Гурова Г.Г., Николаева Н.С. - Обучение разговорной речи и чтению литературы на английском языке по специальности Сварка, страница 7

As in the vertical position ofwelding, 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 tothe base metal becomes increasingly difficult, and the chances of largeglobules of molten metal dropping from the electrode increase. Whenyou routinely shorten and lengthen the arc, the dropping of molten metalcan be prevented; however, you will defeat your purpose should youcarry too large a pool of molten metal in the weld.One of the problems encountered in overhead welding is the weightof the cable. To reduce arm and wrist fatigue, drape the cable over yourshoulder when welding in the standing position.

When sitting, place thecable over your knee. With experience, cable placement will becomesecond nature.Prepare the plates for overhead butt welding in the same manner asrequired for the flat position. The best results are obtained when backingstrips are used; however, you must remember that you will not always beable to use a backing strip. When you bevel the plates with a featheredgeand do not use a backing strip, the weld will repeatedly burn throughunless extreme care is taken by the operator.For overhead butt welding, bead welds are preferred over weavewelds. Clean each bead and chip out the rough areas before placing thenext pass.

Make the first pass with the electrode held at 90 degrees tothe plate. When you use an electrode that is too large, you can not holda short arc in the root area. This results in insufficient root penetrationand inferior joints.(1978)From http://64.78.42.182/sweethaven/BldgConst/Welding/lessonmain.asp?lesNum=7&modNum=7Unit 3Corner, Edge, Tee, and Lap JointsPreview. In this unit you are going to study 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.AB1. A corner jointa) is used for making corners in platesor foils that are too thin for othertypes of weld2. A flange jointb) is a butt weld between two piecesthat are perpendicular rather thancomplainer3. A melt through weldc) is used to connect two parts togetherto form a corner4. A butt weld corner jointd) is a weld, where the corner isassembled and the beam is used tomelt through the top component andinto the lower component3.3.

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 ... cuttingproduce intense sound. 3. ... the name implies, a corner joint is used to38connect two parts together to form a corner. 4. Copper backing in singleV-groove butt joints is not recommended ...

the tendency of the weldmetal 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 machinedprior to welding. 6. Because of ... the internal ... external slag-free natureof gas metal arc deposits, subsequent submerged arc welds of excellentquality can be produced. 7. ... 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. ... thehigh 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.1. What makes the difference of corner joints? 2. What are the maintypes of corner joints? 3. How strong are the welds produced? 4. Whatis used to reinforce the weld? 5. Where is a flange joint applied?Corner JointsOne of the major types of welding connection is the corner joint.As its name implies, this joint is used to connect two parts together toform a comer. This weld type is extremely useful and can be preformedwith either a high or low energy density welder. There are a total offour common sub types of corner joint, each, as usual, having its ownbenefits and disadvantages.The first common corner joint sub type is made by beveling bothparts, usually at 45 degrees for a 90 degree joint, then placing the twofaces together, and melting the outside edge.

This is usually done witha low energy density welder but a high-energy density welder can beused. A weld bead may also be added to the inside of the comer toreinforce the weld. This weld is fairly fast and easy to create, but canhave 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 betweentwo pieces that are perpendicular. This weld can be done with a lowenergy density welder if the parts are small enough, but is usually donewith a high energy density beam. This allows deep penetration and can39form a weld that is as strong as the base material.

This advantage ofstrength is countered by the increased proneness of joints to deformation,as well as the increased difficulty and equipment cost of the weld. Asin the case with normal butt joints, the edges may be machined prior towelding to improve fit, alignment or welding properties.The third type of corner welds is the melt through weld. In thisweld, the corner is assembled and the beam is used to melt through thetop component and into the lower component. This type of weld worksbest when the top piece is relatively thin compared to the bottom piece,allowing it to be melted through with a minimal energy input. This typeof welds is preformed exclusively with high energy density sources.This weld can be made easily without the need to precisely follow ajoint, but it can be weak due to the very low cross sectional area of theweld.

If necessary, multiple passes can be made if the bottom piece issufficiently thick, improving the weld strength.The final major type of comer joints is truly a flange joint. This isused for making corners in plates or foils that are too thin for the othertypes of welds. To make this type of joints a 90-degree flange is madein one of the components. This flange is then aligned to the other pieceto be welded, and the welder is run over the edges of the two parts. Thismelts the edges together and forms the weld bead. This method can beused with either a high or low energy density source and is fast andreliable, but tends to make extremely weak joints due to the leverageand odd stress angles that the flange causes.(2850)From Joining Technologies | Newgate International Business Center (slightlyabridged).3.5.

Vocabulary to the text “Corner Joints”. Try to memorize thefollowing words and word combinations:1) a corner joint — угловое соединение;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 [flænÃ] joint — сварное соединение, выполненноепо отбортовке;406)7)8)9)leverage [ li:v(@)rıÃ], n — сила, усилие;an odd stress angle — необычный угол напряжения;proneness [ pr@Unn@s], n — подверженность чему-либо;a weld bead [bi:d] — 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 logicalstatements.1.

A corner joint can be preformed with a) the relativelylow area of the welda) the relatively low area of the2. Corner joints can have problems with strength due tob) if the bottom piece is sufficiently thick, improving thewells strength3. Multiple passes can be madec) when the top piece is relatively thin compared to thebottom piece, allowing it to bemelted through with a minimal energy input4. Flange joints tends to makeextremely weak joints due tod) the leverage and odd stressangles that the flange causes5. Melt through weld works beste) either a high or low energydensity welder3.8.