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some tests on steel

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Gaziantep university - Kamaran shekha Abdullah

Published in: Engineering
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some tests on steel

  1. 1. i Table of Contents 1 MICROSTRUCTRE OF STEEL.......................................................................................1 1.1 Steel.............................................................................................................................1 1.2 List of some important chemical elements used in structural steels ...........................1 1.3 Steel Types ..................................................................................................................1 2 HEAT TREATMENT OF STEEL.....................................................................................2 2.1 Definition ....................................................................................................................2 2.2 Types of Defects..........................................................................................................2 2.3 How to Strengthen Metals...........................................................................................2 3 HARDENABILITY TEST ................................................................................................3 3.1 Definition of hardenability..........................................................................................3 3.2 How we can determine Hardenability? .......................................................................3 3.3 Factors Affecting the Hardenability of Steel...............................................................3 4 HARDNESS TEST............................................................................................................4 4.1 Definition of Hardness ................................................................................................4 4.2 Purpose of hardness testing.........................................................................................4 4.3 Hardness measuring mechanisms................................................................................4 5 TENSILE TESTING..........................................................................................................5 5.1 Definition of Tensile test.............................................................................................5 5.2 Purpose of Test............................................................................................................5 6 IMPACT TESTING...........................................................................................................6 6.1 Definition of Impact test .............................................................................................6 6.2 Purpose of Impact testing:...........................................................................................6 7 FATIGUE TEST................................................................................................................7
  2. 2. ii 7.1 Difinition of the test ....................................................................................................7 7.2 Factors that affect fatigue life......................................................................................7 8 Creep Testing.....................................................................................................................8 8.1 Definition of the test....................................................................................................8 8.2 The objective of this experiment is .............................................................................8 8.3 Factor affecting the creep............................................................................................8 8.4 Stages of creep ............................................................................................................8 8.4.1 Primary creep.......................................................................................................8 8.4.2 Secondary creep...................................................................................................8 8.4.3 Tertiary creep.......................................................................................................8 List of Figures Figure 1-1 Type Of steel and Percentage of Carbon..................................................................1 Figure 2-1 Optimization of heat treatment.................................................................................2 Figure 3-1 Relationship between critical diameter and hardenability .......................................3 Figure 4-1 Brinell hardness Test................................................................................................4 Figure 4-2 Rock well hardness Test...........................................................................................4 Figure 5-1 A typical stress-strain curve obtained from a tension test........................................5 Figure 5-2 Tensile-test sequence showing different stages in the elongation of the specimen .5 Figure 6-1 Charpy Test equipment ............................................................................................6 Figure 6-2 Stress - Strain Curve of differnt steel type...............................................................6 Figure 7-1 Rotating Bending Test Machine...............................................................................7 Kamaran Shekha Abdullah 06/12/2016
  3. 3. 1 1 MICROSTRUCTRE OF STEEL 1.1 Steel At the point when carbon in little amounts is added to iron, "Steel" is acquired. Since the impact of carbon on mechanical properties of iron is much bigger than other alloying components, 1.2 List of some important chemical elements used in structural steels Carbon (C),Manganese (Mn),Aluminum (Al) ,Chromium (Cr) ,Columbium (Cb) ,Copper (Cu) ,Molybdenum (Mo) ,Nickel (Ni) ,Phosphorus (P) ,Sulfur (S) ,Silicon (Si) ,Vanadium (V) 1.3 Steel Types 1. Carbon Steels 2. Alloy steels 3. High-Strength low- Alloy Steels 4. Tool Steels 5. Maraging Steels 6. Austenitic Manganese Steels 7. Stainless Steels Figure 1-1 Type Of steel and Percentage of Carbon
  4. 4. 2 2 HEAT TREATMENT OF STEEL 2.1 Definition Heat Treating – defined as the controlled heating and cooling of metals for the primary purpose of altering their properties (strength, ductility, hardness, toughness, machinability, etc.it can be done for Strengthening Purposes (converting structure to martensite), or for Softening and Conditioning Purposes (annealing, tempering, etc.) 2.2 Types of Defects • Surface Defects • Point Defects • Line Defects 2.3 How to Strengthen Metals • Finer grain boundaries – can be done by recrystallizing (and cold working) • Increase dislocation density via COLD WORKING (strain hardening) • Add alloying elements to give –SOLID SOLUTION HARDENING • Add alloying elements to give precipitates or dispersed particles – PRECIPITATION HARDENING (aka Heat Treat) Figure 2-1 Optimization of heat treatment
  5. 5. 3 3 HARDENABILITY TEST 3.1 Definition of hardenability Hardenability is the ability of a steel sample to be hardened by rapid cooling (quenching) OR, The capacity of a steel specimen to transform partially or completely from austenite to some percentage of marten site at a given depth when cooled under some given conditions. 3.2 How we can determine Hardenability? 1-Grossman's method 2-Jominy end quench method 3.3 Factors Affecting the Hardenability of Steel 1-Amount of alloying element 2-Carbon content 3-Amount of Boron 4-Austenitic Grain Size Figure 3-1 Relationship between critical diameter and hardenability
  6. 6. 4 4 HARDNESS TEST 4.1 Definition of Hardness Hardness is a resistance of metal to plastic deformation, usually by indentation. Or define the hardness as the resistance of a material to indentation. 4.2 Purpose of hardness testing The principal purpose of hardness test is to determine the suitability of a material for a given application 4.3 Hardness measuring mechanisms 1- Static indentation tests 2- Brinell hardness testing 3- Rockwell hardness testing Figure 4-1 Brinell hardness Test Figure 4-2 Rock well hardness Test
  7. 7. 5 5 TENSILE TESTING 5.1 Definition of Tensile test Tensile testing it is used In order to discover the various properties of a material we must carry out material tests. There are many different types of tests available but the most common is the tensile test 5.2 Purpose of Test To evaluate the values of ultimate tensile strength, yield strength, % elongation, fracture strain and Young's Modulus of the selected metals when subjected to uniaxial tensile loading. Figure 5-1 A typical stress-strain curve obtained from a tension test Figure 5-2 Tensile-test sequence showing different stages in the elongation of the specimen
  8. 8. 6 6 IMPACT TESTING 6.1 Definition of Impact test Impact testing is used to measure impact behavior and likelihood of brittle fracture. Developed in response to onset of brittle failure in ductile materials e.g. steel ships, bridges etc. Still used in quality control and Standards 6.2 Purpose of Impact testing: 1- Checking quality 2-Tendency for brittle failure 3-Temprature dependence. Figure 6-1 Charpy Test equipment Figure 6-2 Stress - Strain Curve of differnt steel type
  9. 9. 7 7 FATIGUE TEST 7.1 Difinition of the test Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit, or the yield stress limit. 7.2 Factors that affect fatigue life 1-Magnitude of stress 2-Quality of the surface Figure 7-1 Rotating Bending Test Machine
  10. 10. 8 8 Creep Testing 8.1 Definition of the test Creep is defined as time-dependent plastic deformation (elongation) of the metal at a constant tensile load. It is also defined as high temperature progressive deformation at constant stress. 8.2 The objective of this experiment is 1-To understand the stage that is involved in the creep test. 2-To obtain the creep curve. 3-To identify the properties of material while subjected to a tensile load. 4-To measure the rate of deformation of the material to stress at a constant temperature. 8.3 Factor affecting the creep 1-Load, 2-grain size , 3- strain hardening , 4- heat treatments , 5-alloying element , 6-manufacturing processes, 7- thermal stability, 8-composition 8.4 Stages of creep 8.4.1 Primary creep This stage occurs at the beginning of the tests, and creep is mostly transiently, not at a steady rate. Resistance to creep increases until stage 2 is reached. 8.4.2 Secondary creep The rate of creep becomes roughly steady. This stage is often referred to as steady state creep. 8.4.3 Tertiary creep The creep rate begins to accelerate as the cross sectional area of the specimen decreases due to necking or internal voiding decreases the effective area of the specimen.
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