From 1995 to April 18, 2007, China Railway has carried out six large speed-ups, which has increased the high-speed operation speed of passenger trains from l00h/h to 2001, and above m/h: at the same time, freight locomotives are also operated by single machines. The traction 5000t mentioned l0000t, or the two-machine traction 20000t, the speed increased from 80-80h/h to 1201; m/h, marking the Chinese railway really entered the era of "passenger high speed, cargo heavy load". In order to meet the needs of railway transportation "high speed, heavy load", it is bound to require rail vehicles to achieve lightweight, reduce their own weight and increase the load. The goal of lightweighting is achieved by using new materials with high strength, high specific strength and light weight. At the same time, the goal of lightweighting has also promoted the development and innovation of rail vehicle welding technology.
1. Train speed increase requirements for rail car auxiliary materials
In order to meet the needs of "high speed and heavy load", the two important components of rail vehicles - the material of the steering frame and the body of the car have undergone fundamental changes:
(1) The material of the bogie frame is changed from the traditional Q2358 and other low-grade steel to Q345C, Q3458, etc. If the frame of the locomotive or heavy-duty vehicle of the Qinghai-Tibet Railway is used, the Q4501 Pa Rl high-strength weathering with higher strength and better low temperature toughness is adopted. Steel or steel such as Q345E.
(2) The car body is also replaced by the corrosion-resistant stainless steel, lighter weight aluminum alloy and other materials (even all) to replace the traditional low carbon. It can be said that due to the light weight requirements of the development of "high-speed, heavy-duty" railways in China in recent years, non-ferrous metals such as aluminum-magnesium alloys are rapidly being squeezed into the traditional black material field of rail vehicles. The quality of the metal materials used in rail vehicles has undergone major changes.
2. Requirements for welding materials and equipment for train speed increase
In fusion welding, the welding material is matched to the choice of structural materials, welding methods and equipment. At the same time, with the improvement of the quality, reliability and quantity requirements of rail vehicles, high-quality and efficient welding methods have also been promoted and applied. The welding method has been from simple manual welding, T-work, submerged arc welding to c0-weld, M^G welding to fully automatic welding and robotic welding. In addition to Mlå˜, some units are in the process of friction stir welding (FSW).
Welding materials also range from carbon steel electrodes to low alloy, high strength, high toughness electrodes and stainless steel electrodes: from solid wire to gas shielded flux cored wire, self-shielded flux cored wire. It is precisely because the rail vehicle industry enterprises use efficient welding technology, fast updating welding equipment, efficient welding materials and high automation level to promote the research and development of welding technology such as welding materials.
3. Train speed increase requirements for welding technicians
The high-quality, high-strength, lightweight, low-cost and high-efficiency requirements of rail vehicles for the development of "high-speed, heavy-duty" railways, and the diversification of the use of metal structural materials, have raised more issues for welding technicians. Or / and challenge, need more welding technicians with systematic welding theory, familiar with factory welding, and practical experience, including welding structural designers, welding process designers, welding field service engineers and welding quality inspectors. The actual situation in the industry is: the welding structure design can not consider the process more, the process documents can not guide the actual welding on site, the problems found in the on-site process quality service can not be included in the welding structure design drawings and process documents in time. Therefore, it is recommended that:
(1) After graduation, the welding technician should first participate in the welding production in the factory workshop for about one year, familiar with the equipment and tooling at the production site, understand the welding process and process being executed, and master the actual skill and operation requirements of the welding.
(2) Thereafter, arrange the on-site welding process quality service for 3 to 4 years, and clearly understand the actual skill operation of the welder and the mastery and execution of the welding process, and cooperate with the welding structure and process problems existing at the site.
(3) After 4 to 5 years of welding production site, the welding technicians must be trained in a special welding training center (such as Harbin Welding Technology Training Center) according to the uniform requirements of IIW, and after passing the examination and obtaining the certificate ( For example, the international welding project 'J coin IWE, etc.) can be hired and independently undertake welding technology work.
(4) In the qualified welding technicians, the company arranges them in the positions of welding structure design, welding process design or welding process and quality service according to personal characteristics and enterprise needs. Such positions are not static and can be exchanged. Improve the overall quality of welding technicians.
(5) Enterprises should provide more platforms for the improvement of the capabilities of welding technicians in their regular work. For example, timely arrange welding technicians to study and inspect, and increase their understanding of the development of welding technology today.
Only in this way can we improve and standardize the quality of welding technicians, train a team of engineers who are familiar with the characteristics of welding processes and master the design of welded structures, and adapt to and meet the higher requirements of railway rapid manufacturing for rail vehicle manufacturing technology.
4. Welding quality control
After the railway transportation enters “high speed and heavy loadâ€, the safety and reliability of rail vehicles are particularly prominent due to the increase in speed and load, and the small quality problems in the manufacture of metal structures may lead to accidents and even disasters. Therefore, higher and more stringent requirements are imposed on the control of manufacturing quality, especially the control of welding quality.
Welding safety issues have received increasing attention from welders, which are prone to metallurgical imperfections or machining defects (such as cracks, pores, unfused, and poorly shaped shapes) that can lead to premature failure of the structure during service. Due to the large changes in structural application conditions, with the continuous emergence and application of new materials, new processes, and new methods, we believe that reliable and effective quality control methods (systems) will be re-evaluated in the past. Meet the requirements of today's rail vehicles Dora run. Therefore, we will refine or establish the corresponding welding quality control system from the aspects of personnel, equipment, materials, process methods and environment.
Enterprises that have passed the advanced quality system certification must also formulate their own manufacturing quality standards according to the product structure form, and prepare manufacturing technical standards such as the details of welding joints and strictly enforce them, in order to truly ensure the "high speed, heavy load" requirements of rail vehicles.
5. Technical innovation requirements
In order to meet the development needs of “high speed and heavy load†of rail vehicles, the rail vehicle industry should innovate from the following aspects:
(1) Establish an analysis system for rail vehicles, especially the dynamics and fatigue of the bogie frame, to achieve structural optimization and improve its safety and reliability.
(2) In the overall promotion of the use of inverter pulse control welding machine MIc, / M ^ G welding, through optimization, improve the structure and joint form of aluminum alloy car body, promote the use of advanced friction stir welding (FSW) method: The laser welding method is promoted on the stainless steel body.
(3) Pursuing the development of lighter metal-based new materials and their processing methods, such as the development of hollow extruded profiles that meet both strength and light weight requirements, and explore the application techniques of magnesium alloys in the body and parts.
(4) High-efficiency, high-quality and high-strength welding technology (such as core/double wire M^G welding) and robot and special machine welding technology are widely used and promoted in the body and bogie.
(5) Through the cooperation with international advanced rail vehicle enterprises, the introduction of international advanced personnel training and quality management system, the establishment of the company's own manufacturing technology standard system, the realization of the welding standard system innovation of aluminum alloy car body, steering frame and other products .
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