Unit VI. Powder Metallurgy

Vocabulary

powder порошок

to sinter спекать

to long связывать, соединять

to lack нуждаться

to lubricate смазывать

compact - прессованный брикет:

о blend - смешивать

ejection - выброс, выталкивание

void - пустота

adhesion - прилипание

coherent - однородный

to facilitate- облегчать

to interlock- соединяться, сцепляться

range - щредел, размах

durability - долговечность, срок службы (металлов)

to double - удваивать

consumption- потребление

rolled - stock - прокат

Exercise 1. Choose the correct Russian equivalents to the English terms :

1. plunger - порошок

2. to lack - прочность

3. purity - плунжер

4. to blend- чистота

5. sintering - однородный

6. strength - смешивать

7. powder - прилипание

8. adhesion - нуждаться

9. coherent- спекание

Exercise 2. Choose the corresponding synonyms to the words

1. to produce - 1. use

2. to obtain 2. hard

3. solid 3. to manufacture

4. to reduce 4. volume

5. application 5. to interlock

6. to bond 6. to decrease

7. to lack 7. to get

8. amount 8. to need

Exercise 3. Translate the words of the same root. Define speech parts.

1. to sinter - sintered - sintering

2. to produce - produced - producing - product

3. to press - pressed - pressure

A. to heat - heated - heating - heat

5. to lubricate - lubricant, lubricating - lubrication

6. to compact - compact - compacting

7. to reduce - reduced - reducing - reduction

Exercise 4. Translate the following word combinations.

Powder metallurgy, produced by pressure, melting point, properties of the finished product, manufacturing methods, to find wide application, to ensure economical prodгction, to ensure economical production, sintered compacts, accurate.

Exercise 5. Live verbs corresponding to the given nouns and translate them:

Melting, sintering, manufacturing, compacting, heating, reducing, welding, lubricating, pouring, increasing.

Exercise 6. Remember the following definitions.

1. Powder metallurgy in me at of producing commercial products from metallic powders by pressure.

2. Sintering in the operation of heating a "green compact" to an elevated tetemperate.

3. Compacting is a process of pouring a measured amount of the appropriate powder into the die cavity and then pressing the metal powder into a coherent mass by plungers.

TEXT A

Powder metallurgy is the art of producing commercial product; from metallic powders by pressure. Heat, which may be used in the process, must be kept at a temperature below the melting point of the powder. The application of heat during the process, or subsequently, is known as sintering and results in bonding the fine particles together, thus improving the strength and other properties of the finished product.

Although all metals can be produced in the powder form, only a few find wide application in the manufacture of pressed-metal parts. Some lack the desired characteristics or properties which are necessary for economical production. The two principal kinds in use are the iron- and copper- base powders. Both lend themselves well to this process and are produced in a wide variety of alloys.

Powder for a given product must be carefully selected to insure economical production and to obtain the desired properties in the final compact. Practically all powders have lubricants in the final compact; Practically all powders have lubricants added in the blending operation to reduce die wall friction and to the porosity, they permit a greatly increased production rate and are necessary in presses using automatic powder feed. I

It is extremely important that all the metal powders used during production be uniformly mixed so that uniform results are obtained. This is especially true when two or more powders are used together to form an alloy or mixture. Lubricants, volatilizing agents ,or non-metallic particles are often included in the powder mix for special purposes, and must be homogeneously distributed.

Compacting the powder is an important step in the powder metallurgy method.

to lend oneself- годиться к чему-либо. "Volatilizing agents -подгоночные веществ

In addition lb producing the required shape, the compacting operation also influences (the subsequent sintering operation and governs, to a large extent, properties of the final product. Several of the most important effects of compacting are: 1. To reduce voids between powder particles and increase density of the compact. 2. To produce adhesion and cold welding of the powder and sufficient green strength. 3. To plastically deform the powder to allow recrystallization during subsequent sintering.4. To plastically deform the powder to increase the contact areas between the powder particles, increasing green strength and facilitating subsequent sintering. . ,

Compacting is mostly performed by pouring a measured amount of the appropriate powder into the die cavity and then introducing one or more plungers to press the metal powder into a coherent mass. A measured volume of powder is usually used, although in some cases a definite weight of powder is more suitable. |

The operation of heating a "green compact" to an elevated temperature is known as sintering. It is the process by which solid bodies are bonded by atomic forces. By the application of heat the particles are pressed into more intimate contact, and the effectiveness of surface-tension reactions is increased. Plasticity is increased, and better mechanical interlocking is produced. Also any interfering gas phase present is removed by the heat. The temperatures used in sintering are usually well below the melting point of the principal powder constituent but may vary over a wide range up to a temperature just below the melting point.

Sintered compacts are often sufficiently accurate to be placed in service immediately, or after a minimum of machining, but some products requiring very accurate dimensions must be brought to exact size by subsequent operation of sizing.²

Exercise 7. Read the text again and say what it deals with in English. Exercise 8. Answer the following questions.

1. What is powder metallurgy?

2. What temperatures may be used in the process? 3.What does the application of heat result in?

4.Can all metals be produced in the powder form?

5, What are the two principle kinds of powders in use? ,

6.For what purpose do all powders have lubricant added? .

7.Why is it extremely important for all the metal powders to be uniformly mixed?

8. What is compacting? What is its significance?

9.How is compacting mostly performed?

l0.What is sintering?

1 l.What are 'he main factors in sintering?

12.Can sintering compacts be used immediately?

Exercise 9. Complete the following sentences.

¹ to govern - определять

² sizing - обработка точно по размеру

a) Heat, which may be used in the process, must be kept at a temperature below...of the powder.

b). The iron and copper-base powders ... well to this process and are produced in a wide variety of alloys.

c). This is especially true when two or more powders are used together — d). Sintering in a process by which solid bodies... by atomic forces, e). Sintering compacts are often;sufficiently ... to be placed in service immediately. (point, are bonded, the melling point, lend, to form an alloy).

Exercise 10. Write a summary of the text according to the plan.

a).The process of powder metallurgy and temperatures used in it.

b). Metal powders principally used in powder metallurgy.

c). Selection of quality powders and adding lubricants.

d). The importance of the uniform mixing of powders,

e). The operation of compacting and "green compact" as its product.

f). The subsequent operation of sintering and its purpose.

g). The factors of the process: temperature, time and atmosphere.

h). Possibility of using sintering compacts in service.

Exercise 11. Speak on the topics.

1. Powder metallurgy and its use in industry.

2. The process of compacting.

3. The operation of sintering.

4. The factors used in sintering.