Experiment 3 Heat treated tissue of carbon steel §A4.1 Objective of the experiment (1)To study the micro-structure of ca

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Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 1 (271.95 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 2 (170.51 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 3 (314.6 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 4 (281.19 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 5 (309.45 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 6 (372.34 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 7 (263.43 KiB) Viewed 15 times

Experiment 3 Heat Treated Tissue Of Carbon Steel A4 1 Objective Of The Experiment 1 To Study The Micro Structure Of Ca 8 (258.86 KiB) Viewed 15 times

Experiment 3 Heat treated tissue of carbon steel §A4.1 Objective of the experiment (1)To study the micro-structure of carbon steel after different heat treatment. (2)Deeply understanding of the causal relationship between heat treatment and changes in crystalline structure and properties of steel. §A4.2 Heat Treatment Tissue of Carbon Steel 1. Iron-carbon alloy can change its crystal structure in a large range through phase change recrystallization, which is the basic basis for improving the performance of steel through heat treatment process. The list of heat treatment tissues of carbon steel studied in this experiment is as follows: A.8. Because most of heat treatments does not belong to the slow cooling process of obtaining equilibrium tissues, it is sometimes referred to as non-equilibrium tissues. 2. Description of the micro-structure of each heat-treated sample The hypo-eutectoid steel is mainly represented by 45 steel: (1)The normalized structure of 45 is shown in FIG. A. 14 (a), which is a mixture of massive ferrite and slightly pearlite (actually a mixture of sorbite and troostite), and belongs to the product of continuous cooling transformation. After being etched by nitric acid alcohol solution the ferrite is bright white and the silk pearlite is dark. And it is more than annealing tissue. (2) The quenched structure of 45 steel is shown in figure (b), which is a mixture of fine needle-like martensite and a small amount of residual austenite. Because
of fine needle-like martensite and a small amount of residual austenite. Because martensite is very small, it is difficult to identify under microscope. It's dark after being etched by nitric acid alcohol solution. (3) As shown in picture (c), you can find a typical tempered sorbite structure of 45 steel The structure can be obtained by quenching and tempering at high temperature. The higher magnification electron microscope images(d) show that the cementite has gathered into a granular form and the matrix of ferrite has recrystallized from the needle into equiaxed grains. 2.The eutectoid steel is mainly represented by T8 tool steel: (1)The structure after isothermal quenching at 400°C is typical upper bainite tissue and the ferrite appears as black feather. (2)The structure after isothermal quenching at 300°C is typical lower bainite tissue and the ferrite appears as black needle. 3.The hyper-eutectoid steel is mainly represented by T12 tool steel: 17 Figure A.14 Heat treated tissue of carbon steel
Figure A.14 Heat treated tissue of carbon steel (a)normalizing of 45 steel (400 x) Etchant 4% nitric acid alcohol solution (c)thermal refining of 45 steel(400 x) Etchant: 4% nitric acid alcohol solution (b)quenching of 45 steel(400 x) Etchant 4% nitric acid alcohol solution (d)thermal refining of 45 steel(7000 x) Etchant:4% nitric acid alcohol solution
(e)isothermal quenching of T8 steel at 400 C (1300 x) Etchant:4% nitric acid alcohol solution 18 (f)isothermal quenching of T8 steel at 300 C (600x) Etchant:4% nitric acid alcohol solution Figure A.15Heat treated tissue of carbon steel
Figure A.15Heat treated tissue of carbon steel (g)spheroidizing annealing of T12 tool steel(600 x) Etchant:4% nitric acid alcohol solution Number Material 1 2 3 4 45 steel 45 steel 1 Table A.S observe various heat treated samples of non-equilibrium structure 45 steel T8 steel (h)quenching and low tempe- ature tempering of T12 tool steel(500 x) Etchant: 4% nitric acid alcohol solution quenching at 1000°C and low temperature tempering of T12 tool steel(500 x) Etchant 4% nitric acid alcohol solution Heat treatment normalizing quenching quenching+high temperature tempering isothermal transformation at 400°C Tissue characteristics sorbite+ferrite Lath-shaped martensite tempered sorbite upper bainite
Table A.8 observe various heat treated samples of non-equilibrium structure Number Material 1 2 3 4 5 6 7 8 45 steel 45 steel 45 steel T8 steel T8 steel T12 steel T12 steel T12 steel Heat treatment normalizing quenching quenching+high temperature tempering isothermal transformation at 400°C isothermal transformation at 300°C spheroidizing annealing quenching+low temperature tempering high temperature quenching Tissue characteristics sorbite ferrite 10 Lath-shaped martensite tempered sorbite upper bainite lower bainite Granular cementite +ferrite tempered martensite+secondary. cementite+residual austentite Thick needle-shaped tempered martensitetresidual austentite (1)Figure (f) shows the structure of spheroidization annealing of T12 steel. After specific spheroidization annealing, the secondary cementite С which originally
distributed in a network on the grain boundary and the cementite Cp in the pearlite both have accumulated into granular cementite and distributed evenly on the ferrite matrix. (2)Figure (g) shows the structure of T12 steel after the quenching and low temperature tempering. The needle-shaped martensite has been precipitated with e- Fe24C phase and it is easy to be etched. Therefore, the blackish needle-shaped structure is presented. (3)Figure (h) shows the structure of T12 steel after being quenched at over-high temperature (1000°C), it appears thick needle-shaped martensite and a certain amount of residual austenite about 15%-30% After being etched by nitric acid alcohol solution, the latter is bright white and constitutes the back of needle-shaped martensite. $A4.3 Experimental equipment and materials (1)XJB (4X) type metallographic microscope. (2)A set of metallographic samples of 45 steel, T8 steel and T12 steel after heated treatment. $A4.4 Brief description of experiment operation 1.Key points of experiment operation (1)Before the experiment, the contents of the two chapters on the heat treatment of iron-carbon alloy and steel in the text should be reviewed comprehensively, so as to prepare theoretical analysis for the experiment. (2) The other operating points are the same as experiment II. 2. Matters needing attention in the experiment are the same as those in experiment II
$A4.5 The requires of experiment report (1) Write the purpose of this experiment clearly. (2) Draw the micro-structure of each sample carefully Indicate the composition of the tissue, and list the corresponding material sample number, name, carbon content, etchant and magnification. (3) Draw the heat treatment process schematic curve of each heat treated sample. (4) Discuss the experience of this experiment.