Abstract : Combined with the Wuhan light rail track project, the construction process of the welding rail with K920 small welder is introduced in detail.
Key words : Wuhan light rail; K920 welding machine; construction method
1 Overview The quality of rail welding is of great significance for railway traffic safety and extending the service life of the rail. At present, the seamless lines laid by China's railways are generally contact welded by factory welding, and small pressure welding and aluminum heat welding are used for site welding. Due to the high degree of mechanization of contact welding, the weld material is equivalent to the base metal, and the welder has a quality monitoring system to ensure the quality of each weld head is stable and consistent, so the weld quality of the contact weld is the best among the three welding methods.
The K920 flash contact welder was jointly developed and produced by the Scientific Research Institute of the Shanghai Railway Bureau and the China Railway 11th Bureau Group under the auspices of the Department of Science and Education of the Ministry of Railways. According to the needs of the first phase of the Wuhan Rail Transit Railway, the China Railway 11th Bureau The machine was ground with a small fixed welding. The project has a full-length double line of 10.234 km, of which the single-lane line is 19.2 km and the rail is PD360 kg/m. In the construction, the standard rail of 25 m was first welded to a 1.5 m long rail by K920 welder, and it was sent to the site through a long-track transport vehicle and then welded into a seamless line by mobile air pressure welding.
2 K920 welder features
(1) The machine is compact in structure, convenient for transportation and installation, and supports two containers in place. After the rail track line is installed, the production capacity can be quickly formed. It is especially suitable for base welding of small-scale seamless lines, occupying less space and quicker installation and production.
(2) The whole process of welding is controlled by computer to ensure the welding quality is uniform and reliable.
(3) The process is simple, the labor intensity is small, and the use is safe and convenient.
(4) It can be self-generated or externally connected, which is convenient and flexible.
3 Construction process
3.1 Process Flow (Figure 1)
3.2 Operation process and points
The welding rail production line is installed and arranged according to the construction requirements. Under normal circumstances, there are optional rails, rail end treatment, push, welding, normalizing, grinding, flaw detection and inspection, long rail lifting and other work stations. The form writes out its operating procedures.
(1) Optional rails Use 25 5 gantry cranes to hang a 25 m long standard rail on the railing platform. After inspection and measurement, determine whether it can be welded. The rail to be welded shall meet the following requirements:
1 All the rails are inspected and the damaged rails are removed;
2 The rail shall be straightened to make the full length of the rail straight and not hard, and the straightness of the rail shall not exceed 0.5 mm within 1 m of the length;
3 The rail length error shall not exceed ±10 mm; the unevenness at the saw cut surface shall not exceed 0.5 mm;
4 There shall be no defects such as cracks, heavy skin, slag inclusions, shrinkage holes and severe segregation on the surface or inside of the rail.
(2) Before the rail end treatment rail welding, the rust removal treatment should be carried out on both ends of the welding rail on the distribution platform. The surface is required to be smooth and clean, and there must be no rust spots. The grinding amount should not exceed 012 mm at a time. If the welding rail is to be welded for more than 24 hours or the oil and water are contaminated, it must be re-polished and the grinding length is about 600 mm.
(3) After the welding rails are aligned, the power is turned on, and the two jaws are soldered at 400 V to activate the automatic welding procedure, respectively entering the pre-flash phase, stable high-pressure flash phase, low-pressure flash, accelerated flash, and upset forging. After the top forging is completed, the entire welding process is completed.
After the flash welding is completed, the rail clamping device quickly releases the two jaws, and the pusher knife in the welding head immediately pushes the tumor to complete the welding of a rail joint.
(4) Normalized rail welded joints are subject to post-weld treatment. The heat treatment uses (oxygen + acetylene) flame normalizing. The flame normalization begins when the rail weld head temperature drops below 500 °C. The heater oscillates along the longitudinal direction of the welding head. The surface temperature of the heating of the rail head generally does not exceed 950 °C, the surface temperature of the rail bottom heating is not lower than 830 °C, and the surface of the rail surface is heated by a photoelectric thermometer and is normalized. recording.
(5) Grinding the top surface and side of the rail of the welded rail joint by using the rail grinding machine, it is not suitable to horizontally grind the weld when grinding, and does not make the surface of the rail "blue". If the temperature is high during sanding, it is necessary to suspend the grinding and polish it when the temperature is suitable.
(6) Weld flaw detection The ultrasonic flaw detector is used to inspect the rail welds. The following requirements are met: the flaws are to be naturally cooled to below 50 °C; any part of the welds is found to be incomplete, cracked, When a defect such as slag is trapped, the horn must be cut and re-welded.
(7) After the weld is inspected, the weld is inspected for its appearance and the inspection results are in accordance with Table 1.
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