Residual magnetism gradient distribution controlled NdFeB permanent-magnet material and preparation method thereof

Abstract

The invention belongs to the field of a magnetic field, and particularly relates to a residual magnetism gradient distribution controlled NdFeB permanent-magnet material and a preparation method thereof. The NdFeB permanent-magnet material comprises the chemical constituents based on percent by mass: 28-30% of Nd, 0.3-0.7% of Ga, 4-6% of Co, 0.8-1.2% of B, 0.18-0.28% of Al, 0.1-0.3% of Cu and 0.06-0.1% of M with balance being Fe, wherein the M is one or more of Dy, Ho and Tb. The NdFeB permanent-magnet material is prepared by employing gradient temperature control and pressure control hot-pressing and segmented variable-flow-speed and variable-pressure thermorheological process, is simple in process and short in period, and moreover, the prepared permanent-magnet material also has the advantages of residual magnetism controllability.

Description

technical field [0001] The invention belongs to the field of magnetic materials, in particular to a NdFeB permanent magnet material with controllable remanence gradient distribution and a preparation method thereof. Background technique [0002] Using nuclear magnetic resonance to analyze petroleum cores, porosity (total porosity, effective porosity, clay-bound water porosity, etc.), free fluid index (percentage of movable fluid), pore size distribution, and permeability can be obtained from a rock sample. A variety of parameters, with significant advantages of non-destructive testing, one machine with multiple parameters, and the same multiple parameters. my country's oilfields are dominated by continental sedimentary oilfields. Its main feature is that there is serious heterogeneity in the reservoir, so it is necessary to use nuclear magnetic resonance core analysis. The magnet system is the core component of the nuclear magnetic resonance core analyzer, which can provid...

AI Technical Summary

Problems solved by technology

One is that for an analyzer with a constant magnetic field, in order to generate a gradient magnetic field, additional gradient coils and other signal conversion and amplification systems need to be added to the analyzer, which on the one hand increases the complexity of the system and makes the system reliable. The performance and stability will decrease, and the cost will increase

On the other hand, the gradient coil will generate eddy current, which affects the system signal-to-noise ratio and gradient switching speed

The other is an analyzer with a fixed magnetic field gradient. Through structural design, it generates a constant gradient magnetic field between the air gaps of the pole plates. The structural design of this analyzer is relatively complicated, requiring magnets, yokes, and gradient plates. etc. to cooperate with the assembly, the production process is complicated, and its gradient is not variable, and the test conditions are poorly adaptable

[0004] Not only in the field of oil exploration, but also in many fields such as medical treatment, fuel cells, environmental science or in different industrial application environments, gradient magnetic fields will be used, and the corresponding gradient magnetic fields are passed through permanent magnets, soft magnetic materials (yokes) These devices are often designed more complicated, especially in the selection of electromagnetic materials, the shape and size design of magnetic poles, yokes and iron cores, the winding method of excitation coils, Parameter setting, reasonable layout of coils and cooling devices and many other aspects require strict design and exploration. Obviously, these tasks have brought challenges to the design of gradient magnetic field generators.

The traditional hot-pressing / thermo-rheological method adopted in Chinese invention patent application CN 102982935 A etc. cannot prepare magnets with controllable remanence gradient distribution

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