JPH09318619A - Probe for measuring hydrogen concentration in molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen concentration measuring probe with facilitates measuring without any limits in the insertion angle or depth of a two hole ceramic pipe and measuring is not made impossible even if inert gas is reversibly circulated. SOLUTION: In a circulation type hydrogen concentration measuring probe having a two hole ceramic pipe, a fitting part 22 is formed by boring the tip part of a two hole ceramic pipe 11 made of silicon nitride and a ceramic filter 22a and a ceramic fiber 22b are fitted. Then, by the characteristic of the ceramic fiber 22b for being prevented from being wet in hot metal solution 12, the flowing of the metal solution 12 into the suction passage 17 of the two hole ceramic pipe 11 is prevented, the flowing of circulated inert gas into the solution 12 is also prevented and thus the degree of freedom of setting the insertion angle of the two hole ceramic pipe 11 is increased and its insertion depth is small.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to aluminum,
A probe for measuring the hydrogen concentration in molten metal such as aluminum alloys, in particular, the application range is expanded and the service life is extended except for the influence of the insertion depth, the clogging of the molten metal at the suction port, and the influence of the insertion angle. It's about the bad probe.

[0002]

2. Description of the Related Art Aluminum and aluminum alloys are
When hydrogen gas is dissolved or present in the molten metal, the hydrogen gas causes pores inside the metal during solidification of the molten metal, which deteriorates the quality of the obtained cast metal. Therefore, for such metals as aluminum and aluminum alloy, an operation of removing dissolved hydrogen in the molten metal (so-called dehydrogenation operation) is generally performed. However, this dehydrogenation operation takes time, and excessive dehydrogenation operation increases the cost of the product.Therefore, in general, prior to the operation, the hydrogen concentration in the molten metal should be measured in advance. Based on the results, the minimum necessary dehydrogenation operation is performed. The hydrogen concentration in the molten metal, which is performed prior to the dehydrogenation operation, can be measured directly in the molten metal state as it is in the molten state, and the time required for the measurement is short. As described in Japanese Patent No. 684865 and US Patent No. 2861450,
Measuring the hydrogen concentration in the molten metal by the so-called Telegas method by repeatedly circulating a predetermined inert gas in the desired molten metal and measuring the concentration of hydrogen diffused in the inert gas. Is said to be desirable.

By the way, in the hydrogen concentration measuring apparatus for measuring the hydrogen concentration in the molten metal by the telegas method, an inert gas is blown into the molten metal and the inert gas blown into the molten metal is recovered. In general,
A probe having a ceramic tube provided with two through holes in the axial direction as a gas passage, that is, a so-called two-hole ceramic tube is adopted. By immersing the tip of the two-hole ceramic tube in the molten metal, a circulating closed circuit of the inert gas containing the molten metal is formed. During the process of being repeatedly circulated, the hydrogen gas in the molten metal is diffused in the inert gas. Then, the concentration of hydrogen in the inert gas is detected by the circulation detector provided on the closed circuit, whereby the concentration of hydrogen in the molten metal is measured.

In such a probe, conventionally, the tip surface of the two-hole ceramics tube, which is immersed in the molten metal, is a surface perpendicular to the axis of the two-holes ceramic tube, which is not contained in the molten metal. A hole for blowing the active gas is opened on the tip surface, and the inert gas is blown into the molten metal through the hole closed on the tip surface,
Hydrogen concentration is being measured. A conventional probe (Japanese Utility Model Laid-Open No. 5-75661) is shown in FIG. In FIG. 6, the two-hole ceramic tube 11 is inserted into the molten metal 12. When the circulation pump (not shown) is discharged, the circulating inert gas is supplied through the stainless pipe 13 and the inert gas discharge passage 14, and the two-hole ceramic pipe tip 11
It comes out of a, passes through the molten metal, and is collected in the cup 15.

Then, when the circulation pump changes to suction,
The gas in the cup 15 is returned to the circulation pump through the filter 16 and then the suction side flow path 17 and the stainless steel pipe 18. During the repetition of this operation, hydrogen in the molten metal 12 is diffused and equilibrated with the inert gas for circulation. In FIG. 6, the stainless steel pipes 13 and 18 and the two-hole ceramic pipe 12
The connection portion with and is accommodated in the protective sleep 20, and the connection is made by firmly adhering to the glass 19 for fusing so as to prevent gas leakage.

The two-hole ceramic tube 11 is provided with a surface coating layer 21. When the two-hole ceramic tube 11 is inserted into the molten metal 12, it is prevented from cracking due to thermal shock, or the wettability with the molten metal 12 is improved, so This is to prevent air from entering through the gap with the ceramic tube 11.

[0007]

In the probe according to the above-mentioned prior art, as shown in FIG.
The inert gas discharge passage 14 of No. 1 is opened in the molten metal. Therefore, when the stainless steel tube 18 for connecting the two-hole ceramics tube 11 is erroneously connected to the suction side of the pump for measurement, the molten metal 12 enters the flow path 14 of the two-holes ceramic tube 11. Then it solidified, and it became impossible to measure. Further, the conventional two-hole ceramic tube 11 shown in FIG. 6 has a problem that the angle of insertion into the molten metal 12 is limited. That is, in the two-hole ceramics pipe 11 of FIG. 6, when the two-holes ceramics pipe 11 is obliquely inserted, the inert gas for circulation discharged from the tip 11a of the two-holes ceramics pipe is not collected in the cup 15, so that the inertness is inactive. The gas cannot be circulated and the measurement cannot be performed. Furthermore, the probe of FIG. 6 needs to be inserted into the molten metal 12 at a depth of 50 mm or more in order to prevent air from entering, and measurement at a shallow position where the depth of the molten metal is 50 mm or less cannot be performed.

The present invention has been made in view of the above-mentioned problems, and the object thereof is to prevent visual confirmation by eliminating the restriction on the insertion angle and the insertion depth of the two-hole ceramic tube and facilitating the measurement. It is an object of the present invention to provide a probe for measuring hydrogen concentration which enables measurement even in such a place and does not make measurement impossible even when an inert gas is reversely circulated.

[0009]

In order to solve the above-mentioned problems, in the hydrogen concentration measuring probe according to the present invention, the inside of the two-hole ceramic tube is hollowed out or the outer cylinder is formed into two. The present invention is characterized in that a filling portion is provided by joining it to a perforated ceramics tube, and a ceramic filter and ceramic fibers are sequentially filled in the filling portion.

More specifically, in the probe for measuring hydrogen concentration according to the first invention of the present application, a predetermined inert gas is repeatedly circulated in the molten metal so that the concentration of hydrogen diffused in the inert gas is increased. Is used as a gas passage in the axial direction, which is used in an apparatus for measuring hydrogen concentration in molten metal for measuring hydrogen concentration in such molten metal.
Having two through-holes, the tip of which is immersed in the molten metal, and the inert gas blown into the molten metal through one of the two through-holes, while the inert gas blown into the molten metal. In a probe for hydrogen concentration measurement, which is provided with a two-hole ceramic tube and is configured to be recovered through another through hole, a filling portion is provided at the tip of the two-hole ceramic tube, and a heat resistant filter is provided in the filling portion. Another feature is that heat-resistant fibers having low wettability are sequentially filled into the molten metal.

In the probe for measuring hydrogen concentration according to the second invention of the present application, in the probe for measuring hydrogen concentration according to the first invention, the heat-resistant filter and the heat-resistant fiber sequentially filled in the filling portion are: It is characterized by being a ceramic filter and a ceramic fiber.

In the hydrogen concentration measuring probe according to the third invention of the present application, in the hydrogen concentration measuring probe according to the second invention, the ceramic fibers are silicon carbide fibers, silicon nitride fibers or alumina fibers. It is characterized by

In the probe for measuring hydrogen concentration according to the fourth invention of the present application, in the probe for measuring hydrogen concentration according to any one of the first to third inventions, the filling portion is directed toward the end thereof. It is characterized in that it has a divergent shape.

[0014]

1 to 4 show an embodiment of a probe for measuring hydrogen concentration according to the present invention. The same components as those of the conventional technique (FIG. 6) are designated by the same reference numerals, and the description thereof will be omitted.

[First Embodiment] FIG. 1 is a longitudinal sectional view of a probe for measuring hydrogen concentration according to the present invention. As shown in FIG. 1, in the hydrogen concentration measuring probe according to the present invention, the filling portion 22 is formed by hollowing out the tip portion of the two-hole ceramic tube 11 made of silicon nitride, and the ceramic filter 122a.
And ceramic fibers 22b. Molten metal 1
The insertion of the two-hole ceramics tube 11 into 2 is carried out while blowing the inert gas for circulation from both the circulation flow paths 13 and 18. When the supply of the inert gas is stopped after inserting the two-hole ceramics tube 11 into the molten metal, the inert gas for circulation is supplied to the entire circulation circuit including the ceramic fiber 22b at the tip of the two-holes ceramic tube 11 and the ceramic filter 122a. Trapped in. Hydrogen dissolved in the molten metal 12 diffuses from the interface between the ceramic fiber 22b and the molten metal 12 into the inert gas in the ceramic fiber 22b. When a circulation pump (not shown) is activated, the inert gas is mixed with the ceramic filter 22a and the ceramic fiber 2
Circulate through 2b. The hydrogen gas diffused in the inert gas in the ceramic fiber 22b moves into the circulating inert gas. Hydrogen diffuses from the molten metal 12 into the inert gas until the hydrogen partial pressure in the inert gas in the ceramic fiber 22b becomes equal to the equilibrium hydrogen partial pressure in the molten metal 12.

Here, the ceramic fiber 22b needs to have a property of not getting wet with the molten metal 12. This property prevents the molten metal 12 from entering the suction passage 17 of the two-hole ceramic tube 11. Further, since the inert gas for circulation does not enter the molten metal 12, the degree of freedom of the insertion angle of the two-hole ceramic tube 11 into the molten metal 12 is increased. Further, according to such a configuration, the tip portion of the two-hole ceramic tube is
It is sufficient if it can be immersed in the molten metal 12 for 10 to 15 mm or more, and the hydrogen concentration can be measured even when it is difficult to visually check the measurement position or when the molten metal 12 is inserted into the molten metal 12 in the furnace. As a result, the probe for measuring hydrogen concentration according to the present invention has a wider application range than the conventional probe.

[Second Embodiment] As a method other than the method of forming the filling portion 22 at the tip portion of the two-hole ceramic tube 11 and hollowing out the portion to form the filling portion 22,
There is a method of joining the outer cylinder to the tip portion of the two-hole ceramic tube. 2 and 3 are enlarged cross-sectional views of a main part of the hydrogen concentration measuring probe in which the filling portion 22 is formed by such a method. These probes have the outer cylinder 23 at the tip portion of the two-hole ceramic tube 11. It is made by fitting and fixing it with the ceramic adhesive 24.

[Third Embodiment] Here, in the probe of FIG. 3, the filling portion 22 is formed in a divergent shape toward the end thereof. Since the filling portion 22 having such a skirt shape is provided, the diameter of the filling portion 22 to be filled increases as it goes to the end thereof. Therefore, in the case of this probe, the area in which the ceramic fiber 22b contacts the molten metal 12 becomes larger than that in FIG.
It is possible to improve the diffusion efficiency of hydrogen from the inside.

[Fourth Embodiment] The hydrogen concentration measuring probe shown in FIG. 4 is an improved example of the hydrogen concentration measuring probe shown in FIG. 1, and is conventionally measured by lengthening the ceramic portion of the two-hole ceramic tube. In the high temperature furnace, which was difficult
For example, it is possible to measure the hydrogen concentration in the molten metal in the holding furnace. In FIG. 4, elements corresponding to those in other forms are designated by the same reference numerals. Here, a protective casing 25 is attached in correspondence with the lengthening of the ceramic portion of the two-hole ceramic pipe 11, and cooling air is sent from the upper portion thereof via a cooling pipe 27.

According to such a hydrogen concentration measuring probe, the consumable ceramic fiber to be filled in the tip of the two-hole ceramic tube can be easily replaced, so that the life of the two-hole ceramic tube body is dramatically improved. .

[Concrete mode] The thickness and length of the two-hole ceramic tube 11 can be freely set according to the purpose of use. Further, as the material thereof, silicon nitride, alumina or the like is used, but silicon nitride is more preferable from the viewpoint of thermal shock resistance.

The filling portion 22 has an inner diameter of 6 to 20 m.
It is suitable that the m and space volume are in the range of 0.2 to 3 ml. Here, as described above, the ceramic fiber 22b needs to have a property of not getting wet with the molten metal 12. As such, the ceramic fibers 22b include silicon carbide fibers,
Silicon nitride fiber and alumina fiber are suitable. However, any material that does not wet the molten metal 12 or that does not easily wet can be used.

The ceramic fiber is used by filling a thin material with an appropriate packing density as much as possible in terms of strength. It is preferable that the ceramic fiber diameter is 2 to 10 μm, the length is 20 to 60 mm, and the packing density is 0.2 to 0.5 g / cm ³ , and the packing is light. The ceramic filter is Al ₂ O ₃ = 92-9
Alumina fibers having a composition of 9% and SiO ₂ = 1 to 8% are preferable.

[0024]

[Embodiment] Using the two-hole ceramic tube of FIG. 1 made of silicon nitride and having a diameter of 8 mm and the conventional two-hole ceramic tube of FIG. 6, the influence of the dipping angle when measuring the hydrogen concentration in the molten metal (Table 1), the effect of immersion depth (Table 2), and the results of comparison of measurement accuracy (Table 3) are shown. Further, FIG. 5 shows the comparison result of the response times.

[0025]

[Table 1] << Table Note >> ○: Measurement is possible △: Measurement is difficult ×: Measurement is not possible

[0026]

[Table 2] << Table Note >> ○: Possible △: Difficult ×: Not possible

[0027]

[Table 3]

As can be seen from Tables 1 to 3 and FIG.
A two-hole ceramic tube has been obtained which is equivalent to the conventional one in terms of response time and measurement accuracy, and which is superior to the conventional one in terms of the influence of the immersion angle and the immersion depth.

[0029]

As described above, in the hydrogen concentration measuring probe according to the present invention, since the ceramic filter and the ceramic fiber are sequentially filled in the filling portion provided at the tip of the two-hole ceramic tube, It becomes possible to prevent the situation where the molten metal intrudes into the two-hole ceramic pipe from the blow-out hole during the circulation of the active gas and the measurement becomes impossible. Further, there is no limitation on the insertion angle or the insertion depth of the two-hole ceramics tube, which facilitates the measurement. By facilitating the measurement, the measurement can be performed even in a place where it cannot be visually confirmed, and the specifications as a probe are improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a configuration of a hydrogen concentration measurement probe according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing a configuration of a probe for measuring hydrogen concentration according to a mode different from that of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part showing a configuration of a probe for measuring hydrogen concentration according to a mode different from that of FIG.

FIG. 4 is a vertical cross-sectional view showing a configuration of a probe for measuring hydrogen concentration according to an improved example of FIG.

FIG. 5 is a graph showing a comparison result of response times of a probe for measuring hydrogen concentration according to the present invention (FIG. 1) and a probe for measuring hydrogen concentration according to the related art (FIG. 6).

FIG. 6 is a vertical cross-sectional view showing the configuration of a hydrogen concentration measurement probe according to a conventional example.

[Explanation of symbols]

 11 2 hole ceramics tube 11a 2 hole ceramics tube tip 12 Metal melt 13 Stainless steel tube 14 Inert gas discharge channel 15 Cup 16 Filter 17 Suction side channel 18 Stainless tube 19 Glass for fusion 20 Protective sleep 21 Surface coating layer 22 Filling part 22a Ceramic filter 22b Ceramic fiber 23 Outer cylinder 24 Ceramic adhesive 25 Protective casing 27 Cooling pipe

Claims (2)

[Claims] 1. A method for measuring the hydrogen concentration in a metal melt by repeatedly circulating a predetermined inert gas in the metal melt and detecting the concentration of hydrogen diffused in the inert gas. It has two through holes as a gas passage in the axial direction, which is used in a hydrogen concentration measuring device, and a tip portion is dipped in the metal melt, and the metal melt is introduced into the metal melt through one of the two through holes. A hydrogen concentration measuring probe comprising a two-hole ceramic tube, wherein an inert gas is blown into the molten metal while the inert gas blown into the molten metal is recovered through another through hole. Hydrogen concentration measurement characterized in that a filling part is provided at the tip, and a heat-resistant filter and heat-resistant fiber having low wettability to molten metal are sequentially filled in the filling part. Probe. 2. The hydrogen concentration measuring probe according to claim 1, wherein the heat resistant filter and the heat resistant fiber sequentially filled in the filling portion are a ceramic filter and a ceramic fiber.