METAL CASTING

After metal has been melted, it is poured into a mold and allowed to cool. To remove the mold, sand castings enter a process called shakeout where the sand mold is shaken from the metal piece. During the process dust and smoke are collected by dust control equipment. Permanent molds are pried from the metal pieces without being destroyed. Investment molds and shell molds are destroyed during removal, creating solid waste.

Any additional parts used to hold the piece during casting are removed. The metal piece is cleaned using steel shot, grit or other mechanical cleaners to remove any remaining casting sand, metal flash or oxide.

A surface coating may be applied to the metal piece at the foundry; however, such coating is usually done at metal finishing plants.

The first step in metal casting involves the creation of a mold into which the molten metal will be poured and cooled. The materials used to make the molds depend on the type of metal being cast and the desired shape of the final product. Sand is the most common molding material; however, metals, investment materials, and other compounds may also be used.

Green sand mold are used in 85% of foundries. Green sand is a mixture of sand, clay, carbonaceous material and water. The sand provides the structure for the mold, the clay binds the sand together and the carbonaceous materials prevent rust. Water is used to activate the clay. The green sand mixture is packed around a pattern of the metal piece and allowed to harden. The mold is carefully removed from the pattern and prepared for the molten metal.

Sand molds are used only once. Molten metal is poured into the mold and allowed to cool. After cooling, the mold is broken away from the metal piece in a process called shakeout. Most of the sand from green sand molds is reused to make future molds.

Sand mixtures are also often used to create cores. Cores are pieces that fit into the mold to create detailed internal passages in the metal piece. Cores must be strong and hard to withstand the molten metal, and collapsible so they can be removed from the metal piece after it has cooled. To obtain these properties, resins or chemical binders are usually added to sand mixtures. Depending on the binder used, molds may be either air or thermally set.

Other molding materials include chemically bonded sand, metal or refractory. These materials are used in the remaining 15% of foundry applications. Shell molds use chemically bonded sand to make the molds. Permanent metal molds may be used in foundries that produce large quantities of the same piece. Investment molds are made from ceramic substances called refractory. They are used in high precision metal castings.

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

плавити, вимикати, лиття у піщані форми, пил, тверді відходи, стальний шрот, покриття, cтворення ливарної форми, ливарна форма з вологого піску, глина, вуглецевий матеріал, запобігати ржавінню, повторне використання піску, серцевина, витримувати розплавлений метал, використання, велика кількість, керамічна речовина.

3.Make up word combinations from the following words. Translate them into Ukrainian.

4.Make up sentences from the following words. Translate the sentences into Ukrainian.

1. Mixture, is, a carbonaceous, material, green, clay, sand, and, water, of, sand.

2. The green, mixture, sand, a pattern, the metal piece, is packed around, of, to harden, and, allowed.

3. Once, sand, only, molds, are, used.

4. Mixtures, sand, also, are, to create, often, cores, used.

5. Insert necessary modal verbs into the following sentences:

1. After metal has been melted, it _____ be poured into a mould.

2. During the process dust and smoke _____ be collected by dust control equipment.

3. Cores _____ be strong and hard to withstand the molten metal.

4. We _____ use this type of equipment in foundry production. It’s forbidden by law.

5. Molten metal _____ to be re-cooled.

6. Permanent metal moulds _____ be used in foundries that produce large quantities of the same piece.

7. Most of the sand from green sand molds _____ be reused to make future molds.

8. To obtain desired properties, resins or chemical binders _____ be added to sand mixtures.

6. Put the verbs in brackets in appropriate tense form.

1. After metal (to melt), it (to pour) into a mould.

2. Sand casting (to enter) a process called shakeout.

3. During the process dust and smoke (to collect) by dust control equipment.

4. Investment molds and shell moulds (to destroy) during removal.

5. A surface coating (to apply) to the metal piece at the foundry.

7. Transform the following sentences a) into Second Conditional, b) into Third Conditional. The first one has been done for you.

1. If the first step in metal casting involves the creation of a mold, the molten metal will be poured and cooled.

a) If the first step in metal casting involved the creation of a mold, the molten metal would be poured and cooled.

b) If the first step in metal casting had involved the creation of a mold, the molten metal would have been poured and cooled.

2. If sand is the most common molding material, it will be used in foundry processes.

3. If green sand molds are used in 85% of foundries, these molds will be the most important for us.

4. If the sand provides the structure for the mold, it will be used in foundry processes.

5. The carbonaceous materials will be used in foundry processes, if they prevent rust.

6. If the water is used to activate the clay it will be useful for this research.

7. If sand molds are used only once, they won’t be rather useful.

8. If most of the sand from green sand molds is reused, future molds will be made from this sand.

9. If cores are strong and hard to withstand the molten metal, they will be removed after the metal piece cooled.

10. If shell molds use chemically bonded sand, they will be used in our industry.

8. Answer the following questions:

1. What is done to remove the mold?

2. How is solid waste created?

3. How is the metal piece cleaned?

4. What can be remained on the metal piece?

5. Where can surface coating be applied?

6. What does the first step of metal casting involve?

7. What is the most common molding material?

8. What are the components of green sand?

9. What bind the sand together in the mold?

10. What types of molds do you know?

Section 2

1.Read and translate the following text:

Date: 2015-01-02; view: 1026