KR970002093B1 - Method of sintering object - Google Patents

Method of sintering object Download PDF

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KR970002093B1
KR970002093B1 KR1019940036810A KR19940036810A KR970002093B1 KR 970002093 B1 KR970002093 B1 KR 970002093B1 KR 1019940036810 A KR1019940036810 A KR 1019940036810A KR 19940036810 A KR19940036810 A KR 19940036810A KR 970002093 B1 KR970002093 B1 KR 970002093B1
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temperature
binder
carbon content
atmosphere
carbon
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KR1019940036810A
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Korean (ko)
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KR960021299A (en
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윤태식
안상호
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김만제
포항종합제철주식회사
신창식
재단법인산업과학기술연구소
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture 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
    • B22F3/225—Manufacture 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/103—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing an organic binding agent comprising a mixture of, or obtained by reaction of, two or more components other than a solvent or a lubricating agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/1017—Multiple heating or additional steps
    • B22F3/1021—Removal of binder or filler
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2201/00—Treatment under specific atmosphere
    • B22F2201/01—Reducing atmosphere
    • B22F2201/013—Hydrogen

Abstract

A method for manufacturing of sintered body by the metal injection molding controllable the content of carbon comprising the step mixing the carbon containing iron powder or the mixture of the metal powder containing Ni like and the iron powder and then injecting the mixture, the step injecting the mold using injection mold, and the step removing and sinterizing binder is disclosed. Said binder removing step is effected by heating the binder to 280~320deg. C at the heating speed 1deg. C/min under the mixture atmosphere of H2/N2 more than 0.75 or the H2 atmosphere and maintaining said temperature for 0.5~1.5 hr to make carbon content of fat-removed mold 1~2 times of row materials with binder removing. Said sinterizing step following said binder removing step is effected by raising the temperature to 600~720deg. C under the mixture atmosphere of H2/N2 more than 0.05 or the H2 atmosphere, maintaining said temperature for 1 hour or more to make carbon content of presintered body 1.5 times or less of the row powder carbon content and then raising the temperature to final sinterizing temperature under the mixture gas atmosphere of H2/N2 less than 0.25 to obtain desired carbon content and final sinterization at said temperature. Thereby, it is possible to control the carbon content of the sintered body in wide range.

Description

탄소함량을 제어할 수 있는 금속사출성형법에 의한 소결체의 제조방법Method for producing sintered body by metal injection molding that can control carbon content

본 발명은 전자부품, 사무용기기, 총기류부품 및 컴퓨터 부품등에서 사용되는 금속소결체를 금속사출성형법에 의해 제조하는 방법에 관한 것으로써, 보다 상세하게는 결합제 제거 및 소결공정에서 수소와 질소 가스의 혼합비를 조절하므로써 탄소량을 제어할 수 있는 금속사출 성형법에 의한 소결체의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a metal sintered body used in electronic parts, office equipment, firearm parts, computer parts, etc. by metal injection molding, and more specifically, a mixture ratio of hydrogen and nitrogen gas in a binder removal and sintering process. It is related with the manufacturing method of the sintered compact by the metal injection molding method which can control carbon amount by adjusting.

금속사출성형 기술은 플라스틱 사출성형법의 장점인 3차원의 복잡하고 정밀한 제품을 대량으로 제조하는 공정과 주조법 보다 균일한 조직을 얻을 수 있는 분말야금법을 조합한 것이다. 또한 미세한 분말을 사용하여 이론밀도의 93% 이상의 고밀도 소결체를 제조할 수 있다. 통상, 금속사출성형법은 금속분말과 결합제를 일정한 비로 혼합하여 사출성형 가능한 혼합체를 제조하는 공정, 원하는 형상의 금형내로 사출성형하여 사출성형체를 제조하는 공정, 사출성형체에서 결합제를 제거하여 탈지체를 제조하는 공정 및 탈지체를 고온 소결하여 최종 제품을 제조하는 공정으로 이루어진다. 이러한 금속사출성형 공정에 관한 내용은 RM. German의 저서(Powder Injection Molding, Metal Powder Industries Federation, 미국, 1990년)과 대한민국 특허공고 92-7456등에 나타나 있다.Metal injection molding technology combines the advantages of plastic injection molding with the three-dimensional complex and precise process of mass production of powder and powder metallurgy to obtain a more uniform structure than casting. In addition, fine powders can be used to produce high density sintered bodies of 93% or more of theoretical density. In general, the metal injection molding method is a process for producing a compound capable of injection molding by mixing a metal powder and a binder in a constant ratio, a process for producing an injection molded product by injection molding into a mold of a desired shape, to remove the binder from the injection molding to produce a degreasing body And a process for producing a final product by hot sintering the degreasing body. For this metal injection molding process, see RM. It is published in German books (Powder Injection Molding, Metal Powder Industries Federation, USA, 1990) and Korean Patent Publication 92-7456.

금속사출성형에 있어 결합제는 금속분말의 충진특성에 따라 부피비로 30-50% 정도가 첨가되는 것이 보통이며 일반적으로 적어도 두가지 이상의 물질로 구성된다. 금속분말과 결합제는 혼합되어 사출성형용 혼합체를 구성하고 사출성형시 결합제는 결합제의 용융온도 이상에서 금속분말과 함께 유동하여 금형내로 충진되게 하며 냉각후 형상을 유지하는 역할을 한다. 결합제는 최종적으로 제거되어야 하므로 결합제 제거공정을 거치게 된다. 이때 결합제는 사출성형체에 뒤틀림이나 균열등의 결함을 발생시키지 않으면서 제거되어야 하기 때문에 결합제 제거공정은 전체 공정중에서 가장 중요한 단계의 하나이며 장시간을 요하는 공정이다. 금속사출성형법에서 다량으로 첨가되는 결합체의 주성분은 탄소이며 이러한 결합제의 제거시 부적절한 분위기 및 가열조건에서는 최종제품에 원치않는 탈탄이나 침탄반응으로 결국 소결체의 탄소량 제어가 매우 곤란하게 된다. 모든 결합제 제거방법의 최종 단계에는 항상 열분해법을 포함한다(미국 특허 제4,404,166호, 미국 특허 제4,765,950호, 미국 특허 제5,028,367호 등).In metal injection molding, a binder is generally added in a volume ratio of about 30-50%, depending on the filling properties of the metal powder, and is generally composed of at least two materials. The metal powder and the binder are mixed to form an injection molding mixture, and when the injection molding, the binder flows together with the metal powder at a melting temperature of the binder to be filled into the mold and maintains the shape after cooling. Since the binder must be finally removed, the binder is removed. At this time, since the binder should be removed without causing defects such as warping or cracking in the injection molded product, the binder removal process is one of the most important steps in the overall process and requires a long time. In the metal injection molding method, the main component of the binder added in a large amount is carbon, and when the binder is removed, it is difficult to control the carbon content of the sintered body due to undesired decarburization or carburizing reaction in the final product under inappropriate atmosphere and heating conditions. The final step of all binder removal methods always includes pyrolysis (US Pat. No. 4,404,166, US Pat. No. 4,765,950, US Pat. No. 5,028,367, etc.).

상기한 결합제 제거시 수소를 사용하는 경우 결합제 제거에 효과적이나 탈탄 반응을 촉진하게 되어 철제 합금 소결체 제조시 원료금속분말인 카보닐 철분말(제조사에 따라 탄소량 0.7-0.9무게% 함유)의 완전한 탈탄이 발생되어 탄소제어가 어렵게 된다. 이러한 문제를 해결하기 위하여 합금조성으로 카보닐 철분말과 중량비 2%의 니켈 분말을 사용하고 결합제로는 폴리프로필렌-카나우바왁스-파라핀왁스-스테아린산을 사용한 사출성형체를 결합제 제거시 완전하게 탈탄을 시킨후 CO/CO2비를 조절한 가스로 소결이 진행되기 직전에 일정온도에서 유지하여 침탄시킨후 소결하는 방법(D.R. Bankovic, and R.M. German; Advances in Powder Metallurgy Vol.2, 1991, Metal Powder Industries Federation, pp 198-208)이 제안되었으나, 이러한 방법의 경우에는 열처리 온도뿐만 아니라 CO/CO2의 비가 정밀하게 제어되어야 하는데 로내의 약간의 온도구배로도 산소불순물들이 CO/CO2의 비를 이동시키게 되며 결국 부품의 탄소량을 변화시킬 수 있기 때문에 부적절하다고 알려져 있다.When hydrogen is used to remove the binder, it is effective to remove the binder but promotes the decarburization reaction. Is generated, making carbon control difficult. In order to solve this problem, carbonyl iron powder and nickel powder of 2% by weight are used as alloy composition, and the injection molded product using polypropylene-carnauba wax-paraffin wax-stearic acid as a binder is completely decarburized when the binder is removed. After sintering by maintaining the gas at a constant temperature just before the sintering proceeds with a controlled CO / CO 2 ratio (DR Bankovic, and RM German; Advances in Powder Metallurgy Vol. 2, 1991, Metal Powder Industries Federation) , pp 198-208), but in this method, the ratio of CO / CO 2 as well as the heat treatment temperature must be precisely controlled. With a slight temperature gradient in the furnace, oxygen impurities can shift the ratio of CO / CO 2 . It is known to be inadequate because it can change the carbon amount of the component.

상기한 방법에서의 문제점을 해결하기 위하여 동일한 분말과 결합제를 사용한 사출 성형체에서 순수한 질소, 질소수소 혼합가스 및 순수한 수소를 사용하여 탄소량을 제어하기 위한 방법이 시도되었다(M.A. Phillips 외 4명, Powder Injection Molding Symposium-1992, Metal Powder Industries Federation, pp 37-384).In order to solve the problems of the above method, a method for controlling the amount of carbon using pure nitrogen, mixed nitrogen hydrogen gas and pure hydrogen in an injection molded body using the same powder and binder has been attempted (MA Phillips et al., Powder Injection Molding Symposium-1992, Metal Powder Industries Federation, pp 37-384).

그러나, 이 방법의 경우에는 결합제 제거후의 탈지체(결합제가 제거 처리된 사출성형체)에 잔류한 탄소량은 순수한 수소의 경우 모든 탄소(분말 및 결합제)의 제거가 진행되었으나 질소-수소 혼합가스의 경우에는 순수한 질소분위기에서 처리한 것보다 탈지체의 탄소량이 많았으며 질소에 수소 가스량이 증가되어도 잔류 탄소량은 더욱 증가하게 되어 혼합가스는 부적절하며, 질소에서 처리하는 경우에만 원료분말의 탄소량을 유지할 수 있는 것으로 설명되고 있다. 이러한 결과는 금속사출성형시 사용되는 결합제가 분위기에 따른 상이한 분해거동을 나타내기 때문인 것으로 설명할 수 있다.However, in the case of this method, the amount of carbon remaining in the degreasing body (binder-treated injection molded body) after binder removal was removed in the case of pure hydrogen, but in the case of nitrogen-hydrogen mixed gas. The amount of carbon in the degreasing body was higher than that in the pure nitrogen atmosphere, and the amount of residual carbon increased even though the amount of hydrogen gas increased in nitrogen, so that the mixed gas was inadequate and the carbon content of the raw material powder was maintained only when treated in nitrogen. It is described as being able. These results can be explained by the fact that the binder used in metal injection molding shows different decomposition behavior depending on the atmosphere.

따라서, 상기한 방법에 있어 질소에서 처리하는 경우 원료분말의 탄소량을 유지할 수 있으므로 탄소량 제어범위가 완료분말의 탄소량에 극한되는 문제점이 있다.Therefore, in the above-described method, since the carbon amount of the raw material powder can be maintained when treated with nitrogen, the carbon amount control range is limited to the carbon amount of the finished powder.

본 발명자들은 상기한 종래의 문제점들을 해결하기 위하여 연구와 실험을 행하고, 그 결과에 근거하고 본 발명을 제안하게 된 것으로써, 본 발명은 금속분말로는 탄소함유철 분말 또는 여기에 Ni과 같은 금속이 함유된 혼합 금속분말을 사용하고, 결합제로는 폴리아미드계를 사용하여 금속사출성형법에 의해 소결체를 제조함에 있어서, 결합제 제거 및 소결공정에서의 가스분위기 즉, 수소와 질소가스의 혼합비를 조절하므로써, 소결체중의 탄소함량을 넓은 범위에 걸쳐 용이하게 제어할 수 있는 금속사출성형법에 의한 소결체의 제조방법을 제공하고자 하는데, 그 목적이 있다.MEANS TO SOLVE THE PROBLEM The present inventors carried out research and experiment in order to solve the above-mentioned conventional problems, and based on the result, the present invention proposes the present invention. The present invention includes a metal powder such as iron-containing iron powder or a metal such as Ni. Sintered compact by using a mixed metal powder, and using a polyamide-based binder as a binder for producing the sintered compact by the metal injection molding method, by adjusting the gas atmosphere in the binder removal and sintering process, that is, mixing ratio of hydrogen and nitrogen gas. An object of the present invention is to provide a method for producing a sintered body by a metal injection molding method which can easily control the carbon content in a wide range.

이하, 본 발명에 대하여 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

본 발명은 탄소함유 철분말 또는 여기에 Ni과 같은 금속이 함유된 혼합금속분말과 폴리아미드계 결합제를 혼합하여 사출성형용 혼합체를 만든 다음, 사출성형하여 사출성형체를 제조한 후, 결합제 제거공정 및 소결공정을 거쳐 소결체를 제조하는 방법에 있어서, 상기한 결합제 제거공정이 질소에 수소의 부피비가 75% 이상인 혼합분위기 또는 수소분위기하에서 1℃/분 이하의 승온속도로 280-320℃까지 승온하고, 이 온도에서 0.5-1.5시간 유지하여 결합제 제거와 함께 탈지성형체의 탄소함량이 원료분말 탄소함량의 1-2배가 되도록 행해지고; 그리고 상기 소결공정이 상기 결합제 제거공정에 이어서 질소에 수소의 부피비가 5% 이상인 혼합분위기 또는 수소분위기하에서 600-720℃까지 승온하고, 이 온도에서 1시간 이상 유지하여 예비소결과 함께 예비소결체의 탄소함량이 원료분말 탄소함량의 1.5배 이하가 되도록 한 다음, 질소에 수소의 부피비가 25% 이하인 혼합가스분위기하에서 최종 소결온도까지 승온하여 이 온도에서 최종소결 및 목적하는 탄소량의 제어가 이루어지도록 구성되는 탄소함량을 제어할 수 있는 금속사출성형법에 의한 소결체의 제조방법에 관한 것이다.The present invention is a carbon-containing iron powder or a mixed metal powder containing a metal such as Ni and a polyamide-based binder is mixed to make an injection molding mixture, and then injection molding to prepare an injection molded body, and then removing the binder In the method for producing a sintered body through the sintering step, the binder removal step is the temperature increase to 280-320 ° C at a heating rate of 1 ° C / min or less under a mixed atmosphere or a hydrogen atmosphere of a volume ratio of hydrogen to nitrogen of 75% or more, Maintained at this temperature for 0.5-1.5 hours so that the carbon content of the degreasing molded body is 1-2 times the raw material powder carbon with binder removal; The sintering step is followed by the binder removal step, and the temperature is raised to 600-720 ° C. under a mixed atmosphere or hydrogen atmosphere in which the volume ratio of hydrogen to nitrogen is 5% or more, and maintained at this temperature for 1 hour or more, and the carbon of the pre-sintered body The content is made to be 1.5 times or less of the raw material powder carbon content, and then the temperature is raised to the final sintering temperature in a mixed gas atmosphere in which the volume ratio of hydrogen to nitrogen is 25% or less, so that the final sintering and control of the desired carbon content are achieved at this temperature. It relates to a method for producing a sintered body by a metal injection molding method capable of controlling the carbon content.

이하, 본 발명에 대하여 상세히 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

본 발명에 따라 소결체를 제조하기 위해서는 우선 금속분말과 결합제를 준비하여야 한다.In order to manufacture a sintered body according to the present invention, first, a metal powder and a binder must be prepared.

본 발명이 적용될 수 있는 금속분말로는 탄소섬유 철분말 또는 여기에다 같은 금속분말이 혼합된 혼합금속분말을 사용하며, 결합제로는 폴리아미드계 결합제를 사용한다.As the metal powder to which the present invention can be applied, a carbon fiber iron powder or a mixed metal powder in which the same metal powder is mixed is used, and as the binder, a polyamide-based binder is used.

상기 탄소함유 철분말의 대표적인 예로는 BASF사의 카보닐 철분말(상품명(CIPOM))을 들 수 있으며, 탄소함유 철분말 중의 탄소의 함량은 0.7-0.9중량%가 바람직하다. 결합제의 대표적인 예로는 일본의 (주)삼화(三和)화학공업사의 폴리아미드로만 구성된 결합제를 들 수 있다.Representative examples of the carbon-containing iron powder may include BASF carbonyl iron powder (trade name (CIPOM)), and the content of carbon in the carbon-containing iron powder is preferably 0.7-0.9% by weight. Representative examples of the binder include a binder composed only of polyamide of Samwha Chemical Co., Ltd. of Japan.

다음에, 상기와 같이 준비된 탄소함유 혼합금속분말과 결합제를 가압식 혼합기등에서 혼합하여 사출성형용 혼합체를 제조한다.Next, the carbon-containing mixed metal powder and the binder prepared as described above are mixed in a pressurized mixer or the like to prepare an injection molding mixture.

다음에, 사출성형용 혼합체를 일반 플라스틱용 정밀사출기등에 의해 사출성형하여 사출성형체를 제조한다.Next, the injection molding mixture is injection molded with a general plastic precision injection machine or the like to produce an injection molded body.

다음에, 상기 사출성형체 중의 결합제를 제거하여 탈지체를 제조하는데, 그 방법은 열분해방법에 의한다.Next, the binder in the injection molded body is removed to prepare a degreasing body, which method is based on a pyrolysis method.

상기 열분해방법은 상온부터 상압의 수소가 포함된 가스를 로내로 흘리면서 알루미나와 같은 기판위에서 사출성형내에 포함되어 있는 결합제를 제거하는 방법이다. 본 발명의 특징중의 하나는 이 열분해 방법에 의해 결합제를 제거할시 가스분위기를 적절히 제어하는데 있다.The pyrolysis method is a method of removing a binder contained in injection molding on a substrate such as alumina while flowing a gas containing hydrogen of normal pressure from normal temperature into a furnace. One of the features of the present invention is to properly control the gas atmosphere when removing the binder by this pyrolysis method.

즉, 본 발명에 있어 결합제 제거공정은 질소에 수소의 부피비가 75% 이상인 혼합분위기 또는 수소분위기하에서 1℃/분 이하의 승온속도로 280-320℃까지 승온하고, 이 온도에서 0.5-1.5시간 유지하여 결합제 제거와 함께 탈지체의 탄소함량이 출발원료인 금속분말의 탄소함량의 1-2배가 되도록 행해진다. 여기서, 승온속도를 1℃/분 이하로 하는 이유는 금속사출성형체에 균열이나 표면기표와 같은 결합이 발생되지 않도록 하기 위함이다.That is, in the present invention, the binder removing step is to increase the temperature to 280-320 ° C. at a temperature rising rate of 1 ° C./min or less under a mixed atmosphere or a hydrogen atmosphere in which the volume ratio of hydrogen to nitrogen is 75% or more, and maintained at this temperature for 0.5 to 1.5 hours. Then, the binder is removed and the carbon content of the degreasing body is made to be 1-2 times the carbon content of the metal powder as the starting material. The reason why the temperature increase rate is 1 ° C./min or less is to prevent cracking and bonding such as surface marks from occurring in the metal injection molded body.

그리고, 상기한 분위기가스성분, 유지온도 및 유지시간은 출발원료인 혼합금속분말의 탄소함량에 좌우되는 것으로써, 상기한 조건으로 결합제를 제거하는 경우 탈지체의 탄소함량이 출발원료인 금속분말의 탄소함량의 1-2배가 된다. 다음에, 280-320℃에서 0.5-1.5시간 유지하여 결합제가 제거된 탈지체를 예비소결 및 최종소결하여 소결체를 제조한다.In addition, the atmosphere gas component, the holding temperature and the holding time depend on the carbon content of the mixed metal powder as the starting material, and when the binder is removed under the above conditions, the carbon content of the degreased body powder of the starting material It is 1-2 times the carbon content. Next, pre-sintering and final sintering of the degreasing body from which the binder was removed by holding at 280-320 ° C. for 0.5-1.5 hours to prepare a sintered body.

즉, 본 발명에 있어 소결공정은 280-320℃로 유지된 탈지체를, 질소에 수소의 부피비가 5% 이상인 혼합 분위기 또는 수소분위기하에서 600-700℃까지 승온하고 이 온도에서 1시간이상 유지하여 예비소결과 함께 예비소결체의 탄소함량이 원료분말 탄소함량의 1.5배 이하가 되도록 예비소결한 다음, 질소에 수소의 부피비가 25% 이하인 혼합가스분위기하에서 최종소결온도까지 승온하여 이 온도에서 최종 소결 및 목적하는 탄소 함량의 제어가 이루어지도록 구성된다. 상기한 예비소결온도 및 시간은 탈지체중의 탄소의 함량 및 목적하는 소결체중의 탄소함량에 좌우된다.That is, in the present invention, the sintering step is to increase the degreasing body maintained at 280-320 ℃, to 600-700 ℃ under a mixed atmosphere or hydrogen atmosphere in which the volume ratio of hydrogen to nitrogen 5% or more and maintained at this temperature for 1 hour or more Presintering is presintered together with the pre-sintered carbon content to be 1.5 times less than the raw powder carbon content, and then heated up to the final sintering temperature in a mixed gas atmosphere where the volume ratio of hydrogen to nitrogen is 25% or less. It is configured to control the desired carbon content. The presintering temperature and time described above depend on the carbon content in the skim body and the carbon content in the desired sintered body.

상기와 같이, 본 발명에 따라 결합제 제거공정및 소결공정을 제어함으로써, 소결체중의 탄소함량을 제어할 수 있을 뿐만아니라 고밀도의 소결체가 제조된다. 본 발명의 바람직한 예로서, 출발원료중의 탄소함량이 0.7-0.9중량%인 경우, 소결체중의 탄소함량을 0.003-0.9% 범위로 제어할 수 있다.As described above, by controlling the binder removal step and the sintering step according to the present invention, not only the carbon content in the sintered body can be controlled, but also a high density sintered body is produced. As a preferred example of the present invention, when the carbon content in the starting material is 0.7-0.9% by weight, the carbon content in the sintered body can be controlled in the range of 0.003-0.9%.

이하, 실시예를 통하여 본 발명을 보다 구체적으로 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.

[실시예]EXAMPLE

본 실시예에서는 금속분말로서 약 0.9중량%의 탄소를 함유한 카보닐 철분말(BASF사의 상품명(CIPOM, 평균입경 : 5㎛)과 중량비로 2%의 니켈분말(INCO사의 상품명 T123, 평균입경 : 6㎛))을 혼합한 혼합금속분말을 사용하였으며, 혼합분말의 탄소, 질소, 및 산소는 각각 중량비로 0.8%, 0.65% 및 0.3%이였다. 결합제로는 폴리아미드로만 구성된 결합제[일본의 (주)삼화(三和)화학공업제품]을 사용하였다.In this embodiment, carbonyl iron powder containing about 0.9% by weight of carbon as a metal powder (BASF trade name (CIPOM, average particle diameter: 5㎛) and 2% nickel powder (INCO brand name T123, average particle diameter: 6 µm)) was used, and the mixed powders of carbon, nitrogen, and oxygen were 0.8%, 0.65%, and 0.3% by weight, respectively. As the binder, a binder composed only of polyamide (Samhwa Chemical Co., Ltd., Japan) was used.

상기와 같이 준비된 금속분말과 결합제를 중량비로 91.8대 8.2로 가압식 혼합기에서 150℃에서 1시간 혼합한 후 펠렛형태의 사출성형을 혼합체를 제조하였다. 상기 사출성형용 혼합체의 탄소, 산소 및 질소 함량은 각각, 6.2%, 1.6%, 및 1.2%정도 분석되었다. 여기서, 상기한 금속분말중의 상기 성분들의 함량과 결합제가 첨가된 사출성형용 혼합체중의 상기 성분들의 함량이 다른 이유는 결합제인 폴리아미드 구조에 탄소, 질소, 및 산소가 포함되어 있기 때문이다.The metal powder and the binder prepared as described above were mixed in a pressurized mixer at a weight ratio of 91.8 to 8.2 for 1 hour at 150 ° C., and then a pellet-shaped injection molding mixture was prepared. Carbon, oxygen and nitrogen contents of the injection molding mixture were analyzed by 6.2%, 1.6% and 1.2%, respectively. The reason why the content of the above components in the metal powder and the content of the above components in the injection molding mixture to which the binder is added is that carbon, nitrogen, and oxygen are included in the binder polyamide structure.

다음에, 상기 사출성형용 혼합체를 사용하여 일반 플라스틱 정밀사출 성형기에서 폭 10mm, 두께 4mm, 길이 60mm이며 게이지 길이가 10mm이고 폭이 3mm인 판상의 인장시편형태의 사출성형체를 제조하였다. 사출성형시 최대압력은 550kg/㎠이었으며 노즐의 온도는 150℃, 금형온도는 50℃이였다. 사출성형체의 결합제 제거, 예비소결 및 소결은 동일한 수평관상로에서 기공률 15%인 알루미나 기판위에서 실온부터 소정의 온도까지 직선적으로 승온하였다. 사출성형체의 결합제는 하기 표 1과 같은 조건으로 제거되었으며, 결합제가 제거된 탈지체중의 탄소함량을 측정하고, 그 결과를 하기 표 1에 나타내었다.Next, using the injection molding mixture, an injection molded article in the form of a plate-shaped tensile specimen having a width of 10 mm, a thickness of 4 mm, a length of 60 mm, a gauge length of 10 mm, and a width of 3 mm was manufactured in a general plastic precision injection molding machine. The maximum pressure during injection molding was 550kg / ㎠, the nozzle temperature was 150 ℃ and the mold temperature was 50 ℃. The binder removal, pre-sintering and sintering of the injection molded product were carried out linearly from room temperature to a predetermined temperature on an alumina substrate having a porosity of 15% in the same horizontal tube furnace. The binder of the injection molded product was removed under the conditions shown in Table 1 below, and the carbon content in the degreasing body from which the binder was removed was measured, and the results are shown in Table 1 below.

* : 나머지는 질소 가스량임*: Remainder is nitrogen gas amount

상기 표 1에서 나타난 바와 같이, 질소에 수소가 5% 포함된 경우(비교탈지체 A) 탈지체에 결함은 없었으나 탄소량이 원료분말의 4배 이상이며, 질소에 수소가 50% 포함된 경우(비교탈지체 B) 탄소량은 감소하였으나 원료분말의 3배 이상이며, 100% 수소로 300℃까지 처리하고 2시간 유지한 경우(비교탈지체 C) 탈지체의 탄소량이 원료분말의 절반이하로 제거되어 부적합함으로 알 수 있다.As shown in Table 1 above, when nitrogen contained 5% of hydrogen (comparative degreasing body A), there was no defect in the degreasing body, but the carbon content was four times or more than that of the raw powder, and when nitrogen contained 50% of hydrogen ( Comparative degreasing body B) The amount of carbon decreased but more than 3 times of raw powder, and treated at 300 ° C with 100% hydrogen and maintained for 2 hours (comparative degreasing body C). It can be seen as inappropriate.

한편, 질소에 수소가 75% 포함된 가스 조성으로 처리한 발명탈지체(1) 및 (2)의 경우에는 승온속도가 분당 0.25℃에서 1℃의 범위에서 탈지체의 탄소량은 1.3%에서 1.6%로 원료분말의 2배 이내에서 제어되고 있음을 알 수 있다. 또한 100% 수소를 사용한 발명탈지체(3)과 (4)도 승온속도가 분당 0.25℃에서 1℃의 범위에서 탈지체의 탄소량은 1.1%에서 1.4%로 원료분말의 2배이내에서 제어되고 있음을 알 수 있다. 탈지체의 질소량은 발명탈지체(1)-(4)중 가장 많은 발명탈지체(2)에서도 0.05% 이하로 제거되었는데, 이는 사출성형용 혼합체중의 금속분말과 폴리아미드 결합제 성분도 거의 제거되었음을 나타낸다.On the other hand, in the case of the invention degreasing body (1) and (2) treated with a gas composition containing 75% of hydrogen in nitrogen, the carbon content of the degreasing body was in the range of 1.3% to 1.6 in the temperature increase rate of 0.25 ° C to 1 ° C. It can be seen that it is controlled within 2 times of the raw material powder in%. In addition, in the invention degreasing body (3) and (4) using 100% hydrogen, the carbon content of the degreasing body was controlled within 1.1 times to 1.4% within 2 times of the raw material powder in the temperature increase rate of 0.25 ° C to 1 ° C. It can be seen that. Nitrogen content of the degreasing body was also removed to 0.05% or less in the invention degreasing body (2) of the invention degreasing body (1)-(4), indicating that almost all metal powder and polyamide binder components in the injection molding mixture were also removed. .

상기와 같이 제조된 탈지체를 하기 표 2와 같은 조건으로 예비소결하여 예비소결체를 제조한 다음, 탄소량을 측정하고, 그 결과를 하기 표 2에 나타내었다.The degreasing body prepared as described above was presintered under the conditions as shown in Table 2 to prepare a presintered body, and then the carbon content was measured, and the results are shown in Table 2 below.

* : 나머지는 질소 가스량임*: Remainder is nitrogen gas amount

상기 표 2에 나타난 바와 같이, 비교탈지체(A)를 동일한 분위기에서 분당 1℃의 승온조건으로 700℃까지 승온하여 1시간 유지하여 예비소결한 비교예비소결체(D)의 경우에는 잔류탄소량도 많을 뿐만 아니라 육안으로도 탄환된 것을 확인할 수 있었다. 이에 반하여 발명탈지체(2)를 각각 질소에 수소가 5%, 10%, 25%, 50%인 가스조성으로 700℃, 1시간 예비소결한 발명예비소결체(5-8)의 경우에는 질소에 수소함량이 증가함에 따라 탄소량은 1.22%에서 0.05%까지 제어되고 있음을 알 수 있다. 또한, 발명탈지체(4)를 질소에 수소가 5%인 가스조성으로 예비소결한 발명예비탈지체(9)의 경우에는 75% 수소의 조성으로 결합제 제거 처리된 발명탈지체(2)를 예비소결한 발명예비소결체(5) 보다는 낮은 1.1%를 나타내어 결합제 제거공정이나 예비소결처리에서 잔류탄소는 수소함량이 증가에 따라 감소함을 알 수 있다.As shown in Table 2, in the case of the comparative pre-sintered body (D) in which the comparative degreasing body (A) was pre-sintered by raising the temperature to 700 ° C. under the same atmosphere at a temperature of 1 ° C. per minute and maintaining it for 1 hour. Not only many, but also visually confirmed bullets. On the contrary, in the case of the invention pre-sintered body (5-8) in which the invention degreasing body (2) was pre-sintered at 700 ° C. for 1 hour in a gas composition containing 5%, 10%, 25%, and 50% hydrogen in nitrogen, respectively, As the hydrogen content increases, the carbon content is controlled from 1.22% to 0.05%. In addition, in the case of the invention preliminary degreasing body (9) in which the invention degreasing body (4) is presintered in a gas composition containing 5% of hydrogen in nitrogen, the invention degreasing body (2) prepared by removing the binder with a composition of 75% hydrogen is prepared. It shows that 1.1% lower than the sintered invention pre-sintered body (5), the residual carbon in the binder removal process or pre-sintering treatment decreases with increasing hydrogen content.

상기와 같이 예비소결된 예비소결체를 하기 표 3과 같은 조건으로 소결한 후 탄소량을 측정하고, 그 결과를 하기 표 3에 나타내었다.The pre-sintered presintered body as described above was sintered under the conditions as shown in Table 3 and then the carbon amount was measured, and the results are shown in Table 3 below.

* : 나머지는 질소 가스량임*: Remainder is nitrogen gas amount

상기 표 3에 나타난 바와 같이, 비교예비소결체(D)를 질소에 수소가 5% 포함된 분위기로 1200℃에서 1시간 소결한 비교소결체(E)의 경우에는 소결체의 탄소량이 1.9%로 높을 뿐만아니라 예비소결시 잔류한 탄소는 표면에 더욱 많이 잔류하여 표면에서 국부적인 용융현상으로 소결체가 뒤틀리고 표면은 부풀어 오르게 됨을 확인하였다. 한편 발명예비소결체(5)를 각각 질소에 수소가 5% 및 25%인 분위기에서 소결한 발명 소결체(10) 및 (11)의 경우에는 각각 탄소의 함량이 0.83% 및 0.75%임을 알 수 있으며, 발명소결체(11)의 경우가 소결분위기중 수소함량이 많아 탈탄은 약간 더 진행되었지만 기계적인 특성에 큰 저하는 관찰되지 않는다.As shown in Table 3, in the case of the comparative sintered compact (E), in which the comparative pre-sintered compact (D) was sintered at 1200 ° C. for 1 hour in an atmosphere containing 5% hydrogen in nitrogen, the carbon content of the sintered compact was not only high as 1.9%. It was confirmed that the carbon remaining during pre-sintering remained on the surface, causing the sintered body to distort and swell due to local melting phenomenon on the surface. On the other hand, in the case of the invention sintered bodies (10) and (11) in which the invention pre-sintered body (5) was sintered in nitrogen in an atmosphere of 5% and 25% of hydrogen, respectively, the content of carbon was 0.83% and 0.75%, respectively. In the case of the inventive sintered body 11, the decarburization proceeded slightly more because of the high hydrogen content in the sintering atmosphere, but no significant deterioration in mechanical properties was observed.

또한, 발명예비소결체(6), (7), (8)을 질소에 5% 수소가 포함된 가스 분위기하에서 소결한 발명소결체(12), (13), (14)의 경우에는 각각의 예비소결체에서의 탄소량보다는 감소하였으나 탄소량이 일정하게 제어되며 순철의 이론밀도의 95% 이상인 고밀도의 소결체가 모든 조건에서 얻어짐을 알 수 있다.In addition, in the case of the invention sintered bodies (6), (7), (8) sintered under a gas atmosphere containing 5% hydrogen in nitrogen, in the case of the invention sintered bodies (12), (13), and (14), the respective presintered bodies Although it is reduced from the amount of carbon at, it can be seen that the carbon content is controlled uniformly and a high density sintered body of 95% or more of the theoretical density of pure iron is obtained under all conditions.

Claims (2)

탄소함유 철분말 또는 여기에 Ni과 같은 금속이 함유된 혼합금속분말과 폴리아미드계 결합제를 혼합하여 사출성형용 혼합체를 만든 다음, 사출성형하여 사출성형체를 제조한 후, 결합제 제거공정 및 소결공정을 거쳐 소결체를 제조하는 방법에 있어서, 상기한 결합제 제거공정이 질소에 수소의 부피비가 75% 이상인 혼합분위기 또는 수소분위기하에서 1℃/분 이하의 승온속도로 280-320℃까지 승온하고, 이 온도에서 0.5-1.5시간 유지하여 결합제 제거와 함께 탈지성형체의 탄소함량이 원료분말 탄소함량의 1-2배가 되도록 행해지고; 그리고 상기 소결공정이 상기 결합제 제거공정에 이어서 질ㅅ에 수소의 부피비가 5% 이상인 혼합분위기 또는 수소분위기하에서 600-720℃까지 승온하고, 이 온도에서 1시간 이상 유지하여 예비소결과 함께 예비소결체의 탄소함량이 원료분말 탄소함량의 1.5배 이하가 되도록 한 다음, 질소에 수소의 부피비가 25% 이하인 혼합가스분위기하에서 최종 소결온도까지 승온하여 이 온도에서 최종소결 및 목적하는 탄소량의 제어가 이루어지도록 구성됨을 특징으로 하는 탄소함량을 제어할 수 있는 금속사출성형법에 의한 소결체의 제조방법.Iron injection powder containing carbon or mixed metal powder containing metal such as Ni and polyamide-based binder is mixed to make injection molding mixture, and then injection molding to prepare injection molding, and then binder removal and sintering In the method for producing a sintered body, the binder removing step is carried out in a mixed atmosphere or a hydrogen atmosphere in which the volume ratio of hydrogen to nitrogen is 75% or more, and the temperature is raised to 280-320 ° C. at a temperature rising rate of 1 ° C./min or less at this temperature. Maintained at 0.5-1.5 hours to remove the binder, so that the carbon content of the degreasing molded product is 1-2 times the carbon content of the raw powder; The sintering step is followed by the binder removal step to increase the temperature to 600-720 ° C. under a mixed atmosphere or a hydrogen atmosphere in which the volume ratio of hydrogen is 5% or more, and maintain the temperature at this temperature for at least 1 hour to maintain the pre-sintered body. The carbon content is made to be 1.5 times or less of the raw material powder carbon, and then the temperature is raised to the final sintering temperature in a mixed gas atmosphere in which the volume ratio of hydrogen to nitrogen is 25% or less, so that final sintering and control of the desired carbon content can be performed at this temperature. Method for producing a sintered body by a metal injection molding method capable of controlling the carbon content, characterized in that configured. 제1항에 있어서, 출발금속원료분말의 탄소함량이 0.7-0.9중량%이고, 그리고 최종소결체의 탄소함량이 0.003-0.9% 범위에서 제어되는 것을 특징으로 하는 탄소함량을 제어할 수 있는 금속사출성형법에 의한 소결체 제조방법.The metal injection molding method of claim 1, wherein the carbon content of the starting metal raw material powder is 0.7-0.9% by weight, and the carbon content of the final sintered body is controlled in the range of 0.003-0.9%. Sintered body manufacturing method by
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Publication number Priority date Publication date Assignee Title
KR101230286B1 (en) * 2010-07-19 2013-02-05 베스너 주식회사 Method of controlling carbon content in sintered body made by metal injection molding

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101230286B1 (en) * 2010-07-19 2013-02-05 베스너 주식회사 Method of controlling carbon content in sintered body made by metal injection molding

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