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

Автор: Sindo Kou
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119524915
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the electric current enters the electrode. Consequently, the cathode spot moves around rather randomly and quickly in the flat electrode end. The time‐averaged diameter of the area covered by the moving spot can be considered as the effective cathode spot size. Without a conical surface at the electrode end, the resultant Lorentz force is still inward and downward, but the downward component is reduced as illustrated in Figure 3.5a. Consequently, the resultant arc can be expected to be more constricted, as shown in Figure 3.5b.

Schematic illustration of the arc produced by a tungsten electrode with a flat end: (a) Lorentz force (F) and (b) fluid flow. Schematic illustration of the current-density field (left) and Lorentz force (right) in an arc produced by a tungsten electrode with a flat end.

      Source: Tsai and Kou [1]. © Elsevier.

Graph depicts the velocity and temperature fields in an arc produced by a tungsten electrode with a flat end.

      Source: Modified from Tsai and Kou [1]. © Elsevier.

      3.2.1 Gas−Tungsten Arc Welding

Graph depicts the electrical conductivity of Ar and He and how they are affected by Fe vapor.

      Source: Tanaka et al. [7]. © IOP Publishing.

Schematic illustration of 304 stainless steel welded by stationary gas-tungsten arc for 20 s: (a) He as shielding gas, showing much Fe vapor deposit, (b) Ar as shielding gas, showing little Fe vapor deposit, (c) cross-section of weld made with He shielding.

      Source: Tanaka et al. [7]. © IOP Publishing.

Graphs depict the computer simulation of gas-tungsten arcs considering metal evaporation from pool: (a) (b) Ar arc, (c) 1 percent N2 in Ar causing porosity, (d) (e) He arc. (f) 1 percent N2 in He causing no porosity.

      Source: Kodama et al. [8]. Springer Open Access.

      3.2.2 Gas−Metal Arc Welding

      Murphy [9–13] studied the effect of metal evaporation on gas−metal arc welding (GMAW) of Al alloys. In GMAW significant evaporation of metal elements can occur at the tip of the filler metal, which will be called the wire here for simplicity. The wire is usually positive in polarity, and the electrons enters the melted wire tip and release much energy equivalent to the work function (Section 1.3.2.2). At the anode spot at the melted wire tip, the boiling point of the wire material is achieved. The concentration of metal vapor in the arc can become as high as 50% [10–12].