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3. Complete the following sentences:
A characteristic feature of fusion welding is:
a) molten metal b) low-voltage discharge c) inert atmosphere 48
Furnace heating is usually employed in
a) friction joining b) diffusion bonding c) ultrasonic joining
The consumable electrode is made
a) negative b) positive c) neither
Total energy input in all welding processes is
a) is greater than required to produce a joint b) is smaller than required
to produce a joint c) equals to required to produce a joint
Reactions of most metals with the atmosphere or other nearby metals can
1) improve the properties of a welded joint b) make the properties of a
welded joint worse c) never influence the properties of a welded joint
The most common gas used in gas-shielded metal-arc and gas-shielded
Tungsten-arc welding is
a) argon b) oxygen c) carbon dioxide
If not controlled, residual stress results in
a) precipitation processes in welded structures, b) freezing of the weldmetal c) bowing or distortion of the weldment
True or false?
1. There is always a welding pool in solid-phase welding processes.
2. Total energy input in all welding processes is greater than needed to
produce a weld.
3. Reactions of metals with the atmosphere or other nearby metals are
favorable to the properties of a welded joint.
4. Fluxes and inert atmospheres play a protective role and prevent oxidation.
5. The heat-affected zone is a region with unaltered properties.
6. Residual stress is present in all welded structures.
Answer the following questions:
1. What is a weld?
2. How can the heat be supplied for welding?
3. Is pressure employed in solid-phase processes?
4. What does an arc column consist of?
5. How is heat applied during welding?
6. What is the role of inert atmospheres?
7. What can make a joint brittle while welding?
8. What does the weld metal comprise in arc welding?
9. What is the base metal influenced by?
10. How can residual stress in welded structures be controlled?
***
Сварочное оборудование
"WELDING PROCESSES & EQUIPMENT"
(сварочное оборудование)
Read and remember:
You already know what kind of training you should go through to become
welder. Among other things, a welder should know about processes which
are similar to welding. Look through the vocabulary and the text below and
say what the main difference between welding and related metal joining
processes is.
WELDING PROCESSES & EQUIPMENT
Lead-in
You already know what kind of training you should go through to become
welder. Among other things, a welder should know about processes which
are similar to welding. Look through the vocabulary and the text below and
say what the main difference between welding and related metal joining
processes is.
Vocabulary
soldering пайка; пайка мягким (легкоплавким) припоем
tinning лужение; облуживание
leading свинцевание
brazing 1) пайка твердым припоем (из меди и цинка) 2)
покрытие медью
sweat паять, запаивать, припаивать (in, on)
gimmick 1) сложное приспособление Syn: gadget 2) а) прием,
трюк, уловка, ухищрение, хитрость
filler metal присадочный металл, присадка
filler rod присадочный пруток; присадочная проволока
heat buildup теплообразование, тепловведение
heat distortion деформация (материала) из-за теплового нагрева
stitch welding прерывистая шовная сварка; точечная сварка
перекрывающимися точками; автоматическая
точечная сварка
Reading
Text 1. Introduction to Welding Processes & Equipment
Among the first things a new welder needs to understand, is what the
different kinds of welding processes and equipment are, and their application.
A quick rundown:
Terms:
Soldering: Bonding by melting a soft metal to the surface of pieces to be
joined. Low temperature. Good for joining dissimilar materials. Most
common solders are lead-tin alloys.
Tinning: A soldering process, where the surface of a metal is coated with
solder.
Leading: A form of soldering, solder is used to fill in the surface of metal.
Brazing: Similar to soldering, but uses a higher temperature to fuse the filler
metal to the work pieces. Stronger bond. (Includes "Silver Soldering") Work
heated to pre-melt temperatures.
Welding: Joining 2 similar work pieces by melting them together, usually
with an additional filler rod of some sort to take up space. Materials must be
similar.
Cutting: Work is heated to melting point and beyond, and "cut" by oxidizing
metal. (Literally burning it away).
Shield: A barrier to keep oxygen away from heated work to prevent
oxidation. Includes chemical coatings called flux (liquids, pastes, solids,
which may be vaporized into a barrier gas when heated), and inert gasses.
Oxidation of the surfaces will prevent proper bonding of the metals.
Gas Welding
Uses Flame from burning gas to create welding heat.
Propane torch: (Soldering, heating) Good for sweating pipes, starting fires,
and spending hours trying to heat frozen bolts, while the surrounding metal
gets just as hot.
Oxyacetylene torch: (Cutting, welding, brazing, soldering, leading) Most
universal and useful welding tool. (Uses Acetylene gas and Oxygen for hot
flame) With the right bits, rod, and technique, you can weld almost anything.
Good for cutting anything from sheet metal to the turret off a tank, lead
filling, brazing (a sort of hard soldering process) welding plate, welding sheet
metal, welding aluminium, heating frozen bolts, or alternately cutting them
off, drilling holes in plate, welding cast iron, shrinking and forming steel, and
can double as a flame thrower in a pinch. Drawbacks are: Overheating of
some types of work, harder to control quality of some processes.
Oxy-propane: (Soldering, brazing, heating) A cheap compromise between
low cost and portable propane, and Oxy-Acetylene. Better than the former,
not as good as the latter.
Arc welding
Uses an electric arc to create welding heat.
Basic AC & DC arc welders (AC is cheaper) Uses flux coated steel (or
other) rods of various types for different jobs. Makes some of the best welds
on heavy gauge steels and cast iron. Cutting rods can make clean holes
through thick stock, and are about the only thing which can cut Kryptonite
bike locks. Very difficult to weld thin metals. You can also get a carbon arc
torch to use on an arc welder to braze. Eastwood's "stitch" welder is a
gimmick used on an arc welder to buzz the rod in and out, which may help on
thinner stock. (learning how to weld better, or going to a different process is
usually a better idea.)
MIG (Metal Inert Gas): A DC arc welding process which uses filler metal
fed in the form of a spool of thin wire, shielded by flow of inert gas (He,
Argon) instead of flux used in Arc. Very fast, much easier than Arc Welding,
with less heat buildup. Very good for sheet metal, due to minimal heat
distortion. Harder to weld thick stock, as welds are weaker due to poorer
penetration. The modern choice for steel body work, it can also be used for
Aluminium with Argon as the shield gas.
TIG (Tungsten Inert Gas): A high frequency AC arc process which uses a
tungsten electrode shielded by an inert gas to create a fine, controllable torch.
Uses a separate filler rod, as in Oxy-Acetylene welding. Capable of welding
very thin metals. About the best process for Aluminium, Stainless steel, and
other exotic stuff.
Resistance welding: includes spot welding: Uses the heat generated by
electricity flowing through work to melt and fuse. i.e.- put an electrode on
either side of 2 overlapped sheets of steel, turn on power. Metal in between
heats up, and melts together. An old favorite for assembling car bodies.
Plasma Cutters: Not a welder, but related. A high voltage arc is used to
superheat and ionize a stream of air to the "plasma" state. The stream of
plasma makes a rapid, clean, narrow cut with minimal heating of the work
piece.
After-reading activity
Answer the following questions:
1. What is the main difference between soldering and brazing?
2. What is used by welders to prevent oxidation?
3. What makes soldering advantageous before welding?
4. What welding processes are suitable for welding thin/thick metal plates?
5. What makes plasma cutting better than gas cutting?
Vocabulary
coalescence соединение, слипание; сращение
filler material присадочный материал
molten pool ванна расплавленного металла, сварочная ванна
gas flame газовое пламя
solid-phase твёрдая фаза
ultrasonic ультразвуковой
friction трение
furnace печь
diffusion 1) рассеивание
2) диффузия
high-current сильноточный
low-voltage низковольтный, низкого напряжения
discharge разряд
arc column столб дуги
direct current (dc) постоянный ток
alternating current переменный ток
layer слой; пласт; ряд
molten-metal капля жидкого металла
droplet
flux флюс
inert atmosphere инертная среда
annulus тех. узкое кольцо (зазор и т. п.)
torch сварочная горелка (для автоматической сварки –головка)
base metal основной металл
grain зерно
precipitation осаждение
residual stress остаточное напряжение
Find the English equivalents for the following words and word combinations:
источник тепла, расплавленный металл, необходимый размер, сварной
шов, не нагретый металл, механические свойства, максимум
температуры, защищать поверхности, быстрое охлаждение,
осуществлять контроль, препятствовать окислению, вступать в
химическую реакцию, термообработка, бомбардировка электронами,
зона термического [теплового] воздействия, общая потребляемая
энергия
***
Понятие о пайке. Виды пайки
1. Read the following Text:
Soldering
1. Soldering is employed when liquid tight joints are required. 2. They have comparatively low mechanical strength. 3. The tensile strength of a soldered seam may be from 3 to 10 kg per sq. cm. 4. The tensile strength of brazed joints is much higher (form 31 to 44 kg per sq. cm). 5. Metals may be soldered by means of a hand type soldering iron, a blowtorch and other methods. 6. Soldering iron may be plain, gas or electric. 7. Metals may be dipped in molten solder. 8. Sometimes the brazing and soldering of metals may use mechanized and automatic equipment. 9. Mechanized and automatic brazing methods include resistance brazing, arc brazing and others. 10. The selection of a mechanized brazing method should be based on the type of filler metal, weak material, size, of joined components.
Дата: 2019-02-25, просмотров: 500.