JPH09295876A - Brazed bonded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal resistance and shock resistance without using an independent buffer plate by making a brazing material layer thicker at a site near the outer periphery including the outer peripheral edge of the brazed bonded surface than a site near the center from the site near the outer periphery. SOLUTION: An outer peripheral site W having a specific width on a bonding surface 2a is finished with a specific taper against the bonding surface 2a formed on a plain surface near the center so that the thickness of a brazing material layer 4, at a site near the outer periphery including the outer peripheral edge 2b of the brazed bonding surface 2a of a metallic material 2 having a diameter D and a length L, is made thicker than the thickness of a brazing material layer 4 at the site near the center inside the outer peripheral site W. A specific foil shaped brazing material and an ceramic member 3 are placed on the bonding surface 2a of the metallic member 2, and they are brazed so that the thickness of the brazing material layer 4 near brazed the center is 5-50μm, and the difference between the minimum thickness of the brazing material layer 4 at a site near the center and the maximum thickness of the brazing material layer 4 at a site near the outer periphery is 10-150μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazed joint body in which a metal member and a ceramic member are joined by brazing, and more specifically, it is used for an engine tappet, a rocker arm, other engine parts, tools and the like. The present invention relates to a brazed joint body (hereinafter, also simply referred to as a joint body) of a metal member and a ceramic member.

[0002]

2. Description of the Related Art Ceramics have excellent properties such as heat resistance and thermal shock strength, and are therefore suitable for use as parts that are subjected to shock loads in a high temperature atmosphere. However, the ceramic is rarely used alone and is usually used as a brazed joint with a metal member. By the way, the thermal expansion coefficient of metals such as carbon steel, nickel chrome molybdenum steel, and SUS304 is 11 × 10 ⁻⁶ / ° C. to 17 × 10 ⁻⁶ / ° C., while sialon and silicon nitride (Si 3 N 4 ), silicon carbide (SiC), alumina (Al2 O3) thermal expansion coefficient of the ceramic or the like, 3 × 10 ^-6 /℃~4.5×10 ^-6 /
It is as small as ℃, and the difference is remarkably different.

In such a brazed joint body having a large difference in coefficient of thermal expansion, it is preferable to set the brazing material layer thicker when heat resistance is important. If a large thickness of the brazing material layer is secured, the brazing material layer itself can absorb (buffer) stress due to the difference in thermal expansion coefficient, causing cracking or peeling of the ceramic during the brazing process or high temperature atmosphere. This is because it is effective in prevention. On the other hand, when impact resistance is important, it is preferable to set the brazing material layer thin. This is because if the brazing material layer is thick, it is soft and easily deformed, so that when the ceramic is subjected to an impact load, the ceramic may be cracked. As can be understood from the above, in a bonded body having a large difference in thermal expansion coefficient such as metal and ceramic, the thickness of the brazing material layer must be appropriately set according to the performance required for the bonded body.

By the way, the joined body is required to have both heat resistance and impact resistance as in the case where the joined body is, for example, an engine tappet, and the cam contact surface is a ceramic member which is brazed to a metal body. There are things. Conventionally,
Such a bonded body should be designed with emphasis on either of them, or with an emphasis on intermediate performance, or between them, such as a copper (Cu) plate or a nickel (Ni) plate. A design has been made in which a soft metal is interposed as a cushioning material to absorb the stress caused by the difference in thermal expansion coefficient.

[0005]

However, if the brazing material layer is set thicker in consideration of heat resistance, the effect of absorbing the stress caused by the difference in the coefficient of thermal expansion becomes large. It is unavoidable that the brazing material layer near the center of the joint surface, which is subjected to the collision, is easily deformed and the impact resistance of the ceramic is lowered. On the other hand, if the brazing material layer is set thinner, the deformation of the brazing material layer itself due to impact load is small, but the absorbing effect of the stress due to the difference in thermal expansion coefficient becomes insufficient, and therefore, during brazing or under high temperature atmosphere. However, there remains a problem that peeling or cracking is likely to occur in a portion near the outer periphery of the ceramic member where the stress is maximum.

As described above, in a joined body that is exposed to an impact load under high heat, such as an engine tappet, both joining surfaces of the metal member and the ceramic member are formed into a single plane, and the brazing material layer is formed. If you keep it to a certain thickness,
Only heat resistance or impact resistance can be ensured, and performance is insufficient. In addition, when a soft metal such as a copper plate is interposed as a cushioning material between the two to absorb the stress caused by the difference in thermal expansion coefficient, a cushioning material is additionally required, and the cushioning material itself is required. To be soft,
Impact resistance is still insufficient.

Under these circumstances, the inventor of the present invention conducted various tests by changing the thickness of the brazing material layer on the joining surface of the tappet, and found that the brazing material layer was thickened only at the outer peripheral portion, It has been found that the heat resistance can be increased without impairing the impact resistance. The present invention has been made on the basis of such findings, in a joined body in which members having greatly different thermal expansion coefficients such as ceramic and metal are joined by brazing, without using an independent buffer plate, and It is an object to provide a brazed joined body having excellent heat resistance and impact resistance.

[0008]

In order to achieve the above object, the present invention provides a brazing joint body in which a metal member and a ceramic member are joined by brazing, and includes an outer peripheral edge of a brazing joint surface. The thickness of the brazing material layer at the outer peripheral portion is thicker than the thickness of the brazing material layer at the central portion than the outer peripheral portion.

Due to the difference in the coefficient of thermal expansion, the stress generated at the time of brazing or at a high temperature becomes large at the outer peripheral portion of the joint surface. On the other hand, in the above-mentioned means, since the brazing material layer is thick at the outer peripheral portion where the stress increases,
The stress in the portion near the outer periphery is effectively absorbed. That is, by making the brazing material layer thicker only in the outer peripheral portion relative to the central portion, the heat resistance during brazing and in the process of use can be reduced without lowering the impact resistance required for the central portion. It is possible to obtain a joined body that is excellent in the performance of absorbing the stress caused by the change.

The thickness of the brazing material layer near the center of the brazing joint surface (hereinafter also simply referred to as the joint surface) depends on the impact resistance required for the joint, but is generally 5 ~ 5
0 μm is appropriate, and the difference between the minimum thickness of the brazing material layer at the central portion and the maximum thickness of the brazing material layer at the peripheral portion is 10 to 150 μm. If the maximum thickness of the portion near the outer periphery is 15 μm or less, the effect of absorbing stress due to the difference in thermal expansion coefficient cannot be expected, while if it exceeds 200 μm, the filling property of the brazing material layer may be reduced, and pores may be included. This is because there is a high risk that brazing will not be performed normally, such as when there is a risk of damage. In the case of joining by brazing, a diffusion layer which is neither a pure brazing material nor a pure metal or ceramic is provided between the brazing material layer and the metal member or ceramic member forming the joined body (interface). In the present specification, the thickness (numerical value) of the brazing material layer means the diffusion layer existing between the brazing material layer and the metal and the diffusion existing between the brazing material layer and the ceramic. The measured value of the brazing material layer itself, which does not include the layer. The thickness of the brazing material layer is shown in unit of μm.

The shape of the brazing joint surface is typically exemplified by a circle, an ellipse, or a polygon such as a substantially square or a rectangle. In this case, the brazing surface is formed to be thicker at the outer peripheral portion. The width of the brazing material layer is 5 to 30% with respect to the maximum outer diameter dimension or the maximum diagonal dimension of the brazing joint surface.
It is good to If this ratio is less than 5%, the effect of absorbing stress due to the difference in thermal expansion coefficient cannot be achieved, while if this ratio is more than 30%, the area in which the brazing material layer is easily deformed by impact load increases too much, This is because the impact resistance decreases. It may be designed as appropriate according to the required heat resistance, impact resistance, etc., but it may be set smaller when the difference in thermal expansion coefficient is small and larger when it is large.

For example, in the case of a joined body of silicon nitride (Si3 N4) or alumina ceramic (Al2 O3) and nickel chrome molybdenum steel (SNCM630), the above ratio is preferably 5 to 20%. is there. By the way,
Si3 N4, Al2 O3, the thermal expansion coefficient of SNCM630, respectively ^{3 × 10 -6 /℃,4.5×10 -6 / ℃} , 1
It is 1 × 10 ⁻⁶ / ° C. On the other hand, these ceramics and S
As in US304 (coefficient of thermal expansion 17 × 10 ⁻⁶ / ° C.),
If the difference in coefficient of thermal expansion is significantly different,
15-30% is suitable.

In each of the above means, at least one of the metal member and the ceramic member is formed so that the thickness of the brazing material layer in the region near the outer periphery is greater than the thickness of the brazing material layer in the region near the center. It is advisable to form the portion near the outer periphery in a stepped shape. In this case, when only one of the outer peripheral portions is formed in a stepped shape, the other brazing bonding surface may be a single flat surface, or the outer peripheral portion thereof may have a thickness of the brazing material layer. May be formed in a tapered shape so that the thickness increases toward the outer peripheral edge. Further, in each of the above means, at least one of the metal member and the ceramic member is tapered so that the thickness of the brazing material layer in the outer peripheral portion increases toward the outer peripheral edge. You may form in. In this case, when only one outer peripheral portion is formed in a tapered shape, the other brazing bonding surface may be a single flat surface, or the outer peripheral portion may be formed to have a thickness of the brazing material layer. May be formed in a stepped shape so that the thickness is thicker than the thickness of the brazing material layer in the central portion.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which a joined body according to the present invention is embodied will be described in detail with reference to FIGS. However, the joined body 1 in this example is a model of a tappet for an engine, and a ceramic member (thin plate) 3 forming a cam contact surface is brazed to a metal member 2 forming a tappet body. The metal member 2 is JIS
SNCM630 with a diameter D of 30 mm and a length L of 50
It is formed into a cylindrical shape of mm and has a joint surface (end surface) 2a of Ra (center line average roughness) 0.4 μm.
The thickness of the brazing material layer 4 at the outer peripheral portion including the outer peripheral edge 2b of the brazing joint surface 2a is greater than the thickness of the brazing material layer at the central portion inside the outer peripheral portion. In this example, a predetermined width portion W on the outer periphery of the joint surface 2a is finished with a predetermined taper with respect to the joint surface 2a formed on the plane (flat) of the portion closer to the center of the joint surface 2a. The ceramic member 3 is a silicon nitride (90 wt% Si3 N4, residual sintering aid) sintered body or an alumina (Al2 O3 90 wt% residual sintering aid) sintered body, and both surfaces are flat (flat). It is a disk-shaped thin plate with a diameter of 30 mm and a thickness of 2 mm that is polished to a surface, and its joint surface 3a has a Ra (center line average roughness) of 0.3 μm.
It is finished.

In the joined body 1 in this example, a predetermined foil-shaped brazing material is placed concentrically on the joining surface 2a of the metal member 2, and the ceramic member 3 is placed on the brazing material.
The brazed body 1 was maintained at 30 ° C. for 30 minutes and cooled by N 2 gas displacement to obtain a brazed joint 1. However, in this example, the maximum thickness T1 of the brazing material layer 4 at the outer peripheral portion formed to be thick is
70 μm (± 10), the thickness T2 of the central portion (flat portion) is set to 20 μm (± 10), and the difference is 50 μm. However, in this example, the brazing material is an In-Ti-Cu-Ag system (In; 15%, T) formed to have a diameter of 30 mm and a thickness of 0.07 mm (70 μm).
i; 1%, Cu; 23%, Ag; 60%).

In the bonded body 1 of the present example as described above, the thickness of the brazing material layer 4 at the central portion (planar portion) of the joint surface is
The thickness is 10 to 30 μm to secure the bonding strength, and the maximum thickness of the outer peripheral portion is 60 to 80 μm. Therefore, the stress that is a problem during brazing due to the difference in the thermal expansion coefficient can be easily adjusted by the thick portion. It is absorbed and brazed without problems. The thermal stress generated when used in a high-heat atmosphere is also absorbed by the thick portion of the brazing material layer, so that the ceramic 3 can be effectively prevented from peeling even without the buffer material. Further, since the thickness of the portion near the center which is in charge of the cam contact surface, that is, the flat portion of the brazing joint surface is set to about 20 μm, there is no problem in impact resistance.

Hereinafter, in the above-mentioned basic form, each member sample in which the cross-sectional shape of the brazing bonding surface of the metal member 2 (SNCM 630) and the ceramic member 3 (silicon nitride or alumina) was changed near the outer periphery was used. One sample of each joined body (joined body sample) was prepared by combining, and only one cross-sectional shape of the thick portion of the brazing material layer 4 was different, and each joined body sample was tested for heat resistance and impact resistance. However, the cross-sectional shape and dimensions showing the brazed joint surface 3a of the ceramic member 3 used in this test are as shown in the model in Table 1. No. 1 is the one where the entire joint surface 3a is flat,
o. 2 is the one in which the central portion of the joint surface 3a is flat and the outer peripheral portion is formed in a taper shape. Further, in No. 3, the central portion of the joint surface 3a is flat and the outer peripheral portion is stepped. Those formed (recessed) are shown respectively.

[0018]

[Table 1]

On the other hand, the cross-sectional shape and dimensions showing the brazed joint surface 2a of the metal member 2 are as shown in the model in Table 2. No. 1 is the one where the entire joint surface 2a is flat,
For No. 2, the joint surface 2a has a flat central portion, and the outer peripheral portion has a tapered shape. Further, No. 3 has a flat central portion of the joint surface 2a and a stepped outer peripheral portion. These are formed respectively. No. in Table 2
The step t of 3 and the width w thereof were appropriately changed and tested.

[Table 2]

The contents of the heat resistance and impact resistance tests are as follows. In the heat resistance test, the joined body sample is left in a furnace at 300 ° C. for 100 hours to generate stress due to the difference in thermal expansion coefficient between the ceramic and the metal, which promotes the peeling of the ceramic, and the peeling causes the entire area of the joint surface to grow. Was measured up to 50%. After 100 hours, if the peeling is 50% or less, the result is good (○), and in other cases, it is bad (X).
And The attached number in each table showing the test results is 50%
It is the elapsed time when peeling occurs.

In the impact resistance test, a cylindrical cemented carbide pin having a diameter of 10 mm and a length of 30 mm is placed on the surface of the sample on the ceramic member side in the diameter direction of the surface, and the ceramic member is impacted through the pin. An impact test of applying a load was performed to measure the load at which the ceramic cracked. 70
The case of 00 kg or more was regarded as good (marked with ◯), and the other cases were judged as defective (marked with ×). The attached number in each table showing the test results is the load when the ceramic cracks.

Test Example 1 The ceramic member is silicon nitride (Si3 N4), the joint surface is the flat surface in Table 1, and the metal member is the flat surface in Table 2 (comparative example), tapered or stepped. Then, each bonded sample (Sample Nos. 1 to 8) was prepared and tested. The test results are shown in Table 3. In this test, the level difference t of the metal member sample in Table 2 is 0.008 to
0.2 mm (8 to 200 μm), and its width w is 5
mm. Further, the thickness of the brazing material layer at the central portion (the entire surface in the comparative example) is set to 20 μm (± 10).

[Table 3]

As can be seen from these results, the brazed joint sample (Comparative Example) in which the joint surfaces of the sample No. 1 are flat members is strong in the impact test, but the stress absorbing action is insufficient. In the heat resistance test, the ceramic member peeled off in a short time. In addition, the comparative example of sample No. 2 has a thickness of 0.3 mm.
However, the ceramic plate did not peel off, but because the copper plate was soft, the impact performance was low, and the copper plate was broken at a load of about half the standard value. On the other hand, in the case of the joined body samples within the scope of the present invention (Sample Nos. 3 to 8), good results were obtained in almost all of the heat resistance test and the impact test.
The metal member of Sample No. 4 is stepped and the step t is 0.0
In the case of 08 mm (8 μm), since the stress absorbing effect is not always sufficient, the ceramic member peeled off in 8.5 hours, but still the heat resistance of 60% or more higher than that of the comparative example of Sample No. 1 was recognized. Further, when the metal member of Sample No. 8 is stepped and the step t is 0.2 mm (200 μm), the impact resistance is inferior, but it is still superior to the case where the copper plate is interposed. From this result, it can be said that t is in a suitable range of 10 to 150 μm in the present joined body sample.

Test Example 2 Next, the ceramic member is silicon nitride (Si3 N4),
The joining member is a flat member sample in Table 1, and the metal member is a step member in Table 2 (the step t is 0.02 mm (20 μm
m)), the width (width of the thick portion of the brazing material layer) w was changed with respect to the outer diameter D (30 mm) of the bonding surface to prepare bonded samples (Sample Nos. 9 to 13). Was tested. The results are as shown in Table 4.

[Table 4]

As can be seen from these results, good results were obtained for almost all of the heat resistance test and the impact test under the test conditions. Of these, if w / D is 3%,
In the heat resistance test, the ceramic member peeled off in 13 hours, but it was still 120% or more superior to the comparative example of Sample No. 1. Further, when w / D is 33%, the impact resistance is inferior, but still higher performance is recognized than when a copper plate is interposed. From this result, the w / D was 5 in this conjugate sample.
It can be said that -30% is an appropriate range.

Test Example 3 Further, the ceramic member is silicon nitride (Si3 N4)
The cross-sectional shape of the joint surface is the tapered or stepped one in Table 1, and the metal member is the flat, tapered or stepped cross-sectional shape in Table 2, and the joint sample (Sample No. 1
4-19) were made and tested for each. The results are as shown in Table 5. Note that the step t of the stepped metal member is
Is 0.02 mm (20 μm) and its width w is 5 m
m.

[Table 5]

As can be seen from these results, good results were obtained for all the samples. At the same time, from the above results,
It is preferable that either the ceramic member or the metal member is stepped or tapered in the outer peripheral portion, and the brazing material layer in the outer peripheral portion has a large thickness. It turns out that the result is obtained.

Test Example 4 Next, the ceramic member was alumina (Al2O3), and the cross-sectional shape of the joint surface was flat, tapered or stepped in Table 1, and the metal member was flat, tapered or tapered in Table 2. Each of the stepped cross-sectional shapes has a joint sample (Sample No. 20
~ 28) were made and tested for each. The results are as shown in Table 6. The step t of the metal member is 0.
It is 02 mm (20 μm) and its width w is 5 mm.

[Table 6]

In the comparative example of sample No. 20, the ceramic member was cracked in the brazing process, while good results were obtained in all the tests with the other joined sample within the scope of the present invention. It was This proves the effect of the present invention. It is considered that the cause of the crack in the comparative example of Sample No. 20 was that it could not withstand the stress generated due to the difference in the coefficient of thermal expansion during brazing because the strength of Al2O3 was low and the Young's modulus was high.

INDUSTRIAL APPLICABILITY The present invention is applicable to tools, electronic parts, etc., including parts for which heat resistance and impact resistance are strongly required, such as those in which the metal member is the engine tappet body and the ceramic member forms the cam contact surface. Available. Naturally, the joined body (structure) according to the present invention is not limited to one having two members, and one having a composite structure including three or more members such as metal-ceramic-metal or ceramic-metal-ceramic. Can also be applied. The brazing material is not limited to the active brazing material, and various brazing materials having various compositions can be used.

[0031]

As is apparent from the above description, the present invention is a brazed joined body of members having greatly different thermal expansion coefficients, such as ceramic and metal, and has a thickness of the brazing material layer on the joined surface. Since the outer peripheral portion is thicker than the central portion, the stress in the outer peripheral portion of the ceramic due to the difference in thermal expansion coefficient can be reduced without using an independent buffer plate such as a copper plate. . Therefore, cracking or peeling of the ceramic in the brazing process or in a high-temperature atmosphere is effectively prevented. Since the thick portion of the brazing material layer is only the portion near the outer circumference, the impact resistance is hardly impaired. That is, according to the present invention, a brazed joint having excellent heat resistance and impact resistance can be formed, and in a joint such as a tappet or rocker arm that requires heat resistance and impact resistance, There are some remarkable effects.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of an embodiment of a brazed joined body embodying the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

[Description of Reference Signs] 1 joined body 2 metal member 2a brazing joint surface of metal member 2b outer peripheral edge of brazing joint surface of metal member 3 ceramic member 3a brazing joint surface of ceramic member 4 brazing material layer

Claims (5)

[Claims] 1. In a brazed joined body obtained by joining a metal member and a ceramic member by brazing, the thickness of the brazing material layer at the outer peripheral portion including the outer peripheral edge of the brazing joint surface is the outer peripheral portion. A brazed joint body, wherein the brazed joint body is formed to be thicker than the brazing material layer in a portion closer to the center. 2. The thickness of the brazing material layer near the center is 5
2. The brazing according to claim 1, wherein the brazing material layer has a thickness of ˜50 μm, and a difference between the minimum thickness of the brazing material layer at the central portion and the maximum thickness of the brazing material layer at the peripheral portion is 10 to 150 μm. Zygote. 3. The width of the brazing material layer formed thickly in the portion near the outer periphery is 5 to 30% with respect to the maximum outer diameter dimension or the maximum diagonal dimension of the brazing joint surface. The brazed joint body according to claim 1 or 2. 4. The thickness of the brazing material layer near the outer periphery is greater than the thickness of the brazing material layer near the center.
The brazed joint body according to claim 1, wherein at least one of the metal member and the ceramic member, which is near the outer periphery, is formed in a stepped shape. 5. The tapered portion of at least one of the metal member and the ceramic member is tapered so that the thickness of the brazing material layer in the outer peripheral portion increases toward the outer peripheral edge. Claim 1 characterized by the above.
The brazed joint body according to 3 above.