CN103962555A

CN103962555A - Method for sintering cylindrical or annular sintered NdFeB with height <= 30 mm

Info

Publication number: CN103962555A
Application number: CN201410134426.6A
Authority: CN
Inventors: 王志远; 刘建国; 刘木根; 吴滨; 吕殿国; 肖暾; 曹斌
Original assignee: XUZHOU JINSHI PENGYUAN RARE EARTH MATERIAL FACTORY
Current assignee: XUZHOU JINSHI PENGYUAN RARE EARTH MATERIAL FACTORY
Priority date: 2014-04-04
Filing date: 2014-04-04
Publication date: 2014-08-06
Anticipated expiration: 2034-04-04
Also published as: CN103962555B

Abstract

The invention discloses a method for sintering cylindrical or annular sintered NdFeB with the height <= 30 mm. The method comprises the steps that the NdFeB is placed in a sintering furnace and is heated to be at the temperature of 1050 DEG C to 1115 DEG C under a vacuum state, then heat preservation is carried out, hygienic paper is laid between layers when the cylindrical NdFeB with the height <= 30 mm is placed before sintering, and the annular NdFeB with the height <= 30 mm is wrapped by the hygienic paper; in the sintering process, the temperature rise rate is four DEG C/minute at the stage with the indoor temperature of 300 DEG C to 380 DEG C, and the temperature rise rate is controlled within one DEG C/minute from the stage with the indoor temperature of 300 DEG C to 380 DEG C to the stage with the indoor temperature of 1050 DEG C to 1115 DEG C. The hygienic paper is added between the layers of the cylindrical product or the annular product is wrapped by the hygienic paper, the temperature rise rate is reduced, the problems of cracks, adhesion and air holes in the sintering process can be solved, the product percent of pass is improved, the furnace charge quantity is increased, the equipment utilization rate is greatly improved, high temperature resisting materials with the granularity of 10 microns to 60 microns cannot enter a vacuum system in the vacuum pumping process, a main valve, a rough suction valve and a valve sliding pump cylinder are prevented from being damaged, and the equipment service life is prolonged.

Description

The sintering method of a kind of height≤30mm cylinder or ring-like sintered NdFeB

Technical field

The present invention relates to a kind of sintering method of sintered NdFeB, particularly relate to the sintering method of a kind of height≤30mm cylinder or ring-like sintered NdFeB.

Background technology

The sintering of sintered NdFeB refers to performance and the usability in order further to improve magnet, improve the contact property between powder, improve intensity, make magnet there is high performance microstructure characteristic, green compact need to be heated to the temperature below powder matrix phase fusing point and be incubated the technique of a period of time.

Conventional vacuum-sintering flow process: static pressure such as moulding → wait → exotic material is laid between two magnet contact-making surfaces (is equivalent to suppress green compact product) → and be placed in sintering magazine → filling with inert gas protects → enters stove → vacuumize → heating → tempering.

By particle diameter at 10um～60um exotic material powder, as the one in graphite powder, alumina powder, magnesia powder or refractory ceramics, solve product scorification problem has not occurred in sintering process, due to 10um～60um exotic material fine size, while vacuumizing, very easily enter vacuum system, to main valve, slightly take out the sliding pump cylinder of valve, valve and cause damage, reduce service life of equipment.

The magazine size of sintered NdFeB is mostly 300mm*220mm*65mm or 320mm*240mm* (75～80) mm, 300 kilograms of sintering furnaces, prepare conventional Ф 9mm～Ф 33mm, and when neodymium iron boron cylinder, magazine can be put 40～45 boxes, folding is heavily about 400 kilograms, utilization rate of equipment and installations >=100%.

But, in the time that sintering height is less than the small column of 30mm, taking Ф 9(± 0.05) mm*30(± 0.05) mm be example, blank product Ф 9.6mm*31mm after sintering, compacting green compact are of a size of Ф 11.5mm*42mm, use magazine 300mm*220mm*65mm individual layer can fill 306, this magnetic post, and reduced mass is 16.8 grams/, i.e. 5.14 kilograms/box, 300 kilograms of sintering furnace charges are only 205.6 kilograms～231.3 kilograms; Preparation Ф 50mm～Ф 100mm cake, every box is placed two, 1.942 kilograms/; Every box charge is 3.884 kilograms, and 300 kilograms of sintering furnace charges are for being only 155.36 kilograms～174.78 kilograms; In the time of sintering (Ф 150mm～Ф 200mm) * 30mm, every box only can fill 1 disk, 3.974 kilogram/, 300 kilograms of sintering furnace charges are only 158.96～178.83 kilograms, utilization rate of equipment and installations is reduced to 35.32%～37.35%, and, between sequin, easily cause the adhesion of material material phase.Meanwhile, in the time of the cake of sintering diameter >=50mm or annulus neodymium iron boron, because being is directly positioned over magazine bottom sintering, product easily causes adhesion with magazine, causes product to ftracture in the time shrinking.

Summary of the invention

The object of this invention is to provide the sintering method of a kind of height≤30mm cylinder or ring-like sintered NdFeB, the cracking can solve sintering time and pore problem, improve product percent of pass.

For achieving the above object, the technical solution used in the present invention is:

The sintering method of a kind of height≤30mm cylinder of the present invention or ring-like sintered NdFeB, that neodymium iron boron is inserted in sintering furnace, insulation after being heated to 1050～1115 DEG C under vacuum state, when sintering, be 4 DEG C/min in room temperature to (300～380) DEG C stage heating rate, heating rate is controlled at 1 DEG C/min by (300～380) DEG C to (1050～1115) DEG C stage.

Compare with existing vacuum sintering technology, NbFeB sintered method of the present invention, adopt the slow technique heating up, while being sintering, it is 4 DEG C/min at room temperature to (300～380) DEG C stage heating rate, heating rate is controlled at 1 DEG C/min by (300～380) DEG C to (1050～1115) DEG C stage, can avoid cracking and pore, and product percent of pass is improved greatly.

Brief description of the drawings

Fig. 1 is sintering operation schematic flow sheet of the present invention.

Detailed description of the invention

Below in conjunction with embodiment, the present invention will be described.

In the sintering process of green compact, will there is a series of physicochemical change.First, the gas (comprising steam) of powder particle surface absorption is got rid of, evaporation and the volatilization of organic matter (oil that may be stained with in static pressure as waited or antioxidant and the lubricant etc. adding), the elimination of stress, the reduction of the oxide of powder particle surface, the Recovery and recrystallization of distortion powder particle.Secondly, atom diffusion, material migration, the contact between particle changes physical chemistry contact into by Mechanical Contact, forms the combination of metallic bond and covalent bond.Finally, the contact-making surface between powder expands, and occurs sintering neck, is next that sintering neck length is large, and density improves, grain growth etc.The porosity of powder green compact is large, and surface area is also large, and therefore surface can be also large, also has distortion of lattice energy simultaneously, makes powder green compact on the whole in upper state.From the angle of energy, this is unsettled, has spontaneously sintering and the tendency and the driving force that are bonded to a DB.Therefore, under the condition of uniform temperature, in the situation that dynamics allows, the contact between powder particle will be spreaded over a whole area from one point, to reduce surface area and surperficial energy.Along with the expansion of intergranular contact-making surface, green compact start to shrink and are densified, finally become a sintered body.In brief, to be exactly powder combination become the process of blank from green compact to sintering.

Sintering process process of the present invention:

(1) sintering annulus product, most of product substance is more than 1Kg, and when sintering, heating rate is 4 DEG C/min in room temperature to (300～380) DEG C stage; This stage is that product discharges adsorbed gas and temperature rise period; Between powder particle, metal contact area increases the stage, in this stage, be first to get rid of the gas that is adsorbed on powder particle surface, organic evaporation and volatilization (gasoline etc.), Main physical chemical process is, powder surface Reduction of Oxide, between the metal powder granulates in green compact, metal contact area increases, reply (elimination of stress) and the recrystallization of distortion powder particle; The sintering stage: powder particle dissolution phase, its main process is that powder particle dissolves mutually, the solid solution volume dispersion hardening of alloy composition, volumetric expansion.This is the Main Stage of sintering process, 800～1000 DEG C of temperature ranges.

(2) holding stage: in the solid solution homogenising stage, the process at this moment occurring is solid solution homogenising and grain growth, volume contraction, density improves and alloy merges, 1050～1115 DEG C of temperature ranges.

Alloying component difference, the temperature range of three phases is also different, mainly contains three temperature stages:

1. low-temperature space: eliminate blank internal residual stress, get rid of gas and the volatility foreign material etc. of absorption.

2. middle warm area: blank starts to shrink, and starts to spread and form connection between metallic particles, continues to get rid of the gas of absorption.

3. high-temperature region: blank shrinks rapidly, space nodularization is dwindled, and is coupled to interface between particle, and with the prolongation grain growth of temperature retention time, finally forms fine and close sintered body.

(3) each stage is focused on problem difference: holding stage (1050～1115) DEG C now slows down heating rate, 1 DEG C/min, small product size is shunk, and it is external heat that product is heated, heat by outer and in, if heating rate is fast, also does not shrink the outside inside of shrinking of product, and there is pore at the center of can causing, affects magnet overall performance, technique of the present invention has solved cracking and pore problem, has greatly improved product percent of pass.

As a further improvement on the present invention, before sintering, place mat toilet paper between layers in the time that height≤30mm column type neodymium iron boron is put, the ring-like neodymium iron boron of highly≤30mm wraps up with toilet paper.As shown in Figure 1; the sintering method of a kind of height≤30mm cylinder of the present invention or ring-like sintered NdFeB, its operating process is: and static pressure such as moulding → wait → first put one deck compacting green compact → common toilet paper that tiles → put again in the above one deck product → be placed in is in sintering magazine → and filling with inert gas protects → enters stove → vacuumize → heating → tempering.

Neodymium iron boron product can be bonded together in the time of extruding and stack in sintering process, have a strong impact on the qualification rate of product, the present invention takes height≤30mm column type neodymium iron boron to put after one deck product, and tiling one deck toilet paper, on top puts one deck neodymium iron boron cylinder again; To all wrapping up with toilet paper after the static pressure such as height≤30mm ring products, stack is placed in magazine, removes toilet paper and carry out firsts and seconds tempering after sintering.Solve like this product adhesion problems, ensured product percent of pass, simultaneously, adopt said method can not make the exotic material of 10um～60um granularity in the time vacuumizing, enter vacuum system, prevent main valve, slightly taken out the infringement of valve, the sliding pump cylinder of valve, improved service life of equipment.

Claims

1. the sintering method of height≤30mm cylinder or ring-like sintered NdFeB, neodymium iron boron is inserted in sintering furnace, under vacuum state, be heated to insulation after (1050～1115) DEG C, it is characterized in that: when sintering, be 4 DEG C/min in room temperature to (300～380) DEG C stage heating rate, heating rate is controlled at 1 DEG C/min by (300～380) DEG C to (1050～1115) DEG C stage.

2. the sintering method of a kind of height≤30mm cylinder according to claim 1 or ring-like sintered NdFeB, it is characterized in that: before sintering, place mat toilet paper between layers in the time that height≤30mm column type neodymium iron boron is put, the ring-like neodymium iron boron of highly≤30mm wraps up with toilet paper.