The method of repairing or connecting the failed parts of the diesel generator set by applying the adhesive and restoring the function of the parts is called the bonding repair method. In recent years, bonding repair technology has developed rapidly and has been widely used in the repair of diesel generator set. The following describes in detail the electroplating repair method of the diesel generator set parts - the characteristics of the bonding process.
1. Unlimited by materials, all kinds of the same or different materials can be bonded.
2. The bonding process temperature is not high, it will not cause changes in the metallographic structure of the base metal and thermal deformation, and will not cause cracks and other defects, so that it can adhere to cast iron parts, aluminum alloy parts, thin parts, small parts and the like.
3. The strength of the original is not damaged during bonding, and local stress concentration is not easily generated. Compared with riveting, threaded connection and welding, the structure quality is reduced by 20%-25%, and the surface is beautiful and flat.
4. The process is convenient, the cost is low, and the construction period is short, which is convenient for on-site repair.
5. The glue joint has the properties of sealing, abrasion resistance, corrosion resistance and insulation, and some also have heat insulation, moisture proof and shockproof performance. The glue between the two metals also prevents electrochemical corrosion.
The disadvantages are: high temperature resistance (generally only 150 ° C, up to 300 ° C, except for inorganic glue); poor impact resistance, peeling resistance, anti-aging properties; low bonding strength (compared with welding and riveting); The inspection is more difficult. Therefore, it is necessary to fully understand the characteristics of the bonding process, and rationally select the bonding agent and bonding method to make full use of it in the repair work.
Bonding Method
1. Hot melt bonding
The method uses electric heating, hot gas or frictional heat to heat and melt the bonding surface, and then superimposes and adds sufficient pressure until it cools and solidifies. Mainly used for bonding between thermoplastics, most thermoplastic surfaces can be bonded by heating to 150~230 °C.
2. Flux bonding method
Non-finished amorphous thermoplastics, joints plus simple solvents or plastic-containing solutions melt the surface to achieve bonding days.
3. Adhesive bonding method
Adhesives are used to bond two materials or two parts together to achieve the desired strength. The method is the most widely used and can bond a variety of materials such as metals and metals, metals and non-metals, non-metals and non-metals.
There are many types of adhesives, and there are many classification methods. According to the chemical composition of the adhesive, it can be divided into organic adhesive and inorganic adhesive; it is divided into natural adhesive and synthetic adhesive according to the source of raw materials; it is divided into structural adhesive and non-structural according to the strength characteristics of the bonded joint. The adhesive is divided into a liquid adhesive and a solid adhesive according to the state of the adhesive; the shape of the adhesive is powder, rod, film, paste and liquid; and is classified into a thermoplastic adhesive according to thermal properties. Thermosetting adhesives, etc.
The natural adhesive composition is simple, and the synthetic adhesive is mostly composed of a plurality of components. Additives such as a curing agent, a plasticizer, a toughening agent, a diluent, a filler, a coupling agent, a solvent, an antioxidant, and the like are usually added to a base material of a natural material or a polymer material having viscosity and elasticity. Whether or not these additives are added depends on the nature of the adhesive and the requirements of use. Synthetic adhesives can be further divided into thermoplastics (such as acrylates, cellulose polyphenols, polyimides), thermosets (such as phenolic, epoxy, polyester polyurethanes), rubbers (such as chloroprene, butyronitrile), and blends. Type (such as phenolic-butyronitrile, epoxy-polysulfide, phenolic-nylon). Among them, epoxy resin adhesive has strong bonding ability to various metal materials and non-metal materials, and has good water resistance, organic solvent resistance, acid and alkali resistance and corrosion resistance, small shrinkage, and electrical insulation. Good performance and the most widely used.
Bonding process
1. Selection of the agent
When selecting the adhesive, the material of the bonded material, the force and the environment to be used are mainly considered, and the shape, structure and process possibility of the bonded member are comprehensively considered, and the cost is low and the effect is good.
2. Joint Design
When designing the joint, the bonded joint should be subjected to or subjected to shearing force as much as possible; the peeling and uneven pulling force should be avoided as much as possible; the bonding area should be increased as much as possible to improve the bearing capacity of the joint; Practical, economical and reliable. For parts that are impacted or subjected to large forces, appropriate reinforcement measures such as riveting, threaded connections, etc., may be employed.
3. Surface treatment
The goal is to obtain a clean, rough, and active surface to ensure that the bonded joints are identical. It is the most important process in the entire bonding process and is related to the success or failure of bonding.
For surface cleaning, remove the dust with a dry cloth or cotton yarn, remove the thick grease, and then wipe with an organic solvent such as acetone, gasoline or trichloroethylene, or degrease with oil. The rust and oxidation treatment layer is removed by boring, grinding, roughing, sand blasting, electric sparking, etc., and the surface can be roughened. Among them, sandblasting works best. The surface roughness of the metal parts should be mechanically treated with Ra12.5um, and then the surface should be cleaned and dried for use.
If necessary, a uniform, dense oxide film can be obtained by chemical treatment to ensure a firm bond between the bonding surface and the adhesive. Chemical treatment generally uses pickling, anodizing, and the like. When steel, iron and natural rubber are bonded, copper and iron can be copper-plated to greatly improve the bonding strength.
4. Glue
Different coating methods should be selected according to the different forms of the adhesive. For liquid glue, brush coating, spraying, and roller coating can be used. When applying glue, care should be taken to ensure that the glue layer is free of air bubbles and uniform without lack of glue. The amount of glue applied and the number of times of glue application vary depending on the type of glue, and the thickness of the glue layer should be thin. For most adhesives, it is advisable to control the thickness of the adhesive layer in the range of 0.05~o.2mm.
5. open assembly
The adhesive containing the solvent should be left to dry for a certain period of time after the glue is applied, so that the solvent in the adhesive layer is sufficiently volatilized, otherwise bubbles are generated in the adhesive layer after curing, and the bonding strength is lowered. The length of the open time, the temperature is different from glue, should be strictly controlled according to their respective regulations.
6. Curing
The two bonded parts that are left open can be used for closing, assembly and heating, and pressure curing. Except for the room temperature curing glue, almost all other glues need to be heated and cured. Even if it is a room temperature assimilated adhesive, increasing the cultivating temperature is beneficial to the bonding effect. Slowly heat up and cool down during curing. When the temperature is raised to the flow temperature of the adhesive, it should be kept at this temperature for 20~30 minutes, so that the glue is fully diffused and wetted on the bonding surface, and then raised to the desired temperature. Curing temperature, pressure and time should depend on the specific type of adhesive. An oven, an infrared lamp, an electric furnace, and electric induction heating can be used for heating.
7. Quality inspection
The quality inspection of bonding parts is both destructive and non-destructive. The destructive test measures the breaking strength of the bonding member. Non-destructive testing is commonly used in actual production. It is generally tested by observing the appearance and the method of tapping the sound. The accuracy depends largely on the experience of the inspector. In recent years, some advanced technologies such as acoustic resistance, laser holography, and X-ray inspection have also been used for non-destructive testing of bonded parts, and great progress has been made.
8. Post-bonding processing
Some bonding parts are bonded to the technical requirements by machining or bench work. The necessary chamfering and grinding should be carried out before processing, and the cutting force and cutting temperature should be controlled during processing.
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