焊条电弧焊-----外文翻译.doc

附录 Shielded Metal-Arc Welding Shielded metal-arc welding is an arc welding process wherein coalescence is produced by heating with an electric arc between a covered or “coated” metal rod called the electrode and the work. Shielding is obtained from decomposition of the electrode covering, and filler metal is obtained from the eletrode’s metal core and metallic particles in the covering.The source of the shielding and filler metal varies with electrode design. The shielding and filler metal largely control the mechanical,chemical,metallurgical and electrical characteristics. Shielded metal-arc welding is by far the most widely used of the various electric arc welding processes. Like the other electric arc welding processes,it employs the heat of the electric arc to bring the work to be welded and a consumable electrode to a molten state.The work is made part of an electric circuit knowm as the welding circuit(Fig.IV-1).This circuit includes a source of power,welding cables,an electrode holder a ground clamp and the consumable welding electrode.One cable carrying current from the power source is attached to the work ,and another cable is attached to the electrode holder. Welding begins when an electric arc is formed or struck between the metallic electrode and the work.The intense heat of arc melts the electrode and the surface of the work adjacent to the arc.Tiny globules of molten metal rapidly form on the tip of electrode and transfer through the arc into the molten weld poor or weld puddle on the work’s surface.If the welds are flat or horizontal,the actual transfer is induced by the force of gravity,molecular attraction and surface tension.Molecular attraction and surface tension are the forces that induce metal transfer from the electrode to the work where the weld is being made in the vertical or overhead position.The arc is moved along the work,metaling and fusing the metal as it progresses. Since the arc is one of the hottest commercial sources of heat (tempe