ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
The secondary truss is also a steel pipe truss structure with inverted triangle cross section. Each truss is about 2 m long. It consists of two sizes of pipe diameter. The string truss is seamless pipe and the web bar is welded pipe. The longest section is 47608m and the shortest is 39303m. Each time the truss is processed in the factory, it is divided into three sections, which are transported to the site and arched according to the routine after assembly. The project quality requirements are very strict; linear, beautiful appearance is also very important; and there are many intersecting tubes, high technical requirements, so the main arch structure of the steel pipe cutting all choose CNC plasma intersecting wire cutting machine, the cutting machine six-axis linkage, plasma cutting, computer control cutting machine cutting speed, variety of angle change. Therefore, the blanking of components meets the requirements of precision in design and manufacture technology, and forms the required groove. After cutting, the main chord and web are assembled, and then the arch is raised on the pre-fabricated frame. The arch height h is 3.1.2 according to the radius of the center of the circle and the length of each solitary section. The steel pipe truss structure requires smooth lines and graceful shape. The connection of the steel pipe is mainly welded, so the welding technology plays an important role in the steel pipe joints. Status.
No matter from the fabrication of welded joints, the welding process and the non-maple inspection technology have special requirements. The specifications of pipe truss steel pipe in this project are various: the largest is steel pipe column 450*10, the smallest is decorative truss web 42 and pipe wall deformation is large, and the requirements for welding are high, otherwise it is easy to weld through the pipe wall. The connection forms of steel pipe are as follows: T-shaped K-shaped, T-Y-shaped, TK-shaped composite and X-shaped intersecting joints with branch pipe are T, Y, K or composite joints, and the end of branch pipe is saddle-shaped curve. The pipe-closing intersecting joint can be divided into four sections: T, Y, K or composite intersecting joints between the main pipe and the branch pipe. The end of the branch pipe is saddle-shaped curve. This kind of tubular joints are divided into four parts, two sides and root zone joints. The welds can be divided into three parts: full penetration welding, partial penetration welding and fillet welding, which are different according to different design bearing requirements. Because of the different thickness of the pipe and the different angle between the branch pipe and the main pipe, the welding form and the height of the weld are also different.
If correspond to different pipe walls, some need to cut a certain groove angle at saddle curve of branch pipe to weld. However, when the wall thickness of the branch pipe in this project is small and the angle between the branch pipe and the main pipe is less than 300, it is difficult to weld the root zone. It must be filled at the bottom of the angle to a certain width before the normal weld can be welded. The effective value of the weld seam must be sampled and inspected to verify the welding process qualification. Due to the limitation of material, processing, transportation and installation conditions, the truss must be processed, transported and installed in segments, and the steel pipe must be spliced. The steel pipe splicing forms are commonly used in the following three forms, corresponding to different requirements and material characteristics of the truss assembly on the assembly frame for single truss welding, the truss assembly must be in accordance with the welding sequence of first welding intermediate joints, then extending to the two end joints of the truss, in order to avoid the accumulation of weld shrinkage to one end caused by each truss. Size error between nodes. Moreover, the weld size at both ends of the same branch pipe should not conform to the calculation thickness required by the platform design, but too much surfacing should be avoided to increase the welding residual stress.
When the root clearance of the weld is larger than the standard value (1.5mm), the size of the weld can be added according to the excess clearance value. However, when the gap is more than 5 mm, surfacing and grinding should be used to repair the end of branch pipe or surfacing weld on the main pipe surface at the junction to reduce the gap between welds.