Advantages and disadvantages of powder metallurgy

Powder metallurgy has the following advantages:

• The possibility of producing materials which are hard or impossible to obtain by other methods (e.g. W, Ta).

• The possibility of obtaining some materials and parts with higher technico-economical characteristics.

• When using pure powders it is possible to obtain sintered materials with less impurities.

• Sintered materials have better properties than melted ones despite the same composition and density.

• It is easier to regulate the dimensions and structure of the sintered materials.

• Moreover, it becomes possible to obtain such types of grain interlocation and shape which are unattainable for melted metals.

A few of the disadvantages of powder metallurgy are as follows:

• The comparatively high cost of powders.

• The necessity of sintering in a protective atmosphere.

• The necessity of applying pure powders to obtain pure metals.

Four groups of metal powder products

Metal powder parts can be divided into four general categories:

Parts having densities of the order of 50 per cent. Such parts are used as filters and for similar applications.

Those parts having densities in the order of 75 per cent such as the well-known and broadly used self-lubricating bearings.

Parts having densities ranging from 80 per cent to 95 per cent such as those used in structural applications.

Infiltrated parts having practically 100 per cent density when finished; such parts are also used largely in structural applications.

Parts made from ferrous powders are iron, copper-infiltrated iron, steel and stainless steel compositions.

The technique of making metallic products from metal powders is applied to three different areas of application, depending on certain factors as follows:

As a method of manufacturing machine parts or structural parts that can also be made by the conventional methods of casting, forging, cutting from metals etc., but for which the powder metallurgy technique is used because of its minimum loss of materials and, in some cases, its lower cost of production.

For the manufacture of special materials with unusual properties that cannot be achieved by any other metallurgical method, often because the component metals are immiscible and therefore cannot be alloyed in the molten state.

As a research tool for investigating solid state reactions and phenomena.

The second category is perhaps the most important for consideration since it deals with some special materials (combinations of metals and non-metals) which cannot be fabricated by any other method than by powder metallurgy techniques. (From “Metallurgy and Plastics for Engineers” by Merle O.Nutt)

Task 3.

Give the opposite meaning to the following words:

ferrous			minimum
unusual			immiscible
metal			alloyed
low			similar
often			impossible

Task 4.

Match the following words with their translation:

1. advantages	a) недоліки
2. impurities	b) чисті порошки
3. forging	c) підшипники
4. powders	d) переваги
5. disadvantages	e) середовище
6. density	f) домішки
7. atmosphere	g) густина
8. bearings	h) ковка

Task 5.

Match the following words and translate them into Ukrainian:

to produce to use to obtain to regulate to sinter to be made from to be applied to be alloyed to deal with		the dimensions and structure some special materials to different areas sintered materials with less impurities materials pure powders in a protective atmosphere ferrous powders in the molten state
Task 6.	Give missing forms of comparison for the following words:

hard
		higher
		less
		better
		easier
				the most important

Task 7.

Translate into Ukrainian the following words and word combinations:

possibility of obtaining, higher technico-economical characteristics, pure powders, sintered materials, impurities, the same composition and density, to regulate the dimensions and structure, grain interlocation, disadvantages, limitations, protective atmosphere, self-lubricating bearings, structural applications, infiltrated parts, conventional methods, forging, immiscible.

Task 8

Make up word combinations by finding in the box the endings to the following words and translate them into Ukrainian:

1. infiltrated ..., 2. stainless ..., 3. sintered ..., 4. protective ..., 5. powder ...,

6. molten …, 7. conventional ..., 8. pure ..., 9. self -lubricating..., 10. structural ... .

a) state, b) powders, c) parts, d) applications, e) materials, f) methods, g) steel, h) metallurgy, i) atmosphere, j) bearings

Task 9. Make up word combinations from the following words:

		1. infiltrated	a) interlocation
		2. pure	b) applications
		3. high	c) atmosphere
		4. grain	d) cost
		5. protective	e) bearings
		6. sintered	f) parts
		7. self-lubricating	g) materials
		8. structural	h) powders
Task 10.	Fill in the table with the information from the text above.

Advantages and Disadvantages of PM
Advantages of PM
Disadvantages of PM

Task 11.

Decide whether the following phrases characterize advantages or disadvantages of powder metallurgy. Prove your thoughts with some arguments.

higher technico-economical characteristics, applying pure powders, less impurities, better properties, high cost of powders, minimum loss of materials, lower cost of production, sintering in a protective atmosphere, immiscible components.

Task 12.

Speak on the topic “Powder metallurgy”. Such information should be included:

• Definition of powder metallurgy;

• Methods of powder production;

• Description of forming;

• Sintering;

• Advantages and disadvantages of PM;

• Metal powder products.

UNIT 9

FUELS IN METALLURGY

Task 1.

Discuss in your group and present in a few words these questions:

1. What melting units do you know?

2. What fuels are used for this or that unit?

Task 2.

Read the following text and find English equivalents to the following words and word combinations:

доменна піч, кокс, гаряче дуття, пилоподібне вугілля, подрібнювати та переміщувати, зв’язана вологість, затвердіння, торф, рослинні залишки, болото, коріння, крохмаль, кутикули, пилок, грибки, мікроелементи, мох, осока, різноманіття, очерет, змінювати, піддавати (дії), захоронення.