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Forms and Causes of Steel Structure Welding

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Forms and Causes of Steel Structure Welding
Issue Time:2020-02-03
Steel structure connections are generally welded, and full penetration welding is generally used for some important welds. During the local heating and melting process of metal welding, the temperature of the metal in the heating zone and the surrounding base metal are very different, which causes transient stress during the welding process.

After cooling to the original temperature, the tensile stress area of ​​the weld and the near-seam area of ​​the entire joint area and the base material are balanced in the compressive stress area, which results in the welding residual stress of the structure itself.

At this time, various forms of deformation occur in the structure of the welded part under the action of welding stress. The existence of residual stress and the generation of deformation are mutually transformed. It is not difficult to find a way to prevent the reduction and correction of deformation when the deformation law is recognized.

First, the form and reason of welding open

The deformation of steel structures after welding can be roughly divided into two cases: the deformation of the overall structure and the local deformation of the structure. Deformation of the overall structure includes longitudinal and lateral shortening and bending (ie warping) of the structure. The local deformation is manifested as convex curve, wave shape, angular deformation and so on.

1.1 Common basic forms of deformation
The common basic forms of welding deformation are as follows: the deformation of the plate groove butt welding shortens the length (longitudinal shrinkage) and the width of the plate is narrowed (transverse shrinkage); the angular deformation of the plate groove butt welding produces

Twisted deformation caused by the different angular deformation of the welded member along the longitudinal axis of the member and the inconsistent longitudinal shrinkage of the flange of the member and the web;

After welding of the thin plate, the compressive stress area of ​​the base material is deformed due to wave deformation caused by warping of the plate surface; due to the asymmetry of the longitudinal and lateral shrinkage of the weld relative to the neutral axis of the component, the overall bending of the component is caused by this deformation: Bending deformation.


These deformations are all basic deformation forms, and various complex structural deformations are the development, transformation and synthesis of these basic deformations.
 
1.2 Reasons for welding deformation:
Local and uneven heating of the weldment during welding is the cause of welding stress and deformation. During welding, the metal in the weld and the heated area near the weld expands. Because the colder metal around it prevents this expansion, compressive stress and plastic shrinkage deformation occur in the welded area, resulting in different degrees of lateral and longitudinal shrinkage. Due to the shrinkage in these two directions, various deformations of the welded structure are caused.

Dalian Guangtong Steel Structure Co., Ltd., established in 1998, is located in Dalian Free Trade Zone. Specializing in the design and manufacture of steel structures and non-standard metal parts. The company covers an area of ​​18,000 square meters, of which the plant area is 13,000 square meters, with an average annual output of more than 20,000 tons. The company has dozens of advanced processing and testing equipment. More than 100 employees, including technicians and skilled workers, account for more than three-quarters. The company advocates safety first, quality first, and green production. In addition, it has obtained ISO9001 quality management system, ISO14001 environmental management system, OHSAS18001 occupational health and safety management system, EU EN1090 system certification and ISO50430 construction enterprise quality management standard certificate. Has the qualification for construction steel structure engineering contracting. Adhering to the business philosophy of sincerity, pragmatism and innovation, our company has developed into a management system integrating design, production, production and sales, is committed to creating more wealth and value for customers, and is committed to becoming a steel structure industry outstanding company.