Time:1/11/2019 8:41:51 AMauthor:source:
The manufacturing process and equipment principle of NdFeB magnets are popularized, dissolved, powdered, formed, sintered, post-processed, etc.
(1) Smelting 1. According to the different processes, it can be divided into two types: conventional smelting (20kg, 30kg, 50kg, 100kg) and simmering furnace (100kg, 300kg, 500kg). 2. Process A, Nd, Fe, B ingredients pre-treatment B, ingredient C, smelting: First, charge and then pump to the true 1Pa, start to send low-power heating, continue to pump while heating, with increasing temperature, adsorption In the state of the gas, the water is gradually desorbed and extracted, until the charge is generally dark red, the valve is filled with argon gas, and the power is increased until the charge is completely melted, and the refining is performed for about 5 minutes, and the refining is completed to reduce the power and carry out the pouring. When pouring, the gate should be aligned with the cooling mold, and the pouring is completed and cooled. D. Preservation of alloys In the process of placing and transporting alloy ingots, attention should be paid to the entry of impurities such as the wire of the gloves and the dust in the air. At the same time, oxygen has a destructive effect on the alloy, and oxygen permeates into the yttrium oxide. The water vapor has a destructive effect on the alloy. When the water hits the ruthenium, it will form ruthenium oxides and hydrides. Therefore, the smelting process should be protected against impurities and oxidation. .
(2) Milling 1, equipment hydrogen crushing furnace, coarse breaking machine, medium crushing machine, jet mill, mixer 2, process 3. Process control points A, particle size, 2.9-5.2um is appropriate, the finer the particle size The coercive force and remanence will increase, and the corrosion resistance of the product will also increase, but the subsequent process is not well controlled. The narrower the particle size distribution can be done. B. The proper amount of air in the jet mill is very important for the passivation of the powder. It is as if a person walks from the dark to the bright place, the eyes will be uncomfortable, sometimes it will damage the eyes. If the powder does not put some air, it will be more oxidized in the subsequent production, and it is very likely to burn C and stir. The powder properties are not consistent, so the powder needs to be stirred.
(3) Forming 1, equipment press, isostatic pressing, storage cylinder 2, process A, weighing: powdering according to process requirements B, magnetic field oriented forming: this process in order to put thousands of NdFeB powder in the magnetic field Under the action, they are arranged neatly and pressed into a set shape in the mold. The basic requirement of the press is that the magnetic field must be greater than 18000 ohms in the 40mm air gap, and there should be a photoelectric protector to prevent the press from injuring the event C. The pressed green density is about 3.2---3.8g/cm3, and the theoretical density of Nd-Fe-B after sintering is about 7.5g/cm3, so the shrinkage is large when pressing relatively large cylinders and squares. Cracking and cornering are deformed and the size is out of tolerance. Therefore, it is necessary to increase the density of the green body by isostatic pressing. The density of the green body after isostatic pressing is 4.5 g/cm3. The company now removes the low-performance small column (Ф10 or less). After isostatic pressing, the pendulum box is directly inserted into the sintering furnace and the other is subjected to isostatic pressing, and the isostatic pressing green body is protected from oil immersion and surface oxidation, and must be vacuum-packed and stripped before entering the furnace. 4. Abrasives: grinding The level of production and design directly affects the product Appearance quality, with the fierce competition in the industry, abrasive tools are an important part of cost saving, the reduction of processing allowance, the reduction of product deformation, and the direct suppression production of some special-shaped products will determine whether a company is competitive. One of the important factors.
(4) After the sintering or isostatic pressing, the green body does not have the microstructure of high permanent magnet properties, in order to further improve the density, improve the contact property between the powder particles, improve the strength, and make the magnet have the microstructure characteristics of high permanent magnet properties. It is necessary to heat the compact to a temperature below the melting point of the powder matrix phase for a heat treatment. The sintering furnace should have good sealing performance and low leakage rate. Therefore, vacuum should be kept tightly to prevent gas and water vapor adsorption, and the product should not be allowed to be taken out. The furnace door is open, and it is in contact with the outside air and water vapor for a long time. The stripping tank should also be closed in time to prevent the adsorption of water vapor and affect the performance of the product. The sintering process is divided into sintering and aging two-stage process, sintering temperature, and hydrogen-containing scrap Between 1050 ° C and 1085 ° C, the ingots are crushed between 1070 ° C and 1095 ° C. The ingots are between 1100 ° C and 1135 ° C. The aging time is divided into two stages: 890 ° C ~ 920 ° C and 500 ° C ~ The second stage of 630 °C, from sintering and aging to the entire process of the furnace generally takes between 20~38 hours.
(V) Post-processing Nd-Fe-B blanks can not directly meet the customer's requirements due to the influence of production factors, and must be processed after subsequent processing to meet customer requirements. ü Wire cutting (wire cutting machine) for some shaped or sliced machines that can not be directly sliced ü For sliced and medium and small squares, use a microtome for higher precision or CPK requirements (slicer, Double-sided grinding machine) ü Small cylinders that cannot be directly pressed need to be cut into small square bars and then rounded (small centerless grinding). ü Some products require small holes to be punched, and holes with holes above Ф6 can be set. Hole machine, hole machine) ü Form-pressed cylinder (Ф80 or less) is ground with a centerless mill (heartless mill) ü For cylinders larger than 80mm, it must be done with a hole-setting device. Flat grinding, or double-sided grinding equipment ü Some shaped products can also be completed with direct tiling
(6) Electroplating Since the anti-corrosion performance of NdFeB products is relatively poor, surface treatment must be carried out. 1. Form of surface treatment a. Zinc plating: blue and white zinc, white zinc, color zinc, black zinc. According to environmental protection requirements, it can be divided into trivalent chromium zinc (environmental zinc) and hexavalent chromium and zinc. b. Nickel plating: bright nickel, black nickel, nickel plating is currently nickel, nickel and nickel three-layer plating c. Electrophoresis (epoxy plating): black epoxy, gray epoxy d. Phosphating e. gold plating , copper plating, silver plating, tin plating, etc. 2. Electroplating process mechanical chamfering time may be long, so the plating product is not very fast, there must be a cycle.
(VII) Reliability test 1. Drop test: glue the product and iron sheet together with glue, free fall from 1~1.5m in the air and repeat it many times to see if the coating has fallen off. The drop test is basically acceptance of galvanized products. . 2. Cross-cut test: Use a knife to cross-cut the coating to see the bonding of the coating (galvanized or nickel-plated). 3. Pyrolysis heat test: The product after electroplating nickel is placed in an oven for heating (about 200 ° C), and then placed in water to chill, such that several cycles to verify the bonding strength of the nickel plating product. 4. PCT test: (pressure cook test) conditions: 2 atmospheres, 95% relative humidity, 121 ° C temperature, check the adhesion of the coating. 5. Weight loss test: Nd-Fe-B is not the same because of easy oxidation, different processes and different added elements, and different process control. The unit of weight loss test is how many milligrams of weight lost per square centimeter. Not the same as European standards.
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