Scanning electron microscopy inspection shows the position of the bolts and bolts on the copper plate on the copper plate. According to the macroscopic shape and color of the fracture, it is preliminarily determined that the No. 3 is the bolt that falls first. The bolts that fall off on both sides of the No. 3 bolt are numbered 1 and 2. At the same time, for the sake of comparison, the bolts at the same position on the other copper plate were knocked out and numbered as No. 4. The sample fractures of No. 1, 2, 3, and 4 were examined and analyzed by a QUANTA-400 scanning electron microscope, which is a SEM image of the bolt fracture. It can be seen that there are many welds in the fractures of No.1, No.2 and No.3 samples, and the unwelded area of ​​the fracture of No.3 sample accounts for 1/2. Further enlargement observation, the unwelded joint is free surface. There is a large amount of flux slag distributed thereon. The fracture at the weld joint is the same as the fracture of the bolt that is manually knocked out. Moreover, there is a layer of high temperature oxide scale in the No. 3 fracture joint. This further proves that the No. 3 bolt is first welded, and the open welding surface is oxidized by high temperature under the action of high temperature on the liquid surface after the welding. The metallographic examination showed that the No. 1 and No. 4 bolts were cut along the axis and polished, and then electrolytically etched with a 10% aqueous solution of oxalic acid, and observed under an optical microscope. It can be seen that a relatively uniform copper-iron alloy transition layer is formed at the weld. There is no such junction layer without solder joints (see 7). The matrix structure is austenite. The effect of welding defects After the bolts and copper plates are welded by fixed-point resistance, if there is no welding defect, the continuity of the weld is destroyed, resulting in a decrease in the strength of the weld and artificially causing a source of fracture. During use, under the action of the vibration force of the continuous casting machine mechanical system, the stress is concentrated and expanded at the source of the fracture. When a bolt is broken and the weld is broken, the binding force between the copper plate and the spare plate is not balanced. Under the action of high temperature, since the thermal expansion coefficients of the two materials of the copper plate and the standby plate are different, the bolts falling near the bolt are subjected to the expansion stress. In this way, when there are welding defects in the nearby bolt welds, stress concentration is inevitably formed at the defects, which eventually leads to the breakage of the nearby bolts and the loss of the fastening function. The position and temperature effects are in the 2nd row and the 3rd row from the position of the bolts broken by the open welding, because this position is precisely the position of the molten metal surface in the crystallizer and the highest temperature in the crystallizer. The position of the bolt at this location is also the most affected by the temperature. At the same time, the copper plate is also thermally expanded, and the copper plate is inflated and deformed inwardly, and a tensile stress is applied to the fastening bolt, and the presence of welding defects necessarily causes the bolts which are defective here to be broken in advance. Conclusion The reason for the early failure of bolts is that there are weld defects in the welds after welding between the bolts and the copper plates, which destroys the continuity of the welds and reduces the strength of the welds, and is subjected to various stresses during operation. The bolt breaks ahead of the weld and fails. Suppliers are advised to further study the welding process or to study the mechanical connection of the bolts to the copper plate. Pdc Cutter For Grinding,Pcd Grinding Plates For Grinding,Polycrystalline Diamond Insert For Cutting Tools,Pdc Shoes For Grinding Henan Bohong New Material Co., Ltd , https://www.bohongpcd.com
Analysis of failure of welding of internal plate and spare tightening bolt of smelting and casting equipment
Scanning electron microscopy inspection shows the position of the bolts and bolts on the copper plate on the copper plate. According to the macroscopic shape and color of the fracture, it is preliminarily determined that the No. 3 is the bolt that falls first. The bolts that fall off on both sides of the No. 3 bolt are numbered 1 and 2. At the same time, for the sake of comparison, another copper plate will be