Методичка по сварке (778485), страница 6

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2.29 Scan the text and find the correct answers.

1. In which cases is square butt welding used? 2. Why are relatively small quantities of wire used in Single-V Groove welding with Root Face? 3. What kind of backing is recommended for Single-V Groove welding without Root Face? Prove your answer. 4. What kind of joint is used for two-pass submerged arc welds? 5. How can the flow of material through the gap be prevented when making a double-V butt joint? 6. Why should the finishing weld penetrate into and refuse the backing weld to a depth of 3/16 to 5/16-in when making a double-V butt joint?7. In which cases is double- U groove butt joint used?

2.30 Compare the types of butt joints.

2.31 Find in the texts the English equivalents for the following phrases.

1. поддерживается постоянным по всей длине шва; 2. обратная сторона соединения; 3. стремится стать чрезмерным для более толстых швов; 4. сравнительно небольшое количество проволоки; 5. т. к. это соединение часто используется; 6. не позволяет части подварочного шва осуществить полное проплавление; 7. т. к. нужное проплавление может быть достигнуто без разделки кромок; 8. зазор между свариваемыми кромками может быть допустим; 9. отношение толщины соединения к диаметру цилиндра; 10. чтобы обеспечить 100-процентное проплавление.

2.32 Group work. Describe main features of the types of welds shown in the pictures. You may simulate this process on your computer and demonstrate the results to your group-mates.

2.33 Make up a summary in English of the text “Groove Butt Joint Welds”.

Writing

2.34 Read the text and translate it in written form.

Overhead-Position Welding (1978п. зн.)

Overhead welding is the most difficult position in welding. Not only do you have to contend with the force of gravity but the majority of the time you also have to assume an awkward stance. Nevertheless, with practice it is possible to make welds equal to those made in the other positions.

To retain complete control of the molten puddle, use a very short arc and reduce the amperage as recommended. As in the vertical position of welding, gravity causes the molten metal to drop or sag from the plate. When too long an arc is held, the transfer of metal from the electrode to the base metal becomes increasingly difficult, and the chances of large globules of molten metal dropping from the electrode increase. When you routinely shorten and lengthen the arc, the dropping of molten metal can be prevented; however, you will defeat your purpose should you carry too large a pool of molten metal in the weld.

One of the problems encountered in overhead welding is the weight of the cable. To reduce arm and wrist fatigue, drape the cable over your shoulder when welding in the standing position. When sitting, place the cable over your knee. With experience, cable placement will become second nature.

Prepare the plates for overhead butt welding in the same manner as required for the flat position. The best results are obtained when backing strips are used; however, you must remember that you will not always be able to use a backing strip. When you bevel the plates with a featheredge and do not use a backing strip, the weld will repeatedly burn through unless extreme care is taken by the operator.

For overhead butt welding, bead welds are preferred over weave welds. Clean each bead and chip out the rough areas before placing the next pass. Make the first pass with the electrode held at 90 degrees to the plate. When you use an electrode that is too large, you can not hold a short arc in the root area. This results in insufficient root penetration and inferior joints.

From (http://64.78.42.182/sweethaven/BldgConst/Welding/lessonmain.asp?lesNum=7&modNum=7)

UNIT 3. Corner, Edge, Tee, and Lap Joints.

Warm up

3.1 Before reading the text try to answer the following questions:

1. Try to give the definition to comer joints as its name implies.

2. What are the angles between the plates to be welded?

3.2 Match the words in column A with the definitions in column В

А B

3.3 Brush up the following auxiliary words (due to, as well as, either... or, as) and fill in the following sentences with the proper one:

1. A butt joint may be ... square ... grooved. 2. Arc welding ... cutting produce intense sound. 3.... the name implies, a corner joint is used to connect two parts together to form a corner. 4. Copper backing in single V-groove butt joints is not recommended ... the tendency of the weld metal to fuse to the backing piece. 5. ... in the case with butt joints, the edges of the plates to be welded by corner joints may be machined prior to welding. 6. Because of ...the internal ...external slag-free nature of gas metal arc deposits, subsequent submerged arc welds of excellent quality can be produced. 1.... the relatively low area of the weld, .. .aesthetic appearance a corner joint weld may not be strong enough. 8. Plasma arc welding is used for metal spraying ... for cutting. 9....the high welding speeds, plasma arc welding is one of most efficient.

3.4 Read the text making use of the active terminological vocabulary to answer the following questions:

l. What makes the difference of corner joints? 2. What are the main types of corner joints? 3. How strong are the welds produced? 4. What is used to reinforce the weld? 5. Where is a flange joint applied?

Corner Joints (2850)

One of the major types of welding connection is the corner joint. As its name implies, this joint is used to connect two parts together to form a comer. This weld type is extremely useful and can be preformed with either a high or low energy density welder. There are a total of four common sub types of corner joint, each, as usual, having its own benefits and disadvantages.

The first common corner joint sub type is made by beveling both parts, usually at 45 degrees for a 90 degree joint, then placing the two faces together, and melting the outside edge. This is usually done with a low energy density welder but a high-energy density welder can be used. A weld bead may also be added to the inside of the comer to reinforce the weld. This weld is fairly fast and easy to create, but can have problems with strength due to the relatively low area of the weld, as well as aesthetic appearance.

The second type of comer joint is essentially a butt weld between two pieces that are perpendicular. This weld can be done with a low energy density welder if the parts are small enough, but is usually done with a high energy density beam. This allows deep penetration and can form a weld that is as strong as the base material. This advantage of strength is countered by the increased proneness of joints to deformation, as well as the increased difficulty and equipment cost of the weld. As in the case with normal butt joints, the edges may be machined prior to welding to improve fit, alignment or welding properties.

The third type of corner welds is the melt through weld. In this weld, the corner is assembled and the beam is used to melt through the top component and into the lower component. This type of weld works best when the top piece is relatively thin compared to the bottom piece, allowing it to be melted through with a minimal energy input. This type of welds is preformed exclusively with high energy density sources. This weld can be made easily without the need to precisely follow a joint, but it can be weak due to the very low cross sectional area of the weld. If necessary, multiple passes can be made if the bottom piece is sufficiently thick, improving the weld strength.

The final major type of comer joints is truly a flange joint. This is used for making corners in plates or foils that are too thin for the other types of welds. To make this type of joints a 90-degree flange is made in one of the components. This flange is then aligned to the other piece to be welded, and the welder is run over the edges of the two parts. This melts the edges together and forms the weld bead. This method can be used with either a high or low energy density source and is fast and reliable, but tends to make extremely weak joints due to the leverage and odd stress angles that the flange causes.

from: Joining Technologies | Newgate International Business Center (slightly

abridged)

3.5 Terminological vocabulary to the text “Corner Joints”. Try to memorize the following words and word combinations.

1. a corner joint - угловoе соединениe

2. a welder, n - сварочный агрегат

3. a melt through weld — сварной шов со сквозным проплавлением

4. an input, n - подводимая мощность

5. a flange [flAndG] joint - сварное соединение, выполненное по отбортовке

6. leverage [0lIv(Q)ridG], n- сила, усилие

7.an odd stress angle - необычный угол напряжения

8. proneness [0prQunnQs], n - подверженность чему-либо

9. a weld bead [bId] - наплавленный валик сварного шва

3.6 Read the following words correctly (consult, if necessary, a dictionary).

Implies, extremely, essentially, beveling, relatively, perpendicular, exclusively, precisely, reliable, prior to, aligned, sufficiently

3.7 Match the two halves of the sentence fragments to make logical statements.

3.8 Find in the text the English equivalents for the following phrases.

Соединение сваркой; как подразумевает название; в общей сложности – 4 обычных подтипа; при помощи разделки кромок обеих деталей; чтобы усилить шов; сварочная установка с низкой (высокой) плотностью энергии; благодаря сравнительно малой зоне шва; это делает возможным глубокое проплавление; повышенная склонность соединения к деформации; перед сваркой; отбортовка в 90 градусов; деталь, которую необходимо сварить.

3.9 Scan the text and fill in the table using the information from the texts.

3.10 In pairs discuss the reasons that make corner joints weak?

3.11 Make the text retelling using the table from exercise 9.

Характеристики

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