Science
EGN 3331L Qatar University Mechanics of Material Heat Treatment Lab Report

EGN 3331L

Qatar University

EGN

Question Description

I’m trying to study for my Engineering course and I need some help to understand this question.

Include in Lab Report

1. Cover Letter

2. Introduction/Problem Statement (in your own words)

3. Test Procedure (in your own words)

4. Test Data

5. Results

6. Conclusion

Unformatted Attachment Preview

ASTM Hardness Conversion Table Appendix I Materials Lab Heat Treatment Mechanics of Materials Lab – Materials Section Experiment #1: Effect of Heat Treatment on the Strength of Steel Objective The purpose of this experiment is to introduce the students to the effect of heat treatment on the mechanical properties of steel. Steel is the most important commercial metal alloy. Of course, "steel" is not a single alloy, but instead is a bewildering array of compositions whose common component is iron. The microstructure of steel is the key to its behavior because the crystal structure, size, carbon content and arrangement of the microconstituents (BCC ferrite, BCT martensite, FCC austenite, orthorhombic cementite, etc.) determine its properties. Relevance of Experimental Design Hardness can be defined as the resistance of a material to scratching, abrasion, or penetration. Any hardness index is a manifestation of the combined effects of several related properties, which may include the yield point, ultimate tensile strength, malleability, work hardening characteristics, wear-resistance properties and so on. Therefore, hardness measurements must be interpreted with caution and full consideration of their attendant limitations. In fact, past methods for determining hardness, like the file hardness test, were not fully reliable because they depended on the skill of the technician performing the test. It was not until 1900 that Dr. Brinell of Sweden proposed a new, reliable method whereby the hardness could be indicated by the resistance to indentation. Nowadays, hardness testing has found extensive industrial applications and is an essential tool in the quality control of metals, alloys, and metal products. The Most commonly used hardness testing methods are the Brinell and the Rockwell hardness test. Report Type Worksheet/Informal with Cover Letter Theoretical Background Steel is the term used to describe a large number of alloys containing two key ingredients: iron and carbon. The most common and least expensive steels contain between 0.05% and 1% C, about 98% Fe and the remainder is made of Mn, Si, and other additions. Steels containing primarily C and a little Mn fall generally within the 10XX designation of the AISI-SAE. The XX correspond to the hundredths of percent carbon in the steel. For instance, 1040 steel contains 0.4% C. Steels of this kind have phase diagrams as the one shown in the Figure 13.1 (1). A 1050 steel heated to 850 °C will be made of the austenite phase which has a face center cubic structure. If this steel is slowly cooled to room temperature, maintaining equilibrium conditions, the austenite decomposes and the microstructure transform into two phases, in accordance with the corresponding phase diagram, ferrite and cementite. Expressed differently, the microstructure will be made of two microconstituents: primary ferrite and pearlite. However, if we consider a 1077 steel, the microstructure at room temperature of slow cooled steel will be made of only one microconstituent: pearlite. Pearlite, the eutectoid microconstituent, is made of alternating plates or lamellae of ferrite and cementite. It is expected that the 1050 steel will have lower strength than the 1077 because of its lower pearlite content. Sometimes, it is desirable to increase steel strength or ductility. Controlling the strength and ductility of steels can be performed through the chemical composition (carbon content) or through the cooling process of steel from the austenitic range. If very fast cooling rates are used in cooling the steel from the austenitic range to room temperature (called quenching), the decomposition of austenite to cementite and ferrite will not take place. Instead, the austenite still decomposes but this time a short range, diffusionless rearrangement takes place at the atomic level, which results in the formation of another phase called martensite. Due to this structure rearrangement, the dislocation motion becomes more difficult thus resulting in an increase in strength and a decrease in ductility. Depending on the cooling rate employed, several other microstructures can be obtained in accordance with the time-temperature curves of the particular steel that is used (1). Martensite is very strong but quite brittle, which is undesirable. But if the quenched material is furthermore heated up briefly (a process called tempering) to some intermediate temperature, the martensite decomposes to a fine dispersion of cementite and ferrite. This tempered martensite will have properties intermediate between those of the untempered martensite and slowly cooled ferrite plus eutectoid, retaining still much of the strength of the plain martensite but not nearly as brittle - a very desirable combination of properties! That is why the martensite is tempered, after quenching, for most practical applications. The exact properties are determined by the tempering temperature. If the quenched material is heated again to the temperature where austenite forms, the martensite microstructure will disappear. If this “re-austenitized” material is cooled down slowly, then the resulting structure will be softer pearlite/ferrite mixture, just as if the martensite had never formed before. These processes can be conducted repeatedly. For example, if the same material is re-heated to austenite and quenched again, the structure will become martensite and the hardness will be high again. In this experiment, hypoeutectoid (meaning XX <77) carbon steel will be heat-treated in different ways. The effect of heat treatment on mechanical properties will be determined by hardness measurements using a Rockwell hardness tester. Instructions Table has been created following these instructions for data collection. 0. Make sure all tools, equipment, and machinery are ready to go. 1. Measure the hardness of the sample in as-received condition (three different spots). This material has been rolled (plastically deformed to its final shape) and contains a large number of dislocations, so its hardness is higher than that of undeformed slow-cooled material. 2. The tubular furnace will be pre-heated to about 960 °C. Record the temperature at the center of the furnace. Tie the metal wire to the steel specimen. Place the steel sample in the center of the furnace. Leave the specimen in the furnace for at least 10 min and observe the color changes in the sample as it heats up. 3. Pull the specimen quickly using attached wire (SPECIMEN IS RED HOT; USE EXTREME CARE PER ASSISTANT INSTRUCTIONS) and allow it to drop in a bucket filled with water. This is a quenching procedure. Remove sample from bucket and clean oxide scale using a file. 4. Measure the hardness of the specimen in three different spots. Set the tube furnace to 970 ℃. 5. Put sample back in furnace; wait 10 minutes. Slide sample away from center of furnace 2 inches every 2 minutes; this results in slow cooling for this experiment. After the sample is completely out of the furnace, cool in water. 6. File off the oxide layer from the surface and measure the hardness at three different spots. Change the furnace to 980 ℃. 7. Place the specimen back in the furnace and keep it in for at least 10 minutes. 8. At the end of the heating period, pull out the specimen and drop it into the water until it cools down. Remove it and file off the oxide layer from the surface of the specimen. 9. Measure the hardness of the quenched specimen on the Rockwell hardness tester at three different spots. 10. Calculate the average hardness for each of the conditions tested. Read and record the estimate tensile strength for each case. State of Steel HR Rockwell Hardness (B or C) Tensile Strength (ksi) Initial State After 1st Quick Cooling After Slow Cooling After 2nd Quick Cooling Cooling Phase 1st Quick Cooling Slow Cooling 2nd Quick Cooling Furnace Temperature (°C) Time of Cooling Phase (sec) Results 1. Organize all your data in a table or tables and compute the average tensile strength for each procedure. 2. Determine and draw the temperature profile for all cooling procedures. The data can be presented on top of the corresponding CCT diagram (Figure 12-17). 3. Determine the expected microstructure for both cooling procedures using appropriate CCT diagram. (e.g. martensite/pearlite/bainite/etc.) 4. Comment on the properties and correlate the properties to the microstructure. (e.g., how is martensite/pearlite/bainite/etc. related to strength? Did the strength change after the process? Does martensite/pearlite/bainite/etc. make the steel more ductile/brittle/etc.?) 5. On the Fe-C phase diagram (Figure 11-12), indicate and specify the point at which austenite starts forming in this particular specimen based on temperature and weight percent of carbon. 6. Compare measured martensite hardness with that expected for the type of steel used. The steel that was used is 1060 Steel. Was it higher/lower than expected (Figure 11-24)? 7. Compare slow-cooled hardness with textbook values for the type of steel used. (Figure 1117). The steel used was 1060 Steel. Explain factors that may result in difference. Research if necessary. 8. Was the second martensite harder/softer/same compared with that obtained the first time? Why? Include in Lab Report 1. Cover Letter 2. Introduction/Problem Statement (in your own words) 3. Test Procedure (in your own words) 4. Test Data 5. Results 6. Conclusion NOTE: TO RECEIVE FULL CREDIT MAKE SURE TO INCLUDE ALL EQUATIONS, IMAGES, FIGURES & TABLES USED. Bibliography 1. D.R. Askeland, “The science and engineering of materials”. PWS-Kent Publishing Company. Boston. USA. 1994. State of Steel HR 43 Initial State 45 45 After 1st Quick Cooling 51 45 50 34 After Slow Cooling 31 42 After 2nd Quick Cooling Cooling Phase 1st Quick Cooling Slow Cooling 2 nd Quick Cooling 52 43 50 960 Minimum Temperautre Furnace Reaches (℃) 889 970 897 365 980 898 2 Set Temperature of Furnace (℃) Time of Cooling Phase (sec) 4 ...
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Final Answer

Attached.

Running Head: STEEL MECHANICAL PROPERTIES

Heat Treatment Lab Report
Steel Mechanical Properties
Name:
Course:
Instructor:
Date:

2

COVER LETTER
The experiment investigates the heat treatment process and its effects on strength of steel
and effects of rate of cooling on the mechanical properties of steel. The experiment objectives
included to introduce the student’s heat treatment process and its adverse effects on the various
mechanical properties of steel and to investigate the effect of the rate of cooling to the strength of
the steel in heat treatment.
Hypoeutectoid carbon steel was heat treated in several ways and the effects of heat
treatment process on the various mechanical properties determined by hardness measurements
using a Rockwell Hardness tester. This was achieved through insertion of a sample specimen into
a tube boiler at a given set temperature, specimen held at that temperature for some time and then
the specimen removed and cooled and the hardness measured using a Rockwell hardness tester.
Various cooling procedures were defined by the various rates of cooling implied onto the
heated specimen. The results of this experiment therefore confirmed the theoretical basis of an
increase in material strength as a result of rapid cooling during heat treatment and an increase in
steel alloy strength as a result of increase in carbon content and vice versa.This experiment is
important because it centralizes on the industrial point of interest, that is developing a material,
specifically the wide used steel alloy, with higher mechanical properties.

INTRODUCTION

3

Steel one of the most important materials, containing less than 2% of carbon and 1% of
manganese and also some small amounts of other elements such as oxygen, phosphorus, silicon
and Sulphur. It has a vast application and can be easily recycled (Administrator, 2006)
The measure of material’s resistance to localized plastic deformation is known as hardness.
According to (Callister, 2007), ancient tests for hardness were solely based on natural minerals
with constructed scale exclusively on the aptitude of a given material to scratch another softer one.
A different...

malsad5343 (174)
UIUC

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