Hvordan bedømmer man kvaliteten af sintrede NdFeB-magneter?
Sintrede neodym-jernbor-permanentmagneter, som et af de materialer, der fremmer moderne teknologi og sociale fremskridt, er meget udbredt inden for følgende områder: computerharddiske, nuklear magnetisk resonansbilleddannelse, elektriske køretøjer, vindkraftproduktion, industrielle permanentmagnetmotorer, forbrugere elektronik (cd, dvd) , mobiltelefoner, lyd, kopimaskiner, scannere, kameraer, kameraer, køleskabe, fjernsyn, klimaanlæg osv.) og magnetiske maskiner, magnetisk levitationsteknologi, magnetisk transmission og andre industrier.
I de sidste 30 år har den permanente magnetmaterialeindustri udviklet sig kraftigt, med dens magnetiske egenskaber, der konstant slår nye rekorder, og mangfoldigheden og kvaliteterne af materialer har været stigende. Med udvidelsen af markedet vokser dets producenter dag for dag, og mange kunder vil uundgåeligt falde i en sådan forvirring. Hvordan bedømmer man fordele og ulemper ved produkterne?
Comprehensive judgment method: 1. Magnet performance; 2. Magnet size; 3. Magnet coating.
First of all, the guarantee of magnet performance comes from the control of the raw material production process
1. According to the requirements of high-grade or mid-grade or low-grade sintered NdFeB, the raw materials are selected according to the raw material composition stipulated by national standards.
2. Whether the production process is advanced or not directly determines the performance and quality of the magnet. The current advanced technologies are scale ingot (SC) technology, hydrogen crushing (HD) technology and jet mill (JM) technology. Small-capacity vacuum induction smelting furnaces (10kg, 25kg, 50kg) have been replaced by large-capacity (100kg, 200kg, 600kg, 800kg) vacuum induction furnaces. SC (StripCasting) rapid-setting cast sheet technology has gradually replaced large ingots (ingots with a thickness greater than 20-40mm in the cooling direction), and hydrogen crushing (HD) technology and jet mill (JM) have replaced jaw crushers and disc mills. The machine and ball mill (wet milling) ensure the uniformity of the powder and are beneficial to liquid phase sintering and grain refinement.
3. In terms of magnetic field orientation, my country is a country that adopts two-step compression molding. It uses low pressure vertical compression molding during orientation, and then adopts quasi-isostatic compression molding. This is one of the characteristics of my country's sintered NdFeB industry.
4. In addition, the monitoring of the quality of the production process is very important, and it can be controlled by testing methods such as SC sheet thickness measurement and JM powder particle size distribution. Products are all dependent on the control of the production process, but customers will be very confused, how to judge the performance of the products I buy? The Institute of Metrology has developed a variety of models of permanent magnetic material technology magnetic parameter measuring instruments. The pulsed magnetic field magnetometer (PFM) is a test instrument for testing ultra-high coercivity permanent magnets, mainly to adapt to the high coercivity permanent magnets required by the electric vehicle field and large permanent magnet motors.
Customers can select the NdFeB grades they need according to the magnet parameters Br (remanence), Hcb (coercivity), Hcj (intrinsic coercivity), (BH)max (large magnetic energy product), and these four The parameter is the standard for judging whether the product is produced in accordance with the customer's requirements.
Secondly, the guarantee of magnet size depends on the processing strength of the factory
De praktisk brugte neodym-jern-bor permanente magneter har forskellige former, såsom skiver, cylindre, cylindre (med indvendige huller); firkantede plader, firkanter, firkantede søjler; flise-formet, sektor-formet, trapezformet, polygonal og forskellige former. Uregelmæssige former osv. De permanente magneter af hver form har forskellige størrelser, og det er vanskeligt at danne dem på én gang under produktionsprocessen. Den generelle produktionsproces er: Mr. producerer store (store-størrelser) emner, efter sintring og anløbning, og derefter gennem mekanisk bearbejdning (inklusive skæring, stansning) og slibning, overfladebelægning (coating) behandling, og fortsæt derefter Magnetydelse, overfladekvalitet og dimensionsnøjagtighed testes, magnetiseres derefter, pakkes og sendes fra fabrikken.
1. Mechanical processing is divided into three categories:
(1) Cutting process: cutting cylindrical and square columnar magnets into discs and squares;
(2) Shape processing: processing round and square magnets into fan-shaped, tile-shaped or grooved or other complex-shaped magnets;
(3) Punching: processing round and square bar magnets into cylindrical or square cylindrical magnets. Its processing methods include: grinding and slicing processing, electric discharge cutting processing and laser processing.
2. The surface of the sintered NdFeB permanent magnet element is generally required to be smooth and reach a certain accuracy. The surface of the magnet delivered as a blank needs to be surface-grinded. Common grinding methods for square NdFeB permanent magnet alloys include surface grinding, double-end grinding, internal grinding, and external grinding. Cylinders are commonly used for coreless grinding, double-end grinding, etc. Multi-station grinders are used for tile, sector and VCM magnets.
A qualified magnet not only needs to meet the performance standards, but also the control of dimensional tolerances directly affects its application. The guarantee of size directly depends on the processing strength of the factory. Processing equipment is constantly updated with economic and market demand. The trend of new equipment and industrial automation not only meets the increasing demand of customers for product accuracy, but also saves The manpower and cost are reduced, making it more competitive in the market.
Again, the quality of the magnet coating directly determines the application life of the product
Experiments have shown that 1cm3 of sintered neodymium iron boron permanent magnets will be completely oxidized and corroded if they are placed in the air at 150 degree for 51 days. It is more susceptible to corrosion in weak acid solutions. In order to make the neodymium iron boron permanent magnet durable, it is required to have a service life of 20-30 years, and it must be subjected to surface anti-corrosion treatment to resist the corrosion of the corrosive medium to the magnet. At present, the manufacturing industry of sintered NdFeB permanent magnets generally uses methods such as electroplating metal, electroplating plus electroless metal plating, electrophoretic coating, and phosphating treatment. An additional spacer is plated on the surface of the magnet to isolate the surface of the magnet from the corrosive medium. , In order to prevent the media from harming the magnet.
1, generally three processes are mainly zinc plating, nickel plating plus copper plus nickel, nickel plating plus copper plus electroless nickel plating, and other metal plating requirements are generally applied to other metal plating after nickel plating.
2. Fosfatering anvendes også i nogle specielle tilfælde: (1) Når neodymjernbormagnetproduktet vendes og opbevares for længe, og den efterfølgende overfladebehandlingsmetode ikke er klar, er anvendelsen af fosfatering enkel og let; 2) Når magneten har brug for epoxyklæbende limning, maling osv., kræver bindingskraften af organiske epoxyforbindelser såsom lim og maling god fugtbarhed af matrixen. Fosfateringsprocessen kan forbedre befugtningen af magnetoverfladen.
3, electrophoretic coating has become one of the widely used anti-corrosion surface treatment technologies. Because it not only has a good bonding force with the surface of the porous magnet, but also has corrosion resistance such as salt spray, acid and alkali resistance, and excellent corrosion resistance. However, compared with spray coating, its resistance to humidity and heat is poor.
Customers can choose the plating layer according to their product work requirements. With the expansion of the application field of motors, customers have requirements for the corrosion resistance of NdFeB. The HAST experiment (also known as the PCT experiment) is specifically to test the corrosion resistance of sintered NdFeB permanent magnets in humid and high temperature environments.
Og hvordan vurderer kunderne, om belægningen lever op til kravene? Formålet med saltspraytesten er at lave en hurtig anti-korrosionstest på de sintrede NdFeB-magneter, hvis overflade er blevet behandlet med anti-korrosionsbelægning. Ved afslutningen af forsøget tages prøven ud af testboksen og tørres. Brug dine øjne eller et forstørrelsesglas til at observere, om der er pletter på overfladen af prøven, og ændringen i farven på størrelsesboksen på pletområdet.
To sum up, only by understanding the production process and the requirements of the product can customers correctly judge the eligibility of the product. In short, it is the grasp of performance, the control of dimensional tolerances, the detection of coatings and the evaluation of appearance.
Med hensyn til ydeevne kan Br (remanens), Hcb (koercivitet), Hcj (intrinsisk koercivitet), (BH)max (magnetisk energiprodukt) og afmagnetiseringskurven testes efter ydeevne; dimensionelle tolerancer kan måles ved hjælp af kalibre. Dens nøjagtighed; på belægningen kan belægningens farve og lysstyrke observeres med det blotte øje, og bindingskraften, saltsprayeksperiment og andre detektionsmetoder; det overordnede udseende, hovedsageligt med det blotte øje eller et forstørrelsesglas, eller et optisk mikroskop (for produkter med en streggrad mindre end 0,2 mm), en magnet Hvis overfladen er glat, er der ingen synlige partikler og fremmedlegemer, ingen pletter, ingen kanter eller hjørner, udseendet er kvalificeret.
