Sintering box

Abstract

The utility model relates to the technical field of magnetic material production, in particular to a sintering box for loading and sintering neodymium iron boron products. The sintering box comprises a box body with an upward opening, a plurality of placing positions used for placing magnet blanks to be sintered are arranged at the box bottom of the box body, each placing position is provided with a plurality of granular protrusions which extend upwards and are arranged in an array mode, the shapes and the sizes of all the granular protrusions are the same, the width W of each granular protrusion ranges from 0.5 mm to 3 mm, and the width W of each granular protrusion ranges from 0.5 mm to 3 mm. And the number of the granular bulges at each placing position is 0.25-4 / cm < 2 >. According to the utility model, the defects of shrinkage cracking, strain, edge collapse and the like in the sintering process of the neodymium iron boron product can be reduced or even avoided, and the defective rate and the production cost can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of magnetic material production, specifically relates to a sintering box reducing shrinkage cracking of neodymium iron boron product. BACKGROUND

[0002] Neodymium iron boron product will be placed in the sintering box made of graphite and other materials before sintering, in order to reduce the friction in the sintering shrinkage process, corundum powder will be laid on the bottom of the sintering box, but the irregular shape and rough surface of corundum powder particles lead to the easy production of cracks such as Figure 1 The black crack surface 6, 7 exists at the cracking position. In addition, the larger the mass of the neodymium iron boron product, the more likely the black crack surface appears. In addition, the corundum powder also has the problems of high use cost (one-time consumable), the risk of product pollution by surface water and oil immersion, and uneven laying of corundum powder to cause local stress concentration and deformation. UTILITY MODEL CONTENT

[0003] The utility model aims at providing a sintering box which can reduce the sintering defective rate of neodymium iron boron product and has low production cost.

[0004] In order to achieve the above-mentioned purpose, the utility model adopts a sintering box, which comprises an upwardly open box body, a plurality of placement positions for placing sintered magnet blanks are arranged at the bottom of the box body, each placement position is provided with a plurality of granular protrusions which extend upward and are arranged in an array, all the granular protrusions have the same shape and size, the width W of the granular protrusion is 0.5-3 mm, and the number of granular protrusions at each placement position is 0.25-4 per square centimeter.

[0005] When the sintering box is used for sintering neodymium iron boron product, the sintered magnet blanks to be sintered are placed in the placement positions of the sintering box according to the pre-planning, so that each sintered magnet blank is supported on a plurality of granular protrusions, thereby achieving isolation, and then the sintering of the magnet blanks can be carried out according to the normal procedure.

[0006] The sintering box does not need to spread corundum powder, can avoid the problem of local stress concentration caused by uneven laying of corundum powder, does not need to consider the pollution of corundum powder to the magnet blanks, can reduce the production cost, and can reduce the friction when the magnet blanks shrink and slide, so that the defects such as neodymium iron boron scratch cracking and corner drop are greatly reduced, thereby reducing the defective rate. The regularly arranged granular protrusions provide isotropic sliding guide for the magnet blanks, the uniformity of the magnet blank shrinkage is improved, the product size consistency is better, the sintering quality of the neodymium iron boron product is further ensured, and the defective rate is reduced.

[0007] The granular protrusions on the sintering box can be separately produced and then assembled and fixed on the sintering box, or can be integrally produced with the sintering box; when the manufacturing process of the granular protrusions and the box bottom and the box wall is a split structure, the material of the granular protrusions is one or more of molybdenum, titanium alloy, titanium oxide, aluminum oxide and zirconium oxide, and the material of the box bottom and the box wall is one of graphite, molybdenum, titanium alloy and stainless steel.

[0008] Preferably, the granular protrusions are integrally formed with the box bottom. When the manufacturing process of the granular protrusions and the box bottom and the box wall is an integral type, the manufacturing material can be one of graphite, molybdenum, titanium alloy and stainless steel.

[0009] The integrally formed structure enables the granular protrusions to be closely combined with the box bottom and become an integral whole, and compared with the split structure, there is no connection point or joint, thereby avoiding the situation that the granular protrusions fall off from the box bottom due to external force or thermal expansion in the sintering process and the like, and ensuring normal use and reliability of the sintering box.

[0010] Preferably, the granular protrusions have a semispherical structure.

[0011] The top of the semispherical structure is circular, and when the magnet blank of the neodymium iron boron product to be sintered is placed on the granular protrusions, compared with other shapes such as pointed or square protrusions, a more stable support can be provided when contacting the magnet blank, and the pressure of the magnet blank on the granular protrusions is evenly distributed along the semispherical surface, avoiding local deformation or cracking of the magnet blank due to pressure concentration, and effectively protecting the integrity of the neodymium iron boron product.

[0012] Preferably, the diameter D of the granular protrusions is 1mm-2mm.

[0013] The granular protrusions with a diameter of 1mm-2mm can form relatively uniform contact with the bottom of the neodymium iron boron product, so that the support force received by the neodymium iron boron product during sintering is more evenly distributed, effectively reducing problems such as product deformation and cracking caused by uneven support. Compared with smaller protrusion diameters, the protrusions with a diameter of 1mm-2mm can provide sufficient support points in a unit area. At the same time, for neodymium iron boron products of different sizes and shapes, the granular protrusions with a diameter of 1mm-2mm can better adapt to different sizes and shapes, whether it is a smaller sheet product or a larger block product, stable support can be achieved by reasonably arranging the number and distribution of protrusions, thereby enhancing the versatility and application range of the sintering box.

[0014] Preferably, the surface roughness Ra of the granular protrusions is ≤1.6μm.

[0015] The granular protrusion has a low surface roughness, which helps to reduce the friction coefficient between the Nd-Fe-B product and the granular protrusion, and the Nd-Fe-B product will shrink during the sintering process, and the low friction coefficient can ensure that the product can shrink relatively freely, and reduce the local stress concentration caused by friction resistance.

[0016] Preferably, the surface roughness Ra of the granular protrusion is ≤0.6 μm.

[0017] Preferably, the number of granular protrusions at each placement site is 1-2 per cm 2 The sintering box can be used for sintering of the blank of the Nd-Fe-B product with a surface greater than 2 cm2 or even larger.

[0018] The number of 1-2 per cm2 protrusions is relatively easy to achieve during the manufacturing process of the sintering box, without the need for overly complex processing technology, thereby reducing production cost and process difficulty.

[0019] Preferably, the plurality of granular protrusions are evenly distributed in an array on the bottom of the box.

[0020] The array distribution of the granular protrusions on the bottom of the box enables the sintering box to adapt to a plurality of different sizes of magnet blanks, and no matter the size and shape of the magnet blank, a suitable placement site can be found on the sintering box, making the planning of the placement site more convenient, enabling the granular protrusions to uniformly support the blank, improving the application range of the sintering box, and reducing the inconvenience and cost increase caused by replacing different models of sintering boxes.

[0021] The sintering box does not need to be used with corundum powder, which effectively avoids the problem of product contamination by corundum powder. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The sintering box of the present application is used for separating the neodymium-iron-boron product from the corundum powder, so as to avoid the defects.

[0023] Figure 2 A structure diagram of the sintering box of the present application.

[0024] Figure 3 A structure diagram of the sintering box of the present application. DETAILED DESCRIPTION

[0025] The present application will be further described below according to the drawings and specific embodiments.

[0026] As shown in Figure 2 and Figure 3 , the present embodiment discloses a sintering box, which comprises an upwardly open box body, the box body comprising a box bottom 2 and a box wall 3, and a plurality of placement positions for placing the sintered magnet blank 4 are arranged at the box bottom 2 of the box body, each placement position is provided with a plurality of granular protrusions 1 extending upwardly and arranged in an array, and the granular protrusions 1 are of the same shape and size. Among them, the density of the granular protrusions 1 under the sintered surface of the sintered magnet blank 4 per square centimeter is 0.25 / cm 2 , and the plurality of granular protrusions are evenly distributed in an array at the box bottom 2.

[0027] The granular protrusions 1 of the present embodiment are integrally formed with the box bottom 2 and the box wall 3, the granular protrusions 1, the box bottom 2 and the box wall 3 are all made of stainless steel, the granular protrusions 1 are in a hemispherical structure, the diameter D of the granular protrusions 1 is 2mm, and the surface roughness of the granular protrusions is Ra=0.6μm.

[0028] As shown in Figure 2 , the magnet blank with a size of 40*50*60mm (i.e. the sintered surface is 40*60mm) is placed on the six granular protrusions 1 of the sintering box, and then sintered according to the conventional process. After sintering, a 3mm thick slice is cut from the sintered surface of the neodymium-iron-boron magnet by wire cutting, and then the slice is knocked. It is found that the fracture surface has no black crack surface caused by shrinkage cracking. However, the neodymium-iron-boron magnet obtained by the sintering method of laying dry corundum powder will have a black crack surface caused by fracture shrinkage cracking when a slice is obtained in the same way, and a typical black crack surface is shown in Figure 1 .

[0029] The sintering box of the present embodiment does not need to be used with corundum powder, which effectively avoids the problem of product contamination by corundum powder. The granular protrusions of the present application can uniformly support the magnet blank to be sintered, the friction during the sintering shrinkage process is small, which can reduce or even avoid the generation of defects such as shrinkage cracking, scratching and edge collapse of the neodymium-iron-boron product during the sintering process, and can reduce the rate of defective products.

Claims

1. A sintering cartridge comprising an upwardly open cartridge body, characterised in that: The box body is provided with a plurality of placement positions for placing the to-be-burnt magnet blank at the box bottom, each placement position is provided with a plurality of granular protrusions extending upward and arranged in an array, all the granular protrusions are of the same size, the width W of the granular protrusion is 0.5-3 mm, and the number of the granular protrusions at each placement position is 0.25-4 per cm 2 .

2. The sintering box according to claim 1, characterized in that: The granular protrusions are integrally formed with the box bottom.

3. The sintering box according to claim 1, characterized in that The granular protrusions and the box bottom are two independent components.

4. The sintering box according to claim 1 or 2 or 3, characterized in that: The granular protrusions are in a semi-spherical structure.

5. The sintering box according to claim 4, characterized in that: The diameter D of the granular protrusions is 1mm-2mm.

6. The sintering box according to claim 1 or 2 or 3, characterized in that: The surface roughness Ra of the granular protrusions is ≤1.6μm.

7. The sintering box according to claim 6, characterized in that: The surface roughness Ra of the granular protrusions is ≤0.6μm.

8. The sintering box according to claim 1 or 2 or 3, characterized in that: The number of granular projections at each placement site is 1-2 per cm 2 .

9. The sintering cartridge of claim 1 or 2 or 3, wherein: The granular protrusions are evenly distributed in an array on the box bottom.

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