Task 10. Retell the text “My Future Speciality”.

UNIT 3

FUNDAMENTALS OF CASTING PRACTICE

Casting is based on the use of one of the physical properties of liquids. This property consists in the ability of a liquid to take the shape of the vessel it is poured into (under the force of gravity).

Metals and alloys heated to a temperature exceeding the melting point become liquid. When cooled, liquid metal or alloy, poured into a vessel, solidifies. The solidified metal will keep the shape of the vessel into which it was poured in liquid state. After the vessel is broken, its shape is kept by the solidified metal. Thus, by using vessels of different shapes, castings of different configurations can be obtained from liquid metals.

In blanks production by casting this role is played by foundry mould. The parts of a mould are normally fabricated separately and assembled afterwards. Inside the mould there is a cavity, which has the shape of the blank required. This cavity is filled with molten metal through gating arrangement.

The starting material for producing an iron or steel melt are foundry and conversion pig, cast-iron and steel scrap, chips, ferro-alloys and non-metallic materials such as fuels and fluxes.

Various melting furnaces are available to melt and overheat ferrous and non-ferrous metals and alloys. Shaft-type furnaces, called cupolas, provide for molten cast iron; electric and open-hearth furnaces for steel, and flame furnaces for cast iron and non-ferrous alloys.

To obtain the required structure and mechanical properties of castings and to relieve internal stresses, the cast pieces are often subjected to heat treatment-heating and cooling in ovens strictly to the prescribed schedule (the time and temperature of treatment).

Task 1.

Memorise the following words:

blank	заготівка
cast-iron	чавун
flame furnace	полум’яна піч
gating arrangement	ливникова система
mould	ливарна форма
open-heart furnace	мартенівська піч
shaft-type furnace	шахтна піч
steel scrap	стальний брухт

Task 2.

Find in the text English equivalents to the following words and word combinations:

литво, ливарне виробництво, фізичні властивості, механічні властивості, виготовляти, форма, точка плавлення, сила тяжіння, сплав, охолоджувати, твердіти, раковина, збирати, вихідний матеріал, флюс, вагранка, внутрішнє напруження, термічна обробка, режим (графік).

Task 3.	Match the words from column A with the Ukrainian equivalents from column B:
А	В
1. casting 2. property 3. liquid 4. ability 5. gravity 6. alloy 7. vessel 8. blank 9. mould 10. cavity 11. melt 12. scrap 13. chips 14. fuels 15. oven 16. schedule	a. заготівка b. графік c. тяжіння d. стружка e. піч f. лиття g. розплав h. здатність i. порожнина j. брухт k. сплав l. ливарна форма m. пальне n. властивість o. посудина p. рідина

Task 4.

Give Ukrainian equivalents to the following words and word combinations:

casting, foundry, to take the shape, to keep the shape, under the force of gravity, the solidified metal, melting point, castings of different configurations, liquid metal, blank production, foundry mould, separately, afterwards, the blank required, molten metal, various furnaces, cupola, to relieve internal stresses, the cast pieces, strictly to the prescribed schedule.

Task 5.

Make up word combinations and translate them:

1. physical	a. metal
2. melting	b. mould
3. solidified	c. melt
4. liquid	d. production
5. blank	e. stresses
6. foundry	f. materials
7. gating	g. materials
8. starting	h. properties
9. steel	i. furnace
10. non-metallic	j. treatment
11. melting	k. state
12. open-hearth	l. furnace
13. internal	m. point
14. heat	n. arrangement

Task 6.

Find in the text antonyms to the following words:

solid, to cool, the same, prior to, outside, metallic, unavailable, ferrous, crystallize.

Task 7.

Fill in the gaps with the missing words:

1. Casting ______ on the ability of a liquid to take the shape of the vessel it is poured into.

2. When metals ______ they become liquid.

3. Liquid metal ______ into the vessel.

4. The cavity inside the vessel ______ with molten metal through gating arrangement.

5. When cooled, liquid metal ______.

6. When metal solidifies the vessel ______.

7. The shape of the vessel ______ by the solidified metal.

8. We can ______ castings of different configurations by using vessels of different shapes.

Task 8.

Answer the following questions:

1. What is casting based on?

2. What shape does the solidified metal keep?

3. How can castings of different configurations be obtained from liquid metals?

4. How is the mould made?

5. In what way is the cavity of the mould filled with molten metal?

6. Name the starting material for producing an iron or steel melt.

7. What melting furnaces do you know?

8. What are the cast pieces often subjected to?

Task 9.

Think of the title to each paragraph of the text and write them down.

Task 10.

Retell the text.

UNIT 4

CASTING AS A METHOD OF BLANK PRODUCTION

The main advantages of casting as a method of blank production lie in:

A. The possibility of casting production from the majority of construction alloys and, in particular, from those which are not suitable for forming (for instance, various sorts of cast-iron).

B. The possibility of producing blanks of a very complicated shape, especially blanks with a complicated shape of inner cavities.

C. The possibility of producing blanks weighting from a few grams up to several hundreds of tons.

Various technological processes are used in the foundry practice. The differences between them lie mainly in the sort of materials used for the foundry moulds, the method of the mould manufacture and conditions in which liquid metal is poured into the moulds. The basic moulding process is sand-mold casting which accounts for 80% of the total output of cast products.

Castings are made from irons and steels and from non-ferrous alloys such as copper, aluminium, magnesium, zinc and other types. The castings from metals and alloys find wide use as parts of machines and instruments turned out by the machine-building and instrument-making industries.

However, in spite of great advantages, the method of casting is not universal as it has its own disadvantages, for example, difficulty and, sometimes, impossibility to produce castings with the desired accuracy of dimensions and surface finish.

That is why special casting processes find an ever increasing application. These are permanent-mold casting, die casting, investment casting, shell casting, centrifugal casting and other precision processes which produce cast components of increased dimensional accuracy and low surface roughness with minimum finish allowances.

Task 1. Find in the text English equivalents to the following words and word combinations:

виробництво заготівок, різні сорти, складна форма, придатний для штамповки, внутрішня порожнина, застосування, точність, піщана форма, приладобудівний, лиття в постійні форми, лиття в кокіль, точне лиття по виплавленим моделям, центробіжне лиття, обробка поверхні, мінімальні припуски на обробку, шорсткість поверхні.

Task 2. Find in the text synonyms to the following words:

to produce, to apply, to have got

Task 3. Match the words with their translations:

1. blank	a) порожнина
2. finish	b) ливарна форма
3. cavity	c) шорсткість
4. mould	d) кокіль
5. shell	e) припуски
6. surface	f) заготівка
7. die	g) поверхня
8. roughness	h) точність
9. accuracy	i) обробка
10. allowances	j) оболонка

Task 4. Combine the words and translate the word combinations into Ukrainian:

1. construction	a) cavities
2. complicated	b) industry
3. inner	c) casting
4. foundry	d) alloys
5. die	e) accuracy
6. total	f) practice
7. instrument-making	g) finish
8. surface	h) roughness
9. dimensional	i) output
10. surface	j) shape

Task 5. Give Ukrainian equivalents to the following words and word combinations:

blank production, construction alloys, cast-iron, very complicated shape, inner cavities, to weight, foundry practice, mould, liquid metal, to pour, sand-mold casting, total output, castings, non-ferrous alloys, to turn out, machine-building and instrument-making industries, desired accuracy of dimensions, to find application, permanent-mold casting, die casting, investment casting, shell casting, centrifugal casting.

Task 6. Answer the following questions:

1. Where do the advantages of casting as a method of blank production lie?

2. Where do the differences between various technological foundry processes lie?

3. What is the basic moulding process?

4. What are castings made from?

5. Where do the castings from metals and alloys find wide use?

6. What disadvantages has the method of casting?

7. What special casting processes do you know?

UNIT 5

BASIC FACTORS IN CASTING

In casting, a solid is melted, heated to proper temperature, and sometimes treated to modify its chemical composition. The molten material, generally metal, is then poured into a cavity or mould, which contains it in proper shape during solidification. Thus, in a single step, simple or complex shapes can be made from any metal that can be melted. The resulting product can have virtually any configuration the designer desires. In addition, the resistance to working stresses can be optimized, directional properties can be controlled, and a pleasing appearance can be produced.

Cast parts range in size from a fraction of an inch and a fraction of an ounce (such as the individual teeth on a zipper), to over 30 feet (10 m) and many tons (such as the huge propellers and stern frames of ocean liners). Moreover, casting has marked advantages in the production of complex shapes, of parts having hollow sections or internal cavities, of parts that contain irregular curved surfaces (except those made from thin sheet metal), of very large parts, and of parts made from metals that are difficult to machine. Because of these obvious advantages, casting is one of the most important of the manufacturing processes.

Today, it is nearly impossible to design anything that cannot be cast by means of one or more of the available casting processes. However, as in all manufacturing techniques, the best results and economy are achieved if the designer understands the various options and tailors the design to use the most appropriate process in the most efficient manner. The various processes differ primarily in the mould material (whether sand, metal, or other material) and the pouring method (gravity, vacuum, low pressure, or high pressure). All of the processes share the requirement that the materials solidify in a manner that would maximize the properties, while simultaneously preventing potential defects, such as shrinkage voids, gas porosity, and trapped inclusions.

Six basic factors are involved in casting processes:

Mould Cavity. A mould cavity, having the desired shape and size, must be produced with due allowance for shrinkage of the solidifying metal. Any complexity of shape desired in the finished casting must exist in the cavity. Consequently, the mould material must be able to reproduce the desired detail and also must have a refractory character so that it will not be significantly affected by the molten metal that it must contain. Either a new mould must be prepared for each casting (expendable moulds), or the mould must be made from a material that can withstand being used for repeated castings. The latter type is known as permanent moulds. Since the permanent moulds are made of metal or graphite and are quite costly, their use is generally restricted to large production runs. The more economical expendable moulds are generally preferred for the production of smaller quantities.

Melting Process. A melting process must be capable of providing molten material not only at the proper temperature, but also in the desired quantity, with an acceptable quality, and within a reasonable cost.

Pouring Techniques. A pouring technique must be devised to introduce the molten metal into the mould. Provision should be made to permit the escape of all air or gases in the mould before pouring and those generated by the action of the hot metal entering the mould. The molten metal can then completely fill the cavity, producing a quality casting that is fully dense and free of defects.

Solidification Process. The solidification process should be properly designed and controlled. Provision must be made so that the mould will not cause too much restraint to the shrinkage that accompanies the cooling of solidified metal. Otherwise, the casting will crack when it is still hot and its strength is low. In addition, the design of the casting must be such that solidification and solidification shrinkage can occur without producing internal porosity or voids.

Mould Removal. It must be possible to remove the casting from the mould (i.e., mould removal). When the metal is poured into moulds that are broken apart and destroyed after each casting is made, there is no serious difficulty. However, in processes where permanent moulds are used, removal of the casting may present a major design problem.

Cleaning, Finishing and Inspection. After the casting is removed from the mould, various cleaning, finishing, and inspection operations may need to be performed. Extraneous material that is attached where the metal entered the cavity, excesses at mould parting lines, and mould material that is attached to the casting surface must all be removed.

Task 1. Find in the text English equivalents to the following words:

лиття, змінювати склад, плавити, значні переваги, тонколистовий метал, технології виробництва, формувальний матеріал, метод заливання, запобігати потенційним дефектам, усадочні порожнини, пористість, порожнина ливарної форми, припуски, тугоплавкий, готові виливки, ливарні форми одноразового використання, постійні форми, процес плавлення, бажана кількість, прийнятна ціна, розплавлений метал, якісний виливок, без дефектів, супроводжувати, процес кристалізації, охолодження, тріскатись, видалення виливка з ливарної форми, очистка, обробка, перевірка, залишки матеріалу, лінія рознімання.

Task 2. Give Ukrainian equivalents to the following words and word expressions:

solid, heated to the proper temperature, to modify, to pour into a cavity, the resulting product, cast parts, casting processes, complex shape, pouring method, maximize the properties, to solidify, to prevent defects, trapped inclusions, mould cavity, expendable moulds, repeated castings, reasonable cost, desired quantity, escape of gases, to fill, dense, solidification process, strength, to remove the casting from the mould, parting surface, gating system.

Task 3. Match the following words with their translations:

1. complex shape	a) тугоплавкий
2. permanent mould	b) бажана кількість
3. expendable mould	c) якісний виливок
4. shrinkage voids	d) одноразова форма
5. solidification shrinkage	e) постійна форма
6. proper shape	f) усадочні пустоти
7. desired quantity	g) складна форма
8. acceptable quality	h) усадка під час кристалізації
9. refractory character	i) належна форма
10.quality casting	j) прийнятна якість

Дата добавления: 2015-11-14