JPH0776141B2 - Ceramic member for joining with metal member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention relates to a ceramic member joined to a metal member.

(2) Conventional Technology Conventionally, as this type of ceramic member, a large number of recesses that open to the joint surface are formed in a surface layer portion that constitutes a joint surface with a metal member, and these recesses are used when the metal member is forged. It is known that one of the metal members is filled (see Japanese Patent Laid-Open No. 61-259865).

(3) Problems to be Solved by the Invention However, in the joined body with the metal member using the ceramic member, physical properties such as thermal conductivity, thermal expansion coefficient, and electrical conductivity, and tensile strength are obtained at the joint portion of both members. Mechanical properties such as strength, impact value, and fatigue strength change rapidly, so if the joint is subjected to repeated loading for a long period of time or used under severe thermal cycles, the joint may start to break. Therefore, there is a problem that the durability of the bonded body is significantly impaired.

Further, in order to improve machining efficiency, it is desirable to adopt electric discharge machining, but since the ceramic member has extremely low electric conductivity, it is impossible to apply electric discharge machining. Therefore, it is conceivable that the ceramic member is made to contain a conductive substance so as to have a predetermined electric conductivity. In this case, however, the electric conductivity is drastically changed at the joint portion, which causes a discharge. There is a problem that the joint generates high heat during processing.

In view of the above, it is an object of the present invention to provide the ceramic member that has excellent durability and can obtain the joined body that can be electric discharge machined.

B. Structure of the Invention (1) Means for Solving Problems The present invention provides a ceramic member joined to a metal member, which contains a conductive ceramic component and is filled with a part of the metal member. It has a three-dimensional network structure with fine pores, and is characterized in that the diameter of the pores is gradually reduced as the distance from the joint surface with the metal member increases.

(2) Action When the diameter of the pores is made to have a gradient in the ceramic member as described above, when these pores are filled with a part of the metal member and the metal member and the ceramic member are joined, As the composite of ceramics and metal changes, the physical and mechanical properties of the ceramic member from the joint surface to the entire joint will change with a certain gradient. Can be prevented from deteriorating.

The ceramic member has a predetermined electric conductivity by containing a conductive ceramic component, and since the fine pores are partially filled with the metal member, the ceramic member, and hence the entire bonded body, has a good electrical conductivity. Exhibits electrical properties, which enables electrical discharge machining of the joined body.

In this case, since the electric conductivity of the joint of the joined body also changes with a certain gradient, the joint does not generate high heat during electric discharge machining.

It is also possible to perform electric discharge machining on a single ceramic member.

(3) Example A ceramic member according to the present invention, which contains a conductive ceramic component and has a three-dimensional network structure with innumerable fine pores, is manufactured through the following steps. That is, a conductive ceramic powder, a powdery pore-forming substance that can be eluted by an acid, and an additive that accelerates the elution treatment of the pore-forming substance and a sintering aid powder are dispersed in the ceramic powder that is the main component. In the step of obtaining a molded body using the mixed powder, the step of subjecting the molded body to a sintering treatment to obtain a sintered body, and the step of subjecting the sintered body to an elution treatment to dissolve the pore-forming substance after melting and solidification. is there.

As the ceramic powder, Si ₃ N ₄ , Si having a diameter of 10 μm or less can be used.
Single powders of C, ZrO ₂ , Al ₂ O ₃ , sialon, etc., and mixed powders thereof are applicable.

The sintering aid powder is used as necessary to improve the sinterability of the ceramic powder. As the seed powder, Al ₂ O ₃ , Y ₂ O ₃ , MgO, SiO having a diameter of 0.1 to 5 μm are used. ₂ , CeO ₂
Single powders such as and mixed powders thereof are applicable.

Conductive ceramic powders include Ti, Ta, Hf, Mo, W,
Carbides such as Cr and Zr, nitrides, borides, etc. are applicable.

A powdery pore-forming substance that can be eluted by an acid is used to positively form fine pores in a sintered body to obtain a ceramic member having a three-dimensional network structure with a predetermined porosity. The following applies.

SiO ₂ 20 to 40 wt% B ₂ O ₃ 30 to 50 wt% Al ₂ O ₃ 3 to 15 wt% MgO 2 to 12 wt% K ₂ O 2 to 15 wt% Na ₂ O 10 to 25 wt% each powder And TiO ₂ , if necessary, to the mixed powder.
MoO, Cr ₂ O ₃ , ZrO ₂ , Li ₂ O, BaO, La ₂ O, Cs ₂ O, Ce ₂ O ₃ , Y ₂
Maximum diameter 44μ obtained by adding at least one powder selected from O ₃ , CaO, etc., and melting and crushing.
It is a vitreous powder having an average diameter of 10 μm or less.

The reason for limiting the blending amount of each powder as described above is that if the blending amount is deviated from the above, the crystals are deposited on the pore-forming substance to form a non-uniform structure, and elution with acid becomes impossible. Further, in the present invention, as will be described later, melting of the pore-forming material in the sintering process, since it is aimed at the change in the diameter of the pores due to the flow, at the sintering treatment temperature, for example, 800 ~ 1400 ℃, the flow generated from the pore-forming material It is necessary for the body to have a predetermined viscosity, for example 0.1 to 20 cP, and for this reason the compounding amount of each powder is limited as described above.

At least one selected from a boron compound and a phosphoric acid compound is used as an additive that accelerates the elution treatment of the pore-forming substance, and thus the pore-forming component produced by melting and solidifying the substance. In this case, the boron-based compound includes sodium borate, borate such as ammonium borate, boric anhydride (B ₂ O ₃ ), and the like, and the phosphoric acid-based compound includes sodium hexametaphosphate and sodium acid metaphosphate. And other metaphosphates, orthophosphoric acid, phosphoric anhydride (P ₂ O ₅ ) and the like are included.

This additive has almost no involvement in the sintering process of the ceramic powder, and therefore, it exists in the sintered body and functions to accelerate the elution treatment of the pore-forming component with acid, and thereafter, to the sintered body. It is more eluted with the pore-forming component.

Alumina fibers, silicon carbide fibers (including whiskers), silicon nitride fibers, carbon fibers, etc. may be blended in order to improve the strength of the ceramic member.

The ceramic powder, the conductive ceramic powder, the sintering aid powder, the pore-forming substance and the additive are blended in the following amounts: ceramic powder 40 to 80% by weight conductive ceramic powder 5 to 40% by weight sintering aid powder 15% by weight Below, 5 to 50% by weight of pore-forming substances and 20% by weight or less of additives.

The reason for limiting the compounding amount of the conductive ceramic member as described above is that if it exceeds 40% by weight, the sintering of the ceramic powder as the main component is hindered, and if it is less than 5% by weight, the conductivity is lowered and the discharge is caused. This is because processing becomes impossible.

The reason for limiting the blending amount of the sintering aid powder as described above is
This is because the sinterability of the ceramic powder does not change so much even if it is mixed in an amount exceeding 15% by weight.

The amount of the pore-forming substance mixed varies depending on the target porosity of the ceramic member, and the porosity can be adjusted to 5 to 80% by the above-mentioned amount.

Additives improve the mutual diffusivity when joining a ceramic member and a metal member made of aluminum alloy, steel, etc., and reduce the contact angle of the metal to the ceramic member to significantly improve its wettability. Since it has the effect of increasing the bonding strength, if this curing is aimed at, an additive is added in a slight excess so that it remains in a thin film on the inner surface of the pores of the ceramic member even after the elution treatment. At this time, the additive amount is
10 to 20% by weight is suitable.

When a molded body is obtained using a mixed powder composed of the ceramic powder, the conductive ceramic powder, the sintering aid powder, the pore-forming substance and the additive, a slip casting method,
Various molding methods such as a pressure molding method and an injection molding method are used.
In this case, a molding pressure of 25 to 150 MPa is suitable.

In the sintering of the molded body, 1500 ~ 2200
The one-step sintering method that completes the sintering of the ceramic components by holding the temperature at 0.5 ℃ for 0.5 to 2 hours once
Primary sintering process to secure 0 to 1400 ℃ for 0.5 to 2 hours and 15
A two-stage sintering method is adopted in which the sintering of the ceramic components is completed through a secondary sintering process of holding at 00 to 2200 ° C for 0.5 to 2 hours. When the one-stage sintering method is adopted, it is natural that the elution treatment is performed after the sintering treatment. However, when the two-stage sintering method is adopted, the primary sintering treatment or the secondary firing is performed. After the binding treatment, the elution treatment is performed.

Since the sintered body after the primary sintering process has an appropriate hardness, it is possible to subject the sintered body to mechanical processing such as lace processing. In this case, the defects caused by machining are
It can be removed by the chemical polishing action of the elution treatment in the next step.

The acid used in the elution treatment is mainly a single acid such as HCl, HNO ₃ , HF or a mixed acid thereof, and in some cases, a small amount of an organic acid such as carboxylic acid such as CH ₃ COOH or HCOOH is added to the acid. To be done. The elution treatment is performed by immersing the sintered body in an acid solution for a predetermined time. At that time, when ultrasonic vibration of 8 to 24 MHz is applied to the acid solution while flowing, the acid solution spreads to the ceramic component, the pore-forming component and the sintering aid component, and also has the action of promoting the elution treatment of the additive. The elution treatment of impurities contained in the pore-forming component and the ceramic component and the sintering aid component can be completed within a short time.

By the elution treatment on the sintered body, a ceramic member having a three-dimensional network structure having innumerable fine pores can be obtained.

The diameter of the pores of this ceramic member is the largest on the end face side facing downward in the sintering furnace during the sintering process, and gradually decreases as the distance from the end face increases.

This is probably due to the following reasons.

That is, in the sintering process, when the temperature of the molded body, that is, the vitreous pore-forming substance reaches about 1000 to 1200 ° C., the substance melts and becomes a fluid having a predetermined viscosity. Then, the fluid descends due to gravity, the rearrangement of the tissue due to the rise of the ceramic component accompanying it, and the re-elevation of the fluid due to the capillary action of the fine gaps generated between the ceramic components due to the descending of the fluid, which causes sintering. The concentration of the pore-forming component in the body is high on the end face side, and gradually decreases as the distance from the end face increases.

By subjecting the sintered body in such a state to the elution treatment, it is possible to form pores having a gradient in diameter as described above.

When the ceramic member obtained by the above method is joined to a metal member, the end face on the side where the diameter of the pore is large serves as the joint surface.

The fluid also has a function of removing impurities because it entrains impurities that cause a decrease in strength of the ceramic member and descends.

In joining the ceramic member and the metal member, the ceramic member joining portion of the metal member is melted, and the ceramic member is heated at a high temperature to press one of the two members to the other. Installed in the vacuum casting method,
A means such as applying a casting method such as a low pressure casting method, a high pressure casting method, a gravity casting method, and the like, at the same time as casting the metal member and joining the ceramic member to the metal member is used.

Incidentally, in order to improve the wettability of the metal member to the ceramic member, Ti, Cu, Ag, on the inner surface of the pores of the ceramic member,
It is effective to form a thin film such as B by chemical vapor deposition (CVD) or the like.

Example 1 Maximum diameter 1.0 μm, minimum diameter 0.1 μm, average value diameter 0.4 μm
Si ₃ N ₄ powder as a base material, AlN, Al ₂ O ₃ , and Y ₂ O ₃ are added to this, and Si _6-X Al _X O _X N _8-X (where 0 < _X ≤ 4.3) Get the Sialon.

SiO ₂ 27.3% by weight B ₂ O ₃ 39.8% by weight Al ₂ O ₃ 8.6% by weight MgO 4.5% by weight Na ₂ O 13.2% by weight K ₂ O 4.6% by weight BaO 2.0% by weight and an average diameter of 10 μm To obtain a glassy powder of.

Sialon 60% by weight Conductive ceramic powder TiN with a maximum diameter of 5 μm and average diameter of 0.7 μm 20% by weight Pore forming substance 20% by weight, organic wax, dispersant, etc. are thoroughly mixed to obtain a mixed powder. The pressure molding method using a die was applied using powder, and the molding pressure was 75 MPa, and the length l = 9 shown in FIG.
A plate-shaped compact 1 having a width of 0 mm, a width of w = 20 mm, and a thickness of t = 5 mm is obtained.

After drying the molded body 1, the molded body 1 was erected in the sintering furnace with one end surface 1a thereof facing downward, and the N ₂ flow rate was 30 ml / min.
The molded body 1 is subjected to an organic component removal treatment under the conditions of 5 Torr, 650 ° C. and 1 hour.

Subsequently, the compact 1 is subjected to primary sintering treatment under the conditions of N ₂ flow rate of 30 ml / min, 0.4 Torr, 1200 ° C. and 2 hours.

Next, apply pressure to the sintered body after the primary sintering treatment under N ₂ atmosphere.
HIP treatment (secondary sintering treatment) is performed under the conditions of 500 kg / cm ² , 1750 ° C., and 1 hour to highly advance the sintering.

25% HNO ₃ and 0.2% H 2 heated to 30-60 ℃
It is immersed in an acid solution from F, and the acid solution is kept for 15 minutes while applying ultrasonic vibration of 16 MHz to elute the pore-forming components and impurities, and has a three-dimensional network structure shown in FIG. 2 (a). The plate-shaped ceramic member 2 is obtained. The dimensions of this ceramic member 2 are substantially the same as those of the molded body 1.

FIG. 2B shows the relationship between the distance from the one end surface 2b of the ceramic member 2 in the length direction, the maximum diameter of the pores, and the porosity. The line x ₁ corresponds to the maximum pore diameter, and the line x ₂ corresponds to the porosity.

From FIGS. 2 (a) and 2 (b), the other end surface of the ceramic member 2 is shown.
It can be seen that the diameter of the pores is the largest on the 2a side and the porosity is the highest, and the diameter of the pores gradually decreases as the distance from the other end surface 2a decreases, and the porosity gradually decreases.

FIG. 3 shows the relationship between the porosity and the bending strength of the ceramic member 2.

The electrical conductivity of the ceramic member 2 is 10 ^-2 Ω ^-1 · cm ^{-1 when the} content of TiN as the conductive ceramic powder is 20% by weight.

After preheating the ceramic member 2 to 1400 ° C., one end surface 2a side having a large pore diameter is installed in the mold with the gate side facing, and the molten metal temperature 1400 is used by using chrome steel (JIS SCM415).
Casting was performed under the conditions of ℃ and molten metal filling pressure of 50 kg / cm ² .
A joined body 4 of the chromium steel member 3 and the ceramic member 2 shown in the figure is obtained.

In the joined body 4, the length of the ceramic member 2 is 1
The ceramic member 2
It has been confirmed that the pores of s are fully filled with chrome steel.

As described above, by making the diameter of the pores in the ceramic member 2 have a gradient, the joint between the chrome steel member 3 and the ceramic member 2, that is, the ceramic member 2 in this embodiment.
In almost all of the above, the physical properties and the mechanical properties are changed from the end face 2a to the end face 2b with the combination of ceramics and chrome steel.
Since it changes with a certain gradient toward, it is possible to prevent the deterioration of durability due to the rapid change of those properties.

Further, the ceramic member 2 has the electric conductivity as described above, and since the fine pores thereof are filled with chrome steel, the entire bonded body 4 exhibits good conductivity, whereby the bonded body 4 It enables electric discharge machining.

In this case, the electrical conductivity of the ceramic member 2 that is the joint portion changes with a certain gradient as it is compounded with the chromium steel, so that the ceramic member 2 does not generate high heat during electric discharge machining.

It is also possible to perform electric discharge machining on the ceramic member 2 alone.

If the ceramic member 2 is provided with conductivity by using the conductive ceramic powder as described above, it is effective in avoiding the thermal deterioration when the joined body 4 is used at a high temperature.

FIG. 5 shows the relationship between the TiN blending amount and the electrical conductivity in the ceramic member 2, and it is clear that the electrical conductivity increases as the TiN blending amount increases.

Example II

In a cylinder head for an internal combustion engine, a method of manufacturing an intake valve seat as a ceramic member joined to the cylinder head body will be described.

As a pore-forming substance, SiO ₂ 27.3 wt% B ₂ O ₃ 39.8 wt% Al ₂ O ₃ 6.1 wt% MgO 4.5 wt% K ₂ O 4.6 wt% Na ₂ O 1.32 wt% BaO 2.0 wt% MoO ₂ 0.2 wt% CeO ₃ 2.3% by weight is used to obtain a glassy powder.

Silicon nitride powder Maximum diameter 4 μm, average diameter 0.5 μm 49.5% by weight Conductive ceramic powder Maximum diameter 10 μm, average diameter 0.8 μm TiB ₂ 20% by weight Pore forming substance Average diameter 10 μm 20% by weight Sintering aid powder diameter 0.1-1.0 μm, Al ₂ O _{3 with} an average diameter of 0.4 μm and diameter
0.25% by weight of Y ₂ O ₃ with 0.1 to 2.0 μm and average diameter of 0.5 μm
0.5% by weight Ammonium borate 10% by weight, organic wax, dispersant, etc. are added and mixed well to obtain a mixed powder. Using this mixed powder, a pressure molding method with a die is applied to obtain a molding pressure of 100 MPa. The annular molded body 5 shown in FIG. 6 is obtained. The dimensions of the molded body 5 are as follows. That is,
Outer diameter of _one annular end surface 5a d ₁ = 34.1 mm, its inner diameter d ₂ = 22.7
mm, the inner diameter d _{3 of} the other annular end surface 5 b = 21.1 mm, its outer diameter d ₄ =
It is 31.6 mm.

After the molded body 5 is dried, it is placed on the base of the sintering furnace with one of the annular end surfaces 5a facing upward, and the N ₂ flow rate of 40 ml / min, 1
Under the condition of time, the molded body 5 is subjected to an organic component removal treatment.

Subsequently, the molded body 5 is subjected to primary sintering treatment under the conditions of N ₂ flow rate of 50 ml / min, 0.6 Torr, 1200 ° C. and 2 hours to obtain a sintered body.

4N HNO ₃ and 0.1% HF heated to 40 ℃
It has a three-dimensional network structure by immersing it in an acid solution consisting of and leaching the acid solution for 16 minutes while applying ultrasonic vibration of 16 MHz to elute the pore-forming component, impurities and excess sintering additive component. Get the valve seat.

The valve seat is thoroughly washed and dried, and then subjected to secondary sintering by HIP treatment under N ₂ atmosphere at 500 atm and 1750 ° C. for 1 hour to highly advance sintering. Get the valve seat. This is designated as the first valve seat 6 (FIG. 7).

The same secondary sintering treatment as described above is performed on the sintered body after the primary sintering treatment similar to the above, and the acid elution treatment similar to the above is performed on the sintered body after the secondary sintering treatment to generate the second valve. Get the sheet.

The dimensional changes in the outer shape and inner diameter and the total linear shrinkage in the first and second valve seats are as shown in the table below.

In the first valve seat 6, the maximum diameter of pores on one annular end surface 6b side is as large as about 300 μm, and the maximum diameter of pores on the other annular end surface 6a side is fine at 1 μm or less, and the diameter of one pore is one. It becomes gradually smaller as it goes away from the annular end face 6b.

In the second valve seat, the maximum diameter of the pores is 500 μm on one annular end surface (corresponding to 6b) side, or the maximum diameter of the pores is 3 μm or less on the other annular end surface (corresponding to 6a) side. The change has the same tendency as that of the first valve seat 6.

FIG. 8 shows the relationship between the porosity and electrical conductivity of each part of the valve seat.

Line y ₁ is the first valve seat 6 containing 20% by weight of TiB _2.
The electric conductivity is almost constant at the site where the porosity is in the range of about 5 to about 60%, but the porosity is about 60 to 60%.
The electric conductivity tends to drop sharply in the area of about 80%.

In FIG. 8, the line y ₂ shows the TiB ₂ content of 40% by weight, and the line y ₃ shows
Indicates that the content of TiB ₂ is set to 5% by weight. The blending amount of the silicon nitride powder is reduced or increased according to the increase or decrease of TiB ₂ .

In this case, the content of TiB ₂ is appropriately 20 to 40% by weight.
This is because, if the amount of TiB ₂ exceeds 40 wt%, TiB ₂
Sintering of the ceramic powder, which is the main component, is hindered, and the strength of the ceramic member is reduced.On the other hand, if the content is less than 20% by weight, the electrical conductivity changes due to the change in the porosity, and the electrode becomes Partial heat generation may occur, which may lead to the introduction of extreme defects, so that electrical discharge machining cannot be performed efficiently.

FIG. 9 shows the cylinder head 7, and the method of casting the cylinder head 7 is as follows.

First, the exhaust valve seat 8 is manufactured using the same method as the first valve seat 6.

Next, after subjecting both valve seats 6 and 8 to predetermined processing, they are preheated to 800 ° C., and the annular end surfaces 6b and 8b of the intake and exhaust sides are sucked and directed toward the exhaust ports 9 and 10, respectively. The valve seats 6 and 8 are installed in the mold, the temperature of the molten aluminum alloy (JIS AC4C) is 700 ℃, and the filling pressure of the molten metal is
When the cylinder head body 11 was constructed under the condition of 200 kg / cm ² , it was confirmed that the pores of each valve seat 6, 8 were sufficiently filled with aluminum alloy.

It is possible to apply electric discharge machining to machining both valve seats 6 and 8, and this electric discharge machining may be performed after the cylinder head 7 is cast.

The present invention is not limited to the valve seat, and is applied to various members such as a turbine impeller joined to a metallic rotating shaft and a slipper surface structure joined to a metallic rocker arm body.

C. Effect of the Invention According to the present invention, since the diameter of the pores in the ceramic member has the gradient as described above, the pores are partially filled with the metal member and the metal member and the ceramic member are joined. At this time, in the joint portion of both members, the physical property and the mechanical property change from the joint surface of the ceramic member to the entire joint portion with a certain gradient due to the compounding of the ceramic and the metal. It is possible to relieve the changes in both properties of the joint portion and significantly improve the durability of the joint portion.

Moreover, since the ceramic member has a predetermined electric conductivity,
It becomes possible to perform electric discharge machining on the single body or a joined body with a metal member, and thereby it is possible to improve machining efficiency.

Further, since conductivity is imparted to the ceramic member by the conductive ceramic component, it is possible to avoid the thermal deterioration when the joined body is used at high temperature.

[Brief description of drawings]

FIG. 1 is a perspective view of the molded body, FIG. 2 (a) is a cross-sectional view of the ceramic member, and FIG. 2 (b) shows the relationship between the distance from one end face of the ceramic member and the porosity and the maximum diameter of the pores. The graph which shows, FIG. 3 is the graph which shows the relationship between the porosity and bending strength in a ceramic member, FIG. 4 is the perspective view of a joined body,
Fig. 5 is a graph showing the relationship between the amount of TiN compounded in the ceramic member and the electrical conductivity, Fig. 6 is a sectional view of the molded body, Fig. 7 is a sectional view of the valve seat, and Fig. 8 is a porosity of the valve seat. And FIG. 9 is a cross-sectional view of the cylinder head. 2 ... Ceramic member, 2a ... End face as joint surface, 3
...... Chromium steel member, 6 …… Valve seat, 6b …… Annular end face as joint surface, 11 …… Aluminum alloy cylinder head body

Claims (1)

[Claims] 1. A ceramic member to be joined to a metal member, which has a three-dimensional network structure containing a conductive ceramic component and having innumerable fine pores filling a part of the metal member, A ceramic member for joining with a metal member, characterized in that the diameter of the pores is gradually reduced with increasing distance from the joining surface with the metal member.