JP2536630B2 - Method for joining ceramic member and metal member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for joining a ceramic member and a metal member, and more specifically, joining a ceramic member and a metal member using a precipitation hardening alloy as the metal member. Regarding the method.

[Prior Art] In recent years, various methods for joining a ceramic member and a metal member have been proposed. For example, in Japanese Unexamined Patent Publication No. 62-70275, a shaft protrusion of a ceramic member and a cylindrical portion of a metal member are fitted with each other through a filling metal material (brazing material) and heated under a load. Then, the filling metal material is melted and filled, and shrinkage stress is generated by utilizing the difference in shrinkage amount based on the difference in thermal expansion coefficient between the metal member and the ceramic member in the cooling process after the filling metal material is solidified. Is disclosed. Further, JP-A-61-40879 discloses a method of using a precipitation hardening alloy as a metal member and performing a precipitation hardening treatment after bonding with a ceramic member. This precipitation hardening alloy is an alloy that hardens due to the precipitation of a solute from the supersaturated solid solution when it is held at the aging temperature for a long time, and is effective in maintaining a high binding force.

Therefore, when the cylindrical protrusion of the metal member is shrink-fitted to the shaft protrusion of the ceramic member, if the filling metal material is filled and a precipitation hardening alloy is used as the metal member, the coupling between the shaft protrusion and the cylindrical member is achieved. It is expected that the power will increase further.

[Problems to be Solved by the Invention] However, it has been found that satisfactory results cannot be obtained even if such means is adopted. This is because when the melt filling process is performed before the precipitation hardening of the cylindrical part made of precipitation hardening alloy, shrink fit stress occurs in the cylindrical part in the cooling process after the molten filling metal material is solidified. It is due to starting to. That is, at the time of cooling after the melt-filling treatment, shrinkage stress is generated in the tubular portion, so high-temperature strength is required, but this property is not obtained in the precipitation-hardening alloy in the non-precipitation hardened state. Therefore, even if the precipitation hardening treatment is performed after the melt filling processing of the filled metal material, the bond strength due to both the melt filling processing and the precipitation hardening treatment cannot be obtained.

SUMMARY OF THE INVENTION The present invention provides a technical problem to be solved to reliably increase the bonding force between a ceramic member and a metal member by both precipitation hardening treatment and melt filling treatment.

[Means for Solving the Problems] The method for joining a ceramic member and a metal member according to the present invention includes:
A fitting step of fitting the shaft projection of the ceramic member into the cylindrical portion of the metal member made of a precipitation hardening alloy through a filling metal material having a melting point higher than the precipitation hardening temperature of the precipitation hardening alloy, and the filling process. A melt-filling treatment step of heating the metal material to a temperature equal to or higher than the melting point to melt-fill the filled metal material between the shaft projection portion and the tubular portion, and a furnace cooling during a cooling process after the melt-filling treatment step. It is characterized by comprising a precipitation hardening treatment step of holding and cylindrically hardening the tubular portion.

The fitting step constituting the joining method of the present invention is a step of fitting the shaft protrusion of the ceramic part and the tubular part of the metal member made of a precipitation hardening alloy with a filling metal material interposed therebetween. This fitting can be performed, for example, by press fitting the outer diameter of the shaft protrusion slightly larger than the inner diameter of the tubular portion. The filling metal material should be assembled in the axial gap formed between the shaft protrusion and the cylindrical portion, or in the recess formed on the outer peripheral surface of the shaft protrusion or the inner peripheral surface of the cylindrical portion. You can

The ceramic member has a shaft protruding portion at one end, and the metal member has a cylindrical portion that can be fitted into the shaft protruding portion. The material of the ceramic member is not particularly limited, and may be, for example, silicon nitride, silicon carbide, alumina or the like.
The type of the precipitation hardening alloy is not particularly limited, and for example, Incoloy 903 having a precipitation hardening temperature of 720 ° C., Incoloy 904 having the same hardening temperature of 600 ° C. and the like can be used. As the filling metal material, one having a melting point higher than the precipitation hardening temperature of the precipitation hardening alloy and lower than the melting point of the precipitation hardening alloy is used. As the filling metal material, for example, a copper alloy, a silver alloy, a palladium alloy, a nickel alloy or the like can be used.

The melt-filling treatment step constituting the joining method of the present invention is a step of heating the filler metal material to a temperature equal to or higher than the melting point to melt-fill between the shaft protrusion and the tubular portion. The filled metal material heated above the melting point melts and solidifies at the solidification point during the subsequent cooling process. This melt filling process can be performed in a state in which a load is applied in a direction in which the shaft protrusion portion and the tubular portion approach each other.

The precipitation hardening treatment step that constitutes the joining method of the present invention is a step of precipitating and hardening the tubular portion by keeping the furnace cold in a predetermined temperature range for a predetermined time or more during cooling after the melt filling treatment step. . As a result, the tubular portion is hardened due to the precipitation of the solute from the supersaturated solid solution, and the high temperature strength required for bonding with the shaft protrusion is obtained. Further, due to the difference in shrinkage amount based on the difference in coefficient of thermal expansion between the tubular portion and the shaft projection portion, shrink fit stress is generated, and the binding force is increased. This precipitation hardening treatment can be carried out by keeping the furnace at a precipitation hardening temperature lower than the melting point of the filling metal material for a predetermined time or more, or in a predetermined temperature range near the precipitation hardening temperature for a predetermined time or more. It can also be carried out by holding. In the latter case, it is preferable to set the temperature within a range of 100 ° C. from the precipitation hardening temperature. The holding time is preferably 10 minutes or more and 120 minutes or less. If the holding time is shorter than 10 minutes, sufficient precipitation hardening does not occur and sufficient bond strength cannot be secured. Also, even if the holding time is longer than 120 minutes, the bond strength obtained does not change.

[Operation] The method for joining the ceramic member and the metal member of the present invention is
The shaft protrusion of the ceramic member and the tubular portion made of precipitation hardening metal are fitted through a filling metal material having a melting point higher than the precipitation hardening temperature, and the above filling metal material is heated to a melting point or higher to melt and fill. After that, the furnace is kept at a predetermined temperature for a predetermined time during the cooling process to precipitate and harden the tubular portion. Therefore, first, in the melt filling process, the filling metal material is melt-filled between the shaft projection and the cylindrical portion, and the molten filling metal material is solidified at the freezing point in the subsequent cooling process, whereby the shaft projection is formed. And the tubular portion are joined together. Further, in the subsequent precipitation hardening treatment step during the cooling process, the cylindrical portion is precipitation hardened to obtain the high temperature strength necessary for bonding with the shaft protruding portion, and the heat shrinkage occurs between the shaft protruding portion and the cylindrical portion. Shrinkage stress occurs due to
The bond strength between the two is further increased.

Although shrink-fitting stress occurs in the tubular portion even within the temperature range from the solidification of the molten filling metal to the precipitation hardening of the tubular portion, the solidification point of the molten filling metal and the precipitation hardening temperature Since the difference is small, the effect of shrink fit stress in the above temperature range is small.

[Examples] Hereinafter, specific examples will be described with reference to the drawings.

The present embodiment applies the present invention to the manufacture of a ceramic turbo rotor shaft. As shown in FIG. 1, the ceramic turbo rotor shaft includes a ceramic turbine wheel 1, a metal sleeve 2, and a metal shaft 3.
It consists of and. The ceramic turbine wheel 1 is made of silicon nitride and has a shaft projection 11 formed at its tip. The metal sleeve 2 is made of precipitation hardenable alloy Incoloy 903 (precipitation hardening temperature 720 ° C.), and the shaft projection 11
A tubular portion 21 that fits with is formed. The shaft protrusion 11
Has an outer diameter of 12 mm and an inner diameter of the tubular portion 21 of 12.2 mm. In addition,
Copper plating is applied to the inner peripheral surface of the tubular portion 21 to improve the wettability of the filling metal material 4 (described later) with respect to the tubular portion 21. Further, FIG. 2 is a graph showing a heating pattern of each treatment of the joining method of this embodiment.

(Fitting process) Silver brazing is applied to the concave portion 22 formed on the inner peripheral end surface of the opening of the tubular portion 21.
The shaft protrusion 11 and the tubular portion 21 were fitted together with the filler metal material 4 made of BAg-8 (melting point 780 ° C.) assembled.

(Melting and filling process step) The thus-integrated unit is set in a jig (not shown), placed in a vacuum furnace with a load applied so as to press the tubular portion 21 against the shaft protrusion 11 and placed at 850 ° C. Hold at the temperature for 60 minutes to melt the filling metal material 4 to make the shaft projection 11 and the tubular portion 21
Filled between and.

(Precipitation hardening treatment step) After that, the furnace is kept cold in a vacuum furnace, and as shown in FIG.
It was cooled to 620 ° C. over about 30 minutes so that it was kept at a temperature range of 720 to 620 ° C. (range indicated by T in FIG. 2) for 10 minutes. At this time, first, the freezing point (78
When the temperature becomes 0 ° C. or lower, the molten filling metal material 4 is solidified, and the shaft protruding portion 11 and the tubular portion 21 are bonded. And
In the temperature range of 720 to 620 ° C., the tubular portion 21 is hardened due to the precipitation of the solute from the supersaturated solid solution, and the high temperature strength required for bonding with the shaft projection 11 is obtained. Further, a shrink fit stress is generated due to a difference in shrinkage amount based on a difference in thermal expansion coefficient between the shaft protrusion portion 11 and the tubular portion 21, and a coupling force between the shaft protrusion portion 11 and the tubular portion 21 is increased.

After that, argon gas was introduced into the vacuum furnace and forced cooling to normal temperature was performed for 60 minutes using a cooling fan.

After joining the ceramic turbine wheel 1 and the metal sleeve 2 as described above, a metal shaft 3 made of chrome steel is electron beam welded 5 to the metal sleeve 2 and finished by machining to make a ceramic turbo rotor. The shaft was manufactured. About this shaft Exhaust gas temperature 950 ℃
As a result of a high-temperature high-speed rotation test conducted at, it was confirmed that there was no breakage even at 180,000 rpm and that good bonding was achieved.

(Test Example) In the above example, the precipitation hardening treatment temperature (720 to 620
The holding time T of (° C.) was variously changed, and the relationship between the holding time T and the hardness of the metal sleeve 2 was investigated. FIG. 3 shows the results. Further, the holding time T was variously changed, and the ceramic turbo rotor shaft manufactured in the same manner as in the above-mentioned embodiment was subjected to a high temperature twist tester to measure the high temperature twist strength of the joint at 500 ° C.
I investigated the relationship with the hardness. The results are shown in FIG.

As can be seen from FIGS. 3 and 4, the holding time T
The hardness of the metal sleeve 2 is 280 by making it 10 minutes or more.
If the hardness of the metal sleeve 2 is 280 Hv or more, sufficient bond strength can be obtained. Therefore, by setting the holding time T in the precipitation hardening treatment to 10 minutes or more, sufficient bond strength can be secured. Even if the holding time T was set longer than 10 minutes, the hardness of the metal sleeve 2 did not increase.

[Effects of the Invention] As described in detail above, in the method for joining a ceramic member and a metal member according to the present invention, the filling metal material having a melting point equal to or higher than the precipitation hardening temperature is the axial projection of the ceramic member and the tubular shape of the metal member. The molten metal material is melt-filled between the shaft projection and the tubular portion at the solidification point during the subsequent cooling process. Furthermore, in the subsequent precipitation hardening step during the cooling process, the cylindrical portion is precipitation hardened to obtain the high temperature strength necessary for bonding with the shaft protruding portion, and heat shrinkage occurs between the shaft protruding portion and the cylindrical portion. Shrinkage stress is generated and the binding force between the two is further increased.

Therefore, since the joining method of the present invention performs the precipitation hardening treatment during the cooling process after the melt filling processing, the bond strength does not decrease even when the melting point of the filled metal material is higher than the precipitation hardening temperature, and the melt filling is performed. By both the treatment and the precipitation hardening treatment, it becomes possible to reliably join the shaft protrusion and the tubular portion.

Moreover, since the furnace is cooled after the melt filling process, thermal stress does not suddenly act on the ceramic member,
It is possible to prevent cracks caused by the thermal stress.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a ceramic turbo rotor shaft obtained by the joining method of this embodiment, FIG. 2 is a graph showing a heating pattern in each treatment step of the joining method, and FIG.
FIG. 4 is a graph showing the relationship between the holding time T in the precipitation hardening treatment step and the hardness of the metal sleeve, and FIG. 4 is a graph showing the relationship between the high temperature torsion strength and the hardness of the metal sleeve. DESCRIPTION OF SYMBOLS 1 ... Ceramic turbine wheel 2 ... Metal sleeve, 3 ... Metal shaft 4 ... Filling metal material, 11 ... Shaft protrusion 21 ... Cylindrical part

Claims (1)

(57) [Claims] 1. A fitting for fitting a shaft projection of a ceramic member to a cylindrical portion of a metal member made of a precipitation hardening alloy through a filling metal material having a melting point higher than the precipitation hardening temperature of the precipitation hardening alloy. A melt filling treatment step of heating the filling metal material to a temperature equal to or higher than the melting point so as to melt-fill the filling metal material between the shaft protrusion and the cylindrical portion, and cooling after the melting filling treatment step. A method for joining a ceramic member and a metal member, which comprises a precipitation hardening treatment step of holding the furnace cold during the process to precipitate and harden the tubular portion.