The crane 's running track is generally relatively long, and it requires multiple tracks to be welded together. In order to ensure the safety of the track, there are certain requirements for orbital welding. The editor of our factory will share with you:
Before welding the crane rail joint, carefully clean the groove and nearby oil, rust and other dirt until the metallic luster is exposed. The welding consumables are matched to the basic welding rod according to the principle of equal strength, and its grade is J857 (national standard
The height of the rail end padding in advance depends on the type, length and fixing condition of the rail, as well as the ambient temperature and other factors. The rail end padding up 30-40mm with a copper pad and carbon steel plate is used in advance, and the use has been made. Connecting parts such as bolts and pressure plates, tighten the nuts to fix the rail on the rail beam, and set at least 4 fixing points near each rail joint. When the bottom of the rail is welded, loosen the pressure plate, lower the pad part of the rail end to 20mm, and then tighten the pressure plate nut. When welding the rail waist part, gradually reduce the height of the backing plate. When the rail waist part is welded, all the backing plates should be removed and the pressure plate should be loosened. At this time, there should be a small upturn value at the rail joint. During the heading process, according to the straightness of the rail, it is decided whether to tighten the pressure plate nut again. In the entire welding process, it is necessary to check the deformation of the rail joint with a straight steel ruler at any time, and adjust the height of the joint and tighten the pressure plate at any time to control the deformation of the rail joint. When fixing the rail joints before welding, the gap left between the two rail ends is wide at the top and narrow at the bottom. Based on the gap at the bottom of the rail, it should not be less than 12mm, nor should it be too wide. Generally, it should be within the range of 15-18mm. . When adjusting the fixed rail joints, in addition to ensuring the size of the end gap, the two rail ends must also be aligned, and there must be no distortion or stagger. Before and during welding, check strictly and ensure that the center lines of the two rails are on the same line to prevent the rail from being welded.
At the same time, there is usually a phenomenon of bending not straight. When welding the rail joints of the rail fixed with hook bolts, refer to the above method according to the specific situation, and set up temporary fixtures to fix the rail for welding.
The sequence of welding the rail joints is from bottom to top, the bottom of the rail first, the waist and the head of the rail, layer by layer, and finally the surrounding area is repaired. The ends of the two rails are each 40mm, and they are preheated at the same time. The preheating and interlayer temperature are controlled at 300℃～350℃. First layer welding (priming): current 120A～130A to prevent the permanent carbon steel backing plate from burning through and melting the copper backing plate, thereby reducing the difficulty of removing the copper backing plate and shortening the air cooling time of the track to help maintain the interlayer Temperature to prevent quenching; each layer can be used (130±15)A in the future, and the welding slag must be removed after each layer is welded before welding can be continued; Rail waist welding: current 130～140A, welding from the lower part of the waist, pay attention to slag removal .
Rail head welding: current 130～140A, after installing the copper pallet, start welding, pay attention to removing slag once for each layer; finally, repair the unsoldered area around the weld.
When applying each layer of welding wave, especially when applying each layer of welding wave at the bottom of the welding rail, one electrode should be used to complete the welding. Avoid using the welding electrode in the middle to break the arc. The welding direction of the front and back two layers of welding waves should be opposite. ; The welding work of each rail joint should be carried out continuously to keep the rail end welded at a higher temperature (300℃～350℃). After welding, when it is not cooled after stress relief heat treatment, it must be protected from rain, etc.; the hot copper plate can be removed and soaked in water for cooling, so that it can be reused next time.
The stress relief heat treatment of the rail end after the welding is an important measure to improve the welding quality. For the rail to be welded at a relatively low temperature, such as winter construction, it must be used
This measure: stress relief heat treatment uses gas welding nozzles to repeatedly heat around the rail head, rail waist and rail bottom. The full section of the rail should be heated as uniform as possible, and special attention should be paid to the heating quality of the rail bottom. The stress relief heat treatment temperature is 620℃～650℃, and the range of the stress relief heat treatment is 40mm on both sides from the center of the weld; after the stress relief heat treatment temperature is reached, the constant temperature heating must be ensured for more than 20～30min, and needling The blanket is wrapped with thermal insulation cotton, and the thermal insulation is slowly cooled until normal temperature.
After the crane rail welded joints have been subjected to stress relief heat treatment and cooled to atmospheric temperature, the welds on the top surface and both sides of the rail are flattened. When the welding protrusion is too large, use a grinding wheel polisher to polish until it is flush with the rail head, and finally polish the surface.
There are usually two types of rail joints at the expansion joints of the factory building: one is connected by splints or fishplates, and the rail uses 45° slanted joints with a gap of 10mm. The other is connected by splicing splints that are processed according to the shape of the rail head, with a gap of 50mm.
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