Abstract : High-energy beam welding has the advantages of heating concentration, less heat input, small welding deformation, small heat-affected zone, high welding precision, suitable for refractory metal, and highly sensitive metal welding. The application of laser welding, electron beam welding and plasma welding in various aspects of the automotive industry is analyzed.
Key words: high energy beam; automobile; welding
Foreword
The welding process is one of the three most representative processes in the automotive manufacturing technology (welding, painting, final assembly). In the automotive industry, traditional welding processes include manual arc welding, oxyacetylene welding, and manual spot welding. However, the conventional welding method has the disadvantages of poor weld quality, large deformation after welding, easy generation of pores, and difficulty in removing the weld slag. Instead, it is a highly mechanized CO 2 gas shielded welding and resistance spot welding. However, the defects in the spot welding process have a certain impact on the automotive assembly. These problems are often found in the assembly line assembly and need to be repaired, trapped, corrected for deformation, affecting the progress of the assembly line [1]. Especially in the aluminum alloy, due to the high thermal conductivity, low melting point and low yield strength of aluminum, it is necessary to use a large current, which makes the deformation caused by the resistance spot welding aluminum alloy product must be much more serious than the steel product, and also the welding quality monitoring belt. It is a big difficulty.
As the car develops in the direction of safety, environmental protection, economy, reliability and durability, the automobile welding production line is gradually developing towards full automation. In order to meet this requirement, national automobile companies are demanding efforts to improve vehicle quality and reduce costs while increasing production. As we all know, the premise of achieving automation is that the manufacturing precision of the parts is high, the welding deformation is small, and the appearance of the welded parts is bright, so the welding technology is required to be higher and higher. However, CO2 gas shielded welding and resistance spot welding are not suitable for the welding of automotive parts with high dimensional requirements and small deformation. Therefore, high energy beam welding is being widely used in the automotive industry. For example, General Motors has used more than 3,000 automotive parts for laser welding. According to the data, after the application of high-energy beam welding technology in the US automobile industry, cost accounting found that each car saved more than $100. High-energy beam welding provides high-speed welding, which results in reduced component quality, reduced manufacturing time, and reduced production costs.
High energy beam welding characteristics
High-energy beam welding is a technique for welding materials using a heat source having a power density greater than 5×108 W/m 2 , including electron beam welding, laser welding, and plasma welding. In the high-energy beam welding process, due to the high energy density of the heat source, the material to be evaporated evaporates in a very short period of time, creating a void through the thickness of the material to be welded, which is called a "keyhole" or "small hole". As the heat source and the material to be welded move relative to each other, the liquid metal continues to flow to the back of the bath to fill the pores, thereby forming a continuous and fully welded weld. The “small hole effect†is a distinctive feature of the high energy beam welding process, changing the way energy is delivered. Compared with general arc welding, there are obvious advantages:
a. It is basically unnecessary to open the groove and fill the wire when welding, and the penetration depth is large;
b. Heating concentration, less heat input, small welding deformation, small heat affected zone, fine weld microstructure, high welding precision, and high productivity;
c. Suitable for refractory metals, metals with high heat sensitivity, and welding between disparate workpieces of different sizes and sizes;
d. The specification parameters of the high energy beam welding can be individually adjusted, and the adjustable range is wide.
Application of high energy beam welding in the automotive industry
2.1 Application of laser welding
As a special process, laser welding can be divided into two categories: continuous laser welding and pulse laser welding. It has the advantages of high energy density, large penetration depth, good welding quality, small heat affected zone, no pollution and any corrosion, and easy automation. It has been widely used in the automotive field.
Continuous laser welding is mainly used in the automotive industry. According to experts' prediction, more than 50% of the resistance spot welding production lines in auto parts have been replaced by laser welding production lines. Many famous automobile companies in the world have built special laser welding production lines: General Motors has adopted 22 laser processing lines; Thyssen Steel's car floor welding production line; Volkswagen's gear laser processing line; Mercedes-Benz Automobile Factory Eight of the 18 plants have laser processing equipment installed [2].
The high-power CO 2 laser can be used to adjust the focus to 2.5m from the lens. The CNC system is used to manipulate the focusing mirror for precise rotation to form a scanning laser beam for welding the working surface of the body at a distance of about 2.5m. The power can reach up to 37kW. The maximum welding speed is 4m/s and the maximum acceleration is 100m/s 2 , and the weld position accuracy is ±0.5mm. In 1985, Toyota began to apply laser tailor-welded blanks, and laser welded five different thickness plates into a whole slab. After punching into the body side wall, it can save a lot of thick plates, omitting many machining processes, and No deflection or deformation. In addition, the top cover of the Mercedes-Benz 300SEL sedan also uses laser tailor welding technology, with outstanding results [3]. Italy Fiat is preparing to replace the traditional spot welding process with laser welding. The welding operation is also carried out by a robot mounted on a movable bracket. The robot has a laser selector with a laser power of 2.5 kW. According to researchers at KUKA, 600 laser welds on the body can be welded in just 12 minutes with a laser head. The laser-welded body has good integrity, which is beneficial to vibration reduction and safety [4].
Replacing resistance spot welding with laser splicing can eliminate or reduce the flange width required for resistance welding. For example, a conventional spot welding process requires a flange of 100 mm width, and laser welding requires only 1.0-1.5 mm width. The average car can be reduced by 50kg [5, 6]. Two pieces of 0.8mm steel stamping parts are welded by conventional spot welding, the average is 20 points min, the welding distance is 25mm, that is, the speed is 0.5m/min, and the laser welding speed can reach 5m/min or more. The use of laser welding technology not only reduces costs, but also greatly increases production efficiency.
Laser welding is also used for welding other components of automobiles such as clutches, transmission gears, chassis, and wheel rims. Ford Motor Company of the United States uses 4.7kW. The CO 2 laser welder welds the wheel disc rim with a 1mm thick steel ring and a welding speed of 25cm/min. The company also built a car chassis automation production line using a 6kW laser system. The entire production line is controlled by an electronic computer and requires only one operator. The Italian company Fiat uses laser welding of the synchronous gear of the car, which costs only one time more than the old equipment, and the production efficiency is increased by 5-7 times. Japan's auto electrical appliance factory uses two sets of 1kW laser welding igniters for the shaft in the dial plate assembly, with a daily output of 10,000 pieces, a penetration depth of 1.2mm and a welding speed of 3.5 pieces/s. The HPL industrial CO 2 laser welder developed by AFC in the United States has a power of 15 kW. Two gears for welding automotive rotating components, welding time is 1ms, concentricity is controlled within 0.05mm, more than 1000 components can be welded every hour [7]. In GM, laser welding operations are carried out by robots. Volkswagen AG of Germany uses CO2 laser to weld the car floor. On the floor welding line of Audi500 sedan, the welding line is fully automated, equipped with a weld monitoring system. The weld length is 1950mm, the plate thickness is 0.9mm, the heat affected zone is 1mm, the weld is bright and flat, and the weld strength is better than the base metal. The welding time is 20s.
In China, in order to meet the needs of high-speed laser welding of automobile bodies, Huazhong University of Science and Technology and Wuhan Iron and Steel Company use laser welding technology to weld the ultra-wide steel plates for automobiles. The research on the laser welding machine of the completed ultra deep drawing steel plate shows that the mechanical properties and deep drawing processing performance of the joint are equivalent to that of the base metal, and there is no deformation, and the welding speed is as high as 2.2-3.0 m/min. Changchun FAW and the Beijing Institute of Industry, Education and Research jointly developed the laser length welding technology for the new red flag car. Shanghai Leo Laser Equipment Factory successfully carried out laser welding of Isuzu's transmission gears [8].
3.2 Application of electron beam welding
Electron beam welding has the advantages of high energy density, strong penetrating power, high thermal efficiency, precision and easy control, and multi-function. It has been widely used in various industries in the industrial field, especially since the 1960s Japan Fuji Heavy Industries and the United States Since the automobile company took the lead in the use of electron beam welding gearboxes and flywheels, electron beam welding has been widely used in the automotive industry. Japan's Mitsubishi Electric Dorada supplies about 100 electron beam welding machines to the world every year, 80% of which is used in the automotive industry. More than 20 electron beam welders are installed in a gear processing workshop of Volkswagen AG. Currently, electron beam welding equipment has been introduced in almost all automobile manufacturers in the world. Electron beam welding is mainly used to weld the following components in the automotive industry: composite multi-link gears in manual transmissions; planetary gear transmissions and hydraulic transmissions in automatic transmissions; turbochargers; hydraulic containers for ABS brake systems; Gas generator for air bag system; rear axle and other parts such as valves, spark plugs, rocker assemblies, distributor cams, nozzles, pistons, clutches, rim seats, axles, connecting rod caps, moving conduits, oil retaining rings , crankshaft, axle, transmission bracket, brake band, flywheel, etc. According to foreign sources, at least 40 parts of the automotive industry use electron beam welding [9].
Next page
Chemical dosing pump,Solvent resistant gear pump,Food grade gear pump,magnetically coupled pump,leak free magnet drive pump
Suzhou Macxi Fluid Technology Co.,Ltd. , https://www.macxipump.com