JP6617477B2 - Stainless steel clad for gasket - Google Patents

Description

  The present invention relates to a stainless steel cladding for gaskets.

  Gaskets having heat resistance are used for automobile exhaust system parts such as automobile and motorcycle engines, exhaust manifolds, catalytic converters, EGR coolers, and turbochargers.

  FIG. 1 and FIG. 2 show examples of gaskets used for connecting parts of automobile exhaust system parts. As shown in FIG. 1 and FIG. 2, for example, a connection part 30a between the exhaust manifold 10 and the exhaust pipe 20a, a connection part 30b between the exhaust pipe 20a and the exhaust pipe 20b, and the like are formed on the flanges 21a and 21b. The bolts 40a and 40b inserted in the through holes are fastened to tighten them. At this time, the gaskets 1a and 1b are sandwiched between the gaps between the connection portions 30a and 30b. The gasket has an uneven portion (hereinafter referred to as “bead”). By tightening the bolts 40a and 40b, the bead of the gasket is deformed. As a result, prevention of gas leakage from the connecting portions 30a and 30b can be achieved by the repulsive force of the convex portion of the bead.

As a gasket that can withstand use at high temperatures, a high nitrogen stainless steel proposed in Japanese Patent Application Laid-Open No. 2009-249658 (Patent Document 1) or JIS G 4902 (corrosion and heat resistance) is used for a connection part of an exhaust system part of an automobile. An expensive material containing 50% or more of Ni by mass%, such as NCF625 and NCF718 defined in (Superalloy plate), is used. A gasket using a clad material instead of a single metal plate is known.

  As a gasket using a clad material, Japanese Patent Laid-Open No. 09-109136 (Patent Document 2) discloses a metal gasket in which a ferritic stainless steel is joined to a portion exposed to a corrosive atmosphere of a substrate made of austenitic stainless steel. Is disclosed. Japanese Utility Model Publication No. 62-2360 (Patent Document 3) discloses a gasket in which a ferrite structure layer is bonded to both surfaces of an austenite structure layer to cause creep deformation in the layer thickness direction.

JP 2009-249658 A JP 09-109136 A Japanese Utility Model Publication No. 62-2360

  Automobile exhaust system parts undergo high-temperature thermal cycles due to the heat of exhaust gas, so that expansion and contraction are repeated, and so-called “sagging” occurs in which the repulsion force of the beads decreases due to material recovery and recrystallization. . When the bead is stale, the surface pressure between the gasket and the flange decreases, and it cannot withstand the pressure of the exhaust gas, making it difficult to completely seal the bead.

  A heat-resistant gasket for automobiles, which is one of the technical fields targeted by the present invention, is mounted on an automobile and its usage time is several thousand hours. was there. Moreover, the ultimate temperature during use is 600 ° C. or higher. In some cases, it may reach 650 ° C. or higher, and further 700 ° C. or higher. At such high temperatures, the strength of ferritic stainless steels is significantly reduced, so austenitic stainless steels with excellent high temperature strength are generally applied.

  FIG. 3 is a partially enlarged view of the periphery of the connection portion 30a between the exhaust manifold 10 and the exhaust pipe 20a in FIG. As shown in FIG. 3A, the gasket 1a is sandwiched between the gaps of the connecting portion 30a, and the bead of the gasket 1a is deformed by tightening the bolt 40a, so that the contact surface between the gasket 1a and the exhaust manifold 10 Is fixed with a predetermined surface pressure applied thereto.

  However, as shown in FIG. 3 (b), when used at a high temperature for a long period of time, the beads 1a become stale. As a result, the surface pressure between the gasket 1a and the exhaust manifold 10 is lowered, and it becomes impossible to withstand the internal pressure of the exhaust gas flowing through the exhaust pipe 20a (the white arrow in the figure). And a clearance gap arises between the gasket 1a and the exhaust manifold 10, and it becomes impossible to ensure a sealing performance.

  On the other hand, the flanges 21a, 21b, etc. formed at the connection portions of the pipes 20a, 20b are thermally deformed and subjected to a long thermal cycle at a high temperature, so that a gap is formed between them and a sealing property is secured. There is also a problem that makes it impossible.

  FIG. 4 is a partially enlarged view of the periphery of the connection portion 30a between the exhaust manifold 10 and the exhaust pipe 20a in FIG. As shown in FIG. 4A, in the initial state, the contact surface between the gasket 1a and the exhaust manifold 10 is fixed in a state where a predetermined surface pressure is applied. However, when subjected to a high-temperature thermal cycle, the flange 21a is thermally deformed, the gap between the exhaust manifold 10 and the flange 21a is widened (see the white arrow in the figure), and the internal pressure of the exhaust gas flowing through the exhaust pipe 20a (see FIG. Cannot withstand the white arrow). And a clearance gap arises between the gasket 1a and the exhaust manifold 10, and it becomes impossible to ensure sealing performance. If the thermal deformation of the flange 21a increases, a gap may be generated between the gasket 1a and the exhaust manifold 10 when the engine is stopped. This problem occurs even when the bead 1a is not set.

  These problems tend to increase due to the use of a supply and exhaust system for the purpose of increasing the combustion gas temperature for the purpose of improving combustion efficiency, downsizing the engine, and increasing the output of the engine. In particular, the problem of thermal deformation of the flange described in FIG. 4 is in a situation that becomes apparent at the joint between the engine having a cooling function and another product or piping. It also becomes apparent when the combustion gas temperature rises during high-speed driving of an automobile. It should be noted that the usage time of the automobile is estimated to be several thousand hours, the engine operation stop at that time is several thousand times, and the number of high-speed traveling is estimated to be several hundred times.

  In the case of a single metal plate, even if a material as disclosed in Patent Document 1 is used, it is inevitable that the beads will be broken. The technique of Patent Document 2 is mainly for the purpose of preventing stress corrosion cracking, and has not been studied for the bead sag. In patent document 3, it does not describe about forming a bead in a gasket. Further, the thermal expansion at high temperature in the vertical direction of the gasket thickness is suppressed, and the thickness of the entire gasket is increased from the initial dimension, and the sag of the beads has not been studied.

  In any of the above techniques, no consideration is given to a method for preventing a reduction in the surface pressure of the gasket when the flange is thermally deformed.

  The present invention has been made to solve the above-described problems of the prior art, and does not reduce the surface pressure of the gasket even when the flange is thermally deformed, and always provides excellent sealing performance from the engine starting stage. It is an object to provide a stainless steel cladding for a gasket.

  The present inventors use a ferritic stainless steel and austenitic stainless steel clad material as a gasket, and effectively prevent deterioration of the sealing performance by utilizing the bimetal effect, and always have excellent sealing performance from the engine starting stage. The following knowledge was obtained.

  (A) Austenitic stainless steel is superior in strength at high temperatures and has a large thermal expansion compared to ferritic stainless steel. Further, Ni that is classified as an expensive and rare metal is generally contained as an indispensable element.

  (B) Ferritic stainless steel has a tendency for strength at a high temperature range of 600 ° C. or higher to be greatly reduced as compared to austenitic stainless steel. However, expensive Ni is generally not contained and is relatively inexpensive.

  (C) The heat-resistant gasket is repeatedly heated and cooled when the engine is started and stopped. When such a thermal history is applied to a clad material provided with an austenitic stainless steel layer and a ferritic stainless steel layer, a concave warpage occurs such that the ferritic stainless steel layer side warps due to the bimetallic effect. If the configuration of the clad material is variously adjusted, this warp can be left after cooling.

  (D) Using such a clad material, if a gasket is manufactured so that the above-mentioned concave warpage coincides with the rising direction of the bead, the bead warps in the rising direction due to heating during engine operation (that is, the height is The warpage will remain after the engine has been stopped and cooled. Since the height of the beads increases due to the stacking, it follows the thermal deformation of the flange and always provides excellent sealing performance from the engine starting stage.

  (E) In terms of cost and resources, if the use amount of Ni classified as expensive and rare metal is suppressed, it is possible to cope with environmental problems due to improvement in fuel consumption of automobiles and motorcycles.

  The present inventors have completed the present invention as a result of further detailed studies based on the above-mentioned idea.

  The gist of the present invention is the following stainless steel clad for gaskets.

  (A) A clad used for a heat-resistant gasket, comprising an austenitic stainless steel layer and a ferritic stainless steel layer, and when a thermal history including heating and cooling is applied, the ferritic stainless steel layer side after cooling Clad for heat-resistant gaskets that cause concave warping.

(B) The clad for heat-resistant gasket according to (B), wherein the austenitic stainless steel layer and the ferritic stainless steel layer satisfy the relationship of the following formula (1).
T _α · σ _αt ≧ T _γ · σ _γt (1)
However, the meaning of each symbol in the above formula (1) is as follows.
T _α : Plate thickness of the ferritic stainless steel layer σ _αt : 0.2% proof stress of the ferritic stainless steel layer at the operating temperature of the heat resistant gasket T _γ : Plate thickness of the austenitic stainless steel layer σ _γt : Use of the heat resistant gasket 0.2% yield strength of austenitic stainless steel layer at temperature

  (C) The clad for heat-resistant gasket according to (A) or (B), wherein the heating is heating to 600 ° C. or more, and the cooling is cooling to room temperature.

  (D) The clad for a heat-resistant gasket according to any one of (A) to (C), wherein a concave warp occurs on the ferritic stainless steel layer side when a thermal history that repeats heating and cooling is applied.

  (E) The heat-resistant gasket cladding according to any one of (A) to (D), wherein warpage increases by 0.1 mm or more after the tenth cooling when a thermal history of repeating heating and cooling is applied.

  According to the present invention, even when the flange is thermally deformed, the surface pressure of the gasket is not lowered, and excellent sealing performance can be always obtained from the engine starting stage.

The fragmentary sectional view which shows the example of the gasket used for the connection part of the exhaust system components of a motor vehicle. The partial exploded view which shows the example of the gasket used for the connection part of the exhaust system components of a motor vehicle. The fragmentary sectional view which shows the various aspects of a gasket. (A) shows a mode in which no internal pressure is applied, (b) shows a mode in which sealability cannot be secured when an internal pressure is applied, and (c) shows a mode in which an internal pressure is applied, The aspect which has ensured the sealing performance is shown. The fragmentary sectional view which shows the various aspects of a gasket. (A) shows an initial state, and (b) shows a state after undergoing a long thermal cycle at a high temperature. Sectional drawing which shows the example of the clad which concerns on this invention. Sectional drawing which shows the example of the gasket using the clad which concerns on this invention. It is a figure which shows the aspect of a curvature test piece. It is a figure which shows the aspect of a sealing property test material. (A) shows a plane aspect, (b) shows the cross-sectional aspect in the AB cross section in (a).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 5, the clad 5 for heat-resistant gaskets of this embodiment relates to a clad used for a heat-resistant gasket including an austenitic stainless steel layer 5a and a ferritic stainless steel layer 5b. When the heat history including heating and cooling is applied to the clad 5 for heat-resistant gasket, the warp is generated such that the ferrite-based stainless steel layer 5b side is warped after cooling.

  Next, the example of the gasket manufactured using the clad 5 for heat-resistant gaskets of this embodiment is demonstrated.

  As shown in FIG. 4, the gasket 1 includes, for example, a flat base 6 made of a clad 5 including an austenitic stainless steel layer 5 a and a ferritic stainless steel layer 5 b, a through hole 7 provided in the base 6, A bead 8 is provided at a position surrounding the through-hole 7 and is formed to rise in one of the thickness directions of the base 6. The through-hole 7 is for allowing fluid to conduct. Moreover, in this embodiment, the insertion hole (illustration omitted) for inserting a fastener is provided like a normal gasket.

  The clad material 5 includes a ferritic stainless steel layer 5b on the surface 8a side where the beads 8 are raised and formed. Here, since the expansion of the austenitic stainless steel layer 5a is large and the expansion of the ferritic stainless steel layer 5b is small at high temperatures, the beads 8 of the gasket 1 manufactured using the clad material 5 are made of ferritic stainless steel. It will warp to the layer 5a side (surface 8a side where the beads are raised and formed). In addition, the ferritic stainless steel layer 5b tends to have a strength that is significantly lower than that of the austenitic stainless steel layer 5a at the engine operating temperature (high temperature range of 600 ° C. or higher). For this reason, even if the engine is stopped and the temperature of the gasket is lowered to room temperature, part of the warpage of the bead 8 remains.

  As a result, a concave warp can be generated on the ferritic stainless steel layer 5b side after being used at a high temperature for a long time and cooled. For this reason, if it is set as the structure provided with the ferritic stainless steel layer 5b in the surface 8a side which raised and formed the bead 8, it can warp the bead 8 in the direction which warps from an initial state, ie, the starting direction of the bead 8. That is, the height of the bead 8 is increased. For this reason, the surface pressure between the gasket 1a and the exhaust manifold 10 can be maintained even at room temperature. As a result, the gasket 1a can withstand the internal pressure of the exhaust gas flowing through the exhaust pipe 20a (the white arrow in the figure) at the engine start stage and during engine operation, and the sealing performance is always excellent. Can be maintained.

  Here, the above-mentioned heating is heating by exhaust gas during engine operation, and specifically heating to the use temperature of the heat-resistant gasket. The operating temperature of the heat-resistant gasket is 600 ° C. or higher. Or it may reach 650 ° C. or higher, and further 700 ° C. or higher. Moreover, said cooling is cooling after an engine stop, and is specifically cooling to room temperature. There is no restriction on the number of repetitions of heating and cooling, but in particular, a clad having a structure in which the concave warpage toward the ferritic stainless steel layer 5b after repeating 10 times is larger than the initial state is preferable. Specifically, in the test conditions shown in the examples, a clad having a configuration in which the warpage increases by 0.1 mm or more from the initial state after the tenth cooling is preferable. Further, a clad having a configuration in which the concave warp toward the ferritic stainless steel layer 5b after 100 times is larger than the concave warp toward the ferritic stainless steel layer 5b after 10 times is preferable.

  In the above description, the gasket 1a sandwiched between the connection portions 30a between the exhaust manifold 10 and the exhaust pipe 20a is described as an example. However, the present invention is not limited to such an example. The same effects as described above can be obtained as long as the gasket is used in a portion used at a high temperature, such as the gasket 1b sandwiched between the connection portions 30b between the exhaust pipe 20a and the exhaust pipe 20b. Further, according to the present invention, even when the flange is thermally deformed (see FIG. 4B), it is possible to follow the shape of the flange. Is obtained.

  However, the austenitic stainless steel desirably has a higher coefficient of thermal expansion, and the ferritic stainless steel desirably has a low coefficient of thermal expansion. The chemical composition of austenitic stainless steel and ferritic stainless steel is not limited to a specific chemical composition. Examples of the austenitic stainless steel include SUS301, SUS301L, SUS304, SUS304LN, SUS316L, SUS310S, and SUS201. Examples of the ferritic stainless steel include SUS409L, SUS410L, SUS430, SUS444, SUS436J1L, SUS436L, and SUS430JIL.

  Here, when a thermal history including heating and cooling is applied, if the configuration is such that a concave warp occurs on the ferritic stainless steel layer side after cooling, the thickness of the cladding, the austenitic stainless steel layer, and the ferritic system There is no restriction on the balance of the thickness of the stainless steel layer.

However, it is preferable that the austenitic stainless steel layer and the ferritic stainless steel layer satisfy the relationship of the following formula (1). When this relationship is satisfied, when a thermal history including heating and cooling is applied, a concave warp occurs on the ferritic stainless steel layer side after cooling.
T _α · σ _αt ≧ T _γ · σ _γt (1)
However, the meaning of each symbol in the above formula (1) is as follows.
T _α : Plate thickness of the ferritic stainless steel layer σ _αt : 0.2% proof stress of the ferritic stainless steel layer at the operating temperature of the heat resistant gasket T _γ : Plate thickness of the austenitic stainless steel layer σ _γt : Use of the heat resistant gasket 0.2% yield strength of austenitic stainless steel layer at temperature

  In addition, even if the ratio of the thickness of the austenitic stainless steel layer 5a with respect to the total thickness is too large or too small, it is difficult to generate warpage due to a difference in thermal expansion due to heating that is a premise of the present invention. Become. On the other hand, in the present invention, since the warp remains even after cooling to room temperature, the proportion of expensive austenitic stainless steel is small and the deformation is shared. Therefore, the ratio of the thickness of the austenitic stainless steel layer 5a to the total thickness is preferably 10 to 50%. The upper limit is preferably 45%, more preferably 40%.

  Here, the clad in which the ferritic stainless steel layer 5b and the austenitic stainless steel layer 5a are directly stacked has been described. However, when it is difficult to clad both steels, both steels are joined using an insert material such as Ni foil. There is no problem.

  From the viewpoint of manufacturing cost, a two-layer clad is desirable, but a three-layer clad of ferritic stainless steel, austenitic stainless steel, austenitic stainless steel different from the austenitic stainless steel, or the like may be used. However, the thickness ratio of the austenitic stainless steel is preferably within the above range even if the clad has three or more layers. On the other hand, there is no problem even if the clad is made of two layers of different ferritic stainless steels and one phase of austenitic stainless steel, but even in this case, the thickness ratio of the austenitic stainless steel is within the above range. Is good.

  Even when the total thickness of the clad material 5 is small, it is possible to warp to the ferritic stainless steel layer side (surface side where the beads are raised and formed) at high temperatures. However, depending on the combination of clad materials selected, warping at high temperatures is insufficient, and the surface pressure with the exhaust manifold or flange (hereinafter referred to as “flange”) decreases, resulting in sufficient sealing performance. It may be difficult to ensure. On the other hand, if the total thickness is too large, depending on the combination of clad materials selected, it may be difficult to warp the ferritic stainless steel layer side (the side where the beads are raised and formed) at high temperatures. It may be difficult to ensure a good sealing performance. Therefore, the total thickness of the clad material 5 is preferably 0.1 to 0.5 mm.

  The shape of the bead is not particularly limited as long as it is formed so as to rise in one direction in the thickness direction of the substrate at a position surrounding the through hole. That is, it may be a bead such as a full bead or a trapezoidal bead formed by partially raising a flat substrate, or a half bead formed up from the inner peripheral end of the through hole. However, the effect of the present invention is remarkable in the case of a gasket having a half bead.

<Manufacturing method of clad material>
As a manufacturing method of the clad material in the present embodiment, for example, a known method such as diffusion bonding, hot rolling bonding, warm rolling bonding, cold rolling bonding can be adopted.

  When manufacturing a clad material by diffusion bonding, for example, an austenite / ferritic stainless steel sheet having a predetermined thickness manufactured by a general method (after melting, repeating hot and cold rolling and annealing) is used. The clad can be manufactured by using it as a material and holding it under predetermined conditions. The temperature is preferably 800 to 1200 ° C. The holding time is preferably 1 to 10 hours. The pressure may be 1-10 MPa. The atmosphere is preferably a non-oxidizing nest atmosphere such as Ar gas or a vacuum.

  When manufacturing a clad material by hot rolling bonding, for example, after melting, hot-rolled austenitic steel plate and ferritic stainless steel thick plate with a predetermined thickness are used as raw materials and heated at a temperature higher than the recrystallization temperature. Inter-rolling can be performed and bonded to produce a clad. The temperature is preferably 800 to 1200 ° C. The rolling rate is preferably 50% or more. If necessary, high-temperature diffusion heat treatment may then be performed. Thereafter, hot rolling, cold rolling and annealing may be repeated (generally, the final process is cold rolling) to produce a clad having a desired plate thickness and composition ratio.

  When manufacturing a clad material by joining by rolling in warm or cold, for example, a predetermined thickness manufactured by a general method (after melting, repeating hot and cold rolling and annealing) The clad can be produced by using austenite and a ferritic stainless steel sheet as a raw material, and performing rolling at a temperature lower than the recrystallization temperature or cold and bonding. In this case, a high-temperature diffusion heat treatment is generally performed next. Thereafter, hot rolling and cold rolling and annealing may be repeated (generally, the final process is cold rolling) to produce a clad.

  <Gasket manufacturing method>

  In addition, after applying beat processing to each of the austenitic stainless steel plate and ferritic stainless steel plate adjusted to a predetermined thickness, these steel plates are overlapped and the surroundings are welded, thereby providing a gasket having a bead of a predetermined shape. Can be manufactured. Further, a gasket having a bead having a predetermined shape can be manufactured by performing spot welding (resistance welding) on the clad material and partially bending the clad material. In particular, the clad plate can be warped also by a method of spot welding only the portion that becomes the apex of the beat.

  The gasket of the present embodiment can be manufactured by a technique such as press molding using the above clad material. Specifically, a gasket having a bead of a predetermined shape can be manufactured by blanking (punching), press molding, and assembling a plurality of sheets. In addition, after applying a beat process to each of the austenitic stainless steel plate and ferritic stainless steel plate adjusted to a predetermined thickness, these steel plates are overlapped and welded around to form a gasket having a bead of a predetermined shape Can be manufactured. Further, a gasket having a bead having a predetermined shape can be manufactured by performing spot welding (resistance welding) on the clad material and partially bending the clad material. In particular, the clad plate can be warped also by a method of spot welding only the portion that becomes the apex of the beat.

At this time, an austenitic stainless steel layer and a ferritic stainless steel layer are disposed so as to increase the surface pressure with the flange or the like at a high temperature. That is, when the bead of the gasket warps to the ferritic stainless steel side, the surface pressure with the flange or the like can be increased. Although the gasket of the present invention has been described based on a single gasket, austenitic stainless steel and ferritic stainless steel are also used to increase the surface pressure with a flange or the like in the case of two-layered or three-layered gaskets. By determining the position of the steel, the same effect appears.

  An austenitic stainless steel plate and a ferritic stainless steel plate having the chemical composition shown in Table 1 were produced as predetermined plate thicknesses by repeating general hot rolling, cold rolling and annealing.

  After degreasing and cleaning, two different ones are stacked, and the clad material is manufactured by diffusion bonding in a non-oxidizing atmosphere, maintaining the temperature of 1050 ° C. for 3 hours while applying a pressure of 1.4 MPa, and correcting the shape. did. Various test pieces were sampled from the same material, heated and cooled a predetermined number of times, and then subjected to the following warpage test and sealing property test. The results are shown in Table 2.

<Warpage test>
The above clad material was cut into strips having a width of 5 mm and a length of 20 mm, and then a warp test piece having a cross-sectional shape shown in FIG. 7 was obtained by press molding. Specifically, the warpage test piece has a first parallel portion between the tip and 2 mm, a taper portion between 2 mm and 4 mm from the tip, and a second parallel portion between 4 mm and the other end from the tip. The step between the 1 parallel portion and the second parallel portion was 1 mm. This level | step difference assumes the bead height of a gasket.

  After the warp test piece is heated to 700 ° C. and held for 5 minutes, the step (height) after repeating the heat history of cooling to room temperature 10 times and the step (height) after repeating 100 times are measured. did.

<Sealability test>
After the above clad material was cut into a width of 100 mm and a length of 100 mm, a through hole having a diameter of 70 mm was provided in the center, and a bead having a cross-sectional shape shown in FIG. 8 was formed by press molding to obtain a sealability test material. Specifically, as shown in FIG. 8B, the sealability test material is a first ring-shaped parallel portion between 2 mm outward from the inner peripheral end and 2 mm to 4 mm outward from the inner peripheral end. Between the first ring-shaped parallel part and the second ring-shaped parallel part (bead height). ) Was 1 mm.

  The sealability test material was heated to 700 ° C. and held for 5 minutes, and then the heat history of cooling to room temperature was repeated 100 times, and then the sealability of a gas at a predetermined pressure was evaluated. ○ (good), × (poor) ).

  As shown in Table 2, in Examples 1-27 of the present invention, the warpage of the beads after repeating heating and cooling 10 times and 100 times was larger than the initial state, and heating and cooling were repeated 100 times. The later sealability was good.

  On the other hand, Comparative Examples 28 to 37 were inferior in sealing properties after repeating heating and cooling 100 times. In addition, Comparative Example 28 is a clad between ferritic stainless steels, and Comparative Example 29 is a clad between austenitic stainless steels. Beads were crushed by heating and cooling, and gas leakage occurred. In Comparative Examples 30 to 37, the bead height after repeated heating and cooling was reduced at least 100 times, and the sealing performance was poor in the vicinity of room temperature mainly in the cooling process.

  According to the present invention, even when the flange is thermally deformed, the surface pressure of the gasket is not lowered, and excellent sealing performance can be always obtained from the engine starting stage.

DESCRIPTION OF SYMBOLS 1 Gasket 1a, 1b Gasket 2a, 2b Flange 5 Clad for heat-resistant gasket 5a Austenitic stainless steel layer 5a Ferritic stainless steel layer 6 Base 7 Through-hole 8 Bead 8a Surface where the bead is raised and formed 10 Exhaust manifold 20a, 20b Exhaust pipe 21a, 21b Flange 30a, 30b Connection part 40a, 40b Bolt

Claims (5)

A clad used for a heat-resistant gasket,
It has an austenitic stainless steel layer and a ferritic stainless steel layer,
The austenitic stainless steel layer and the ferritic stainless steel layer are
A clad for a heat-resistant gasket, which satisfies the relationship of the following formula (1) and has a concave warp on the ferritic stainless steel layer side after cooling when a thermal history including heating and cooling is applied.
T _α · σ _αt ≧ T _γ · σ _γt (1)
However, the meaning of each symbol in the above formula (1) is as follows.
T _α : Plate thickness of ferritic stainless steel layer
σ _αt : 0.2% proof stress of ferritic stainless steel layer at the operating temperature
T _gamma: plate thickness of the austenitic stainless steel layer
σ _γt : 0.2% proof stress of austenitic stainless steel layer at operating temperature of heat-resistant gasket The heating is heating to 600 ° C. or higher;
The clad for heat-resistant gasket according to claim 1, wherein the cooling is cooling to room temperature. The clad for heat-resistant gasket according to claim 1 or 2 , wherein a concave warp occurs on the ferritic stainless steel layer side when a thermal history that repeats heating and cooling is applied. The clad for a heat-resistant gasket according to any one of claims 1 to 3 , wherein warpage increases by 0.1 mm or more after the tenth cooling when a thermal history of repeating heating and cooling is applied.   The heat-resistant gasket cladding according to any one of claims 1 to 4, wherein a ratio of the thickness of the austenitic stainless steel layer to the total thickness is 10 to 50%.