JP3358633B2 - Sealing method of cell part of oxygen sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sealing a cell portion of an oxygen sensor, and more particularly, to a method for sealing a stabilized zirconia in a cell portion of an oxygen sensor and a mounting bracket made of a corrosion resistant alloy. It relates to a sealing method.

[0002]

2. Description of the Related Art At present, an oxygen sensor using stabilized zirconia in which a predetermined amount of yttria or the like is dissolved as a stabilizer is known as a boiler, a process heater, an inert gas generator, a cement kiln, a lime kiln, It is used in glass melting furnaces, heating furnaces, soaking furnaces, heat treatment furnaces, reducing atmosphere furnaces, blast furnaces, etc., and is used under harsh environments such as corrosive gas, high temperature and high humidity. The oxygen sensor for these is, for example, a cell part of stabilized zirconia containing up to 8 mol% of Y ₂ O ₃ and a fitting made of a corrosion-resistant alloy, for example, a nickel alloy such as Hastelloy (registered trademark) . The flange is attached with an inorganic adhesive.

The oxygen sensor using the stabilized zirconia is configured to measure the oxygen concentration by utilizing the difference in electromotive force caused by the difference in oxygen concentration between the reference gas and the measurement gas existing inside and outside the cell partition. Therefore, the quality of the airtightness of the sealing portion between the cell member and the mounting bracket greatly affects the measurement accuracy of the oxygen concentration.

However, in the conventional oxygen sensor which has been sealed using an inorganic adhesive, poor airtightness is apt to occur in the sealed portion, and the yield is poor, which tends to cause an increase in cost. The leaktightness is 1 ×
Since it is very poor at 10 ^-2 atm · cc / sec, the measurement accuracy of the oxygen concentration, especially the concentration in the atmosphere under a low concentration of ppm order 2
The measurement accuracy of the oxygen concentration under high concentrations of around 1% and around 100% is poor, and it becomes difficult to measure the oxygen concentration with high accuracy.

[0005] Furthermore, because of poor airtightness, when used in an atmosphere of corrosive gas, corrosive gas enters the inside of the sensor, corrodes internal devices and causes failure, and the durability of the oxygen sensor decreases. There was an inconvenience of lowering.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned technical circumstances, and has improved airtightness and durability. It is an object of the present invention to provide a highly durable oxygen sensor which can measure the concentration with high accuracy, has less troubles, and a method for manufacturing the same.

[0007]

According to the present invention, at the time of sealing between a stabilized zirconia member in a cell portion of an oxygen sensor and a fitting made of a corrosion-resistant alloy, at least one of the fittings made of a corrosion-resistant alloy is used. On the surface forming the sealing part,
After forming a coating film made of a nickel alloy containing an active metal, a sealing portion formed between the stabilized zirconia member and a mounting bracket made of a corrosion-resistant alloy having the coating film formed thereon is formed. A method for sealing a cell portion of an oxygen sensor, wherein a sealing material made of aluminosilicate glass is filled and heated to a temperature equal to or higher than the softening point of the sealing material. .

Here, the formation of the coating film made of a nickel alloy containing an active metal is intended to improve the wettability of the aluminosilicate glass to the corrosion resistant alloy, and by improving the wettability, Both can be well sealed with an aluminosilicate glass. For example, by forming the coating film before sealing, the contact angle between the molten aluminosilicate glass and Hastelloy (registered trademark) is set to 110.
From 70 degrees to 70 degrees (improvement of wettability), and sealing with greatly improved airtightness and durability of the sealing portion can be performed. In the present invention, the active metal is defined as T
i, Zr, Hf, Cr, Be, etc. TiH _2, ZrH _2, referred to a compound containing a very active metal to oxygen.

Further, as means for forming the coating film, C
Known means such as a VD method, a sputtering method, and a thermal spraying method can be adopted. From the viewpoint of partial coating on an inner surface such as a sealing portion, a third aspect is described below.
It is preferable to employ the means described in (1). The heat treatment time for sealing with the aluminosilicate glass is preferably 15 minutes or more, and the heat treatment atmosphere is preferably an inert gas atmosphere, for example, a nitrogen atmosphere. In an oxidizing atmosphere, the corrosion-resistant alloy is oxidized at the time of sealing, and in a vacuum atmosphere or a reducing atmosphere, the sealing material foams and the sealing portion becomes porous, which is not preferable.

[0010] Further, the heat treatment temperature for sealing with the aluminosilicate glass is preferably about 100 to 150 ° C higher than the softening point of the aluminosilicate glass as the sealing material. The viscosity becomes moderate,
It is suitable from the viewpoint of sealing properties. Further, the softening point of the aluminosilicate glass is preferably 400 ° C. or higher. The reason is that the tip of the cell of the oxygen sensor is heated to approximately 750 ° C. for measuring the oxygen concentration, and the temperature of the sealing portion rises to approximately 350 ° C. accordingly. The aluminosilicate glass used as a sealing material has a softening point of 40.
If the temperature is lower than 0 ° C., the cell portion may be detached from the mounting bracket. As described above, the airtightness and the durability are improved, the oxygen concentration can be measured accurately even at a low concentration or a high concentration, and a highly durable oxygen sensor with less failure can be manufactured.

The coating film made of a nickel alloy containing an active metal includes at least one of the active metals,
It is preferable to contain 0.5 to 30% by weight in total. Here, when the content of the active metal is less than 0.5% by weight, the effect of improving the wettability with the aluminosilicate glass tends to decrease, while the content of the active metal exceeds 30% by weight. In addition, the obtained coating film becomes brittle, the coefficient of thermal expansion becomes lower than that of a corrosion-resistant alloy as a base material, and cracks occur or peel off, which is not preferable.

Further, the coating film made of a nickel alloy containing an active metal contains at least one of the active metals in a total amount of 0.5 to 30% by weight, and contains phosphorus (P) in an amount of 20% by weight or less. It is preferable to contain. That is, phosphorus (P) is further added to a nickel alloy containing an active metal by 20%.
The addition of not more than% by weight is intended to lower the melting point of the nickel alloy containing the active metal, to improve the fluidity during melting and to facilitate the formation of the coating film, and to contain phosphorus (P). If the amount exceeds 20% by weight, the obtained coating film becomes brittle and peels off, which is not preferable.

[0013] The means for forming the coating film includes a nickel alloy powder containing an active metal or a mixed powder containing at least an active metal and nickel on at least a surface of a fitting made of a corrosion resistant alloy on which a sealing portion is formed. Is applied by an appropriate method, and is heat-treated in a non-oxidizing atmosphere at a temperature equal to or higher than the melting point of the alloy powder or the mixed powder thereof. The temperature for this heat treatment is, for example, 800 to 10
00 ° C. Non-oxidizing atmosphere used, which can be mentioned a reducing atmosphere or a vacuum atmosphere, especially, ^10-4
A vacuum atmosphere at or below Torr is preferred. The formation of the coating film under a vacuum atmosphere improves the flow of the molten active metal-containing nickel alloy and improves the airtightness of the sealing portion.

Further, the composition of the aluminosilicate glass contains 40 to 75% by weight of silica,
35% by weight, further containing MgO, MnO, CaO,
SrO, PbO, BaO, ZnO, Li ₂ O, Na ₂ O,
At least one of K ₂ O and Rb ₂ O in total of 5 to 3
Those containing 0% by weight are preferred. Here, when the silica content of the aluminosilicate glass is less than 40% by weight,
It is difficult to completely vitrify, and when partially crystallized, the composition tends to be non-homogeneous, and when a thermal cycle is applied, cracks are likely to occur due to distortion inside the glass, and the durability tends to decrease. On the other hand, if the silica content exceeds 75% by weight, the thermal expansion coefficient decreases, cracks are likely to occur at the time of cooling after sealing at a high temperature or at the time of measuring the oxygen concentration, and the yield is reduced as a product. Tend to.

If the alumina content of the aluminosilicate glass is less than 3% by weight, the chemical durability against corrosive gas and the like is deteriorated, while the alumina content is 35% by weight.
If it exceeds, the coefficient of thermal expansion decreases, cracks are likely to occur at the time of cooling after sealing at a high temperature or at the time of measuring the oxygen concentration, and the yield as a product tends to decrease.

Furthermore, the heat treatment temperature required for sealing with the aluminosilicate glass should be about 100 to 150 ° C. higher than the softening point of the aluminosilicate glass as the sealing material, and the viscosity of the aluminosilicate glass should be higher. Is appropriate and suitable. The softening point of aluminosilicate glass is 40
0 ° C. or higher is preferred. The reason is that the tip of the cell portion of the oxygen sensor is almost 700 mm for oxygen concentration measurement.
° C, and the temperature of the sealing portion is increased to approximately 35 ° C.
This is because the temperature rises to about 0 ° C. If the softening point of the aluminosilicate glass used as the sealing material is lower than 400 ° C., there is a risk that the cell portion may come off from the mounting bracket.

The thermal expansion coefficient of the aluminosilicate glass is stabilized by the thermal expansion coefficient of zirconia (10 × 10 ⁻⁶ / ° C.).
To match the degree, the aluminosilicate glass must have M
gO, MnO, CaO, SrO, PbO, BaO, Zn
_{O, Li 2 O, Na 2} O, K 2 O, a total of at least one of Rb ₂ O, may be added 5 to 30 wt%, preferably, it has greater than 30 wt% at less than 5 wt% Also, it becomes difficult to match the coefficient of thermal expansion with that of stabilized zirconia,
Cracks tend to easily occur during cooling after sealing at a high temperature or when measuring the oxygen concentration.

Regarding the composition of the aluminosilicate glass,
It contains 40 to 75% by weight of silica, 3 to 35% by weight of alumina, and further contains MgO, MnO, CaO, SrO,
PbO, BaO, ZnO, Li ₂ O, Na ₂ O, K ₂ O,
In total at least one of rb ₂ O, the one containing 5 to 30 wt%, further, a total of at least one of _{B 2 O 3, P 2 O} 5, those containing 15 wt% or less Is preferred. This is added in order to increase the chemical durability against corrosive gas and the like. When the amount added exceeds 15% by weight, the coefficient of thermal expansion decreases, and during cooling after sealing at a high temperature, , Easy to crack when measuring oxygen concentration,
The yield as a product tends to decrease.

As a material of the corrosion resistant alloy forming the mounting bracket, an alloy containing nickel such as Hastelloy (registered trademark) is preferable.

[0020]

[Function] The formation of a coating film made of a nickel alloy containing an active metal improves the wettability of the aluminosilicate glass to the corrosion-resistant alloy, and is made of a stabilized zirconia and a corrosion-resistant alloy of the cell member of the oxygen sensor. Can be better sealed with the aluminosilicate glass, and further contributes to the improvement in the airtightness and durability of the sealed portion, and also improves the product yield.

Further, by specifying the composition of the coating film made of a nickel alloy containing an active metal within the above range, the wettability of the aluminosilicate glass to the corrosion-resistant alloy is further improved, and the solidification is further improved. In addition, it can be more airtightly sealed.

Further, the melting point of the nickel alloy containing the active metal is lowered by adding phosphorus to the composition of the coating film made of the nickel alloy containing the active metal, whereby the fluidity during melting is reduced. To facilitate the formation of a coating film, greatly improve the wettability of the aluminosilicate glass to the corrosion-resistant alloy, and provide a stronger and more airtight seal.

Further, by using a coating film made of a nickel alloy containing an active metal, it is easy to partially coat the inner surface such as a sealing portion.

Further, the tip of the cell of the oxygen sensor is heated to about 750 ° C. for measuring the oxygen concentration. Therefore, the sealing for sealing the stabilized zirconia of the cell member of the oxygen sensor and the mounting bracket made of the corrosion resistant alloy is performed. Since the bonded part is also exposed to a considerably high temperature, the sealing material needs to have excellent heat resistance and thermal shock resistance. Further, since the stabilized zirconia has a coefficient of thermal expansion of 10 × 10 ⁻⁶ / ° C., it is desirable that the sealing material has the same coefficient of thermal expansion. Further, the environment in which the oxygen sensor is used is often a corrosive gas atmosphere, and the sealing material needs to have excellent corrosion resistance. Thus, the aluminosilicate glass as the sealing material sufficiently satisfies these conditions.

Further, the composition of the aluminosilicate glass as the sealing material increases the chemical durability against corrosive gas and the like by specifying the above range.

As described above, according to the sealing method of the present invention, the oxygen sensor has improved airtightness and durability, and can accurately measure the oxygen concentration even at low or high concentrations.
It is possible to provide a highly durable oxygen sensor with few failures.

Next, the method of sealing the cell portion of the oxygen sensor according to the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

[0028]

EXAMPLES Nickel powder having a purity of 99.9%, active metal powder and, if necessary, red phosphorus are shown in the first column of Tables 1 and 2 (composition of coating film) (Nos. 1 to 43). And mixed with screen oil in an agate mortar to form a slurry. This slurry is transferred to a nickel alloy (Hastelloy-
(Registered trademark) is applied to a sealing portion of a mounting bracket, dried at 120 ° C. for 30 minutes by a vacuum drier, and then 800 to 1000 ° C. in a vacuum atmosphere [10 ⁻⁴ torr (torr) or less].
The coating was made of a nickel alloy containing an active metal by performing a heat treatment for 20 minutes in the above temperature range.

On the other hand, aluminosilicate glass as a sealing material was produced as follows. That is, each reagent powder having a purity of 99.9% was prepared so as to have the composition (No. 1 to 43) shown in the second column (composition of the sealing material) in Tables 1 and 2, and using a planetary mill. Crushed for 6 hours and mixed. This mixed powder was put in a platinum crucible, melted in an oxidation furnace, dropped into water, quenched, crushed, and then sized with a 300-mesh sieve to obtain a sealing material according to the present invention.

The above sealing material was mixed with a polyvinyl butyral resin in an agate mortar to form a slurry. The slurry was prepared by using stabilized zirconia, which is a cell member of an oxygen sensor, and a nickel alloy (hastelloy-registered trademark) having a coating film formed thereon.
After filling in the sealing part formed between the mounting bracket made by the mark , and dried at 120 ° C. for 1 hour with a vacuum dryer. Then, it was kept at 350 ° C. for 2 hours in an oxidation furnace, and degreased in glass. Then, in a nitrogen atmosphere, each of the sealing materials (No. 1 to 43) was heat-treated at a temperature 100 ° C. higher than the glass softening point, thereby performing a sealing operation. still,
Stabilized zirconia is conventionally used as Y ₂ as a stabilizer.
It contains 8 mol% of O ₃ .

As described above, an oxygen sensor component (cell member) was manufactured using each of the coating films prepared with the compositions shown in Tables 1 and 2 and the sealing materials (Nos. 1 to 43). The presence or absence of cracks in the wearing member was visually observed, and the third in Tables 1 and 2 was observed.
The results are summarized in the first column (evaluation results). A helium leak detector (manufactured by Nidec Anelva; ASM-
151T, detection limit; 2 × 10 ⁻¹⁰ Torr), and the airtightness was evaluated.

For an oxygen sensor part having good airtightness, as an endurance test, the atmosphere in the furnace was heated in a nitrogen gas containing 10% SO ₂ and 5% O ₂ at a heating rate. 3
After heating to 350 ° C. at 5 ° C./min and holding for 2 hours,
After repeating a heat cycle of cooling to room temperature at a cooling rate of 35 ° C./min and holding for 1 hour 100 times, an airtight test as described above was performed to check for the presence or absence of a leak. The results of this evaluation test are shown in the third durability section in the column of evaluation results.

The results of each evaluation are shown in the third column of Tables 1 and 2 (evaluation results). Tables 1 and 2 show comparative examples (No.
44) is a conventional inorganic adhesive (Sumiceram S-3)
01; trade name). The numbers in the evaluation result column are based on the number of non-defective products,
The number of evaluations is shown in the denominator.

[0034]

[Table 1]

[0035]

[Table 2]

From the above results, the oxygen sensor parts (Nos. 1 to 43) of the present invention showed a detection limit of 2 × 10 ⁻¹⁰ atm · cc /
By seconds, all airtightness was confirmed to be good. Compared with a conventional product sealed by the conventional technique (No. 42, leak amount: 1 × 10 ⁻² atm · cc / sec), airtightness was improved. Gender,
It improved by more than 10 (minus 8th power).

In addition, an oxygen sensor component (N) whose airtightness has been confirmed within the detection limit using a helium leak detector.
o. 1 to 43) confirmed that it was possible to accurately measure the oxygen concentration in the low concentration region up to the oxygen concentration of 1 ppb, and in the high concentration region near the oxygen concentration of 21% and the oxygen concentration of 100%.

In the conventional product (No. 44) sealed with an inorganic adhesive, the airtightness of the sealed portion was poor, and the oxygen concentration was 0.1% or less, the oxygen concentration was around 21%, and the oxygen concentration was 100%. %, The measurement accuracy was poor, and it was confirmed that accurate measurement of the oxygen concentration was difficult.

[0039]

As described above, the following remarkable technical effects have been obtained by the method of sealing an oxygen sensor according to the present invention. First, by forming a nickel alloy coating film containing an active metal, the wettability of the aluminosilicate glass to the corrosion-resistant alloy is improved, and the hermeticity of the sealing portion is greatly improved. In addition, an oxygen sensor capable of accurately measuring the oxygen concentration even under a high concentration was obtained, and an oxygen sensor having a high yield, few failures, and high durability was obtained. Second, according to the method for attaching an oxygen sensor of the present invention, the production cost is reduced and the market for the oxygen sensor is expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a section of a cell portion of an oxygen sensor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stabilized zirconia cell 2 Corrosion-resistant alloy mounting bracket 3 Adhesive material 4 Adhered part 5 Coating film

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-148127 (JP, A) JP-A-3-271173 (JP, A) JP-A-55-104979 (JP, A) JP-A-2- 80381 (JP, A) JP-A-61-236661 (JP, A) JP-A-63-45192 (JP, A) JP-A-6-329480 (JP, A) JP-A-53-37094 (JP, A) JP-A-60-104251 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/409 G01N 27/41 G01N 27/419

Claims (6)

(57) [Claims] When sealing between a stabilized zirconia member in a cell portion of an oxygen sensor and a mounting bracket made of a corrosion-resistant alloy, at least a surface of the mounting bracket made of the corrosion-resistant alloy that forms a sealing portion thereof. After forming a coating film made of a nickel alloy containing an active metal, a sealing formed between the stabilized zirconia member and a mounting bracket made of a corrosion-resistant alloy having the coating film formed thereon. A method for sealing a cell portion of an oxygen sensor, comprising filling a sealing material made of aluminosilicate glass into a portion and heating the sealing material to a temperature equal to or higher than the softening point of the sealing material. 2. The coating film made of a nickel alloy containing an active metal contains at least one of the active metals in a total amount of 0.5 to 30% by weight. A method for sealing a cell part of the oxygen sensor according to the above. 3. The coating film made of a nickel alloy containing an active metal contains at least one of the active metals in a total amount of 0.5 to 30% by weight and phosphorus (P) in a weight of 20% by weight. The method for sealing a cell part of an oxygen sensor according to claim 1, wherein: 4. The means for forming the coating film includes a nickel alloy powder containing an active metal or at least an active metal and nickel on at least a surface of a mounting bracket made of a corrosion resistant alloy on which a sealing portion is formed. Apply the mixed powder to
The method according to claim 1, wherein the heat treatment is performed in a non-oxidizing atmosphere at a temperature equal to or higher than the melting point of the alloy powder or the mixed powder. 5. The method according to claim 1, wherein the aluminosilicate glass is silica 4
0-75% by weight, alumina 3-35% by weight, and furthermore MgO, MnO, CaO, SrO, Pb
O, BaO, ZnO, Li ₂ O, Na ₂ O, K ₂ O, Rb ₂
The method for sealing a cell portion of an oxygen sensor according to claim 1, wherein at least one of O is contained in a total of 5 to 30% by weight. 6. The aluminosilicate glass comprises silica 4
0-75% by weight, alumina 3-35% by weight, and furthermore MgO, MnO, CaO, SrO, Pb
O, BaO, ZnO, Li ₂ O, Na ₂ O, K ₂ O, Rb ₂
In total at least one of O, containing 5 to 30 wt%, further claims a total of at least one of _{B 2 O 3, P 2 O} 5, characterized in that it contains 15 wt% or less Item 1
3. The method for sealing a cell part of an oxygen sensor according to item 1.