JPS62167833A - Thermal expansion regulated alloy for ceramic brazing - Google Patents

Abstract

PURPOSE:To obtain alloy capable of brazing low thermal expansion and dense ceramic without deteriorating strength so much, by setting components ranges in Fe-Co-Ni alloy to that indicated by specified regions in ternary compsn. diagram of Fe, Co and Ni. CONSTITUTION:Components of Ni, Co are prescribed into underside range to a boundary line ab of an inequality IV in wt%. Since thermal expansion coefft. at cooling suppressed to 4.0X10<-6>/ deg.C even in max. is desired for joining with ceramic having low expansion coefft., a region between lines bc or ae, i.e., component ranges of Ni and Co satisfying inequalities V and I is prescribed. Further, as range capable of causing gamma alpha transformation at 750 - about 900 deg.C being brazing temp., region above lines ed and dc, i.e. component ranges of Ni and Co satisfying inequalities III and II is prescribed. Alloy composed of Ni, Co in a range A surrounded by abcde, with the balance Fe is the aimed alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal expansion adjustment alloy that can be brazed to dense ceramics that have a much smaller coefficient of thermal expansion than 1203 ceramics and are relatively strong.

Conventionally, to braze metal to ceramics.

Select metals or alloys with matching thermal expansion coefficients as much as possible to minimize the thermal stress that occurs due to the difference in thermal expansion coefficients during the cooling process during brazing, or It has been devised to absorb the distortion caused by this thermal stress by sandwiching a fairly flexible metal such as silver or aluminum as an intermediate buffer material.

However, in recent years, carbide-based materials have been developed that have relatively excellent mechanical properties, high strength, and a small coefficient of thermal expansion.

As a nitride ceramic, for example, pressureless sintered SiC
, reaction sintered 8iC-8i + pressureless sintered 8i3N4 + pressureless sintered AeN, and other ceramic sintered bodies have been developed, and metals and alloys with small thermal expansion coefficients that can be brazed to these ceramics have been developed. We have been under pressure to develop. The metal with the smallest coefficient of thermal expansion in the rising silver brazing temperature range of room temperature to 800°C is W, and its value is 4.
It is about 5 x 10-'/'C, Sic,
8 to-8i Arui wa All'N'! (M!'!
It can barely be used for brazing ceramic sintered bodies whose expansion coefficient is within the range of 4 to 5 x 10-6/'C. However, W is extremely hard and brittle.

It is not a satisfactory material because it has poor flexibility and tends to leave strain in the joint, and it is also poor in resources and expensive. Also, 17.0% by weight of Co, which is conventionally known as a bonding alloy for Ae203 ceramics.

Kovar alloy, which is composed of 29.0% by weight Ni and the balance substantially Fe, has a thermal expansion coefficient of about 4.8 x t o-'/''c even in the temperature range from room temperature to 430°C, and has a thermal expansion coefficient of about 4.8 average of 8.8 x 10-'/”
C, it is difficult to apply it to ceramics with low thermal expansion as described above.

The present invention has been made in view of these circumstances, and
Ceramics with a small coefficient of thermal expansion of s, ox t o-'/"c or less have high strength, and have a transverse rupture strength of 20 of 9/- or more and have relatively poor strength compared to ceramics with M[J" The objective is to provide an alloy that can be brazed without any problems.

The thermal expansion adjustment alloy for ceramic brazing of the present invention has a range shown as a region in FIG.

40%≦Ni%+CO%, 24.0%≦Ni%, Ni%
+0.47 Co%≧340%, 81%+0.3Go
%≦34.5% 81%+0.58Co%≦37.8%. . However, the total amount of deoxidizing components such as SI+Mn1C is 0.
It can also contain up to 6%.

The components of the alloy of the present invention include the aforementioned Kovar alloy shown as point B in FIG. 004%, known to have a value of Ni3
2%, the balance is iron, and is shown as point C in the figure.

It is composed of 36% Ni and the balance is iron, and can be shown together with invar alloys, which are indicated by dots.

All of these alloys, which have been commonly known, are
1 point a as a component range that does not transform the crystal structure from r to α even when cooled to a low temperature of about -80'C
, b belongs to the area with a large amount of Ni and Co on the upper side of the curve passing through the vicinity of b. Conversely, the alloy of the present invention has a composition range set so that this r→α transformation occurs at temperatures above about -80°C, so 81%+0.3Co%≦34.
The Ni and GO components should be in the range below the 5% boundary 11ab, and the thermal expansion coefficient during cooling should be at most 4.5% for bonding with low thermal expansion ceramics. OX10
−'/”In order to keep the value below C, the straight line be or a
The region between e, i.e. Ni%+0.58Co%≦37.
The content range of Ni and CO satisfies 8% and 40%≦Ni%+CO%. Furthermore, the reverse transformation of the above r→α transformation, that is, the r→α transformation when the temperature is increased is the brazing temperature7.
The range that can occur at about 50 to 900°C is the area above the straight lines ed and dc, that is, Ni%+0.47%≧340
% and 24.0%≦Ni%.
The component range is o.

Ni and Co in the component range surrounded by abcde of the present invention,
Furthermore, the thermal expansion adjustment base, the remaining portion of which is essentially Fe, has an expansion coefficient of 4.0 from room temperature to 400°C, as explained above. less than OX 10-6/''C.

Furthermore, during cooling after brazing, or forcedly
It is an alloy that easily undergoes γ→α transformation by gradually supercooling to a certain degree or by processing.

The solid curve in the figure shows the starting temperature of γ→α transformation during cooling, and the dotted line shows the temperature at one point of Curie.

Figure 2 shows the thermal expansion curve (1) of the Kovar alloy, as well as an example of the alloy of the present invention, which is cooled to O''C and has a component in which α and γ coexist, and a component that is supercooled to -80°C and almost The thermal expansion curves for the component with only α are (2) and (3
). Namely, the alloy of the present invention is heated.

Since a hysteresis is generated when the temperature is increased, this hysteresis is effectively used to absorb the stress and strain caused by the brazing.

Figure 3 shows the alloy of the present invention and a sintered body metallized with a thermal expansion coefficient of about 3.2 x 10'/''C such as Si3N4 using eutectic silver solder with a melting point of 780°C. The principle of bonding will be explained using thermal expansion curves.The shrinkage of the alloy of the present invention and silicon nitride due to cooling is
1 alloy and ceramics in the flexible temperature range of 780°C to 500°C, which is the flexible temperature range of silver solder after brazing. Each shrinks like yellow and dust independently. However, below 500°C, the ceramics deform while being restrained by the silver solder, and the ceramic tends to shrink like a line rohenu, which shows shrinkage parallel to the chirality.

It is thought that at room temperature, a strain equivalent to the amount of strain remains. However, when the alloy of this example of the present invention is cooled to 0°C, it partially undergoes r-α transformation and the thermal expansion curve changes. At point C, most of the residual strain can be absorbed. If the temperature continues to rise after that, some strain will occur in the opposite direction, but this will not be a problem because the brazing material itself will soften and become flexible, allowing the alloy and ceramic to expand independently of each other. Furthermore, α→r transformation occurs at point T, resulting in a single phase consisting almost exclusively of γ.

As mentioned above, the thermal expansion adjustment alloy of the present invention is intended to eliminate or reduce residual stress and strain during brazing by utilizing rα transformation, and is intended to eliminate or reduce residual stress and strain during brazing. The concept is essentially different from that of nickel-iron alloys, etc.

As mentioned above, the present invention is applicable to ceramics such as nitrides and carbides whose coefficient of thermal expansion is on the order of 3 x 10-' or 4 x
It is possible to braze ceramics on the order of 10' with metals, and considering that there is no need to use rare metals such as tungsten, the effects of the present invention are extremely large.

The present invention will be explained below with reference to Examples.

Example 1 As an alloy of the present invention, an alloy having the components listed in Table 1 was blended and melted, and then hot rolled to a plate thickness of 10fi to 5IIs, and further cold rolled to form a 3111I plate. After that, a thermal expansion test piece was cut out and heat treated at 1000°C, then cooled to 0'C or -80°C. υα according to the expansion coefficient and thermal expansion curve.

I identified r and obtained the results listed in the same table, both of which were -8
At temperatures above 0°C, r→α transformation occurs, and the thermal expansion coefficient of r is 4.
Prove that it is less than 0 x t o-6/"c.

Example 2 As the alloy of the present invention, 45. /Vh10 and Si3N4 pressureless sintered ceramics with Ni, Or.

After metallizing using a metallizing composition containing Zr, using eutectic silver solder, using these alloys as a 2 m thick intermediate loose I material, after brazing to carbon steel with a diameter of 12 mm, It was cooled appropriately to -80°C, and the shear strength at room temperature was measured. For comparison, measurements were also made using Kovar μ alloy. Boiled 10 is 7.9#/d, flattened 5 is 9.
5 kg/d, 8.5 k(i
/-, indicating that the alloy of the present invention relaxes residual stress even at room temperature.

As described above, the present invention provides a new method for brazing low thermal expansion ceramics, and is very effective in solving difficult problems that could not be solved conventionally.

[Brief explanation of drawings]

Figure 1 shows the range of components of the thermal expansion adjustment alloy of the present invention.
, Co+'', where the area is the component range of the present invention alloy, points B, O, and D indicate the conventionally known alloys Kovar, Super Invar, and Invar, respectively, and each black dot indicates the number The composition of each alloy listed in Table 1 is shown.The solid line shows the temperature at which the γ→α transformation starts upon cooling, and the dotted line shows the Curie point. The thermal expansion curves of each Yaf alloy (1)
, (2), (3), (1), (2)
(3) is the case of supercooling to -80°C. FIG. 3 is a diagram illustrating one composition of the alloy of the present invention and the residual strain due to thermal expansion and brazing of a silicon nitride ceramic sintered body, and is a diagram illustrating the principle of the alloy of the present invention. Sadahito from Japan Hybrid Chikunoro Seeds Co., Ltd.'s first product! ”, (1 Co (%) 2nd temperature (0C) Note 30 Temperature (°C)

Claims (1)

[Claims] 40%≦Ni%+Co%, 24.0%≦Ni%, Ni%
+0.47Co%≧34.0%, Ni%+0.3Co%
≦34.5%, Ni%+0.58Co%≦37.8% (
1. A thermal expansion adjustment alloy for ceramic brazing, characterized by comprising Co and Ni, with the balance substantially consisting of Fe and unavoidable impurities, in a range that satisfies all inequalities of (wt%).