JP2013082955A - Method for treating sintered product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a sintered product which achieves productivity improvement, laborsaving, quality improvement, and reduction of consumables.SOLUTION: The method for treating a sintered product is provided, in which steam treatment is performed and then gas soft nitriding treatment is performed on the sintered product. As a treatment container which contains the sintered product and/or a tool which supports the sintered product, the treatment container and/or the tool, having an aluminum diffusion coating layer formed on the surface thereof, are used, and also the gas soft nitriding treatment is performed without changing the treatment container and/or the tool after the steam treatment.

Description

  The present invention relates to a method for processing a sintered product, and more specifically, to a method for processing a sintered product that is subjected to steam treatment on a sintered product manufactured by a powder metallurgy method and then subjected to gas soft nitriding.

  Sintered products manufactured by powder metallurgy (hereinafter referred to as “sintered products” in this specification) are less wasteful of materials during production and are suitable for mass production. Application to machine parts is progressing. In each of these machine parts, there is a part that requires hardness depending on the application. In this case, the sintered product is applied with a surface hardening treatment. As the surface hardening treatment, there is a method in which a hardening gas enters or diffuses on the surface of the sintered product, and gas carburizing, gas nitriding, and gas soft nitriding are generally used.

  By the way, the sintered product manufactured by the powder metallurgy method has fine pores derived from the manufacturing method inside, and when performing the above-mentioned surface hardening treatment, the curing gas is relatively easily contained inside the sintered product. Therefore, it is difficult to control the thickness of the cured layer. For this reason, after performing a water vapor treatment (sometimes referred to as a homo-treatment) comprising bringing the sintered product into contact with water vapor, the pores opened on the surface of the sintered product are sealed, and then the above curing treatment is performed. A method (Patent Document 1, etc.) has been proposed.

That is, in the steam treatment (homo treatment), for example, after preheated pressurized steam to 350 to 400 ° C., superheated steam heated to around 500 ° C. is passed through the workpiece, so that the surface of the workpiece is about 5 to 20 μm. This is a technique for forming a thick Fe ₃ O ₄ film, and when applied to a sintered product, the pores are sealed by expansion of the Fe ₃ O ₄ film formed on the surface of the pores.

When the gas soft nitriding treatment is performed on the sintered product in which pores are sealed in this way, the porous Fe ₃ O ₄ layer formed on the surface serves as a kind of filter, and the infiltration rate of nitrogen is uniform. Since Fe ₃ O ₄ is also generated inside the fine pores in the surface layer of the sintered product, it is relatively thin and stable by preventing excessive nitriding gas from entering the sintered product. A nitrided layer can be obtained. In addition, variations in the thickness of the nitride layer due to parts and variations in the thickness of the nitride layer due to differences in installation locations within the processing furnace are reduced. Furthermore, in the case of gas soft nitriding, not only the presence of carbon promotes the diffusion of nitrogen due to the coexistence of CO and H _{2 as} reducing gases, but also the reduction of Fe ₃ O ₄ formed on the surface in parallel. As a result, finally, a nitride layer having a thickness of about 5 to 20 μm with almost no Fe ₃ O _{4 on the} surface is obtained.

  By performing the treatment as described above, a thin nitride layer having a stable thickness can be obtained by gas soft nitriding after steam treatment (homo treatment) even for a sintered product having a fine space inside. Is possible.

Japanese Examined Patent Publication No. 04-070391

  In general, when performing steam treatment or gas soft nitriding treatment on a sintered product manufactured by powder metallurgy, the sintered product is made so that the entire surface of the sintered product can easily come into contact with the curing gas. Is stored in a gas permeable container (for example, a mesh basket, mesh belt, etc.), and the gas permeable container is held or suspended in the air by a column or the like, or the sintered product is held or loaded on a jig or the like. , Steam treatment (homo treatment) or gas soft nitriding treatment is performed. Use of such gas permeable containers and jigs is particularly important in order to optimize the arrangement of the sintered products and increase the processing efficiency.

However, the basket that holds the sintered product, the supporting column, other containers, jigs, etc. are all made of metal materials such as ordinary steel, special steel, and austenitic stainless steel to ensure high temperature strength. Generally, it is configured. Since these containers, jigs, etc. are subjected to steam treatment or gas soft nitriding treatment together with the sintered product, for example, in the steam treatment, not only the sintered product but also the surface of these metal members have Fe. An iron oxide film such as ₃ O ₄ or Fe ₂ O ₃ is formed.

  Therefore, when the gas soft nitriding treatment is performed by using the metal member such as the container and jig used for the steam treatment as it is, the nitriding gas is also performed until the container and the jig are reduced. As a result, more nitriding gas is required than the sintered product requires, and furthermore, it becomes difficult to stably supply the nitriding gas to the sintered product located near the container and jigs, resulting in high gas cost. In addition to increasing the variation in the nitrided layer thickness of the sintered product, it becomes a serious quality problem.

  Therefore, conventionally, metallic members such as containers and jigs used for steam treatment and metallic members such as containers and jigs used for gas soft nitriding have not been mixed and have been used exclusively for each. . That is, after the steam treatment, the container, jigs and sintered product are once taken out of the processing furnace and cooled, and then the sintered product is replaced with a gas soft nitriding vessel and jig. It requires work to be inserted into the furnace, which not only increases work effort and lowers the operating rate of the processing furnace, but also due to the occurrence of damage to parts due to the shortening of the reloading time intended to improve productivity. An increase in the defect rate is inevitable. In addition, the surface layer of metal members such as containers and shellfish becomes excessively hard due to repeated nitridation, and cracks occur and become unusable due to repeated heating and cooling.

  All of these are factors for increasing the cost, and it has been important to achieve reduction in processing time, labor saving, quality improvement, and the like.

  The present invention has been made in order to solve the above problems, and is a processing method of a sintered product in which a sintered product is subjected to steam treatment and then subjected to gas soft nitriding, and the sintered product is accommodated. As a jig for supporting the processing container and / or the sintered product, a processing container and / or jig having an aluminum diffusion coating layer formed on the surface is used, and after the water vapor treatment, the processing container and / or the jig is used. The gas soft nitriding treatment is performed without replacement.

  Such a method for treating a sintered product according to the present invention includes, as a preferred embodiment, one in which the aluminum diffusion coating layer has an aluminum concentration of 15 to 40% by weight on the outermost surface.

  In such a method for treating a sintered product according to the present invention, as a preferred embodiment, the processing container for accommodating the sintered product and / or the jig for supporting the sintered product is made of ordinary steel, special steel, or austenitic stainless steel. It is made of a metal material selected from steel, and the aluminum diffusion coating layer on the surface thereof is formed by aluminum diffusion permeation treatment.

  In the method for processing a sintered product according to the present invention, an aluminum diffusion coating layer is formed on the surface of a metal member such as a container or a jig that contains and / or supports the sintered product, thereby Generation of iron oxide on the surface can be prevented (first effect).

  Furthermore, since a dense and extremely thin alumina coating is formed on the outermost surface of the aluminum diffusion coating layer such as a container or jig by steam treatment, the ingress of nitrogen is suppressed. It is prevented that metal materials such as these containers and jigs are nitrided. Thereby, the lifetime of containers, jigs, etc. can be extended (second effect).

  From this, it becomes possible to carry out the gas soft nitriding without changing the sintered product after the steam treatment from the containers and jigs (third effect).

  Since the nitriding gas used for the gas soft nitriding process is not consumed for nitriding containers and jigs, it is effectively used for gas soft nitriding of sintered products. In addition, the gas soft nitriding treatment of the sintered product is improved in stability, so that the properties of the nitrided layer, the layer thickness are stabilized, and the quality is improved (fourth effect).

  As a result, it is possible to improve productivity, save labor, improve quality, and reduce consumables.

1 is a cross-sectional microscopic view of a test piece of SUS304 material of the present invention in Example 1. FIG. 1 is a cross-sectional microscopic view of a test piece of SCH 13 material of the present invention in Example 1. FIG. The graph which shows the analytical value of the X-ray microanalyzer (EPMA) of the aluminum before the test of the aluminum diffusion coating layer of the test piece of the SUS304 material of this invention in Example 1. FIG. The graph which shows the EPMA analysis value of the aluminum before the test of the aluminum diffusion coating layer of the test piece of SCH13 material of this invention in Example 1. FIG. In Example 1, the cross-sectional microscopic view of SUS304 material after one time of water vapor | steam processing. In Example 1, the cross-sectional inspection of the SUS304 material after 50 times of water vapor | steam processes. In Example 1, the cross-sectional microscopic view of SCH13 material after one time of water vapor | steam processing. In Example 1, the cross-sectional microscopic view of SCH13 material after 50 times of water vapor | steam processes. In Example 1, the cross-sectional EPMA analysis value of the SUS304 material after 50 times of water vapor treatments. In Example 1, the graph which shows the EPMA analysis value of aluminum and nitrogen of the aluminum diffusion coating layer of the test piece of SUS304 material of the present invention in which the gas soft nitriding treatment was repeated 50 times after the water vapor treatment 50 times. In Example 1, the graph which shows the EPMA analysis value of aluminum and nitrogen of the aluminum diffusion coating layer of the test piece of the SCH13 material of the present invention in which the gas soft nitriding was repeated 50 times after performing the steam treatment 50 times. FIG. 5 is a conceptual diagram of a sintered product filling basket (mesh basket) and support columns used in Example 2;

<Method of processing sintered product>
The present inventors can prevent the formation of iron oxide on the surface of the metal member in the water vapor treatment step, and if the member is not nitrided in the gas soft nitriding treatment in the next step, these members are subjected to gas soft nitriding treatment. As a result of various studies paying attention to the fact that it does not become a hindering factor, it is possible to prevent the formation of iron oxide in the water vapor treatment process by forming an aluminum diffusion coating layer on the surface of these members, and also to prevent nitriding in the next process. Obtained knowledge.

  The method for treating a sintered product according to the present invention is a method for treating a sintered product by performing steam treatment on the sintered product and then subjecting the sintered product to gas soft nitriding, and a processing container for housing the sintered product and / or As a jig for supporting the sintered product, a processing container and / or jig having an aluminum diffusion coating layer formed on the surface thereof is used, and the processing container and / or jig is replaced after the steam treatment. And performing the gas soft nitriding treatment.

  Here, in the present invention, the “processing container for storing the sintered product” is a container for storing all or a part of the sintered product to be processed in the steam treatment and gas soft nitriding treatment, At least a part of the container is configured to be permeable to the gas used in the water vapor treatment or gas soft nitriding treatment, and at least a part of the surface of the sintered product to be treated is brought into contact with water vapor or the gas. A container configured to be able to.

  In the present invention, the “jig for supporting a sintered product” refers to supporting a sintered product subjected to the treatment during the steam treatment and gas soft nitriding treatment, and maintaining its position and posture. Says a tool that can be stabilized. This jig is not limited to a jig that directly contacts a sintered product to be processed. For example, including the jig (primary jig) that is in direct contact with the sintered product to be processed, the above-mentioned “processing vessel for containing the sintered product” or the jig that is in direct contact with the sintered product (primary By holding or stabilizing the position and orientation of the jig), as a result, the jig that does not directly contact the sintered product that contributes to maintaining and stabilizing the position and orientation of the sintered product (secondary jig) Etc. are also included. For example, a column or the like that supports one or a plurality of the above-mentioned “processing containers containing sintered products” is a specific example of this “jig for supporting sintered products”.

  As a particularly preferred specific example of the “processing container for containing a sintered product” in the present invention, an outer diameter formed by a metal wire having a wire diameter of 1.0 to 4.0 mm, preferably 1.5 to 2.5 mm. Mention may be made of a net cage of 300 to 900 mm, preferably 500 to 700 mm, and a depth of 100 to 400 mm, preferably 200 to 300 mm.

  A particularly preferable specific example of the “jig for supporting a sintered product” in the present invention includes a three-point holding jig for the purpose of preventing warpage.

  The “processing container for storing a sintered product” and the “jig for supporting a sintered product” in the present invention have been conventionally employed in the case of “steam treatment” or “gas soft nitriding” for a sintered product. Like the “processing vessel” or “jig”, it can be made of metal materials such as ordinary steel, special steel, and austenitic stainless steel, but an aluminum diffusion coating layer is formed on the surface of these metal materials. In this respect, it is clearly different from the conventional general “processing vessel for containing a sintered product” or “jig for supporting a sintered product”.

  In the “processing container for storing a sintered product” and “jig for supporting a sintered product” in the present invention, an aluminum diffusion coating layer is always formed on all surfaces of the “container” and “jig”. Although not necessarily required, an aluminum diffusion coating layer is preferably formed on at least the surface with which the nitriding gas may come into contact.

  In the present invention, the “processing container for storing a sintered product” and the “jig for supporting a sintered product” are repeatedly used in a series of processing methods for a sintered product in which gas soft nitriding is performed after steam treatment. can do. Further, when only the steam treatment is repeatedly performed, it can be repeatedly used for the gas soft nitriding treatment after being used at least once for the steam treatment.

<Aluminum diffusion coating layer>
The high temperature oxidation resistance of the aluminum diffusion coating layer formed on the surface of the metal material is particularly remarkable in the high temperature red hot region exceeding 800 ° C. The mechanism by which the aluminum diffusion coating layer exhibits high oxidation resistance is that, when heated to the red heat region in the atmosphere, the aluminum contained in the aluminum diffusion coating layer preferentially bonds with oxygen in the air, and the melting point is 2050 ° C. It is now analyzed that it is extremely high and a dense aluminum oxide film (alumina = Al ₂ O ₃ ) film rich in corrosion resistance is formed to block oxygen and suppress subsequent oxidation.

  As described above, the “processing vessel for storing a sintered product” and the “jig for supporting a sintered product” in the present invention are conventionally used for “steaming” or “gas soft nitriding” for a sintered product. Similarly to the “processing vessel” or “jig” that has been employed in the present invention, it can be made of a metal material such as ordinary steel, special steel, or austenitic stainless steel. In the present invention, metal materials such as conventionally known ordinary steel, special steel, and austenitic stainless steel can be used as long as an aluminum diffusion coating layer can be formed on the surface thereof. Particularly preferable metal materials in the present invention include austenitic stainless steel, for example, SUS304 material, SCH13 material, SUS316 (L) material, SUS309 material, SUS310S material, SCH21 material and the like as defined in JIS standards. Among these, SUS304 material and SCH13 material are particularly preferable.

  Examples of the method for forming the aluminum diffusion coating layer on the surface of the metal material include an aluminum diffusion permeation treatment using a mixed powder containing iron-aluminum alloy powder, alumina powder and ammonium chloride powder.

  In the present invention, particularly preferable aluminum diffusion and penetration treatment is, for example, 10 to 90 wt% (preferably 30 to 80 wt%) of iron-aluminum alloy powder having an aluminum concentration of 20 to 60 wt% (preferably 30 to 55 wt%). ), Alumina powder 10 to 90% by weight (preferably 30 to 60% by weight) and ammonium chloride powder 0.1 to 3.0% by weight (preferably 0.2 to 1.5% by weight) A powder is used as a penetrant, a metal material is embedded in the penetrant, and the temperature is raised to 800 to 1100 ° C. (preferably 850 to 1050 ° C.) in a reducing atmosphere such as an inert gas (preferably Ar) or hydrogen. A method of heating and heating for 5 to 20 hours (preferably, 10 to 20 hours) can be given.

  According to this aluminum diffusion penetration treatment, an aluminum diffusion coating layer having an aluminum concentration of 15 to 40% and a thickness of 20 to 800 μm can be easily formed on the surface of the metal material. The aluminum concentration on the surface of the metal material is preferably 20 to 40%, particularly preferably 25 to 40%. If the aluminum concentration is less than 15%, there is a problem in durability. On the other hand, if it exceeds 40%, it becomes too hard and brittle, and cracking and peeling are liable to occur, and this is not preferable. In addition, when the thickness of the aluminum diffusion coating layer is less than 20 μm, it is too thin and there is a problem in durability. On the other hand, when it exceeds 800 μm, the coating layer is too thick and becomes brittle, so cracking or peeling due to thermal shock This is not preferable because it easily occurs and cannot be practically used. Here, the “aluminum concentration” of the aluminum diffusion coating layer is obtained by quantitative analysis of an EPMA apparatus, and the thickness of the aluminum diffusion coating layer is obtained by an optical microscope.

  The specific conditions in the aluminum diffusion permeation treatment can be appropriately determined in consideration of the component composition of the metal material, the thickness of the coating layer, the aluminum concentration, and the like.

  As another treatment method, aluminum powder is used in place of the iron-aluminum alloy powder used in the aluminum diffusion permeation treatment, and alumina powder and ammonium chloride powder are mixed into this to form a permeation agent. A method of heating at ℃ (preferably 700 to 850 ° C.), a metal material is immersed in molten aluminum at 670 to 720 ° C. (preferably 680 to 710 ° C.) to form a pure aluminum film on the surface, and separately There is a method of heating to 900 to 1000 ° C. (preferably, 920 to 980 ° C.) in a heating furnace to diffuse aluminum on the surface inside the material to form an aluminum diffusion coating layer. In either case, an aluminum diffusion coating layer, that is, an aluminum alloy layer can be formed on the surface.

<Steam treatment (homo treatment)>
In the present invention, “steam treatment” refers to surface oxidation treatment using steam. For example, in a state where the sintered product subjected to the steam treatment is accommodated in the processing container in which the aluminum diffusion coating layer is formed, or is supported by a jig in which the aluminum diffusion coating layer is formed, Water vapor at 400 to 600 ° C. (particularly preferably 450 to 550 ° C.) under a pressure of 0 to 1 kg / cm ² (particularly preferably 0.4 to 0.7 kg / cm ² ) for 30 to 300 minutes (particularly The treatment for holding (preferably 60 to 240 minutes) corresponds to the “water vapor treatment” of the present invention.

  In the case of steam treatment (homo treatment), the temperature is about 500 ° C. and a relatively low temperature steam atmosphere compared to high-temperature oxidation exceeding 800 ° C. in the atmosphere, but as a result of various experiments, containers, jigs, Regarding metal members such as gas rectifying members, it has been found that the formation of iron oxide can be prevented by forming an aluminum diffusion coating layer on the surface of any material of ordinary steel, special steel, and stainless steel. That is, the aluminum in the aluminum diffusion coating layer is preferentially oxidized by high-temperature water vapor to form an alumina film, whereby the reaction between high-temperature water vapor and iron in the coating layer can be suppressed, and iron oxide is generated. It was confirmed that it can be prevented. Here, ordinary steel refers to carbon steel including general structural rolled steel (SS), and special steel refers to steel including alloy elements such as Ni and Cr.

  Alumina on the surface produced by the steam treatment (homo treatment) does not adhere to or be baked on the surface of the sintered product, and does not adversely affect the surface properties of the sintered product.

<Gas soft nitriding>
In the present invention, "gas soft nitriding" refers to supplying nitrogen and carbon by treating mainly in a mixed atmosphere of carburizing gas and nitriding gas for the purpose of improving fatigue strength and improving wear resistance. It refers to a process of forming carbonitride by simultaneously invading and diffusing nitrogen and carbon on the surface of a component in contact with the mixed gas. As the carburizing gas used in the gas soft nitriding, for example, a carburizing gas (CO gas) such as a rapid thermal modified gas (Endo gas) or a pyrolysis gas of an organic solvent is used. Further, as the nitriding gas, for example, NH ₃ gas or the like is used. For example, in a state where the sintered product subjected to the steam treatment is accommodated in the processing container used for the steam treatment or supported by a jig used for the steam treatment, in the mixed gas atmosphere, The treatment for holding at a temperature of 500 to 650 ° C. (particularly preferably 550 to 580 ° C.) and atmospheric pressure for 30 to 240 minutes (particularly preferably 60 to 180 minutes) is referred to as “gas soft nitriding treatment” in the present invention. Applicable.

  In the present invention, since the alumina coating formed on the surface of the container or jig suppresses the ingress of nitrogen, the container or jig is not nitrided. For this reason, gas soft nitriding can be performed as it is without replacing the sintered product from the container or jig.

  Therefore, all the nitriding gas is not only effectively used for gas soft nitriding of sintered products, but also the surface properties of containers and jigs that are not nitrided are almost the same as in the unused state, and nitriding is repeated as before. As a result, the life of the container and jigs can be dramatically increased and the cost of consumables can be reduced significantly.

  When the sintered product is removed from the container and jig after the gas soft nitriding is completed, the surface of the sintered product is maintained in a normal state without being seized. Even if the alumina film is partially rubbed and peeled off during use, the alumina film is formed again in the next water vapor treatment (homo treatment). The prevention effect lasts.

<Example 1>
In order to confirm that the product of the present invention does not produce iron oxide by steam treatment and is not nitrided by subsequent gas soft nitriding treatment, JIS standard SUS304 material, which is a representative metal material used for jigs and containers The test piece of the present invention obtained by subjecting the SCH 13 material to aluminum diffusion permeation treatment and the untreated material (raw material) of the same size are repeatedly subjected to steam treatment and gas soft nitriding treatment together with the sintered product. The change of surface condition was investigated.

1) Test piece Material: SUS304, SCH13 Dimension: 50mm x 50mm x thickness 5mm
Number of sheets: 4 each

2) Aluminum diffusion treatment a. Composition of penetrant Iron-aluminum (50% by weight) alloy powder: 65% by weight
Alumina powder: 34% by weight
Ammonium chloride powder: 1.0% by weight
b. Processing temperature: 1000 ° C
c. Processing time: 15 hours

3) Surface characteristics of the test piece of the present invention Table 1 shows the results of investigating the aluminum diffusion coating layer by cutting each one of the test pieces subjected to the aluminum diffusion treatment. The thickness of the diffusion coating layer was measured by cross-sectional microscopy, and cross-sectional micrographs are shown in FIGS. Analytical values of the aluminum concentration in the cross section by EPMA (X-ray microanalyzer) are shown in FIGS.

4) Steam treatment Among the test pieces of the present invention that have been subjected to aluminum diffusion permeation treatment, 3 SUS304 materials, 3 SCH13 materials, 2 untreated materials each, and a filled container when steaming a sintered product And the treatment was repeated once and repeated 50 times as shown in Table 2. One steam treatment was performed by heating in steam at 500 ° C. for 2 hours.
Then, each test piece was cut | disconnected, the cross-sectional state of the surface was examined, and the result of having measured the thickness of the iron oxide production | generation layer is shown in Table 2.

  Next, cross-sectional micrographs of untreated products are shown in FIGS. The hatched portion in the figure is an iron oxide generation layer. As a typical example, the result of EPMA analysis of the cross-sectional microscopic portion of FIG. 6 is shown in FIG. As is apparent from FIG. 9, the surface layer portion contains a large amount of iron and oxygen, and it was confirmed that iron oxide was generated.

Next, as a result of cross-sectional inspection of the test piece of the present invention product, there was no significant difference from FIGS. 1 and 2 before the steam treatment, and the iron oxide-containing layer generated in the untreated product could not be confirmed.

  As described above, generation of iron oxide was not observed on the surface of the test piece of the present invention in either case of SUS304 material or SCH13 material, and the first effect of the present invention could be confirmed.

5) Gas soft nitriding treatment Each remaining one of the test pieces of the present invention which was subjected to the steam treatment experiment 50 times was put together in a filling container when the sintered product was subjected to gas soft nitriding, and gas soft nitriding was repeated 50 times. It was. One gas soft nitriding was performed by heating to 570 ° C. for 90 minutes in an atmosphere in which urea was thermally decomposed.
Thereafter, each test piece was cut and the cross section of the aluminum diffusion coating layer was examined. As a result, the thickness of the coating layer was not significantly different from that in FIGS.

  Next, the results of EPMA analysis of aluminum and nitrogen in the coating layer are shown in FIGS. As is clear from the figure, almost no nitrogen was detected in the aluminum diffusion coating layer and in the nearby base material (in the material) in either the SUS304 material or the SCH13 material, and the aluminum concentration on the surface and the concentration gradient of aluminum were as follows: There was no significant difference from FIGS. 3 and 4 before the steam treatment and the gas softening treatment. Thus, the second effect of the present invention could be confirmed.

<Example 2>
In order to confirm the effect of the present invention with an actual machine, an aluminum diffusion penetration treatment was applied to a sintered product filling member composed of a basket (mesh cage) and a support shown in FIG.

  All the materials are SUS304 materials. The outer diameter of the net cage is 600 mm, the depth is about 200 mm, and the wire diameter is 1.6 mm. The fine basket is filled with about 15 to 30 kg of a sintered product, and is arranged at intervals so that water vapor and soft nitriding gas are sufficiently dispersed.

  Aluminum diffusion penetration treatment was performed under the same conditions as in Example 1 to obtain an aluminum diffusion coating layer having an aluminum concentration of 31% and a thickness of 220 μm on the surface.

  One gas soft nitriding treatment consisting of heating the sintered body to 570 ° C. for 90 minutes in an atmosphere in which urea is thermally decomposed after one steam treatment comprising heating the sintered body in water vapor at 500 ° C. for 2 hours. The process to perform was made into 1 cycle, and this was implemented 50 cycles.

  After 50 cycles, the mesh cage was cut and the cross section of the line was examined to perform EPMA analysis. As a result, no iron oxide was observed on the surface, the aluminum concentration on the surface of the aluminum diffusion coating layer was 30.5%, the thickness of the coating layer was 222 μm, and there was almost no change from before the test, and nitrogen was detected. I could not do it. Also, there was no change on the basket surface that would lead to material deterioration such as cracks and scratches.

  The conventional basket using the untreated material (raw material) is cracked when the nitriding treatment is repeated about 200 times and cannot be used due to deformation, whereas in the case of the product of the present invention obtained in Example 2, it is 200. Although there is some thermal deformation after repeated use, no clear cracks are observed. Thereafter, there was no problem in practical use even after continuous use 1000 times.

  Thus, according to the present invention, there is no need to take out the sintered product from the basket and replace it with a new basket, and the steam treatment and gas soft nitriding treatment can be carried out continuously, so that the operating rate of the processing furnace is increased. Productivity is improved, and scratches and chipping of products that occur when handling sintered products are reduced, which is effective not only for cost reduction but also for quality improvement.

<Effect of the invention>
As described above, the metal member such as a sintered product filled container and jig of the present invention not only prevents the formation of iron oxide but also prevents nitridation and sintering when used for steam treatment and gas soft nitriding treatment. The economic effect is very remarkable because it can improve the gas soft nitriding work of the product, improve the productivity, improve the quality, and extend the life of the container and jigs.

1, 2, Aluminum diffusion coating layer 3, 9, 10 Base material (SUS304 material)
4, 11, 12 Base material (SCH13 material)
5, 6, 7, 8 Iron oxide generation layer 13 Prop 14, 15, 16 Mesh basket

Claims (3)

A method for treating a sintered product that performs steam treatment on a sintered product and then gas nitrocarburizing,
A processing container and / or jig having an aluminum diffusion coating layer formed on the surface is used as a processing container for storing the sintered product and / or a jig for supporting the sintered product, and after the steam treatment, the processing container is used. And / or performing the gas soft nitriding treatment without replacing the jig.   The said aluminum diffusion coating layer is a processing method of the sintered article of Claim 1 whose aluminum concentration of the outermost surface is 15 to 40 weight%.   The processing container for storing the sintered product and / or the jig for supporting the sintered product is made of a metal material selected from ordinary steel, special steel, and austenitic stainless steel, and an aluminum diffusion coating layer on the surface thereof. The processing method of the sintered article according to claim 1 or 2 formed by aluminum diffusion penetration treatment.

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