JP2801735B2 - Joint of ceramics and metal and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention functions from structural materials using ceramics such as rocker arms, tappets, engine parts such as turbocharger rotors, tools such as cutting tools, and electronic parts. The present invention relates to a joined body of ceramic and metal that can be widely used for materials.

[Prior art and problems] One of the joining methods of ceramics and metal is a brazing method using a brazing material. However, ceramics have a smaller coefficient of thermal expansion than metals, and silicon nitride, silicon carbide, etc., which have recently attracted attention as structural materials, have a particularly small coefficient of thermal expansion among ceramics. Therefore, in the simple brazing method, ceramics are easily broken in a cooling process after the brazing process due to a difference in thermal expansion.

Therefore, various improvements have been proposed for the brazing method.
Bonding to reduce the above thermal expansion difference by interposing a buffer layer of Kovar, molybdenum, tungsten, etc.
4) In addition, a joint (JP-A-61-127674) in which a low-expansion metal (a metal mainly composed of W and Mo) and a low Young's modulus metal (eg, Cu, Ag, Ni) are interposed as a buffer layer. Filed. On the other hand, as a brazing material, an active solder containing Ti has good reactivity with ceramics, and an active solder containing In in addition to Ti has good reactivity and can be joined at low temperature. Therefore, for example, an Ag-Cu-In-Ti-based brazing material is known as a suitable material.

However, at least Ti and
When ceramics and metal are joined using an active brazing filler metal containing In, the reactivity (wetting) between the ceramic and the active brazing filler metal deteriorates, and a problem arises in that sufficient bonding strength cannot be obtained.

[Means for Solving the Problems and Action] In view of the above problems, the present inventor has investigated the causes. In the case where Cu, Ni, or the like is interposed, the Ti of the active brazing filler metal is insufficiently chemically reacted with the ceramics. I knew it would come. The cause is not clear, but it is probably because most of the Ti that should react with the ceramics was consumed in the reaction with the buffer material. Therefore, as a result of further intensive studies on the bondability between metal and ceramics using various other metal materials and various brazing materials, a specific iron-based buffer material was interposed, and at least
When using brazing material containing In and Ti, especially Ag-Cu-In-Ti brazing material, not only does the ceramic not crack during cooling after heat bonding, but the resulting bonded body can exhibit extremely high bonding strength. And have completed the present invention.

That is, the joined body of the present invention is a joined body in which a cushioning material is interposed between a ceramic and a metal, and a joint between the ceramic and the cushioning material, and between the metal and the cushioning material. The shock absorbing material is a shock absorbing material mainly composed of iron and having a Vickers hardness (Hv) of 170 or less after joining, and the joining member is a joining member containing at least In and Ti. I do.

The cushioning material can be pure iron or carbon steel. Further, the thickness of the cushioning material can be in the range of 0.4% to 10% of the maximum diagonal length or the maximum diameter of the bonding surface between the ceramic and the metal.

In addition, the method for manufacturing a joined body according to the present invention is characterized in that a buffer material having iron as a main component and having a Vickers hardness (Hv) of 170 or less after joining is interposed between a ceramic and a metal, so that at least In and Ti And bonding between the ceramic and the cushioning material and between the metal and the cushioning material, respectively, by using a joining member including:

Heretofore, it has not been known at all that a material containing iron as a main component as a cushioning material, and in particular, its use alone is not known. In the present invention, the reaction between ceramics and a joining member is inhibited by using the iron-based cushioning material. Without reducing the residual stress due to the difference in thermal expansion between the ceramic and the metal, cracking of the ceramic during cooling is prevented and high bonding strength is maintained.

As the iron-based buffer material, the one with less impurities is softer and effectively exerts a stress buffering action. Therefore, pure iron is preferred. In this case, some of the pure iron may be work-hardened by rolling or the like, but may be used because it is usually annealed and softened by a heat treatment at the time of joining. However, even for general steel materials such as carbon steel and alloy steel, the Vickers hardness (Hv) is at least 17 after the heat treatment at the time of joining.
Anything below 0 is valid.

That is, it is possible to use not only Hv 170 or less before the heat treatment at the time of joining but also Hv 170 or less, which is softened by the heat treatment at the time of joining even if it is Hv 170 or more before the heat treatment at the time of joining. Further, in some cases, a steel material having a Hv of 170 or less can be used by separately annealing after the heat treatment at the time of joining. Therefore, low carbon steel (carbon content 0.15% or less) and medium carbon steel (0.15% to 0.15%)
40%) can be preferably used. Specifically, rolled steel for general structures (JIS G 3101 “SS” series), carbon steel for machine structures (JIS G 3101
4051 "S" type) can be used. In this case, it is needless to say that a small amount of silicon, manganese, phosphorus, sulfur and the like may be contained.

On the other hand, those containing elements that increase the quenching effect in the heat treatment at the time of joining, for example, Cr, Mn, Ni, and Mo are not preferable. Therefore, alloy steels that have high hardenability and are easily quenched by heat treatment during joining, such as chromium molybdenum steel (JIS SCM) and nickel chromium molybdenum steel (JIS SNCM) with a large amount of chromium, are hardened by heat treatment during joining. Therefore, a stress buffering action cannot be expected. Incidentally, such iron-based cushioning materials may be used in combination of different compositions.
In addition, as long as a predetermined iron-based cushioning material exists, it is acceptable to use a W and Mo-based cushioning material separately.

The thickness of the iron-based cushioning material is preferably about 0.4% or more and 10% or less of the maximum width (diameter) of the joint surface between the metal and the ceramic.
Of course, as long as it is within the range, a plurality of sheets may be present.

The joining member used in the present invention is a Ti-In type, particularly an Ag-Cu-In-Ti type, that is, Ag, Cu, In, Ti as an essential component, and the total amount of these components is 99% by weight of the whole. The above are preferred. This Ag-Cu-In-Ti-based brazing filler metal has sufficient reactivity with ceramics and has high bonding strength.
Moreover, despite the inclusion of the Ti component, it has the advantage that the melting point is relatively low and the energy cost is low. In the present invention, a predetermined iron-based material is used as the cushioning material as described above.
The advantages of the Ag-Cu-In-Ti-based active brazing filler metal, in particular, high reactivity with ceramics can be effectively exhibited. This Ag-Cu-In-Ti
As the brazing material, a material in which the ratio of each element is 90% by weight of Ag, 50% by weight of Cu, 50% by weight of Cu, 10% by weight of In, and 10% by weight of Ti is preferably used.

In addition, other than the Ag-Cu-In-Ti type, other Ti-In type active materials can be used as long as they have excellent reactivity with ceramics and can effectively exhibit the effect of reducing the thermal expansion difference by the iron type buffer material. It is also possible to use a brazing material according to the application and purpose. In this case, in consideration of the effects of the brazing treatment on the iron-based buffer material, that is, quenching hardening and softening (annealing, normalizing, etc.), the melting point of the Ti-In-based brazing material and the Adjustment of the composition is necessary for the buffer material having the predetermined hardness to effectively exhibit the effect of reducing the thermal expansion difference. Therefore, the melting point of the Ti-In brazing material is 600-800.
° C, more preferably about 700 to 780 ° C.

The shape of such a Ti-In-based active brazing material may be foil, paste, or a combination of foil and paste, such as Ti foil and AgCu.
Any material such as In alloy foil and TiAgCuIn paste can be used.

Regarding the heat treatment conditions at the time of joining, heating may be performed at a temperature higher than a temperature at which a brazing material as a joining member can be melted, and varies depending on a difference in the composition of the brazing material. On the other hand, the upper limit of the heating temperature is set in consideration of softening of the iron-based cushioning material. Usually 700
The temperature may be set in a range of 10 minutes to 2 hours at a temperature of 900 ° C. The atmosphere is preferably a non-oxidizing atmosphere such as a vacuum or an inert gas (such as argon) in order to sufficiently react the Ti as a brazing material with the ceramic. The cooling method is preferably furnace cooling and air cooling, and oil cooling and water cooling are not preferable because ceramics are vulnerable to thermal shock.

Ceramic materials include Ti-In, especially Ag-Cu-In, such as silicon nitride, silicon carbide, sialon, alumina, and mullite.
Any material that can be joined with a Ti-based active brazing material may be used.

The metal material may be any material having a larger coefficient of thermal expansion than ceramics such as structural alloy steel, nickel chrome molybdenum steel, Kovar, and nickel. In this case, the thickness of the iron-based cushioning material may be adjusted according to the type of metal or ceramic to be joined.

[Example] Example 1 Silicon nitride having a diameter of 12 mm and a length of 20 mm (90 wt% Si ₃ N ₄ balance sintering aid), a metal having a diameter of 12 mm and a length of 20 mm (JIS SNCM630), a diameter of 12 mm and a thickness of 0.25 mm Various buffer materials (Purities of 99% or higher for Fe, Ni and Cu, other materials are JIS standard) and activated brazing foil (Ag 60% by weight, Cu27, In12.5, Ti1.5) with a diameter of 12mm and a thickness of 0.05mm. As shown in FIG. 1, three pieces each were heated and bonded at 780 ° C. for 30 minutes in a vacuum. The cooling after the heating was performed at a speed of 20 ° C./min with N ₂ gas sealed.

Then, as shown in FIG. 2, while holding the metal, the cantilever bending strength was measured, the bending strength was determined by the following equation 1, and the average value of the three pieces is shown in Table 1. Note that l = 10 mm. The hardness of the cushioning material was measured at a load of 10 g using a Vickers hardness tester after cutting the joint and polishing the cut surface.

(Equation 1): σ: Bending strength (kg / mm ² ) P: Breaking load (kg) l: Span (mm) d: Joint diameter (mm) π: Pi SS34, S15C, which does not harden by brazing other than pure iron,
S40C (Hv 170 or less) was found to have a stress buffering effect. On the other hand, it was found that materials with Hv of 230 or more had no stress buffering effect.

Example 2 Table 2 shows the results of joining and measuring the strength under the same conditions as in Example 1 except that the thickness of the pure iron was changed.

The buffer effect was observed even when the thickness of pure iron was reduced to 0.42% of the joint diameter. When the thickness of pure iron was increased to 16.7% of the joint diameter, bending was visually observed with a stress of 15 kg / mm ² .

Example 3 Table 3 shows the results of measuring the strength by joining under the same conditions as in Example 1 except that the composition of the active brazing material was changed. The composition of the active brazing material is (Ag 59% by weight, Cu26, In12.5, Ti2.5).

Even if the Ti content of the Ag-Cu-In-Ti-based brazing filler metal is increased, Ni, C
The effect of the present invention was confirmed when the Fe-based buffer material was used as compared with the u-buffer material, because the bonding strength was larger.

[Effects of the Invention] According to the present invention, it is possible to provide an extremely strong bonded body of ceramics and metal which can be easily obtained by using a Ti-In-based active brazing material.

As the iron-based cushioning material, a general steel material other than pure iron can be used, and by selecting an appropriate material according to the joining metal and ceramics, it can be applied to a wide range of joined bodies.

The advantages of Ti-In-based, particularly Ag-Cu-In-Ti-based brazing materials can be fully utilized. In other words, it has sufficient reactivity with ceramics and can increase the bonding strength, and on the other hand is not so high in melting point, which is advantageous in energy cost.

If the joined body of the present invention is applied to the following joined body and joining method, it is possible to apply to a large-sized component and to improve the reliability of the joined portion. That is, the joined body is a joined body of a ceramic body and a metal body which joins a ceramic body and a metal body via a brazing material layer, and the brazing material layer has a solidus point of 700 ° C or less. The metallic body is composed of a pearlite transformation, a normal pearlite transformation (Ar ₁ ), and a supercooled pearlite transformation (Ar ₁ ) that occurs at a temperature lower than the normal pearlite transformation (Ar ₁ ) point after austenite is supercooled. ')including. ｝ Consists of a material generated below the solidus point of the raw material or a material in which the pearlite transformation is inhibited, and the metal structure after joining is at least one of a supercooled structure and a martensitic structure except pearlite in a narrow sense. A joined body of a ceramic body and a metal body, which is characterized by being composed of a structure.

In addition, the joining method is such that a solid point between the ceramic body and the metal body made of the above-mentioned metal material is 70 ° between the desired joining surfaces.
A raw material having a temperature of 0 ° C. or less is placed, and these are transformed to the austenite transformation above the solidus point. Thereafter, the cooling rate is 0.1 to 200 at least near the point A ₁ (including the above Ar ₁ and Ar ′). The pearlite transformation is caused below the solidus point or the pearlite transformation is prevented by cooling them by air / air cooling at a rate of ° C./sec, and the displacement difference between the expansion and contraction of the ceramic body and the metal body is reduced. It refers to a method of joining a ceramic body and a metal body, which is characterized by being reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a joined body according to an embodiment of the present invention before joining, and FIG. 2 is a schematic diagram for explaining a test method for examining joining strength (bending strength). Express. 1 ... joining member (brazing material) 2 ... cushioning material

Claims (4)

(57) [Claims] 1. A joined body in which a cushioning material is interposed between a ceramic and a metal, and the ceramic and the cushioning material and the metal and the cushioning material are respectively joined by a joining member, The joined body is characterized in that the shock absorbing material is a shock absorbing material having iron as a main component and a Vickers hardness (Hv) of 170 or less after joining, and the joining member is a joining member containing at least In and Ti. 2. The joined body according to claim 1, wherein the cushioning material is pure iron or carbon steel. 3. The joined body according to claim 1, wherein the thickness of the cushioning material is in the range of 0.4% to 10% of the maximum diagonal length or the maximum diameter of the joining surface between the ceramic and the metal. 4. A joining member containing at least In and Ti is interposed between a ceramic and a metal with a buffer material having iron as a main component and having a Vickers hardness (Hv) of 170 or less after joining. , Between ceramic and cushioning material, and
A method for producing a joined body of a ceramic and a metal, wherein the joined body is heated and joined between the metal and the cushioning material.