JP3442427B2 - Manufacturing method of sintered member - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered member with less contamination of gas and impurities and with less surface damage. 2. Description of the Related Art In recent years, as the size of a plant has increased, the integration of electronic devices, mainly semiconductor components, and the functionality of systems have advanced, the requirements for materials and components have become severer and more sophisticated. ing. In order to meet this demand, it is essential that materials or parts be highly purified while maintaining prices at an industrial level. In general, these materials or parts are materials obtained by pressing, molding, and then melting, sintering, and sintering and infiltration methods in a specified atmosphere level using raw materials that have been thoroughly examined. Are subjected to various processes such as heat treatment and finishing, and are turned into target products and semi-finished products. Here, raw materials that have been thoroughly examined can be industrially easily prepared as raw materials and powders having target performances by recent advances in scouring and pulverizing techniques. For example, the atmosphere in each process is
It is also possible to easily and economically prepare high-performance equipment capable of performing operations in an inert or reducing atmosphere such as vacuum, nitrogen, argon, and hydrogen. However, in the heat treatment step, it is not easy to prepare and accurately quantify and control various conditions at the moment when the treatment is performed at the industrial level. Therefore, the raw material technology becomes particularly important. [0003] That is, the present inventor examined each of the above-mentioned steps in order to obtain a sound material or component having a target performance. Variations in the properties of the molded object, which are thought to be caused by processing technology, and (b) the physical and chemical conditions of the melting crucible and sintering boat that are heated together with the material or component during heat treatment such as melting and sintering. Due to the effects of
It was found that the quality (eg, soundness of the surface state) of the obtained material or component (product) was affected. As powders for powder metallurgy, metal powders such as copper, iron, nickel, chromium, titanium, tungsten and tantalum, and alloy powders such as stainless steel are generally used. The heat treatment performed at the time of manufacturing a material or component using these powder metallurgy raw materials generally includes a heat treatment support member (a container, a crucible, Boats) are essential. As described above, the material or component is inserted or placed in a heat treatment support member (hereinafter, also referred to as a heat treatment container) and subjected to heat treatment to produce a product or a semi-finished product.
The material or component comes into direct contact with graphite as a material for the heat treatment container during the heat treatment, and the material or component and carbon may exhibit a metallurgical reaction. As a result, the raw material or the component may not be taken out of the heat treatment container in a sound form and may be damaged, or the heat treatment container may be damaged, and surface shape inconvenience may be observed. These not only cause fatal damage to the product, but also cause a serious problem of economic loss. [0005] The problems of the prior art described above will be summarized and described. Problem 1: In the production of a sintered member, prior to heat treatment, raw material powders are mixed, and then compacted into a predetermined shape by a molding press machine and subjected to sintering and heat treatment. . By compacting the raw material powder, the workability during heat treatment (during sintering) is improved, the volume of the raw material powder is reduced, the sinterability is improved, and the density of the member after sintering is increased. And many other benefits. However, since the powder is compressed by the molding press machine, gas remains inevitably in the interior. During the heat treatment (during sintering), the sintered body is discolored or oxidized, or the volume of the gas is expanded. Problems such as swelling and deformation of the sintered body may be observed. It is considered that these are all caused by gas confinement during molding, and that the outlet is closed by the progress of sintering before the gas is sufficiently discharged outside during sintering. In addition, due to the difference in fluidity of the raw material powder at the time of loading into a mold and the difference in pressure transmission to the raw material powder of a molding pressure related to a molding technique at the time of molding, uniformity with little variation in density and the like is obtained. The production of a molded or / and sintered body
It has become difficult. This is because not only does the pressing force applied to each molded body vary during the molding operation of each molded body, but also the pressure due to the location inside the molded body after pressurization due to the aforementioned difference in fluidity. It is thought to be due to the difference in distribution. Problem 2: During the sintering of the molded body,
As a container for accommodating the molded body during the heat treatment, a carbon heat treatment container is known. This utilizes the excellent reducing power of carbon (carbon) at a high temperature and the low wettability with many metals, and is widely used industrially. [0008] However, the carbon heat treatment container has the above-mentioned advantages, but on the other hand, depending on the material to be heat-treated or the material of the part, a remarkable metallurgical reaction occurs between the two, and the material or the material in a healthy state is not produced. An obstacle to the production of parts. For example, as a material or part,
When iron, chromium, titanium, etc. are selected, iron carbide,
The formation of chromium carbides and titanium carbides is not preferable because damage to the material or the surface of the component and breakage of the heat treatment container are observed. As a technique for suppressing such a metallurgical reaction, a technique of interposing an aluminum oxide fine particle layer between the two has been developed. However, iron, chromium, titanium, and the like are affected by moisture and gas present in the gaps between the fine particles or on the surface of the fine particles, which may again hinder the production of materials or components in a healthy state. . Accordingly, an object of the present invention is to provide a method for manufacturing a sintered member capable of obtaining a sintered member free from obstacles such as systematic segregation, surface damage, and contamination. [0010] In order to solve the above-mentioned problems, the present invention provides a carbon heat treatment container made of carbon (C).
The surface of the vessel is coated with chromium (Cr), and the chrome surface is carbonized.
Chromium (Cr ₃ C ₂ ) or chromium oxide (Cr ₂ O ₃ )
A first step of obtaining a heat treatment container, and
Place the chromium powder in powder form without applying pressure, introduce and heat
And a second step of processing . In the above structure, the carbon (C)
Cover the surface of the heat treatment container with chromium (Cr)
Chromium carbide (Cr ₃ C ₂ ) or chromium oxide (Cr ₂ O)
₃ ) Obtain a heat treatment container as described above and place the original heat treatment container in this heat treatment container.
Place the chromium material in powder form without applying pressure, introduce and add
By heat treatment, during heat treatment,
Carbon (C) as raw material for heat treatment container made of carbon and raw material chromium
It is possible to avoid direct contact with (Cr) .
As a result, no metallurgical reaction occurs between the two, and the sintered member does not suffer from surface damage and contamination.
In addition, the raw material Cr is placed and introduced on the heat treatment support member without pressurizing, so that the structure due to non-uniform sintering due to non-uniformity of molding pressure distribution due to pressure molding. It is possible to prevent the occurrence of the segregation. The material of the carbon-made heat treatment vessel of the heat treatment vessel is made of carbon having excellent reducing power at high temperatures and low wettability with many metals. It is possible to better achieve the effect of preventing surface damage and contamination of the sintered member. Embodiments of the present invention will be described below with reference to Table 1 by way of specific examples. The gist of the manufacturing method of the present embodiment is that, without applying an external pressure to the target metal to be heat-treated (raw material powder), the metal is placed on a heat-treating support member that satisfies predetermined surface conditions, introduced, and then heated. Is heated and sintered together with the heat-treating support member to obtain a sintered member. Therefore, the type of the target metal
There is no particular limitation. Here, first, Cr is selected as a representative metal of the metal to be heat-treated and will be specifically described. Experiment; very clean surface, thickness 3
Using a high-purity Cr plate having a thickness of mm, a heat treatment container made of a metal Cr plate was prepared. Using a Cr cake obtained by forging after arc melting, a Cr-resistant flange part was manufactured. An experiment was conducted in which the above-mentioned Cr-made contact-resistant flange part was placed in the above-mentioned heat treatment container made of a metal Cr plate in a state of being in direct contact with the heat-treated container at 810 ° C in vacuum. As a result, a strong interdiffusion phenomenon was observed between the heat treatment container made of the Cr plate and the contact flange made of Cr, and the contact flange made of Cr could not be removed from the container without damage. No touch-resistant flange parts could be obtained. However, there was no surface contamination of the Cr contact-resistant flange part and no intrusion of impurities into the inside. Experiment; 3 mm thick with extremely clean surface
Using the high-purity Cr plate, a heat treatment container made of a metal Cr plate was prepared. 4 tons / cm2 of fully degassed Cr powder
A 42 mm diameter corrosion resistant gear part made of Cr powder was manufactured. An experiment was conducted in which the above-mentioned corrosion-resistant gear part made of Cr powder was put into the heat treatment container made of a metal Cr plate in a state of being in direct contact with it and subjected to heat treatment at 810 ° C. in vacuum. As a result, C
In the case of the gear parts made of r, despite the same heat treatment as in the same experiment, a strong interdiffusion phenomenon was observed between the heat treatment container made of Cr plate and the gear parts made of Cr powder, as in the case of the experiment. No Cr was observed, and the degree of damage was lower than in the case of the experiment, and the Cr part could be removed from the container. However, local welds remained as traces of tripping. In addition, there was no surface contamination and no intrusion of impurities into the interior as in the experiment. That is, the present inventors, except for the difference in the surface damage problem of the material or part at the time of removal by both experiments,
From the viewpoints of surface contamination and intrusion of impurities into the interior, observations have shown that a high-purity metal of the same material as the metal to be heat-treated (raw material) is useful as a container for heat treatment (support member for heat treatment). Moreover, considering the fact that the surface damage problem was minor in the case of the latter experiment, prior to the latter experiment, the Cr powder was sufficiently degassed and subjected to a heating treatment. It is considered that the appropriate surface gas remaining in the Cr powder acted on the surface of the heat treatment container whose surface was extremely cleaned, and appropriately formed a film that was hardly wetted. As a result of the microanalysis, the product was a compound of Cr, O, and C. Experiment, Reference Example 1, Comparative Example 1
In each case, flange parts (experimental) and gear parts (experimental) were manufactured from pre-produced Cr material (ingot),
Since it is processed and used as a metal to be heat treated, the Cr material (ingot) is included in the man-hours required to reach the final product.
As a result, the process of manufacturing the product has an effect on the final product price. Also, as in the experiment, when the powder compact (Cr powder) was used as the metal to be heat-treated, the pores and the amount and location of the gas tended to vary, especially when the gas was present in a closed interior. Explosive outgassing during heat treatment can cause surface damage. Therefore, in order to easily release gas from the inside during the heat treatment, the state of the metal to be heat-treated is made into a Cr material (ingot) as in the case of the experiment, that is, in a lump beforehand, or as in the case of the experiment. As an experiment, an experiment was conducted in which a powdered product was introduced into a heat treatment container in the form of a powder in order to easily perform gas release without being made into a compact powder body, that is, a mass state in advance. According to the suggestion of the experiment, the surface of the heat treatment container was made of carbon, and the surface thereof was coated with the same Cr as the metal to be heat treated by a 0.1 μm-thick ion plating method. As a result, a sintered member with less gas and impurities and less surface damage was obtained (experiment, reference example).
1 ). As a heat treatment container, a heat treatment container made of a metal Cr plate using a high-purity Cr plate having a thickness of 3 mm as in the experiment was used. Of the gas tended to vary (Experimental Comparative Example 1). Experimental Reference Example 2 ;
In the above experiment, the surface of the used heat treatment container made of a high-purity Cr plate was used after being extremely cleaned, and the above result was considered as a difference in the result due to the difference in the state of the metal to be heat treated. Therefore, the present inventors made an experimental heat treatment container in which an extremely thin Cr film having a thickness of about 0.1 μm was previously formed on the surface of the carbon heat treatment container by a sputtering method as an experiment. When the same heat treatment as in the experiment was performed using this heat treatment container, the metal to be heat treated ( Reference Example 2 ) could be taken out of the heat treatment container in a sound state without surface damage, and the part was subjected to surface contamination. And no impurities entered the interior. EXPERIMENTAL EXAMPLES 1 and 2 As an experiment, a very thin Cr film having a thickness of about 0.1 μm was formed on the surface of carbon, and the surface was changed to Cr 2 O 3 by adjusting the atmosphere by sputtering. , (Cr-Cr2 O3)
A heat treatment container in which a film was formed on carbon was produced ( Example 1 ). Similarly, a heat treatment container in which an extremely thin (Cr-Cr3 C2) film having a thickness of about 0.1 .mu.m was formed on carbon was produced ( Example 2 ). When a heat treatment similar to the experiment was performed using these heat treatment containers, the metal Cr to be heat treated could be taken out of the heat treatment container in a sound state without surface damage, and the component was
There was no surface contamination and no intrusion of impurities into the inside ( Examples 1 and 2 ). Experiment, Example 3 , Comparative Example 2 As an experiment, a thickness of 100 was adjusted by a vacuum evaporation method while adjusting the atmosphere.
A heat treatment container in which a (Cr-Cr2 O3) coating of about .mu.m was formed on carbon was produced. When the same heat treatment as in the experiment was performed using this heat treatment container, the metal Cr to be heat treated could be taken out of the heat treatment container in a healthy state without surface damage. There was no intrusion of impurities into the interior ( Example
3 ). Further, a heat treatment container was prepared by forming a (Cr-Cr2 O3) film having a thickness of about 0.01 [mu] m on carbon while adjusting the atmosphere by sputtering. When the same heat treatment as in the experiment was performed using this heat treatment container, slight surface damage was found, but the metal Cr to be heat treated could be taken out of the heat treatment container in a substantially healthy state. . However, because the thickness of the coating was not necessary, the moisture and gas existing on the surface and inside of the graphite diffused into the metal Cr to be heat-treated during the heat treatment, and the surface discolored, contaminated and contaminated. Infiltration of impurities,
A healthy Cr part could not be obtained (Comparative Example 2). After the metal to be heat treated (raw material) is introduced and placed in the heat treatment vessel, the porosity of the sintered member, that is, the theoretical density, is adjusted by adjusting the heat treatment temperature, the particle size of the raw material, and adding a sintering aid. The ratio of the voids can be adjusted in a wide range of about 30 to 95% . The present inventors have found that even in a heat treatment container in which a metal film is formed on a carbon heat treatment container, surface damage, surface contamination, and intrusion of impurities into the inside are prevented.
It has been found that a sound product or semi-finished product can be obtained. However, if the thickness of the metal coating on the carbon heat treatment container is inappropriate, a strong interdiffusion phenomenon is observed, which is not preferable. As described above, based on the above findings, the present inventor has determined that the pressure applied to the raw material powder before sintering is not only for each sintered member but also for a microscopic portion inside each sintered member. The present invention has been completed as a result of a synergistic combination of the study on the technology that also keeps the constant and the experimental study described above. [Table 1] Condition No. Metal to be heat-treated Heat-treated supporting member Heat-treatment conditions Container material Surface Experiment: Reference Cr-Cr vacuum vacuum Cr-cake 810 ° C (Cr-resistant contact flange part) Experiment: Reference Degas-treated Cr Cr Same as above Cr powder compact ( Experiment: Reference example 1 Degassed carbon Carbon surface same as above Cr powder 0.1 μm thick Cr coated by ion plating method Same as above: Comparative example 1 Same as experiment Cr plate Cr plate As above (thickness: 3 mm) Experiment: Same as in Reference Example 2 Experiment: Coating the surface of carbon and carbon with 0.1 μm thick Cr by the sputtering method Experiment: Same as in Example 1 Experiment: Same as in the experiment of Example 1 0.1 μm thick ( as above ) Cr—Cr2 O3) coating by sputtering method Experiment: Same as in Example 2 Same as above. Carbon surface with 0.1 μm thick (Cr—Cr3 C2) coating as above Coating by sputtering method Experiment: Same as in Example 3 Same as above Experiment 100 mm thick (Cr-Cr2O3) on the carbon surface same as above by vacuum evaporation method Same as above: Comparative Example 2 Same as experiment Same as above on the carbon surface 0.01 [mu] m thick As described above, according to the present invention, the surface of a carbon-made heat treatment container made of carbon is coated with chromium (Cr-Cr2 O3).
Chromium surface or chromium oxide or chromium oxide
Obtain a heat treatment container and place the raw material
Place, introduce, and heat-treat
Therefore, during the heat treatment, the heat treatment container
It is possible to avoid direct contact between the material carbon (C) of the container and the raw material Cr , so that a metallurgical reaction between the two does not occur and a sintered member free of surface damage and contamination is obtained. be able to. In addition, since the raw material Cr is placed on a heat treatment support member without being pressed and introduced and subjected to heat treatment, uneven sintering due to uneven molding pressure distribution caused by pressure molding and the like. Can be prevented, and a sintered member without systematic segregation can be obtained. Further, since the material of the heat treatment container made of carbon is made of carbon , the surface of the sintered member has a good reducing power at a high temperature and low wettability with many metals. The effect of preventing damage and contamination can be better achieved.

──────────────────────────────────────────────────続 き Continuing on the front page (72) The inventor, Manabu Takahashi 8-4, Nihonbashi Koamicho, Chuo-ku, Tokyo Japan Heavy Chemical Industry Co., Ltd. (72) The inventor, Isao Okutomi 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu Plant (72) Inventor Kaoru Sekiguchi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Corporation Yokohama Office (56) References JP-A-56-142804 (JP, A) (58) Fields investigated Int.Cl. ⁷ , DB name) B22F 3/10

Claims (1)

(57) Claims 1. The surface of a carbon heat treatment container made of carbon (C) is coated with chromium (Cr), and the surface of the chromium is coated with chromium carbide (Cr ₃ C ₂ ) or A first step of obtaining a heat treatment container made of chromium oxide (Cr ₂ O ₃ ); and a _second step of placing, introducing, and heating the raw material chromium in the heat treatment container in a powder form without pressurizing. And a method for producing a sintered member.