1983165438+1October 29th, at the metal seminar, Sumitomo Special Metals Company of Japan first proposed the manufacture of NdFeB permanent magnet materials, which really "stirred up a thousand waves with one stone". Since then, the research upsurge of NdFeB new magnetic metals has been set off. For more than ten years, patents in this field have been increasing day by day, and Sumitomo Special Metals Company of Japan has also made progress in this field.
Before the 1980s, Sumitomo Special Metals Co., Ltd. in Japan had been lagging behind General Motors in the research of magnetic metals. In order to break the monopoly position of American General Motors, the boss of Sumitomo offered a large sum of money to the inventor of new magnetic metal with good quality.
"It's a big reward. There must be a brave man." A technician named Shinji Sagawa stepped forward and accepted the task of the company to study new magnetic metals.
Sagawa is short, unattractive and usually taciturn. He accepted the task not for the bonus, but for national pride, trying to catch up with and surpass the United States in this respect. At first, the research work was not as smooth as expected. However, after repeated failures, Sagawa learned lessons from reality, summed up experience, and got closer and closer to success. 1in the summer of 983, he finally succeeded in manufacturing a permanent magnet material called NdFeB, which was a blockbuster.
The composition of Sagawa permanent magnet metal is as follows: neodymium and praseodymium account for1-18%, boron accounts for 6- 12%, vanadium accounts for 2-6%, and the rest is iron and cobalt. There are two manufacturing methods: first, melting in an electric furnace, and then heat-treating at 700- 1 100℃ in an inert gas atmosphere to form an antioxidant protective film around the crystal grain, and then performing conventional pressing, sintering and heat treatment; The second method is to add vanadium or cobalt after the melting process, in order to precipitate it at the grain boundary during the sintering process to form an oxidation protective film, and then carry out conventional sintering and heat treatment.
The NdFeB permanent magnet prepared by the above two methods has the following characteristics: first, the coercivity of the magnet is greatly improved, and its magnetic coercivity can reach 15.2-2 1Koe, and the maximum magnetic energy product is 30MGoe；; Secondly, it is particularly stable to temperature, which is three times higher than that of traditional permanent magnet materials; Third, the corrosion resistance is strong, which is twice as high as that of traditional materials.
Sagawa's invention made Japan not only catch up with the United States in the production of permanent magnet metal materials, but also surpass the United States in a short time.
However, the technicians of American General Motors can't bear to see Japan catch up. In 1990, they also put forward a new method for manufacturing permanent magnetic materials-NdFeB-type magnetic oriented sheet. In this method, isotropic banded powder particles are prepared by melt spin quenching, and then the powder particles are heated into paste by a plasma spray gun, pushed into the gap between a pair of counter-rotating rollers, and then pressed into powder sheets, thus making anisotropic high-quality magnetic materials. The material after this operation is even better than Sagawa's invention.
Not to be outdone, Mr. Sasakawa made great improvements on his previous inventions and put forward new measures. He added a small amount of copper to NdFeB magnets, which greatly broadened the heat treatment temperature range with high coercivity. After adding copper, the optimum heat treatment temperature range of the magnet is widened from the original 10 to 300 degrees, thus making a better permanent magnet.
It is worth mentioning that China scientists have also made new contributions in the competition upsurge of permanent magnet materials. They created a new sintering method, using induction heating sintering instead of traditional sintering and heat treatment. In this way, the sintering density of the magnet can reach more than 95% of the theoretical value within 5 minutes, and the maximum magnetic energy product can reach more than 280kJ/m3. Because the sintering time is much shorter than the traditional process, the excessive growth of magnet grains can be avoided and greatly improved.
Obviously, since 1983, the competition of NdFeB permanent magnet materials has become more and more fierce, and the speed of progress is rare. The competition will bring new technology to people.