JP6502225B2 - Ceramic heater and method of manufacturing the same - Google Patents

Description

  The present invention relates to a ceramic heater for use in, for example, a hot-water-washed toilet seat, a fan heater, an electric water heater, and a 24-hour bath, and in particular, a metal annular flange is externally fitted on a ceramic heater body. The present invention relates to a ceramic heater having a different structure and a method of manufacturing the same.

  Generally, a heat exchange unit having a resin container (heat exchanger) is used for the hot water cleaning toilet seat. A cylindrical ceramic heater is attached to the heat exchange unit in order to warm the cleaning water contained in the heat exchanger.

  As this type of ceramic heater, an annular ceramic flange made of a flat plate is externally fitted to a cylindrical ceramic heater main body, and a heater main body and the flange are joined via glass. There is.

  Also, in recent years, in order to improve the airtightness and strength (bonding strength) between the heater body and the flange, etc., an annular metal flange made of a flat plate is removed from the cylindrical ceramic heater body. It has been proposed to fit and connect the heater body and the flange with a brazing material (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 11-74063 JP-A-9-283197

  However, when the above-described heater main body and the metal flange are heat-joined, there is a problem that rust is generated during use due to a change in the surface structure of the metal flange.

  Specifically, when heating and joining a ceramic heater body and a flange made of metal containing chromium and iron, chromium segregates at metal grain boundaries on the surface of the metal flange when heated to a certain temperature range. There are chromium-deficient tissues around it. And since the iron content is high in the chromium-deficient tissue, iron may be oxidized on the side of the metal flange where it is easy for water to contact during use, resulting in rust. Therefore, not only the corrosion resistance is lowered in this case, but also the bonding strength between the heater body and the flange is lowered, so that it has been difficult to impart sufficient performance to the ceramic heater.

  Further, in order to prevent the occurrence of rust due to the above-mentioned cause, it has been necessary to apply nickel plating to a metal flange or to select a glass that can be welded at a temperature that is hard to segregate. Therefore, there is a problem that the ceramic heater tends to be complicated to manufacture.

  The present invention has been made in view of the above problems, and an object thereof is to provide a ceramic heater which is excellent in bonding strength and corrosion resistance between a heater main body and a flange which are bonded via glass, and which is easy to manufacture It is in providing a manufacturing method.

  As means for solving the above problems (means 1), there is provided a ceramic heater comprising a cylindrical heater body made of ceramic and a metal annular flange externally fitted to the heater body. The flange has a hole penetrating the first surface and the second surface, and has a concave portion on the first surface side, and the concave portion has a glass reservoir filled with glass. The flange and the heater main body are joined via the glass disposed in the glass reservoir, and at least the surface layer around the hole on the second surface side of the flange is the flange. There is a ceramic heater characterized in that the grain boundaries of the metal structure are in a crushed state as compared with the inner layer portion.

  Therefore, according to the invention described in means 1, at least the surface layer portion around the hole on the second surface side of the flange is in a state where the grain boundary of the metal structure is crushed as compared with the inner layer portion of the flange. For this reason, it becomes difficult to generate chromium segregation to the grain boundary in the surface layer portion, and it becomes difficult to generate a chromium deficient structure having a high iron content. Thus, the occurrence of rust on the second surface side of the flange due to the oxidation of iron in the chromium-deficient tissue is avoided. Therefore, it is possible to provide a ceramic heater which is excellent in bonding strength and corrosion resistance between the heater main body and the flange bonded via glass, and which is easy to manufacture. Here, "the surface layer portion around the hole portion" refers to the surface layer portion in a region which is in the range of 2 mm in the radial direction from the opening edge of the hole portion.

  In the ceramic heater of the above means, the glass reservoir portion of the concave portion of the flange is filled with glass, and the heater body and the flange are joined via the glass. Therefore, when manufacturing the ceramic heater of this configuration, for example, a glass reservoir may be filled with a glass material, and the heater body and the flange may be welded and joined via the glass. Therefore, compared with the case where the conventional joining method by brazing is performed, it can be set as the ceramic heater which can be manufactured easily.

  Moreover, when the flange of the said means which has a concave-shaped part is used, compared with the case where it joins only with the narrow inner peripheral surface of the width of the hole of a flat flange, for example, It is welded to the outer peripheral surface of the heater body and the inner surface of the hole of the flange over a wide area along the direction. Thereby, high air tightness and bonding strength are provided between the heater body and the flange.

  Here, the “glass reservoir” refers to a portion of the concave portion capable of storing glass (a portion filled with glass and stored).

  When the flange is made of a metal containing chromium and iron, variation in the value of chromium content / iron content in the surface layer portion around the hole of the flange is small (that is, the value of "maximum value-minimum value" is small) Is preferred, and the iron content is preferably low.

  Specifically, when the surface layer around the hole is randomly analyzed at 10 locations in 10 μm squares, the maximum value of the chromium content / iron content and the minimum value of the chromium content / iron content Preferably, the iron content is less than 45%. Such a metallographic structure can reliably prevent the occurrence of rust in the flange, since the chromium segregation and the abundance of chromium deficient structures are sufficiently small. More preferably, when the surface layer part around the hole is randomly analyzed at 10 locations in 5 μm squares, the maximum value of the chromium content / iron content and the minimum value of the chromium content / iron content The difference is preferably 100% or less and the iron content is less than 55%.

  With regard to the first side of the glass-filled flange (i.e. the side with the concave portion), the chromium content of the surface layer is preferably greater than the chromium content of the inner layer. In this case, since the wettability of the glass on the first surface side is improved, the glass can be easily joined firmly to the flange, and the airtightness and the joint strength are improved. The chromium in the surface layer portion of the flange may be present as a single metal or may be present as an oxide.

  The flange is preferably formed in a cup-shaped bent state so that the plate material has a concave portion, and the glass is formed to fill at least a part of the inside of the cup serving as a glass reservoir. Is preferred. With such a structure, the flange can be easily manufactured from the plate material by, for example, pressing.

  In the ceramic heater of the above means, the thermal expansion coefficient of the metal constituting the flange is preferably larger than the thermal expansion coefficient of the ceramic constituting the heater body and the thermal expansion coefficient of the glass. Therefore, when the temperature at the time of welding of the glass (welding temperature) decreases, for example, to normal temperature, stress can be applied to the inner glass and the heater main body from the outer flange. By the action of this stress, airtightness and joint strength can be enhanced.

Here, the thermal expansion coefficient of the metal forming the flange are not particularly limited, may be employed a value in the range of, for example, ^{100 × 10 -7 / K~200 × 10} -7 / K. As the thermal expansion coefficient and the thermal expansion coefficient of the glass ceramic constituting the heater body, both are not particularly limited, the value of, for example, within a range of ^{50 × 10 -7 / K~90 × 10} -7 / K It can be adopted. In addition, it is preferable that the thermal expansion coefficient of glass is larger than the thermal expansion coefficient of a ceramic, and in this case, airtightness and joining strength can be further improved.

  In the ceramic heater, the flange preferably applies compressive residual stress to the glass and the heater body, and in this case, the airtightness and bonding strength can be further improved.

  In the ceramic heater of the above means, as a ceramic for forming the heater main body, for example, alumina, aluminum nitride, silicon nitride, boron nitride, zirconia, titania, mullite and the like can be mentioned as preferable examples. The heater main body includes a heating element (heater pattern layer) made of, for example, tungsten, molybdenum, tantalum or the like.

The glass used for the ceramic heater of the above means is not particularly limited. For example, B ₂ O ₃ · SiO ₂ · Al ₂ O ₃ system, SiO ₂ · Na ₂ O system, SiO ₂ · PbO system, SiO ₂ · Al ₂ O ₃ · BaO-based glasses, or component-based glasses in which the respective components are replaced, etc. may be mentioned as preferable examples.

  The depth (depth in the axial direction) of the glass reservoir in which the glass is stored is preferably set, for example, in the range of 1 mm to 20 mm, and the depth of the glass may be set, for example, 2 mm or more preferable.

  Further, as another means (means 2) for solving the above-mentioned problems, there is provided a method of manufacturing the ceramic heater according to the above-mentioned means 1, wherein mechanical or physical with respect to the second surface side of the flange The process of crushing the grain boundary of the metal structure in the surface layer portion around the hole by processing, and heating and melting the material of the glass to a welding temperature and then cooling, the flange via the glass And a step of welding the heater body with each other.

  Therefore, according to the invention described in means 2, the result that the grain boundaries of the metal structure in the surface layer around the hole are crushed (broken) by mechanical or physical processing on the second surface side of the flange Chromium is less likely to segregate at grain boundaries of the metal structure. Therefore, the metal structure is less likely to generate a chromium-deficient tissue having a high iron content. Thus, the occurrence of rust on the second surface side of the flange due to the oxidation of iron in the chromium-deficient tissue is avoided. Further, according to the present invention, it is not required to perform plating treatment on the flange or to select a specific glass in order to prevent rust, thereby avoiding complication of manufacturing. it can.

  Either of the grain boundary breaking step and the welding step may be performed first, but it is preferable to perform the welding step after the grain boundary breaking step, for example. The flange is preferably made of a metal containing chromium, and it is preferable to deposit chromium on the surface layer around the hole by heating the glass to a welding temperature.

  Here, as the mechanical or physical processing, any processing method capable of crushing the grain boundaries of the metal structure forming the flange can be employed, and a specific example is a blast Processing, barrel processing, sandpaper processing, grinding processing etc. can be mentioned.

(A) is a front view of the ceramic heater in the embodiment embodying the present invention, (b) is a partially cutaway view when the flange and the glass portion in the same ceramic heater are cut along the axial direction. The top view which permeate | transmits and shows the glass part of the ceramic heater of embodiment. Explanatory drawing which expand | deploys and shows the heater pattern layer side of the ceramic layer of the ceramic heater of embodiment. (A) is a top view which shows the flange of the ceramic heater of embodiment, (b) is AA sectional drawing of (a). The principal part expansion fracture side view when the flange in the ceramic heater of an embodiment, and the portion of glass are cut along the direction of an axis. The principal part expansion fracture side view when the flange in the ceramic heater of an embodiment, and the portion of glass are cut along the direction of an axis. (A)-(f) is an explanatory view showing a manufacturing method of a ceramic heater of an embodiment. The photograph which shows the SEM image of product sample A in an example of an experiment. The photograph which shows the SEM image of product sample B in an example of an experiment. The photograph which shows the SEM image of product sample C in an example of an experiment. The photograph which shows the SEM image of product sample D in an example of an experiment.

  Hereinafter, a ceramic heater according to an embodiment of the present invention and a method of manufacturing the same will be described with reference to FIGS.

  The ceramic heater 11 of the present embodiment is used, for example, in a heat exchanger of a heat exchange unit of a warm water washing toilet seat to warm the washing water.

  As shown in FIGS. 1 and 2, the ceramic heater 11 includes a cylindrical ceramic heater body 13 and a metal annular flange 15 fitted on the heater body 13. . The heater main body 13 is composed of a ceramic tube 17 and a ceramic layer 19 covering almost the entire outer periphery of the ceramic tube 17. In the present embodiment, the outer diameter of the ceramic tube 17 is set to 10 mmφ, the inner diameter is set to 8 mmφ, and the length is 65 mm, and the thickness of the ceramic layer 19 is set to 0.5 mm and the length 60 mm. Since the ceramic layer 19 does not completely cover the outer periphery of the ceramic tube 17, the outer peripheral surface 14 of the heater main body 13 is formed with a groove 21 having a width of 1 mm and a depth of 0.5 mm extending along the axial direction. There is.

The ceramic tube 17 and the ceramic layer 19 constituting the heater main body 13 are made of alumina, for example. The thermal expansion coefficient of alumina is in the range of 50 × 10 ⁻⁷ / K to 90 × 10 ⁻⁷ / K, and 70 × 10 ⁻⁷ / K (30 ° C. to 380 ° C.) in this embodiment. It has become.

  As shown in FIG. 3, a heater pattern layer 22 and a pair of internal terminals 23 are formed in a serpentine pattern on the inner peripheral surface (surface on the ceramic tube 17 side) or inside of the ceramic layer 19. These internal terminals 23 are electrically connected to external terminals 25 (see FIG. 1) at the end of the outer peripheral surface of the ceramic layer 19 through via conductors and the like (not shown).

  As shown in FIG. 4, the flange 15 is an annular member made of metal such as stainless steel, for example, and the central portion of the plate is bent toward the first surface S1 to be concave (cup shape). It is. More specifically, the flange 15 of the present embodiment is formed, for example, by bending a plate having a thickness of 1 mm. At a central portion of the plate member, a hole 27 is formed which passes through a first surface S1 which is an inner surface and a second surface S2 which is an outer surface. In the present embodiment, the inner diameter of the opening side (that is, the upper side of FIG. 4B) of the concave portion 16 is set to, for example, 16 mmφ. On the other hand, the inner diameter of the bottom side (that is, the lower side of FIG. 4B) of the concave portion 16, that is, the inner diameter of the hole 27 is set to 12 mmφ, for example.

  The overall height H1 (vertical direction in FIG. 4B) of the flange 15 is 6 mm, for example, and the bottom 29 curved at a radius r (for example 1.5 mm) and upward from the bottom 29 (axial direction And a cylindrical side 31 extending perpendicularly thereto. For example, the height H2 of the bottom portion 29 is 1.5 mm, and the height H3 of the side portion 31 is 4.5 mm. Moreover, the radius r means the radius in the cross section along the axial direction.

The thermal expansion coefficient of the metal forming the flange 15 is a value within the range of ^{100 × 10 -7 / K~200 × 10} -7 / K. For example, when the flange 15 is made of SUS304 (main component is Fe, Ni, Cr), the thermal expansion coefficient thereof is 178 × 10 ⁻⁷ / K (30 ° C. to 380 ° C.), SUS 430 (main component Is made of Fe, Cr), the thermal expansion coefficient thereof is 110.times.10.sup.- ⁷ / K (30.degree. C. to 380.degree. C.).

  In this embodiment, as shown in FIG. 5, in the concave portion 16 of the flange 15, the glass 33 is a space surrounded by the outer peripheral surface of the heater main body 13 and the first surface S1 which is the inner surface of the flange 15. It is considered as a glass reservoir 35 to be filled. In FIGS. 1 and 2, the portion of the glass 33 is hatched.

  The height H4 (vertical direction in FIG. 5) of the glass reservoir 35 is set, for example, in the range of 1 mm to 20 mm, and is 5 mm in the present embodiment. The width X (i.e., the radial length of the opening) X of the side portion 31 of the glass reservoir 35 is set, for example, in the range of 1 mm to 20 mm, and is 2 mm in the present embodiment.

  In the glass reservoir 35, glass 33 is filled to 1/3 or more of the height H4 of the glass reservoir 35, and the heater body 13 and the flange 15 are welded and joined via the glass 33. The height (dimension along the axial direction of the heater main body 13) H5 of the glass 33 is set, for example, in the range of 1 mm to 19 mm.

As the glass 33, for example, _{Na 2 O · Al 2 O 3} · B 2 O 3 · SiO 2 -based glass of the so-called _{Al 2 O 3 · B 2 O} 3 · SiO 2 -based glass of (borosilicate glass) is used ing. The thermal expansion coefficient of the glass 33 is, for example, a value within the range of 50 × 10 ⁻⁷ / K to 90 × 10 ⁻⁷ / K (30 ° C. to 380 ° C.), and in the present embodiment, 62 × 10 ⁻⁷ / K (30 ° C. to 380 ° C.).

  As shown in FIG. 6 which expands FIG. 5 further, between the inner surface 28 of the hole 27 located in the bottom part 29 side of the concave portion 16 and the outer peripheral surface 14 of the heater main body 13, for example, 0.1 mm There is a gap 39 of about 1.0 mm, and in the present embodiment, the dimension Y of the gap 39 is set to about 0.3 mm to 0.5 mm. A portion of the glass 33 filled in the glass reservoir 35 on the first surface S1 side axially flows along the outer peripheral surface 14 of the heater main body 13 along the gap 39, and is located further below the lower end of the second surface S2. It has reached to.

  Here, in the case of the flange 15 of FIG. 6, mechanical and physical processing is performed on the surface layer portion including at least the periphery of the hole 27 on the second surface S2 side (ie, the surface layer portion of the bottom surface of the flange 15). It has been subjected. As a result of such mechanical and physical processing, the grain boundary of the metal structure is in a crushed state compared to the inner layer portion of the flange 15 in the surface layer portion on the second surface S2 side of the flange 15 . For convenience of illustration, in FIGS. 5 and 6, etc., a portion represented by a broken line is referred to as “grain boundary destruction portion 43”. In the present embodiment, the “surface layer” refers to a region having a depth of less than 0.1 μm from the surface of the metal structure, and the “inner layer portion” has a depth of 0.1 μm or more from the surface of the metal structure. It shall refer to the area. By the way, since the above processing is not performed on the first surface S1 side of the flange 15, the grain boundaries of the metal structure of the surface layer portion on the first surface S1 side are not in a crushed state, and the grain boundary fracture portion 43 also does not exist.

  Next, a method of manufacturing the ceramic heater 11 of the present embodiment will be described based on FIG.

  First, as shown in FIG. 7A, a cylindrical alumina ceramic tube 17 is temporarily sintered.

  Further, as shown in FIG. 7B, a refractory metal such as tungsten is printed on the surface of the alumina ceramic sheet 51 or inside the laminated sheet. Thereby, a pattern 53 to be the heater pattern layer 22, the internal terminal 23, and the external terminal 25 is formed later.

  Next, a ceramic paste (alumina paste) is applied to one side surface of the ceramic sheet 51, and the ceramic sheet 51 is wound around and adhered to the outer peripheral surface of the ceramic tube 17 as shown in FIG. 7C. Baking. Thereafter, the external terminals 25 are plated with nickel to form the heater body 13.

  Next, a plate material made of stainless steel is press-formed using a mold to form a cup-shaped flange 15, and then the second surface S2 side of the flange 15 is subjected to, for example, conventionally known barrel processing The grain boundary fracture portion 43 is selectively formed (grain boundary fracture process; see FIG. 6). Here, with barrel processing, a workpiece (work), abrasive stone (media), compound (abrasive agent), etc. are mixed in a container (barrel), and constant rotation / vibration or high speed is performed in the barrel. It refers to the method of grinding the work by applying centrifugal force etc. by turning. In the present embodiment, wet barrel processing in which polishing is mainly performed using water may be performed, or dry barrel processing in which water is not used may be performed. As an apparatus which performs barrel processing, it is also possible to use any of a rotary barrel processing machine, a vibration barrel processing machine, and a centrifugal barrel processing machine, for example. In the present embodiment, for example, while using a centrifugal barrel processing machine, alumina particles are used as a medium, a surfactant is used as a compound, and conditions of a swirling speed: 220 rpm and 30 minutes are set to perform wet barrel processing. As a result of this processing, the grain boundaries of the metal structure in the surface layer portion on the second surface S2 side of the flange 15 were broken, and the grain boundaries in that portion were made visually unclear.

  In the grain boundary fracture process, for example, conventionally known sand blasting may be performed instead of barreling. Here, sandblasting is a type of blasting, and refers to a method of grinding the surface of a work by blowing a sand-like abrasive (abrasive) together with compressed air, wet, and so on. It is both dry. In the present embodiment, for example, while using a sand blasting apparatus, sand blasting is performed using alumina beads as a polishing agent and setting a processing time of 2 minutes with an air gun. Also by this processing, the grain boundaries of the metal structure in the surface layer portion on the second surface S2 side of the flange 15 can be broken.

  In order to ensure adhesion with the glass 33 filled in the concave portion 16, the grain boundary fracture portion 43 is not formed as much as possible on the side of the first surface S1 of the flange 15. And the flange 15 prepared in this way is externally fitted in the predetermined attachment position of the heater main body 13, as FIG.7 (d) shows. In this state, the heater body 13 and the flange 15 are supported by a jig not shown.

  Further, the above-mentioned glass material made of borosilicate glass is press-formed into a ring shape, and this is calcined at 640 ° C. for 30 minutes to prepare a calcined glass material 55. Then, as shown in FIG. 7E, a ring-shaped calcined glass material 55 is disposed in the glass reservoir 35 between the heater main body 13 and the flange 15.

Next, the one in this state is put into a continuous furnace for firing, and the heater main body 13 and the flange 15 are glassed (welding step). Specifically, the calcined glass material 55 is melted by heating the inside of the continuous furnace at a welding temperature (1015 ° C.) for a predetermined time under a reducing atmosphere (for example, N ₂ + 5% H ₂ ). Thereafter, the calcined glass material 55 is cooled to a normal temperature (for example, 25 ° C.) and solidified to weld and fix the heater main body 13 and the flange 15 via the glass 33, thereby completing the ceramic heater 11.
<Example of experiment>

  Hereinafter, an experimental example performed to evaluate the performance of the ceramic heater 11 of the present embodiment will be described.

  Here, sandblasting of the flange 15 is performed under the above conditions, and the grain boundaries of the metal structure in the surface layer portion of the second surface S2 are broken, and the above-described welding step is performed. As a result, ceramic heaters 11 (product samples A and B of Examples) in which crystal grain boundaries were visually unclear were produced. And while observing the surface layer part of 2nd surface S2 of these flanges 15 with a scanning electron microscope (x 2000), the component of chromium (Cr) and iron (Fe) by ESD (energy dispersive X ray analysis) Analysis was carried out. The results are shown in Tables 1 and 2, respectively. 8 shows a photograph showing a SEM image of the bottom of the flange 15 of the product sample A, and FIG. 9 shows a photograph showing a SEM image of the bottom of the flange 15 of the product sample B. Further, the product samples A and B of the ceramic heater 11 manufactured by the above method were put into a constant temperature and humidity chamber, and the occurrence of rust at the flange 15 portion was observed and investigated.

  At the same time, the grain boundary of the metal structure of the surface layer portion of the second surface S2 is left as it is without sandblasting the flange 15, and the above-mentioned welding step is performed. As a result, ceramic heaters (product samples C and D of Comparative Examples) were produced in which crystal grain boundaries can be clearly observed visually. And about the surface layer part of 2nd surface S2 of these flanges 15, the observation by the same scanning electron microscope and the component analysis of Cr and Fe by ESD were performed. The results are shown in Tables 3 and 4, respectively. Further, the product samples C and D were also introduced into the constant temperature and humidity chamber, and the occurrence of rust in the flange 15 portion was observed and investigated.

  In the product sample A in which the metal structure was broken at the second surface S2 of the flange 15, no grain boundary could be seen even using a scanning electron microscope (× 2000) (see FIG. 8). In addition, the surface layer around the hole 27 in the product sample A is randomly analyzed at 10 locations in 10 μm squares, and the chromium content (Cr content) and the iron content (Fe for each of a to j) The content) and the chromium content / iron content (Cr content / Fe content) which is the abundance ratio of them were determined. As a result, the maximum value of chromium content / iron content was 98%, and the minimum value of chromium content / iron content was 52%, so the value of “maximum value−minimum value” is 46% (ie, 50% or less). Also, the iron content was less than 45% in all cases. Therefore, since product sample A has small variation in the value of chromium content / iron content and low iron content, chromium segregation to the grain boundary of the metal structure in the surface layer portion of the second surface S2 of the flange 15 There were no outbreaks and no chromium-deficient tissues. Therefore, it was suggested that the grain boundary fracture portion 43 has a metal structure which is less likely to cause rust. Therefore, when observed after the constant temperature and humidity chamber was charged, the occurrence of rust in the flange 15 portion was not recognized. Therefore, it was found that the ceramic heater 11 had sufficient corrosion resistance.

  Similarly, in the product sample B in which the metallographic structure was broken at the second surface S2 of the flange 15, no grain boundaries could be seen using a scanning electron microscope (× 2000) (see FIG. 9). In addition, the surface layer around the hole 27 is randomly analyzed at 10 locations in 5 μm squares in the product sample B, and the chromium content, iron content, chromium content / iron content are obtained for each of a to j. The value of the quantity was determined. As a result, the maximum value of chromium content / iron content was 98%, and the minimum value of chromium content / iron content was 47%, so the value of “maximum value−minimum value” is 51% (ie, 100% or less). Moreover, all iron content was less than 55%. Therefore, since product sample B has small variation in the value of chromium content / iron content and low iron content, chromium segregation to the grain boundary of the metal structure in the surface layer portion of the second surface S2 of the flange 15 There were no outbreaks and no chromium-deficient tissues. Therefore, it was suggested that the grain boundary fracture portion 43 has a metal structure which is less likely to cause rust. Therefore, when observed after the constant temperature and humidity chamber was charged, the occurrence of rust in the flange 15 portion was not recognized. Therefore, it was found that the ceramic heater 11 had sufficient corrosion resistance.

  Similarly, in the product sample C in which the metallographic structure is not broken at the second surface S2 of the flange 15, the grain boundaries can be clearly seen using a scanning electron microscope (× 2000) (see FIG. 10). In addition, the surface layer around the hole 27 is randomly analyzed at 10 locations in 10 μm squares with the product sample C, and the chromium content, iron content, chromium content / iron content is obtained for each of a to j. The value of the quantity was determined. As a result, the maximum value of chromium content / iron content was 250%, and the minimum value of chromium content / iron content was 74%, so the value of “maximum value−minimum value” is 176%, It was over 50%. The maximum iron content was 48.4%, exceeding 45%. Therefore, since product sample C has a large variation in the value of chromium content / iron content and a high iron content, chromium segregation to the grain boundary of the metal structure in the surface layer portion of second surface S2 of flange 15 is It was concluded that it occurred and that chromium-deficient tissues were also generated. Therefore, it has been suggested that the metal structure is susceptible to rust. Then, when observation was carried out after the constant temperature and humidity chamber was charged, generation of rust was recognized in the flange 15 portion. Accordingly, it has been found that this ceramic heater is inferior in corrosion resistance.

  Similarly, in the product sample D in which the metallographic structure is not broken at the second surface S2 of the flange 15, the grain boundaries can be clearly seen using a scanning electron microscope (× 2000) (see FIG. 11). In addition, the surface layer around the hole 27 is randomly analyzed in 10 places of 5 μm square in the product sample D, and the chromium content, the iron content, the chromium content / iron content for each of a to j are analyzed The value of the quantity was determined. As a result, the maximum value of chromium content / iron content was 296%, and the minimum value of chromium content / iron content was 52%, so the value of “maximum value−minimum value” was 244%, It exceeded 100%. The maximum iron content was 56.0%, exceeding 55%. Therefore, since the product sample D has a large variation in the value of chromium content / iron content and a high iron content, chromium segregation to the grain boundary of the metal structure in the surface layer portion of the second surface S2 of the flange 15 It was concluded that it occurred and that chromium-deficient tissues were also generated. Therefore, it has been suggested that the metal structure is susceptible to rust. Then, when observation was carried out after the constant temperature and humidity chamber was charged, generation of rust was recognized in the flange 15 portion. Accordingly, it has been found that this ceramic heater is inferior in corrosion resistance.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the ceramic heater 11 according to the present embodiment, at least the surface layer around the hole 27 on the second surface S2 side of the flange 15 has a crushed grain boundary of the metal structure compared to the inner layer of the flange 15 It has become. For this reason, it becomes difficult to generate chromium segregation to the grain boundary in the surface layer portion, and it becomes difficult to generate a chromium deficient structure having a high iron content. Therefore, the occurrence of rust on the second surface S2 side of the flange 15 due to the oxidation of iron in the chromium-deficient tissue is avoided. Therefore, according to the present embodiment, it is possible to provide the ceramic heater 11 which is excellent in bonding strength and corrosion resistance between the heater main body 13 and the flange 15 bonded via the glass 33 and which is easy to manufacture.

  (2) The method of manufacturing the ceramic heater 11 of the present embodiment is characterized in that the grain boundary breaking step and the welding step are performed. Then, by performing mechanical or physical processing on the second surface S2 side of the flange 15 in the grain boundary fracture process, the grain boundaries of the metal structure in the surface layer portion around the hole are crushed (broken ). As a result, chromium is less likely to be segregated in the grain boundaries of the metal structure, and the occurrence of rust in the flange 15 can be prevented. In addition, according to this manufacturing method, it is not required to perform plating treatment on the flange 15 or to select a specific glass 33 in order to prevent rust, thereby avoiding complicated manufacturing. can do. Therefore, the ceramic heater 11 can be easily manufactured as compared with the prior art.

  (3) In the method of manufacturing the ceramic heater 11 according to the present embodiment, since the process sequence of performing the welding process after performing the grain boundary fracture process is adopted, the glass 33 is mechanically or physically damaged. It has the advantage of being less susceptible to Therefore, the improvement of the bonding strength between the heater main body 13 and the flange 15, corrosion resistance and the like can be easily achieved, and the reliability also becomes high. If the reverse process order is adopted, it may be necessary to take measures to avoid mechanical or physical damage to the glass 33. However, in the case of the process order of this embodiment, this process order may be used. Because such measures are unnecessary, the manufacturing cost can be reduced. Furthermore, in the manufacturing method of the present embodiment, sandblasting or barreling is performed in the grain boundary fracture process, but since the apparatus for performing these processes is relatively inexpensive, the manufacturing cost is reduced. be able to.

  (4) In the ceramic heater 11 of the present embodiment, the glass reservoir 35 of the concave portion 16 of the flange 15 is filled with the glass 33, and the heater body 13 and the flange 15 are joined via the glass 33. Therefore, when manufacturing the ceramic heater 11 of this configuration, the glass reservoir 35 may be filled with the material of the glass 33, and the heater body 13 and the flange 15 may be welded and joined via the glass 33. Therefore, the ceramic heater 11 can be easily manufactured as compared with the case where the conventional joining method by brazing is performed. Further, the flange 15 of the present embodiment is bent in a cup shape, and the glass 33 fills the inside of the cup serving as the glass reservoir 35. Therefore, if it is such a structure, flange 15 can be easily manufactured from board material by press processing etc., for example.

  (5) In the ceramic heater 11 of the present embodiment, the flange 15 having the concave portion 16 is used. For this reason, compared with the case where conventional flat flanges are joined, the glass 33 disposed in the glass reservoir 35 covers the outer peripheral surface 14 of the heater main body 13 and the hole of the flange 15 over a wide area along the axial direction. It is welded to the inner surface 28 of 27. Thereby, high airtightness and joint strength are provided between the heater main body 13 and the flange 15.

  (6) In the ceramic heater 11 of the present embodiment, the thermal expansion coefficient of the metal (stainless steel) forming the flange 15 is greater than the thermal expansion coefficient of the ceramic (alumina) forming the heater main body 13 and the thermal expansion coefficient of the glass 33 It is getting bigger. Therefore, when the temperature drops from the temperature at the time of welding of the glass 33 to normal temperature, stress can be applied from the outer flange 15 to the inner glass 33 and the heater main body 13. By the action of this stress, airtightness and joint strength can be enhanced. In addition, since the residual stress is applied to the glass 33 and the heater main body 13 after the flange 15 is manufactured, the airtightness and the bonding strength can be further improved.

  (7) In the ceramic heater 11 of the present embodiment, the flange 15 is made of stainless steel containing chromium and iron, and the chromium content of the surface of the flange 15 is larger than the chromium content of the inside of the flange 15 through the firing step. It has become. Therefore, as a result of the wettability of the glass 33 on the surface of the flange 15 being improved, the glass 33 can be easily joined firmly to the surface of the flange 15, and the airtightness and the bonding strength are improved. Further, the presence of a large amount of chromium on the surface of the metal flange 15 can improve the corrosion resistance.

  The embodiment of the present invention may be modified as follows.

  In the ceramic heater 11 according to the above-described embodiment, grain boundaries are formed in part of the surface layer portion on the second surface S2 side of the flange 15 by performing mechanical or physical processing on the bottom surface of the cup-shaped flange 15 The destructive part 43 was formed. For example, the grain boundary fracture portion 43 may be formed on the entire surface layer portion of the flange 15 on the second surface S2 side.

  In the above embodiment, the order of performing the welding process after performing the grain boundary fracture process is adopted, but the process order of performing the welding process before performing the grain boundary destruction process is adopted. It is also good.

  In the above embodiment, the grain boundaries of the metal structure are crushed by mechanical or physical processing on the side of the second surface S2 of the flange 15 in the grain boundary fracture process. Chemical processing can be employed.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above will be listed below.

(1) In the above means 1, the first surface side of the flange is not in a crushed state.
(2) In the above means 1 or 2, the thermal expansion coefficient of the metal forming the flange is larger than the thermal expansion coefficient of the ceramic forming the heater main body and the thermal expansion coefficient of the glass.
(3) In the above means 1 or 2, the thermal expansion coefficient of the metal forming the flange is larger than the thermal expansion coefficient of the glass, and the thermal expansion coefficient of the glass is the thermal expansion of the ceramic forming the heater main body Greater than a factor.
(4) In the above means 1 or 2, the flange applies compressive residual stress to the glass and the heater main body.
(5) In the above means 2, the mechanical or physical processing is blast processing.
(6) In the above means 2, the mechanical or physical processing is barrel processing.
(7) In the above means 2, the mechanical or physical processing is sandpaper processing.
(8) In the above means 2, the mechanical or physical processing is grinding.

DESCRIPTION OF SYMBOLS 11 ... Ceramic heater 13 ... Heater main body 15 ... Flange 16 ... Concave part 27 ... Hole part 33 ... Glass 35 ... Glass puddle part S1 ... 1st surface S2 ... 2nd surface

Claims (8)

A ceramic heater comprising: a ceramic cylindrical heater body; and a metal annular flange externally fitted to the heater body.
The flange has a hole penetrating the first surface and the second surface, and has a concave portion on the first surface side,
The concave portion includes a glass reservoir filled with glass, and the flange and the heater main body are joined via the glass disposed in the glass reservoir.
A ceramic heater characterized in that at least a surface layer portion around the hole on the second surface side of the flange has a grain boundary of a metal structure crushed as compared with the inner layer portion of the flange. .   The flange is made of a metal containing chromium and iron, and when the surface layer part around the hole is randomly analyzed at 10 locations in 10 μm squares, the maximum value of the chromium content / iron content, and the chromium content The ceramic heater according to claim 1, wherein the difference between the amount / the iron content and the minimum value is 50% or less, and the iron content is less than 45%.   The flange is made of a metal containing chromium and iron, and when the surface layer part around the hole is randomly analyzed in 10 places of 5 μm square, the maximum value of the chromium content / iron content and the chromium content The ceramic heater according to claim 1, wherein the difference between the amount / the iron content and the minimum value is 100% or less, and the iron content is less than 55%.   The ceramic heater according to any one of claims 1 to 3, wherein the flange is made of stainless steel.   The flange is formed in a state in which the plate is bent in a cup shape so as to have the concave portion, and the glass is formed in a state in which at least a part of the inside of the cup is filled. The ceramic heater according to any one of claims 1 to 4, characterized in that: A method of manufacturing a ceramic heater according to any one of claims 1 to 5, comprising:
Crushing the grain boundaries of the metallographic structure in the surface layer around the hole by mechanical or physical processing on the second surface side of the flange;
And a step of welding the flange and the heater main body through the glass by heating and melting the glass material to a welding temperature and then cooling the material.   After the step of crushing the grain boundaries of the metal structure in the surface layer portion around the hole portion, the step of welding the flange and the heater main body through the glass is performed. The manufacturing method of the ceramic heater as described.   The ceramic according to claim 6 or 7, wherein the flange is made of metal containing chromium, and chromium is deposited on the surface layer around the hole by heating the glass to the welding temperature. Method of manufacturing a heater.