Die assembly for orientation pressing of magnetic material, preparation method of die assembly and orientation pressing method

Abstract

The invention discloses a mold assembly for orientation pressing of a magnetic material, a preparation method of the mold assembly and an orientation pressing method. The mold assembly comprises a main body, a lower clamping sleeve, an upper clamping sleeve and a pressing head, the main body comprises a first main body and a second main body; a first mold cavity is formed in the middle of the side face of the first body, and a wear-resisting layer is arranged on the surface of the first mold cavity. The first mold cavity divides the first main body side face into a first main body side face first part and a first main body side face second part, and the surfaces of the first main body side face first part and the first main body side face second part are provided with transition layers; a second die cavity is formed in the middle of the side face of the second body, and a wear-resisting layer is arranged on the surface of the second die cavity. The second mold cavity divides the second body side face into a second body side face first part and a second body side face second part, and the surfaces of the second body side face first part and the second body side face second part are provided with transition layers. The mold assembly is high in high-pressure bearing capacity and weak in magnetic shielding effect.

Description

Technical Field

[0001] The invention relates to a mold component for orientation pressing of magnetic materials, a preparation method thereof and an orientation pressing method. Background Art

[0002] The manufacturing process for permanent magnet materials primarily involves preparing permanent magnet powder, pressing, and sintering. The pressing step involves placing the permanent magnet powder into a mold cavity, applying an aligning current, and using upper and lower mold rods to compress the permanent magnet powder within an aligning magnetic field. The pressing process determines the magnet's geometry, size, and degree of orientation, factors that directly impact its ultimate performance.

[0003] CN107958776A discloses a molding and orientation device comprising an upper slide of a press, an upper film, a mold cavity, a coil head, a lower mold, a magnetizing coil, and a lower slide of the press. The upper film is mounted to the lower end of the upper slide of the press, and the lower mold is mounted to the upper end of the lower slide of the press. The upper mold is located directly above the lower mold, with a mold cavity sandwiched between the upper and lower molds. The mold cavity accommodates a blank. The coil head is mounted to the side of the mold cavity, and the magnetizing coil is mounted at the upper and lower ends of the coil head.

[0004] CN119207991A discloses a mold structure for compacting NdFeB powder. The mold outlet is designed with a certain curvature, i.e., the mold outlet is rounded. This reduces shear stress on the green body during demolding, thereby reducing cracking and improving green body strength. The curvature of the mold outlet satisfies the conditions of 0.05 ≤ r / W ≤ 0.1 and 0.05 ≤ r / h ≤ 0.1, where r is the fillet radius, W is the length or width of the mold, and h is the height.

[0005] The above molds do not have the advantages of strong high-pressure bearing capacity, weak magnetic shielding effect and easy demoulding. Summary of the Invention

[0006] In view of this, one object of the present invention is to provide a mold assembly for orientation pressing of magnetic materials, wherein the mold assembly has strong high-pressure bearing capacity and weak magnetic shielding effect. Furthermore, the mold assembly is easy to demold. Another object of the present invention is to provide a method for preparing the mold assembly. Yet another object of the present invention is to provide an orientation pressing method.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions.

[0008] In one aspect, the present invention provides a die assembly for oriented pressing of magnetic materials, comprising a main body, a lower ferrule, an upper ferrule, and a pressing head;

[0009] The main body includes a first main body and a second main body;

[0010] The first body is formed by a first body curved surface, a first body side surface, a first body top surface and a first body bottom surface; the first body top surface and the first body bottom surface are substantially parallel;

[0011] A first mold cavity is formed in the middle of the first main body side surface, the first mold cavity runs through the length direction of the first main body side surface, and the surface of the first mold cavity has a wear-resistant layer; the first mold cavity divides the first main body side surface into a first portion of the first main body side surface and a second portion of the first main body side surface, and the surfaces of the first portion of the first main body side surface and the second portion of the first main body side surface have a transition layer;

[0012] The second body is formed by a second body curved surface, a second body side surface, a second body top surface and a second body bottom surface; the second body top surface and the second body bottom surface are substantially parallel;

[0013] A second mold cavity is formed in the middle of the second main body side surface, the second mold cavity runs through the length direction of the second main body side surface, and the surface of the second mold cavity has a wear-resistant layer; the second mold cavity divides the second main body side surface into a first portion of the second main body side surface and a second portion of the second main body side surface, and the surfaces of the first portion of the second main body side surface and the second portion of the second main body side surface have a transition layer;

[0014] The lower ferrule is provided with a lower ferrule slot, and the lower ferrule slot is configured to accommodate the bottom of the main body;

[0015] The upper ferrule is provided with an upper ferrule slot, and the upper ferrule slot is configured to accommodate the top of the main body; the upper ferrule is provided with a mold cavity communicating hole;

[0016] The pressure head includes a main body and a force-bearing part; the top of the main body is connected to the bottom of the force-bearing part, and the main body can extend into the mold cavity formed by the first mold cavity and the second mold cavity; the surface of the part of the main body extending into the mold cavity has a wear-resistant layer.

[0017] According to the mold assembly of the present invention, preferably, the mold assembly further comprises a moving spacer;

[0018] The movable pad is matched with the shape of the mold cavity, and the surface of the movable pad is provided with a wear-resistant layer; and two movable pads are provided.

[0019] According to the mold assembly of the present invention, preferably, the main body, the pressing head and the movable pad are formed of a first non-magnetic steel, the Rockwell hardness of the first non-magnetic steel is 53-67, and the magnetic permeability of the first non-magnetic steel is ≤1.8;

[0020] The lower ferrule and the upper ferrule are formed of a second non-magnetic steel, the Vickers hardness of the second non-magnetic steel is 350-450, and the magnetic permeability of the second non-magnetic steel is ≤1.8.

[0021] According to the mold assembly of the present invention, preferably, the thickness of the transition layer is 0.05 to 0.5 mm, and the transition layer contains Ni, Cr, Al and Y;

[0022] The thickness of the wear-resistant layer is 10-20 μm, and the wear-resistant layer contains tungsten carbide, Co and Cr.

[0023] According to the mold assembly of the present invention, preferably, the first portion of the first main body side surface has an inner concave portion and an outer convex portion, and the inner concave portion of the first portion of the first main body side surface is close to the first mold cavity;

[0024] The second portion of the first main body side surface has an inner concave portion and an outer convex portion, and the outer convex portion of the second portion of the first main body side surface is close to the first mold cavity;

[0025] The first portion of the second main body side surface has an inner concave portion and an outer convex portion, and the outer convex portion of the first portion of the second main body side surface is adjacent to the second mold cavity; the inner concave portion of the first portion of the second main body side surface matches the outer convex portion of the first portion of the first main body side surface, and the outer convex portion of the first portion of the second main body side surface matches the inner concave portion of the first portion of the first main body side surface;

[0026] The second part of the second main body side has an inner recess and an outer protrusion, the inner recess of the second part of the second main body side is close to the second mold cavity, the inner recess of the second part of the second main body side matches the outer protrusion of the second part of the first main body side, and the outer protrusion of the second part of the second main body side matches the inner recess of the second part of the first main body side.

[0027] According to the mold assembly of the present invention, preferably, a positioning hole is opened on the top surface of the first body, and a positioning hole is opened on the top surface of the second body;

[0028] A positioning pin is provided at a position in the upper clamping sleeve slot that matches the positioning hole.

[0029] According to the mold assembly of the present invention, preferably, the portion of the first main body curved surface located in the upper ferrule slot smoothly transitions from the top to the bottom of the main body and bulges outward; the angle between L1 and L2 is 0.5-5°;

[0030] Wherein, L1 is a straight line passing through the intersection of the first main body curved surface and the top surface of the first main body and perpendicular to the top surface of the first main body; L2 is a straight line passing through the intersection of the first main body curved surface and the bottom surface of the upper ferrule and tangent to the first main body curved surface; L1 and L2 are located in the same plane;

[0031] The portion of the first main body curved surface located in the lower ferrule slot smoothly transitions from the bottom of the main body to the top and bulges outward; the angle between L3 and L4 is 0.5-5°;

[0032] Wherein, L3 is a straight line passing through the intersection of the first main body curved surface and the first main body bottom surface and perpendicular to the first main body bottom surface; L4 is a straight line passing through the intersection of the first main body curved surface and the top surface of the lower ferrule and tangent to the first main body curved surface; L3 and L4 are located in the same plane;

[0033] The portion of the second main body curved surface located in the upper ferrule slot smoothly transitions from the top to the bottom of the main body and bulges outward; the angle between L5 and L6 is 0.5-5°;

[0034] Wherein, L5 is a straight line passing through the intersection of the second main body curved surface and the second main body top surface and perpendicular to the second main body top surface; L6 is a straight line passing through the intersection of the second main body curved surface and the bottom surface of the upper ferrule and tangent to the second main body curved surface; L5 and L6 are located in the same plane;

[0035] The portion of the second main body curved surface located in the lower ferrule slot smoothly transitions from the bottom to the top of the main body and bulges outward; the angle between L7 and L8 is 0.5-5°;

[0036] Among them, L7 is a straight line passing through the intersection of the second main body curved surface and the second main body bottom surface, and perpendicular to the second main body bottom surface; L8 is a straight line passing through the intersection of the second main body curved surface and the top surface of the lower ferrule, and tangent to the second main body curved surface; L7 and L8 are located in the same plane.

[0037] According to the mold assembly of the present invention, preferably, the roughness of the first main curved surface located in the upper ferrule slot is Ra≤0.8μm; the roughness of the first main curved surface located in the lower ferrule slot is Ra≤0.8μm; the roughness of the second main curved surface located in the upper ferrule slot is Ra≤0.8μm; the roughness of the second main curved surface located in the lower ferrule slot is Ra≤0.8μm.

[0038] In another aspect, the present invention provides a method for preparing the above-mentioned mold assembly, comprising the following steps:

[0039] (1) subjecting the first non-magnetic steel alloy to ultrasonic testing to select non-magnetic steel that complies with GB / T 4162-2008 Grade A;

[0040] The non-magnetic steel meeting the requirements is vacuum quenched at 800-920°C for 0.5-3h, and then cryogenically treated at -230--180°C for 0.5-3h; the cryogenically treated non-magnetic steel is tempered at 170-230°C for 1-6h to obtain a first non-magnetic steel;

[0041] Solution treating the second non-magnetic steel alloy at 900-1300° C. for 10-50 minutes, and then water-cooling to obtain the second non-magnetic steel;

[0042] (2) machining the first non-magnetic steel and the second non-magnetic steel to obtain a first body, a second body, an upper ferrule, a lower ferrule, a pressing head, and a movable pad;

[0043] (3) spraying a transition layer on the surface of the first portion of the first main body side surface, the second portion of the first main body side surface, the first portion of the second main body side surface, and the second portion of the second main body side surface;

[0044] A wear-resistant layer is plated on the surface of the first mold cavity, the surface of the second mold cavity, the surface of the movable pad, and the surface of the portion of the pressure head extending into the mold cavity consisting of the first mold cavity and the second mold cavity.

[0045] In another aspect, the present invention provides a method for orientation pressing using the above mold assembly, comprising the following steps:

[0046] (A) assembling the first body, the second body, and the lower clamping sleeve, and forming a mold cavity with the first mold cavity and the second mold cavity;

[0047] (B) placing one of the movable spacers in the mold cavity, and allowing the movable spacer to sink to the bottom of the mold cavity under the action of gravity; adding magnetic powder to the mold cavity, and then adding another movable spacer;

[0048] (C) assembling the upper card sleeve on top of the first body and the second body;

[0049] (D) Inserting the main body of the punch into the mold cavity; in the presence of a magnetic field, applying pressure to the force-bearing portion of the punch to orient and compact the magnetic powder to obtain a green body.

[0050] The mold assembly of the present invention has strong high-pressure bearing capacity and weak magnetic shielding effect. Furthermore, the mold assembly of the present invention is easy to demould. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The figure is an exploded view of a mold assembly for oriented pressing of magnetic materials according to the present invention.

[0052] Figure 2 This is a schematic diagram of the structure after the first body and the second body are assembled.

[0053] Figure 3 This is a schematic diagram of the structure of the mold assembly after assembly of Example 1.

[0054] Figure 4 for Figure 3 A partial enlarged view of part A is shown.

[0055] The reference numerals are as follows:

[0056] 111-first main body curved surface; 1121-first mold cavity; 1122-first part of the first main body side surface; 1123-second part of the first main body side surface; 113-first main body top surface; 1131-positioning hole; 114-first main body bottom surface; 121-second main body curved surface; 1221-second mold cavity; 1222-first part of the second main body side surface; 1223-second part of the second main body side surface; 123-second main body top surface; 124-second main body bottom surface; 2-lower ferrule; 201-lower ferrule slot; 3-upper ferrule; 301-positioning pin; 302-mold cavity connecting hole; 4-pressing head; 401-main body; 402-force-bearing part; 5-movable pad. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0058] <Mold components>

[0059] The mold assembly of the present invention includes a main body, a lower ferrule, an upper ferrule, and a pressing head. In some embodiments, it also includes a movable spacer. Each component is described in detail below.

[0060] main body

[0061] The main body of the present invention can be cylindrical as a whole. The main body of the present invention has a split structure, comprising a first main body and a second main body. The first main body is semi-cylindrical. The second main body is semi-cylindrical. The first and second main bodies are substantially coaxial. After assembly, the coaxiality between the first and second bodies is ≤φ0.015mm.

[0062] The first body is formed by a first body curved surface, a first body side surface, a first body top surface and a first body bottom surface. The first body top surface and the first body bottom surface are substantially parallel.

[0063] A first mold cavity is provided in the middle of the side surface of the first main body. The first mold cavity runs through the length direction of the side surface of the first main body. The first mold cavity can be a rectangular parallelepiped. The surface of the first mold cavity has a wear-resistant layer. The thickness of the wear-resistant layer can be 10 to 20 μm; preferably 13 to 17 μm. The wear-resistant layer can contain tungsten carbide (WC), Co and Cr. The content of tungsten carbide can be 78 to 93 wt%; preferably 83 to 90 wt%. The content of Co can be 5 to 13 wt%; preferably 8 to 12 wt%. The content of Cr can be 2 to 6 wt%; preferably 3 to 5 wt%. The microhardness of the first mold cavity is ≥1800 HV, and the friction coefficient is ≤0.15.

[0064] The first mold cavity separates the first main body side surface into a first portion of the first main body side surface and a second portion of the first main body side surface. The surface of the first portion of the first main body side surface has a transition layer. The surface of the second portion of the first main body side surface has a transition layer. The thickness of the transition layer can be 0.05 to 0.5 mm, preferably 0.1 to 0.3 mm. The transition layer can contain Ni, Cr, Al, and Y. The Ni content can be 60 to 70 wt%, preferably 65 to 68 wt%. The Cr content can be 8 to 25 wt%, preferably 20 to 22 wt%. The Al content can be 8 to 12 wt%, preferably 9 to 11 wt%. The Y content can be 0.3 to 1.5 wt%, preferably 0.9 to 1.3 wt%. This can prevent the propagation of microcracks caused by stress concentration.

[0065] The first part of the first main body side surface has an inner concave portion and an outer convex portion. The inner concave portion of the first part of the first main body side surface is arranged close to the first mold cavity. The projection of the first part of the first main body side surface on the horizontal plane is This can increase assembly accuracy.

[0066] The second part of the first main body side surface has an inner concave portion and an outer convex portion. The outer convex portion of the second part of the first main body side surface is arranged close to the first mold cavity. The projection of the second part of the first main body side surface on the horizontal plane is This can increase assembly accuracy.

[0067] The intersection of the first main body curved surface and the first main body top surface is a transition fillet. The diameter of the transition fillet can be 0.1 to 0.8 mm, preferably 0.3 to 0.6 mm. This can reduce stress concentration.

[0068] The intersection of the first main body curved surface and the first main body bottom surface is a transition fillet. The diameter of the transition fillet can be 0.1 to 0.8 mm, preferably 0.3 to 0.6 mm. This can reduce stress concentration.

[0069] Positioning holes may be provided on the top surface of the first body to facilitate accurate assembly.

[0070] The part of the first main body curved surface located in the upper ferrule slot smoothly transitions from the top of the main body to the bottom and bulges outward. The angle between L1 and L2 is 0.5-5°; preferably 1.5-2.8°. L1 is a straight line passing through the intersection of the first main body curved surface and the top surface of the first main body, and perpendicular to the top surface of the first main body. L2 is a straight line passing through the intersection of the first main body curved surface and the bottom surface of the upper ferrule, and tangent to the first main body curved surface. L1 and L2 are in the same plane. The projection of the part of the first main body curved surface located in the upper ferrule slot on the vertical plane is a minor arc. The roughness of the first main body curved surface located in the upper ferrule slot is Ra≤0.8μm; preferably, Ra≤0.2μm. This facilitates demolding.

[0071] The part of the first main body curved surface located in the lower ferrule slot smoothly transitions from the bottom of the main body to the top and bulges outward. The angle between L3 and L4 is 0.5-5°; preferably 1.5-2.8°. L3 is a straight line passing through the intersection of the first main body curved surface and the bottom surface of the first main body, and perpendicular to the bottom surface of the first main body. L4 is a straight line passing through the intersection of the first main body curved surface and the top surface of the lower ferrule, and tangent to the first main body curved surface. L3 and L4 are in the same plane. The projection of the part of the first main body curved surface located in the lower ferrule slot on the vertical plane is a minor arc. The roughness of the first main body curved surface located in the lower ferrule slot is Ra≤0.8μm; preferably, Ra≤0.2μm. This facilitates demolding.

[0072] The first body is formed from a first non-magnetic steel. Ultrasonic flaw detection of the first non-magnetic steel complies with GB / T4162-2008 Class A. The Rockwell hardness of the first non-magnetic steel may be 53 to 67, preferably 58 to 62. The magnetic permeability of the first non-magnetic steel may be ≤ 1.8, preferably ≤ 1.04. The first non-magnetic steel may include carbon, manganese, and iron. The carbon content may be 0.65 to 0.75 wt%. The manganese content may be 1.2 to 1.5 wt%.

[0073] The second body is formed by a second body curved surface, a second body side surface, a second body top surface and a second body bottom surface, and the second body top surface and the second body bottom surface are substantially parallel.

[0074] A second mold cavity is provided in the middle of the side surface of the second main body. The second mold cavity runs through the length direction of the side surface of the second main body. The second mold cavity can be a rectangular parallelepiped. The surface of the second mold cavity has a wear-resistant layer. The thickness of the wear-resistant layer can be 10 to 20 μm; preferably 13 to 17 μm. The wear-resistant layer can contain tungsten carbide (WC), Co and Cr. The content of tungsten carbide can be 78 to 93 wt%; preferably 83 to 90 wt%. The content of Co can be 5 to 13 wt%; preferably 8 to 12 wt%. The content of Cr can be 2 to 6 wt%; preferably 3 to 5 wt%. The microhardness of the second mold cavity is ≥1800 HV, and the friction coefficient is ≤0.15.

[0075] The second mold cavity separates the second main body side surface into a first portion of the second main body side surface and a second portion of the second main body side surface. The surface of the first portion of the second main body side surface has a transition layer. The surface of the second portion of the second main body side surface has a transition layer. The thickness of the transition layer can be 0.05 to 0.5 mm, preferably 0.1 to 0.3 mm. The transition layer can contain Ni, Cr, Al, and Y. The Ni content can be 60 to 70 wt%, preferably 65 to 68 wt%. The Cr content can be 8 to 25 wt%, preferably 20 to 22 wt%. The Al content can be 8 to 12 wt%, preferably 9 to 11 wt%. The Y content can be 0.3 to 1.5 wt%, preferably 0.9 to 1.3 wt%. This can prevent the propagation of microcracks caused by stress concentration.

[0076] The first part of the second main body side surface has an inner concave portion and an outer convex portion. The outer convex portion of the first part of the second main body side surface is arranged close to the second mold cavity. The projection of the first part of the second main body side surface on the horizontal plane is The outer protrusion of the first part of the second body side surface matches the inner concave portion of the first part of the first body side surface. The inner concave portion of the first part of the second body side surface matches the outer protrusion of the first part of the first body side surface. This can increase assembly accuracy.

[0077] The second part of the second main body side surface has an inner concave portion and an outer convex portion. The inner concave portion of the second part of the second main body side surface is arranged close to the second mold cavity. The projection of the second part of the second main body side surface on the horizontal plane is The inner concave portion of the second portion of the second body side surface matches the outer convex portion of the second portion of the first body side surface. The outer convex portion of the second portion of the second body side surface matches the inner concave portion of the second portion of the first body side surface. This can increase assembly accuracy.

[0078] The intersection of the second main body curved surface and the second main body top surface is a transition fillet. The diameter of the transition fillet can be 0.1 to 0.8 mm, preferably 0.3 to 0.6 mm. This can reduce stress concentration.

[0079] The intersection of the second main body curved surface and the second main body bottom surface is a transition fillet. The diameter of the transition fillet can be 0.1 to 0.8 mm, preferably 0.3 to 0.6 mm. This can reduce stress concentration.

[0080] Positioning holes may be provided on the top surface of the second body to facilitate accurate assembly.

[0081] The part of the second main body curved surface located in the upper ferrule slot smoothly transitions from the top of the main body to the bottom and bulges outward. The angle between L5 and L6 is 0.5-5°; preferably 1.5-2.8°. L5 is a straight line passing through the intersection of the second main body curved surface and the top surface of the second main body, and perpendicular to the top surface of the second main body. L6 is a straight line passing through the intersection of the second main body curved surface and the bottom surface of the upper ferrule, and tangent to the second main body curved surface. L5 and L6 are in the same plane. The projection of the part of the second main body curved surface located in the upper ferrule slot on the vertical plane is a minor arc. The roughness of the second main body curved surface located in the upper ferrule slot is Ra≤0.8μm; preferably, Ra≤0.2μm. This facilitates demolding.

[0082] The part of the second main body curved surface located in the lower ferrule slot smoothly transitions from the bottom of the main body to the top and bulges outward. The angle between L7 and L8 is 0.5-5°; preferably 1.5-2.8°. L7 is a straight line passing through the intersection of the second main body curved surface and the second main body bottom surface, and perpendicular to the second main body bottom surface. L8 is a straight line passing through the intersection of the second main body curved surface and the top surface of the lower ferrule, and tangent to the second main body curved surface. L7 and L8 are located in the same plane. The projection of the part of the second main body curved surface located in the lower ferrule slot on the vertical plane is a minor arc. The roughness of the second main body curved surface located in the lower ferrule slot is Ra≤0.8μm; preferably, Ra≤0.2μm. This facilitates demolding.

[0083] The second body is formed from a first non-magnetic steel. Ultrasonic flaw detection of the first non-magnetic steel complies with GB / T4162-2008 Class A. The Rockwell hardness of the first non-magnetic steel may be 53 to 67, preferably 58 to 62. The magnetic permeability of the first non-magnetic steel may be ≤1.8, preferably ≤1.04. The first non-magnetic steel may include C, Mn, Si, S, P, Cr, Ni, Cu, and Fe. Preferably, the first non-magnetic steel is composed of the aforementioned elements. The C content may be 0.65 to 0.75 wt%. The Mn content may be 1.2 to 1.5 wt%. The Si content may be 0.20 to 0.30 wt%. The S content may be 0.005 to 0.02 wt%. The P content may be 0.005 to 0.02 wt%. The Cr content may be 0.15 to 0.3 wt%. The Ni content may be 0.1 to 0.2 wt%. The Cu content may be 0.2 to 0.3 wt%. This can ensure good high-voltage bearing capacity and reduce the magnetic shielding effect.

[0084] After the first and second bodies are assembled, the first and second mold cavities form a mold cavity. The corners within the mold cavity are rounded. The radius R of the rounded corners can be 0.2 to 0.8 mm, preferably 0.4 to 0.6 mm. This facilitates demolding.

[0085] Lower card sleeve

[0086] The lower ferrule of the present invention is provided with a lower ferrule slot. The lower ferrule slot is configured to accommodate the bottom of the main body. The lower ferrule can be a rectangular parallelepiped. The lower ferrule is configured to fix the first and second main bodies from the bottom.

[0087] The lower ferrule is formed of a second non-magnetic steel. The Vickers hardness of the second non-magnetic steel can be 350-450; preferably 380-420. The magnetic permeability of the second non-magnetic steel is ≤1.8; preferably, the magnetic permeability is ≤1.02. The second non-magnetic steel contains Cr, Ni, C, Mn, Si, P, S and Fe. The Cr content can be 18-20wt%. The Ni content can be 8-10.5wt%. The C content can be 0.01-0.03wt%. The Mn content can be 0.05-0.20wt%. The Si content can be 0.2-0.4wt%. The P content can be 0.005-0.02wt%. The S content can be 0.005-0.02wt%. This can ensure good high-voltage bearing capacity and reduce the magnetic shielding effect.

[0088] Upper card sleeve

[0089] The upper ferrule of the present invention is provided with an upper ferrule slot. The upper ferrule slot is configured to accommodate the top of the main body. The upper ferrule can be a rectangular parallelepiped. The upper ferrule is configured to fix the first and second main bodies from the top.

[0090] A locating pin is provided in the upper ferrule slot at a position matching the locating hole. The shape of the locating pin matches the shape of the locating hole. The locating pin can be diamond-shaped.

[0091] The upper clamping sleeve is provided with a mold cavity communicating hole. When the upper clamping sleeve is sleeved on the top of the main body, the mold cavity communicating hole is communicated with the mold cavity.

[0092] The upper ferrule is formed of a second non-magnetic steel. The Vickers hardness of the second non-magnetic steel can be 350-450; preferably 380-420. The magnetic permeability of the second non-magnetic steel is ≤1.8; preferably, the magnetic permeability is ≤1.02. The second non-magnetic steel contains Cr, Ni, C, Mn, Si, P, S and Fe. The Cr content can be 18-20wt%. The Ni content can be 8-10.5wt%. The C content can be 0.01-0.03wt%. The Mn content can be 0.05-0.20wt%. The Si content can be 0.2-0.4wt%. The P content can be 0.005-0.02wt%. The S content can be 0.005-0.02wt%. This can ensure good high-voltage bearing capacity and reduce the magnetic shielding effect.

[0093] Indenter

[0094] The ram of the present invention includes a main body and a force-bearing portion. The top of the main body is connected to the bottom of the force-bearing portion. The main body is capable of extending into a mold cavity formed by a first mold cavity and a second mold cavity. The ram can be T-shaped. The surface of the portion of the main body extending into the mold cavity has a wear-resistant layer.

[0095] The indenter is formed from a first non-magnetic steel. Ultrasonic flaw detection of the first non-magnetic steel complies with GB / T 4162-2008 Class A. The Rockwell hardness of the first non-magnetic steel may be 53 to 67, preferably 58 to 62. The magnetic permeability of the first non-magnetic steel may be ≤ 1.8, preferably ≤ 1.04. The first non-magnetic steel may include C, Mn, Si, S, P, Cr, Ni, Cu, and Fe. Preferably, the first non-magnetic steel is composed of the aforementioned elements. The C content may be 0.65 to 0.75 wt%. The Mn content may be 1.2 to 1.5 wt%. The Si content may be 0.20 to 0.30 wt%. The S content may be 0.005 to 0.02 wt%. The P content may be 0.005 to 0.02 wt%. The Cr content may be 0.15 to 0.3 wt%. The Ni content may be 0.1 to 0.2 wt%. The Cu content may be 0.2 to 0.3 wt%. This can ensure good high-voltage bearing capacity and reduce the magnetic shielding effect.

[0096] The wear-resistant layer can have a thickness of 10 to 20 μm, preferably 13 to 17 μm. The wear-resistant layer can contain tungsten carbide (WC), cobalt, and chromium. The tungsten carbide content can be 78 to 93 wt%, preferably 83 to 90 wt%. The cobalt content can be 5 to 13 wt%, preferably 8 to 12 wt%. The chromium content can be 2 to 6 wt%, preferably 3 to 5 wt%. The body with the wear-resistant layer has a microhardness of ≥1800 HV and a friction coefficient of ≤0.15.

[0097] Moving pads

[0098] The movable pad of the present invention matches the shape of the mold cavity. The surface of the movable pad has a wear-resistant layer. In this embodiment, the movable pad is a rectangular parallelepiped.

[0099] The movable pad is formed of a first non-magnetic steel. The ultrasonic flaw detection of the first non-magnetic steel complies with GB / T4162-2008 Class A. The Rockwell hardness of the first non-magnetic steel can be 53 to 67, preferably 58 to 62. The magnetic permeability of the first non-magnetic steel is ≤1.8, preferably ≤1.04. The first non-magnetic steel may include C, Mn, Si, S, P, Cr, Ni, Cu, and Fe. Preferably, the first non-magnetic steel is composed of the aforementioned elements. The C content can be 0.65 to 0.75 wt%. The Mn content can be 1.2 to 1.5 wt%. The Si content can be 0.20 to 0.30 wt%. The S content can be 0.005 to 0.02 wt%. The P content can be 0.005 to 0.02 wt%. The Cr content can be 0.15 to 0.3 wt%. The Ni content can be 0.1 to 0.2 wt%. The Cu content can be 0.2 to 0.3 wt%. This can ensure good high-voltage bearing capacity and reduce the magnetic shielding effect.

[0100] The wear-resistant layer can have a thickness of 10 to 20 μm, preferably 13 to 17 μm. The wear-resistant layer can contain tungsten carbide (WC), cobalt, and chromium. The tungsten carbide content can be 78 to 93 wt%, preferably 83 to 90 wt%. The cobalt content can be 5 to 13 wt%, preferably 8 to 12 wt%. The chromium content can be 2 to 6 wt%, preferably 3 to 5 wt%. The microhardness of the movable pad is ≥ 1800 HV, and the friction coefficient is ≤ 0.15.

[0101] When the movable pad is placed in the mold cavity formed by the first mold cavity and the second mold cavity, the gap between the movable pad and the inner wall of the mold cavity is 0.1 to 0.15 mm.

[0102] The number of movable spacers can be two.

[0103] <Method for Preparing Mold Assembly>

[0104] The method for preparing the mold assembly of the present invention comprises the following steps: (1) a step of pre-treating raw materials; (2) a step of mechanical processing; and (3) a step of forming a film layer.

[0105] Raw material pretreatment steps

[0106] The present invention subjects a non-magnetic steel alloy to ultrasonic testing to select non-magnetic steel that meets GB / T 4162-2008 Grade A. The non-magnetic steel that meets the requirements is quenched and then cryogenically treated. The cryogenically treated non-magnetic steel is then tempered to obtain a first non-magnetic steel. A second non-magnetic steel is then solution treated and then water-cooled to obtain a second non-magnetic steel.

[0107] The quenching temperature may be 800-920°C, preferably 840-860°C. The quenching time may be 0.5-3 hours, preferably 1.5-2.5 hours. The quenching may be performed under vacuum conditions, where vacuum means a pressure of ≤5 Pa.

[0108] The cryogenic treatment temperature may be -230 to -180° C., preferably -200 to -190° C. The cryogenic treatment time may be 0.5 to 3 hours, preferably 1 to 1.5 hours.

[0109] The tempering temperature may be 170 to 230° C., preferably 190 to 210° C. The tempering time may be 1 to 6 hours, preferably 3 to 5 hours.

[0110] The solution treatment temperature may be 900 to 1300° C., preferably 1000 to 1100° C. The solution treatment time may be 10 to 50 minutes, more preferably 20 to 40 minutes.

[0111] Machining steps

[0112] The present invention mechanically processes the first non-magnetic steel and the second non-magnetic steel to obtain the first body, the second body, the upper clamping sleeve, the lower clamping sleeve, the pressure head and the movable pad.

[0113] The curved surface can be processed by a five-axis machining center.

[0114] Steps for forming the film

[0115] The present invention sprays a transition layer on the surface of the first part of the first main body side, the second part of the first main body side, the first part of the second main body side, and the second part of the second main body side; and plates a wear-resistant layer on the surface of the first mold cavity, the surface of the second mold cavity, the surface of the movable pad, and the surface of the part of the pressure head extending into the mold cavity formed by the first mold cavity and the second mold cavity.

[0116] The wear-resistant layer can be deposited using unbalanced magnetron sputtering technology.

[0117] <Orientation Pressing Method>

[0118] The method of the present invention for orientation pressing using the above-mentioned mold assembly includes the following steps: (A) assembling the first main body, the second main body and the lower clamping sleeve, and the first mold cavity and the second mold cavity form a mold cavity; (B) placing one of the movable pads in the mold cavity, and the movable pad sinks to the bottom of the mold cavity under the action of gravity; adding magnetic powder to the mold cavity, and then adding another movable pad; (C) assembling the upper clamping sleeve on the top of the first main body and the second main body; (D) extending the main body of the pressing head into the mold cavity; in the presence of a magnetic field, the pressure applied to the force-bearing part of the pressing head is used to orientation-press the magnetic powder to obtain a blank.

[0119] The magnetic powder can be neodymium iron boron magnetic powder or magnetostrictive composite powder.

[0120] Neodymium iron boron magnetic powder contains Nd, Fe, B, Dy, Al, and Cu. The Nd content can be 29 to 32.5 wt%, preferably 30 to 32 wt%. The Fe content can be 50 to 70 wt%, preferably 60 to 67 wt%. The B content can be 0.9 to 1.5 wt%, preferably 1 to 1.2 wt%. The Dy content can be 0.5 to 1.5 wt%, preferably 0.7 to 1.2 wt%. The Al content can be 0.1 to 0.8 wt%, preferably 0.2 to 0.6 wt%. The Cu content can be 0.05 to 0.3 wt%, preferably 0.1 to 0.2 wt%. The neodymium iron boron magnetic powder may also contain other impurities. The content of other impurities is ≤ 2.0 wt%, preferably ≤ 1.5 wt%.

[0121] The magnetostrictive composite powder contains TbDyFe alloy powder and epoxy resin. The volume ratio of the TbDyFe alloy powder to the epoxy resin can be 2:(1-5), preferably 2:(2-4).

[0122] The epoxy resin may be a bisphenol A type solid epoxy resin.

[0123] In the TbDyFe alloy powder, the content of Tb may be 0.1 to 0.6 atomic fractions, and preferably 0.2 to 0.4 atomic fractions.

[0124] In the TbDyFe alloy powder, the content of Dy may be 0.4 to 0.9 atomic fractions, and preferably 0.6 to 0.8 atomic fractions.

[0125] In the TbDyFe alloy powder, the Fe content may be 1 to 3 atomic parts, and preferably 1.5 to 2.5 atomic parts.

[0126] In step (C), a three-coordinate measuring machine can be used to detect the assembly coaxiality.

[0127] The magnetic field strength can be 0.1 T to 1.5 T, preferably 0.8 to 1 T. The magnetic field is a uniform magnetic field and can be provided by an electromagnet.

[0128] The pressure applied to the force-bearing portion may be 20 to 250 MPa. In some embodiments, the pressure is 30 to 50 MPa. In other embodiments, the pressure is 190 to 210 MPa. The elemental composition of the alloy is described below:

[0129] The first non-magnetic steel has a composition of: C 0.71wt%, Mn 1.40wt%, Si 0.24wt%, S 0.01wt%, P 0.01wt%, Cr 0.21wt%, Ni 0.15wt%, Cu 0.24wt%, and the balance Fe. Ultrasonic testing confirms it complies with GB / T4162-2008 Grade A. Its Rockwell hardness (HRC) is 58-62, and its magnetic permeability μ≤1.04.

[0130] The second non-magnetic steel has a composition of Cr 18.71wt%, Ni 9.88wt%, C 0.02wt%, Mn 0.10wt%, Si0.31wt%, P 0.01wt%, S 0.01wt%, and the remainder is Fe. The Vickers hardness (HV) is 403, and the magnetic permeability μ≤1.02.

[0131] The composition of the wear-resistant layer is: 86 wt% WC (tungsten carbide), 10 wt% Co and 4 wt% Cr.

[0132] The composition of the transition layer is: 67.22wt% Ni, 20.86wt% Cr, 10.71wt% Al and 1.21wt% Y.

[0133] Example 1

[0134] like Figure 1 As shown, the mold assembly for orientation pressing of magnetic materials in this embodiment includes a main body, a lower clamping sleeve 2, an upper clamping sleeve 3, a pressing head 4 and a movable pad 5.

[0135] The main body is a cylinder and is divided into a first main body and a second main body along a plane passing through the central axis of the main body.

[0136] The first body is formed by a first body curved surface 111, a first body side surface, a first body top surface 113 and a first body bottom surface 114. The first body top surface 113 and the first body bottom surface 114 are substantially parallel.

[0137] A first mold cavity 1121 is defined in the middle of the first main body side surface. The first mold cavity 1121 extends through the length of the first main body side surface. The first mold cavity 1121 is a rectangular parallelepiped. The first mold cavity 1121 divides the first main body side surface into a first portion 1122 of the first main body side surface and a second portion 1123 of the first main body side surface.

[0138] The first part 1122 of the first main body side surface has an inner concave portion and an outer convex portion. The inner concave portion of the first part 1122 of the first main body side surface is close to the first mold cavity 1121. The projection of the first part 1122 of the first main body side surface on the horizontal plane is shape.

[0139] The second part 1123 of the first main body side has an inner concave part and an outer convex part. The outer convex part of the second part 1123 of the first main body side is close to the first membrane cavity 1121. The projection of the second part 1123 of the first main body side on the horizontal plane is shape.

[0140] The intersection of the first main body curved surface 111 and the first main body top surface 113, as well as the intersection of the first main body curved surface 111 and the first main body bottom surface 114 are both transition fillets. The diameter of the transition fillets is 0.5 mm.

[0141] like Figure 1 and Figure 2 As shown, a positioning hole 1131 is defined on the top surface 113 of the first body. The first body is formed of a first non-magnetic steel. The surface of the first mold cavity 1121 has a wear-resistant layer with a thickness of 15±2 μm. The microhardness of the first mold cavity 1121 is ≥1800 HV, and the coefficient of friction is ≤0.15. The surfaces of the first portion 1122 of the first body side surface and the second portion 1123 of the first body side surface have a transition layer with a thickness of 0.2 mm.

[0142] like Figure 1 As shown, the second body is formed by a second body curved surface 121, a second body side surface, a second body top surface 123 and a second body bottom surface 124. The second body top surface 123 and the second body bottom surface 124 are substantially parallel.

[0143] A second mold cavity 1221 is defined in the middle of the second main body side surface. The second mold cavity 1221 extends through the length of the second main body side surface. The second mold cavity 1221 is a rectangular parallelepiped. The second mold cavity 1221 divides the second main body side surface into a first second main body side surface portion 1222 and a second second main body side surface portion 1223.

[0144] like Figure 2 As shown, the first side portion 1222 of the second main body has an inner concave portion and an outer convex portion. The outer convex portion of the first side portion 1222 of the second main body is close to the second mold cavity 1221. The projection of the first side portion 1222 of the second main body on the horizontal plane is The inner concave portion of the first portion 1222 of the second body side surface matches the outer convex portion of the first portion 1122 of the first body side surface. The outer convex portion of the first portion 1222 of the second body side surface matches the inner concave portion of the first portion 1122 of the first body side surface.

[0145] The second portion 1223 of the second main body side has an inner concave portion and an outer convex portion. The inner concave portion of the second portion 1223 of the second main body side is close to the second membrane cavity 1221. The projection of the second portion 1223 of the second main body side on the horizontal plane is The inner concave portion of the second portion 1223 of the second main body side surface matches the outer convex portion of the second portion 1123 of the first main body side surface. The outer convex portion of the second portion 1223 of the second main body side surface matches the inner concave portion of the second portion 1123 of the first main body side surface.

[0146] The intersection of the second main body curved surface 121 and the second main body top surface 123, as well as the intersection of the second main body curved surface 121 and the second main body bottom surface 124, are both transition fillets with a diameter of 0.5 mm.

[0147] like Figure 1 and 2 As shown, a positioning hole 1131 is defined on the top surface 123 of the second body. The second body is formed from a first non-magnetic steel. The surface of the second mold cavity 1221 has a wear-resistant layer with a thickness of 15±2 μm. The microhardness of the second mold cavity 1221 is ≥1800 HV, and the coefficient of friction is ≤0.15. The surfaces of the first side portion 1222 of the second body and the second side portion 1223 of the second body have a transition layer with a thickness of 0.2 mm.

[0148] like Figure 3 As shown, after the first and second bodies are assembled, their coaxiality is ≤φ0.015mm. The first mold cavity 1121 and the second mold cavity 1221 form a mold cavity. The edges and corners in the mold cavity are rounded. The diameter R of the rounded corners is 0.5mm.

[0149] like Figure 1 As shown, the lower ferrule 2 is a rectangular parallelepiped. The lower ferrule 2 is provided with a lower ferrule slot 201. The lower ferrule slot 201 is configured to accommodate the bottom of the main body. The lower ferrule 2 is formed from a second non-magnetic steel. The lower ferrule 2 is used to fix the first and second main bodies from the bottom.

[0150] The upper clamping sleeve 3 is a rectangular parallelepiped. The upper clamping sleeve 3 is provided with an upper clamping sleeve slot. The upper clamping sleeve slot is set to accommodate the top of the main body. Figure 3 As shown, a diamond-shaped positioning pin 301 is provided in the upper ferrule slot at a position matching the positioning hole 1131. The upper ferrule 3 is provided with a mold cavity communication hole 302. When the upper ferrule 3 is mounted on the top of the main body, the mold cavity communication hole 302 is connected to the mold cavity. The upper ferrule 3 is formed from a second non-magnetic steel. The upper ferrule 3 is used to fix the first and second bodies from the top.

[0151] like Figure 3 and Figure 4As shown, the part of the first main body curved surface 111 located in the upper ferrule slot smoothly transitions from the top of the main body to the bottom and bulges outward, and its projection on the vertical plane is a minor arc. The angle between L1 and L2 is 2±0.2°. L1 is a straight line passing through the intersection of the first main body curved surface 111 and the first main body top surface 113, and perpendicular to the first main body top surface 113. L2 is a straight line passing through the intersection of the first main body curved surface 111 and the bottom surface of the upper ferrule 3, and tangent to the first main body curved surface 111. L1 and L2 are in the same plane. The roughness of the first main body curved surface 111 located in the upper ferrule slot is Ra≤0.2μm.

[0152] The first main body curved surface 111 located in the lower ferrule slot 201 transitions smoothly from the bottom of the main body to the top and bulges outward, and its projection on the vertical plane is a minor arc. The angle between L3 and L4 is 2±0.2°. L3 is a straight line passing through the intersection of the first main body curved surface 111 and the first main body bottom surface 114, and perpendicular to the first main body bottom surface 114. L4 is a straight line passing through the intersection of the first main body curved surface 111 and the top surface of the lower ferrule 2, and tangent to the first main body curved surface 111. L3 and L4 are in the same plane. The roughness Ra of the first main body curved surface 111 located in the lower ferrule slot 201 is ≤0.2μm.

[0153] The portion of the first main body curved surface 111 located between the upper ferrule 3 and the lower ferrule 2 is substantially perpendicular to the first main body bottom surface 114 .

[0154] The part of the second main body curved surface 121 located in the upper ferrule slot smoothly transitions from the top of the main body to the bottom and bulges outward, and its projection on the vertical plane is a minor arc. The angle between L5 and L6 is 2±0.2°. L5 is a straight line passing through the intersection of the second main body curved surface 121 and the second main body top surface 123, and perpendicular to the second main body top surface 123. L6 is a straight line passing through the intersection of the second main body curved surface 121 and the bottom surface of the upper ferrule 3, and tangent to the second main body curved surface 121. L5 and L6 are in the same plane. The roughness of the second main body curved surface 121 located in the upper ferrule slot is Ra≤0.2μm.

[0155] The second main body curved surface 121 located in the lower ferrule slot 201 transitions smoothly from the bottom of the main body to the top and bulges outward, and its projection on the vertical plane is a minor arc. The angle between L7 and L8 is 2±0.2°. L7 is a straight line passing through the intersection of the second main body curved surface 121 and the second main body bottom surface 124, and perpendicular to the second main body bottom surface 124. L8 is a straight line passing through the intersection of the second main body curved surface 121 and the top surface of the lower ferrule 2, and tangent to the second main body curved surface 121. L7 and L8 are located in the same plane. The roughness Ra of the second main body curved surface 121 located in the lower ferrule slot 201 is ≤0.2μm.

[0156] The portion of the second main body curved surface 121 located between the upper ferrule 3 and the lower ferrule 2 is substantially perpendicular to the second main body bottom surface 124 .

[0157] like Figure 1 and 3 As shown, the pressing head 4 includes a main body 401 and a force-bearing part 402. The top of the main body 401 is connected to the bottom of the force-bearing part 402. The main body 401 can extend into the mold cavity to apply pressure to the magnetic powder in the mold cavity. The pressing head 4 is T-shaped. The pressing head 4 is formed by a first non-magnetic steel. The surface of the part of the main body 401 extending into the mold cavity has a wear-resistant layer with a thickness of 15±2μm. The microhardness of the main body 401 with the wear-resistant layer is ≥1800HV, and the friction coefficient is ≤0.15.

[0158] The movable pad 5 matches the shape of the mold cavity. In this embodiment, the movable pad 5 is a rectangular parallelepiped. The movable pad 5 is formed from a first non-magnetic steel. The surface of the movable pad 5 has a wear-resistant layer with a thickness of 15±2μm. When the movable pad 5 is placed in the mold cavity, the gap between it and the inner wall of the mold cavity is 0.1 to 0.15mm. Two movable pads 5 are provided.

[0159] Example 2

[0160] This embodiment provides a method for preparing the mold assembly for oriented pressing of magnetic materials according to embodiment 1, comprising the following steps:

[0161] (1) The first non-magnetic steel alloy is subjected to ultrasonic testing, and non-magnetic steel that meets GB / T 4162-2008 Grade A is selected. The non-magnetic steel that meets the requirements is vacuum quenched (pressure ≤ 5 Pa) at 850±10°C for 2 hours, and then cryogenically treated at -196°C for 1 hour. The cryogenically treated non-magnetic steel is tempered at 200±10°C for 4 hours to obtain the first non-magnetic steel.

[0162] The second non-magnetic steel alloy was solution treated at 1050° C. for 30 minutes and then water-cooled to obtain the second non-magnetic steel.

[0163] (2) The first non-magnetic steel and the second non-magnetic steel are machined to obtain a first body, a second body, an upper ferrule, a lower ferrule, a pressing head and a movable pad; wherein the curved surface is machined by a five-axis linkage machining center.

[0164] (3) A transition layer is sprayed on the surfaces of the first portion 1122 of the first main body side surface, the second portion 1123 of the first main body side surface, the first portion 1222 of the second main body side surface, and the second portion 1223 of the second main body side surface.

[0165] The wear-resistant layer is plated on the surfaces of the first mold cavity 1121 and the second mold cavity 1221 by using unbalanced magnetron sputtering technology.

[0166] The wear-resistant layer is plated on the surface of the movable pad 5 by adopting unbalanced magnetron sputtering technology.

[0167] The wear-resistant layer is plated on the surface of the portion of the pressing head 4 extending into the mold cavity by using unbalanced magnetron sputtering technology.

[0168] Example 3

[0169] This embodiment provides a method for oriented pressing of NdFeB magnetic powder using the mold assembly of embodiment 1:

[0170] The first body, the second body and the lower ferrule 2 are assembled, and the first mold cavity 1121 and the second mold cavity 1221 form a mold cavity.

[0171] One of the movable blocks 5 is placed in the mold cavity, where it sinks to the bottom under gravity. NdFeB magnetic powder is then added to the mold cavity, followed by the other movable block 5. An electromagnet is used to provide a uniform magnetic field with a magnetic field strength of 1.5 T. The chemical composition of the NdFeB magnetic powder is 32.0 wt% Nd, 64.1 wt% Fe, 1.1 wt% B, 0.9 wt% Dy, 0.4 wt% Al, 0.1 wt% Cu, and 1.4 wt% other impurities.

[0172] The upper ferrule 3 is assembled on the top of the first body and the second body. The coaxiality of the assembly is detected by a three-dimensional coordinate measuring machine.

[0173] The main body 401 of the pressing head 4 is inserted into the mold cavity. A pressure of 200 MPa is applied to the force-bearing portion 402 of the pressing head 4 to orient and compact the NdFeB magnetic powder to obtain a 50 mm×30 mm×30 mm rectangular NdFeB blank.

[0174] The demoulding force was measured to be 2.8 kN by direct testing with a tensile gauge.

[0175] The above experiment was repeated. After the mold assembly was used continuously for 15,000 times, the deformation of the inner diameter of the mold cavity was ≤0.003mm, and the wear-resistant layer in the mold cavity did not fall off.

[0176] Using an electromagnet to provide a uniform magnetic field strength of 1.5 T, a Tesla meter was used to measure the magnetic field strength inside the mold cavity and around the mold (at the same height as the test position inside the mold cavity, 5 mm from the outside of the mold side wall). The deviation in magnetic field strength inside and outside the mold cavity was less than 5%. The deviation in magnetic field strength inside and outside the mold cavity was calculated using the following formula:

[0177] P = [(H0 - H1) / H0] × 100%;

[0178] Where P represents the magnetic field strength deviation; H0 represents the magnetic field strength around the mold, in T; H1 represents the magnetic field strength in the mold cavity, in T.

[0179] Example 4

[0180] This embodiment provides a method for oriented pressing of magnetostrictive composite powder using the mold assembly of embodiment 1:

[0181] The first body, the second body and the lower ferrule 2 are assembled, and the first mold cavity 1121 and the second mold cavity 1221 form a mold cavity.

[0182] One of the movable pads 5 is placed in the mold cavity, and the movable pad 5 sinks to the bottom of the mold cavity under the action of gravity; magnetostrictive composite powder is added to the mold cavity, and then the other movable pad 5 is added. An electromagnet is used to provide a uniform magnetic field with a magnetic field strength of 0.8T. The composition of the magnetostrictive composite powder is Tb in a volume ratio of 2:3. 0.3 Dy 0.7 Fe2 alloy powder and bisphenol A solid epoxy resin.

[0183] The upper ferrule 3 is assembled on the top of the first body and the second body. The coaxiality of the assembly is detected by a three-dimensional coordinate measuring machine.

[0184] The main body 401 of the pressing head 4 is inserted into the mold cavity. A pressure of 40 MPa is applied to the force-bearing portion 402 of the pressing head 4 to orient and compact the magnetostrictive composite powder to obtain a 50 mm×30 mm×30 mm rectangular green body.

[0185] The demoulding force measured by a tensile tester was 1.5 kN.

[0186] The obtained green body has a smooth surface and complete edges.

[0187] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A mold assembly for oriented pressing of magnetic materials, characterized in that: Including main body, lower ferrule, upper ferrule and press head; The main body includes a first main body and a second main body; The first body is formed by a first body curved surface, a first body side surface, a first body top surface and a first body bottom surface; the first body top surface and the first body bottom surface are substantially parallel; A first mold cavity is formed in the middle of the first main body side surface, the first mold cavity runs through the length direction of the first main body side surface, and the surface of the first mold cavity has a wear-resistant layer; the first mold cavity divides the first main body side surface into a first portion of the first main body side surface and a second portion of the first main body side surface, and the surfaces of the first portion of the first main body side surface and the second portion of the first main body side surface have a transition layer; The second body is formed by a second body curved surface, a second body side surface, a second body top surface and a second body bottom surface; the second body top surface and the second body bottom surface are substantially parallel; A second mold cavity is formed in the middle of the second main body side surface, the second mold cavity runs through the length direction of the second main body side surface, and the surface of the second mold cavity has a wear-resistant layer; the second mold cavity divides the second main body side surface into a first portion of the second main body side surface and a second portion of the second main body side surface, and the surfaces of the first portion of the second main body side surface and the second portion of the second main body side surface have a transition layer; The lower ferrule is provided with a lower ferrule slot, and the lower ferrule slot is configured to accommodate the bottom of the main body; The upper ferrule is provided with an upper ferrule slot, and the upper ferrule slot is configured to accommodate the top of the main body; the upper ferrule is provided with a mold cavity communicating hole; The pressure head includes a main body and a force-bearing part; the top of the main body is connected to the bottom of the force-bearing part, and the main body can extend into the mold cavity formed by the first mold cavity and the second mold cavity; The surface of the portion of the main body extending into the mold cavity is provided with a wear-resistant layer.

2. The mold assembly according to claim 1, wherein: The mold assembly also includes a movable spacer; The movable pad is matched with the shape of the mold cavity, and the surface of the movable pad is provided with a wear-resistant layer; and two movable pads are provided.

3. The mold assembly according to claim 2, wherein: The main body, the pressing head and the movable pad are formed of a first non-magnetic steel, the Rockwell hardness of the first non-magnetic steel is 53-67, and the magnetic permeability of the first non-magnetic steel is ≤1.8; The lower ferrule and the upper ferrule are formed of a second non-magnetic steel, the Vickers hardness of the second non-magnetic steel is 350-450, and the magnetic permeability of the second non-magnetic steel is ≤1.

8.

4. The mold assembly according to claim 1, wherein: The thickness of the transition layer is 0.05 to 0.5 mm, and the transition layer contains Ni, Cr, Al and Y; The thickness of the wear-resistant layer is 10-20 μm, and the wear-resistant layer contains tungsten carbide, Co and Cr.

5. The mold assembly according to claim 1, wherein: The first portion of the first main body side surface has an inner concave portion and an outer convex portion, and the inner concave portion of the first portion of the first main body side surface is close to the first mold cavity; The second portion of the first main body side surface has an inner concave portion and an outer convex portion, and the outer convex portion of the second portion of the first main body side surface is close to the first mold cavity; The first portion of the second main body side surface has an inner concave portion and an outer convex portion, and the outer convex portion of the first portion of the second main body side surface is adjacent to the second mold cavity; the inner concave portion of the first portion of the second main body side surface matches the outer convex portion of the first portion of the first main body side surface, and the outer convex portion of the first portion of the second main body side surface matches the inner concave portion of the first portion of the first main body side surface; The second part of the second main body side has an inner recess and an outer protrusion, the inner recess of the second part of the second main body side is close to the second mold cavity, the inner recess of the second part of the second main body side matches the outer protrusion of the second part of the first main body side, and the outer protrusion of the second part of the second main body side matches the inner recess of the second part of the first main body side.

6. The mold assembly according to claim 1, wherein: A positioning hole is provided on the top surface of the first body, and a positioning hole is provided on the top surface of the second body; A positioning pin is provided at a position in the upper clamping sleeve slot that matches the positioning hole.

7. The mold assembly according to claim 1, wherein: The portion of the first main body curved surface located in the upper ferrule slot smoothly transitions from the top to the bottom of the main body and bulges outward; the angle between L1 and L2 is 0.5-5°; Wherein, L1 is a straight line passing through the intersection of the first main body curved surface and the top surface of the first main body and perpendicular to the top surface of the first main body; L2 is a straight line passing through the intersection of the first main body curved surface and the bottom surface of the upper ferrule and tangent to the first main body curved surface; L1 and L2 are located in the same plane; The portion of the first main body curved surface located in the lower ferrule slot smoothly transitions from the bottom of the main body to the top and bulges outward; the angle between L3 and L4 is 0.5-5°; Wherein, L3 is a straight line passing through the intersection of the first main body curved surface and the first main body bottom surface and perpendicular to the first main body bottom surface; L4 is a straight line passing through the intersection of the first main body curved surface and the top surface of the lower ferrule and tangent to the first main body curved surface; L3 and L4 are located in the same plane; The portion of the second main body curved surface located in the upper ferrule slot smoothly transitions from the top to the bottom of the main body and bulges outward; the angle between L5 and L6 is 0.5-5°; Wherein, L5 is a straight line passing through the intersection of the second main body curved surface and the second main body top surface and perpendicular to the second main body top surface; L6 is a straight line passing through the intersection of the second main body curved surface and the bottom surface of the upper ferrule and tangent to the second main body curved surface; L5 and L6 are located in the same plane; The portion of the second main body curved surface located in the lower ferrule slot smoothly transitions from the bottom to the top of the main body and bulges outward; the angle between L7 and L8 is 0.5-5°; Among them, L7 is a straight line passing through the intersection of the second main body curved surface and the second main body bottom surface, and perpendicular to the second main body bottom surface; L8 is a straight line passing through the intersection of the second main body curved surface and the top surface of the lower ferrule, and tangent to the second main body curved surface; L7 and L8 are located in the same plane.

8. The mold assembly according to claim 7, wherein: The roughness of the first main curved surface located in the upper ferrule slot is Ra≤0.8μm; the roughness of the first main curved surface located in the lower ferrule slot is Ra≤0.8μm; the roughness of the second main curved surface located in the upper ferrule slot is Ra≤0.8μm; the roughness of the second main curved surface located in the lower ferrule slot is Ra≤0.8μm.

9. The method for preparing a mold assembly according to any one of claims 2 to 8, characterized in that: The steps include: (1) subjecting the first non-magnetic steel alloy to ultrasonic testing to select non-magnetic steel that complies with GB / T 4162-2008 Grade A; The non-magnetic steel meeting the requirements is vacuum quenched at 800-920°C for 0.5-3h, and then cryogenically treated at -230--180°C for 0.5-3h; the cryogenically treated non-magnetic steel is tempered at 170-230°C for 1-6h to obtain a first non-magnetic steel; Solution treating the second non-magnetic steel alloy at 900-1300° C. for 10-50 minutes, and then water-cooling to obtain the second non-magnetic steel; (2) machining the first non-magnetic steel and the second non-magnetic steel to obtain a first body, a second body, an upper ferrule, a lower ferrule, a pressing head, and a movable pad; (3) spraying a transition layer on the surface of the first portion of the first main body side surface, the second portion of the first main body side surface, the first portion of the second main body side surface, and the second portion of the second main body side surface; A wear-resistant layer is plated on the surface of the first mold cavity, the surface of the second mold cavity, the surface of the movable pad, and the surface of the portion of the pressure head extending into the mold cavity consisting of the first mold cavity and the second mold cavity.

10. A method for orientation pressing using the mold assembly according to any one of claims 2 to 8, characterized in that: The steps include: (A) assembling the first body, the second body, and the lower clamping sleeve, and forming a mold cavity with the first mold cavity and the second mold cavity; (B) placing one of the movable spacers in the mold cavity, and allowing the movable spacer to sink to the bottom of the mold cavity under the action of gravity; adding magnetic powder to the mold cavity, and then adding another movable spacer; (C) assembling the upper card sleeve on top of the first body and the second body; (D) Inserting the main body of the punch into the mold cavity; in the presence of a magnetic field, applying pressure to the force-bearing portion of the punch to orient and compact the magnetic powder to obtain a green body.

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