Three. Analysis of Steel Structure Production Technology
(A) construction focus and difficulties
1. Curved box steel girder is the important force of the roof structure, the position of the joint of the bar itself is more, and it is easy to produce angular deformation, distortion, local or integral deformation during the welding process. If the welding deformation is not effective Control, will directly lead to the appearance of the component size serious tolerance, component quality can not meet the design, specification requirements, will give the site installation to bring considerable construction difficulty.
2. H-beam because of the wide flange, and the thickness of 10-20mm, if the use of submerged arc welding, the welding position is not easy to operate, and easy to produce welding deformation, so the structure of the welding is the focus of this project.
3. The support of the column is the tube-tube structure, the cutting precision of the tube and the precision of the cut-out size are the key to ensure the quality of the intersecting welding. Therefore, the intersecting line cutting of the steel pipe is the focus of this project.
(B) technical measures for the production of steel structure of the project
1. For box steel girders, in order to prevent the use of horizontal welding and choose a reasonable welding process, the use of simultaneous, symmetrical welding sequence for welding.
2. For wide flange H-shaped steel, the use of CO2 gas shielded welding for welding, can reduce the welding deformation, to ensure its welding quality. CO2 welding is characterized by large melting depth, welding heat affected zone is small, high melting efficiency, suitable for all-position welding, production can be automated / semi-automatic, high welding quality, high productivity, relatively low cost.
3. In the intersecting line CNC cutting machine for cutting, to ensure its cutting accuracy. The process is in the computer modeling, the equipment directly cutting cutting, not only cutting high precision, and fast.
A. Welding quality assurance measures
Using a reasonable welding process.
1 )double-sided groove should be used on both sides of symmetrical multi-pass welding, to avoid shrinkage strain concentration.
2 )Use appropriate small heat input multilayer welding to reduce shrinkage strain.
3 )box-shaped column angle connector, when the thickness of the larger side of the side of the board edge of the flame cutting surface should be grinding (or planing) to the heat generated by the hardening layer of tissue.
4 )using low hydrogen, ultra-low hydrogen electrode or gas shielded welding method.
5) use or improve the preheating temperature welding, in order to reduce the cooling rate, improve the joint area toughness, but the use of the preheating temperature is high when the shrinkage strain is easy to increase.
6 )The use of post-welding hydrogen heat treatment to accelerate the diffusion of hydrogen to prevent cracks.
B. Supports intersecting connections for multiple nodes
This part of the project is a dendritic structure, and the phenomenon of the intersection of multiple rods is more common. This puts forward the higher requirements for the control of the cutting, group and welding deformation.
1. Typical node form
2. Precision assurance measures
As the large-scale steel structure part of the space box-type component in the form of intersecting line structure, so the intersecting line node manufacturing accuracy of the project a major focus, therefore, intersecting line processing to use high precision processing equipment, After a detailed comparison of a variety of equipment to be used after the import of six-dimensional intersecting line cutting machine, the maximum to meet the processing accuracy requirements, the device has a flame and plasma cutting in two ways to cut diameter 50mm-800mm of various pipe fittings, and At the same time to open a good welding profile.