Welding Metallurgy. Sindo Kou. Читать онлайн. Newlib. NEWLIB.NET

Автор: Sindo Kou
Издательство: John Wiley & Sons Limited
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Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119524915
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beam of very high intensity can vaporize the metal and form a vapor hole during welding, that is, a keyhole, as illustrated in Figure 1.26b.

Schematic illustration of the electron beam welding showing (a) the process and (b) keyhole. Schematic illustration of the dispersion of electron beam at various ambient pressures.

      Source: Welding Handbook, Vol. 3, 7th Edition, © American Welding Society.

Schematic illustration of the welds in 13-mm-thick 2219 aluminum: (a) electron beam weld, (b) gas–tungsten arc weld.

      Under high welding speeds, weld porosity results when gas bubbles do not have enough time to escape from the deep weld pool. Materials containing high‐vapor‐pressure constituents, such as Pb‐containing alloys, are not recommended for EBW because evaporation of these constituents tends to foul the pumps or contaminate the vacuum system.

      1.4.1.2 Advantages and Disadvantages

      With a very‐high‐power density in EBW, full‐penetration keyholing is possible even in thick workpieces. Joints that require multiple‐pass arc welding can be welded in a single pass at a high welding speed. Consequently, the total heat input per unit length of the weld is much lower than that in arc welding, resulting in a very narrow HAZ and little distortion. Reactive and refractory metals can be welded because there is no air in vacuum to cause contamination. Some dissimilar metals can also be welded because the very rapid cooling in EBW can prevent the formation of coarse brittle intermetallic compounds. When welding parts vary greatly in mass and size, the ability of the electron beam to precisely locate the weld and form a favorably shaped fusion zone helps prevent excessive melting of the smaller part.

Schematic illustration of the missed joints in electron beam welds in 150-mm-thick steels: (a) 2.25Cr–1Mo steel with a transverse flux density of 3.5 G parallel to joint plane, (b) SB steel and A387 steel.

      Source: Blakeley and Sanderson [17]. Welding Journal, January 1984, © American Welding Society.

      1.4.2 Laser Beam Welding

      1.4.2.1 The Process

Schematic illustration of the laser beam welding with solid-state laser including (a) the process, (b) energy absorption and emission during laser action.

      Source: Welding Handbook [1]. Welding Handbook, Vol. 3, 7th Edition, © American Welding Society.

Schematic illustration of the keyhole laser-beam welding includes (a) the process and (b) CO2-laser weld in 13-mm-thick A633 steel.

      Besides solid‐state and gas lasers, semiconductor‐based diode lasers and fiber lasers have also been developed. Diode lasers of 2.5 kW power and 1 mm focus diameter have been demonstrated [19]. Conduction‐mode