Construction machinery is for the construction of urban and rural construction, railways, highways, ports and docks, farmland water conservancy, electricity, metallurgy, mines, sea and air bases and other basic construction projects; all earthwork, stonework, concrete works and various Construction machinery installation engineering in the comprehensive mechanized construction, the necessary operating machinery and equipment, commonly known as construction machinery. Construction machinery in my country mainly includes: excavation machinery, earth shovel transportation machinery, construction crane machinery, pavement machinery, compaction machinery, pile driver machinery, reinforced concrete machinery, rock drilling machinery, forklifts, special construction machinery and other 10 categories. Its classification in other countries is similar, such as the construction machinery in the United States, construction machinery in Japan, and construction and road machinery in Russia. Specific common construction machinery include: hydraulic excavators, crawler bulldozers, wheel loaders, road rollers, graders, pavers, forklifts and truck cranes.
As we all know, construction machinery is an outdoor working machinery, which is exposed to the outdoor atmosphere (including marine atmosphere, industrial atmosphere, urban atmosphere and rural atmosphere) and different water quality (seawater, river water) and other harsh environments for a long time. Different degrees of corrosion in different regions and environments have caused various "chronic diseases" and "more frequent diseases" of construction machinery. Construction machinery coating is an important link in the manufacturing process of construction machinery 名媛直播. Anti-rust and anti-corrosion coating quality is one of the important aspects of the overall quality of the product. Product appearance quality not only reflects product protection and decoration performance, but also an important factor that constitutes product value.
1 Painting process
Construction machinery anti-rust coating process can generally be divided into surface treatment process before coating and anti-rust primer coating process.
1. 1 Surface treatment
Surface treatment is one of the important processes of antirust coating. The quality of anti-rust coating of construction machinery depends to a large extent on the quality of the surface treatment.
According to the introduction of the British Imperial Chemical Company, the life of the coating is restricted by three factors: surface treatment, accounting for 60%; coating construction, accounting for 25%; coating quality, accounting for 15%.
Construction machinery industry, surface treatment of different parts.
Mechanical cleaning can effectively remove rust, welding slag, oxide scale on the workpiece, eliminate welding stress, increase the bonding force between the anti-rust coating film and the metal substrate, thereby greatly improving the anti-rust quality of construction machinery parts. The standard for mechanical cleaning requires Sa850 of ISO8501 -1:1988. The surface roughness should reach 1 /3 of the thickness of the anti-rust coating. The steel shot used for shot blasting and shot blasting shall meet the requirements of GB6484.
The surface treatment of sheet metal stamping is called chemical surface treatment. The technological process is:
Pre-degreasing → degreasing → hot water washing → cold water washing → pickling → cold water washing → neutralization → cold water washing → surface adjustment → phosphating → cold water washing → hot water washing → pure water washing → drying
The above process can also be adjusted appropriately according to the oil and rust conditions of the sheet metal stampings, or without the pickling process, or without the degreasing process. Degreasing and phosphating are the key processes in the chemical treatment process. These two processes directly affect the quality of the chemical treatment of the workpiece and the quality of the anti-rust coating. The relevant process parameters and related auxiliary equipment are also factors that cannot be ignored that affect the surface treatment quality.
1.2 coating process
Due to the wide range of construction machinery, many specifications, the weight of the whole machine, and the large parts, the spraying method is generally used for painting. Spraying tools include air spray guns, high-pressure airless spray guns, air-assisted spray guns and portable electrostatic spray guns. Air spray guns have low spraying efficiency (about 30%), and high-pressure airless spray guns waste paint. The common feature of the two is that the environmental pollution is serious, so they have been and are being replaced by air-assisted spray guns and portable electrostatic spray guns. For example, Caterpillar (CAT), the world's first engineering machinery company, uses an air-assisted spray gun for spraying, and uses a portable electrostatic spray gun for thin plate covers such as the engine hood. The coating equipment for construction machinery generally adopts the more advanced water-spray spray booth. Small and medium parts can also use water curtain spray booth or pumpless spray booth. The former has advanced performance, the latter is economical, convenient and practical. Due to the heavy construction machinery and components and large heat capacity, the drying of the anti-rust coating is generally done by uniformly hot air convection drying. The heat source can be adapted to local conditions, and steam, electricity, light diesel oil, natural gas and liquefied petroleum gas can be selected.
2 Main coating equipment
2. 1 Walk-through shot blasting room
Pass-through shot blasting room is composed of cleaning room body, shot blasting device, projectile circulation system, ventilation and dust removal system, bottom foundation and electrical control system. According to different specifications of workpieces, non-standard designs of different sizes can be used, and styling equipment can also be used.
Pass-through shot blasting chamber is suitable for the cleaning and strengthening of the surface of engineering machinery structural parts and forging castings, so as to obtain a certain roughness of the smooth surface, increase the coating film binding force, and improve the anti-corrosion effect of the workpiece. When the workpiece enters the shot blasting chamber, the shot blaster driven by the motor centrifugally throws high-speed projectiles, which strongly impacts the rust and scale on the surface of the workpiece. The workpiece is cleaned after constant speed movement or several rotations, and the surface quality can reach Sa2 ~ Sa2. 5 level standard.
2. 2 Water swirl spray booth
Water spin spraying room is also called hydraulic spinning spraying room. The chamber uses a gas laminar flow suppression method to prevent the spread of paint mist, and uses a hydraulic spinning tube to filter the paint mist. It is a technically complete paint spraying chamber.
The water spray paint room is composed of a room body, an electric door, a paint mist filter device, an air-conditioning air supply device and an exhaust device; the lighting device is installed on both sides of the room body, and the illuminance is above 500 Lux, which can be controlled by groups; the combustible gas concentration is set indoors Detection and alarm device; paint mist filter device is composed of washing plate, hydrocyclone, groundwater tank and exhaust device, paint mist removal rate is> 98%; air conditioning air supply device is the main component that makes gas form laminar flow, The air sent into the air supply chamber is filtered, heated, and evenly sent from the air supply ceiling to the room, so that the indoor wind speed is uniform, and the vertical wind speed can reach 0.35 ~ 0.4 m · s-1 when there is no workpiece; the exhaust device is Use a fan to filter the paint mist gas in the chamber through the hydraulic spinning tube and discharge it between the water tank and the washing plate.
2. 3 Hot air drying room
Drying method is hot air circulation convection method, its biggest advantage is uniform baking, especially suitable for engineering machinery parts with large heat capacity. Heating sources include steam, electricity, light diesel oil, natural gas, and liquefied petroleum gas. When conditions permit, LPG is preferred. This is a kind of clean and efficient energy. The biggest advantage is that the production and operation cost is only 35% to 40% of the electricity cost.
2. 4 Conveying system
For construction machinery components (structural parts), the use of self-propelled hoist is an effective choice.
Self-propelled electric hoist conveying system is composed of gantry column, bearing rail, sliding conductive rail and current collector, cargo truck, electric hoist, and central control cabinet controlled by PC.
The system integrates the four technical essences of machinery, electronics, computer, and automatic control, and focuses on the four logistics links of warehousing, transportation, loading and unloading, and process operation. Not only can the workpiece be transported continuously or step by step according to the preset program, but it is especially convenient that it can be automatically or manually freely lifted in the spraying room where there are manual operations such as the upper and lower parts.
3 Paint
Construction machinery coatings should have the following characteristics:
①Permeability to water, oxygen and corrosive medium is extremely small; ②Strong adhesion to the substrate and long-lasting; ③Good anti-rust and decorative properties; ④Special properties, such as insulation, conductivity, heat insulation, etc. ; ⑤ has an appropriate coating matching system.
With the needs of industrial energy saving and environmental protection, under the condition of ensuring the above performance, the coating should also have the performance of low temperature and quick drying, environmental protection and energy saving, and this type of coating should be especially suitable for the production of small quantities of engineering machinery parts and complete machines Painting.
The coatings currently used in domestic construction machinery are generally epoxy ester primers and polyurethane topcoats. The former has good anti-rust performance, while the latter has better decorative performance.
4 Environmental protection and labor safety and hygiene
4. 1 Environmental protection
In the coating design of construction machinery, environmental protection is a very important issue. The basis is:
① GB8978 — 7996 "Comprehensive Wastewater Discharge Standard";
② GB16297 — 1996 Comprehensive Air Emission Standards;
③ GB12348 — 90 “Noise Standard of Industrial Enterprise Factory”;
④ JBJ16 — 2000 “Code for Design of Environmental Protection of Machinery Industry”, etc.
Resolutely implement the design and construction related to the prevention of pollution and other public hazards. The "three simultaneous" system of design, construction and simultaneous use of the main project should be implemented at the same time.
For example, in the anti-rust coating project of construction machinery, the paint wastewater and the acid and alkali wastewater discharged regularly by chemical treatment are treated by a special wastewater treatment unit after collection and adjustment, and meet the national standard pH = 6 ~ 9, SS = 70 mg /L, COD = 100 mg · L-1, petroleum can only be discharged after 5 mg/L.
In addition to exhaust gas, waste residue, noise, etc., certain measures must be taken to control the standards.
4. 2 Labor safety and health
In terms of occupational safety and health, the national standards based on are:
① GBJ16—87 (2001 edition) "Code for Fire Protection of Architectural Design";
② JBJ18 — 2000 "Code for occupational safety and health design of machinery industry";
③ GB6514 — 1995 "Safety regulations for painting operations · Safety of painting process and its ventilation and purification";
④ GB14443 — 1993 “Safety Regulations for Coating Operations·Safety Technical Regulations for Coating Drying Room”;
⑤ GB14444 — 1993 “Safety regulations for painting operations and safety technical regulations for painting booths” etc.
Strengthen the work safety and health management of the workshop, and continue to carry out education and training on safety knowledge and work hygiene, and strictly implement the national and enterprise regulations on work safety and industrial hygiene.
