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Fill in prepositions if necessary.
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1. The focused laser beam has the highest energy concentration _______any known source_______energy.
2. The end surfaces of the ruby rod were ground flat and parallel and were polished______extreme smoothness.
3. The laser can be compared_______solar light beam for welding.
4. The laser can be used_______air.
5. The laser can operate_______considerable distance_______ the work piece.
6. The beam penetrates_______the metal vapor and melts the metal below.
7. It was found that once the metal is raised_______its melting temperature the surface conditions have little or no effect.
8. The power density_______the electron beam is only slightly greater.
9. Heating and cooling rates are much higher_______laser beam welding than in arc welding.
10. Rapid cooling rates can create problems such as cracking_______high carbon steels.
Give the summary of the text.
What parts of speech do the following words belong to? Translate these words into Russian.
Process, application, surface, focus, highest, project, early, crystal, extreme, vapor, melt, below, original, density, create, same.
Translate the following words paying attention to their suffixes.
Concentration, concentrated, producing, production, smoothness, considerable, consideration, differential, difference, different.
Translate the following groups of words.
Quality parameters, quality criteria, quality deviations, quality control system, required welding energy, constant quality, solar light beam, melting temperature, carbon steels, stainless steel.
Read and translate the text.
Text B
Improved Quality Through Ultrasonic Metal Welding
Height-volume production requires the strict adherence to predetermined quality parameters. This implies not only exact machine operation based on preset data, but also a simultaneous quality check of the weld against previously determined quality criteria. Ultrasonic metal welding offers the best prerequisites for optimum quality control as there are only a few specific process parameters which are easily measurable and thus controllable. Quality deviations are identified and usually offset during the welding process, i.e. they are adjusted.
Reasons for quality variations
Quality deviations may occur, for example, when workpieces have different dimensions, when the material quality (batches) differs and when contamination is excessive. A wrong insertion of the workpiece by the operator can also be identified by a quality control system.
Quality influences and quality parameters
The first task is to monitor the set machine data whereby welding pressure and amplitude are proportional in size to the supplied generator power output. Multiplying the power output with the welding time gives the required welding energy.
Welding in the energy mode
Welding in energy mode, i.e. with a constant energy setting, is known from ultrasonic plastics welding and can also be used for ultrasonic metal welding. To achieve a constant quality the welding time is automatically adjusted. Although this type of quality control is good with ultrasonic plastics welding, the approach has to be more carefully applied when it comes to ultrasonic metal welding.
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Control of welding energy is not always sufficient
Contact-free probe to determine the degree of compression
Considering that were applications which require only minimum welding energy, the total of all system-caused losses amounts to some 80% of the total necessary welding energy (leaving 20% effective welding energy), it becomes evident that small modifications in the workpieces to be welded require only a minor adjustment to the welding energy. The control of the welding energy in respect of welding time does not take into account possible insufficiencies and variations of the machine components.
The tolerances are even higher when the workpieces to be welded are of different quality and have different service conditions.
All these varying influences can have a considerable effect on the welding quality.
Mechanical compression as a quality parameter
As the parts to be welded may deform during the welding process, the mechanical compression of the parts after they have been welded together may constitute an important quality measure. Contact-free measuring devices in the welding equipment determined the degree of compression by measuring the movement (stroke) of the welding tools during the process. The starting point of this stroke is the position of the sonotrode under pressure before the ultrasonic is triggered.
SUPPLEMENTARY READING
Text 1
Soldering
Soldering is a method of using a filler metal (commonly known as solder) for joining two metals without heating them to their melting points. Soldering is valuable because it is a simple and fast means for joining sheet metal, making electrical connections, and sealing seams against leakage. Additionally, it is used to join iron, nickel, lead, tin, copper, zinc, aluminum, and many other alloys.
Soldering is not classified as a welding or brazing process, because the melting temperature of solder is below 800°F. Welding and brazing usually take place above 800°F. The one exception is lead welding that occurs at 621°F. Do not confuse the process of SILVER SOLDERING with soldering, for this process is actually a form of brazing, because the temperature used is above 800°F
This lesson describes the following:
· Equipment and materials required for soldering
· Basic methods used to make soldered joints
· Special techniques required to solder aluminum alloys
Equipment
Soldering requires very little equipment. For most soldering jobs, you only need a heat source, a soldering copper or iron, solder, and flux.
Sources of Heat
The sources of heat used for soldering vary according to the method used and the equipment available. Welding torches, blowtorches, forges, and furnaces are some of the sources of heat used. Normally, these heating devices are used to heat the soldering coppers that supply the heat to the metal surfaces and thus melt the solder. Sometimes, the heating devices are used to heat the metal directly. When this is done, you must be careful to prevent heat damage to the metal and the surrounding material.
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Soldering Coppers
A soldering copper (usually called a soldering iron) consists of a forged copper head and an iron rod with a handle.
The handle, which may be wood or fiber, is either forced or screwed onto the rod. Soldering heads are available in various shapes.
Figure 6-2 shows three of the more commonly used types. The pointed copper is for general soldering work The stub copper is used for soldering flat seams that need a considerable amount of heat. The bottom copper is used for soldering seams that are hard to reach, such as those found in pails, pans, trays, and other similar objects.
Nonelectrical coppers are supplied in pairs. This is done so one copper can be used as the other is being heated. The size designation of coppers refers to the weight (in pounds) of TWO copperheads; thus a refer-ence to a pair of 4-pound coppers means that each copper head weighs 2 pounds. Pairs of coppers are usually supplied in 1-pound, 1 1/2-pound, 3-pound, 4-pound, and 6-pound sizes. Heavy coppers are de-signed for soldering heavy gauge metals, and light cop-pers are for thinner metals. Using the incorrect size of copper usually results in either poorly soldered joints or overheating.
Text 2
Soldering Aluminum Alloys
Soldering aluminum alloys is more difficult than soldering many other metals. The difficult y arises primarily from the layer of oxide that always covers aluminum alloys. The thickness of the layer depends on the type of alloy and the exposure conditions.
Using the proper techniques, many of the aluminum alloys can be successfully soldered. Wrought aluminum alloys are usually easier to solder than cast aluminum alloys. Heat-treated aluminum alloys are extremely dif-ficult to solder, as are aluminum alloys containing more than 1% magnesium.
The solders used for aluminum alloys are usually tin-zinc or tin-cadmium alloys. They are generally called ALUMINUM SOLDERS. Most of these solders have higher melting points than the tin-lead solders used for ordinary soldering. Corrosive and noncorrosive fluxes are used for soldering aluminum.
The first step in soldering aluminum is to clean the surfaces and remove the layer of oxide. If a thick layer of oxide is present, you should remove the main part of it mechanically by filing, scraping, sanding, or wire brushing. A thin layer of oxide can often be removed by using a corrosive flux. Remember, remove any residual flux from the joint after the soldering is finished.
After cleaning and fluxing the surfaces, you should tin the surfaces with aluminum solder. Apply flux to the work surfaces and to the solder. You can tin the surfaces with a soldering copper or with a torch. If you use a torch, do not apply heat directly to the work surfaces, to the solder, or to the flux. Instead, play the torch on a nearby part of the work and let the heat conduct through the metal to the work area. Do not use more heat than is necessary to melt the solder and tin the surfaces. Work the aluminum solder well into the surfaces. After tinning the surfaces, the parts may be sweated together.
Another procedure you can use for soldering alumi-num alloys is to tin the surfaces with an aluminum solder and then use a regular tin-lead solder to join the tinned surfaces. This procedure can be used when the shape of the parts prevents the use of the sweating method or demands a large amount of solder. When using tin-lead solder with aluminum solder, you do not have to use flux.
After soldering is complete, you should clean the joints with a wire brush, soap and water, or emery cloth. Ensure that you remove all the flux from the joint since any flux left will cause corrosion.
Text 3
Application Technology
Ultrasonic metal welding is a proven technology, especially when workpieces need to be bonded on a permanent basis without consuming significant heat. Since no fusion takes place, the process is also applicable for welding materials with different melting points.
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Reasons for ultrasonic metal welding
When it comes to selecting this technology, the following advantages should also be considered:
· there is no coarse grain formation and thus no embrittlement of the parts
· mechanical stability and resistance to corrosion remained constant
· an excellent electric conductivity is guaranteed
· no welding consumables are required
· special ambient conditions (i.e. vacuum) are not necessary
· negligible electric power is consumed in comparison to other welding processes
Materials suitable for ultrasonic welding
The materials which a most suitable for ultrasonic metal welding are nonferrous metals and their alloys of any combination. Therefore, applications that involved bonding materials such as copper, aluminum and brass are very common. Materials such as lead, zinc and tin cannot be welded due their high lubricity. The oscillations during ultrasonic welding would only lead to smoothing of the bonding area, not to bonding of the molecules. Even coatings which contain these materials are troublesome and will at the very least will lead to variations in the quality of the weld.
As previously described, the part facing the sonotrode is accelerated and decelerated under pressure using high frequencies. As the available energy for generators with up to approximately 4 kW is limited, the size or the mass of the part to be welded has to be considered. As a general rule parts up to max. 10 grams can be welded. This value can be exceeded if the material is relatively soft so that the material deformation in the welding area is absorbed. The part which faces the anvil, i.e. away from the sonotrode, can be of any weight.
In order to introduce the energy more efficiently and consistently and to better accommodate the parts to be welded, design modifications may be required. For weldings which require a large surface bond, the use of one or several energy directors (welding studs) is recommended.
If the parts to be welded have an unfavorable shape, the oscillation energy can continue to flow inside the workpiece itself and produce a nodal point (wave) which may lead to distortion or even break the part in this area. During the design phase, the shape of the parts has to be studied in this context by conducting welding tests.
If a design change at this stage is not possible, the remedy could be a slight modification of the welding fixture and the anvil. As an alternative, the parts can be specially clamped in certain areas and the energy concentrated in local areas.
When several spots-weldings are carried out on one part, nodal points may form in places where they are undesirable. This requires proper countermeasures to be taken, if necessary.
In order to obtain a constant weld quality it is important to have a uniform surface. Slight contamination is usually acceptable, but heavily oiled, greased or oxidized parts impair the welding process to such an extent that the previously defined amount of energy cannot be introduced into the process, even if the welding time is increased.
Coated surfaces are likewise to be evaluated to determine their suitability for welding. Nickel-plating, silver-coating, copper-coating or aluminum-plating often have a positive effect. Negative effects are known from tin-plating, zinc-coating and from chromium-plated surfaces. On the other hand, materials which are less suitable for ultrasonic metal welding can obtain good welding qualities by applying a suitable surface layer (for example, the application of a nickel or galvanized copper layer on steel).
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A major area of application for ultrasonic metal welding is the bonding of enamel copper wires such as those used for coils, transformers, etc. Based on today's technology, good quality, pipeless and homogeneous welds without having to first strip the enamel are rare. The decisive factor here is the quality of the enamel as well as its proportion to the total weld.
Ultrasonic metal welding is already widely used in industry. This means that there is significant application experience in this field. The most important factor is the weldability of the materials and their alloy components as well as the shape of the parts.
When carrying out welding tests with the help of proper lab tools, the quality of the tested welds can be ascertained. In addition, the experience gained is also the basis for the design and construction of welding tools as well as for possible material or design changes. This makes the applications test a vital prerequisite if ultrasonic welding equipment is to produce reliable quality.
Text 4
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