Physical Metallurgy and Heat Treatment of Steel

ISBN-13: 9783031057014 / Angielski / Twarda / 2022

José Ignacio Verdeja González;Daniel Fernández-González; Luis Felipe Verdeja González

Opis

This book covers the physical metallurgy of steels as well as the heat treatments used to improve the their properties. A full chapter is dedicated to the atmospheres in the steelmaking, including the implications of the own gases generated in the iron and steelmaking factories and how they could be applied in these treatments. This book is specially conceived for graduate and undergraduate courses, being the result of more than 30 years of teaching experience in courses for undergraduate, graduate (master and Ph. D.), and companies (technicians). The trends in the re-utilization of industrial gases in the iron and steelmaking process are discussed by the authors. Additionally, the book comprises 41 solved exercises, problems and case-studies, as a complement of the theoretical sections of the text. These exercises, problems, and case-studies are based on problems observed in the industrial practice.

Spis treści

1. Solid-state transformations in the iron carbon system.

1.1. Introduction.

1.2. Crystalline structures of the iron.

1.3. Solid solutions in the iron.

1.3.1. Substitutional solid solutions.

1.3.2. Interstitial solid solutions.

1.3.2.1. Austenite.

1.3.2.2. Ferrite.

1.3.3. Hardness.

1.3.3.1. Brinell hardness.

1.3.3.2. Vickers hardness.

1.3.3.3. Rockwell hardness.

1.3.4. Tensile test.

1.3.5. Toughness.

1.4. Alphagenous and gammagenous character of the elements solubilized in the iron.

1.5. The metastable Fe-C equilibrium diagram.

1.5.1. 2.11% C steels.

1.5.2. Transformations by equilibrium cooling of hypoeutectoid steels (<0.77% C).

1.6. Influence of alloying elements in the Fe-C metastable diagram.

1.7. Non-equilibrium transformations by isothermal cooling of the austenite.

1.7.1. Metallography and kinetics of the pearlitic transformations.

1.7.2. Bainitic transformations.

1.7.2.1. Upper bainite.

1.7.2.2. Lower bainite.

1.7.3. TTT curves (Transformation-Temperature-Time curves).

1.7.3.1. Intrinsic factors.

1.7.3.2. Extrinsic factors.

1.8. Transformation of the austenite into martensite.

1.8.1. Crystalline structure and hardness of the martensite.

1.8.2 Ms temperature.

1.8.3. Thermal difference (θγ – T) and residual austenite.

1.8.4. Stabilization of the austenite by interruption in the cooling at T<Ms.

1.9. Complementary considerations about the ferritic-pearlitic transformations.

1.9.1. Ferritic-pearlitic transformations of the austenite by continuous cooling.

1.9.2. Ferritic-pearlitic transformations in low alloy steels.

1.10. Designation and normalization of steels.

1.10.1. Different methods to designate steels.

1.10.1.1. Due to the chemical composition.

1.10.1.2. Other designations.

1.10.2. International standards for steels.

1.11. References.

2. Heat treatment of steels.

2.1. Introduction.

2.2. Austenitization.

2.2.1. Heating to austenitize.

2.2.1.1. Overheating and burning.

2.2.1.2. Dimensional variations during the heating.

2.2.2. Cooling from the austenitic state.

2.2.2.1. Heat-transfer factor of the coolant agent.

2.2.2.2. Size factor.

2.3. Annealing to soft the steel.

2.3.1. Full annealing.

2.3.2. Intercritical annealing.

2.3.3. Isothermal annealing.

2.3.4. Subcritical annealing.

2.4. Normalizing.

2.5. Quenching.

2.5.1. Hardenability.

2.5.1.1. Jominy’s curves.

2.5.1.2. Real and ideal critical diameters.

2.5.2. Susceptibility to cracking due to quenching.

2.5.3. Surface quenching.

2.6. Tempering.

2.6.1. General questions.

2.6.1.1. Changes in the martensite during the heating.

2.6.1.2. Evolution of the bainite and pearlite.

2.6.1.3. Colors of the tempering.

2.6.2. Stages of the martensite tempering.

2.6.2.1. Transformation of the tetragonal martensite.

2.6.2.2. Transformation of the residual austenite.

2.6.2.3. Brittleness during the tempering.

2.6.2.4. Recovery-recrystallization of the ferrite and spheroidiza-tion of the cementite.

2.6.2.5. Secondary hardening.

2.6.3. T1 temperature and time t in the tempering.

2.6.3.1. Hardness after 1 hour of tempering at temperature T1.

2.6.3.2. Equivalence temperature-time in the tempering.

2.6.3.3. Potential hardness and softening coefficient.

2.6.4. Multiple tempering treatments.

2.7. Isothermal treatments.

2.7.1. Patenting.

2.7.2. Austempering.

2.7.3. Martempering.

2.7.4. Sub-zero treatments.

2.8. Surface thermochemical treatments.

2.9. Hyperquenching and aging.

2.10. References.

3. Thermomechanical treatments of steels.

3.1. Recrystallization.

3.2. Hot deformation.

3.3. Improvements by hot forming of the solidification structures.

3.3.1. Forge fibering and crystalline texture. Anisotropy of properties.

3.3.1.1. Anisotropy and embrittlement by hydrogen.

3.4. Thermomechanical treatments of the austenite before their allotropic transformation.

3.4.1. Banded structure.

3.4.1.1. Origin of the banded structure.

3.4.1.2. Factors to remove or mask the banded structure.

3.4.2. Controlled rolling.

3.4.3. LT ausforming.

3.5. Thermomechanical treatments of the austenite during its allotropic trans-formation.

3.5.1. Isoforming.

3.5.2. TRIP effect.

3.6. Thermomechanical treatments after the transformation of the austenite.

3.6.1. Pearlite forming.

3.6.2. Martensite forming.

3.7. References.

4. Controlled atmospheres for heat treatments in furnaces.

4.1. Introduction

4.2. Formation and dissociation of metallic oxides. Ellingham’s diagram.

4.3. Reduction of oxides with gases.

4.3.1. Reduction of an oxide MxOy in presence of a CO-CO2 gaseous mix-ture.

4.3.2. Reduction of an oxide MxOy with H2.

4.3.3. Reductant or oxidizing aptitude of CO-CO2-H2-H2Ovapor gases mix-ture in equilibrium.

4.4. Case-hardening and decarburizing of steels

4.4.1. Boudouard equilibrium

4.4.2. Decarburizing-case hardening in a CO-CO2 binary atmosphere

4.4.3. Decarburizing-case hardening in a binary atmosphere of H2-CH4.

4.4.4. Mixture of gases CO-CO2-H2-CH4-H2O in equilibrium.

4.5. Industrial atmospheres. C-H-O-N system.

4.5.1. Introduction

4.5.2. Endothermic and exothermic atmospheres.

4.5.3. Atmospheres obtained from NH3.

4.5.3.1. Nickel as catalyzer of endothermic atmosphere.

4.5.4. The future of the industrial atmospheres.

4.6. Complementary considerations.

4.7. References.

O autorze

José Ignacio Verdeja González received his Bachelor of Engineering from the School of Mines (Polytechnic University of Madrid, Spain) in 1968. He received his Master of Science both in Metallurgy and Physics of the Solid State in 1971/72 from the University of Paris. He obtained his Ph.D. both from the University of Oviedo (1974) and the University of Paris (1978). He was appointed Assistant Professor (1978) and Professor of Physical Metallurgy (1983) in the Oviedo School of Mines (Oviedo, Asturias, Spain). He became the first Head of the Department of Materials Science and Metallurgy at the University of Oviedo (1987-1991) on behalf of Professor José Antonio Pero-Sanz Elorz (1934-2012), and he worked closely with him in academic and industrial problems throughout his professional career (1974-2012). The focus of his current activities is the broadening and strengthening of the academic programs in the Department of Materials Science and Metallurgical Engineering at the University of Oviedo.

 

Daniel Fernández González received the Bachelor of Engineering and the Master in Mining Engineering (Oviedo School of Mines, University of Oviedo, Oviedo, Asturias, Spain) in 2013 and the Master in Materials Science and Technology from the University of Oviedo in 2014. He obtained his Ph.D. from the University of Oviedo (granted by the Spanish Government) in 2019 with a dissertation about the utilization of concentrated solar energy in metallurgy and materials. He received prize to the best Ph. D. in the category of Experimental Science and Technology by the Real Academy of Doctors of Spain. Now he is postdoctoral researcher of the Nanomaterials and Nanotechnology Research Center from the Spanish National Research Council granted within the Juan de la Cierva-Formación program of the Spanish Ministry of Science and Innovation.

 

Luis Felipe Verdeja González has a Ph.D. in Chemical Sciences from the University of Oviedo, where he is Professor of Materials Science and Head of the Siderurgy, Metals and Materials Group (Sid-Met-Mat), and Head of the Department of Materials Science and Metallurgical Engineering of the University of Oviedo. His research focuses on the application, maintenance, and wear of refractory linings in blast furnaces and other metal and steels production processes.