Welding is to ensure that the ship of the ship and the strength of the key. This paper describes the ship in the welding of several common reasons for the shortcomings and propose preventive measures.Welding is to ensure that the ship of the ship and the strength of the key is to ensure that the key to the quality of the ship, is to ensure the safety of ships navigating and operating an important condition for. If there is a welding defect, it may cause structural faults, leakage, or even cause the ship sank. According to the ship brittle fracture accident investigation showed that 40 percent of brittle fracture from the accident was the beginning of the weld defects. Ships in the township in shipbuilding, ship the welding quality is particularly prominent. In the inspection of ships in the process of welding the test is particularly important. Therefore, should the early detection of defects, the welding defects restricted to a certain extent, to ensure navigational safety. Many types of ship welding defects, according to their different positions, the defects can be divided into external and internal defects. Defects have pores, slag, welding cracks, lack of penetration, not fusion, weld and shape of Dimension are not met, the biting edge, of welding, such as arc pit.first stomatal pore stomatal pore means that the welding, bubble bath in the solidification of the failed escape the hole formed. The main reason there have stomata: groove edge of dirty, water, oil and Xiuji; electrode or not provisions of curing flux, solder or rust-core skin degeneration, such as spalling. In addition, low-hydrogen welding electrode, the arc is too long, welding too fast; submerged arc welding voltage too high, are easily generated in the process of welding stomata. Because the presence of porosity so that the seam of effective cross-section decreased, too large pores will reduce the strength of welds, the destruction of the weld metal density. Prevention is to have a stoma: choose the right welding current And welding speed and groove edge to clean up water, oil and Xiuji. Strictly in accordance with the regulations custody, clearing and curing welding materials. Not to use degenerate electrode, when the skin degeneration drug discovery electrode, spalling or welding core corrosion, should strictly control the use of. SAW, should use the appropriate welding process parameters, particularly the plate automatic welding, welding speed should be as small as possible more.Sendcent, slagSlag is the residue of the weld slag. Weld slag will also reduce the intensity and density. A slag is the main reason for Weld aerobic cutting edge of gas or carbon arc shaver residual slag; groove angle or welding current is too small, too fast or welding. Acid in the use of electrode, the current is too small or because of improper transport of a paste residue to use alkaline electrode, the arc is too long or because of incorrect polarity will cause the slag. A SAW back cover, from welding wire center, but also easy to slag formation. Prevention Slag produced the measures are: select the right groove size, to clean up groove edge, choose the right welding current and welding speed, and transport of the swing should be appropriate. Multi-welding, should be carefully observed groove on both sides of melting, each layer must be welded to clean up welding slag. Back cover welding slag should be thoroughly removed, SAW attention should be paid to prevent the solder side.Third, bite Weld left edge of the Depression, known as the biting edge. A biting edge because the welding current is too large, Yun of the speed and arc welding rod stretched too long or inappropriate angle. SAW welding speed too fast or welder orbit causes of inequality, will cause the melting of welding to a certain depth, and filled with metal also failed to fill the resulting biting edge. Reduce the biting edge of the base metal joint cross-section of work, thereby resulting in the biting edge of stress concentration, it was important to the structure or structure of the dynamic load, is generally not allowed to bite While there, or to bite-depth limit. Bite-prevention approach is: Choose the right of the welding current and transport practices, the attention of control at any time arc welding rod angle and length; SAW process parameters to be appropriate, with special attention to welding speed should not be too high, welding machine to track formation.Fourth, lack of penetration, no fusionWelding, the joints were not fully root penetration of the phenomenon, known as the lack of penetration in the welding pieces of metal and weld seam or a partial layer of penetration phenomenon, known as Fusion did not. Lack of penetration or fusion is a more serious flaw, since lack of penetration or fusion, Weld will appear intermittent or mutation, weld strength greatly reduced, or even cause cracks. Therefore, in the hull of the important parts of the structure does