Vehicle maintenance knowledge: introduction of two body welding - welding, maintenance - auto repair and maintenance industry

From the eighties of last century before the car rack Car body The popularity of the overall style body, body no longer has heavy steel plate frame, but a thin steel plate after the stamping, welding a whole. In structure, the body of the security design applications more and more cars front and rear crumple zones structure began. The role of energy absorption area is allowed deformation in the collision, to absorb the large amount of impact energy, protecting the structural integrity of the central body in order to ensure the safety of passengers. Repair to ensure energy absorbing plates to restore the performance, so in the second collision energy absorbing deformation in time to protect the safety of passengers. Therefore, in sheet metal welding work, some of the traditional approach is no longer suitable for welding Modern Body repair work has. Related Reading: Surfacing technology application in the automotive repair    Hyundai Sonata bond strap loose weld failures

Now, the body material has also been significant changes. Previously widely used in automotive body is low carbon steel. Because of low carbon steel is quite soft, in order to meet the design strength, the general use of thicker plates. Low carbon steel welding performance is better, welding heat and then cooled, low-carbon steel intensity is low, they are suitable for all kinds of welding. From the last century, decade, high-strength steel and ultra high strength steel has gradually been widely used in the body of. Now the body of high strength and ultra-high strength steel consumption has more than 70%. High-strength steel and ultra high strength steel are characterized by large amount of heat, otherwise the performance will change, and even its strength and low carbon steel will become the same. So heat welding is no longer suitable for modern vehicle repair welding operation.

As part of the strength will reduce the welding, arc welding and oxyacetylene welding applications have been banned in the modern car body welding repair operations. Now the application of the welding body mainly inert gas welding and resistance spot welding.

1, inert gas welding Present, arc welding in Vehicle Maintenance Station, repair shop has been widely applied, but in practical applications there are still many problems.

1. Body-specific selection of welding machine Many repair shop welding by the gas used mostly for industrial welding, special welding machine welding is not a body. Body Parts in the 1mm thickness of about welding current required is small and smooth, or welding is not prone to wear through or welding phenomenon. General industrial welder in the welding current is not stable, with the grid voltage fluctuation current fluctuations, this thin plate welding is very unfavorable.

2. Selection of welding consumables Now, some small repair shop car body welding wire selection is random, various grades of wire there. Body welding wire special grade should be AWS-ER70S-6, wire diameter 0.6mm, and many repair shops are using 0.8mm wire. 0.8mm welding wire for welding steel plate thickness of 1.2mm, 1.0mm body does not fit the overall style is about the thickness of the plates.

3. Protection of selected gases General repair shop selected to protect 100% of carbon dioxide gas. 100% carbon dioxide in the welding would have a greater penetration, when welding sheet metal parts prone to penetration or other issues. Therefore, protection should be used argon gas and carbon dioxide gas mixture, the ratio of argon 75%, the ratio of carbon dioxide, 25%, the mixed gas in the welding body panels best.

Welding in body should be provided in accordance with manufacturer Service Manual operation, each of the plates required by different welding methods. Frequently used welding methods have lap welding, butt welding and plug welding, welding on the body panels as small as possible to pay attention to current, low current welding can be used not to use high-current welding. Section to be used when welding welding, so that each weld can be fully cooled, in order to prevent deformation of plates.

2, resistance spot welding Manufacturing in the body is a lot of resistance spot welding applications, now also gradually began to repair applied. With the car material Developing Some ultra-high strength steel can not use gas shielded welding. Gas shielded welding heat will destroy the internal structure of high strength steel, it reduces the strength. So only use resistance spot welding to repair. There is also a resistance spot welding of the biggest advantages is subject to operator influence is relatively small, as long as the adjustment of good welding pressure, welding current and welding time, the welding quality of each solder joint will be no major deviations basic, relatively stable welding quality .

In resistance spot welding repair operations, should be noted that welding quality control. General resistance spot welding machine welding current can reach about 6000A, for the general body of the vehicle plates can be welded. But for some ultra-high strength steel, welding current may be achieved more than 9000A, or solder joints can not guarantee sufficient strength. Come from the outside because the plates are not welded well before doing resistance spot welding, to find the same material welding test. Trying to constantly adjust the welding pressure welding, current and time are three parameters, and then destructive test to verify whether the welding strength.

In welding, spot welding gas density and different. Gas welding requirements and the same as the original manufacture of the weld, while the resistance spot welding spot welding spot more than 30% of normal, and can not ever place in the original welding welding. Welding solder joint strength will be strengthened as the density increases. However, from the small joints to a certain extent, the strength is not only not increase, it will fall.

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