LAB 6 pdf (2)

pdf

School

Ivy Tech Community College, Columbus *

*We aren’t endorsed by this school

Course

346

Subject

Mechanical Engineering

Date

Apr 3, 2024

Type

pdf

Pages

Uploaded by MateDugong7537

MET 346 Lab 6: Annealing Name: ______Jesus Davalos___________________ Lab Section: ______ Date: ______ Day: ______ Time: ______ Assignment: Part 1: Lab Data Using the data from the Annealing Data Table, plot on one piece of graph paper: (5 pts.)  Hardness before annealing vs. Percent cold work  Hardness after annealing vs. Percent cold work for 350°C  Hardness after annealing vs. Percent cold work for 400°C Use the graph plotted from above and sketches of microstructures to answer the following questions: a. At what percent cold work does hardness begin to decrease for the samples annealed at 350°C? At 400°C? The hardness starts to decrease at 18.5% cold work (3 pts) b. Why are the above cold work percentages different for each temperature? What stage of annealing begins at this point? The specimen goes through the annealing phases differently based on the cold work and the temperature. This is the recrystallization stage of annealing (4 pts) c. Is there an indication that hardness of the annealed samples begins to increase at higher cold work percentages? Explain why this might happen. Yes, the higher the cold work percentage, the easier it is for the material to recrystallize.

Part 2: Published Data Data A below is published for 70-30 brass strips all previously cold rolled to 50% cold work and then annealed for 30 minutes at the temperatures shown. DATA A Annealing Temperature, o C as rolled 150 200 250 300 350 450 600 700 Hardness, HK (HRX) 170 176 180 183 176 114 80 44 8 Tensile Strength, ksi 80 81 82 82 76 60 46 44 42 Elongation, % 8 8 8 8 12 28 51 66 70 Grain size, in. Fragmented .02 .03 .06 .12 Data B is a combination of our data and published data for annealed (0% cold work) 70-30 brass strips that were cold worked by rolling to the percentages shown. DATA B Percent Cold Work 0 10 20 30 40 50 60 Hardness, HK (HRX) 5 82 122 144 162 170 180 Tensile Strength, ksi 43 48 53 60 70 80 90 Elongation, % 70 52 35 20 12 8 6 Plot Data A and Data B each on separate pieces of 8½ x 11 graph paper. For “A” plot Properties vs. Temperature; for “B” plot Properties vs. Percent Cold Work.

(5 pts) Use these graphs in answering the following questions. In scoring your answers the emphasis is on why you drew your conclusion rather than the numerical answer. a. Recovery occurs over what temperature range? Explain why you picked that range. (3 pts) Recovery occurs over relatively low temperatures. The range would approximately be from the as rolled temperature to 300 degrees Celsius. During the recovery phase, the tensile strength, hardness, and elongation are all mostly constant. b. Recrystallization: (8 pts) i) As best as you can estimate from your graphs, at what temperature does it begin? Explain how or why you identified that temperature. The recrystallization begins at approximately 300 degrees Celsius. Recrystallization begins at the sharp decrease of hardness, tensile strength, and increase of elongation. ii) Recrystallization ends at about what temperature? Justify the selection of that temperature. Recrystallization ends at approximately 450 degrees Celsius. At this temperature, the grains have started to form and grow but before the sharp increase in size of the grains. iii) How large were the recrystallized grains when they were formed? Why do you say that? The grains were approximately .03 inches which is what the size was at 450 degrees Celsius. d. What is the driving force during the “grain growth” stage of annealing? At what temperature do you think grain growth started? Why do you say that? Grain growth started at 350 degrees, started increasing at 450 degrees, and sharply increasing at 600 degrees. (3 pts) e. Data “A” was obtained using specimens that had 50% cold work before annealing. What would the plot of the “A” Data look like if the amount of cold work prior to annealing had been 60% ? You actually know where the curves will be at room temperature and at the highest temperatures. (How do you know that? Check out Data B and also consider that the highest temperatures give you fully annealed material.) Will the other parts of the curve shift to the right (higher temperature) or to the left (lower temperature)? Sketch your answer in with dotted lines. Explain why you chose your answers.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

The curves would shift left because at a higher cold work percent, the material will recrystallize easier. Since the can recrystallize easier the curves will be shifted to the left at a lower temperature. (5 pts) e. 70-30 brass sheet is to be produced 0.15 inches thick using both methods of manufacture, i.e., “A” and “B,” achieving the following properties: Hardness 114 HK minimum Tensile strength 56 ksi minimum Elongation 20 % minimum (Questions follow on the next page) i) In method A, represented by Data A, the sheet is rolled to size and annealed “back” to the properties required. ii) In method B, represented by Data B, it is to be rolled part way, annealed (back to 0% cold work), and given just the right amount of cold work to get the properties required. iii) For each method, A and B, specify the % cold work , annealing temperature , and annealing time that would be critical to achieving the properties required. (8 pts) A: % cold work = 50% CW Annealing temperature = 350 degrees Celsius Annealing time = 30 min B: % cold work = 25% CW Annealing temperature = N/A Annealing time = N/A

Lab 6 Jesus Friday 1:30 Section 007 Due 3/1/2024

ABSTRACT This experiment investigates the intricate interplay between annealing temperature, annealing time, percent cold work, and mechanical properties in metallurgy. Through systematic experimentation, the temperature range for the three stages of annealing is determined, providing insights into microstructural changes in annealed brass. Additionally, the study addresses questions related to the temperature and cold work required to achieve specific mechanical properties. By elucidating these relationships, this research contributes to optimizing annealing processes in brass manufacturing and advancing our understanding of material behavior in response to thermal and mechanical treatments. INTRODUCTION AND BACKGROUND This lab gave the group a visualization of how the cold work from the previous lab affects the grains of the brass materials. These specimens were cut down and placed into plastic pucks and then sanded down until they were smooth enough for the grains to be seen under a microscope. The information about % cold work and the kinds of things like recrystallization and generally longer grains inside the specimen can be visualized under the microscope. The recrystallization process can be acted upon further, which it was for the specimens of this lab, and the specimens were annealed to varying degrees. Those specifications are seen below in the data. Unfortunately the specimens for the lab group were not smoothed down enough so more clear pictures of the samples were provided. Cold work can be beneficial for increasing hardness in materials without needing to spend large amounts of energy and time into hot work. Although this comes at the expense of a more distorted grain structure which could be seen like said before. EXPERIMENTAL PROCEDURE Before the lab, the specimens from the previous lab were annealed and placed intoblack pucks that could be easily used for the main procedure of the lab. The procedure of the lab was to take one of the pucks and use the sanding machines to grind down and smooth the surface of the pucks. After a long shift of sanding, the pucks with the brass specimens from last week’s lab could be analyzed under the microscope and the grain structure could be seen and interpreted clearly.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

RESULTS AND DISCUSSION CONCLUSION To conclude, the objective of this lab was teaching students about annealing as well as the appearances of crystallizations and grains. Overall the results were somewhat successful but also not as the resulting photos shown during lab were deemed failures however examples of the desired formations were still present. Some things that could be improved upon for this lab would be to increase the number of samples as about three quarters of the class was unable to do anything from the lack of samples, as well as some guidance to correctly annealing as groups were given the samples, shown what to do and then left to their own devices. REFERENCES NA APPENDICES NA