Engr45 California State University Sacramento Spring 2006 Instructor: Homen [email protected] Lab Report: Heat Treatment of Steel The lab report for Heat Treatment of Steel will be a group lab report. This means you should form groups of three to four students (four is preferred) and work collaboratively to complete the report. Your report must be in the following order and include: 1. Title Page. Include: a. Lab title b. Lab report submittal date c. Course title and lab section d. Group member names e. Your lab instructor’s name f. Date experiment performed 2. Abstract. Include in a (one paragraph) statement specifically what was done in this experiment and why, and any important results and/or conclusions. Each student must complete his/her own abstract working individually—this is one of two items that will be completed in this manner. When the final report is submitted, there should be as many abstracts included as there are group members. Be sure to include individuals’ names on these. 3. Introduction. Explain what was done in this experiment. (The introduction does require more detail than the Abstract). Each student must complete his/her own introduction working individually—this is the other of the two items that will be completed in this manner. Describe the different heat treatments you investigated, how they are obtained, and what differences in strength properties you expect. Describe strengthening mechanisms for steel. Pay close attention in class to identify useful concepts to include in the introduction; be sure to include all “buzz words” and items discussed. Try to remember: an introduction focuses on definitions. Include a statement addressing why engineers are interested in this type of experiment (this tends to validate the experiment). 4. Results. In three tables present your property values for 4140 steel as follows: a. Create one Excel table to present results for the steel in each of the conditions tested (as-received from lab 3, annealed as tested in your lab section, as-quenched, and quenched and tempered as tested in your lab section—that’s three total samples, one of which was in two conditions—four different conditions). This table will allow quick comparison of the strengths and properties of steel with different strengthening mechanisms and heat treating procedures. b. Create two Excel tables comparing experimental results of the two differently heat treated (annealed, quench and tempered) samples to literature (industry) values (one table for each sample. Be sure to include the proper citations for the literature values and a percent difference column. In all tables report values of: o o o o o o Elastic modulus Yield strength Tensile strength Hardness % Elongation % Reduction in area For each table, comment on any trends you see as you compare the results. 5. Stress-Strain. Diagrams. Construct a properly labeled Excel plot showing stress-strain curves for the as-received steel, the annealed steel, and the quenched and tempered steel (yes, all three on one plot). Indicate ultimate tensile strengths, yield strengths, and breaking strengths for all three curves making sure that the values of stress and strain are accurate at these points. 6. Discussion. Clearly and completely explain why the following specific points are important and how they relate to what you did in the experiment. Make sure to give specific answers where appropriate. a. The first paragraph of your discussion should be an introductory paragraph explaining in general the strengthening mechanisms studied in labs 3 and 4. Briefly describe the macroscopic results of cold working (lab 3) and each of the heat treatments considered (annealing, austenitizing and quenching, and quench and tempering). b. Are the elastic moduli similar for all three of the steel specimens you tested and analyzed? Is this what you expected? Explain. How do they compare with the elastic modulus you determined for the aluminum specimens you tested in lab 3 (the 2024 aluminum? c. Compare the yield strengths, tensile strengths, and breaking strengths for the asreceived, quenched and tempered, and annealed specimens. Is this what you expected? Explain. Remember the as-received specimen is cold worked—a different strengthening mechanism than austenitizing-quenching-tempering. d. What phases and constituents are present in each of the steel specimens (annealed, asreceived, as-quenched, and quenched and tempered)? Describe each microstructure and explain how these particular microstructures are formed. e. Explain how the microstructures of the differently heat treated and cold worked specimens (annealed, as-received, as-quenched, and quenched and tempered) influence the mechanical properties (strength, hardness, ductility). Why do these properties vary with heat treatment? f. Plot properties of the quenched and tempered 4140 steel (Y.S., T.S., hardness, % R in A, and % El) vs. tempering temperature. Comment on any trends. Explain why this behavior is expected. Using these plots, predict the properties of a quench and tempered sample of 4140 steel tempered for 1 hour at 600F. g. Using the stress-strain curves determine: o The total strain in the quench and tempered sample at the 0.2% offset yield point. o The total strain at the UTS for the as received sample. o In the annealed sample, just prior to fracture, how much of the total strain was plastic and how much was elastic. Clearly explain how you arrived at your answers. h. Starting with a quenched specimen of 4140 steel, how could it be put in the annealed condition and what would its microstructure be after annealing? i. If you were going to create a part that requires machining and is also required to be hard, explain why you would machine it in the annealed state before you did the final quench and temper process for strengthening. j. If you were going to make a steel chisel, what properties would you want it to have? How might you use a heat treatment to achieve those properties? 7. Appendix. Attach any raw data sheets and data plots. The grading for this report will be scaled as follows: Item 1. Title Page 2. Abstract 3. Results a. Three samples comparison Comments/trends b. Annealed vs literature Comments/trends c. Quench & Temp vs lit Comments/trends 4. Stress-strain diagram 5. Discussion, 4 pts ea x 10 questions 6. Appendix Total: Points 4 8 10 4 5 4 5 4 12 40 4 100 points The introduction will count as writing assignment 3.