Sintered body and method for manufacturing a sintered body

Abstract

This invention provides a method for producing a sintered body by accurately measuring the temperature of an unsintered body, and also provides a sintered body produced by the same method. [Solution] The sintered body 1 is obtained by sintering an unsintered body 1p having a cone-shaped or V-shaped recess 12 on its surface 11s. The method for producing the sintered body includes the steps of: forming an unsintered body 1p having a cone-shaped or V-shaped recess 12 on its surface 11s; and measuring the temperature of the apex 12t of the recess 12 of the formed unsintered body 1p using a radiation thermometer from the bottom side of the recess 12. The method for producing the sintered body includes the step of heating the unsintered body 1p based on the measured temperature to produce the sintered body 1.

Description

Technical Field

[0001] The present disclosure relates to a sintered body and a method for producing a sintered body.

Background Art

[0002] Patent Document 1 describes a sintering method by HIP in which a raw material powder body is heated and held at a first temperature lower than the sintering temperature until the entire raw material powder body reaches a substantially uniform temperature, and then sintering is performed while applying pressure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, it is necessary to measure the temperature of the surface of the raw material powder body, which is an unsintered body, with a radiation thermometer such as an infrared thermometer. However, particularly when the unsintered body is a metal with a high reflectivity, it may not be possible to accurately measure the temperature depending on the unsintered body. Therefore, there is a demand for the development of a technique for accurately measuring the temperature of an unsintered body and producing a sintered body.

Means for Solving the Problems

[0005] The sintered body according to the present disclosure is obtained by sintering an unsintered body having a concave portion with a conical shape or a V-shaped groove on its surface.

[0006] The method for producing a sintered body according to the present disclosure includes a step of forming an unsintered body having a concave portion with a conical shape or a V-shaped groove on its surface, a step of measuring the temperature of the apex of the concave portion with a radiation thermometer from the bottom surface side of the concave portion of the formed unsintered body, and a step of heating the unsintered body based on the measured temperature to produce a sintered body.

Effects of the Invention

[0007] According to this disclosure, a method for producing a sintered body and a sintered body can be provided that enable the accurate measurement of the temperature of the unsintered body. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic transmission perspective view showing a first example of the configuration of a sintered body according to an embodiment. [Figure 2] This is a schematic transmission perspective view showing a second example of the configuration of a sintered body according to the embodiment. [Figure 3] This is a schematic transmission perspective view showing a third example of the sintered body according to the embodiment. [Figure 4] This is a schematic transmission perspective view showing a fourth example of the sintered body according to the embodiment. [Figure 5] This is a schematic top view showing a fifth configuration example of the sintered body according to the embodiment. [Figure 6] This is a flowchart illustrating an example of a sintered body manufacturing method according to an embodiment. [Modes for carrying out the invention]

[0009] The present invention will be described below through embodiments of the invention, but the invention as claimed is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential as means for solving the problem.

[0010] (Embodiment) A first example of the sintered body according to this embodiment will be described using Figure 1. Figure 1 is a schematic transmission perspective view showing this first example of the configuration.

[0011] The sintered body 1 in the first example shown in Figure 1 is obtained by sintering an unsintered body 1p. Note that in Figure 1, the sintered body 1 and the unsintered body 1p are shown as the same entity because they have similar structures. Furthermore, for convenience, the same reference numerals are used to indicate and describe the components of both the sintered body 1 and the unsintered body 1p. The unsintered body may also be called a pre-sintered body.

[0012] The material of the unsintered body 1p can be a metal, a nonmetal, or a mixture of metals and nonmetals. In other words, the unsintered body 1p may be an unsintered body made of a metal element, or an unsintered ceramic body made of a nonmetal element or a mixture of metals and nonmetals. The unsintered body 1p can be formed by molding the material powder, and a binder and lubricant may be added as needed. The lubricant is not limited to oil-based lubricants, but may also be a soap-based lubricant or a synthetic lubricant. Furthermore, the material may be recycled material such as cutting sludge. The sintered body 1 produced by sintering may be aluminum, iron, gold, silver, copper, platinum, or alloys thereof.

[0013] In particular, the sintered body 1 is obtained by sintering an unsintered body 1p having a conical recess 12 on the surface 11s of its main body 11. The recess 12 may also be called a concave part. Examples are given where the unsintered body 1p and the main body 11 of the sintered body 1 have a cylindrical shape. Since the sintered body 1 is made by sintering such an unsintered body 1p, it is different from a sintered body in which a recess of the same shape as the recess 12 is engraved after sintering using a carving knife or laser engraving machine, or a sintered body in which a recess of the same shape as the recess 12 is formed by pressing. Of course, other recesses may be formed in the sintered body 1 after it has been manufactured by engraving or pressing. Furthermore, the unsintered body 1p and the sintered body 1 may have other recesses or protrusions that do not satisfy the condition of a conical shape in the recess 12.

[0014] As will be described later in the sintered body manufacturing method, this recess 12 is formed from the unsintered body stage and is a recess provided to measure the temperature used for temperature control during the sintering process at the apex 12t of this recess 12. In other words, this recess 12 is a recess for measuring the temperature during sintering, and the sintered body 1 is a sintered body obtained by sintering an unsintered body 1p having this recess 12 based on the temperature at the apex 12t of the recess 12. Of course, the sintered body 1 may also have recesses other than the recess used for temperature control.

[0015] Temperature measurements are performed using a radiation thermometer. A radiation thermometer measures the temperature of a powder based on the emissivity of the powder material. Examples of radiation thermometers include infrared radiation thermometers, also known as infrared thermometers, and microwave thermometers.

[0016] The radiation thermometer measures the temperature by irradiating infrared radiation and microwaves towards the conical recess 12 of the unsintered body 1p in Figure 1, particularly towards its apex 12t. Although not shown, the radiation thermometer should be equipped with a sensor of approximately the same size as the opening on the surface 11s, located at the bottom of the cone-shaped recess 12, and irradiate the recess 12. As illustrated by the reference numeral 13 in Figure 1, infrared radiation and microwaves are absorbed toward the conical recess 12, and the reflectivity decreases at the apex 12t, approaching the absolute temperature. Therefore, the temperature of the unsintered body 1p can be accurately measured. This principle is also evident from the method used in blackbody furnaces and is based on Boltzmann's equation.

[0017] Especially when the green compact is made of a metal with a high reflectivity, accurate temperature measurement may not be possible depending on the green compact. However, in the green compact 1p according to the present embodiment, since it has a conical recess 12, the temperature of the green compact 1p can be accurately measured to produce the sintered body 1. That is, the present embodiment can be said to be useful for temperature measurement when the green compact 1p is made of a material with a high reflectivity. Of course, by providing such a recess 12, it is not necessary to measure the measurement target part such as the apex 12t and other parts with a contact thermometer, and it is also not necessary to install a thermocouple sensor at the measurement target part, so the productivity of the sintered body 1 can be improved. Further effects according to the present embodiment will be described in detail in the description of the method for producing the sintered body 1.

[0018] The sintered body 1 and the green compact 1p before sintering according to the first configuration example 1 are examples having a conical recess 12 on the surface 11s. However, such a recess is not limited to a conical shape, and may be a pyramidal shape or a V-shaped shape. A typical pyramidal shape other than the conical shape is a pyramidal shape. However, applicable pyramidal shapes may include those with an elliptical cross-section, those with a cross-section that is partly circular or elliptical and the rest is composed of straight lines, and the like.

[0019] The second to fifth configuration examples of the sintered body according to the present embodiment will be described with reference to FIGS. 2 to 5. FIGS. 2, 3, and 4 are perspective views showing the second, third, and fourth configuration examples schematically, respectively. FIG. 5 is a top view showing the fifth configuration example schematically. In any of the second to fifth configuration examples, for the sake of simplicity of explanation, only the differences from the first configuration example will be described. In FIGS. 2 to 5 as well as in FIG. 1, the sintered bodies 2, 3, 4, 5 and the green compacts 2p, 3p, 4p, 5p are shown as the same, respectively, and the components of the sintered body and the green compact are shown and described using the same reference numerals for convenience.

[0020] The sintered body 2 is obtained by sintering a green compact 2p having an octagonal pyramid-shaped recess 22 on the surface 21s of its main body 21. Although the absorption of infrared rays and the like by the recess 22 is not uniform compared to the conical recess 12 of Configuration Example 1, it can be said that the radiation thermometer can accurately measure the temperature of the main body 21 as the temperature at the apex 22t of the recess 22, compared to the case where the recess 22 is not provided. Note that the pyramid shape is not limited to the octagonal pyramid shape, and may be an n-sided pyramid where n is an integer of 3 or more.

[0021] The sintered body 3 is obtained by sintering a green compact 3p having a V-shaped recess 32 on the surface 31s of its main body 31. The recess 32 can also be referred to as a V-shaped groove or a V-notch. Note that the V shape can be said to be a shape in which a triangular prism is positioned with one side in the height direction at the lowest position. As can be seen from the shape of the recess 32, the apex of the recess 32 is not a single point but a straight line, that is, a portion represented by an apex group 32t. That is, in this example, the temperature of the apex group 32t corresponding to the apex of the recess 32 can be measured as the absolute temperature. Note that in FIG. 3, the recess 32 is provided only in the central portion of the surface 31s, but a V-shaped recess connecting both ends of the main body 31 may also be used.

[0022] The sintered body 4 is obtained by sintering a green compact 4p having a cylindrical recess 42 on the surface 41s of its main body 41, and is different from the sintered body 1 in that the shape of the main body 41 is a quadrangular prism. In this example, the temperature of the apex 42t of the recess 42 can be measured as the absolute temperature. As in these examples, the shape of the main body of the sintered body is not limited to a cylinder, and various shapes such as a quadrangular prism can be adopted, and the areas of its surface and bottom surface may be different.

[0023] The sintered body 5 is obtained by sintering a green compact 5p having a V-shaped recess 52 on the surface 51s of its main body 51. In this example, the main body 51 has a shape in which the area of the surface 51s and the bottom surface is different in the shape of a quadrangular prism, and has a trapezoidal shape when viewed from the side surface side. In this example, the temperature of the apex group 52t of the recess 52 can be measured as the absolute temperature.

[0024] In this example, a recess 52 and other recesses or protrusions are formed on the surface 51s of the main body 51, forming a string of characters 50 such as "Quality Assured." The recess 52 or the string of characters 50 may be, for example, a string of characters that guarantees the quality of the sintered body 5, or a string of characters that indicates the product name. At least a portion of the string of characters 50, excluding the recess 52, may not be present on the unsintered body 5p but may be formed after the sintered body 5 is manufactured by engraving or pressing.

[0025] Let me elaborate on the character-shaped indentation 52. A character-shaped indentation refers to any sequence of characters, including single characters such as "l" as exemplified in Figure 5. This single character may also be a symbol such as "." (period). Furthermore, the entire cone-shaped or V-shaped indentation used for temperature measurement does not have to form a character-shaped indentation; only a part of it may form a character-shaped indentation. In other words, in the example of Figure 5, in addition to the indentation 52 formed as the character "l", the surface 51s may also be provided with cone-shaped or V-shaped indentations such as the indentation 12 in Figure 1, the indentation 22 in Figure 2, and the indentation 32 in Figure 3.

[0026] As illustrated in Figure 5, some or all of the indentations on the surface of the unsintered and sintered bodies may be formed to form a string of characters on their surface. The string of characters that will serve as such temperature-measuring indentations may be formed in a conical or square pyramidal shape in the case of ".", and the shape may be applied according to the shape of each character from among conical or V-shaped shapes.

[0027] Alternatively, although not illustrated, some or all of the indentations on the surface of the unsintered and sintered bodies may be formed to form a mark on that surface. This mark, or a group of marks including this mark, may also be, for example, a mark guaranteeing the quality of the sintered body or a mark representing the product. In other words, not all of the cone-shaped or V-shaped indentations used for temperature measurement may form a mark; only a portion of them may form a mark.

[0028] The above examples illustrate various conical or V-shaped recesses. The size ratio between the unsintered body and the recess should be determined according to the material of the unsintered body so that the temperature of the body can be appropriately measured at the top of the recess. The size ratio can include the ratio of the depth of the recess to the height of the body, and the ratio of the size of the bottom surface of the recess (such as the base of a cone) to the size of the surface. The ratio of the width or area of ​​the bottom surface to the depth of the recess should also be determined according to the material of the unsintered body so that the temperature of the body can be appropriately measured at the top of the recess.

[0029] For example, if the unsintered material is glossy and highly reflective, a narrow, elongated indentation can be made. For materials that blacken upon sintering, such as iron, the reflectivity is low and the emissivity is high. Therefore, compared to materials with high reflectivity, the ratio of the indentation depth to the width of the base can be smaller, and the base area itself can also be smaller. For example, as illustrated in Figure 5, if a material with high emissivity is used to create an indentation for a string of characters, a sufficiently fine string can be formed.

[0030] In the example shown in Figure 1, the apex 12t of the recess 12 is ideally positioned to correspond to the center of the base of the cone. However, even if it is positioned at a location offset from the center of the base, more accurate temperature measurement is possible compared to the case without the recess 12. The same applies to other examples. Furthermore, if multiple temperature-measuring recesses are provided in the unsintered body, temperature control during sintering may be performed based on statistical values ​​such as the average value.

[0031] Next, an example of a sintered body manufacturing method according to this embodiment will be explained using Figure 6. Figure 6 is a flowchart illustrating an example of such a sintered body manufacturing method. For the sake of simplicity, the explanation will be given using the example of manufacturing the sintered body 1 shown in Figure 1.

[0032] This method for producing a sintered body mainly comprises a molding step, a measurement step, and a heating step, and may also include a verification step. For example, sintered body 1 can be produced by solidifying and sintering using a briquette method, but is not limited to this method.

[0033] First, as a molding process, the powder material of the unsintered body 1p is pressed with a mold or the like to form an unsintered body 1p having a conical recess 12 on its surface 11s (step S1). In the case of forming the unsintered body 5p exemplified in Figure 5, the process includes molding part or all of the recess to form a string of characters on the surface 51s. In either case, the unsintered body can be molded in the desired shape depending on the shape of the mold or by using inserts as needed.

[0034] Next, as a measurement step, the temperature of the cone apex 12t, which is the apex of the recess 12, is measured using a radiation thermometer from the cone base side, which is the bottom side of the recess 12 of the molded unsintered body 1p (step S2). Next, as a heating step, the unsintered body 1p is heated based on the measured temperature (step S3). Temperature measurement and heating can be performed, for example, by placing the unsintered body 1p, which has been solidified using a briquette method, into a heating furnace that is heated by irradiating it with microwaves and is also equipped with a radiation thermometer. In this case, heating can be performed using the oil content of lubricants contained in the material as a heat source to raise the temperature. It can also be said that the effect of removing such oil content can be obtained by using microwaves. Furthermore, by performing heating while controlling the temperature, it is possible to suppress increased oxidation due to overheating and insufficient oil content due to insufficient heating.

[0035] Furthermore, heating is not limited to microwave heating; it may also be far-infrared heating, or heating may be performed by placing the unsintered body 1p on a plate heater. Beyond these examples, various heating methods may be employed, such as electron beam sintering, laser sintering, or electrical resistance sintering. By heating while controlling the temperature in this manner, a sintered body 1 is produced from the unsintered body 1p.

[0036] Next, it is determined whether or not sintering is complete (step S4), and if it is not complete, the process returns to step S2. When the result in step S4 is YES, that is, when sintering is complete, the quality of the sintered body 1 is checked in the recess 12 as a confirmation step (step S5), and the manufacturing process is terminated. The quality of the sintered body 1 can be confirmed by checking the shape of the recess 12, but this confirmation may also include checking parts other than the recess 12. If the quality is satisfactory as a result of the confirmation in step S5, the product can be shipped.

[0037] Thus, in addition to measuring the temperature of the apex 12t of the recess 12 before the heating process, the temperature of the apex 12t may also be measured at appropriate intervals while heating the unsintered body during the heating process. Furthermore, the heating process may include a cooling step as needed, such as when the temperature rises too high or when heating is terminated.

[0038] For heating control based on measured temperature, for example, heating may be performed by heating to a first temperature lower than the sintering temperature, and then maintaining the first temperature for a first predetermined time once it is reached. Subsequently, this heating control may be performed by heating to a second temperature, which is the sintering temperature, and then maintaining the second temperature for a second predetermined time once it is reached, after which the temperature may be lowered. Alternatively, the heating control may simply be performed by heating to the sintering temperature, maintaining the sintering temperature for a predetermined time, and then lowering the temperature. In methods that involve pressurizing the sintering process, the timing of the switching may differ, but it is preferable to control the pressure in conjunction with the temperature control.

[0039] Furthermore, using microwaves for heating makes temperature control easier because, even if heating times vary, a certain level of quality can be ensured simply by measuring the temperature with a radiation thermometer while heating. In a simple example, to determine the end time of heating, it is sufficient to measure the temperature of recess 12, and if heating has not progressed as expected, control measures such as increasing the heating temperature or extending the heating time can be taken.

[0040] The sintered body and the method for manufacturing the sintered body according to this embodiment have been described above. As mentioned above, according to this embodiment, the temperature of the unsintered body can be accurately measured, and the sintered body can be manufactured while performing high-precision temperature control based on such high-precision temperature. In addition, by providing a recess near the center of the unsintered body, the accuracy of the measured temperature of the unsintered body can be improved.

[0041] Furthermore, according to this embodiment, the accuracy of temperature control improves quality stability. In addition to improving temperature measurement, this embodiment also offers several advantages compared to the absence of indentations: it makes it easier to apply pressure during molding, enables uniform firing which contributes to quality stability, and speeds up the sintering process. Moreover, these advantages make it easier to determine heating conditions, save energy, improve productivity, and prevent damage during heating and use. Additionally, quality can be easily confirmed by checking the shape of the indentations.

[0042] Furthermore, as described above, the sintered body according to this embodiment exhibits excellent quality stability and is expected to be highly valued due to its low content of impurities such as oil, and is also expected to be widely available as a material. For example, by using the indentations to form quality assurance text or the manufacturer's mark, it is possible to achieve material branding, improved traceability, and easier detection of infringements.

[0043] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. For example, although heating devices such as heating furnaces and radiation thermometers were not illustrated and described in the above embodiments, they only need to perform heating and temperature measurement functions. Also, the sintered body and the shape of its recess exemplified in the above embodiments are not limited to those exemplified, and any shape that allows for accurate temperature measurement is acceptable. [Explanation of symbols]

[0044] 1, 2, 3, 4, 5 Sintered body 1p, 2p, 3p, 4p, 5p Unsintered 11, 21, 31, 41, 51 Main unit 11s, 21s, 31s, 41s, 51s surface 12, 22, 32, 42, 52 indentations 12t, 22t, 42t (peak) 32t, 52t apex group 50 strings

Claims

1. A sintered body obtained by sintering an unsintered body having conical or V-shaped indentations on its surface.

2. Some or all of the recess is formed on the surface to form a string of characters or a mark. The sintered body according to claim 1.

3. A process of forming an unsintered body having a cone-shaped or V-shaped recess on its surface, A step of measuring the temperature at the top of the depression in the molded unsintered body using a radiation thermometer from the bottom side of the depression, A step of heating the unsintered body based on the measured temperature to produce a sintered body, A method for producing a sintered body, comprising the above.

4. The process further includes a step of confirming the quality of the sintered body based on the shape of the indentation. The method for producing a sintered body according to claim 3.

5. The step of forming the unsintered body includes a step of forming part or all of the recess so that it forms a string of characters or a mark on the surface. A method for producing a sintered body according to claim 3 or 4.

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