JP2012013629A - Temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensor that has a longer lifetime at high temperature by using a material which has superior oxidation resistance and a small coefficient of thermal expansion.SOLUTION: The temperature sensor is characterized in that at least one or more regions of an element cover, a sheath pin and a signal line are made of Fe-based alloy containing Al. The Fe-based alloy containing the Al contains, by mass%, ≤0.03% C; ≤3% (preferably, ≤0.8%) Si; ≤1.0% Mn; ≤0.04% P; ≤0.01% S; ≤0.5% Ni; 11-21% (preferably, 15-20%) Cr; ≤6% (preferably 1.5 to <3.5%) Al; 0.01-0.5% Cu; 0.01-0.5% Mo; ≤0.03% N; ≤0.1% Nb; 0.005-0.50% Ti; 0.001-0.1% Sn; ≤0.00005% H, ≤0.002% O; and ≤0.01% Pb; and one kind or two or more kinds among 0.01-0.50% V, 0.001-0.1 mass% Y, 0.001-0.1 mass% REM (rare earth element), and 0.001-0.01 mass% Ca as occasion demands, the remainder being Fe and inevitable impurities.

Description

  The present invention relates to a temperature sensor used in a high-temperature exhaust gas atmosphere of 500 ° C. or higher discharged from a gasoline or diesel engine of an automobile.

There is a temperature sensor using a thermistor element as a sensor for measuring the temperature of exhaust gas discharged from an automobile gasoline or diesel engine. Conventionally, such a temperature sensor is generally provided with an element cover on the tip side so as to cover a thermistor element provided with a pair of Pt wires.
An example is shown in FIG. 1, and this sensor has Al ₂ O ₃ as a main component between a thermistor element 1 for detecting temperature and an element cover 2 disposed at the tip so as to cover the approximate element. The temperature sensor has a sheath pin 5 for fixing the cover by fitting the element cover with the signal line 4 that is filled with the filler 3 and further connected to the thermistor element through the Pt line 6.

  In the temperature sensor having such a structure, the material of the element cover, sheath pin, and signal line is generally made of, for example, high chromium / high nickel heat resistant stainless steel such as SUS310S (Patent Document 1) or Ni-base superalloy. (Patent Document 2).

JP 2004-286491 A JP 2010-71735 A

  However, under a high temperature environment, the SUS310S element cover as shown in Patent Document 1 is oxidized on the inner surface of the cover, and a thick oxide film is formed. Therefore, there are problems that the thickness of the cover is reduced and tearing occurs, and that the cover is deformed and damaged. Further, in the case of the Ni-based alloy shown in Patent Document 2, the above-mentioned problem is slightly improved, but still remains, and in addition, the problem that the material cost is expensive remains.

  In addition, the cause of deformation is not only due to oxidation, but also due to the difference in thermal expansion from alumina filled and fixed in the element cover, which causes damage to the element and breaks the Pt line. There are things to do.

  To solve these problems, the present invention provides a temperature sensor that has a higher heat resistance than conventional materials, has a thermal expansion coefficient closer to that of alumina, and uses a low-cost material to extend the life and reduce costs. To do.

In order to solve the above-described problems, the present invention provides a metal material used for a temperature sensor as follows.
According to the first aspect of the present invention, a filler containing Al ₂ O ₃ as a main component is filled between a thermistor element for detecting temperature and an element cover disposed at the tip so as to cover the approximate element, A temperature sensor having a sheath pin for fixing a cover by fitting a signal line connected to a thermistor element through a Pt line 6 and the element cover, wherein at least one of the element cover, sheath pin, and signal line is at least one part A temperature sensor comprising an Fe-based alloy containing Al.
According to the second aspect of the present invention, the Fe-based alloy containing Al is C: 0.03% or less, Si: 3% or less, Mn: 1.0% or less, P: 0.04% or less in mass%. , S: 0.01% or less, Ni: 0.5% or less, Cr: 11-21%, Al: 6% or less, Cu: 0.01-0.5%, Mo: 0.01-0.5 %, N: 0.03% or less, Nb: 0.1% or less, Ti: 0.005 to 0.50%, Sn: 0.001 to 0.1%, H: 0.00005% or less, O: The temperature sensor according to claim 1, wherein 0.002% or less, Pb: 0.01% or less, and the balance is made of Fe and inevitable impurities.
In the invention according to claim 3, the Fe-based alloy containing Al is Cr: 15-20%, Si: 0.8% or less, Al: less than 1.5-3.5% by mass. It is a temperature sensor of Claim 1 or 2 characterized by these.
In the invention according to claim 4, the Fe-based alloy containing Al is V: 0.01 to 0.50%, Y: 0.001 to 0.1% by mass, REM (rare earth element): 0.001. The temperature sensor according to any one of claims 1 to 3, comprising one or more of ~ 0.1 mass%, Ca: 0.001 to 0.01 mass%.
The invention according to claim 5 is the temperature sensor according to claims 1 to 4, which is a sensor used in a high-temperature exhaust gas atmosphere of 500 ° C. or higher discharged from a gasoline or diesel engine.

  The element cover, sheath pin, and / or signal line in the temperature sensor are made of a material having a specific composition called an Fe-based alloy containing Al, thereby providing two properties, oxidation resistance and good thermal expansion characteristics. Have both. Therefore, the heat resistance of the temperature sensor can be improved under a high temperature environment (temperature range of 500 ° C. or higher), and the lifetime can be increased.

  Since the element cover, sheath pin, and / or signal line have a small difference in linear expansion between the alumina filled and fixed inside the sensor and the Fe base alloy used, deformation of the cover in a high temperature environment, Filler, element damage, and disconnection of the electrode wire can be suppressed.

  The Fe-based alloy contains Al. This Al forms an alumina film on the alloy surface in a high temperature environment, and remarkably suppresses oxidation of the alloy. Therefore, not only the life of the material is remarkably improved, but also the durability of the temperature sensor is remarkably improved in order to suppress the adhesion between the cover and the filler and the formation of a gap.

  That is, by having both the oxidation resistance and the low thermal expansion property, it is possible to greatly reduce the thermal load on the filler, element, etc. in a high temperature environment and to greatly improve the life of the temperature sensor.

  In addition, the Fe-based alloy containing Al not only has oxidation resistance and low thermal expansion at high temperatures, but also has other characteristics similar to those of conventional high chromium / high nickel heat resistant stainless steels and Ni based alloys. The level can be secured, and the cost is rather cheaper than these materials. Accordingly, the manufacturing cost of the temperature sensor is reduced.

  As described above, according to the present invention, it is possible to provide a temperature sensor that has a long life and is inexpensive.

It is a figure which shows the structure of the sensor based on this invention.

As described above, the temperature sensor of the present invention is formed by filling a filler mainly composed of alumina between an element for detecting temperature and an element cover disposed so as to cover the element, and the element cover. , Sheath pin, and / or signal line are made of an Fe-based alloy containing Al.
The Fe-based alloy containing Al includes Cr: 11 to 21% (preferably 15 to 20%) and Al: 6% or less (preferably less than 1.5 to 3.5%). In this case, the effects of the above-described oxidation resistance and thermal expansion characteristics can be exhibited particularly well. Moreover, when content of the said component remove | deviates from the said range, there exists a possibility that it may become difficult to obtain the said characteristic as follows.

The reasons for limiting each element are described below.
H: 0.00005% by mass or less, and O: 0.002% by mass or less H and O reduce the secondary workability of steel. Therefore, when the content exceeds the above value, the element cover, sheath pin, and / Or processing into signal lines becomes difficult. Therefore, it limits to 0.00005 mass% or less and 0.002 mass% or less, respectively.

C: 0.03 mass% or less When the C content is high, abnormal oxidation tends to occur. Moreover, when C content becomes high, the toughness of a slab and a hot coil will deteriorate, and manufacturability will deteriorate. Therefore, the upper limit of the C content is limited to 0.03% by mass or less.

Si: 3% by mass or less Since Si is an element that deteriorates the toughness and secondary workability of steel, the Si content is 3% by mass or less. Preferably it is less than 0.8 mass%, More preferably, it is 0.5 mass% or less.

Mn: 0.5% by mass or less Mn generates a Mn-based oxide to inhibit the formation of a dense Al oxide layer and adversely affects high-temperature oxidation resistance. Therefore, in order to maintain high temperature oxidation resistance, the Mn content is limited to 0.5% or less.

P: 0.04% by mass or less P has an adverse effect on high-temperature oxidation resistance and toughness of hot-rolled sheet, so its content is limited to 0.04% by mass or less.

S: 0.005 mass% or less S is a component inevitably contained in steel, and remarkably inhibits the formation of an Al ₂ O ₃ film. Therefore, the S content is limited to 0.005% or less.

Ni: 0.5 mass% or less Ni is a component inevitably contained in steel. The addition of a small amount of Ni is effective for improving toughness, but has an adverse effect on oxidation resistance, so is 0.5 mass% or less. Preferably it is 0.3 mass% or less, More preferably, it is 0.25 mass% or less.

Cr: 11-25% by mass
Cr is a basic and effective element as an element for improving high-temperature oxidation resistance. In order to obtain good high-temperature oxidation resistance, addition of 11% or more is necessary. However, excessive addition degrades the toughness of slabs and hot coils. Therefore, the Cr content is limited to 11 to 21% by mass. Preferably it is 15-20%, More preferably, it is 17-19.5 mass%.

N: 0.03 mass% or less N combines with Al in steel to form AlN, and becomes a starting point for abnormal oxidation. Therefore, the N content is limited to 0.03% by mass or less in order to improve high temperature oxidation resistance.

Al: 1.5-6 mass%
Al, like Cr, is the most important element for obtaining high-temperature oxidation resistance. However, when Al is contained excessively, the toughness of the slab and hot coil deteriorates, so when added, the upper limit is limited to 6% by mass or less. Excellent high temperature oxidation resistance is obtained by a dense Al oxide formed on the surface of the steel, and the Al content necessary to form this layer is 1.5% by mass or more. Moreover, even if Al is less than 3.5% by mass, almost sufficient high-temperature oxidation resistance can be obtained. Furthermore, when thickness reduction or oxidation resistance is requested | required, Preferably it is less than 2.5-3.5 mass%, More preferably, it is more than 3.0-3.5 mass%.

Cu: 0.01-0.5 mass%, Mo: 0.01-0.5 mass%:
All of these improve the toughness of the steel. In order to fully exhibit the effect, addition of 0.01% by mass or more is required. On the other hand, excessive addition reduces the toughness of the steel and leads to hardening of the steel and an increase in production costs. Therefore, the upper limit is 0.5%. Preferably it is 0.01-0.2 mass%.

Nb: 0.1% by mass or less Nb is desirably reduced as much as possible because it impairs the toughness and secondary workability of the steel, and it is necessary to reduce it to at least 0.1% or less. Preferably it is 0.02 mass% or less, More preferably, it is less than 0.01 mass%.

Ti: 0.005 to 0.50 mass%, V: 0.01 to 0.5 mass%
Ti and V have the effect of improving the high temperature strength of the steel by precipitation strengthening and improving the weldability and toughness. In this patent, the respective claims are defined as Ti: 0.005 to 0.50 mass%, and V: 0.01 to 0.5 mass%. V is added as necessary.

Sn: 0.001 to 0.1% by mass
It is an element that improves the acid resistance and acid dew point corrosion resistance of steel. In a combustion environment containing water vapor and oxygen, acidic condensed water may be condensed at the time when the operation is stopped or at a location where the temperature is locally lowered due to S contained in fuel or the like during combustion and moisture generated during combustion. By containing Sn in an amount of 0.001% by mass or more, acid dew point corrosion is improved. Sn also has the effect of improving free-cutting properties and workability. However, the addition of 0.1% by mass or more significantly lowers the secondary workability and hot workability of the steel, so the upper limit was made 0.1% by mass. Preferably it is 0.001-0.05 mass%.

Pb: 0.01% by mass or less Pb is an element that lowers the toughness of stainless steel. If the content exceeds 0.01%, the effect appears remarkably, so the content is limited to 0.01% or less. Preferably it is 0.005% or less.

Y: 0.001 to 0.1% by mass,
REM (rare earth element): 0.001 to 0.1% by mass,
Ca: 0.001 to 0.01% by mass
Any of these is an alloy component that is added as necessary, and exhibits an action of solid-dissolving in the oxide film and strengthening the oxide film. Such an effect becomes remarkable at Y: 0.001 mass% or more, REM: 0.001 mass% or more, Ca: 0.001 mass% or more, and Zr: 0.03 mass%. However, adding an excess amount of Y exceeding 0.1% by mass, an excess amount of REM exceeding 0.1% by mass, and an excess amount of Ca exceeding 0.01% by mass only makes the steel material excessively hardened. In addition, surface flaws are likely to occur during manufacturing, leading to an increase in manufacturing cost.

  Moreover, it is preferable that the said temperature sensor is used in a 500 degreeC or more use environment, and can be used suitably over a long period also in a 950 degreeC or more use environment.

Example 1
In this example, basic characteristics required for the temperature sensor are confirmed. Table 1 shows the chemical component values of the test materials. The steel shown in Table 1 was melted in vacuum and subjected to hot rolling, and then annealing and cold rolling were repeated to produce a plate material having a plate thickness of 1 mm or 0.3 mm. The final annealing was held in the atmosphere at 950 ° C. for 3 minutes, and then cooled to 300 ° C. at a rate of 30 ° C./s or more. In the intermittent oxidation test, a test piece having a size of 0.3 mm × 15 × 35 mm is prepared and dry-polished with emery paper at the final count # 400, then heated in a furnace at 1050 ° C. for 5 minutes and cooled at room temperature for 5 minutes. After carrying out 3000 cycles of the intermittent oxidation test in the atmosphere, the weight of the test piece was measured. Evaluation measurement results compared with the weight before the test, what weight change ○ those 2 mg / cm ² or less at -2mg / cm ² or more, there is weight gain or weight loss greater than 2 mg / cm ² It evaluated as x. The linear expansion coefficient was measured by preparing a 1 mm × 4 mm × 20 mm strip test piece by cutting, and then obtaining an average linear expansion coefficient between 0 ° C. and 1000 ° C. at 0 ° C. starting point according to JISZ2285. The average linear expansion coefficient was evaluated as “◯” when the average linear expansion coefficient was 1.5 × 10 ⁻⁵ / ° C. or less, and “×” when the average linear expansion coefficient was exceeded. The results are shown in Table 2.

As shown in Table 2, steels (Nos. 1 to 10) included in the scope of the present invention were excellent in oxidation resistance and had a small coefficient of linear expansion. On the other hand, all of SUS304, SUS310S (No. 12), and NCF601 (No. 13) have insufficient oxidation resistance and did not show a good value for the linear expansion coefficient. The average coefficient of linear expansion between 0 and 1000 ° C. of the alumina is about 0.8 to 0.9 × 10 ⁻⁵ / ° C.).

(Example 2)
A temperature sensor having a shape as shown in FIG. 1 was produced. The element cover (plate thickness 0.5 mm), sheath pin (diameter 2.3 mm, tube thickness 0.3 mm), and signal line (average diameter 0.35 mm) are all No. 1 in Table 1. 3 steel was produced as a raw material. At that time, a filler mainly composed of alumina is filled between the element and the element cover, and a filler mainly composed of magnesia is filled between the sheath pin and the signal line. The outer periphery was welded all around.
In addition, the material of each part mentioned above is an example, Comprising: This invention is not limited to this.

  Using the temperature sensor thus produced, an intermittent oxidation test of 3000 cycles was performed under the conditions of Example 1. When the temperature in the electric furnace soaking zone set at 1050 ° C. was measured using this sensor after the test was completed, it showed a value in the range of 1049-1052 ° C., and no performance degradation was observed. Further, the diameters of the element cover and the sheath pin after the test were compared with those before the test, and the difference between the values before and after the test was good within 2%.

  The temperature sensor according to the present invention is excellent in heat resistance and durability, and is particularly suitable for measuring the exhaust gas temperature of automobile gasoline or diesel engines.

1 Thermistor element 2 Element cover 3 Filler 4 Signal line 5 Seaspin 6 Pt line

Claims (5)

A filler mainly composed of Al ₂ O ₃ was filled between the thermistor element for detecting the temperature and the element cover disposed at the tip so as to cover the approximate element, and further connected to the thermistor element through the Pt line. A temperature sensor having a sheath pin for fixing a cover by fitting a signal line and an element cover, wherein at least one of the element cover, sheath pin, and signal line is made of an Fe-based alloy containing Al. A temperature sensor characterized by that.   Fe-based alloy containing Al is, in mass%, C: 0.03% or less, Si: 3% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Ni: 0.5% or less, Cr: 11-21%, Al: 6% or less, Cu: 0.01-0.5%, Mo: 0.01-0.5%, N: 0.03% or less , Nb: 0.1% or less, Ti: 0.005 to 0.50%, Sn: 0.001 to 0.1%, H: 0.00005% or less, O: 0.002% or less, Pb: 0 The temperature sensor according to claim 1, wherein the temperature sensor is 0.01% or less, and the balance is Fe and inevitable impurities.   The Fe-based alloy containing Al is Cr: 15 to 20%, Si: 0.8% or less, and Al: 1.5 to less than 3.5% by mass%, or 2. The temperature sensor according to 2.   Fe-based alloy containing Al is V: 0.01 to 0.50%, Y: 0.001 to 0.1% by mass, REM (rare earth element): 0.001 to 0.1% by mass, Ca: The temperature sensor according to claim 1, wherein 0.001 to 0.01% by mass is contained in one kind or two or more kinds.   The temperature sensor according to claim 1, wherein the temperature sensor is used in an exhaust gas atmosphere having a high temperature of 500 ° C. or higher discharged from a gasoline or diesel engine.

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