- •Unit 5: Metalworking and welding
- •1. Read the text and say what the main metalworking processes are:
- •3. Match the terms with their right definitions.
- •4. Answer the following questions.
- •5. Translate the following sentences from Ukrainian into English using active vocabulary and information from the text to the subject.
- •1. Read the text and say what metal cutting is.
- •4. Find out whether the following statements are true or false.
- •6. Answer the following questions to the text.
- •1. Read the text and say why welding is widely used nowadays.
- •3. Answer the following questions to the text.
- •4. Translate the following sentences from Ukrainian into English.
- •1) Metalworking and metal properties
- •I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.
- •III. Answer the following questions.
- •2) Factors affecting machinability
- •I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.
- •II. Answer the following questions.
- •3) Metal-Cutting Machines. Lathe
- •I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.
- •II. Define whether the following statements are true or false.
- •III. Fill in the following scheme using the text.
- •4) Borys Paton
- •I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.
- •III. Give a short summary of the text in English in written or oral form.
- •1. Choose the right variant.
- •2. Change the words in brackets from Ukrainian into English.
- •3. Fill in the right word into the sentences.
- •4. Make up word-combinations with the following words. Translate them into Ukrainian.
I. Copy the underlined words and word-combinations, translate them into Ukrainian and learn them.
II. Find the following words and word-combinations in English in the text: важлива особливість гарячої обробки; покращення механічних властивостей металлу; напрям максимальної напруги; здатність металу чинити опір; проявляти більше деформаційне зміцнення; внутрішні дефекти в металі; неметалеві складові; належні виробничі технологічні процеси; зміна форми.
III. Answer the following questions.
1. What process improves the mechanical properties of metals?
2. What new properties have hot-worked products?
3. How does the forging of a bar affect the grains of the metal? What is the result of this?
4. How are the flow lines in the forged metal oriented and how does it affect the strength of the forged part?
5. What are the best strain-hardening alloys? Where can we use them?
6. What are the inner flaws in the metal?
7. Can a metal fracture because of the inner flaw?
8. What limits the change of the shape during forming operations?
2) Factors affecting machinability
Machinability is generally assumed to be a function of tool edge life. The main factors which influence the behaviour, and thus the life of the edge of a cutting tool, are:
- the mechanical, characteristics of the material being machined, such as its strength, hardness and metallurgical structure;
- the state of the casting, involving the skin finish, critical dimensions, machining allowances, slag inclusions, the presence of scabs, rust, dirt, etc.;
- the nature of the machining techniques being used;
- the characteristics of the machine-tool being used, such аs machine efficiency, available power, and the rigidity of the setup.
Other factors aside, it is primarily the structure of the metal which determines its resistance to the cutting action of the tool, i. e. the potential rate of metal removal, and the resulting abrasion on the tool, i. e. the life of the cutting edge.
Structure, strength and machinability are interrelated to some extent – in general, increased strength implies reduced machinability. This basic relationship must be understood, otherwise difficulties may be experienced in the machine shop if the designer has specified a material with a higher strength than is necessary. Nevertheless, care should be taken in rating machihabity on the basis of strength. For example, nodular irons are normallу considerably stronger than flake-graphite types, but are likely to be easier to machine. It is therefore recommended that structure, rather than strength, be adopted as the basis for machining practice.
Hardness provides a more reliable guide to machinability than does strength, for hardness depends mainly on the matrix structure of the casting. Again, however, the relation is of a general nature only, for it is possible to have a metal which exhibits low hardness value, but which has a very abrasive action on the cutting tool. For example, the presence of hard phosphide particles embedded in a soft, ferric matrix reduces tool life considerably.