Preface

Heat treatment and surface engineering represent crucial elements in the design and manufacture of strategic components in a wide range of market sectors and industries including air, sea and land transportation, energy production, mining, defense or agriculture. Their influence is broad and of major importance for economics, society and the environment. Although human metallurgy and heat treatment were practiced for millennia, an understanding of the science and associated principles has only been developed in the last century. The progress in heat treatment of bulk alloys was accompanied by an application of heating/quenching to a modification of metal surfaces and development of technologies such as case hardening, thermochemical treatments and coatings, leading in 1980s to a creation of modern surface engineering. Today, surface engineering is seen as a critical enabling technology underpinning major industry sectors.

The generally accepted definition of heat treatment is "heating and cooling a solid metal or alloy in such a way so as to obtain specific conditions and/or properties". Thus, heat treatment represents a combination of thermal and also thermochemical operations aimed at altering mostly physical and mechanical but also chemical properties of materials without changing the product shape. Its ultimate purpose is to increase service life of a product by increasing strength and hardness, or prepare the material for enhanced manufacturability. At a technical level, heat treatment is a technological process which is conducted in furnaces and involves thermal phenomena, phase transformations and mechanical phenomena, mainly stresses. The most pronounced beneficial effect of heat treatment in altering microstructure and modifying properties is to a range of ferrous alloys and nonferrous alloys of aluminum, copper, nickel, magnesium or titanium. Of all materials, steel as the most common and the most important structural material, is particularly suitable for heat treatment. Heat treatment of steel is inherently associated with an improvement in strength, ductility, machinability, formability and involves normalizing, annealing, stress relieving, surface hardening, quenching, tempering, cold and cryogenic treatment.

The above definition excludes processes where heating and cooling are performed inadvertently such as welding or forming. A similar case is with metal heating for the purpose of diffusion bonding. Apart from metals, heat treatment used for non-metallic

#### X Preface

materials is also excluded from this definition. However, controlled heating and quenching accompany many modern manufacturing technologies with bulk material precursors as well as thin films and coatings. Similarly as for bulk metallic alloys, thermal routes affect the microstructure and properties of bulk non-metallic materials, particulate forms and thin layers. Understanding and controlling these processes is of the same importance as in the case of conventional heat treatment.

This book was created by contributions from experts in different fields of materials science from over 20 countries. It offers a broad review of recent global developments in an application of thermal and thermochemical processing to modify the microstructure and properties of a wide range of engineering materials. Although there is no formal partition of the book, chapters represent two different application areas of heat treatment. The first group covers the conventional heat treatment with processing of bearing rings, wrought and cast steels, aluminum alloys, fundamentals of thermochemical treatment, details of carbonitriding and a design of cooling units. The second group describes a use of non-conventional thermal routes during manufacturing cycles of such materials as vanadium carbides, titanium dioxide, metallic glasses, superconducting ceramics, nanoparticles, metal oxides, battery materials and slag mortars. Each chapter contains a rich selection of references, useful for further reading.

A mixture of conventional and novel applications, exploring a variety of processes employing heating, quenching and thermal diffusion, makes the book very useful for a broad audience of scientists and engineers from academia and industry. In order to benefit from opportunities created by heat treatment, its capabilities for each individual material and service conditions should be understood and implemented at the stage of a component design. Since the design stage requires often multidisciplinary knowledge, metallurgy and heat treatment may not be there the core expertise. Therefore, I hope that the book will also attract an audience from outside of metallurgy area not only to generate the genuine interest but also to create new application opportunities for modern heat treatment and surface engineering.

> **Frank Czerwinski** CanmetMATERIALS, Natural Resources Canada Hamilton, Ontario

X Preface

for further reading.

materials is also excluded from this definition. However, controlled heating and quenching accompany many modern manufacturing technologies with bulk material precursors as well as thin films and coatings. Similarly as for bulk metallic alloys, thermal routes affect the microstructure and properties of bulk non-metallic materials, particulate forms and thin layers. Understanding and controlling these processes is of

This book was created by contributions from experts in different fields of materials science from over 20 countries. It offers a broad review of recent global developments in an application of thermal and thermochemical processing to modify the microstructure and properties of a wide range of engineering materials. Although there is no formal partition of the book, chapters represent two different application areas of heat treatment. The first group covers the conventional heat treatment with processing of bearing rings, wrought and cast steels, aluminum alloys, fundamentals of thermochemical treatment, details of carbonitriding and a design of cooling units. The second group describes a use of non-conventional thermal routes during manufacturing cycles of such materials as vanadium carbides, titanium dioxide, metallic glasses, superconducting ceramics, nanoparticles, metal oxides, battery materials and slag mortars. Each chapter contains a rich selection of references, useful

A mixture of conventional and novel applications, exploring a variety of processes employing heating, quenching and thermal diffusion, makes the book very useful for a broad audience of scientists and engineers from academia and industry. In order to benefit from opportunities created by heat treatment, its capabilities for each individual material and service conditions should be understood and implemented at the stage of a component design. Since the design stage requires often multidisciplinary knowledge, metallurgy and heat treatment may not be there the core expertise. Therefore, I hope that the book will also attract an audience from outside of metallurgy area not only to generate the genuine interest but also to create new

application opportunities for modern heat treatment and surface engineering.

**Frank Czerwinski** CanmetMATERIALS, Natural Resources Canada

Hamilton, Ontario

the same importance as in the case of conventional heat treatment.

**Chapter 1** 

© 2012 Pohanka and Kotrbáček, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Pohanka and Kotrbáček, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Design of Cooling Units** 

Michal Pohanka and Petr Kotrbáček

Additional information is available at the end of the chapter

Microstructure and nature of grains, grain size and composition determine the overall mechanical behavior of steel. Heat treatment provides an efficient way to manipulate the properties of steel by controlling the cooling rate. The way of heat treatment depends on many aspects. One of the most important parameter is the amount of production. Another important parameter is the size of products. We focus here on large production such as interstand [1] and run-out table cooling of hot rolled strip, run-out table cooling of sheets and plates, cooling of long products at the exit from a rolling mill, cooling of rails, tubes and special profiles [2], continuous hardening and heat treatment lines for steel strips. Such a treatment is called in-line heat treatment of materials and has become frequently used by hot rolling plants. This method achieves the required material structure without the necessity of reheating. In-line heat treatment is characterized by running of hot material through the cooling section. However, many of discussed topics can be applied on smaller

The design procedure of cooling sections for obtaining the demanded structure and mechanical properties is iterative research involving several important steps. We begin with the Continuous Cooling Transformation (CCT) diagram for the selected material. Numerical simulation of cooling follows to find appropriate cooling intensity and its duration. Knowing the desired cooling intensity new cooling section is designed and tested under the laboratory conditions [3]. From the laboratory experiments boundary conditions are obtained and tested using a numerical model. When the best solution is found it is tested on the real sample and the result structure is studied. In most cases the process must be repeated as the CCT diagram is aimed at a different size of the sample and the cooling rate

**for Heat Treatment** 

http://dx.doi.org/10.5772/50492

**1. Introduction** 

production as well.

in the designed section is not constant.

**Chapter 1** 
