore, microstructures with larger light and dark shades will probably be softer microstructures, thus, softer metals. This is how the hardness is related tothe