Usually, the end faces of the welded lifting rails are perpendicular to the longitudinal direction of the rail, but in a few cases, non-perpendicular conditions may occur. Some customers require 45 degree mitre cutting crane rails. The intention of using the 45 degree mitre cutting crane rails is to reduce the impact on the rails when the crane is walking. Practices have shown that this can reduce the damage to a certain extent, but the impact problem cannot be completely solved. The 45 degree mitre cutting crane rails also exist in certain problems, and the rail joint is prone to lateral misalignment when it’s subjected to the expansion rail pressure. Therefore, the solution to the problem is to weld the 45 degree mitre crane rails into seamless crane rails. Since the end face of the crane rail is inclined, the conventional flash butt welding, air pressure welding and aluminum heat can not be completed. Because if you want to weld, you must cut the bevel into a vertical end face before you can consider welding. Even if the rail is cut into a vertical end face, the flash butt welder is bulky for a lifting rail of a special cross-sectional shape, high-power power source is required, and it is not suitable for field welding. Gas pressure welding requires a prototype heater and corresponding fixture for such a special rail type. Aluminum heat welding also requires the design of special molds, high processing costs and long cycle times. In contrast, the narrow gap arc welding method is more flexible, because only arc welding is to use local heating to weld the rail, and the vertical requirement of the section is relatively low. Although the oblique section welding will have certain difficulty, it may be realized.
Narrow gap arc welding method Welding rails are currently widely used in Japan and Europe, and are mainly used for wire welding of railway rails. Among them, Japan mainly use this kind of welding method in the rail welding of the Shinkansen high-speed train, and the aluminum heat welding is abandoned. The advantage of welding the 45 degree mitre cutting crane rail by narrow gap arc welding method is that the quality of the welded joint can be effectively guaranteed, but the mold design and welding process selection are more complicated. The rail bottom of the lifting rail is 200mm wide, and the length of the rail bottom of the inclined end surface is more than 300mm, which is much longer than the length of the general rail weld. The biggest problem with too long weld seam is that they are very susceptible to slag inclusions, incomplete penetration or poor post-forming. Since the bottom of the rail is located at the lowest point of the welding, once the welding defect is not easy to find, it is not easy to produce re-welding. In addition, the bottom end of the narrow end of the inclined end of the mold is more complicated. We should not only consider the slag removal of the long weld, but also consider if the shape is reasonable, and it can not touch the bolts at the bottom of the fixed rail, the design must ensure that the bottom mold can be placed before welding at the bottom of the rail, and normally removed after welding. The design of the rail waist and rail head welding die should fully depend on the asymmetrical shape of the lifting rail at both ends of the oblique section. The mold and the rail body should retain proper clearance, the gap on the acute side should be appropriately reduced, and the obtuse side should be appropriately enlarged.