JP2010185137A - Method for producing sintered sheet material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method where many pieces of sintered sheet materials are produced from a sintered compact obtained by single HIP treatment, by which the loss of raw materials is reduced, and simultaneously, sintered sheet materials having high sintered density are efficiently produced. <P>SOLUTION: In the method for producing sintered sheet materials, a packed bed of raw material powder and a spacer with a relative density of 50 to 85% partitioning the packed bed are alternately arranged at the inside of a pressure vessel; thereafter, hot hydrostatic press treatment is performed to the pressure vessel so as to obtain a sintered compact, and the spacer part of the sintered compact is cut away so as to obtain a plurality of sintered sheet materials. Further, it is particularly effective when a high melting point metal having a melting point higher than that of iron is used as the raw material powder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a sintered plate material, in which a large number of sintered plate materials are obtained by a single hot isostatic pressing process.

Hot isostatic pressing (hereinafter abbreviated as HIP) treatment forms a high-pressure environment by heating the pressurized space to a specific temperature, and the treated product placed in the pressurized space is pressurized and isotropic at the specified temperature. It is a technology that applies a large pressure.
There are various applications of the HIP treatment, and an example of its use is application to a sintering process in powder metallurgy. Specifically, after filling the sintering powder for compaction such as soft iron or stainless steel with raw material powder, the inside of the container is deaerated and sealed, and this is pressure sintered in the pressure space in the HIP device. To do. According to this method, a uniform and fine structure can be obtained, and a high melting point metal material that is difficult to manufacture by a melting method can be obtained.

Further, as a method for efficiently obtaining a sintered body having a desired size by HIP treatment, a method for obtaining a large number of sintered plate materials by cutting the sintered body obtained by one HIP treatment has been proposed (for example, patents). Reference 1).
Also proposed is a method of forming a preform of raw material powder, laminating the preforms in a sintering container via a spacer, and then performing HIP treatment to obtain a large number of sintered plate materials by one HIP treatment. (For example, refer to Patent Document 2).

JP-A-2005-113188 JP-A-63-290272

The method disclosed in Patent Document 1 is preferable from the viewpoint of production efficiency because a large number of sintered plate materials can be obtained at one time. However, in the method described in Patent Document 1, when a sintered body is cut to produce a plurality of sintered plate materials, a cutting margin is generated and the portion is removed, so that the product yield is low. Not desirable. In particular, when an expensive high-melting-point metal material is used as a raw material for the sintered plate material, the generation of a portion for removing the cutting margin becomes a serious problem in terms of cost.
In addition, the method disclosed in Patent Document 2 is an excellent method in which a large number of sintered plate materials can be obtained at a time by stacking the preforms via spacers and performing HIP treatment. However, it has been confirmed that when the HIP process is performed by laminating via a spacer, the sintered density may not increase at a part of the sintered plate material.

  In view of the above problems, an object of the present invention is to produce a large number of sintered plate materials from a sintered body obtained by a single HIP process. It is to provide a method for producing efficiently.

  The inventors of the present invention have configured the cut portion in the sintered body obtained by the HIP treatment as a spacer having a relative density similar to that of the raw material powder in a pressurized container before the HIP treatment. By cutting and removing the spacer portion, it was found that a large number of sintered plate materials with reduced sintering loss and high dispersion were obtained, and the present invention was achieved.

  That is, according to the present invention, a packed bed of raw material powder and spacers having a relative density of 50 to 85% partitioning the packed bed are alternately arranged in the sintered container, and then subjected to a hot isostatic pressing process on the sintered container. Thus, a sintered body is obtained, and a spacer portion of the sintered body is cut and removed to obtain a plurality of sintered sheets.

  In the present invention, it is particularly effective when a refractory metal having a higher melting point than iron is used as the raw material powder.

  According to the present invention, since loss of raw materials can be reduced when a sintered body is cut to obtain a plurality of sintered plate materials, it is an indispensable technique as a method for obtaining an expensive metal material sintered plate material. .

It is a schematic diagram which shows an example of the filling method of the raw material powder and spacer of this invention. It is a schematic diagram which shows an example of the filling method of the raw material powder and spacer of this invention. It is a figure which shows the relative density of Mo sintered board, and the positional relationship of a pressurized container.

An important feature of the present invention is that the cutting part of the sintered body by HIP processing is composed of spacers, and the spacers as cutting margins are cut to reduce the cutting loss of raw materials when obtaining a plurality of sintered plate materials It is a point that I found out.
In addition, during the HIP process, a high pressure and isotropic pressure is applied to the HIP sintering container at a specific temperature. When the inventor alternately arranged the packing layer of the raw material powder and the spacer partitioning the packing layer in the sintering container and performed the HIP treatment, the packing density of the raw material powder into the sintering container and the relative density of the spacer When there is a large difference between the two, there is a problem that the sintering density at the central portion in the sintering container does not increase, and the sintering density with the vicinity of the wall surface in the sintering container varies. Therefore, in the present invention, the relative density of the spacers is controlled to 50 to 85%, which is substantially equal to the packing density of the raw material powder. Control of the relative density of the spacer is also an important feature in the present invention.

Hereinafter, further specific examples will be described.
FIG. 1 illustrates an example of a state in which a packed bed of raw material powders and spacers that partition the packed bed are alternately arranged in the sintering container of the present invention. First, as shown in FIG. 1 (a), a spacer 2 is installed in the sintering container 1, and as shown in FIG. 1 (b), the raw material powder 3 is placed in a space formed by the installed spacer and the sintering container. By filling, a packed layer is formed, and the raw material powder and the spacer are alternately arranged in the sintering container. Thereafter, as shown in FIG. 1C, the lid 4 with the deaeration holes 5 is welded to the sintering container, and the inside of the sintering container is deaerated from the deaeration holes to seal the deaeration holes. The sealed pressurized container is placed in the HIP apparatus and subjected to HIP treatment to obtain a sintered body. Since the obtained sintered body has a sintered portion of a raw material and a spacer portion, a plurality of sintered plate materials can be obtained by cutting and removing the spacer portion.
In addition, as shown in FIG. 2 which shows an example of the state which alternately arrange | positioned the filling layer of raw material powder and the spacer which partitions a filling layer in another sintering container, raw material powder is made into predetermined thickness in a sintering container. It is also possible to arrange the raw material powder and the spacer alternately by repeating the filling of the raw material powder on the spacer after the filling layer is formed so as to form the filling layer.

In the present invention, the setting of the relative density of the spacer is important. In the HIP treatment, pressure is applied to the treated material isotropically, but when the raw material powder and the spacer of another material are simultaneously subjected to the HIP treatment, there is a difference in the progress of sintering between the surface portion and the central portion. it is conceivable that. In particular, when the relative density of the spacer is higher than the relative density of the raw material powder arranged in the sintering container, a significant difference occurs in the progress of the sintering, and the relative density of the sintered body at the center does not increase.
Therefore, it is important to perform the HIP treatment by making the packing density of the raw material powder to be filled in the pressurized container substantially the same as the relative density of the spacer in order to suppress the density variation of the sintered body. The packing density of the raw material powder varies depending on its composition and the shape and particle size of the raw material powder. However, since the packing density of the raw material powder into the pressurized container is about 50 to 85%, the relative density range of the spacer is also 50 to 50%. 85%. In addition, the relative density of a spacer means the density represented by the relative ratio of the density measured by Archimedes method, and the theoretical density of a spacer raw material, and is represented by relative density (%) = 100x measured density / theoretical density.

  The raw material powder to be arranged in the sintering vessel may be set so that a desired shape is obtained after sintering by HIP treatment, and can be determined by calculating the amount of shrinkage from the packing density of the raw material powder. Further, since the spacer also has a relative density of 50 to 85%, it is necessary to set the shape in consideration of the shrinkage after sintering. In addition, since the spacer is cut and removed after the HIP process, it is desirable to make the spacer larger than the width of the cutting tool in order to reduce the cutting loss of the raw material.

The HIP process is an advantageous sintering process that can sinter the raw material powder at a high density by generating a high pressure within a possible range at a temperature at which the sintering container does not melt. As the material of the sintering container, materials such as soft iron SPCC and stainless steel can be applied. If these iron base materials are applied, a temperature of about 1000 ° C. to 1400 ° C., a pressure of 50 to 150 MPa, 0.5 A holding time of -10 h is often used.
Under these conditions, a sintered body having a relative density of 98% or more can be obtained using, for example, refractory metal Mo or W having a melting point higher than that of iron as raw material powder. It is also possible to make a sintered body of an alloy that is mainly composed of the above-mentioned refractory metal and is mixed and filled with a powder of a plurality of elements made of a refractory metal such as Ti, Nb, Zr and the like. .

  Further, as a method for cutting and removing the spacer portion of the sintered body obtained by the HIP process, there are wire electric discharge machining and saw cutting, and it is preferable to select appropriately according to the material of the spacer.

The spacer of the present invention is disposed in the sintering container together with the raw material powder and subjected to HIP processing. Further, it is cut and removed after the HIP process. Therefore, the material of the spacer needs to be less expensive than the raw material powder without melting under the high temperature and high pressure of the HIP process. Examples of such a material include Fe, Cu, Cr, and alloys mainly composed of these. Since these elements are relatively inexpensive, they are suitable materials as spacers.
Moreover, when the raw material powder and the spacer react during sintering by HIP treatment, the spacer may be covered with a metal foil. Examples of the metal foil include stainless steel foil and Nb foil. The material may be appropriately selected in consideration of the reactivity with the raw material powder and the melting point of the metal foil. In particular, since the Nb foil absorbs oxygen in the raw material powder, it is suitable for producing a sintered body having a low oxygen concentration.

Moreover, as a spacer, it is possible to partition the packed layer of raw material powder in a sintering container, and it is applicable if the relative density is 50 to 85%. For example, a porous plate material having a desired relative density partially having voids, a plate material obtained by compression molding a powder material to a desired relative density, or a sintered plate material can be applied.
In addition, the manufacturing method of a spacer is applicable if it is a method by which a spacer with a relative density of 50 to 85% is obtained. For example, there is a method in which a powder as a raw material of the spacer is made into a sintered body having a desired relative density, such as a plate, by HIP or hot press in which the sintering time and the sintering temperature are adjusted. As another method, the raw material powder of the spacer may be cold-molded to form a plate or the like having a desired relative density.

  Fe powder is filled in a cemented carbide die, cold pressed under the conditions of each pressurizing pressure shown in Table 1 to produce a Fe compact, and cut and machined to 145.5 × 5.6. A spacer of × 158 (mm) was obtained, and the relative density of the produced spacer was measured by the Archimedes method.

  Also, Fe powder can be filled in a sintered vessel made of mild steel and subjected to pressure sintering by hot isostatic pressing (HIP) under the conditions of each pressure, heating temperature and holding time shown in Table 2. The Fe sintered body was cut and machined to obtain a spacer of 145.5 × 5.6 × 158 (mm), and the relative density of the prepared spacer was measured by the Archimedes method.

Next, the maximum surface of the spacer (145.5 × 5.6 × 158 mm) of the sample 2 prepared above in the mild steel sintered container (145.5 × 145.5 × height 175 mm) is the bottom surface of the sintered container. As shown in FIG. 1, the Mo powder having a particle size distribution (d50) of 100 μm is used as a raw material powder in the space formed by the spacer and the sintering vessel (at intervals of 8.4 mm). Filled. At this time, the packing density of the Mo raw material powder was 59%.
Further, the spacers of Samples 3 and 4 were also placed in the sintering container in the same manner as described above, and filled with Mo powder having the same particle size distribution. The packing density of any Mo raw material powder was 59%.
In addition, the spacer of the sample 1 had a low relative density, and it was difficult to hold | maintain a shape, and could not be used as a spacer.

  Next, a lid is welded to each sintering vessel in which the Mo raw material powder and the spacer are alternately arranged as shown in FIG. Stopped. The sealed sintered container was placed in a HIP apparatus, and subjected to HIP treatment under a pressure of 140 MPa, a heating temperature of 1250 ° C., and a holding time of 5 hours to obtain a sintered body. The spacer part of the obtained sintered body was cut and removed with a saw cutter and divided into 10 pieces, and each surface was subjected to machining by grinding to obtain a Mo sintered plate material of 110 × 120 × 5 (mm). . The relative density was calculated by measuring the density of each of the 10 sintered Mo plates produced by the Archimedes method. FIG. 3 shows the relationship between the position in the sintering container and the relative density for the calculated relative density result.

  As a comparative example, the same as above except that a spacer (sample 5) made of SPCC (JIS G3141 cold rolled steel sheet) having a relative density of 100% × 158 × 5.6 (mm) is used. Under the conditions, spacers and Mo raw material powder were alternately arranged in the sintering container, and subjected to HIP treatment to obtain a sintered body. The packing density of the Mo raw material powder was 59%. The spacer portion of the obtained sintered body was cut and removed with a saw cutter and divided into 10 pieces, and each surface was subjected to grinding machining to obtain a 110 × 120 × 5 (mm) Mo sintered plate material. The relative density was calculated by measuring the density of 10 Mo sintered sheets produced by the Archimedes method. FIG. 3 shows the relationship between the position in the sintering container and the relative density for the calculated relative density result.

  From FIG. 3, when the spacers of Samples 2 to 4 are used, it can be confirmed that the obtained sintered plate material can realize a relative density of 98% or more regardless of the position in the sintering container. On the other hand, when the spacer of the sample 5 having a high relative density is used, the relative density decreases as it reaches the central part of the pressurized container, and the relative density of the sintered plate material in the central part is less than 98%. I understand.

1. 1. sintering container; Spacer, 3. Raw material powder, 4. Lid, 5. Deaeration

Claims (2)

  After alternately placing a packed bed of raw material powder and spacers having a relative density of 50 to 85% in the sintered container to partition the packed bed, the sintered container is subjected to hot isostatic pressing to obtain a sintered body. A method for producing a sintered plate material comprising obtaining a plurality of sintered plate materials by cutting and removing the spacer portion of the sintered body.   The method for producing a sintered plate material according to claim 1, wherein a refractory metal having a melting point higher than that of iron is used as the raw material powder.