Application of new technology in steel structure welding
9 Steel structure embedded parts pressure submerged arc welding technology
With the rapid increase of large-span steel structure public buildings, the application of steel structure pillars (reinforcing bars) is increasing. Therefore, the pressure submerged arc welding technology of steel structure embedded parts is continuously applied in engineering practice. Its key technical measures are:
1Select a welder or a modified stud welder with stable and safe performance;
2 Carefully carry out the welding procedure qualification test and select the corresponding welding process parameters according to the diameter of the steel bar;
3 According to the principle of strong welding joints and base metal, use flux with good performance for both AC and DC.
10 Welding deformation control technology in the manufacture of large steel structural members
In the manufacturing process of large steel structures, it is very necessary and important to quantitatively calculate and analyze the flexural deformation, angular deformation and transverse shrinkage deformation of the components after welding. According to the calculation and analysis results, corresponding control measures and welding process measures are taken. It is the key to effectively reduce and reduce welding deformation, improve the processing efficiency of components, and ensure the dimensional accuracy of large components. There are several methods for welding deformation control:
(1) Control of deflection deformation of asymmetric members
1 Weld seam balance control method: Reasonably distribute the cross-sectional area of ​​the weld seam, formulate a scientific welding sequence, and reduce the amount of corrective work;
2 Auxiliary correction control method: Calculate the deflection deformation of the weld of the asymmetric component, and formulate the welding process of the asymmetric component according to the calculation result.
(2) Control of welding angle deformation
1 Anti-deformation control method: Calculate the post-weld angular deformation value of the T-joint, and formulate the box-shaped structure welding process according to the calculation result;
2 angle deformation balance control method: welding the groove weld by balanced welding method, and correcting by flame heating method.
(3) Welding shrinkage deformation control
1 Control of splicing and shrinkage deformation of components: Firstly, the shrinkage allowance of the transverse welds during splicing is calculated, and the splicing shrinkage margin is reserved according to the calculation result.
2 Control of shrinkage and deformation of the section size of the member: Calculate the transverse shrinkage deformation value of the butt joint or T-joint, and reserve the weld shrinkage allowance before assembly.
11 Ultrasonic phased array and TOFD detection technology
With the rapid development of electronic technology, especially microelectronics technology, computer technology and ultrasonic transducer technology, the ultrasonic phased array and TOFD detection technology that have emerged in recent years have become the development trend of ultrasonic flaw detection.
The ultrasonic phased array integrates multiple wafers (such as 32, 64, 128) in one probe. The excitation time of each wafer can be adjusted separately. The transducer wafer array is composed by controlling parameters such as the beam axis and focus. A scan of the full section of the weld is achieved.
The TOFD (diffraction time difference method) detection is a method of detecting defects by means of the diffraction energy obtained from the "end angle" and "end point" of the internal structure (mainly referred to as a defect) of the test piece to be inspected. Two broadband narrow pulse probes are used for detection, and the probes are symmetrically arranged with respect to the center line of the weld. The transmitting probe generates an unfocused longitudinal beam that is incident on the workpiece to be inspected at an angle. A part of the beam is received by the receiving probe along the near surface, and a part of the beam is reflected by the bottom surface and received by the receiving probe. The receiving probe determines the position of the defect and its height by receiving the diffraction signal of the defect tip and its time difference.
Based on the phased array technology, the A, B, C and S scans of the weld can be realized. By combining with the TOFD test, the three-dimensional imaging information of the weld defects can be obtained, and the typical flaw detection interface. Under normal circumstances, the detection result of this method can replace radiography, and the positioning is more accurate. It has been used in domestic aviation and nuclear industry, and the effect is very good. In the West-East Gas Transmission Project, the ultrasonic phased array detection technology is in the oil pipeline. The detection of wire joint welds plays an important role, but due to the high cost of equipment, it is still widely used in the welding inspection of steel structures in buildings.
Conclusion
In summary, the welding technology of China's construction steel structure has made great progress and development. Today, with the rapid development of physics, chemistry, metallurgy, materials, electronics, computers, automatic control, etc., with new technologies, new materials, With the continuous emergence of new equipment and new processes, the new welding technology for the manufacture and installation of steel structures in China is bound to be able to develop faster and better, such as: new digital intelligent arc welding inverter power supply, laser welding and cutting, ultra high pressure Electron beam welding, welding robot system, 4C control technology for steel structure production, namely computer-aided design (CAD), computer-aided processing (CAM), computer-aided detection (CAT), computer-aided evaluation (CAE) and other new technologies are gradually involved in construction In the field of steel structure, the welding technology level of the building steel structure will have a new situation.
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