English Reader for Technical Students. Учебное пособие

Exercise 1. Find English equivalents to the following Russian words

Exercise 2. Group the following words into sentences and translate them:

1.be, these, kept, elements, must, low, at, concentrations, to, very, order, in, to, risk, avoid, of. The, failure, premature, part.

2.is, pressure-depend, metallurgy, reactions, VIM, primarily-aimed, at.

3.produced, the VIM, must, a, and, material, undergo, process, remelting, resolidification.

4.concept, a, design, the, is, VID, on, modular, based.

Exercise 3. Are these statements true or false?

1.In a VIM furnace the slag is not transported to the crucible wall by the bath movement.

2.The VIM produced material must not undergo a remelting resolidification process.

3.The casting process is not realized by using a ceramic launder.

4.The VIDP furnace has no better control of the process atmosphere.

5.The VIDP has higher desorption and leakage rates compared to a conventional VIM furnace.

Exercise 4. Answer the questions:

1.How is the slag transported in a VIM?

2.What is a primary aim of VIM metallurgy?

3.What is it very important

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4.for special applications?

5.What is the VIDP concept based on?

6.What advantages does the VIDP furnace have in comparison with a conventional VIM furnace?

4.5. Vacuum arc remelting (VAR)

VAR is widely used to refine the structure and improve the cleanliness of standard air melted or vacuum induction melted ingots. Vacuum arc remelted steels and superalloys are used in a great number of integrity applications where cleanliness, homogencity, improved fatigue and fracture toughness of the final product are essential. For the production of titanium as well as zirconium the VAR process is used to remelt an electrode made from sponge to produce the solid metal ingot in the first melt. Aerospace, power generation, defense, medical and nuclear industries rely on the properties and performance of these advanced remelted materials.

Process technology and process characteristics. A stable arc operation is important for the quality of the re-melted ingot. The arc is diverted by inhomogeneous magnetic fields. Therefore, a coaxial power connection is needed to eliminate negative influences. The amount of energy supplied to the remelting zone is determined by the required metallurgical result.

For industrial applications a high vacuum is maintained throughout the remelting process in the range of 10 – 2 and 10 – 3 mbar. The intense heat generated by the electric arc melts the tip of the electrode and a new ingot is progressively formed in the water-cooled mould.

Metallurgy. The production of segregation-free ingots demands careful coordination of maximum allowable melting rates and short arc lengths in order to avoid ingot defects like rings, freckles and white spots. The VAR ingot's solidification structure of a given material is a function of the local solidification time and the temperature gradient at the liquid/solid interface. To achieve a directed dendritic primary structure, a relatively high temperature gradient at the solidification front must be maintained during the entire remelting process. The growth direction of the cellular dendrites conforms with the direction of the temperature gradient, i.e. the direction of the heat flow at the moment of solidification at the solidification front. The direction of the heat flow is always perpendicular to the solidification front or, in case of a curved interface, perpendicular to the respective tangent. The growth direction of the dendrites is thus a function of the metal pool profile during solidification. As pool depth increases with the remelting rate, the growth angle of the dendrites, with respect to the ingot axis, also increases.

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In extreme cases, the growth of the directed dendrites can come to a stop. The ingot core then solidifies non-directionally, i.e. in equiaxed grains, leading to segregation and micro-shrinkage. Even in the case of directional solidification, micro-segregation increases with dendrite arm spacing.

Process control. A close control of all remelting parameters is required for reproducible production of homogeneous ingots which are free of macro-segregation and show a controlled solidification structure and superior cleanliness.

To fulfil today's most stringent material quality specifications, VAR furnaces make use of computer controlled process automation. Logic control functions, continuous weighing of the consumable electrode, closed loop control of process parameters (e.g. remelting rate, arc gap based on arc voltage or drop short pulse rale), data acquisition and management tasks are handled by dedicated computer systems. These computer systems communicate via field bus or specific interfaces. An Operator Interface PC (OIP) acting hierarchically as master of the Automatic Melt Control system (AMC) is utilized as interface between operator and VAR process. The operator interface PC serves for process visualization featuring parameter indications, graphic displays and soft keys for operator commands, editing and handling of remelting recipes, data acquisition and storage as well as for generation of melt records. Optionally the operator interface PC can be equipped with an Ethernet network interface which may be utilized for data transfer to other computers connected to the local area network (e.g. supervisory PC, customer's main frame etc.).

Exercise 1. Find English equivalents to the following Russian words

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Exercise 2. Match the definitions with the following words:

Exercise 3. Fill in the blanks with prepositions (in, to, of, by, with, in, of, to, of, to, for, with, to):

1.The amount … energy supplied … the remelting zone is determined … the required metallurgical result.

2.… extreme cases, the growth … the directed dendrites can come … a stop.

3.Even … the case … directional solidification, micro-segregation increases … dendrite arm spacing.

4.Optionally the operator interface PC can be equipped … an Ethernet network interface which may be utilized …data transfer … other computers connected … the local area network.

Exercise 4. Are these statements true or false?

1.VAR is not widely used to refine the structure of standard melted ingots.

2.Medical and nuclear industries don’t rely on the properties of advanced remelted materials.

3.a close control of all remelting parameters is required for reproducible production of homogeneous ingots.

4.The direction of the heat flow is always perpendicular to the solidification front.

Exercise 5. Answer the questions:

1.Where is VAR used?

2.What is a stable arc operation important for?

3.What does the production of segregation-free ingots demand?

4.Why is a close control of all remelting parameters required?

5.Why and how do VAR furnaces make use of computer controlled process automation?

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ГАЛКИНА Татьяна Николаевна ЗАЙЦЕВА Серафима Евгеньевна СМИРНОВА Елена Викторовна ТИНИГИНА Людмила Анатольевна

ENGLISH READER FOR TECHNICAL STUDENTS

Учебное пособие

Редактор Г.Б. Преображенская

Компьютерная верстка Т.Д. Насущновой

Национальный исследовательский технологический университет «МИСиС», 119049, Москва, Ленинский пр-т, 4

Издательский Дом МИСиС, 119049, Москва, Ленинский пр-т, 4

Тел. (495) 638-45-22

Отпечатано в типографии Издательского Дома МИСиС 119049, Москва, Ленинский пр-т, 4

Тел. (499) 236-76-17, тел./факс (499) 236-76-35

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