JPH04350104A - Member joining structure - Google Patents

Abstract

PURPOSE:To offer a structure excellent in relief effect of thermal stress at joint surface, attainable in prolongation of service life with improvement of strength at elevated temp. and heat cycle property or the like, and effective in improvement of reliability especially when applying to large sized structure. CONSTITUTION:In a member joining structure integrally joining >=2 members 1, 2 made of a different material by welding, brazing or another joining means, at least the material composition of one side member 1 is made gradient and a material composition of a joint surface of the member 1 is made the same as the another member 2.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member joining structure for joining two or more members made of different materials, and more particularly to a member joining structure capable of improving the reliability of the joint.

0003

[Prior Art] Different parts of an integral structure, such as each side of a wall, are required to have multiple different physical properties at the same time, such as ultra-heat resistance and high mechanical strength, which are difficult to achieve with a single material composition. There are cases. Conventionally, as a countermeasure for such cases, two or more members made of different materials have been joined together by welding, brazing, or other joining means.

However, when there is a difference in the coefficient of thermal expansion of each member to be joined, the thermal stress generated during joining remains, which deteriorates high temperature characteristics and thermal cycle characteristics, resulting in cracks, etc. during use. There are problems with reliability, such as damage to the product and shortening its useful life.

For this reason, conventionally, between the joint surfaces of each member,
Various measures have been taken to alleviate thermal stress, such as interposing a joint made of a material with low rigidity or a coefficient of thermal expansion between those of each member.

[0006]

[Problem to be solved by the invention] However, even when the above-mentioned conventional measures are taken, it is difficult to reliably prevent damage such as cracking, and the reality is that sufficient effects are not always obtained. This tendency is particularly strong when applied to large structures.

The present invention was made in view of the above circumstances, and has an excellent effect of alleviating thermal stress at the bonding surface of dissimilar materials, and has a long service life due to improvements in high temperature strength, thermal cycle characteristics, etc. The object of the present invention is to provide a member joining structure that is effective for improving reliability, especially when applied to large structures. [Structure of the invention]

[0008]

[Means and effects for solving the problem] According to the inventor's study results, when dissimilar materials of uniform composition are joined by heat by welding, brazing, etc., high-temperature characteristics and thermal cycle characteristics deteriorate due to residual stress. can't avoid it,
Further, even when each of the above-mentioned means is applied, certain limitations are recognized.

Recently, composite materials in which the compositions of two or more materials with different functions are continuously changed, ie, graded composition materials, have been developed. This graded composition material has properties that change in a graded manner as the composition changes, so it can provide special properties that cannot be obtained with general homogeneous materials, such as providing ultra-heat resistance and high mechanical strength to different sides of the same member. It is considered promising for use in various fields.

[0010] This graded composition material is applied to the members to be joined, for example, a region made of the same material as the other member to be connected is set on one side of the member, and other materials are connected through the graded composition region of the intermediate layer. It is thought that by setting the originally required composition region of the material on the side surface, it will be possible to form a structure in which the joining parts are made of the same material and different materials are joined as a whole. If the joint surfaces between the members are made of the same material, the physical properties such as the coefficient of thermal expansion will also be the same, so it is thought that it will be easier to alleviate the thermal stress caused by welding or the like.

The invention of claim 1 has been made based on such knowledge, and provides a member joining structure in which two or more members made of different materials are integrally joined by welding, brazing or other joining means. is characterized in that at least one member is made of a graded composition material, and the material composition of the joint surface between this member and the other member is the same.

[0012] According to this configuration, since the materials on the joint surfaces of the members to be joined are the same, the physical properties such as the coefficient of thermal expansion match and the heat conductivity is improved, so thermal stress can be significantly reduced. It can be relaxed. Therefore, compared to conventional joint structures that connect members made of different single materials, it is possible to improve high-temperature strength, thermal cycle characteristics, etc., and improve reliability, especially when applied to large structures. Improvements can be made effectively.

On the other hand, if the joint is made of the same graded composition material as the member applied in the invention of claim 1, and the joint is interposed between each member, the inclination direction of the material of the joint is Each surface along may be of the same material as each member. Therefore, if such a joint is interposed, it is considered that the joint surfaces of the members will be joined with materials having the same physical properties as described above, and the thermal stress caused by welding or the like can be easily alleviated.

The invention of claim 2 has been made based on such knowledge, and provides a member joining structure in which two or more members made of different materials are integrally joined by welding, brazing or other joining means. , wherein each of the members is joined via a joint made of a graded composition material interposed between them, and the material composition of the joint surface between each of these members and the joint is the same for each joint. shall be.

[0015] Such a configuration also makes it possible to improve high-temperature strength, thermal cycle characteristics, etc., and to effectively improve reliability.

[0016] Even if the composition is a graded composition material, if the thickness along the joining direction is less than a certain level, thermal stress tends to remain in the graded composition portion.

Therefore, in the member joining structure according to claim 1 or 2, the invention as claimed in claim 3 is such that the thickness of the member or joint made of the graded composition material in the joining direction is set within the range where the residual stress due to joining spreads. It is also set to a large value.

[0018] This makes it possible for the member or joint itself made of the gradient composition material to be unaffected by residual stress and to reliably exhibit the thermal stress relaxation effect based on the gradient composition.

[0019]

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

FIG. 1 shows a first embodiment. This example relates to a member joining structure of a structure in which, for example, a PSZ (partially stabilized zirconia) ceramic layer is coated on the surface of a base made of a Ni-based alloy.

As shown in FIG. 1, one member, a block 1 made of a graded composition material, and the other member, a base 2, are joined by a joint 3 such as brazing.

The block 1 is manufactured in the shape of a thick plate by a gradient composition sintering method in which a layered molded body is sintered by gradually changing the material composition. A ceramic region 1a in which PSZ-based ceramics are uniformly distributed is formed at one end of the block 1 in the thickness direction, and a metal region 1b in which Ni-based alloy is uniformly distributed is formed at the other end. A gradient composition region 1c in which the composition of these materials gradually changes is formed in the middle portion (schematically, hatched portion A represents ceramics, and white portion B represents metal).

The base body 2 is homogeneously made of the same Ni-based alloy as the constituent material of the block 1, and is used to constitute walls and other structures.

[0024] The metal region 1b of the block 1 is joined to the surface of the base body 2, and is integrally fixed by a joint 3 such as brazing.

The wall thickness of the block 1 in the joining direction is
It is set larger than the range where residual stress during bonding spreads. In other words, it is known from analysis that the range in which residual stress spreads in a graded composition material of PSZ ceramics and Ni-based alloy is determined by the ratio of the wall thickness T and width W of the block 1, and that range is Since (W/T<80), block 1 has a value greater than or equal to T in this relational expression.
The wall thickness is set.

According to this embodiment configured as above,
Since the material of the joint surface between the block 1 and the base body 2 is made of the same Ni basic alloy, the physical properties such as the coefficient of thermal expansion at the joint surface match and the heat conductivity is improved, so thermal stress can be significantly reduced. It can be relaxed. Therefore, compared to conventional joint structures that connect members made of different single materials, it is possible to improve high-temperature strength, thermal cycle characteristics, etc., and improve reliability, especially when applied to large structures. Improvements can be made effectively.

Furthermore, since the wall thickness of the block 1 made of the graded composition material in the welding direction is set to be larger than the range in which the residual stress due to bonding spreads, the block 1 itself is not affected by the residual stress and the inclination It is possible to reliably exhibit the thermal stress relaxation effect based on the composition.

FIGS. 2 and 3 show a second embodiment. FIG. 2 shows the state before bonding, and FIG. 3 shows the bonded state.

In this embodiment, a pair of rod-shaped members 11 and 12 having different material compositions are integrally joined via a joint 13 by welding. One member 11 is made of stainless steel (for example, SUS304), and the other member 12 is made of Al alloy.

The joint 13 is made of a graded composition material of SUS304 and Al alloy. This joint 13 is manufactured, for example, by a gradient composition sintering method, and has a SUS304 region on one end side in the joining direction, an Al alloy region on the other end side, and a gradient composition region in which the composition of these materials gradually changes in the middle part. ing. The thickness of the joint 13 in the welding direction is set to be larger than the range over which the residual stress at the time of welding spreads. In other words, as a result of analysis, it is known that the range in which residual stress spreads in the graded composition material of SUS304 and Al alloy is determined by the ratio of the wall thickness T and width W of block 1, and that range is (W/ Since T<5), the wall thickness of block 1 is set to be a value greater than or equal to T in this relational expression.

Then, the SUS304 region of the joint 13 is joined to one member 11 made of SUS304,
The Al alloy region of the joint 13 is joined to the other member 12 made of Al alloy, and each joint is fixed by welding.

[0032] Also in this embodiment constructed as described above, the high temperature strength and It becomes possible to improve thermal cycle characteristics, etc., and reliability can be effectively improved.

[0033] In addition to the shapes shown in the above embodiments, the members to be applied in the present invention may have shapes such as round bars, square bars, etc.
It can be applied to various shapes such as a pipe shape.

[0034]

As described above, according to the present invention, in a member joining structure made of different materials, the members themselves or the joints interposed between the members are made of graded composition materials, and the materials at the joining surfaces are made to match. As a result, thermal stress caused by bonding can be significantly alleviated, and high-temperature strength and thermal cycle characteristics can be improved, resulting in a longer service life, and reliability can be effectively improved, especially when applied to large structures. This effect is produced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention before bonding.

FIG. 3 is a diagram of a bonded state according to the embodiment of FIG. 2;

[Explanation of symbols]

1, 2, 11, 12 parts 13 Joint

Claims (3)

[Claims] Claim 1: A member joining structure in which two or more members made of different materials are integrally joined by welding, brazing, or other joining means, in which at least one member is made of a graded composition material, and this member and the other A member joining structure characterized in that the material composition of the joining surface with the member is the same. 2. In a member joining structure in which two or more members made of different materials are integrally joined by welding, brazing or other joining means, each member is a joint made of a graded composition material interposed between them. A member joining structure characterized in that the material composition of the joining surfaces of these members and the joint is the same for each joining part. 3. The member joining structure according to claim 1, wherein the wall thickness of the member or joint made of the graded composition material in the joining direction is set to be larger than the range in which residual stress due to joining spreads.