JPH0621322B2 - Ceramic expansion brazing alloy for brazing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal expansion control alloy which can be brazed to a dense ceramic having a smaller thermal expansion coefficient than Al ₂ O ₃ ceramics and a relatively high strength.

Conventionally, to braze a metal to ceramics, a metal or alloy that has a thermal expansion coefficient that is as close as possible is selected, and the heat generated due to the difference in thermal expansion coefficient between the two in the cooling process during brazing. It has been carried out by making the stress as small as possible, or by devising a soft metal such as steel, silver, and aluminum as an intermediate cushioning material to intervene to absorb the strain due to this thermal stress.

However, in recent years, as carbide-based and nitride-based ceramics having relatively high mechanical properties and high strength and a small thermal expansion coefficient, for example, normal pressure sintering SiC, reaction sintering SiC-S.
With the development of ceramics sintered bodies such as i, atmospheric pressure sintered Si ₃ N ₄ and atmospheric pressure sintered AlN, metals and alloys with a small thermal expansion coefficient that can be brazed to these ceramics have been developed. I have been forced to develop. The metal with the smallest coefficient of thermal expansion is W in the temperature range of room temperature to 800 ℃ for silver brazing.
And the value is about 45 × 10 ⁻⁶ / ° C.
The thermal expansion coefficient of C, SiC-Si or AlN is 4-5 × 10 ^-6
It can be barely used for brazing ceramics sintered bodies within the range of / ° C. However, since W is extremely hard, brittle, and poor in flexibility, strain is likely to remain in the joint portion, and resources are scarce and expensive, so it is not a satisfactory material. Further, Co 17.0 wt% and Ni 29.0 which are conventionally known as alloys for joining Al ₂ O ₃ ceramics are used.
The Kovar alloy, which is composed of wt% and the balance of Fe, has a thermal expansion coefficient of 4.8 × 1 even in the temperature range from room temperature to 430 ° C.
It is about 0 ⁻⁶ / ° C., and the average is 8.8 × 10 ⁻⁶ / ° C. in the range of room temperature to 800 ° C., so it is difficult to apply it to the low thermal expansion ceramics as described above.

The present invention has been made in view of these circumstances,
The ceramics with a small thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less have high strength, and brazing to the dense ceramics having a segregation force of 20 kg / mm ² or more without compromising the strength. The aim is to provide possible alloys.

The thermal expansion control alloy for ceramics brazing of the present invention has a range shown as an A region in FIG. 1 (hereinafter, weight% is omitted), that is, 40% ≦ Ni% + Co%, 24.0% ≦ Ni. %, Ni%
+ 0.47Co% ≧ 34.0%, Ni% + 0.3Co%
≦ 34.5% Ni% + 0.58Co% ≦ 37.8%, Co and Ni in a range that satisfies all the inequalities, and the balance is substantially Fe and inevitable impurities. However, the total content of deoxidizing materials such as Si, Mn, C is 0.6%.
It can also include:

The composition of the alloy of the present invention has the above-mentioned Kovar alloy shown as point B in FIG. 1 and a very small coefficient of thermal expansion of 1.3 × 10 ⁻⁶ / ° C. in the temperature range from room temperature to 100 ° C. It is known to have 4% Co, 13% Ni, and the balance iron, and is shown together with the Super Invar alloy shown as point C in the figure, and the Invar alloy made of 36% Ni and the balance iron at point D. You can

Each of these alloys, which are generally known from the past,
The crystal structure changes from γ to α even when cooled to a temperature as low as −80 ° C.
As a component range that does not transform into
It belongs to a region containing a large amount of Ni and Co above the curve passing near b. On the contrary, since the alloy of the present invention has the composition range set so that the γ → α transformation occurs at a temperature of about −80 ° C. or higher, the boundary line ab of Ni% + 0.3Co% ≦ 34.5% is satisfied. Since Ni and Co components in the lower range are used and the coefficient of thermal expansion during cooling is to be kept to a value of less than 4.0 × 10 ⁻⁶ / ° C. at the maximum in order to bond with low thermal expansion ceramics. The area between the straight lines b or ae, that is, Ni
% + 0.58Co% ≦ 37.8% and 40% ≦ Ni% + C
The composition range of Ni and Co that satisfies o% is set. Further, as a range in which the reverse transformation of the γ → α transformation, that is, the γ → α transformation can occur at a brazing temperature of about 750 to 900 ° C. at the time of temperature rise, a region above the straight lines ed and dc, that is, Ni% +
The composition ranges of Ni and Co satisfy 0.47% ≧ 34.0% and 24.0% ≦ Ni%.

Ni and Co in the composition range surrounded by abcde of the present invention,
Further, the balance of the thermal expansion adjusting alloy consisting essentially of Fe has a thermal expansion coefficient of less than 4.0 × 10 ⁻⁶ / ° C. from room temperature to 400 ° C. as described above, and during cooling after brazing, Alternatively, by forcibly gradually cooling to about -80 ° C or by processing, γ →
An alloy that undergoes alpha transformation. In the figure, the solid line curve shows the starting temperature of the γ → α transformation during cooling, and the dotted line shows the temperature at the Curie point.

FIG. 2 shows the thermal expansion curve (1) of Kovar alloy, and as an example of the alloy of the present invention, it was cooled to 0 ° C., a component in which α and γ coexist, and supercooled to −80 ° C. The thermal expansion curves of the components with only α are shown as (2) and (3), respectively. That is, since the alloy of the present invention produces a history during heating and temperature rise,
This history is used effectively to absorb the stress and strain generated by the brazing.

FIG. 3 shows the thermal expansion coefficient of the alloy of the present invention and Si ₃ N ₄ etc.
The principle of brazing and joining a sinter that has been subjected to a metallizing treatment of about 2 × 10 ⁻⁶ / ° C. using eutectic silver solder having a melting point of 780 ° C. will be described using a thermal expansion curve. The shrinkage of the alloy of the present invention and silicon nitride due to cooling is represented by the lines of Irohani and Chini. Considering now the line showing the shrinkage of the alloy as a reference, the flexible temperature range of silver solder after brazing is considered. 780 ° C
In the region of ~ 500 ° C, the alloy and the ceramic shrink independently like yellow and dust. However, at temperatures below 500 ° C, they are deformed while being constrained by silver brazing, and the ceramics try to shrink like the line Rohenu, which shows shrinkage parallel to the chillini, so it is thought that at room temperature, a strain equivalent to the amount of Nuni remains. . However, when the alloy of the present invention of this example is cooled to 0 ° C., a partial γ → α transformation occurs to cause a change in the thermal expansion curve. At this point, the above residual strain can be almost absorbed. If the temperature is further increased thereafter, a strain in the opposite direction will occur, but the brazing filler metal itself will soften and become flexible, so that the composite and the ceramics will be able to expand independently of each other, so there is no problem. Furthermore, at the point G, the α → γ transformation occurs, and almost a single phase consisting of only γ is formed.

As described above, the thermal expansion control alloy of the present invention is intended to eliminate or reduce the residual stress and strain during brazing by utilizing the γα transformation, and the conventional generally known Kovar or 42% The idea is essentially different from nickel-iron alloy and the like. According to the present invention, as described above, the coefficient of thermal expansion of ceramics such as nitrides and carbides is 3 × 10.
^-6 or 4 × 10 ^-6 ceramics which can be brazed with a target metal, and considering that it is not necessary to use a rare metal such as tungsten, The effect is extremely large.

The present invention will be described below with reference to examples.

Example 1. As the alloy of the present invention, alloys having the components shown in Table 1 were blended and melted, and hot rolled to a plate thickness of 10 mm to 5 mm, and further cold rolled to a plate material of 3 mm. After that, a thermal expansion test piece is cut out and heat-treated at 1000 ° C.,
After cooling to 0 ° C. or −80 ° C., α and γ were identified by the thermal expansion coefficient and the thermal expansion curve, and the results shown in the same table were obtained. In both cases, the γ → α transformation occurs at −80 ° C. or higher, It was proved that the coefficient of thermal expansion of γ was less than 4.0 × 10 ^-6 / ° C.

Example 2. As the alloy of the present invention, No. 5 and No. 10 in the above examples were selected.
Using a metallizing composition containing Ni, Cr, and Zr, a pressure-pressure sintered ceramic of Si ₃ N ₄ and using a eutectic silver braze after metallizing, using these alloys as an intermediate buffer material having a thickness of 2 mm. -8 after brazing to carbon steel with a diameter of 12 mm
After supercooling to 0 ° C., the shear strength at room temperature was measured. or,
For comparison, the measurement was performed also when Kovar alloy was used. No. 10 shows a value of 7.9 kg / mm ² , No. 5 shows a value of 9.5 kg / mm ² , and Kovar shows a value of 8.5 kg / mm ² , showing that the alloy of the present invention relaxes the residual stress even at room temperature. I showed that.

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

[Brief description of drawings]

FIG. 1 shows the composition range of the thermal expansion control alloy of the present invention Fe, C
FIG. 3 is a ternary composition diagram of o and Ni, where region A is the composition range of the alloy of the present invention, points B, C and D are the conventionally known alloys of Kovar, Super Invar and Invar, and the black dots are the first. The components of each alloy described in the table are shown. The solid line shows the temperature at which the γ → α transformation starts during cooling, and the dotted line shows the Curie point. FIG. 2 shows Kovar alloy, No. 9 described in Table 1 of the present invention alloy.
The thermal expansion curves of alloy No. 7 and alloy No. 7 are (1), (2),
Shown by (3), (1) and (2) are when cooled to 0 ° C, and (3) is when supercooled to -80 ° C. FIG. 3 is a diagram showing the principle of the alloy of the present invention by illustrating one composition of the alloy of the present invention and the residual strain due to thermal expansion and brazing of a silicon nitride ceramics sintered body.

Claims (1)

[Claims] 1. 40% ≦ Ni% + Co%, 24.0% ≦ N
i%, Ni% + 0.47Co% ≧ 34.0%, Ni% +
0.3Co% ≦ 34.5%, Ni% + 0.58Co% ≦
Heat for brazing ceramics characterized by being composed of Co and Ni, and the balance being substantially Fe and inevitable impurities, in a range satisfying all inequalities of 37.8% (weight% is omitted). Expansion adjustment alloy.