The 21st century is the era of rapid development of modern science and technology, and laser technology as the current development of the times in which people are the focus of most attention, it plays an important role in various fields. Laser welding technology will be applied to the laser welding, it began in the 1960s and was quickly applied to various industrial sectors, becoming the product of the industrial and technological progress, the technology in the weld width, quality, welding speed, distortion, efficiency respect, control of welding, positioning accuracy and so there were other fusion welding technology incomparable advantages, has been widely applied to aerospace, automotive, marine, biomedical and other fields.
Laser welding is a materials processing technology, the use of a laser beam highest atomic stimulated emission principle, the working substance (lasing material) is excited to produce a good color, strong direction, a high intensity laser beam, focused by energy density of up to 1013W / cm2, and even more in a short time the laser is absorbed by the metal and then converted into heat, eventually melting metal after cooling and crystallization to achieve a metallic material is connected to the thousandths of a second.
A laser welding classification
Press the laser output energy in different ways, laser welding, laser welding can be divided into continuous and pulsed laser welding. Continuous laser welding in the welding process is the formation of a continuous uninterrupted weld appearance, and the pulse laser welding since energy input to the weld surface is intermittent not continuous, so that each pulse is applied to spot welding the workpiece surface forming a circular pad, different morphologies can be obtained according to the change of its laser weld parameters. Different spot power density laser focus, laser welding can be divided into thermal conductivity welding and deep penetration.
1) laser welding thermal conductivity
Laser thermal conductivity welding spot power density in the lower surface of the workpiece, generally less than 105W / cm2. The laser energy is delivered to the welding surface of the workpiece so that the metal surface is heated to the melting point and boiling point between. Metal surface will absorb light energy into heat energy so that the surface temperature rising metal melts, then the thermal conduction heat transfer to the metal, so that the melting area gradually expanded to form a solder or weld cooling, which species principle is similar to TIG welding (TIG), is called the thermal conductivity welding.
2) Laser Welding (welding holes)
When used as a laser power density of the metal surface is greater than 105W / cm2, the role of high-power laser beam to the metal surface causing localized melting and the formation of "holes", the laser beam through the "hole" deep into the bath inside, while the metal in front of the hole melted molten metal flow behind the bypass hole is formed after re-weld solidification.
Second, laser welding characteristics
With the research and development of high-power lasers, laser welding technology has been widely applied to many fields, mainly because it has the following characteristics:
1) deep depth, speed, small deformation
When using laser welding machine connected to the workpiece, the workpiece is connected almost no gap welding, and welding aspect ratio, small deformation after welding, heat affected zone and high accuracy.
2) a simple and flexible means of welding, soldering can be performed at room temperature or special conditions, less demanding on the welding environment.
3) power density
Laser welding machines with considerable depth of penetration, high power density, weldable refractory materials, such as titanium alloy.
Third, laser welding processes
1, welding sheet and the sheet. Including welding, welding end, central through fusion welding, fusion welding center perforation four kinds of process methods.
2, wire and wire welding. Including wire and wire welding, cross welding, parallel lap welding, T-welding and other four process methods.
3, wire and block element welding. Laser welding can successfully achieve wire and massive size of the connector elements, block elements may be arbitrary. It should be noted in welding geometry filamentary element.
4, welding of different metals. Welding different types of metals to solve the solderability and weldability parameters. Laser welding between different materials that only certain combinations of materials possible. Laser soldering connection some elements should not be used laser welding, but using a laser as a heat source, the purposes of soldering and brazing, laser welding also has the advantage of. Using brazing different ways, which is mainly used for laser soldering printed circuit board welding, sheet-like element is especially useful in assembly technology.
Fourth, laser welding applications
Laser welding has the advantage that the laser welding can be used for large aircraft splicing of skin, stringers and skins and body connection accessories (such as pelvic fins and wing box) assembly. In recent years, laser welding techniques are used to replace conventional rivets aluminum airframe manufacturing, to achieve nearly 20% of the airframe weight, strength increased nearly 20%. The laser welding technology used in aircraft fuselage, wings and all connections within the separator and the ribs, instead of traditional riveting process. All aluminum alloy inner baffle Airbus A340 aircraft are laser welding, reduce body weight, reduce manufacturing costs, the technology subsequently extended to A318, A380 aircraft. At the same time, manufacturing inlet, bellows, pipelines, conduits and shaped variable cross-section of the closure and other thin-walled parts are also widely used in laser welding technology.
Large-scale development of automobile manufacturing has become an important trend in the automotive industry, the laser welding technology is the most successful, the most obvious benefit of a connection technology. Laser welding machine used in a growing number of automotive structural parts, for example, an important component in the door panels, bumpers and pillar, as well as a front side member, damper mount and beams and the like. Widely used in laser welding technology makes welding work efficiency aspects greatly improved, so as to optimize the car manufacturing process efficiency. This rise of the welding technology in the 1980s, the use of laser welding technology to the car manufacturing, and laser welding technology offers high efficiency, high quality, low cost, security has become the world's leading automobile manufacturing technology in the United States. With new magnesium, aluminum and other materials used in the manufacture of automobiles, for welding technology requirements have become more sophisticated, laser welding technology can not only reduce the magnesium produced aluminum compound and prolong life, to meet the functional requirements, but also take into account aesthetics.
The mid-1990s, as a heavy industrial laser tools are applied to shipbuilding. With the gradual deepening of the large ship manufacturing process changes (from riveted into welding), welding process, welding method, welding equipment also will be changed, namely the traditional gas welding, arc welding has gradually been replaced by laser welding, in addition to the ship shipbuilding design and materials with the progress of shipbuilding technology and undergoing significant changes. Some large shipyards in Europe began to introduce a large number of laser processing technology, including laser processing technology is high power laser welding technology (power> 10kW) and laser cutting technology, while developing a large number of high-power fiber laser welding machine. Ship made up of many parts, suitable for laser welding site is mainly ship decks and bulkheads.
In biological tissue, the use of laser welding technology will be linked with the success of the fallopian tubes of blood vessels to promote the success of welding technology and worldwide promotion of various biological tissue; in neurological, laser wavelength measurement, the success of the common bile duct and other welded parts show laser welding technology in this regard has played a greater effect; in terms of laser welding suture having a consistent speed and no abnormal healing response characteristics.
Laser welding technology as a strong Effectiveness sophisticated welding technology, with its unique advantages in the development of various fields have achieved a more spectacular results, with the increasing development of technology and research efforts believe it the role will be able to develop more in the field, so as to promote industrial and social progress.