Construction machinery is the machinery that serves the construction of various capital construction projects such as urban and rural construction, railway, highway, port and wharf, farmland and water conservancy, electric power, metallurgy, mining, sea and air base, etc; All operation machinery and equipment necessary for earthwork, stonework, concrete works and various construction and installation works in comprehensive mechanized construction are generally referred to as construction machinery. In China, construction machinery mainly includes 10 categories: excavation machinery, shovel transportation machinery, engineering hoisting machinery, pavement machinery, compaction machinery, piling machinery, reinforced concrete machinery, rock drilling machinery, forklift, special engineering machinery and so on. Its classification in other countries is similar. For example, the United States calls construction machinery construction machinery, Japan calls construction machinery, and Russia calls construction and road construction machinery. Specific and common construction machinery include: hydraulic excavator, crawler bulldozer, wheel loader, roller, grader, paver, forklift and truck crane.
As we all know, construction machinery is a kind of outdoor working machinery. It has been exposed to the harsh environment such as outdoor atmosphere (including marine atmosphere, industrial atmosphere, urban atmosphere and rural atmosphere) and different water quality (sea water and river water) for a long time. It is subject to different degrees of corrosion in different regions and environments all the time, resulting in various "chronic diseases" and "frequently occurring diseases" of construction machinery. Engineering machinery coating is an important link in the manufacturing process of engineering machinery 名媛直播. The quality of anti rust and anti-corrosion coating is one of the important aspects of the overall quality of 名媛直播. The appearance quality of 名媛直播 not only reflects the protection and decoration performance of 名媛直播, but also an important factor constituting the value of 名媛直播.
1 coating process
Antirust coating process of construction machinery can generally be divided into surface treatment process before coating and antirust primer coating process.
1.1 surface treatment
Surface treatment is one of the important processes of antirust coating. The quality of antirust coating of construction machinery largely depends on the way of surface treatment.
According to Imperial Chemical, the coating life is restricted by three factors: surface treatment, accounting for 60%; Coating construction, accounting for 25%; The quality of the coating itself accounts for 15%.
Construction machinery industry, surface treatment methods of different parts.
Mechanical cleaning can effectively remove the rust, welding slag and oxide scale on the workpiece, eliminate the welding stress, and increase the adhesion between the antirust film and the metal matrix, so as to greatly improve the antirust quality of construction machinery parts. The mechanical cleaning standard is required to 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 shot 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:
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 of sheet stamping parts, or there is no pickling process or pre degreasing process. Degreasing and phosphating are the key processes in the chemical treatment process, which directly affect the quality of chemical treatment and antirust coating. Relevant process parameters and relevant auxiliary equipment are also affected at the surface__ Management quality is a factor that can not be ignored.
1.2 coating process
Due to the wide range of construction machinery, many specifications, heavy machine and large parts, spraying is generally used for coating. Spraying tools include air spray gun, high-pressure airless spray gun, air assisted spray gun and portable electrostatic spray gun. The spraying efficiency of air spray gun is low (about 30%), and the high-pressure airless spray gun wastes paint. Their common feature is that the environmental pollution is serious, so they have been and are being replaced by air assisted spray gun and portable electrostatic spray gun. For example, the world's first construction machinery company - Caterpillar (CAT) Company of the United States uses air assisted spray gun for spraying, and portable electrostatic spray gun is used for sheet covering parts such as engine hood. The coating equipment for construction machinery generally adopts the more advanced water rotary spray booth. Small and medium-sized parts can also use water curtain spray booth or pump free spray booth. The former has advanced performance, while the latter is economical, convenient and practical. Due to the heavy weight and large heat capacity of the whole machine and parts of construction machinery, the drying of its antirust coating generally adopts the drying method of uniform baking and hot air convection. The heat source can be steam, electricity, light diesel, natural gas and liquefied petroleum gas according to local conditions.
2 main coating equipment
2.1 passing shot blasting chamber
The passing shot blasting chamber is composed of cleaning chamber body, shot blasting device, shot circulation system, ventilation and dust removal system, bottom foundation and electrical control system. The non-standard design with different sizes can be carried out according to the workpieces of different specifications, and the finalized equipment can also be selected.
The through shot blasting chamber is applicable to the surface cleaning and strengthening of construction machinery structural parts and forged castings, so as to obtain a smooth surface with a certain roughness, increase the adhesion of coating film and improve the anti-corrosion effect of workpieces. When the workpiece enters the shot blasting chamber, the shot blasting device driven by the motor centrifugally throws out high-speed shot, which strongly impacts the rust and oxide scale on the surface of the workpiece. After the workpiece moves at a uniform speed or rotates several times, it is cleaned, and the surface quality can reach SA2 ~ SA2 Level 5 standard.
2.2 water spray booth
Water spinning spray booth is also called hydraulic spinning spray booth. The room adopts gas laminar flow suppression to prevent the diffusion of paint mist, and uses hydraulic spinning pipe to filter paint mist. It is a technically complete paint spraying room at present.
The water spray booth is composed of a room body, an electric door, a paint mist filtering device, an air conditioning air supply device and an exhaust device; The lighting devices are installed on both sides of the room, and the illuminance is more than 500 lux, which can be controlled in groups; Combustible gas concentration detection and alarm devices are set indoors; The paint mist filtering device is composed of washing plate, hydraulic spinning device, underground water tank and exhaust device, and the paint mist removal rate is > 98%; The air supply device of the air conditioner is the main component to make the gas form a laminar flow. The air sent into the air supply room is filtered and heated, and then evenly sent to the room from the air supply ceiling to make the indoor wind speed uniform. When there is no workpiece, the vertical wind speed can reach 0.35 ~ 0.4 m · s - 1; The exhaust device uses the fan to filter the paint mist gas in the chamber through the hydraulic spinning pipe and discharge it from between the sink and the washing plate.
2.3 hot air drying room
The drying mode is hot air circulation convection mode, which has the greatest advantage of uniform baking, especially suitable for construction machinery parts with large heat capacity. Heating sources include steam, electricity, light diesel, natural gas, liquefied petroleum gas, etc. If conditions permit, liquefied petroleum gas is preferred. This is a clean and efficient energy. The biggest advantage is that the production and operation cost is only 35% ~ 40% of the power cost.
2.4 conveying system
For construction machinery components (structural parts), the use of self-propelled electric hoist is an effective choice.
The self-propelled electric hoist conveying system is composed of gantry column, bearing track, sliding conductor rail, collector, load vehicle, electric hoist and PC controlled central control cabinet.
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. It can not only continuously or step-by-step transport the workpiece according to the preset program, but also realize automatic or manual free lifting in the paint booth at the upper and lower parts where there is manual operation.
3 coating
Construction machinery coatings shall have the following characteristics:
① Extremely low permeability to water, oxygen and corrosive media; ② Strong and lasting adhesion with substrate; ③ Good anti rust and decorative properties; ④ With special properties, such as insulation, conductivity, heat insulation, etc; ⑤ Have appropriate coating supporting system.
With the needs of industrial energy conservation and environmental protection, under the condition of ensuring the above performance, the coating should also have the performance of low-temperature quick drying, environmental protection and energy saving. This kind of coating is especially suitable for the coating of construction machinery parts and complete machines with small production batch.
At present, the coatings used for domestic construction machinery are generally epoxy ester primer and polyurethane finish. The former has good antirust performance and the latter has good decorative performance.
4 environmental protection and labor safety and health
4.1 environmental protection
Environmental protection is a very important issue in the coating design of construction machinery. The basis is:
① Gb8978-7996 integrated wastewater discharge standard;
② GB16297-1996 integrated emission standard of air pollutants;
③ GB12348-90 noise standard for industrial enterprises;
④ Jbj16-2000 code for design of environmental protection of machinery industry, etc.
We should resolutely implement the design and construction related to the prevention of pollution and other public hazards, and implement the "three Simultaneities" system that should be designed, constructed and put into operation at the same time as the main project.
For example, in the anti rust coating project of construction machinery, the regularly discharged coating wastewater and the acid-base wastewater discharged by chemical treatment can be treated by a special wastewater treatment unit after collection and regulation, and can be discharged only when the national standard pH = 6 ~ 9, SS = 70 mg / L, COD = 100 mg · L - 1 and petroleum 5 mg / L are met.
In addition, certain measures should be taken to control waste gas, waste residue and noise.
4.2 labor safety and health
In terms of labor safety and health, the national standards as the basis include:
① Gbj16-87 (2001 Edition) code for fire protection design of buildings;
② Jbj18-2000 code for design of occupational safety and health in machinery industry;
③ Gb6514-1995 safety code for painting operation - Safety of painting process and ventilation and purification;
④ Gb14443-1993 safety regulations for coating operation - Safety Technical Regulations for coating drying room;
⑤ Gb14444-1993 safety regulations for painting operation · safety technical regulations for paint booth, etc.
Strengthen the management of labor safety and health in the workshop, continuously carry out education and training in safety knowledge and labor health, and strictly implement various labor safety and industrial health regulations of the state and enterprises.
