In the introduction of glass and metal in front of the welding, the reader has been introduced to the wetting, diffusion of the basic knowledge. Today we introduce the knowledge of dissimilar bonding (welding) to the readers. Only when the problem of dissimilar connection (welding) is clarified and resolved is it possible for us to formally enter the topic of glass and metal welding.
Glass material is widely used because of high temperature wear resistance, corrosion resistance, insulation, oxidation resistance and other characteristics, but the glass itself low ductility, impact toughness difference is limited in the engineering application. Therefore, glass and metal combination of glass and metal composite performance of the double metal composite connector came into being, and widely used in microelectronics packaging, batteries, instrumentation, solar vacuum heat pipe, composite materials and other fields, so the study of glass and metal sealing Significance. Glass and metal sealing methods are many, of which the most mature theory to match the matching seal, matching seal is in the metal before the pre-oxidation treatment, the metal surface to form a layer of appropriate thickness of the oxide layer , Then the metal and glass in the furnace for a certain period of time heating and cooling to room temperature, but the match to be sealed in the furnace heating and cooling so the production cycle length. However, the laser has a very high energy, non-contact local fast heating to achieve rapid cooling, but also to achieve the shape of the joints more complex sealing devices, so the application in the sealing area is also growing. Glass and metal welding are different types of materials, so their welding is heterogeneous welding. This is why we introduce the dissimilar welding. In the follow-up article, we will gradually introduce the glass and metal matching sealing (welding) and laser welding.
What is a heterogeneous connection
Due to functional requirements or limitations of the prior art, it is often difficult to achieve a heterogeneous multifunction project without welding (connection). Therefore, in the actual production is often used in combination and often welded (connected) to achieve the design of this technology. In order to achieve different functions and utilities, different properties and functions of the material welded (connected) together, welding (connection) is often an indispensable process. To this end, a full understanding and mastery of this technology has become a key manufacturing problem. Different scholars from different angles on the welding (connection) for a different definition. Messler sees "a process of making parts of different parts into one whole." According to this definition, our stacked wood, rural wooden structure of the house and furniture, are welding (connection) areas. Scholar Campbell argues that "assembling different parts into a single component is a process that is more complex than a single individual, and assembly is also a process of welding (connection)." This definition further confirms that stacking wood is in fact heterogeneous welding (joining). Different scholars have given different definitions, but no matter what the definition of scholars, it can be clear is that "welding (connection)" is a combination of different components together to form an integral unit of the activities or processes. The second point is clear that "welding (connection) is the process of combining components or structural elements." But the purpose of the combination must be in order to achieve or achieve a certain function, and this function must be a single component can not be achieved. Based on the understanding of the above definition, the following three ways can be considered to achieve welding (connection) approach:
(1) To connect (a connection) by mechanical means;
2, chemical connection: through chemical bonding (reaction) to achieve welding (connection);
3, the hot connection: through the hot melt process to achieve the welding (connection).
Why heterogeneous connections are used: Due to the need for more options, such as light weight and efficiency, different materials are often connected together in order to achieve versatile engineering structures and efficiencies. Such as the topic of the glass and metal welding (connection). Well known in the automotive industry, aerospace industry, textile industry (metal and nameplates on clothing), tool industry, medical implants, electrical and marine engineering and other fields.
In fact, different types of welding in ancient times also have, such as
5000 years ago with tin brazing silver display (ancient Egypt)
5000 years ago with tin brazing silver silver body silver handle (ancient Egypt)
Pipes Welded with Silver Solder 5000 Years Ago (Ancient Egypt)
4000 years ago with gold brazing brazing of the box (ancient Egypt)
5th century BC with tin-lead material embedded in the crown of jewelry, etc. (China)
In 79 AD, buried in the Pompeii city by volcanic eruptions, there was a lead-in plumbing pipe (Roman) brazed with tin solder.
In the history and culture as the stars of China, according to historical records:
The Han Dynasty. Ban Guzhuan "Han":
Hu Tong tears like tears, you can also sweat gold and silver are also used by today's craftsmen. (Sweat that is welded).
Song. Song Yingxian essays "Heavenly Creations":
Small copper brazing with copper at the end of a large braze is trying to play a powerful hammer and strong together, over the ages for a long time, and finally not Kennedy. (Small brazing that is brazing, large brazing for welding).
The Ming Dynasty. Fang Yizhi "physical small knowledge":
Welding to borax copper together, if the juice with silver Tong Tong, firm as stone. This jade knife handle and the like welding flux, plus silver one point, then never off. Try to round the mouth point of welding medicine in its corner, the drug from the walk, the week of the ring, also a strange also.
Application of dissimilar welding (connection)
The more common example is the Boeing 787 aircraft using composite materials as the basic material of its aircraft shell, the material from the 20% Al, 15% Ti, 10% steel and 5% of the other materials. In the modern automobile industry, in order to lose weight, including ceramic and metal welding (connection), beam using steel, as well as aluminum alloy produced more parts, such as aluminum alloy piston and aluminum engine block. EU-FP6 projects in the development of the car is the use of Al, steel, Mg, glass fiber and other different materials.
So what is heterogeneous material, can be simply defined as "materials or materials together, the more difficult to achieve welding (connection), difficult to achieve welding (connection) because of their chemical properties or physical properties caused by different" .
Due to the differences in chemical properties, thermal and physical properties (such as coefficient of thermal expansion, toughness, fatigue, fracture mechanics behavior, elastic modulus, etc.), dissimilar materials will not only affect the welding process, but also affect component service When the performance. Such as galvanic corrosion during service, different coefficients of thermal expansion and other effects will affect the component's service performance.
In order to solve the above problems, in product design and welding (connection) process practice, we must fully consider and consider as much as possible how to solve this challenge. "The difference between the dissimilar welds (connections) must be sufficiently narrowed down by the choice of different materials or other means to narrow the differences between the different materials," says Schiller, Messler. Because the different materials in nature, such as the atomic level of the structure, microstructure, microstructure and properties of the original is different.While the combination of a variety of materials, reduce the difference between different materials becomes more difficult".
As the welding (connection) classification is more, we are here to introduce the glass and metal welding (connection), as shown in this unrelated, do not do too much here.
Glass and metal connections, there are four commonly used in the main form:
1. Mechanical connection: This is the case for ceramic sockets commonly used in homes.
2. The use of sealant or seal: home use the door and window glass is the case.
3. The use of high-temperature sintering approach: We use light bulbs is the case.
4. We have mentioned the laser welding method: This is a new, advanced welding methods, in the laser industry, laser gas discharge tube, long life is the use of laser glass and metal welding.
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