I. The Status of Production and Distribution of China's Auto Industry

China's automobile industry was born in 1953. It has been 60 years since Chairman Mao Zedong wrote the inscription of "Commemoration of Foundation of the First Automobile Manufacturing Plant”. The automobile industry has now become one of the pillar industries of the Chinese economy. From the perspective of automobile production and sales, the rapid development of China's auto market has changed the world market structure. The annual production and sales of China's auto market has risen rapidly from 7.28 million units and 7.22 million units in 2006 to 22.12 million units and 21.98 million units in 2013. As shown in Figure 1. From the perspective of total industrial output value, from 1998 to 2012, the total output value of China's automobile industry increased from RMB 278.73 billion to RMB 3.58 trillion, and its proportion of the China's total industrial output value increased from 4.1% to 4.5%.

  Fig. 1 China's automobile production from 2006 to 2013

The data shows that the top three provinces in terms of automobile production were 2,542,909 in Guangdong Province, 2,342,273 in Jilin Province, and 2,268,857 in Shanghai, accounting for 10.65%, 9.81%, and 9.50% of the total output of the automobile industry of China, respectively. The production of these three provinces accounted for 29.36%. As shown in Figure 2.

       Figure 2 China's auto industry production concentration in 2013

II. Characteristics of China's Auto Industry

1. Development relying on the joint venture model

After the reform and opening up, China officially listed the automobile industry as a national pillar industry, and proposed the policy of introducing foreign capital and technical strength and developing the automobile industry in the form of joint ventures, and determined the development principle of “high starting point, large quantity, and specialization” for the automobile industry. Since then, China's automobile industry has embarked on the road of joint venture development. Volkswagen, Peugeot, Ford and other large foreign auto companies have begun to connect with domestic auto companies, and some joint venture companies have been established one after the other.

2. Self-owned brands develop rapidly, but there is still a gap compared with international standards.

Compared with well-known foreign brands, China's self-owned brand cars still have disadvantages including low technical level, lack of concentration of production enterprises and models, low brand influence and low added value of products.

3. Consumption structure mainly based on passenger cars

Around 1980, the annual production of China's cars was only about 5,000 units. Most of the car market demand can only be solved by import. After determining the policy of developing the automobile industry by joint venture, China took the cars as the development focus. In 2005, the sales of passenger cars in China exceeded the commercial vehicles for the first time. In 2014, the production of passenger cars in China was close to 20 million. From 2006 to 2014, the average growth rate of China's passenger car market was around 20%, which was higher than the average growth rate of commercial vehicle market which was around 9%.

4. Passenger car consumer market is dominated by small-displacement models

With the economic development and the improvement of residents' living standards, the consumption structure of China's automobile market has gradually changed, and the consumption attribute of automobile products has gradually changed from the former luxury goods to the general consumer goods. As a family car, considering the factors of disposable income level and fuel consumption of the residents, the structure of passenger car tends to be lightweight and small-displacement.

5. Localization of auto parts

The automobile industry is characterized by globalization. Since the 1990s, the auto parts industry has formed a global production and global purchase system, and vehicle manufacturers have implemented unified purchase of auto parts on a global scale in accordance with certain principles.

III. Automobile Lightweight

1. The importance of automobile lightweight to the development of modern automobiles

1.1 Automobile lightweight can effectively save fuel consumption and reduce displacement

According to the introduction of relevant information, under normal circumstances, for each 1 kg of vehicle weight reduced, the 1 L of gasoline can give the vehicle an extra 0.011 km, which means that the vehicle can save 0.7 L of gasoline per 10,000 km in operation. In the meantime, vehicle weight reduction not only reduces fuel consumption, but also reduces carbon dioxide emissions in the atmosphere. For each 50% of vehicle weight reduced, the CO2 emissions will be reduced by 13%. Meanwhile, it also reduces the emission of other hazardous substances, such as nitrides and sulfides, which also plays a significant role in improving the quality of environment.

1.2 Lightweight of vehicle can improve the driving performance and safety performance of the vehicle

Reducing the mass of vehicle can improve the driving performance of the vehicle. According to US Aluminum Association, for each 25% of vehicle weight reduced, the time required to accelerate the vehicle to 96.56 km•h - 1 can be reduced from the original 10 s to 6 s. [6]; Reducing the mass of vehicle can also reduce the load of power and power transmission system simultaneously, enabling the vehicle to perform the same or better at a lower traction load condition.

2. Application of aluminum alloy materials in modern automobile production

The automobile industry in European and American countries is very developed, and it has long been focused on the energy conservation and emission reduction of automobiles and the important role of aluminum alloys in lightweight of automobiles. As the first manufacturer that truly brought aluminum into the automobile lightweight mass production stage, Audi produced the world’s first all-aluminum vehicle in 1994. Table 1 lists the composition ratio of materials used in automobiles for world automobile industry in 1980, 1990, 2000 and 2010. From Table 1, the proportion of steel, metalloid and other materials in the automotive industry has been declining over the past 30 years; on the contrary, the proportion of aluminum has increased from 4% in 1980 to 29% in 2010, and there is an upward trend that may partially replace the basic position of steel in the car industry.

Table 1 Changes in the composition of automotive part materials (%, mass fraction)

3. The aluminum alloy used in automobiles can be divided into cast aluminum alloy and deformed aluminum alloy.

The cast aluminum alloy is mostly applied in automobiles and can be divided into gravity castings, low-pressure castings and other special casting parts. Deformed aluminum alloy include sheets, foils, extruded section, forgings. The variety of aluminum alloy materials used in the automotive industry around the world is generally the same. Its variety composition: castings account for about 80%, forgings account for 1% to 3%, and the rest are processed materials. Table 2 shows the main component system of cast aluminum alloys for automobiles while

Table 2 shows the main component system of cast aluminum alloys for automobiles

Table 3 shows the main components of deformed aluminum alloys for automobiles.

IV. Development of New Energy Vehicles

New energy vehicles include hybrid electric vehicles (HEV), pure electric vehicles (BEV, including solar vehicles), fuel cell electric vehicles (FCEV), hydrogen engine vehicles, vehicles powered by other new energy sources (such as high-efficiency accumulator, dimethyl ether), etc. Among them, hybrid vehicles, pure electric vehicles and fuel cell vehicles are the three mainstream development directions of China's new energy vehicle industry.

In 2012, China manufactured 12,552 new energy vehicles, including 11,241 pure electric vehicles and 1,311 plug-in hybrid vehicles. In 2013, China manufactured 17,500 new energy vehicles, including 14,243 pure electric vehicles and 3,290 plug-in hybrid vehicles. In 2014, China manufactured 17,500 new energy vehicles, including 48605 pure electric vehicles and 29894 plug-in hybrid vehicles. The specific situation is shown in Fig. 3.

V. Welding in Vehicles

Fig. 3 Statistical Table for Output of China New Energy Vehicles in 2012-2014 (Unit: Vehicle)

Welding is an important processing step in the automotive manufacturing chain. The six major assemblies of the engine, gearbox, axle, frame, body and compartment of the car are inseparable from the application of welding technology. Various welding methods has "covered" the forming process of parts from white body, frame, chassis to suspension system,

Brake system, steering gear, clutch, transmission to wheel rims. All kinds of existing welding unit technologies and process methods, such as electric resistance welding, gas shielded welding, stud welding, brazing, friction welding, high energy beam welding, etc. have been applied.

1.1 Welding processes used in automobile industry

Automobile is one of the industries with the most extensive welding applications and the welding processes used are various. The main processes are shown in Table 4.

1.2 Application of main arc welding process application method in vehicle industry

At present, in the welding of structural parts of automobiles, the arc welding process is often applied, and the widely used ones are CO2 gas shielded welding, gas metal arc welding (GMAW) and tungsten inert gas welding (TIG). The MlG/MAG method is a commonly used welding method in automobile industry. Its main advantages are high ratio of welding area, low cost of electrode or welding flux, high utilization ratio of filler metal, and it can achieve semi-automatic or full-automatic welding with simple operation and low technical requirements for its operation. It can generate welding arc on time and reduce the generation of fume. It can be seen that the high-speed high-quality build up welding and the MIG/MAG arc welding with low cleanup effort are key to the ideal welding method.

The main automobile parts using MAG welding method are shown in Fig. 4. Spot welding is mainly used for body parts, and different from MAG welding, it is often used for high-strength foot parts and complex-shaped parts.

  Fig. 4 Representative automobile parts suitable for MAG welding.

1.3 Welding process for welding automobile parts

At present, there are many welding processes used in automobile manufacturing, such as CO2 gas shielded welding, electric resistance welding, argon arc welding, arc welding, laser welding, etc. In these welding processes, CO2 gas shielded welding and electric resistance welding have the characteristics of large production volume, small welding deformation, high efficiency, easy operation, high degree of automation, low energy consumption, etc., which are suitable for welding of automobile body sheet covering parts, carriages, frames, and axles.

① CO2 shielded welding is mainly used for welding the auto skin, rear axle, frame and carriage.

② Resistance welding spot welding process is a kind of electric resistance welding, which has the advantages of quick operation and high production efficiency. It has become the main welding process for body-in-white manufacturing. It has been widely used in automobile manufacturing and is also the main welding method [2] of high-strength steel for automobiles. In modern automobile manufacturing, the body-in-white automobile has about 4,000 to 5,000 solder joints.

③ The laser welding of auto sheet has the advantages of high energy, high speed, small heat affected zone and high weld quality, high welding precision, small deformation of parts, and can significantly improve the strength and rigidity of the auto body. It has been widely used in the manufacture of body-in-white auto.

④ Metal-Inert Gas (MIG) brazing, for galvanized sheet, due to the low melting point and boiling point of zinc, when using MAG fusion welding, the galvanized layer is easily vaporized and oxidized under the action of arc, to form defects such as pores, incomplete fusion and cracks. MIG welding can be used for arc brazing of the coated sheet, select the appropriate protective gas, optimize welding parameters, reduce heat input, reduce zinc volatilization, and reduce internal stress, so as to reduce the deformation of the sheet.

1.4 Application of aluminum alloy welding technology in automobile manufacturing

Aluminum alloy used in automobiles can be divided into cast aluminum alloy and deformed aluminum alloy. Cast aluminum alloy are mostly applied in automobiles, accounting for more than 80%, which is divided into gravity castings, low-pressure castings and other special casting parts. Deformed aluminum alloy include sheets, foils, extruded section and forgings. Although there are certain differences in the variety of industrial aluminum alloy materials in the world, they are generally the same. Its variety composition: castings account for about 80%, forgings account for 1% to 3%, and the rest are processed section.

There are many types of aluminum alloy welding technology, in addition to DC pulse MIG welding technology, there are the following: 

1. AC TIG aluminum welding

The better penetration and removal of oxide film are the basic characteristics of positive and negative tungsten gas shielded welding respectively. The tungsten gas shielded welding using AC power supply balances these two characteristics. In the positive half cycle, the arc effectively breaks the aluminum oxide film adhered onto the surface of the material, while in the negative half cycle, the material is fused.

2. AC pulsed metal argon-arc-welding (AC PMIG) 

3. Argon tungsten arc welding (TIG)

Although the thin sheet can be welded, the welding speed is low and the deformation is severe. When the pulsed argon-arc welding is DC and the welding wire is positive (DCEP PMIG), although the arc is stable, the metal droplet transfer is easy, but the arc penetrating power is strong and the weld penetration is large, it is not suitable for welding of thin sheets

4. Variable polarity plasma arc welding of aluminum alloy (VPPA)

5. Laser welding of aluminum alloy

6. DC pulse MIG welding is a widely used and efficient welding method.

Although the AC power supply can effectively remove the oxide film, at the time of current zero, the arc is difficult to ignite again, which destabilizes the arc stability. Therefore, a DC reverse polarity power supply is usually used. The P-GMAW method is used for the welding of the aluminum frame of Audi A8, see Fig. 5. Low-frequency modulation pulse MIG welding method (double pulse) has also been successfully applied to the welding of motorcycle aluminum frames.

Fig. 5 The P-GMAW method is used for the welding of the aluminum frame of Audi A8

1.5  Needs of automotive industry for welding automation and welding power supplies

1.5.1 Requirements by the automotive industry for automation

① High-efficiency, high-speed, intelligent welding is the development direction of modern welding technology, and is the only way to achieve modern welding. Welding robots play an important role in improving welding quality, reducing welding costs and achieving welding automation. For application of automotive welding robot in China, 30% of industrial robots are used in the automotive industry, of which more than 50% are welding robots.

② Improving the automation of the welding process is a systematic engineering. There are many new requirements for welding equipment, welding processes/methods, welding assistive device, etc. In order to achieve high-speed, high-efficiency welding, the requirements for welding power sources are gradually increasing.

③ Automatic and intelligent welding is the general trend of the times. Due to the variety of auto body types and fast replacement, the automotive welding equipment is required to be updated quickly, and as far as possible to achieve flexible production, robot welding, gluing, handling etc. form flexible production systems;

1.5.2 Requirements by the automotive industry for welding machine enterprises

Whatever the whole car or parts basically involve the application of welding technology. But in the perspective of the whole car, if electric welding machine enterprises want to participate directly, on the one hand they needs quite strong brand degree and technical strength, on the other hand it also needs some human resources. It needs that they are able to intervene in advance before the project is settled or even at the early stage of negotiations between the automobile enterprises and local governments. With a focused goal, this competition is very difficult and worldwide. On the contrary, it is relatively easy to enter and participate from the perspective of parts matching. After all, the enterprises involved in spare parts matching are several times more than the whole vehicle enterprises, with many breakthroughs and obviously weaker competition intensity than that of the limited whole-vehicle market. The requirements by the automotive industry for welders are shown in Table 5.

VI.MEGMEET Welder's Opportunities and Challenges in the Automotive Industry 

Based on the understanding of the application of gas shield welding method and process in domestic automobile industry, we need to start from the following points for the purpose that the existing and upcoming products of MEGMEET can be better promoted and used in the domestic automobile industry.

1.

Low splash, low deformation, high-speed welding process of carbon dioxide

The high-strength steel used in the automotive field has the thickness of not more than 2mm, which is required to be small deformation after welding, high strength, low cost, easy to operate and easy to achieve automation. Therefore, the low splash process of carbon dioxide can meet the needs of users.

2.

Welding technology of galvanized sheet material 

MIG brazing process can be developed based on the existing process.

3.

MAG welder working with robots can meet the needs of flexible automatic production of automobile manufacturing.

4.

Laser MAG composite welding is also more popular in the automotive field, which can make welders and laser equipment work together.

5.

In the field of new energy vehicles

In recent years, the new energy vehicles have grow rapidly, and the production has increased significantly. The earlier you enter in the field, the more stable your footing becomes.

6.In the welding field of automobile aluminum and aluminum alloy materials

In the recent years, due to the light weight of aluminum alloy and the reduction of fuel consumption, aluminum alloy is more and more widely used. According to the market change needs, it is necessary to expand the use of aluminum welder in the automotive field.