Talking about How to Do the Four Preventions Work in the Production of NdFeB Permanent Magnet Material

- Nov 23, 2017 -

Sintered NdFeB permanent magnet material is made by powder metallurgy process, the process is as follows: raw material processing → ingredients → smelting → milling → magnetic field orientation and pressure type → compacting → tempering aging → machining and surface treatment → testing . From the process can be seen that the entire process is a systematic project, especially high-performance Nd-Fe-B permanent magnet materials, the production process of each process have the product performance of the "decision" and "right to ". In order to produce high-performance NdFeB permanent magnet materials, organizations and managers should pay attention to every aspect of the production process, and guide employees to pay attention to every detail of the process, which is to require employees to do the most basic "anti-oxidation , Anti-confusion, anti-impurities, anti-damp "" four defenses. " To produce a high-quality requirements of NdFeB permanent materials to lay a solid foundation.

In order to ensure the quality of sintered Nd-Fe-B permanent magnetic materials, our daily basic work should be carried out around the work of "four defenses", that is, to prevent oxidation, prevent confusion, prevent impurities and prevent dampness.

First, anti-oxidation

NdFeB is a rare earth permanent magnet material, the formula contains a larger proportion of rare earth elements. The characteristics of rare earth elements is the chemical nature is very lively, easy to react with the oxygen in the air, generating rare earth oxides, such as neodymium and oxygen react to generate neodymium oxide. Rare earth oxide, the magnetic properties of the product will be greatly reduced, therefore, in our NdFeB material production process, how to do "anti-oxidation" work is a very important quality links.

First of all, when purchasing raw materials, we must ensure the purity of rare earth metals and reduce the oxygen content. Materials stored, sealed with plastic bags, into the barrel, to avoid contact with air, high quality materials at the end of the ingredients, filled with nitrogen to protect and bandage bag. When the ingredients of small pieces of neodymium and other rare earth metal materials, try not to cut spare too long, that time will be oxidized, such as metal neodymium red mouth, metal praseodymium will be white.

Second, we must ensure that the atmosphere of the furnace, the new mold, the new stove or furnace stove, must be dried before the formal start of production; smelting furnace valves, connecting parts and other tightness to ensure normal, do To airspeak, leaking, oil spills; vacuum pump (mechanical pump, Roots pump, diffusion pump) must give full play to the role of good ventilation should be timely repair and maintenance, vacuum hygiene according to the provisions of regular cleaning process, Point, to make the furnace vacuum can be guaranteed to make a good product.

In the milling process coarse broken, broken, air mill, stirring must be filled with nitrogen technology protection. Check the nitrogen pressure of the stainless steel bucket (plastic bag) that is charged at any time, and check whether the stainless steel bucket valve or plastic bag leaks before use. When using it, it should be promptly replaced or the new coat of the jacket should be handled. Powder processing found that fever should be taken to cool nitrogen and other measures to prevent oxidation.

In the molding process should pay close attention to said powder box, nitrogen box oxygen content, to ensure that the values below the process to prevent oxidation of magnetic powder. Oil stripping, into the furnace process, the time required to be compact. Especially high-performance products is particularly important, must be based on process requirements in nitrogen protection box operation. Prevention products water chestnut, corner oxidation.

In addition, we should always pay attention to the purity of argon used, found that abnormal should be handled in time. Often observe the cooling water temperature, determine the cooling time, baked product temperature is below 80 ℃ to avoid high temperature baked, resulting in product oxidation.

Therefore, the "anti-oxidation" work is an indispensable part of our work on the quality of NdFeB permanent magnet materials. We should start from the practical work,


Second, anti-confusion

Sintered NdFeB according to different performance requirements, such as residual magnetic flux density, coercivity, maximum energy product, etc., with different grades to distinguish between. At present, I use the company mainly N, M, H, SH, UH, EH, AH seven series. Coercivity gradually increases from N to AH. Each series also uses different numbers to distinguish the level of magnetic energy products, such as the N series with N30, N35, N38, N42, N45, N50, N52, etc., the larger the number, the higher the product of magnetic energy.

According to the difference of climate, material and formula, we use "-1" and "- 2" after brand, etc., such as N35-1, N35-2 and so on.

Special performance requirements of the product, plus the last character in the grade description.

Can be seen from the English letters, numbers are different, then the brand, formula, technology, meaning is different. We are based on a variety of customer orders, with different grades and processes to produce, to meet customer needs.

Therefore, we must pay attention to the ingredients and melting operations, "anti-confusion" work, do not make the wrong number, according to a single formula to calculate the weight of the ingredients, weighed promptly put the correct identification plate, smelting operators to be based on Grades accurately record raw data records and smelter tracking orders. When the spout is released, be sure to send the identification plate and tracking list of each spindles to the warehouse exactly and timely for verification. At the same time the workshop should check and supervise the above situation at any time. The last proof spindle carefully proofreading, said after filling certificate, and then placed in the barrel after verification. Material proofing and then proofing out of barrel logo is consistent with the barrel of the certificate, so inconsistent does not fat.

Melting should not be different grades of raw materials, crucible alloy liquid, baked after mixing the spindle. Raw materials and ingredients of the group to promptly on the origin of all kinds, origin, performance, specifications, content or number of materials in the ingredients must pay attention to strengthen proofing verification to prevent errors.

In the milling process, the spindle coarse broken, broken must keep up with the "melting list" and found abnormal spindle feedback timely smelting workshop traceability. All processing equipment must be marked with a brand name, all "pending" and "processed" products must have a logo and other brands. Processing equipment and discharge barrel must be clean to prevent mixing other brands of powder.

In the molding process, the use of powder in the molding powder before weighing must be carefully checked the identification of single powder and construction orders of the same grade requirements. Said each batch of flour powder box must be cleaned up, to prevent different batches of powder mixture. After molding the product must be clearly marked before flow. In the oil stripping, into the process of the furnace according to into the furnace single, a single product identification to check, correct operation before. Sintered products must be released into the furnace after a single logo, clear and clear, to prevent product confusion.

If the concept is ambiguous, careless, resulting in brand confusion, the product sintered out of performance can not meet customer requirements, it will cause great losses to the company. We hope that all of our staff must take "prevention and confusion" work in a very important position.


Third, anti-impurities

Sintered NdFeB permanent magnet material, which is through the rare earth, iron, boron and other raw materials in the best ratio of organic combination to form Nd2Fe14B main phase and other basic phase, after melting, milling, molding, sintering a series of processes, Finally get a certain magnetic properties, density and size of the magnet. Only qualified magnets can ensure the quality of after-machined sections and inside and outside of the plated product.

From the performance point of view, we have to eliminate the entry of harmful elements to prevent the basic composition of the magnet; To prevent this, we want to prevent the inclusion of impurity elements, so as not to cause the product sintering melting point and shrinkage, the magnets foaming, shrinkage, or After electroplating pickling spots, spalling, etc., affecting product quality. Therefore, the impurities are the enemy of our sintered NdFeB. Market competition is largely reflected in product quality competition, we have to stand firm in the fierce market competition, we must strictly control product quality.

In the process of raw material processing, the raw materials must be handled cleanly, and the oxides that are covered on the surface of raw materials such as neodymium and iron before the ingredients should be cleaned and removed so that there is no oxide. Before using ingredients empty barrel, cans and other clean up.

In the melting process, be sure to pay attention to the crucible, the use of pouring cup. If found corundum, refractory mud shedding phenomenon, be sure to be treated before use, if necessary, timely replacement. When cleaning the vacuum hygiene, it is necessary to cover the smelting mold in time to prevent dust from entering the mold wall and affecting the surface quality of the spindle. Spindles are not allowed to be released after unwinding, should be placed in the stainless steel pot used to pick impurities, carefully inspected and placed in a clean empty barrel, a good logo, timely cover, to prevent dust and other impurities into. Prohibit the spindle in the dusty space exposed, must take appropriate measures.

In the milling of coarse broken, broken in the fracture should always knock open observation, if impurities in a timely manner and feedback before the procedure. Before using a variety of processing equipment must be clean, especially for a long time without the use of equipment must be cleaned with nitrogen gas before the device cavity to prevent the original powder remaining oxide mixed with impurities. Alloy ingots and the use of equipment into the discharge port should be promptly covered. Prohibit the dusty workshop, if necessary, take appropriate dust control measures. In the fine powder mixing process, pay attention to the stainless steel bottle cleaning, prevention of powder in the barrel, impurities, resulting in the last product impurities or oxidation spots.

In the molding process, pay attention to each must be said that the dust left powder box clean up, in case these oxidized starch mixed, resulting in product impurities or oxidation spots.

Crude impurities are very small things, but once mixed into the product, but made a devastating horse, affecting product quality, the company caused great losses. Therefore, we must not underestimate the impurities, because of small losses, the consequences are very serious. We must attach great importance to "preventing impurities".


Fourth, to prevent damp

NdFeB rare earth permanent magnet formulations contain a large proportion of rare earth elements. The characteristics of rare earth elements is the chemical properties are very lively, easy to react with the oxygen in the air to generate rare earth oxides, the magnetic properties of products will be greatly reduced. When damp raw materials or equipment, the use of fixtures and other high moisture content, the processing of high temperature process, water molecules easily decomposed into oxygen and hydrogen and neodymium and other rare earth elements chemical reaction. Therefore, in our NdFeB material production process, how to do "anti-damp" work is a key part of quality assurance.

In the NdFeB permanent magnet material processing, the melting process of "anti-damp" work: raw materials are not processed or after the timely smelting, must have the necessary moisture-proof measures, into a special plastic bag or drum moisture . On the release of the spindle must be promptly loaded into the barrel and cover; empty furnace equipment must be promptly vacuum protection. The above measures are to prevent raw materials, products and equipment to absorb moisture in the air and damp.

Milling process of "anti-damp" work: control of indoor temperature and humidity, if necessary, open the dehumidifier, air conditioners and so on. For the processing of powder material is strictly prohibited wet barrels. Mixing the aviation gasoline used in the water content control, because gasoline in the air is also easy to absorb moisture.

Sintering process, "anti-damp" work: promptly closed after the release of the furnace vacuum protection, to prevent equipment adsorption of moisture in the air and damp. Sintering basin must be dried and other measures to ensure its drying, drying before use to ensure that the sintering pot to prevent moisture during sintering process.

The daily production process seems to be a trifling matter for "damp proofing" work. It is a relatively simple task, but it plays a crucial role in ensuring the quality of the product. Therefore, we should focus our daily "anti-damp" work.

In short, as a sintered Nd-Fe-B permanent magnetic material processing, because of its production process for each process have a vote on the performance of the product "decision" and "negative" determine the product's pass or not. Therefore, every aspect of the production process should be taken seriously, daily production management should start from the most basic details, that is to say from the "anti-oxidation, anti-confusion, anti-damp" Work started, thus ensuring the quality of our products, improve product quality.

Article from NdFeB Industry Network

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