Looking at the current status of building steel structure engineering and development trend, more and more with modern architectural style and architectural features of high technology, and its main features are:   
      1 A novel and unique shape, structure, system range, the node structure is complex, multi-form welded joints, component production and field installation of the welding technology more and more difficult. For example: the National Stadium "Bird Nest" a large number of complex steel structure truss columns, the main truss, secondary structure of welded joints, weld criss-cross, the construction is very difficult. 

        2 building height high, large span structures, earthquake resistance design of the main steel structure, high quality requirements. Such as: frame beam and column connection weld connecting the shear plate and column weld, the beam web connection with the column and the column weld seam stitching, are the main parts of the structure, basically Singapore population penetration level of weld, 100% ultrasonic testing, welding quality requirements are very high.

        3 Use the varieties of steel specifications, and more and more tend to use high-strength low-alloy structural steel and large thickness of the steel, iron and steel production process level with the continuous improvement of cast steel, stainless steel, composite steel has also been increasingly more and more applications. Therefore, the required on-site before the construction of the steel used for the delivery of state of affairs, a new real-time test for welding steel, welding parameters to explore science, welding technology to develop appropriate measures. 

       4 factory production and field installation link to many factors, many different types of cross-operation, on-site installation difficult.