The frame is primarily used in commercial vehicles such as trucks, passenger cars, and combined passenger and cargo vehicles. It is typically manufactured by riveting, welding, or bolting together hot-rolled steel plate stamping components. In China, the coating process varies significantly depending on the scale of production and the availability of equipment. The processes are generally divided into mass production and small-batch production.
In mass production, the process includes cutting and blanking the steel plates, removing scale, applying rust prevention, stamping, welding, riveting, degreasing, phosphating, electrophoresis or dipping, drying, and finally applying a top coat as needed. Most truck manufacturers in China use this method, which ensures a more consistent and durable finish.
On the other hand, small-batch production involves cutting and blanking the steel plates, stamping (or purchasing pre-stamped vertical and horizontal beams), drilling, welding or riveting, assembly, derusting, cleaning, dipping or painting, and then drying or allowing natural drying. Due to variations in material quality and process control, the coating quality can be inconsistent.
The level of coating on vehicle frames in China varies widely. Mass production generally results in better-quality finishes compared to small-batch production. However, common issues include incomplete coverage on sharp edges, welds, and joints. Even with cathodic electrophoresis, these problems persist due to structural limitations and inadequate pre-treatment, especially when rust forms between stages.
Compared to foreign countries, China's best coating technology is comparable to that of Japan and South Korea, but still lags behind Europe and the United States. Continuous improvements in process control, material quality, and surface preparation are essential for further enhancing the durability and appearance of vehicle frames in China.
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