JPH08215579A - Production of metal carrier for catalyst device - Google Patents

Abstract

PURPOSE: To provide a production method of a stable honeycomb body in which the depth of the part influenced by brazing is controlled to prevent cracks in the plate material due to thermal stress and to prevent decrease in the oxidation resistance of the plate material. CONSTITUTION: This metal carrier for a catalyst device is produced by forming flat plates and wavy plates from thin metal plates of a ferrite heat-resistant alloy containing Al and then melting a brazing material in a furnace to join the flat plates and wavy plates to form a honeycomb body having lots of mesh- like air passages. In this method, the plates in a high vacuum furnace are heated while the furnace temp. is maintained at the preheating temp. c1 which is lower by about 50 deg.C than the solid phase line temp. cm of a Ni-based brazing material for specified T1 preheating time so that the temp. in the furnace near the outside (shown as a solid line) coincides with the center temp. (broken line) at point P2 in the graph. Then furnace is further heated to join the plates at the specified joining temp. c3 for specified joining time T2 . The temp. c3 is determined to be higher than the solid phase line temp. cm of the brazing material and lower than the temp. cn which higher by 50 deg.C than the liquid phase line temp. The heating rate is >=6 deg.C/min and the cooling rate is >=1 deg.C/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal carrier for a catalyst device which constitutes a honeycomb body used in an exhaust gas purifying device for an internal combustion engine.

[0002]

2. Description of the Related Art In a conventional method for manufacturing a metal carrier for a catalyst device used in an exhaust gas purifying apparatus, a thin metal flat plate having a thickness of 50 μm to 100 μm and a corrugated plate are integrally brazed together at a contact point. Bonded to form a honeycomb body. A nickel-based brazing material is used as the brazing material, and a heat resistant ferritic stainless steel material is used as the flat plate and the corrugated plate. A high-vacuum furnace is used for brazing the plate material, and the furnace is usually heated to a temperature above the liquidus temperature of the brazing material to melt the brazing material, and brazing is performed at the joint portion of the plate materials.

A catalyst supporting layer made of alumina or the like is formed on the surface of the honeycomb passages of the honeycomb body thus formed, and a catalyst device for purifying exhaust gas by supporting a noble metal catalyst on the catalyst supporting layer is formed. Was there. The catalyst device is arranged in the exhaust passage of the internal combustion engine and is used for HC and C in the exhaust gas.
Purifies O, NO _x, etc.

The honeycomb body is exposed to high-temperature exhaust gas and repeatedly expands and contracts, and the thermal stress concentrates particularly on the brazing portion, so that the brazing portion may crack and eventually fall off. is there. In this brazing part,
Since the plate material is heated to a temperature above the melting temperature of the brazing material, that is, above the liquidus temperature of the brazing material,
As shown in FIG. 4A, the brazing-affected parts 34, 3 due to liquid phase diffusion of the brazing material over the entire thickness of the flat plate 31 and the corrugated plate 32.
4 ₁ is formed.

In order to reduce the thermal stress caused by the expansion and contraction of the plate material due to the above-mentioned high temperature exhaust gas, FIG.
As shown by the partial sectional schematic view of (A), the honeycomb body in which a portion of the flat plate doubly is disclosed, two flat 31 and 31 ₁ are adapted to be movable to one another.

Further, in order to improve the oxidation resistance of the plate member of the honeycomb body at a high temperature, the ferrite stainless material forming the plate member of the honeycomb body shown in FIG.
Material containing aluminum, eg (Fe + 20Cr +
Although stainless steel consisting 5Al) is used, in case of bonding by the brazing material of these plate nickel-based, the braze-affected zone 34, 34 ₁ formed plate, nickel and aluminum intermetallic compound ( for Ni ₃ Al) is deposited, the aluminum is consumed that a solid solution in the base material 36 in _1, the base material of the joint portion for the 36, 36
It is observed that the aluminum content in ₁ is reduced.

Since the above-mentioned melting of the brazing filler metal is usually carried out in a high vacuum furnace, the honeycomb body in the furnace is heated by radiant heat and is not heated by conduction and convection. Therefore, there is a difference in heating temperature between the outer portion of the furnace near the heat source and the central portion of the furnace. That is, as shown in the temperature vs. time diagram of FIG. 6, the gradient of the heating line h _{1 at} the outside of the furnace shown by the solid line is steeper than the gradient of the heating line h _{2 at} the center of the furnace shown by the broken line. Therefore, the joining time at the joining temperature C ₅ of the brazing material is T for the honeycomb body arranged in the outer portion of the furnace.
_4, always T ₄ becomes T ₅ is longer than T ₅ against the honeycomb body disposed in the furnace center portion, resulting in differences in the amount of diffusion of brazing material in the outer portion and the central portion of the furnace for this purpose. The difference becomes particularly remarkable when the heating rate is high or when the brazing time is short.

[0008]

As shown in FIG. 4 (A), the conventional method of manufacturing a metal carrier for a catalyst device described above will spread the entire thickness of the plate materials 31, 32 by liquid phase diffusion of the brazing material. put-affected zone 34, 34 ₁ appears, the boundary line a, before and after a ₁ as shown in FIG. 4 (B), to produce the extreme differences in hardness distribution of the base material 36, the heat in the vicinity of the boundary line There is a drawback that stress concentrates and causes cracks to occur, and as a measure taken to relieve thermal stress, FIG.
In the double plate structure shown in (B), the second flat plate 3
To diffuse the brazing material to a 1 _1, two flat 31,3
There is a drawback in that it is difficult to slip between 1 ₁ and the advantages of the flat plate double structure cannot be utilized, and in the joint part where the plate material of ferritic stainless steel containing aluminum is joined with the nickel-based brazing material Aluminum which is a solid solution in the base material is an intermetallic compound (Ni ₃ A
Since it is consumed as l), there is a drawback that the aluminum content of the plate material is reduced and the plate material is easily oxidized, which causes abnormal oxidation. Further, when the honeycomb bodies are bonded using a high vacuum furnace, Due to the difference in temperature rise between the outer part and the center part of the furnace, the size of the above-mentioned brazing-affected zone formed at each of the joint part of the outer part and the center part of the furnace, There is a drawback that the quality is not stable due to the difference in the amount of diffusion.

Further, the higher the heating rate and the cooling rate of the furnace, and the shorter the brazing time, the more the diffusion amount of the brazing filler metal can be limited. There is a drawback that the temperature difference in the central portion becomes large.

Further, there is a method of joining by setting the brazing temperature to a temperature lower than the liquidus temperature of the brazing material. According to this method, the brazing time can be extended, and the diffusion depth of the brazing filler metal at the joint can be made uniform, so that uneven quality does not occur easily. It is necessary to set the temperature just below the phase line temperature. Therefore, there is a drawback in that a slight difference in melting point due to variation in composition of the brazing material from lot to lot causes a difference in the diffusion amount.

An object of the present invention is to provide a honeycomb body by joining plate materials of a ferritic heat-resistant alloy containing aluminum with a nickel-based brazing material to form a honeycomb body,
Prevents cracking of the plate by preventing the brazing-affected zone from joining to the total thickness of the plate, and the brazing-affected zone does not impair the function of the flat plate double structure, and prevents the acid resistance of the plate at the joint. A method for producing a metal carrier for a catalyst device, which can minimize the precipitation of intermetallic compounds that cause the loss of chemical property, and stabilize the quality of the bonded portion of the honeycomb body by making the temperature inside the vacuum furnace as uniform as possible. To provide.

[0012]

A method of manufacturing a metal carrier for a catalytic device according to the present invention comprises forming a flat plate and a corrugated plate of a predetermined shape from a thin metal plate of a ferritic heat-resistant alloy containing aluminum, and alternately forming them. A catalyst for forming a honeycomb body having a large number of mesh-like ventilation passages by interposing a nickel-based brazing filler metal in a portion overlapping with each other In the method of manufacturing a metal carrier for an apparatus, the inside of a furnace charged with a flat plate and a corrugated plate is heated and heated at a preset preheating temperature for a preset preheating time so that the temperature distribution in the furnace becomes uniform. After the temperature in the furnace becomes uniform, the furnace is heated again to keep the temperature of the furnace at the joining temperature set above the solidus temperature of the brazing material and below the liquidus temperature by 50 ° C.
After the preset bonding time has elapsed at the bonding temperature, the furnace is cooled to bond the honeycomb bodies.

The above-mentioned preheating temperature is preferably set to a temperature lower than the solidus temperature of the brazing material by about 50 ° C., the preheating time is preferably set to 10 to 120 minutes, and the joining time is set to 0. It is desirable to set the time to minutes to 90 minutes.

Further, in the above manufacturing method, in order to suppress the diffusion depth of the brazing filler metal into the base metal to be less than the plate thickness of the base metal, a heating rate of 6 ° C./min or more and 1 ° C./min. It is desirable to provide the above cooling rate.

[0015]

The temperature in the furnace at the time of joining is made uniform by preheating the furnace containing the honeycomb body at a constant temperature set to 50 ° C. lower than the solidus temperature of the brazing material for 10 to 120 minutes. Therefore, it is possible to eliminate the variation in the size of the brazing-affected zone formed at the joint, and the joining temperature of the brazing material at the time of joining is not less than the solidus line of the brazing material and 50 from the liquidus temperature. By setting the temperature to a temperature higher by ℃, the bonding time to 90 minutes or less, the heating rate up to the bonding temperature is 6 ° C. or more per minute, and the cooling rate after bonding is 1 ° C. or more per minute, The diffusion depth of the brazing material can be suppressed to a desired value less than the plate thickness of the base material, and the diffusion amount of the brazing material can be controlled.

[0016]

EXAMPLES Next, production of a metal carrier for a catalyst device of the present invention
The method will be described with reference to the drawings. FIG. 1 shows the invention
In a furnace of an embodiment of a method for producing a metal carrier for a catalytic device,
Fig. 2 (A) is a diagram showing the relationship between temperature and time
A cross-sectional schematic view of the joined portion of the honeycomb body by the manufacturing method of Ming,
FIG. 2B is the Y-Y of the flat plate of FIG.₁ Hardness on the line
In FIG. 1, which is a diagram showing a cloth, the vertical axis represents temperature c and the horizontal axis.
The axis represents the time t, the solid line is the outer part of the furnace, and the broken line is the furnace.
It shows the relationship between temperature and time in the central part of the. each
The point P on the line is represented by the coordinates (c, t).
The solid line representing the temperature-time relationship of the outer part of the furnace is
1-step heating wire h_0-1 , Preheating line h_1-2 , 2nd stage heating wire h
_2-3 , Joining line h_3-5 And cooling line h_5-7 Than each part of
And the point P on the line with the passage of time t ₀ (C₀ , T₀ ),
P₁ (C₁ , T₁ ), P₂ (C₁ , T₂ ), P₃ (C
₃ , T ₃ ), P_Five (C₃ , T_Five ), P₇ (C₀ , T₇ )
Pass through. Shows the temperature-time relationship in the center of the furnace.
The dashed line indicates the first-stage heating line h_0-2 , 2nd stage heating wire h_2-4 ,
Joining line h_4-6 And cooling line h_6-7 Each part of
Point P on the line with the passage of time t₀ (C₀ , T₀ ), P₂ 
(C₁ , T₂ ), P_Four (C₃ , T_Four ), P₆ (C₃, T₆
 ), P₇ (C₀ , T₇ ).

The reason why there is a temperature difference between the outer portion of the furnace and the central portion of the furnace as described above is that a high vacuum furnace is used to prevent oxidation of the joint portion due to brazing of the plate materials.
In a vacuum furnace, the honeycomb body charged in the furnace is heated by the radiation from the heat source, and conduction and convection do not work.Therefore, the temperature distribution in the furnace is close to the heat source outside the furnace and in the center of the furnace. Makes a difference between and. That is, P ₀ (c
When heating from the state of ( ₀ , t ₀ ), the outer part of the furnace is heated by radiation and rises along the first-stage heating line h _0-1 while the central part of the furnace is higher than the heat source. Since it is far, the temperature rise is delayed and rises along the first stage heating line h _0-2 .

As described above, in the vacuum furnace, the temperature rise of the outer portion of the furnace is faster than the temperature rise of the central portion of the furnace. Therefore, in the manufacturing method of the present invention, the temperature rise of the outer portion is temporarily suppressed and the temperature of the central portion of the furnace is reduced. Take the method of waiting for the temperature to rise. That first stage heating line h _{0- 1} on at time t ₁ after the temperature c
_At the point P ₁ when reaching ₁ , the heating in the furnace is stopped or adjusted so that the point P ₁ does not rise above the temperature c ₁ ,
The first stage heating line h _0-2 of the central part of the furnace is the time (t ₂ −t ₁ =
T ₁ ) After reaching the temperature c ₁ , a uniform furnace temperature c ₁ is obtained. Here, the temperature c ₁ is the preheating temperature, the time (t ₂ −
Let t ₁ ) be the preheating time T ₁ . The preheating temperature c ₁ is usually set to about 50 ° C. lower than the solidus temperature _{cm of the} brazing material in consideration of the overshoot of the furnace (shown by the curve h ₈ ) and the variation of the thermocouple. A solid line h connecting points P ₁ and P _2
Reference numeral _1-2 is a preheating line, which shows the relationship between the outermost temperature in the furnace and the time during the preheating time T ₁ . Preheat time T
The length of ₁ varies depending on the conditions such as the size of the furnace and the object to be heated, and is set by experiment, and usually 10 minutes to 1
It is a value of 20 minutes.

A uniform temperature is maintained between the outer part and the central part of the furnace.
When P₂ At the second stage, if the inside of the furnace is heated again,
Heating wire h_2-3 And h_2-4 As shown in the outer part of the furnace
And the central part have a very large time difference (t_Four -T₃ ) Live
Without joining, brazing temperature c ₃ Point P on the line₃ And P_Four To
Can be reached Bonding temperature c₃ Solidus temperature of brazing filler metal
Degree c_m Higher and liquidus temperature + 50 ° C temperature c_n Than
Set low.

In the above-described temperature-time relationship indicated by the first heating line h _0-1 and the second heating line h _2-3 , the diffusion depth of the brazing filler metal into the base metal is determined by the plate of the base metal. A heating rate of 6 ° C. or more per minute is desirable in order to keep the thickness below the range.

In joining with a brazing material, the base material of the brazing material
Value of diffusion depth of 20 μm or less than the base metal plate thickness
In order to limit the₂ of
During the period, the temperature inside the furnace is kept constant at the junction temperature c₃ Hold on. And
The relationship between temperature and time of the outer part of the kiln is point P₃ And P_Five 
Joining line h connecting_3-5 (Solid line). Heart of the furnace
A constant junction temperature c₃ Is maintained at the joining time T₃ Is outside
Joining time T of the side part₂A slight time delay (t_Four −
t₃ ), (T₆ -T_Five ), The point P_Four And P₆Connection
Joining line h_4-6 (Dashed line) shows the relationship between temperature and time
It However, time delay (t_Four -T₃ ) And (t₆ 
-T_Five ) Is the welding time T of the outer part ₂ And the heart
Minute joining time T₃ Smaller than the outer part and inner part
There is no difference in the joining time of the parts, and it can be applied to the diffusion depth of the brazing material.
Does not make a difference.

After the predetermined joining time T ₂ of 90 minutes or less has elapsed, the supply of the heat source to the furnace is shut off and the cooling line h
_The furnace is cooled along _5-7 and h _6-7 . The cooling rate at this time is preferably 1 ° C. or more per minute in order to stop the diffusion of the brazing material.

Contact of the honeycomb bodies thus joined together
As shown in the partial sectional view of FIG.
1 and the corrugated sheet 2 are joined by a brazing material 3,
Brazing affected by diffusion of 3 and 4, 4₁ Is being generated
It This brazing influence part 4, 4₁ Depth of 20 μm or less
Above the total thickness of flat plate 1 and corrugated plate 2 which are base materials
Experimentally set the above temperature and time to obtain the desired value
I do. Therefore, even at the joint portion, the slave of FIG.
Brazing-affected parts 34, 34 as shown in the conventional example ₁ And parent material
36,36₁ Boundary line across the base metal seen between and
a, a₁ , B, b ₁ However, it is not generated in this embodiment.
Therefore, the strength of the plate material is discontinuous in the longitudinal direction of the base metal cross section.
It does not become cracked and does not easily crack due to expansion and contraction due to heat
In addition to maintaining the
₁ Intermetallic compound (Ni₃Al) is shown in FIG.
Since it is formed to be rougher than the conventional example shown in FIG.
On the cross section of₁ Hardness distribution at the boundary on the line
However, as shown in Fig. 2 (B), it shows a line with a gentle slope.
Therefore, the boundary does not become discontinuous in terms of strength, and therefore
Thermal stress is less likely to concentrate, and cracks can be prevented from occurring.

When the method of the present invention is applied to a honeycomb body having a double plate structure, as shown in FIG.
Brazing affected part 4 stays inside flat plate 1 and
Since it does not reach the surface of the _first flat plate 1 ₁ , the slip between the two flat plates 1 and 1 ₁ is not hindered, and therefore the characteristics of the flat plate double structure are not lost.

Further, according to the joining method of the present invention, the size of the brazing-affected zone is extremely large in the joining portion where the ferritic stainless steel plate material containing aluminum for oxidation prevention is joined with the nickel-based brazing material. Since it can be limited to a small value, it becomes possible to limit the consumption of aluminum in the base material as an intermetallic compound (Ni ₃ Al) in the brazing affected zone to the utmost, and the abnormal oxidation of the joint portion of the plate material. Can be suppressed.

[0026]

As described above, according to the present invention, when a thin flat plate of a ferrite heat-resistant alloy containing aluminum and a corrugated plate are superposed and joined together by using a nickel-based brazing material to form a honeycomb body, While heating the furnace with the corrugated sheet and the corrugated plate, at the preset preheating temperature, adjust the heating of the furnace for the preset preheating time to make the temperature in the furnace uniform and then heat the furnace further. Since the brazing filler metal is joined together by the joining process, there is no temperature difference between the outer part and the central part of the furnace during brazing, which makes it possible to shorten the brazing time and increase the heating rate, and to spread the brazing filler metal. It becomes possible to suppress uniformly, and further, by setting the joining temperature and the joining time of the brazing filler metal to values within a certain range, and by setting the heating rate and the cooling rate to above a certain value, Cormorants wood because the depth of diffusion into the base material can be controlled to less than the thickness of the base material, the effect of improving the quality.

That is, since the precipitation amount of the intermetallic compound of aluminum can be reduced, the oxidation resistance life of the plate material becomes longer than before, and the intermetallic compound is coarsely formed, so that the hardness distribution near the boundary line is gentle. Therefore, the concentration of thermal stress is prevented and cracks are less likely to be generated in the plate material.Because the brazing-affected zone does not cover the entire thickness of the plate material, there is no boundary line that crosses the entire thickness of the plate material. This has the effect of making cracks less likely to occur. Further, in the flat plate double structure, since the brazing-affected zone of the first flat plate does not extend to the second plate, slippage between the two flat plates is not obstructed and the characteristics of the flat plate double structure are impaired. There is an effect that it is exhibited without.

[Brief description of drawings]

FIG. 1 shows a method for producing a metal carrier for a catalyst device according to the present invention,
It is a diagram which shows the temperature in a furnace, and the relationship of time.

FIG. 2A is a schematic diagram of a schematic cross section of a joined portion of a honeycomb body manufactured by the manufacturing method of the present invention. Figure 2 (B) is
Is a graph showing the hardness distribution of the Y-Y ₁ line of flat plate (A).

[Fig. 3] Fig. 3 is a schematic cross-sectional view of a joined portion of a flat-plate double-structured honeycomb body manufactured by the manufacturing method of the present invention.

FIG. 4A is a schematic diagram of a schematic cross section of a bonded portion of a honeycomb body according to a conventional technique. 4B is a diagram showing the hardness distribution on the line XX ₁ of the flat plate of FIG.

FIG. 5 (A) is a schematic cross-sectional view of a joined portion of a honeycomb structure having a flat plate double structure according to a conventional technique. FIG. 5B is a schematic view in which the brazing material is diffused on the second flat plate in FIG. 5A.

FIG. 6 is a diagram showing a relationship between temperature in a furnace and time in a manufacturing method according to a conventional technique.

[Explanation of symbols]

1,31,31 ₁ flat 2,32-wave plate 3,33 braze 4,4 _1, 34, 34 ₁ brazed affected zone 6,6 _1, 36 ₁ preform a, a _1, b, b ₁ border c temperature c ₀ beginning of temperature c ₁ preheating temperature c _3, c ₅ junction temperature c _m solidus temperature c _n liquidus temperature + 50 ℃ temperature h ₁ heating line (furnace outer part) h ₂ heating line ( Furnace center part) h _0-1 , h _0-2 1st stage heating wire h _2-3 , h _2-4 2nd stage heating wire h _1-2 Preheating wire h _3-5 , h _4-6 Joining wire h _5-7 , h _6-7 Cooling line t Time Point on P coordinate (c, t) T ₁ Preheating time T ₂ , T ₃ , T ₄ , T ₅ Joining time

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B23K 35/30 ZAB B23K 35/30 310D 310 B01D 53/36 ZABC

Claims (4)

[Claims] 1. A flat plate and a corrugated plate having a predetermined shape are formed from a thin metal plate of a ferritic heat-resistant alloy containing aluminum, and the flat plate and the corrugated plate are alternately stacked, and nickel-based parts are provided at portions where they abut each other. Manufacture of a metal carrier for a catalyst device in which a brazing material is inserted into a furnace to melt the brazing material and the flat plate and the corrugated plate are joined to form a honeycomb body having a large number of mesh-like ventilation passages. In the method, heating the inside of the furnace charged with the flat plate and the corrugated plate, at a preset preheating temperature, heating for a preset preheating time so that the temperature distribution in the furnace becomes uniform, After the internal temperature becomes uniform, the furnace is heated again to maintain the temperature of the furnace at the bonding temperature set above the solidus temperature of the brazing material and below the liquidus temperature by 50 ° C. , Preset at the joining temperature After a lapse of bonding time and, by cooling the furnace perform bonding the honeycomb body, the joining method of the metal carrier for a catalytic device. 2. The metal for a catalytic device according to claim 1, wherein the preheating temperature is set to a temperature about 50 ° C. lower than the solidus temperature of the brazing material, and the preheating time is set to 10 to 120 minutes. Method for producing carrier. 3. The method for producing a metal carrier for a catalyst device according to claim 1, wherein the joining time is set to 0 to 90 minutes. 4. A heating rate of 6 ° C. or more per minute and a cooling rate of 1 ° C. or more per minute are applied to the joining portion.
The method for producing a metal carrier for a catalyst device according to item 1.