As a non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and produced a high-quality weld. However, the rate of welding is considerably slower than in other processes.
Shielded metal are welding
In shielded metal-arc welding, a metallic electrode, which conducts electricity, is coated with flux and connected to the other and of the same source of current. An electric arc is formed by touching the tip of the electrode to the metal and then drawing it away. The intense heat of the arc melts both parts to be welded and the point of the metal electrode, which supplies filler metal for the weld. This process is used mainly for welding steels.
Gas-metal are welding
In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.
Submerged are welding
Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electro slag welding. It is very efficient but can be used only with steels.
Additional vocabulary:
gas-tungsten welding – сварка оплавлением вольфрамовым электродом в среде инертного
газа
inert – инертный
bare – голый
rate – скорость
gas-metal arc – аргонодуговая сварка
surrounding – окружающий
liquid – жидкость, жидкий
droplet – капелька
carbon dioxide – углекислый газ
beneath – под, ноже, внизу
layer – слой
weld seam – сварной шов
semi-automatic – полуавтоматическая
to submerge – погружать
Answer the questions:
- What is the difference between the arc welding and non-consumable electrode arc welding?
- What are the disadvantages of the non-consumable electrode arc welding?
- How is electrode protected from the air in gas-metal arc welding?
- What is submerged arc welding?
- What is the principle of resistance welding?
- Where is semi-automatic welding employed?
Translate into English:
- вольфрамовый электрод
- инертный газ
- окисление
- высококачественный сварочный шов
- скорость сварки
- аргон, гелий, углекислый газ
- жидкий металл
- слой плавкого металла в виде гранул
- листовой металл
- полуавтоматические сварочные станки
Translate into Russian:
- In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current.
- The heat from the arc melts the edges of the metal.
- A bare electrode is shielded from the arc by surrounding it with argon or carbon dioxide gas.
- Submerged-arc welding is similar to gas-metal arc welding.
- Electrodes are clamped on each side of the parts to be welded.
- Resistance causes heat, which melts the metals and creates the weld.
THEME 4
Machine Tools
Vocabulary:
workpiece – обрабатываемая деталь, изделие
facility – приспособление
to allow – позволять, разрешать
relative – относительно
to lubricate – смазывать
fasten – прикреплять, привязывать, застегивать
(to) screw – винт, привинчивать, навинчивать
thread – нить, резьба, нарезка
discharge – электр. разряд
(to) feed (fed, fed) – подавать, подача
lathe – токарный станок
range – ассортимент, диапазон
flexible – гибкий, гнущийся, эластичный
sharp – острый
friction – трение
outside – наружный, внешний, снаружи
inside – внутри, внутренний
to remove – удалять, перемещать
to mount – крепить, закреплять
to require – нуждаться, требовать
to enable – дать возможность, позволять
tolerance – допуск
close tolerance – жесткий допуск
wheel – колесо, круг
Text 1.
MACHINE-TOOLS
Machine-tools are used to shape metals and other materials. The material to be shaped is called the workpiece. Most machine-tools are now electrically driven. Machine-tools with electrical drive are faster and more accurate than tools: they are an important element in the development of mass-production processes, as they allowed individual parts to be made in large numbers so as to be interchangeable.
All machine-tools have facilities for holding both the workpiece and the tool, and for accurately controlling the movement of the cutting tool relatively to the workpiece. Most machining operations generate large amounts of heat, and cooling fluids (usually a mixture of water and oils) must be used for cooling and lubrication.
Machine-tools usually work materials mechanically but other machining methods have been developed lately. They include chemical machining, spark erosion to machine very hard materials to any shape by means of a continuous high-voltage spark (discharge) between an electrode and a workpiece. Other machining methods include drilling using ultrasound, and cutting by means of a laser beam. Numerical control of machine-tools and flexible manufacturing systems have made it possible for complete system of machine-tools to be used flexibly for the manufacture of a range of products.
Additional vocabulary:
machine-tools – станки
electrically driven – с электроприводом
fluid – жидкость
spark erosion – электроискровая обработка
by means of – посредством
beam – луч
drilling – сверление
Fill in blanks with the proper words:
- Machine-tools are used to shape … and other materials.
- All machine-tools have... for holding both the workpiece and the tool, and for accurately controlling the movement of the cutting tool relatively to the workpiece.
- Most machining operations generate large amounts of heat, and cooling … (usually a mixture of water and oils) must be used for cooling and lubrication.
- Machine-tools usually work materials … but other machining methods have been developed lately.
- Other machining methods include … using ultrasound, and cutting by means of a laser beam.
Complete the following sentences:
- The material to be shaped is called…
- Machine-tools with electrical drive are faster and more…
- Most machining operations generate large amounts of heat, and cooling…
- They include chemical machining, spark erosion…
- Numerical control of machine-tools and flexible manufacturing systems have made it possible for…
Text 2.
LATHE
Lathe is still the most important machine-tool. It produces parts of circular cross-section by turning the workpiece on its axis and cutting its surface with a sharp stationary tool may be moved sideways to produce a cylindrical part and moved towards the workpiece to control the depth of cut. Nowadays all lathes are power-driven by electric motors. That allows continuous rotation of the workpiece at a variety of speeds. The modern lathe is driven by means of a headstock supporting a hollow spindle on accurate bearings and carrying either a chuck or a faceplate, to which the workpiece is clamped. The movement of the tool, both along the lathe bed and at right angle to it, can be accurately controlled, so enabling a part to be machined to close tolerances. Modern lathes are often under numerical control.
Additional vocabulary:
circular cross-section – круглое поперечное сечение
stationary – неподвижный, стационарный
sideways – в сторону
spindle – шпиндель
variety – разнообразие, разновидность
headstock – передняя бабка
chuck – зажим, патрон
faceplate – планшайба
lathe bed – станина станка
numerical control – числовое управление
Answer the questions:
- What are machine-tools used for?
- How are most machine-tools driven nowadays?
- What facilities have all machine-tools?
- How are the cutting tool and the workpiece cooled during machining?
- What other machining methods have been developed lately?
- What systems are used now for the manufacture of a range of products without the use of manual labour?
- What parts can be made with lathes?
- How can the cutting tool be moved on a lathe?
- How is the workpiece clamped in a lathe?
- Can we change the speeds of workpiece rotation in a lathe?
- What is numerical control of machine tools used for?
Find English equivalents in the text:
- отработанный материал
- электропривод
- более точный
- отдельные детали
- процесс массового производства
- приспособления для удержания резца и детали
- операции по механической обработке детали
- высоковольтный разряд
- сверление ультразвуком
- резание с помощью лазерного луча
- гибкие производственные системы
- детали круглого сечения
- поворачивать деталь вокруг ее оси
- двигать в сторону, двигать по направлению к детали
- глубина резания
- непрерывное вращение детали
- движение резца вдоль станины
Translate into English:
- Токарный станок позволяет производить детали круглого сечения.
- Деталь зажимается в патроне или на планшайбе токарного станка.
- Резец может двигаться как вдоль станины, так и под прямым углом к ней.
- Современные токарные станки часто имеют цифровое управление.
Text 3.
MILLING MACHINE
In a milling machine the cutter (фреза) is a circular device with series of cutting edges on its circumference. The workpiece is mounted (fastened) on a table has that controls the feed against the cutter. The table has three possible movements: longitudinal, horizontal, and vertical; in some cases it can also rotate. Milling machines are the most versatile of all machine tools. Flat or contoured surfaces (фасонная поверхность) may be machined with excellent finish and accuracy. Angles, slots, gear teeth and cuts can be made by using various shapes of cutters.