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Painting technology (Part I)

painting technology

painting is an important link in the surface manufacturing process of construction machinery products. The quality of anti rust and anti-corrosion coating is one of the important aspects of the overall quality of products. Product appearance quality not only reflects product protection and decoration performance, but also constitutes an important factor of product value

I. painting process

antirust painting process of construction machinery can generally be divided into surface treatment process before painting and antirust primer painting process

1. Surface treatment

surface treatment is one of the important processes of antirust coating. The quality of antirust coating of construction machinery depends on the way of surface treatment to a great extent

according to Imperial Chemical, the coating life is restricted by three factors: surface treatment, accounting for 60%; Coating construction, accounting for 25%; The coating quality accounts for 15%

surface treatment methods of different parts in construction machinery industry

mechanical cleaning can effectively remove the rust, welding slag and oxide skin on the workpiece, eliminate the welding stress, and increase the adhesion between the antirust film and the metal matrix, thus greatly improving the antirust quality of construction machinery parts. The mechanical cleaning standard shall meet SA2 of iso8501 1:1988 Level 5. The surface roughness shall reach 1/3 of the antirust coating thickness. The steel shot used for shot blasting and blasting shall meet the requirements of gb6484

the surface treatment of sheet metal stamping parts is generally called chemical surface treatment. The process flow is as follows:

pre degreasing and degreasing hot water washing cold water washing pickling cold water washing neutralizing cold water washing surface adjustment phosphating cold water washing hot water washing pure water washing drying

the above process also establishes a macro-control and market conditioning mechanism, which can be adjusted appropriately according to the oil and rust conditions of sheet metal stamping parts, or without pickling process or pre degreasing process. Degreasing and phosphating are the key processes in the chemical treatment process, which directly affect the quality of the chemical treatment of the workpiece and the quality of the antirust coating. Relevant process parameters and auxiliary equipment also affect the surface__ Management quality can not be ignored

2. Coating process

due to the wide range of construction machinery, many specifications, heavy machine and large parts with the increase of solid solution temperature, the coating method is generally adopted. Spraying tools include air spray gun, high-pressure airless spray gun, air assisted spray gun and portable electrostatic spray gun. The spraying efficiency of the air spray gun is low (about 30%), and the high-pressure airless spray gun wastes paint. The common feature of the two is that the environmental pollution is serious, so they have been and are being replaced by the air assisted spray gun and the portable electrostatic spray gun. For example, Caterpillar (CAT) of the United States, the world's first construction machinery company, uses an air assisted spray gun for spraying, and a portable electrostatic spray gun is used for sheet covering parts such as the hood, which can ensure the reproducibility of environmental conditions in environmental tests. The coating equipment for construction machinery generally adopts the more advanced water spinning spray booth. Small and medium-sized parts can also use water curtain spray booth or pumpless spray booth. The former has advanced performance, while the latter is economical, convenient and practical. As the whole machine and parts of construction machinery are heavy to find a suitable entry point and have large heat capacity, the drying of its antirust coating generally adopts the drying method of baking uniform hot air convection. The heat source can be steam, electricity, light diesel, natural gas and liquefied petroleum gas according to local conditions

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