Manufacturing method for shrink-fit components

Abstract

To provide a method for manufacturing a shrink-fitting member, that suppresses damage to a columnar ceramic body also when using a deep drawing stainless steel pipe manufactured according to deep drawing processing.SOLUTION: Provided is a method for manufacturing a shrink-fitting member 30 for arranging and shrink-fitting a columnar ceramic body 20 in a deep drawing stainless steel pipe 10. The manufacturing method includes: a preparation step of preparing a deep drawing stainless steel pipe 10 manufactured according to deep drawing processing and a columnar ceramic body 20; a heating step of heating the deep drawing stainless steel pipe 10 to 900°C or higher; and a shrink-fitting step of inserting the columnar ceramic body 20 into the heated deep drawing stainless steel pipe 10 in order to apply shrink-fitting.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing shrink-fitting members.

Background Art

[0002] Since heat exchangers are often required to have characteristics such as corrosion resistance, ceramic heat exchangers are used. Heat exchangers are used for heating, cooling, and condensing various fluids including acids (such as bromic acid, sulfuric acid, hydrofluoric acid, nitric acid, hydrochloric acid, etc.), alkalis (such as caustic alkalis, etc.), halides, brine, organic compounds, etc. in the chemical industry, pharmaceutical industry, etc. In addition, heat exchangers are also used in systems that warm cooling water, engine oil, automatic transmission fluid (ATF) etc. at the start of an engine to reduce friction loss, and in systems that heat a catalyst to activate an exhaust gas purification catalyst at an early stage.

[0003] Some ceramic heat exchangers have a structure in which a columnar ceramic body is housed inside a metal tube. A heat exchanger having such a structure has an advantage that even if the ceramic body is damaged inside, the fluids do not mix with each other. As a method for housing a columnar ceramic body inside a metal tube, a shrink-fitting method is known in which the metal tube is heated, the ceramic body is inserted into a predetermined position inside the metal tube, and then cooled (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the use of seamless pipes has been considered for shrink-fitting applications. Seamless pipes are considered effective in improving the durability of heat exchangers because they have higher strength than welded pipes with seams. However, when using deep-drawn stainless steel pipes, which are manufactured by deep-drawing, as seamless pipes and performing shrink-fitting, the columnar ceramic body is prone to breakage during the shrink-fitting process. This is thought to be because the deep-drawn stainless steel pipes, manufactured by deep-drawing, become hardened due to work hardening, increasing the surface pressure on the columnar ceramic body during shrink-fitting.

[0006] This invention was made to solve the above-mentioned problems and provides a method for manufacturing shrink-fit members that can suppress damage to columnar ceramic bodies even when using deep-drawn stainless steel pipes manufactured by deep drawing. [Means for solving the problem]

[0007] The above problems are solved by the present invention as described below, and the present invention is defined as follows.

[0008] The present invention relates to a method for manufacturing a shrink-fit member, which involves placing a columnar ceramic body inside a deep-drawn stainless steel tube and shrink-fitting it. Preparation steps for preparing the deep-drawn stainless steel pipe and the columnar ceramic body manufactured by deep drawing, A heating step of heating the deep-drawn stainless steel tube to 900°C or higher, A shrink-fitting process in which the columnar ceramic body is inserted into the heated deep-drawn stainless steel pipe and shrink-fitted, This is a manufacturing method that includes [something]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing shrink-fit members that can suppress damage to columnar ceramic bodies even when using deep-drawn stainless steel pipes manufactured by deep-drawing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the honeycomb structure perpendicular to the axial direction. [Figure 2] This is a cross-sectional view of the honeycomb structure perpendicular to the axial direction. [Figure 3] This is a diagram illustrating a method for manufacturing a shrink-fit member according to an embodiment of the present invention. [Figure 4] This graph shows the dependence of Vickers hardness on heating temperature in the central part of the axial length of a deep-drawn stainless steel tube formed from SUS436L. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the drawings as appropriate. The present invention is not limited to the embodiments described below, and it should be understood that modifications, improvements, etc., to the embodiments described below, made based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention, also fall within the scope of the present invention.

[0012] The method for manufacturing a shrink-fit member according to an embodiment of the present invention is to place a columnar ceramic body inside a deep-drawn stainless steel tube and shrink-fit it. First, we will describe the deep-drawn stainless steel tube and columnar ceramic body used in the manufacturing method of the shrink-fit member according to the embodiment of the present invention.

[0013] <Deep-drawn stainless steel pipe> Deep-drawn stainless steel pipes are stainless steel pipes manufactured by deep-drawing. Furthermore, it is preferable that the deep-drawn stainless steel pipe has not undergone heat treatment after the deep-drawing process. In other words, the deep-drawn stainless steel pipe should not have undergone heat treatment after the deep-drawing process but before the heating process described later. Deep-drawn stainless steel pipe that has not undergone heat treatment after the deep-drawing process has hardened due to work hardening caused by the deep-drawing process.

[0014] The shape of the deep-drawn stainless steel pipe is not particularly limited as long as it is a shape into which a columnar ceramic body can be inserted. It can have various shapes such as cylindrical, square tube-shaped, etc. Also, the deep-drawn stainless steel pipe may be a straight pipe having a uniform diameter in the axial direction, or it may be a pipe other than a straight pipe. A pipe other than a straight pipe is a pipe configured such that the diameter varies in the axial direction. For example, it includes a pipe having a tapered portion in part, a reduced-diameter and / or enlarged-diameter pipe.

[0015] The deep-drawn stainless steel pipe preferably has a thermal expansion coefficient at 0 to 1100 °C of 10 to 22×10 ,

[0019] , , / °C. With such a deep-drawn stainless steel pipe having such a thermal expansion coefficient, it is possible to facilitate the insertion of the columnar ceramic body inside during the heating process described later.

[0016] The type of stainless steel constituting the deep-drawn stainless steel pipe is not particularly limited, and ferritic, austenitic, etc. can be used. Examples of ferritic stainless steel include SUS430, SUS436L, etc., and examples of austenitic stainless steel include SUS304, etc.

[0017] The deep-drawn stainless steel pipe can be manufactured by deep-drawing a stainless steel plate. The conditions for deep-drawing can be appropriately adjusted according to the type of stainless steel plate used, etc., and are not particularly limited. Also, a commercially available deep-drawn stainless steel pipe may be used.

[0018] <Columnar ceramic body> The columnar ceramic body is formed in a columnar shape from ceramic and has a fluid flow path extending from the first end face to the second end face. The columnar shape is not limited to a cylindrical shape, and it may have an elliptical shape, an oval shape in which arcs are combined, a square shape, or other polygonal shapes in a cross-section perpendicular to the axial direction (the direction in which the flow path extends). Also, the columnar ceramic body may be a hollow-type ceramic body having a hollow portion in the central part in a cross-section perpendicular to the axial direction.

[0019] The thermal conductivity of the columnar ceramic body is preferably 50 W / (m·K) or higher at 25°C, more preferably 100 to 300 W / (m·K), and even more preferably 120 to 300 W / (m·K). By setting the thermal conductivity of the columnar ceramic body within this range, good thermal conductivity is achieved, and heat within the columnar ceramic body can be efficiently transferred to the outside. The thermal conductivity values ​​were measured using the laser flash method (JIS R1611-1997).

[0020] Columnar ceramic bodies are primarily composed of ceramics. "Primarily composed of ceramics" means that the mass ratio of ceramics to the total mass is 50% by mass or more. The columnar ceramic body preferably contains silicon carbide (SiC), which has high thermal conductivity, as its main component. "Containing silicon carbide (SiC) as its main component" means that the mass ratio of silicon carbide (SiC) to the total mass is 50% by mass or more. Specifically, as the material for the columnar ceramic body, Si-SiC-based materials such as Si-impregnated SiC and (Si+Al)-impregnated SiC, metal-composite SiC, recrystallized SiC, Si3N4, and SiC can be used. Among these, Si-SiC-based materials are preferred because they can be manufactured inexpensively and have high thermal conductivity.

[0021] The columnar ceramic body is preferably a honeycomb structure. Here, Figures 1 and 2 show cross-sectional views of a typical honeycomb structure perpendicular to the axial direction. The honeycomb structure 100 shown in Figure 1 has an outer perimeter wall 110 and a partition wall 130 disposed inside the outer perimeter wall 110, which partitions a plurality of cells 120 extending from a first end face to a second end face. The honeycomb structure 200 shown in Figure 2 has an outer perimeter wall 110, an inner perimeter wall 140, and a partition wall 130 disposed between the outer perimeter wall 110 and the inner perimeter wall 140, which partitions a plurality of cells 120 extending from a first end face to a second end face. This honeycomb structure 200 is called a hollow honeycomb structure. These honeycomb structures 100 and 200, by having partition walls 130, can efficiently collect heat from the fluid flowing through the cells 120 and transfer it to the outside. Furthermore, the shape of the cell 120 in a cross-section perpendicular to the axial direction of the honeycomb structure 100,200 is not limited to the shape shown in the illustration, and may be circular, elliptical, triangular, or other polygonal shapes.

[0022] The cell density (i.e., the number of cells per unit area) in a cross-section perpendicular to the axial direction of the honeycomb structure 100,200 is not particularly limited and can be adjusted as appropriate depending on the application, but is generally between 4 and 320 cells / cm². 2 It is preferable that the cell density be within the range of 4 cells / cm². 2 By doing so, the strength of the partition wall 130, and consequently the strength and effective GSA (geometric surface area) of the honeycomb structures 100 and 200 themselves, can be sufficiently ensured. Furthermore, the cell density is set to 320 cells / cm². 2 By doing the following, it is possible to prevent an increase in pressure loss when the fluid flows.

[0023] The thickness of the partition walls 130 of the honeycomb structures 100 and 200 can be designed appropriately according to the purpose and is not particularly limited. The thickness of the partition walls 130 is preferably 50 μm to 2 mm, and more preferably 60 μm to 600 μm. If the thickness of the partition walls 130 is 50 μm or more, the mechanical strength is improved and damage due to impact and thermal stress can be prevented. On the other hand, if the thickness of the partition walls 130 is 2 mm or less, the proportion of the cell volume in the honeycomb structures 100 and 200 is increased, which reduces the fluid pressure loss and improves the heat exchange efficiency.

[0024] The thickness of the outer periphery wall 110 and inner periphery wall 140 of the honeycomb structures 100,200 can be appropriately designed according to the purpose and are not particularly limited. When the shrink-fit members are used for general heat conduction applications, the thickness of the outer periphery wall 110 and inner periphery wall 140 is preferably more than 0.3 mm and 10 mm or less, more preferably between 0.5 mm and 5 mm, and even more preferably between 1 mm and 3 mm. Furthermore, when the shrink-fit members are used for heat storage applications, it is also preferable to increase the heat capacity of the outer periphery wall 110 by making the thickness of the outer periphery wall 110 10 mm or more.

[0025] The porosity of the outer periphery wall 110, partition wall 130, and inner periphery wall 140 is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. Alternatively, the porosity of the outer periphery wall 110, partition wall 130, and inner periphery wall 140 can be 0%. By setting the porosity of the outer periphery wall 110, partition wall 130, and inner periphery wall 140 to 10% or less, the thermal conductivity can be improved.

[0026] The isostatic strength of the honeycomb structure 100,200 is preferably greater than 100 MPa, more preferably 150 MPa or greater, and even more preferably 200 MPa or greater. When the isostatic strength of the honeycomb structure 100,200 is greater than 100 MPa, the honeycomb structure 100,200 exhibits superior durability. The isostatic strength of the honeycomb structure 100,200 can be measured in accordance with the method for measuring isostatic fracture strength specified in JASO standard M505-87, an automotive standard issued by the Society of Automotive Engineers of Japan.

[0027] Columnar ceramic bodies can be manufactured by methods known in the art. A specific method for manufacturing columnar ceramic bodies will be explained using the manufacturing method of honeycomb structures 100 and 200 as an example. First, a clay mold containing ceramic powder is extruded into a desired shape to produce a honeycomb molded body. At this time, by selecting a suitable die and jig, the shape and density of the cells 120, the number, length and thickness of the partition walls 130, and the shape and thickness of the outer wall 110 and inner wall 140 can be controlled. Furthermore, the above-mentioned ceramics can be used as the material for the honeycomb molded body. For example, when producing a honeycomb molded body mainly composed of Si-impregnated SiC composite material, a predetermined amount of SiC powder is mixed with a binder and water or an organic solvent, the resulting mixture is kneaded to form a clay mold, and then molded to obtain a honeycomb molded body of the desired shape. Then, the obtained honeycomb molded body is dried, and by impregnating and firing metallic Si into the honeycomb molded body in a reduced-pressure inert gas or vacuum, a honeycomb structure 100,200 can be obtained.

[0028] The method for manufacturing a shrink-fit member according to an embodiment of the present invention is carried out using the deep-drawn stainless steel tube and columnar ceramic body described above. A diagram (perspective view) illustrating this manufacturing method is shown in Figure 3. A method for manufacturing a shrink-fit member according to an embodiment of the present invention includes a preparation step, a heating step, and a shrink-fit step. Furthermore, this manufacturing method may further include a cooling step after the shrink-fit step. A manufacturing method having these steps can be carried out using a known manufacturing apparatus (for example, the manufacturing apparatus described in Japanese Patent Publication No. 6510283).

[0029] <Preparation process> The preparation step involves preparing the deep-drawn stainless steel pipe 10 and the columnar ceramic body 20, which are manufactured by deep drawing. The deep-drawn stainless steel pipe 10 may be manufactured by deep drawing as described above, or a commercially available product may be used. The columnar ceramic body 20 can be manufactured by known methods as described above.

[0030] An intermediate material may be wrapped around the outer surface of the columnar ceramic body 20 parallel to the axial direction, if necessary. In this case, the intermediate material may be attached to the outer surface of the columnar ceramic body 20 parallel to the axial direction using an adhesive. By using an adhesive, the intermediate material can be attached uniformly. It is preferable that the adhesive is sufficiently thin and has good heat transfer properties. Intermediate materials include graphite sheets, metal sheets, gel sheets, and elastoplastic fluids. Examples of metals that make up metal sheets include gold (Au), silver (Ag), copper (Cu), and aluminum (Al). An elastoplastic fluid is a material that behaves as a solid (possesses an elastic modulus) without plastic deformation under small forces, but deforms freely like a fluid when a large force is applied; grease is an example. Considering adhesion and thermal conductivity, a graphite sheet is preferable as the intermediate material.

[0031] <Heating process> The heating process involves heating the deep-drawn stainless steel tube 10 to 900°C or higher. By heating the deep-drawn stainless steel tube 10 to such a temperature, the deep-drawn stainless steel tube 10, which has hardened due to the deep-drawing process, softens. As a result, the increase in surface pressure of the deep-drawn stainless steel tube 10 on the columnar ceramic body 20 during the shrink-fitting process can be suppressed, making the columnar ceramic body 20 less likely to break. Furthermore, since the heating necessary for shrink-fitting can be performed simultaneously with this heating process, manufacturing time can be shortened and manufacturing costs can be reduced. From the viewpoint of suppressing the increase in manufacturing costs due to rising heating temperatures, the heating temperature is preferably less than 1000°C, and more preferably 980°C or lower.

[0032] Here, Figure 4 shows a graph of the dependence of Vickers hardness on heating temperature at the center of the axial length of a deep-drawn stainless steel tube 10 (axial length 57 mm, outer diameter 87 mm, inner diameter 85 mm, thickness 1 mm) formed from SUS436L. As shown in Figure 4, the Vickers hardness of the unheated deep-drawn stainless steel tube 10 was 243 HV, while heating to 900°C or higher reduced the Vickers hardness of the deep-drawn stainless steel tube 10 to approximately 150 HV. Therefore, by setting the heating temperature to 900°C or higher, the deep-drawn stainless steel tube 10, which has been hardened by deep-drawing, can be sufficiently softened. The Vickers hardness values ​​mentioned above are the average of five measurements taken at room temperature (25°C) using a Vickers hardness tester.

[0033] The heating time is not particularly limited, but is preferably 5 seconds or more, and more preferably 10 seconds or more. By controlling the heating time in this manner, the deep-drawn stainless steel tube 10 can be sufficiently softened. Furthermore, from the viewpoint of suppressing the increase in manufacturing costs due to prolonged heating time, the heating time is preferably 60 seconds or less, and more preferably 30 seconds or less.

[0034] The heating method is not particularly limited, but it is sufficient to place a heating means on the outer circumference of the deep-drawn stainless steel pipe 10 and heat the deep-drawn stainless steel pipe 10 with the heating means. As the heating means, for example, a high-frequency heating machine can be used.

[0035] <Shrink-fitting process> The shrink-fitting process involves inserting a columnar ceramic body 20 into a heated deep-drawn stainless steel pipe 10 and shrink-fitting it. Specifically, as shown in Figure 3, the columnar ceramic body 20 is moved in the direction of the arrow and positioned in a predetermined location within the heated deep-drawn stainless steel pipe 10 for shrink-fitting. As the temperature of the heated deep-drawn stainless steel pipe 10 decreases, the pipe, which expanded due to heating, contracts, resulting in a shrink-fitted member 30 in which the columnar ceramic body 20 is fixed in the predetermined position within the deep-drawn stainless steel pipe 10.

[0036] The method for moving the columnar ceramic body 20 is not particularly limited, but can be carried out using various known driving means. For example, the deep-drawn stainless steel pipe 10 and the columnar ceramic body 20 can be positioned in a straight line, and the columnar ceramic body 20 can be moved to a predetermined position inside the deep-drawn stainless steel pipe 10 using a driving means having a drive shaft.

[0037] <Cooling process> The cooling process involves cooling the deep-drawn stainless steel pipe 10. By performing aggressive cooling, the shrink-fit member 30 can be obtained quickly. The cooling conditions are not particularly limited and can be adjusted as appropriate depending on the type of deep-drawn stainless steel tube 10 used.

[0038] In the method for manufacturing a shrink-fit member according to the embodiment of the present invention having the above steps, the increase in surface pressure of the deep-drawn stainless steel pipe 10 on the columnar ceramic body 20 during the shrink-fit process can be suppressed by softening the deep-drawn stainless steel pipe 10 that has been hardened by deep drawing, thereby suppressing damage to the columnar ceramic body 20. Furthermore, the shrink-fit member 30 manufactured by this method uses a seamless deep-drawn stainless steel tube 10, and since damage to the columnar ceramic body 20 is suppressed, it has excellent durability and reliability. Therefore, it is suitable for use as a heat exchange member. [Examples]

[0039] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0040] As a columnar ceramic body, a honeycomb structure (cylindrical) with a circular cross-section perpendicular to the axial direction was fabricated. First, a clay containing SiC powder was extruded into the desired shape, dried, processed to predetermined external dimensions, and then fired by Si impregnation to create the honeycomb structure. The fabricated honeycomb structure had a square cell shape in the cross-section perpendicular to the axial direction and a cell density of 56 cells / cm³. 2 The outer diameter of the outer wall was set to 85 mm, the axial length (direction of the first fluid flow) to 36 mm, the thickness of the outer wall to 1.5 mm, the thickness of the partition wall to 0.3 mm, the porosity of the outer wall and partition wall to 2%, the thermal conductivity (at 25°C) to 150 W / (m·K), and the isostatic strength to 100 MPa.

[0041] Next, a deep-drawn stainless steel tube (made of SUS436L, unheat-treated) was prepared. The deep-drawn stainless steel tube had an axial length of 57 mm, an outer diameter of 87 mm, an inner diameter of 85 mm, a thickness of 1 mm, and a thermal expansion coefficient of 11 × 10⁻¹⁰°C between 0 and 1100°C. -6 The temperature was set to / ℃. Next, after heating the deep-drawn stainless steel pipe to the temperatures shown in Table 1, a honeycomb structure was inserted into the deep-drawn stainless steel pipe and shrink-fitted to obtain a shrink-fitted member. The honeycomb structure of the obtained shrink-fitted members was visually inspected to evaluate the presence or absence of cracks. Furthermore, the Vickers hardness of the deep-drawn stainless steel pipe at the midpoint of its axial length was measured using the method described above. These results are shown in Table 1.

[0042] [Table 1]

[0043] As shown in Table 1, when the heating temperature of the deep-drawn stainless steel pipe was 900°C or higher, the pipe was sufficiently softened, and no cracks occurred in the honeycomb structure after shrink-fitting. In contrast, when the heating temperature of the deep-drawn stainless steel pipe was 850°C, the pipe was not sufficiently softened, and cracks occurred in the honeycomb structure after shrink-fitting.

[0044] As can be seen from the above results, the present invention provides a method for manufacturing shrink-fit members that can suppress damage to columnar ceramic bodies even when using deep-drawn stainless steel pipes manufactured by deep drawing. [Explanation of Symbols]

[0045] 10 Deep-drawn stainless steel tubes 20 Columnar ceramic body 30 Shrink-fit components 100,200 Honeycomb Structure 110 Peripheral wall 120 cells 130 Bulkhead 140 Inner wall

Claims

1. A method for manufacturing shrink-fit members, comprising placing a columnar ceramic body inside a deep-drawn stainless steel pipe and shrink-fitting it, Preparation steps for preparing the deep-drawn stainless steel pipe and the columnar ceramic body manufactured by deep drawing, A heating step of heating the deep-drawn stainless steel tube to 900°C or higher, A shrink-fitting process in which the columnar ceramic body is inserted into the heated deep-drawn stainless steel pipe and shrink-fitted, A manufacturing method that includes this.

2. The manufacturing method according to claim 1, wherein the heating time of the deep-drawn stainless steel tube is 5 seconds or more.

3. The manufacturing method according to claim 1 or 2, wherein the deep-drawn stainless steel pipe has not undergone heat treatment after the deep-drawing process but before the heating step.

4. The manufacturing method according to any one of claims 1 to 3, further comprising a cooling step of performing cooling after the shrink-fitting step.

5. The manufacturing method according to any one of claims 1 to 4, wherein the columnar ceramic body is a honeycomb structure having an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and partitioning a plurality of cells extending from a first end face to a second end face, or a honeycomb structure having an outer peripheral wall, an inner peripheral wall and a partition wall disposed between the outer peripheral wall and the inner peripheral wall and partitioning a plurality of cells extending from a first end face to a second end face.

6. The deep-drawn stainless steel tube has a thermal expansion coefficient of 10 to 22 × 10 at 0 to 1100°C. -6 A manufacturing method according to any one of claims 1 to 5, wherein the temperature is / ℃.

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