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HEAT TREATING FURNACES

Heat treating furnaces may be classified into two general categories, batch and continuous, and there are many different types in each group. The simplest furnaces are the direct-fired batch type, with manual controls. Installations for large production lines are more elaborate and are usually continuous furnaces, with automatic programming controls. In some cases controls are included in the furnace for controlling the atmosphere in the working chamber in order to obtain the desired surface condition. In general, the most common heat treatments performed in furnaces are annealing, normalizing, hardening, spheroidizing, tempering, carburizing, and stress relieving. As a rule heat treating furnaces are not designed for temperatures higher than 2000˚F and, in general they operate at from 800˚F to 1600˚F. Insulation is important in maintaining uniform temperatures and the furnaces are built tight to prevent infiltration of air or loss of special atmospheres. For handling batch loads of material to be heat treated, quenched and tempered quench tanks and cranes should be located so that there is a minimum of time expended in transporting material from the furnace to the quenching medium. Furnaces should also be so arranged as to have a second furnace available for taking material after quenching for such additional treatment as may be required. As a rule, three furnaces are used in operations of this type two for heating and one for tempering the work.

Continuous furnaces are designed with or without auxiliary equipment for atmosphere control, heat being applied either by direct or indirect firing, or electrically. They are especially adapted to zone heating and cooling. A furnace of this type is usually a rotary-hearth furnace used for heating pieces that are to be handled individually, such as gears, shells, cylinders, billets, etc. where they are to be fixture-quenched or handled individually for scale-free hardening without decarburization, for normalizing or drawing. This type of furnace is also used for heating smaller parts loaded in lightweight trays and for pack-carburizing. In this furnace charging and discharging are both accomplished at the same work station. Rotary-hearth furnaces are designed in a wide variety of sizes, to heat from just a few pounds up to 60 tons per hour.

Another type of continuous heat treating furnace is the roller-hearth type used for high production. This is particularly suited for uniform treatment of large quantities of the same material as in the bright annealing of tubes, stampings, drawn parts, etc., and for normalizing, annealing, hardening and tempering steel bars. It is also used extensively for annealing malleable irons, small steel and iron castings and forgings. It is also useful in normalizing flat-rolled products. The roller-hearth furnace is constructed ofasimple furnace or a line of furnaces for zone heating and cooling and, at times, such furnaces have an intermediate section with a tank for quenching.

Conveyor-type furnaces are similar to roller-hearth furnaces, except that in this case belt conveyors are used to carry materials through the furnace. They are particularly adopted for accurately heat treating small pieces which would not ride properly on the roller-hearth. The production rate, or heating cycle, of the continuous conveyor-type furnace iscontrolled by both temperature setting desired and the speed of the conveyor. The belt conveyors are made of an alloy material sufficiently at high temperature to carry the load and are resistant to heat, corrosion, oxidation and abrasion.

heat treating furnaces, manual control, automatic control, insulation, cranes, tempering the work, auxiliary equipment, heating and cooling, gears, billets, drawing, wide variety of sizes, stamping, malleable iron, heating cycle, conveyor.

Task 6. Answer the following questions:

1. What are the two main types of heat treating furnaces?

2. What are the simplest furnaces?

3. What kinds of heat treatments can be performed in furnaces?

4. What temperatures are usually used in heat treating furnaces?

5. Why is insulation important in furnaces for heat treatment?

6. Where should the quenched and tempered tanks be located?

7. What types of continuous furnaces do you know?

8. When is a rotary-hearth furnace used?

9. What are the sizes and capacity of rotary-hearth furnaces?

10. For what is a roller-hearth furnace especially suited?

11. What is the construction of a roller-hearth furnace?

12. What is the main difference between roller-hearth and conveyor-type furnaces?

13. By what is the production rate of conveyor-type furnaces controlled?

14. What material is used for making conveyors of conveyor-type furnaces?

1. What is metal physics?

2. What does metal physics deal with?

Read the following abstract and check your answers:

Metal Physics is a branch of physics that deals with the structure and properties of metals. Like dielectric physics and semiconductor physics, metal physics is a subdivision of solid-state physics. Modern metal physics represents a synthesis of microscopic theory, which explains the properties of metals by the distinctive features of the atomic structure of the metals, and metal science, which uses the methods of thermodynamics, continuum mechanics, and other fields to investigate the structure and properties of real metallic materials. The primary physical and chemical properties of metals were studied as early as the 19^th century because metals were used so extensively. The nature of these properties could not be understood, however, without developing the concepts of the atomic structure of matter.

фізика твердого тіла, підрозділ, високочастотний, поява, просування вперед (прогрес), гратка, надпровідність, дислокації, несистематичний.

SOLID STATE PHYSICS

Modern solid state physics is a young discipline. The field has developed especially rapidly during the last 50 years. It is developed to the extent that now solid state physics is the largest sub-field of physics. The fabrication of high frequency germanium diodes for radar during the war and later the advent of the transistor, have been cited as decisive factors. The rise in importance of non-ferrous metals, the zone refining and growth of pure metal crystals and the understanding of the role of dislocations also occurred during this period.

The modern theory of solids has developed to the point where we now know how to qualitatively explain most observed solid state phenomena. Interesting new developments are taking place at an ever-increasing rate. This can be illustrated by citing recent advances in both linear and non-linear optics, progress in understanding electronic band structure, knowledge of lattice vibrations and of the interaction of defects and vibrations, the explanation of superconductivity along with other new transport phenomena and the nature of dislocations and mechanical properties.

The understanding and control of solid state phenomena presents an exciting intellectual challenge. At present we can describe various crystal structures, but the question of why a particular structure forms cannot yet be satisfactorily answered.

From the developments mentioned above it becomes apparent that much of solid state physics stands on the borderline between science and technology. This, indeed, is part of the strength and the fascination of the field.

The control and understanding of the solid state of matter have been too of man’s goals for centuries. Until very recently, however, the methods used by man for working solid materials were more art than science. Lasting contributions to the theory of solids before 1900 are few and far between.

field, rapidly, fabrication, advent of the transistor, decisive factor, non-ferrous metals, pure metal crystals, to occur, solid, new developments, take place, ever-increasing rate, lattice vibrations, borderline, state of matter.

1. Зараз ми знаємо, як якісно пояснити більшість явищ, що відбуваються в твердому тілі.

2. Швидкий розвиток фізики твердого тіла можна проілюструвати останніми досягненнями як в лінійній так і в нелінійній оптиці.

3. Ми можемо описати різні кристалічні структури, але не можемо точно пояснити чому утворюється та чи інша структура.

1. Відомо, що фізика твердого тіла – молода галузь науки.

2. Повідомлялось, що цікаві нові відкриття з’являються з всезростаючою швидкістю.

Task 6. Answer the following questions:

фізика металів, лінія розділу, прикладна наука, впроваджувати, рентгеноструктурний аналіз, неруйнівне тестування.

PHYSICS OF METALS

Physics of Metals is a part of physics of solid body. At our Institute it was developed into an independent branch about 50 years ago. Professor Gridnev was the founder of the department of physics of metals. Later on he became the director of the Scientific Research Institute of the Physics of Metals.

One can’t draw a distinct demarcation line between the physics of metals and physics of solid body. Physics of metals is sooner the applied science, while the physics of solid body is theoretical one. Physics of metal treats of different processes occurring in liquid and gaseous media and various techniques of their investigation.

Physics of Metals is closely connected with such applied sciences as mechanical and thermal treatment, radio-electronics, etc. Such methods as electronic microscopy and X-ray analyses are widely applied in the field.

Specialists graduates from this department can work in different fields of the peoples’ economy implementing and developing new methods of non-destructive testing and physical processes control.

independent branch, the founder, applied science, liquid and gaseous media, investigation, mechanical treatment, thermal treatment, non-destructive testing.

появлятись, роздуми (мемуари), квантова теорія металів, магнетизм, фізика напівпровідників, кристалохімія, кристалізуватись, точкові дефекти, невпорядкованість кристалів, структура твердого тіла, старі та нові аспекти, фазові перетворення, співвідношення структури та властивостей, розробка матеріалів, хімічна активність твердих тіл, межа розділу (область взаємодії), окислення, видатний дослідник, простір, основи фізики та хімії.

SOLID STATE PHYSICS AND CHEMISTRY

Solid state physics is closely connected with solid state chemistry. Both of these disciplines emerged only in last century, because a knowledge of crystal structure is indispensable to both and that only emerged when X-ray diffraction from crystals was discovered.

The beginnings of the enormous field of solid-state physics were concisely set out in a fascinating series of recollections by some of the pioneers at a Royal Society Symposium. In much greater detail it was described in a large, impressive book by a number of historians of the science (Hoddeson et al. 1992). They dealt in depth with such themes as: the roots of solid-state physics in the years before quantum mechanics, the quantum theory of metals and band theory, point defects and colour centres, magnetism, mechanical behaviour of solids, semiconductor physics and critical statistical theory.

As for solid-state chemistry, it began in the form of ‘crystal chemistry’, the systematic study of the chemical factors that govern the structures in which specific chemicals and chemical families crystallise. The most important addition to crystal chemistry was the examination of crystal defects - point, line, planar defects, including grain boundaries and interphase boundaries. In fact, crystal defects were first studied by the solid-state physicists (Shockley et al. 1952). This was followed some years later by a classic book of Dutch chemist Kroeger (1974) (on crystal defects and their linkage to non-stoichiometry) and by a book on disorder in crystals (Parsonage and Staveley 1979). The current status is surveyed in an excellent overview (Rao and Gopalakrishnan 1986, 1997). Chapter headings of the book clarify the present status of solid-state chemistry: Structure of solids - old and new facets; new and improved methods of characterization; preparative strategies; phase transitions; new light on an old problem - defects and non-stoichiometry; structure-property relations; fashioning solids for specific purposes - aspects of materials design; reactivity of solids. The linkage with materials science is clear enough.

The enormous amount of research at the interface between physical and structural chemistry has been reviewed recently by Schmalzried in a book about chemical kinetics of solids, dealing with matters such as morphology and reactions at evolving interfaces, oxidation, internal reactions, reactions under irradiation, etc.

An eminent researcher at the boundaries between physics and chemistry, Howard Reiss, some years ago explained the difference between a solid-state chemist and a solid-state physicist. The first thinks in configuration space, the second in momentum space; so, one is the Fourier transform of the other.

Both fields are very well supplied with journals, some even combining physics with chemistry (e.g., Journal of Physics and Chemistry of Solids). Some journals are focusing on solid-state physics without indicating this in the title, such as Philosophical Magazine. Many papers in both solid-state physics and solid-state chemistry are published in general physics and chemistry journals.

It is striking that in the English-speaking world no departments of either solid-state physics or of solid-state chemistry are to be found. Students are given a broad background in physics or in chemistry, and in the later parts of their courses they are given the chance to choose emphasis on solids if they so wish... but their degrees are simply in physics or in chemistry. In Europe, where specialised ‘institutes’ take the place of departments, there are many institutes devoted to subfields of solid-state physics and solid-state chemistry, and a few large ones cover these respective fields in their entirety.

solid-state physics, to be connected with, X-ray diffraction, to deal with, quantum mechanics, chemical factors, to crystallise, planar defects, stoichiometry, new facets, improved methods, phase transitions, chemical kinetics of solids, reactions under irradiation, configuration space, Fourier transform, to supply, to combine.

1. They discovered X-ray diffraction in XX-th century.

2. The scientists set out the beginnings of the solid-state physics at the Royal Society Symposium in 1980.

3. A number of historians of the science described a solid-state physics in much greater detail.

4. The solid-state physicists studied crystal defects for the first time.

5. Recently Schmalzried has reviewed the research at the interface between physical and structural chemistry.

6. General physics and chemistry journals publish many papers on solid-state physics.

1. Why have solid-state physics and solid state chemistry emerged only last century?

2. When was the solid-state physics described for the first time?

3. What was the most important addition to crystal chemistry?

4. What is the present day status of solid state chemistry?

5. How did H. Reiss explain the difference between a solid-state physicist and solid-state chemist?

6. Are there any solid-state physics or solid-state chemistry departments in the English-speaking world?

галузь інженерії, виробництво металічних порошків, спікання, формування порошків, захисне середовище, пористий, застосувати термомеханічну обробку, вихрова (шарова, вібраційна) дробарка, розбризкування рідких металів, водний розчин, форми для пресування, небажані домішки, усувати, пористість, порошкова металургія, подрібнення металу, відновлення, розміри, густина, спікання, отримувати, чисті порошки, змащування, не змішуваний компонент.

POWDER METALLURGY

Powder metallurgy is a branch of engineering embracing various methods of producing powders of metals and metal-like compounds, half-finished and finished products made of them without melting the main component.

The technology includes the following operations: metal powders production and preparing charge with the pre-set chemical composition and technological characteristics, forming powders into parts (mainly by pressing), s intering, that is heat-treatment at the temperatures higher than the melting temperature of all the metal or its main components.

After sintering the parts are somehow porous. Toeliminate porosity, to improve mechanical properties and obtain exact dimensions additional pressure treatment of sintered parts is applied. Sometimes additional heat, thermo-chemical or thermo-mechanical treatment is applied. In some variants of technology the operation of forming no longer arises as powders strewn into special forms are sintered. In some cases pressing and sintering are combined into one operation.