The latest progress of foreign welding technology
Resistance spot welding is considered as the most important connection process in the manufacture of automotive bodywork. Despite new technologies such as laser beam bonding and adhesive bonding, spot welding retains its solid position in automotive bodywork. Because many factors will affect the quality of spot welding processing, and spot welding quality standards are demanding, it is necessary to systematically check the quality of spot welding joints.
To do this, the past practice is to use a damaging test method for random testing. Due to the disadvantages of this method, for example, the test specimen may be destroyed or deformed, the test time will be long, the workpiece will be damaged and loosened during the hammering process, and the method of using the "gritzer" when using "zinc binder" Can not find the bonding point, so it is not suitable for modern manufacturing technology and cost accounting awareness. Here is a remedy - "point line ultrasonic testing method", in this way, during the welding process can be solder joint inspection.
"IQR System" is a new control technology for online quality testing and optimization in resistance spot welding
This method compensates for variations in control parameters such as changes in plate thickness, changes in coating thickness, and electrode wear loss, based on U-I characteristics. Due to its simplicity of operation, the IQR controller ensures stable and reliable high-quality spot welding and saves time and money.
In the field of resistance spot welding, one can clearly see the obvious trend of using servomotors in welding equipment. At the 2001 International Essen Welding Show, not less than 12 manufacturers demonstrated welding equipment that uses servo motor drive technology installed in micro spot welders, manual and robotic welding guns, and pedestal spot welders ). According to expert estimates, due to good welding quality and short welding cycle, pneumatic welding equipment will be replaced by servo-driven welding equipment more and more. In addition, some manufacturers show that the use of gas-cooled welding torch welding torch, the electrode requires force and welding cycle time requirements of the welding tasks have a wide range of applications.
Miniature spot welding with piezo-electric linear drive, ideal for resetting parameters and easy programming of moving routes. Because of its robust mechanical structure and the use of piezo-electric drive technology, the time required for positioning before and after welding is short. Therefore, you can seize the opportunity to shift from the work clean-up phase to the stage of work, savings welding power. Due to its robust construction and the extremely high dynamic performance of the drive system, the torch tip is more suitable for use in automatic welding installations and offers high welding efficiency.
Common welding guns for stamping and spot welding are challenged by the more demanding and highly productive robots in terms of motion speed and accuracy. In order to achieve a large working area and minimal bending, a new generation of robotic welding guns has been carefully designed and manufactured using extremely lightweight carbon fiber reinforced plastics (CFRP). According to the research results, a torch sample was made after careful testing and optimization. The recently developed structure has a very stiff, curved arm that is longitudinally stiffened and provides a strong reaction force that can even be offset by an on-line control. This application has promoted the potential for further development of better modern fiber materials for making lightweight structures.
Laser technology and the use of laser beam processing materials
Although Nd: YAG solid-state lasers with power above 12mm x mrad4kW have extremely high beam quality, it is not possible to achieve the CO2 laser range. It is due to the lower cost of CO2 laser and maintenance costs, it can be widely used.
For example, a 3kW laminar CO2 laser can work for about 40000h and a hourly cost of about 6 marks. This type of laser uses almost half the power of an ordinary CO2 laser and can almost achieve the same penetration depth even with a welding speed of 1.5 m / min. Nd: YAG solid-state lasers weld only half as fast as CO2 lasers when the penetration depth of the steel is 4 mm and the power of the laser beam is the same.
Only with three-dimensional multi-axis articulated arm robots, the total investment in using Nd: YAG lasers was lower than with CO2 lasers due to the simple beam delivery through fiber-optic Nd: YAG lasers. In long-distance welding, CO2 laser laser beam to focus through the lens, the scanner's optical system is free to locate the laser beam on the workpiece surface. The focusing lens is mounted on a motorized slide rail to determine machining points in a space of 1500mm × 1500mm × 400mm. The use of mobile mirror device, can be extended to interfere with the edge of the solder joints.
The laser beam welding and arc welding process can be combined to obtain a noteworthy welding process: CO2 laser beam and gas metal arc welding process combination. Using this technology, different levels of steel can be highly efficient welding. The purpose of this process is to determine the maximum allowable gap width, amax, for welding plates of different thicknesses. The gap width is 2 mm at a steel thickness of t = 5 mm, a width of 1.35 mm at t = 8 mm, and a width of 0.7 mm at t = 12 mm. The weld is formed by machining under gravity without the need for any melt support behind the weld. When transverse welding 20mm thick steel plates, the overlap width asssmax can reach 0.7mm without any technical problems. Other aspects of the best process include setting the speed of welding and wire feeding and the diameter of the wire.
People experimented with this combination welding process and demonstrated it in actual welding work. For example, at Meyer Shipyard several welds of 7.5 to 12 mm thick and 10 m long are successfully welded at a welding speed of 2 m / min. In the combined welding process described above, the addition of an arc combination can further enhance the benefits of the process, such as minimizing energy per unit length, increasing welding speed, and the ability to overlap the joint gap.
A compact, easy-to-handle "tool" is a diode-excited Nd: YAG laser and its high-quality laser beam. The thermal lensing effect limits the improvement of the beam quality. The further improvement is to further increase the beam parameters and input them into a 100 μm glass fiber, which results in a comparable beam quality to CO2 laser beams.
Here are more prospects for the development of disc lasers and laminar lasers. At the Laser Technology Expo 2001, HASS Laser Technologies demonstrated for the first time a prototype of a disk laser. The prototype laser power was 1.3 kW and the optical fiber diameter was 0.15 mm. Lamp-excited and diode-excited rod lasers have the problem of thermal lensing caused by the laser beam power, whereas disk lasers are practically no longer hot lens problems. Because disc lasers have a superior quality beam similar to that of CO2 lasers, their power can be calibrated by fiber-optic coupling, which is many times greater than the nominal power of a rod laser.
Diode-excited solid-state lasers with output powers greater than 4kW are decisive for the welding of aluminum alloys. The beam quality of these systems is particularly good, enabling instantaneous injection into optical fibers with a diameter of 0.4 mm. The focusing ability of a laser beam greatly depends on the cross-sectional area of the optical fiber. This shows that the potential of this new generation of solid-state lasers is that the "dot" diameter is smaller and the power density is higher. The high power density allows one to carry out welding in continuous wave mode. For example, it was first used to study various connections for small samples and small parts, such as butt, T-welding, and lap. Parts of the material are AlMgSi0.7 (thickness: 3mm) and AlMg3 (thickness: 1.6mm) aluminum alloy. High-quality bead shapes are only possible in purely continuous wave conditions. When using kilowatt diode-excited Nd: YAG lasers to weld aluminum, high reliability is achieved over a wide range of parameters.
The literature also describes a new method of affecting weld geometry and quality. This is based on the electromagnetic force in the pool, resulting in different pool flow and heat input. This will selectively change the shape of the weld, penetration depth, bead appearance and reduce stomatal formation.
When laser tubes are used to treat the inner surfaces of pipe, barrel and bushing, the properties of the material can be changed even on very limited specific surfaces. The laser beam provides a precisely controlled source of energy, applying energy at specific locations and times, usually with very little error, and therefore requires little or no post-processing. In industrial applications, the tool is fitted with protective equipment, such as pressure. Cabs and Cross-Jet to protect the optical system, cooling the absorbed laser radiation, plasma radiation and incidental thermal radiation.
The laser consists of the following components: laser adapter, substrate and laser head. The base body allows the laser to be mechanically connected to a defined processing system and to the media being processed. Laser light is provided to the laser head optically within the substrate. If necessary, you can also install a device with the media brush movement, the laser head for rotational movement. The laser head is equipped with a central beam-forming element (coated copper mirror) and a shielding gas or process gas nozzle. A Nd: YAG laser with a power of 2 kW is also connected to a hardened unit for long guides. The integrated mirror set focuses the beam to 3mm × 5mm at a working distance of about 60mm. High-alloy steel bushings of φ60mm and depth 600mm can be hardened using a 3kW power solid-state laser. In addition, the optical system developed for internal hardening of pipes has a rotating laser head that can be operated on a stationary engine block for hardening the cylinder bearing surface of a gray cast iron engine body of a truck diesel engine.
A newly developed welding torch system for plasma arc welding, the use of reverse polarity electrode and the selection of welding current 100 ~ 200A can be cost-effective welding aluminum parts, welding quality is good. After a variety of aluminum-magnesium alloy welding tests show that: welding 2 ~ 8mm plate, you can use the melt-in and keyhole welding technology.
Plasma arc welding using variable polarity keyhole technology for welding round welds, such as AlMg3 pipes, flanges, and differently shaped parts made of GK-AlSi7Mg cold-cast alloys, enables the use of 8mm wall thickness materials No groove butt welding connection. The use of a newly developed special gas control system allows for the perfect welding of the circumferential weld. Since only pores are created on the side of the casting, atomic hydrogen content of the molten metal in the casting is to be determined. If the molten metal in the casting has a hydrogen content of less than 0.3 mL / 100 g, the welds will produce fewer pores. The total length of the weld to be repaired by this method can reach 39m, accounting for 27.2% of the entire weld length.
In research and development of the most modern power and control technology, the use of plasma arc welding technology is the best quality, cost-effective, repeatable connection process. In addition, by adjusting the current, to ensure that the thick plate plasma arc butt joint welding keyhole sensor system, the conductive pool support and welding plate insulation, and through the charged frame when the plasma arc penetration current measurement, and with Move.
This new process has the following characteristics compared to TIG welding:
(1) Advantages of a specific process when using plasma arc welding are not only manifested mainly in the range of plate thickness of miniature plasma arc welding, but also in the use of keyhole technology.
Applications include: surfacing, spraying and welding. By using low pulse welding current with adjustable frequency, plasma arc welding can control the amount of arc energy in a better way and reliably and simultaneously monitor the performance of various setpoints with modern control systems. The transistor's welding power supply, such as the AUTOTIG series, can be accurately operated in accordance with the specifications.
(2) The use of powder plasma arc welding of thin plates and pipes, with welding speed, heat input and small deformation advantages.
(3) Plasma arc welding, the key hole technology advantages are also clearly demonstrated in the plate thickness of 10mm of material welding.
Contact: David Piao
Address：No.99 North Wusongjiang Road, Kunshan, Suzhou, Jiangsu, ChinaPR 215300