船舶焊接中常见缺陷的原因和防止措施（Causes and prevention measures of common defects in ship welding）.doc

船舶焊接中常见缺陷的原因和防止措施（Causes and prevention measures of common defects in ship welding） Ship welding is the key to ensure the tightness and strength of ships. It is the key to ensure the quality of ships and the important condition to ensure the safe sailing and operation of ships. If the welding has defects, it may cause structural fracture, leakage, and even cause the ship to sink. According to the investigation of ship brittle fracture, 40% brittle fracture started from the weld defect. In the shipbuilding of towns and villages, the welding quality of ships is particularly prominent. During the inspection of the ship, the inspection of the weld is very important. Therefore, the defects should be found as soon as possible, and the welding defects will be limited within a certain range to ensure the safety of navigation. - P6, D7, e$, U:, I:, Y, D1,, H2, U4, C ` G, * *: T, O0, M, F1, l, F, welding defects of many kinds of ships, according to their location, can be divided into external and internal defects. Common defects have porosity, slag, weld crack, lack of penetration, lack of fusion, weld shape and shape requirements, undercut, such as arc pit. X4 ~2 + J# r! N: D9 _; A; G C! F. / G, W e z% J. z/ C [the! X porosity is the void formed when the bubbles in the weld pool fail to escape during solidification. The main reason of pore formation: groove edge of dirty water oil and rust; electrode or flux without baking cores according to the regulations, rust or skin degeneration drug and spalling. In addition, when the low hydrogen electrode is welded, the arc is too long, the welding speed is too high, and the submerged arc welding voltage is too high, which is easy to produce porosity in the welding process. Because of the existence of the porosity, the effective cross section of the weld is reduced, and the excessive porosity will reduce the strength of the weld and damage the compactness of the weld metal. The way to prevent blowhole is to select proper welding curr