The bolt is made of steel No. 50 and has a diameter of 160 mm. The bolt is subjected to a large impact force during operation, so the welding quality must be guaranteed. If defects such as cracks, pores, and slag are generated during the welding process, the bearing capacity of the bolt will be lowered. In order to ensure the quality of welding, a reasonable welding process has been formulated, and a number of quality assurance measures have been taken. It has been proved by practice that it fully meets the requirements for use and has achieved satisfactory results. The bolt is cylindrical with a diameter of 160 mm. In order to ensure the penetration, double inverted cone type groove is used. The bolt itself is medium carbon steel with 0.5% carbon content, containing 0.3% silicon, 0.7% manganese, 0.03% phosphorus and 0.02% sulfur. Due to the poor weldability of the base metal itself, the plasticity and fatigue resistance after welding are relatively low, and the quenched structure is prone to occur. The cold cracking and hot cracking tendency are also relatively large. Therefore, the alkaline low hydrogen type E5016 electrode is selected. Drying. At the same time, it is necessary to adopt short-circuit continuous and multi-layer multi-layer welding to achieve the effect of preheating and heat preservation in the heat affected zone of the base metal. The BX3-300 AC arc welder is used, and the weld is made by manual arc welding. The welding environment temperature is greater than 10e. At the same time, in order to prevent wind, the welding site is surrounded by iron sheets to ensure the stability of the welding site. The welder must train the welder who participated in the construction before the welding is carried out, and the welding content will be checked and confirmed before the welding work. In order to ensure the welding quality and easy operation, the lathe processing on the inverted cone type of the independent part ensures that the base surface smoothness after processing is greater than 3. For the part connected to the lower part, the groove is cut with gas cutting and sanded with a grinder. To ensure a smooth surface and no scale. There shall be no cracks and delaminations in the groove, and there shall be no deep grooves, otherwise it shall be repaired. When repairing, the defect and the oxide layer should be ground off with a grinding wheel, then surfacing, and smoothing after welding. The bolts should be aligned with the upper and lower centers to ensure the verticality of the upper part, and the misalignment amount should not exceed 1 mm. It can be inspected by wire hammer and square rule. When the positioning welding is docked, the spot welding is carried out at the root with <3.2 electrode, and the positioning is strengthened in the upper spot welding fixture. Fixtures can be made of N63 angle steel and welded with J422 welding rod. First, the root is welded, the weld layer of the post-weld layer and the root of the surface layer are applied with a large current, <3.2 electrode is welded to ensure penetration, no defects, and the defect is found to be polished and re-welded by a polishing machine. The root weld is 1/5 of the diameter of the circumference, the transition layer is 3/5 of the diameter of the circumference, and the surface layer is 1/5 of the diameter of the circumference. Each layer of welding is inspected to ensure the quality of the welding. Each layer of the weld shall be inspected. After the root inspection is passed, the transition layer shall be welded. After the transition layer is passed, the surface layer shall be welded. In addition, the welding shall be inspected at any time during the welding process. Quality, found to be defective immediately removed re-welding. The transition layer and the surface layer are welded with small line energy, multi-pass welding, and the interlayer temperature is controlled below 50e. The workpiece is preheated before welding, and the preheating temperature is controlled at about 150e, which can effectively prevent cracks. After welding, due to the cold brittleness of No. 50 steel, it is easy to produce hydrogen-induced cracking. Insulation measures should be taken. Winding with 50mm of <20mm asbestos rope, keeping it for 2h3h, slowly cooling it to room temperature, then assembling it, in order to ensure the verticality of the bolt after welding. Degree, the welding should be carried out circle by circle.
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