CB series gear pumps are commonly used in agricultural machinery hydraulic system. After a period of gear pump performance, its performance will decline, the survey shows that the main form of gear pump damage is uniform sleeve and gear wear and scratches, the average wear is generally between 0.02-0.50mm, The depth of the mark is usually between 0.05-0.50mm. Due to agricultural time constraints, the urgent need to repair in a short time after damage, but also must take into account the service life of the gear pump after the second life and maintenance costs and maintenance work site operability. The following describes the quick repair method of arc spraying and stick coating technology. Gear pump arc spraying repair technology 1, the principle and characteristics of arc spraying Arc spraying technology in the past 20 years in materials, equipment and applications developed rapidly, its working principle is to be two sprayed wire as a melting electrode, the motor Variable speed drives, which create a short circuit at the intersection of the gun mouth and cause an arc to melt, are atomized into fine particles with compressed air and sprayed at high velocity onto the pre-treated work surface to form a coating. It is a spray high efficiency, high bonding strength, good coating quality spraying method, with high energy efficiency, equipment investment and low cost, simple equipment, convenient and flexible operation, easy site construction and safety advantages. 2, gear pump arc spray repair process Bushing bore, bushing outer, gear shaft and pump casing uniform wear and scratches between 0.02-0.20mm, should adopt high hardness, and the body with a combination of strong , Good wear resistance arc spray repair process. Arc spraying process: the working surface pretreatment → preheat → spray bonding the bottom → spraying the working layer → cooling → coating processing. Spraying process, the requirements of the workpiece without oil, no rust, surface roughness, preheating temperature is appropriate, the bottom combined with a solid, smooth working layer, the material particles melt-bonded reliable, good wear resistance and corrosion resistance. Spray coating quality and workpieces surface treatment and spraying process has a great relationship, therefore, choose the appropriate surface treatment and spraying process is very important. In addition, the non-sprayed portions adjacent to the coated surface should be bundled with a thin sheet of metal or copper during spraying and spraying. ⑴ surface pretreatment coating and the basic bonding strength and substrate cleanliness and roughness. Before spraying, the basic surface cleaning, degreasing and surface roughening and other pretreatment is an important process spraying process. The first part of the spray should be sprayed with gasoline, acetone degreasing treatment, with a file, fine sandpaper, whetstone will be the fatigue layer and the oxide layer removed, exposing the metal color. Then roughening treatment, roughening treatment can provide surface compressive stress, increase the bonding area and clean the surface of the coating and the substrate, reduce the stress when cooling the coating, ease the internal stress of the coating, it is conducive to the increase of adhesion . Sandblasting is the most commonly used roughening process, sand to sharp, hard as well, the choice of quartz sand, emery and so on. Rough fresh surface easily oxidized or polluted by the environment, it should be timely spraying, if placed more than 4h will be re-roughened. ⑵ surface preheat treatment The temperature difference between the coating and the substrate surface will produce shrinkage stress coating, causing the coating cracking and peeling. Preheating of the substrate surface can reduce and prevent the above adverse effects. But the preheating temperature should not be too high, so as not to cause the substrate surface oxidation and affect the bonding strength of the coating and the substrate surface. Preheat temperature is generally 80-90 ℃, commonly used to complete the neutral flame. ⑶ spray-bonded primer coating before spraying the work of a thin layer of metal coating for the follow-up to provide a clean, rough surface, thereby enhancing the bond between the coating and the substrate strength and shear strength. Bottom bonding materials generally use ferrochrome nickel alloy. The main principle of choosing the spraying process parameters is to increase the bonding strength between the coating and the substrate. Spray gun and the workpiece during the relative movement speed is greater than the flame moving speed, the speed of the size of the coating thickness, spray wire feeding speed, arc power and other parameters determined jointly. Spray gun and the surface of the workpiece is generally about 150mm. Other specifications for arc spraying are determined by the characteristics of the coating equipment and the coating material. ⑷ spraying working layer should be first wire brush to remove the adhesion of the bottom surface of the sediment, and then immediately spray coating. Materials for the carbon steel and low alloy wire, the coating has a higher wear resistance, and lower prices. Spray coating thickness should be based on the amount of wear and tear of the workpiece, machining allowance and other relevant factors (diameter shrinkage, clamping deviation, spray coating diameter uneven amount, etc.) to determine. ⑸ cooling spray temperature after the workpiece is not high, the general can be directly air-cooled. ⑹ spray coating processing machinery processing to the required size of the drawings and the provisions of the surface roughness. Gear pump sticky surface repair technology 1, surface sticky coating principle and characteristics In recent years, surface sticky coating technology in China's equipment maintenance has been widely used for a variety of materials, parts and equipment repair. Its working principle is to add molybdenum disulfide, metal powder, ceramic powder and fiber and other special filler adhesive, directly applied to the surface of materials or parts, so that it has a wear-resistant, corrosion and other functions, mainly for surface strengthening and repair . Its process is simple, convenient and flexible, safe and reliable, does not require specialized equipment, just a good glue coated on the surface of the cleaned parts to be cured after curing can often operate at room temperature, will not make the parts Produce thermal equivalent effect and deformation. 2, sticky coating coating process Cylindrical sleeve, sleeve end face fit, gear end face or pump housing bore small area uniformity of wear between 0.15-0.50mm, scratch depth of 0.2mm or more When, should use sticky coating repair process. Adhesion coating coating process: initial cleaning → pre-processing → final cleaning and activation → preparation of repair agent → coating → curing → finishing, cleaning or post-processing. Although the sticky coating process is relatively simple, but the actual construction requirements are quite strict, just choose a good adhesive, not necessarily able to obtain high viscosity strength. It is necessary to select the right adhesive, but also strictly in accordance with the correct process of adhesive coating the right adhesive, but also strictly in accordance with the correct process method line viscosity coating in order to obtain a satisfactory coating effect. ⑴ early cleaning parts surface must not have grease, water, rust, dust and so on. Wash with gasoline, diesel or kerosene first, then acetone. ⑵ pre-processing fine sandpaper into a certain trench mesh, exposing the base color. ⑶ final cleaning and activation treatment with acetone or special cleaning agent. Then sandblasting, flame or chemical treatment to improve the surface activity. ⑷ preparation repair agent repair agent in use should be strictly in accordance with the provisions of the ratio of the agent (A) and curing agent (B) fully mixed to the same color as well, and within the prescribed time, run with the use. ⑸ coated with the first repair agent in the repair surface coating a thin layer, repeated scratching and parts fully infiltrated, and then evenly coated to the specified size, leaving a finishing allowance. As much as possible in the coating to move in one direction, the reciprocating coating will wrap the air in the gel to form bubbles or pores. ⑹ curing coated with a release agent in the steel pressure in the work, the general room temperature curing takes 24 hours, heating curing (about 80 ℃) required 2-3 hours. ⑺ finishing, cleaning or post-processing fine boring or with a file, fine sandpaper, whetstone will be finishing surface finishing to the required size.
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