Method for forming a brake disc green body

Abstract

The application relates to a method for forming a brake disc green body, which utilizes a new type of die to form a pre-compacted body from powder raw materials required by a brake disc body green body, and then to form a pre-compacted body and powder raw materials required by a brake disc cap green body together, so that wear of a female die caused by the powder raw materials can be avoided, and thus the qualified rate of products can be effectively improved and the service life of the die can be prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of powder metallurgy, in particular to a forming method of a green body of a brake disc. BACKGROUND

[0002] Ceramic particle reinforced aluminum matrix composite material has low density, high specific strength and specific stiffness, high thermal conductivity, and excellent wear resistance and corrosion resistance, and has broad application prospects in the field of lightweight structural parts. Specifically applied to brake discs, the disc body needs to have high temperature resistance, wear resistance and other properties, and the disc cap needs to have relatively high mechanical properties, therefore, the disc body is usually made of high volume fraction ceramic reinforced aluminum matrix composite material, and the disc cap is usually made of low volume fraction ceramic reinforced aluminum matrix composite material to meet the performance requirements of each other. However, when the above brake disc is prepared by using a powder metallurgy process, the high volume fraction ceramic reinforced aluminum matrix composite material will cause wear to the female die during the die forming process of the traditional die. After the female die is worn, the green body pressed will crack during demolding, resulting in a decrease in product pass rate and a decrease in service life of the die. SUMMARY

[0003] Therefore, it is necessary to provide a forming method of a green body of a brake disc, which uses a new die to avoid wear to the female die during die forming of the powder material in the die, thereby improving the product pass rate and prolonging the service life of the die.

[0004] A forming method of a green body of a brake disc, comprising the following steps:

[0005] A forming die of a green body of a brake disc is provided, the forming die of a green body of a brake disc comprises an upper die, a lower die and a female die coaxially arranged, and after the die is closed, the upper die and the lower die enclose the female die to form a closed die cavity; the lower die comprises a lower die inner punch and a lower die outer punch sleeved on the lower die inner punch; the inner wall of the female die comprises a first section extending along the axial direction, a second section extending outwardly at an angle of 0.5°-1.0° away from the axial direction, a third section extending outwardly at an angle of 1.0°-2.0° away from the axial direction, and a fourth section extending outwardly at an angle of 0-1.0° away from the axial direction, and the first section, the second section, the third section and the fourth section are sequentially connected; after the die is closed, the lower die outer punch is at least partially in close contact with the first section, and the upper die is at least partially in clearance fit with the fourth section;

[0006] Providing powder raw materials required for a green body of a disc cap of a brake disc and powder raw materials required for a green body of a disc body of a brake disc;

[0007] After the lower die inner punch is moved to the top surface of the lower die inner punch being flush with the end of the fourth section, and the lower die outer punch is moved to the top surface of the lower die outer punch being flush with the end of the first section, the powder raw materials required for the green body of the disc body of the brake disc are filled in the area enclosed by the second section and the third section.

[0008] Moving the upper die to the level of the top end of the fourth section, and moving the lower die outward to press the pre-pressed blank;

[0009] Moving the upper die out of the cavity, and moving the lower die inward to a set height, and filling the powder raw material needed for the brake cap green body in the pre-pressed blank surrounding area;

[0010] Moving the upper die downward to the level of the top end of the fourth section, and moving the lower die outward and the lower die inward as a whole to press the brake disc green body.

[0011] In one embodiment, the axial height of the second section is 35mm-45mm, the axial height of the third section is 35mm-50mm, and the axial height of the fourth section is 20mm-30mm.

[0012] In one embodiment, the outer wall of the upper die extends in the axial direction; and the outer wall of the lower die outward punch extends in the axial direction.

[0013] In one embodiment, after the die is closed, the single-sided distance between the lower die outward punch and the first section is 0.06mm-0.1mm; and the minimum single-sided distance between the upper die and the fourth section is 0.1mm-0.15mm.

[0014] In one embodiment, the bottom surface of the upper die includes a middle recessed surface and a surrounding raised surface, the shape of the middle recessed surface is matched with the top surface of the lower die inward punch, and the shape of the surrounding raised surface is matched with the top surface of the lower die outward punch.

[0015] In one embodiment, the height difference between the middle recessed surface and the surrounding raised surface is 1.5mm-3mm.

[0016] In one embodiment, the mold further includes a core column coaxially arranged with the cavity, and the upper die and the lower die inward punch are respectively provided with an axial through hole for the core column to pass through.

[0017] In one embodiment, the inner wall of the cavity is provided with a coating treatment, and the raw material for the coating treatment is selected from one of chromium carbide, tungsten carbide, titanium carbide, and vanadium carbide.

[0018] In one embodiment, the hardness of the inner wall of the cavity after the coating treatment is >60HRC, and the surface roughness is <0.5um.

[0019] In one embodiment, the thickness of the coating is 0.02mm-0.2mm.

[0020] The method for forming the green brake disc body comprises the following steps: moving the lower inner punch to the top surface of the fourth section, moving the lower outer punch to the top surface of the first section, filling the required powder material of the green brake disc body in the area surrounded by the second section and the third section, and then moving the upper punch to the top surface of the fourth section and pre-pressing the lower outer punch. Since the first section extends along the axial direction, the second section extends outwardly by 0.5-1.0 degrees away from the axial direction, and the lower outer punch is arranged to be at least partially in close contact with the first section after the mold is closed, the powder material can be effectively prevented from leaking into the area surrounded by the inner wall of the first section, thereby avoiding the abrasion of the inner wall of the first section during the movement of the lower outer punch. Meanwhile, the upper punch is arranged to be in clearance fit with the fourth section after the mold is closed, and the fourth section extends outwardly by 0-1.0 degrees away from the axial direction, which can prevent the upper punch from rubbing against the inner wall of the fourth section during the movement, thereby avoiding the abrasion of the inner wall of the fourth section, and further effectively prolonging the service life of the mold.

[0021] Meanwhile, the first section extends along the axial direction, the second section extends outwardly by 0.5-1.0 degrees away from the axial direction, the third section extends outwardly by 1.0-2.0 degrees away from the axial direction, and the fourth section extends outwardly by 0-1.0 degrees away from the axial direction, which can form a mold cavity structure with gradually increasing inner diameter from bottom to top, thereby effectively avoiding the cracking of the green body during the demolding and improving the qualified rate of the product. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a schematic view of the structure of the green brake disc forming mold according to an embodiment of the present application;

[0023] Figure 2 Fig. 2 is a schematic view of the structure of the inner wall of the lower mold according to an embodiment of the present application. Figure 1 Fig. 2 is a schematic view of the structure of the inner wall of the lower mold according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the present application more comprehensively understood, the present application will be described in more detail below, and the preferred embodiments of the present application will be given. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0025] It should be noted that when an element is referred to as being “arranged” on another element, it can be directly on the other element or there can be an intervening element.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. The use herein of the terms "and / or" includes a set of one or more associated listed items.

[0027] The green brake disc forming method of an embodiment comprises the following steps S110-S160:

[0028] S110, providing a green brake disc forming die.

[0029] Please refer to Figure 1 and 2 The green brake disc forming die 10 comprises an upper die 12, a lower die 14 and a female die 16 coaxially arranged. After clamping, the upper die 12 and the lower die 14 form a closed cavity in the female die 16.

[0030] It can be understood that the shape of the closed cavity is matched with the shape of the green brake disc, and the powder raw material for preparing the green brake disc is filled in the cavity and is pressed to form the green brake disc.

[0031] In this application, the inner wall of the female die 16 comprises a first section 162 extending in the axial direction, a second section 164 extending outwardly by 0.5°-1.0° deviating from the axial direction, a third section 166 extending outwardly by 1.0°-2.0° deviating from the axial direction, and a fourth section 168 extending outwardly by 0-1.0° deviating from the axial direction. After clamping, the lower die 14 is at least partially tightly matched with the first section 162, and the upper die 12 is at least partially gap matched with the fourth section 168.

[0032] Among them, the area enclosed by the first section 162 is used to limit the lower die 14, the area enclosed by the fourth section 168 is used to limit the upper die 12, and the area enclosed by the second section 164 and the third section 166 is used to fill the powder raw material.

[0033] It should be noted that if the deviating angle of any section of the female die inner wall is too large or too small, the green body may be subjected to uneven tensile stress or compressive stress during demolding, thereby causing the green body to crack or deform and reducing the qualified rate of products.

[0034] Further, the axial height of the second section 164 is 35mm-45mm, the axial height of the third section 166 is 35mm-50mm, and the axial height of the fourth section 168 is 20mm-30mm.

[0035] Further, the lower die 14 comprises a lower die inner punch 142 and a lower die outer punch 144 sleeved on the lower die inner punch 142. After clamping, the lower die outer punch 144 is at least partially tightly matched with the first section 162.

[0036] Further, the outer wall of the upper die 12 extends axially, and the outer wall of the lower die outer punch 144 extends axially. After the mold is closed, the minimum single-side distance between the upper die 12 and the fourth section 168 is 0.1 mm to 0.15 mm. The single-side distance between the lower die outer punch 144 and the first section 162 is 0.1 mm to 0.15 mm.

[0037] It should be noted that when the fourth section 168 extends outwardly by 0° away from the axial direction, the fourth section 168 is equivalent to extending axially, at this time, the outer wall of the upper die 12 is arranged in parallel with the fourth section 168, and the single-side distance between the upper die 12 and the fourth section 168 is always consistent and can be valued in the range of 0.1 mm to 0.15 mm; when the fourth section 168 extends outwardly by 0 to 1.0° away from the axial direction, and does not include 0°, then the single-side distance between the upper die 12 and the fourth section 168 has a minimum value and a maximum value, and the minimum value can be valued in the range of 0.1 mm to 0.15 mm.

[0038] Further, the bottom surface of the upper die 12 includes a middle recessed surface 122 and a surrounding raised surface 124, wherein the shape of the middle recessed surface 122 is adapted to the top surface of the lower die inner punch 142, and the shape of the surrounding raised surface 124 is adapted to the top surface of the lower die outer punch 144.

[0039] Further, the height difference between the middle recessed surface 122 and the surrounding raised surface 124 is 1.5 mm to 3 mm. The middle recessed surface 122 is used to be clamped with the lower die inner punch 142 when the outer ring is filled with powder, so as to prevent the powder from leaking into the inner ring area when the outer ring is filled with powder.

[0040] In the present embodiment, the mold 10 further includes a core column 18 coaxially arranged with the female die 16. The upper die 12 is provided with an axial through hole 182 through which the core column 18 passes, and the lower die inner punch 142 is provided with an axial through hole 184 through which the core column 18 passes. The core column 18 can move axially in the axial through hole 182 and the axial through hole 184.

[0041] It can be understood that the core column 18 is mainly used for forming the annular brake disc green body.

[0042] The above brake disc green body forming mold 10, after the mold is closed, the upper die 12 and the fourth section 168 are gap fitted, the fourth section 168 extends outwardly by 0 to 1.0° away from the axial direction, which can prevent the upper die 12 from rubbing against the inner wall of the fourth section female die during movement, thereby avoiding abrasion to the inner wall of the fourth section female die; the lower die 14 and the first section 162 are tightly fitted, the first section 162 extends axially, and the second section 164 extends outwardly by 0.5° to 1.0° away from the axial direction, which can prevent the powder raw material from leaking into the area enclosed by the inner wall of the first section female die, thereby avoiding abrasion to the inner wall of the first section female die during movement of the lower die 14; and further effectively prolonging the service life of the mold.

[0043] Meanwhile, the first section 162 extends axially, the second section 164 extends outwardly by 0.5°-1.0° away from the axial direction, the third section 166 extends outwardly by 1.0°-2.0° away from the axial direction, and the fourth section 168 extends outwardly by 0-1.0° away from the axial direction, so as to form a cavity structure of the female mold which gradually increases in inner diameter from bottom to top, thereby effectively avoiding cracking of the blank during demolding and improving the qualification rate of the product.

[0044] In order to further improve the hardness and wear resistance of the inner wall of the female mold and prevent it from being worn, the inner wall of the female mold is subjected to coating treatment in the embodiment. The raw material for the coating treatment is selected from one of chromium carbide, tungsten carbide, titanium carbide and vanadium carbide.

[0045] After the treatment, the hardness of the inner wall of the female mold is greater than 60HRC, and the surface roughness is less than 0.5um.

[0046] Further, the thickness of the coating is 0.02mm-0.2mm. If the coating is too thick, the inner diameter of the female mold will be reduced, thereby affecting the size and shape of the blank and reducing the qualification rate of the product. Meanwhile, the coating will also increase the stress between the coating and the inner wall of the female mold, which is easy to cause the coating to fall off or crack, thereby affecting the service life of the mold. If the coating is too thin, the protection of the coating on the inner wall of the female mold will be insufficient, which cannot effectively prevent the wear of the inner wall of the female mold by the powder raw material, thereby affecting the service life of the mold. Meanwhile, the hardness and wear resistance of the coating will be reduced, thereby affecting the quality and performance of the product.

[0047] S120, providing the powder raw material required for the brake disc cap green body and the powder raw material required for the brake disc body green body.

[0048] In the embodiment, the powder raw material required for the cap green body is a low-volume ceramic particle reinforced aluminum matrix composite material, and the powder raw material required for the body green body is a high-volume ceramic particle reinforced aluminum matrix composite material.

[0049] Further, the powder raw material required for the cap green body is a ceramic particle reinforced aluminum matrix composite material with a ceramic particle mass content of 30% or less, so as to meet the high strength and processability required by the brake disc cap; and the powder raw material required for the body green body is a ceramic particle reinforced aluminum matrix composite material with a ceramic particle mass content of 50% or more, so as to meet the wear resistance and heat resistance required by the brake disc body.

[0050] S130, moving the lower mold inner punch 142 to the top surface of which is flush with the end of the fourth section 168, and moving the lower mold outer punch 144 to the top surface of which is flush with the end of the first section 162, and then filling the area enclosed by the second section 164 and the third section 166 with the powder raw material required for the brake disc body green body.

[0051] It should be noted that the top end of the fourth section 168 is the connecting end of the third section 166 and the fourth section 168, and the end of the fourth section 168 away from the top end is the end thereof. The end of the first section 162 is the connecting end of the first section 162 and the second section 164, and the end of the first section 162 away from the end thereof is the top end thereof.

[0052] In this process, the lower mold outer punch 144 is in close cooperation with the first section 162, the first section 162 extends in the axial direction, and the second section 164 extends outwardly at an angle of 0.5°-1.0° away from the axial direction, so that the powder raw material required for the disc body green body can be effectively prevented from leaking into the area enclosed by the first section 162, thereby effectively avoiding the abrasion of the inner wall of the female mold caused by the lower mold outer punch 144 during movement.

[0053] S140, moving the upper mold 12 to the bottom surface thereof being flush with the top end of the fourth section 168, and moving the lower mold outer punch 144 upwardly to pre-press, to obtain a pre-pressed body.

[0054] In the embodiment, the bottom surface of the upper mold 12 includes the middle recessed surface 122 and the surrounding raised surface 124, so that in step S140, the upper mold 12 needs to be moved to the surrounding raised surface 124 thereof being flush with the top end of the fourth section 168.

[0055] S150, moving the upper mold 12 out of the female mold 16, moving the lower mold inner punch 142 to a set height, and filling the powder raw material required for the disc cap green body in the area enclosed by the pre-pressed body.

[0056] S160, moving the upper mold 12 downwardly to the bottom surface thereof being flush with the top end of the fourth section 168, moving the lower mold outer punch 144 and the lower mold inner punch 142 upwardly to press, and demolding to obtain a brake disc green body.

[0057] In the embodiment, the bottom surface of the upper mold 12 includes the middle recessed surface 122 and the surrounding raised surface 124, so that in step S160, the upper mold 12 needs to be moved to the surrounding raised surface 124 thereof being flush with the top end of the fourth section 168.

[0058] It should be noted that the lower mold outer punch 144 and the lower mold inner punch 142 are moved upwardly to press as a whole, and the disc cap green body is demolded after the bottom surface of the disc cap green body is flush with the bottom surface of the disc body green body.

[0059] In the embodiment, the demolding process is as follows: moving the upper mold 12 out of the female mold 16, moving the lower mold outer punch 144 and the lower mold inner punch 142 upwardly as a whole, until the top surfaces of the lower mold outer punch 144 and the lower mold inner punch 142 reach the end of the fourth section 168, and then moving out the brake disc green body.

[0060] The above brake disc green body forming method uses the mold 10 to make the powder raw material required by the brake disc body green body first form a pre-compacted body, and then makes the powder raw material required by the brake disc cap green body and the pre-compacted body together to be pressed and formed. In the pre-compaction forming process, the powder raw material will not cause wear to the inner wall of the female mold, thereby effectively improving the qualified rate of the product and prolonging the service life of the mold.

[0061] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method of forming a green brake disc, characterised in that, The method comprises the following steps: A brake disc green compact forming die is provided, which comprises coaxially arranged upper and lower dies and a cavity die, and the upper and lower dies form a closed cavity after being closed, wherein the lower die comprises an inner punch and an outer punch arranged on the inner punch, the inner wall of the cavity die comprises a first section extending along the axial direction, a second section extending outward by 0.5-1.0 degrees away from the axial direction, a third section extending outward by 1.0-2.0 degrees away from the axial direction, and a fourth section extending outward by 0-1.0 degrees away from the axial direction, and the first, second, third and fourth sections are sequentially connected, the outer punch of the lower die is in close contact with the first section at least partially after being closed, and the upper die is in clearance fit with the fourth section at least partially, the outer wall of the upper die extends along the axial direction, the outer wall of the outer punch of the lower die extends along the axial direction, the single-side distance between the outer punch of the lower die and the first section is 0.06-0.1 mm after being closed, and the minimum single-side distance between the upper die and the fourth section is 0.1-0.15 mm; The powder raw materials required for a brake disc cap green compact and the powder raw materials required for a brake disc body green compact are provided, the powder raw materials required for the cap green compact are ceramic particle reinforced aluminum matrix composites with a ceramic particle mass content of less than or equal to 30%, and the powder raw materials required for the body green compact are ceramic particle reinforced aluminum matrix composites with a ceramic particle mass content of more than or equal to 50%; The inner punch of the lower die is moved to be flush with the end of the fourth section, the outer punch of the lower die is moved to be flush with the end of the first section, and the powder raw materials required for the brake disc body green compact are filled in the area enclosed by the second and third sections; The upper die is moved to be flush with the top end of the fourth section, the outer punch of the lower die is pressed upward, and a pre-pressed compact is obtained; The upper die is moved out of the cavity die, the inner punch of the lower die is moved to a set height, and the powder raw materials required for the brake disc cap green compact are filled in the area enclosed by the pre-pressed compact; The upper die is moved downward to be flush with the top end of the fourth section, the outer punch of the lower die and the inner punch of the lower die are integrally pressed upward, and a brake disc green compact is obtained after demolding.

2. The green brake disc forming method of claim 1, wherein, The axial height of the second section is 35-45 mm, the axial height of the third section is 35-50 mm, and the axial height of the fourth section is 20-30 mm.

3. The green brake disc forming method of claim 1, wherein, The bottom surface of the upper die comprises a middle recessed surface and a surrounding raised surface, the shape of the middle recessed surface is matched with the top surface of the inner punch of the lower die, and the shape of the surrounding raised surface is matched with the top surface of the outer punch of the lower die.

4. The green brake disc forming method of claim 3, wherein, The height difference between the middle recessed surface and the surrounding raised surface is 1.5-3 mm.

5. The green brake disc forming method of claim 1, wherein, The die further comprises a core column coaxially arranged with the cavity die, and the inner punches of the upper and lower dies are respectively provided with axial through holes through which the core column passes.

6. The green brake disc forming method of claim 1, wherein, The cavity die of the provided brake disc green compact forming die is subjected to coating treatment, and the raw material used in the coating treatment is selected from one of chromium carbide, tungsten carbide, titanium carbide and vanadium carbide.

7. The green brake disc forming method of claim 6, wherein, The hardness of the inner wall of the female mold after coating treatment is greater than 60HRC, and the surface roughness is less than 0.5um.

8. The green brake disc forming method of claim 6, wherein, The thickness of the coating is 0.02mm~0.2mm.

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