In recent years, with the improvement of China ’s railway lines and the increase in transportation capacity, domestic railway locomotives have entered a period of rapid renewal. During the entire “13th Five-Year Plan” period, domestic railway locomotives
The market demand for vehicles will continue to rise. At the same time, infrastructure connectivity is a priority area of the "Belt and Road" construction. The release of the "Belt and Road" has further promoted the development of the rail transportation industry. In order to meet the needs of the leaping development of the rolling stock industry, the domestic railway passenger car and urban rail vehicle manufacturing industry is also actively carrying out comprehensive technical equipment transformation and product technology upgrades. Laser cutting and laser welding are one of its key technologies in manufacturing.
During the "Twelfth Five-Year Plan" period, due to the poor sealing performance and large welding deformation of stainless steel car bodies, the country chose to use aluminum alloy car bodies with higher production costs and relatively low safety performance when vigorously developing high-speed rail passenger cars. As China ’s demand for rail vehicles further increases during the “Thirteenth Five-Year Plan” period, the advantages of stainless steel car bodies in terms of manufacturing costs will be valued. Different from the traditional welding technology, because the laser has excellent transmission and focusing characteristics, it can concentrate all the energy in a small area. Therefore, the laser welding is highly concentrated with high speed, high precision, high quality, low distortion, The unique advantages such as easy control are considered to be one of the most promising welding methods in the 21st century.
Laser processing technology is the most important manufacturing technology method in the locomotive manufacturing industry in recent years, and it has greatly promoted the improvement of locomotive manufacturing technology. The Huagong Laser Intelligent Equipment Business Group will innovate and upgrade the laser cutting technology accumulated over the years, launch efficient and professional solutions for the locomotive manufacturing industry, and push the railway locomotive manufacturing technology to a new era.
Comparison of traditional welding methods and laser welding
Laser welding of stainless steel body
The use of stainless steel body is becoming more and more widespread:
● The United States and France began using stainless steel to make train bodies as early as the 1930s.
● The Hyogo Plant of Japan's Kawasaki Heavy Industries Co., Ltd. has officially introduced laser welding in the welding of stainless steel railway vehicles, which has improved operations by 20% -30% and reduced costs by 20% -30%.
● In July 2003, Changchun Railway Passenger Car Co., Ltd. developed the first stainless steel urban rail passenger car. The car uses a drum body as a whole spot welding structure, which indicates that China's urban rail car technology has realized the transition from carbon steel body to stainless steel The successful leaping of the car body.
● Domestic Changchun Vehicle Factory, Sifang and Zhuzhou Electric Locomotive and other units have carried out preliminary research on laser welding technology for stainless steel car bodies and have begun practical applications.
The welding performance of stainless steel is mainly restricted by the following two physical properties :
● Large thermal expansion coefficient
The thermal expansion coefficient is about 1.5 times that of carbon steel, making the same heat during welding, its deformation is much larger than ordinary steel.
● Low thermal conductivity
The thermal conductivity is about 1/3 of ordinary carbon steel, so the heat generated by welding cannot be quickly dissipated, and a large amount of heat is concentrated in the weld area.
This shows that stainless steel welding is suitable for welding with a small heat input, which is laser welding.
Solutions we offer
1. For the typical joints of stainless steel car body (butt, lap, corner joint), carried out laser welding process optimization and joint performance evaluation work, and developed laser welding process specifications (WPS);
2. Demonstrate the feasibility of laser welding of the main components of stainless steel body (side wall, door frame).
Laser-arc hybrid welding
● High adaptability: It is beneficial to reduce the sensitivity to gaps, centering and misalignment, improve weld formation, reduce the number of blowholes and control of metallurgical cracks;
● High efficiency: the auxiliary heating of the arc can increase the speed of laser welding; the laser guides the arc to achieve high-speed welding;
● Increase the penetration: get a larger single-pass welding penetration;
● Low cost: The arc of lower current laser combined with a certain current can obtain the welding penetration of high power laser.
Conventional CO 2 laser cutting machines can only cut stainless steel with a thickness of less than 12mm and aluminum alloy with a thickness of less than 8mm. Using the SuperCut cutting technology of Huagong Faili Company, it can easily cut 20mm stainless steel and aluminum alloy.
● 亮面切割：毛刺极少，粗糙度小，更好的切割质量和垂直度。 ● Bright surface cutting: Very few burrs, small roughness, better cutting quality and verticality.
多样化的板材选择：标准切割模式和SuperCut模式任意切换，可以实现仅用一台设备就能对不同厚度不同材料实现高质量切割。 ● Diversified board selection: Standard cutting mode and SuperCut mode can be switched at will, which can realize high-quality cutting of different thickness and different materials with only one device.
智能切割系统：切割气体自动控制、自动调焦、可扩展自动上下料机构及料库单元。 ● Intelligent cutting system: automatic control of cutting gas, automatic focusing, expandable automatic loading and unloading mechanism and storage unit.
Stable and reliable performanceCan meet the needs of mass production and processing
Low cost of useNon-contact machining, no tool wear
High processing efficiencyBeam energy and moving speed are adjustable, can realize a variety of processing
Good product qualityThe welding point is smooth and beautiful, the welding seam has high strength and toughness.