CN111515389A - Method for directly forming internal reverse buckle by MIM (metal injection molding) - Google Patents

Method for directly forming internal reverse buckle by MIM (metal injection molding) Download PDF

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Publication number
CN111515389A
CN111515389A CN201910320823.5A CN201910320823A CN111515389A CN 111515389 A CN111515389 A CN 111515389A CN 201910320823 A CN201910320823 A CN 201910320823A CN 111515389 A CN111515389 A CN 111515389A
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Prior art keywords
mim
pom
green
degreasing
insert
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CN201910320823.5A
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CN111515389B (en
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严新华
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Shenzhen Oceanwide United Precision Manufacturing Co Ltd
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Shenzhen Oceanwide United Precision Manufacturing Co Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F3/00Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B22F3/225Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F1/00Special treatment of metallic powder, e.g. to facilitate working, to improve properties; Metallic powders per se, e.g. mixtures of particles of different composition
    • B22F1/0003Metallic powders per se; Mixtures of metallic powders; Metallic powders mixed with a lubricating or binding agent
    • B22F1/0059Metallic powders mixed with a lubricating or binding agent or organic material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F3/00Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10Sintering only
    • B22F3/1017Multiple heating or additional steps
    • B22F3/1021Removal of binder or filler
    • B22F3/1025Removal of binder or filler not by heating only

Abstract

The invention discloses a method for directly forming an internal reverse buckle by an MIM (metal injection molding), which comprises the following steps of: (1) preparing MIM feed; (2) manufacturing a POM insert; (3) forming the MIM green body; (4) degreasing; (5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1200 ℃ and 1400 ℃, sintering time: 17-20 h. The POM part is suitable for all metal molds or parts which are difficult to process in the post-process, the POM part needs to be accurately positioned when being placed into the metal mold, the contact surface of the POM part and the MIM green body is covered with a strong nitric acid corrosion resistant material, a large amount of gas generated during cracking is avoided from crushing the green body and holes, the design of the POM part needs to be uniform in wall thickness, the weight is light as much as possible, and the degreasing time can be reduced.

Description

Method for directly forming internal reverse buckle by MIM (metal injection molding)
Technical Field
The invention relates to the technical field of powder metallurgy, in particular to a method for directly forming an internal reverse buckle by MIM.
Background
The MIM process is suitable for mass production of products with complex shapes and high precision. Some products have complex structures (such as internal inverted buckles, thread holes and the like), the mold cannot be completely molded, a part which cannot be molded (such as CNC) needs to be processed by adopting a post process, and the post process causes secondary processing tolerance and high cost. And the size of part of products is too small, so that the post process cannot be realized. The invention can successfully solve the problems and achieve MIM net-shaped products.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for directly forming an internal reverse buckle by MIM, which directly achieves the net forming of a product, effectively solves the problems that the post-MIM process cannot be processed and the processing cost is too high, reduces the production cost, improves the product precision, effectively solves the problems of degreasing cracking, contact surface air holes and the like by covering the surface of a POM (polyoxymethylene) part with a strong nitric acid corrosion resistant material, and obtains a stable product with a smooth surface.
In order to achieve the aim of the invention, the invention adopts the specific scheme that:
a method of MIM direct forming internal undercuts, the method comprising the steps of:
(1) preparing MIM feed: putting 5-8% of binder and 92-95% of iron powder by weight into a mixing roll, mixing uniformly, and cutting the uniformly mixed feed into uniform particles of 1-3mm by a granulator;
(2) manufacturing the POM insert: firstly, drying a POM raw material in a dryer at the temperature of 80-90 ℃ for 3-4h, removing water, then injecting the POM material into a designed insert mold through a forming machine, and manufacturing an insert, wherein the insert needs to be designed according to MIM shrinkage and injection molding pressure: 80-160Pa, mold temperature: covering a layer of strong nitric acid corrosion resistant material on the contact surface of the POM part and the MIM product at the temperature of between 80 and 120 ℃;
(3) forming an MIM green body: put into the MIM mould with the POM mold insert, the POM piece needs design location characteristic, makes things convenient for POM and the accurate location of mould, prevents that injection pressure from dashing it partially, utilizes the injection machine will be injected into the MIM mould with mixed feed, through the injection, the pressurize, the solidification makes MIM raw blank, injection pressure: 80-160Pa, material temperature: 190 ℃ -200 ℃, mold temperature: 90-130 ℃;
(4) degreasing: putting the formed MIM green body into a degreasing furnace for catalyst degreasing, cracking the POM component and the POM insert in the MIM feed into formaldehyde gas under the catalytic action of nitric acid, burning the formaldehyde gas into harmless gas through a degreasing furnace heater, and performing catalytic degreasing temperature on all characteristics of a degreased MIM part net-formed product: 110-: after 5-7 hours, because the contact surface of the POM part and the MIM green body is covered with a layer of strong nitric acid corrosion resistant material, the POM part is isolated from the MIM green body, the POM part and the MIM green body are separated to generate decomposition reaction during degreasing, the POM part is prevented from being cracked too fast to generate a large amount of gas to crush products, or the defects of pores and unevenness generated on the MIM surface by the gas generated by decomposition of the POM part are avoided;
(5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1200 ℃ and 1400 ℃, sintering time: 17-20 h.
Further, the content of POM in the adhesive accounts for 87-93%.
Further, the iron powder requires: d80 is less than or equal to 20 um.
The invention has the beneficial effects that:
POM (polyaldehyde resin) is used as a binder and is quickly catalyzed and degreased in an acidic atmosphere, long-chain polyaldehyde resin is used as the binder, the polarity of the polyaldehyde resin is utilized to connect metal powder, the polyaldehyde resin can be suitable for a wide range of powder types, the polyaldehyde resin is decomposed into formaldehyde under the catalysis of the acidic atmosphere, the decomposition reaction quickly occurs at the temperature of more than 110 ℃, the direct gas-solid conversion is realized, the deformation of a green body is favorably controlled, and the size precision after sintering is ensured; the net forming of the product is directly achieved, the problems that the process cannot be processed after MIM and the processing cost is too high are effectively solved, the production cost is reduced, the product precision is improved, the surfaces of the POM pieces are covered with strong nitric acid corrosion resistant materials, the problems of degreasing cracking, contact surface air holes and the like are effectively solved, and the stable and smooth-surface product is obtained.
Detailed Description
The present invention is further described below by way of specific examples, but the present invention is not limited to only the following examples. Variations, combinations, or substitutions of the invention, which are within the scope of the invention or the spirit, scope of the invention, will be apparent to those of skill in the art and are within the scope of the invention.
Example 1: a method of MIM direct forming internal undercuts, the method comprising the steps of:
(1) preparing MIM feed: putting 5% of binder and 92% of iron powder by weight into a mixing roll, mixing uniformly, and cutting the uniformly mixed feed into uniform particles of 1mm through a granulator;
(2) manufacturing the POM insert: firstly, drying a POM raw material in a dryer at 80 ℃ for 3h, removing moisture, then injecting the POM material into a designed insert mold through a forming machine, manufacturing an insert, wherein the insert needs to be designed according to MIM shrinkage ratio and injection molding pressure: 80Pa, mold temperature: covering a layer of strong nitric acid corrosion resistant material on the contact surface of the POM part and the MIM product at the temperature of 80 ℃;
(3) forming an MIM green body: put into the MIM mould with the POM mold insert, the POM piece needs design location characteristic, makes things convenient for POM and the accurate location of mould, prevents that injection pressure from dashing it partially, utilizes the injection machine will be injected into the MIM mould with mixed feed, through the injection, the pressurize, the solidification makes MIM raw blank, injection pressure: 80Pa, material temperature: 190 ℃, mold temperature: 90 deg.C;
(4) degreasing: putting the formed MIM green body into a degreasing furnace for catalyst degreasing, cracking the POM component and the POM insert in the MIM feed into formaldehyde gas under the catalytic action of nitric acid, burning the formaldehyde gas into harmless gas through a degreasing furnace heater, and performing catalytic degreasing temperature on all characteristics of a degreased MIM part net-formed product: 110 ℃, degreasing time: after 5 hours, because the contact surface of the POM part and the MIM green body is covered with a layer of strong nitric acid corrosion resistant material, the POM part is isolated from the MIM green body, and the POM part and the MIM green body are separated to generate decomposition reaction during degreasing, so that the POM part is prevented from being cracked too fast to generate a large amount of gas to crush products, or the defects of pores and unevenness generated on the surface of the MIM by the gas generated by decomposition of the POM are avoided;
(5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1200 ℃, sintering time: 17.
the POM content of the binder was 87. The iron powder requires: d80 is less than or equal to 20 um.
Example 2: a method of MIM direct forming internal undercuts, the method comprising the steps of:
(1) preparing MIM feed: putting 6.5 wt% of binder and 93.5 wt% of iron powder into a mixing roll, mixing uniformly, and cutting the uniformly mixed feed into uniform particles of 2mm by a granulator;
(2) manufacturing the POM insert: firstly, drying a POM raw material in a dryer at 85 ℃ for 3.5h, removing moisture, then injecting the POM material into a designed insert mold through a forming machine, and manufacturing an insert, wherein the insert needs to be designed according to MIM shrinkage and injection pressure: 120Pa, mold temperature: covering a layer of strong nitric acid corrosion resistant material on the contact surface of the POM part and the MIM product at 100 ℃;
(3) forming an MIM green body: put into the MIM mould with the POM mold insert, the POM piece needs design location characteristic, makes things convenient for POM and the accurate location of mould, prevents that injection pressure from dashing it partially, utilizes the injection machine will be injected into the MIM mould with mixed feed, through the injection, the pressurize, the solidification makes MIM raw blank, injection pressure: 120Pa, material temperature: 195 ℃, mold temperature: 110 ℃;
(4) degreasing: putting the formed MIM green body into a degreasing furnace for catalyst degreasing, cracking the POM component and the POM insert in the MIM feed into formaldehyde gas under the catalytic action of nitric acid, burning the formaldehyde gas into harmless gas through a degreasing furnace heater, and performing catalytic degreasing temperature on all characteristics of a degreased MIM part net-formed product: 120 ℃, degreasing time: after 6 hours, because the contact surface of the POM part and the MIM green body is covered with a layer of strong nitric acid corrosion resistant material, the POM part is isolated from the MIM green body, and the POM part and the MIM green body are separated to generate decomposition reaction during degreasing, so that the POM part is prevented from being cracked too fast to generate a large amount of gas to crush products, or the defects of pores and unevenness generated on the surface of the MIM by the gas generated by decomposition of the POM are avoided;
(5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1300 ℃, sintering time: and (4) 18.5 h.
The POM content in the binder accounts for 90 percent. The iron powder requires: d80 is less than or equal to 20 um.
Example 3: a method of MIM direct forming internal undercuts, the method comprising the steps of:
(1) preparing MIM feed: putting 8% of binder and 95% of iron powder by weight into a mixing roll, mixing uniformly, and cutting the uniformly mixed feed into uniform particles of 3mm through a granulator;
(2) manufacturing the POM insert: firstly, drying a POM raw material in a dryer at 90 ℃ for 4h, removing moisture, then injecting the POM material into a designed insert mold through a forming machine, manufacturing an insert, wherein the insert needs to be designed according to MIM shrinkage ratio and injection molding pressure: 160Pa, mold temperature: covering a layer of strong nitric acid corrosion resistant material on the contact surface of the POM part and the MIM product at 120 ℃;
(3) forming an MIM green body: put into the MIM mould with the POM mold insert, the POM piece needs design location characteristic, makes things convenient for POM and the accurate location of mould, prevents that injection pressure from dashing it partially, utilizes the injection machine will be injected into the MIM mould with mixed feed, through the injection, the pressurize, the solidification makes MIM raw blank, injection pressure: 160Pa, material temperature: 200 ℃, mold temperature: 130 ℃;
(4) degreasing: putting the formed MIM green body into a degreasing furnace for catalyst degreasing, cracking the POM component and the POM insert in the MIM feed into formaldehyde gas under the catalytic action of nitric acid, burning the formaldehyde gas into harmless gas through a degreasing furnace heater, and performing catalytic degreasing temperature on all characteristics of a degreased MIM part net-formed product: 130 ℃, degreasing time: after 7 hours, because the contact surface of the POM part and the MIM green body is covered with a layer of strong nitric acid corrosion resistant material, the POM part is isolated from the MIM green body, and the POM part and the MIM green body are separated to generate decomposition reaction during degreasing, so that the POM part is prevented from being too quickly split to generate a large amount of gas to crush products, or the defects of pores and unevenness on the surface of the MIM caused by the gas generated by decomposition of the POM are avoided;
(5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1400 ℃, sintering time: and (5) 20 h.
The content of POM in the binder was 93%. The iron powder requires: d80 is less than or equal to 20 um.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (3)

1. A method of MIM direct forming internal undercuts, the method comprising the steps of:
(1) preparing MIM feed: putting 5-8% of binder and 92-95% of iron powder by weight into a mixing roll, mixing uniformly, and cutting the uniformly mixed feed into uniform particles of 1-3mm by a granulator;
(2) manufacturing the POM insert: firstly, drying a POM raw material in a dryer at the temperature of 80-90 ℃ for 3-4h, removing water, then injecting the POM material into a designed insert mold through a forming machine, and manufacturing an insert, wherein the insert needs to be designed according to MIM shrinkage and injection molding pressure: 80-160Pa, mold temperature: covering a layer of strong nitric acid corrosion resistant material on the contact surface of the POM part and the MIM product at the temperature of between 80 and 120 ℃;
(3) forming an MIM green body: put into the MIM mould with the POM mold insert, the POM piece needs design location characteristic, makes things convenient for POM and the accurate location of mould, prevents that injection pressure from dashing it partially, utilizes the injection machine will be injected into the MIM mould with mixed feed, through the injection, the pressurize, the solidification makes MIM raw blank, injection pressure: 80-160Pa, material temperature: 190 ℃ -200 ℃, mold temperature: 90-130 ℃;
(4) degreasing: putting the formed MIM green body into a degreasing furnace for catalyst degreasing, cracking the POM component and the POM insert in the MIM feed into formaldehyde gas under the catalytic action of nitric acid, burning the formaldehyde gas into harmless gas through a degreasing furnace heater, and performing catalytic degreasing temperature on all characteristics of a degreased MIM part net-formed product: 110-: after 5-7 hours, because the contact surface of the POM part and the MIM green body is covered with a layer of strong nitric acid corrosion resistant material, the POM part is isolated from the MIM green body, the POM part and the MIM green body are separated to generate decomposition reaction during degreasing, the POM part is prevented from being cracked too fast to generate a large amount of gas to crush products, or the defects of pores and unevenness generated on the MIM surface by the gas generated by decomposition of the POM part are avoided;
(5) and (3) sintering: putting the degreased green body into a hollow furnace for sintering, wherein the sintering temperature is as follows: 1200 ℃ and 1400 ℃, sintering time: 17-20 h.
2. The method of claim 1, wherein the binder comprises about 87-93% POM.
3. The method of claim 1, wherein the iron powder requires: d80 is less than or equal to 20 um.
CN201910320823.5A 2019-04-20 2019-04-20 Method for directly forming internal reverse buckle by MIM (metal injection molding) Active CN111515389B (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5689796A (en) * 1995-07-18 1997-11-18 Citizen Watch Co., Ltd. Method of manufacturing molded copper-chromium family metal alloy article
CN102009175A (en) * 2010-10-08 2011-04-13 李亚东 Manufacturing method of multilayer shell-core composite structural part
CN104325144A (en) * 2014-10-27 2015-02-04 福立旺精密机电(中国)有限公司 Metal injecting molding catalytic debinding method and catalytic debinding furnace
CN105414549A (en) * 2015-12-24 2016-03-23 深圳艾利门特科技有限公司 Metal powder injection molding method for product with inverted buckle structure
CN108421981A (en) * 2017-08-28 2018-08-21 深圳市富优驰科技有限公司 POM plastics are used as can the injection molding application of fusible core

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5689796A (en) * 1995-07-18 1997-11-18 Citizen Watch Co., Ltd. Method of manufacturing molded copper-chromium family metal alloy article
CN102009175A (en) * 2010-10-08 2011-04-13 李亚东 Manufacturing method of multilayer shell-core composite structural part
CN104325144A (en) * 2014-10-27 2015-02-04 福立旺精密机电(中国)有限公司 Metal injecting molding catalytic debinding method and catalytic debinding furnace
CN105414549A (en) * 2015-12-24 2016-03-23 深圳艾利门特科技有限公司 Metal powder injection molding method for product with inverted buckle structure
CN108421981A (en) * 2017-08-28 2018-08-21 深圳市富优驰科技有限公司 POM plastics are used as can the injection molding application of fusible core

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