JP2535341B2 - Sampling device and method for collecting gas analysis samples in molten steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method and an instrument for collecting a sample for analyzing gases such as hydrogen, oxygen and nitrogen in molten steel, contributing to improvement of steelmaking technology and quality assurance. It is possible.

(Prior Art) In order to quantitatively analyze gas in molten steel, a mold 10 having a two-part structure as shown in FIG.
A method is known in which molten steel pumped up with a spoon is cast into the concave portion 11 of 10 and cooled and solidified, and a sample for gas analysis is cut out from the solidified body to quantify the gas.

By the way, among the gases in the steel, hydrogen, for example, is 1600 ℃
Has an equilibrium solubility of 25 ppm in pure iron, and the equilibrium solubility greatly decreases with decreasing temperature. Therefore,
The molten steel sampled in the mold 10 as described above diffuses from the low temperature side to the high temperature side in the molten steel while cooling and solidifying in the mold 10, and shrinkage holes (shrink cavities) are generated over the entire center line. However, hydrogen becomes a molecule (gas) by the reaction of H ⁺ + H ⁺ → H ₂ and escapes from the contraction hole into the atmosphere. Therefore, in the above method, an accurate analysis value cannot be obtained especially for hydrogen.

On the other hand, FIG. 5 shows an immersion type molten steel sampling tube 12 made of a quartz tube. The sampling tube 12 is formed by attaching a melting point material having a temperature lower than the molten steel temperature to the molten steel inflow port 13 so as to be hermetically sealed and evacuating the inside. By dipping the sampling pipe 12 in the molten steel from above, the low-temperature melting point material is melted, and the molten steel is sucked into the sampling pipe 12 through the molten steel inflow port 13. Thereafter, the sampling pipe 12 is pulled up, the molten steel inside is cooled and solidified, and a gas analysis sample is cut out from the solidified body in the same manner as above to quantify the gas.

In this case, the thickness of the quartz tube that constitutes the sampling tube 12 is 1-2 m.
It is as thin as about m. Therefore, it is possible to rapidly cool and solidify the entire molten steel in the sampling pipe 12 by immersing it in a refrigerant after collecting the molten steel.

However, even in the method described above, when the molten steel is sampled in the sampling tube 12, the diffusion of hydrogen in the molten steel is promoted due to the vacuum inside the sampling tube 12 and escape from the molten steel. When it is immersed in a refrigerant and rapidly cooled and solidified, shrinkage holes (shrink cavities) are formed over the entire center line, and hydrogen diffuses and escapes into these shrinkage holes. For this reason, even if a sample for gas analysis is prepared using such a sampling tube 12, a very accurate analysis value cannot be obtained.

Therefore, in order to obtain a more accurate analysis value, conventionally, the sixth
A molten steel sampling pipe as shown in the figure is used. This sampling pipe has a double pipe structure of an inner pipe 14 and an outer pipe 15 each made of an iron pipe, and the inner pipe 14 is evacuated in the same manner as described above. This is immersed in molten steel, the molten steel is sucked into the inner pipe 14 from the molten steel inflow port at the lower end portion in the same manner as described above, and is cooled and solidified.
In this case, the escape gas collected in the pipe can be quantitatively analyzed before the gas is quantitatively determined from the solidified body.

(Problems to be solved by the invention) However, in the molten steel collecting method using the above-mentioned double pipe structure collecting pipe, the structure of the collecting pipe configured to have a vacuum inside becomes complicated and expensive, Further, there is a problem that the analysis work becomes complicated because it is necessary to perform both gas analysis and diffusion gas analysis in the solid sample.

The present invention has been made in view of the above-mentioned conventional problems, the structure is simple and can be produced at a lower cost, the work labor is also reduced, and moreover, it is possible to obtain a more accurate analysis value in molten steel. The object of the present invention is to provide a sampling tool and a sampling method for the sample for gas analysis of.

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the sample collecting instrument for gas analysis in molten steel in the present invention, the molten steel flows into the inside through the molten steel inlet by being immersed in the molten steel. A molten steel collecting pipe is provided, and this molten steel collecting pipe is formed by providing a molten steel holding portion that extends downward from the molten steel inlet and has a closed bottom end, and a reduced diameter portion provided at an intermediate position in the vertical direction of the molten steel holding portion. It is characterized in that the lower side of the pin is formed to have a smaller diameter and a smaller wall thickness than the upper side.

The method for collecting a sample for gas analysis in molten steel according to the present invention has a molten steel holding portion having a closed bottom end extending downward from a molten steel inflow port, and the lower side of a reduced diameter portion at a midway position in the vertical direction of the molten steel holding portion is an upper side. A method for sampling a gas analysis sample using a molten steel sampling tube formed to have a smaller diameter than
The internal space communicating with the molten steel inflow port in the molten steel sampling pipe is sealed in the molten steel except for the molten steel inflow port so that the molten steel naturally flows in, and then is pulled up from the molten steel and rapidly cooled by a refrigerant, and the diameter reduction in the molten steel holding part It is characterized in that the solidified body below the portion is used as a sample for gas analysis.

(Operation) In the above-described collecting tool of the present invention, molten steel can be collected into a molten steel collecting pipe (hereinafter abbreviated as a collecting pipe) by natural inflow instead of vacuum suction when immersed in molten steel. That is, the molten steel flows into the inside by immersing the sampling pipe until the molten steel inlet is located below the liquid level of the molten steel, and then when the molten steel is pulled up from the molten steel, the molten steel that has flowed above the molten steel inlet Flows out through the molten steel inflow port, but the molten steel in the molten steel holding portion at the lower end closed below the molten steel inflow port is retained inside as it is.

The molten steel collected in the molten steel holding portion of the sampling pipe in this way solidifies from the pipe wall side toward the center during the subsequent cooling solidification operation. At this time, the pipe diameter of the lower side of the molten steel holding portion is smaller than that of the upper side, and therefore,
In the lower part, the solidification to the center ends earlier than in the upper part. Further, since the lower side of the molten steel holding portion has a smaller wall thickness than the upper side, and the amount of heat radiation through the pipe wall is larger than that of the upper side, the entire lower side completes solidification faster than the upper side. As a result, it is possible to cool and solidify the whole without generating shrinkage holes in the solidified portion on the lower side.

In this way, the cooling rate of the molten steel in the molten steel holding part is formed so that it becomes faster toward the lower side, so that even if the entire molten steel is rapidly cooled and solidified after being collected, a contraction hole is formed at the lower end side of the sampling pipe. It is possible to secure a solidified body that does not have

Therefore, if the above-mentioned sampling tube is used, the molten steel is sampled by natural inflow instead of vacuum suction, so that escape of gas that easily diffuses like hydrogen is suppressed, and further,
Even when the material is rapidly cooled and solidified, a solidified body having no shrinkage hole at the center can be surely obtained at the lower end side of the sampling tube, so that diffusion and escape of gas due to the occurrence of shrinkage hole can be suppressed. For this reason,
An accurate analysis value can be obtained by cutting out this portion as a sample for analysis and performing gas analysis.

As described above, the above sampling tube does not need to be evacuated in advance, and a shape having a small diameter and a thin wall on the lower end side can be relatively easily manufactured by using, for example, a quartz tube, Since it is not necessary to process the inside by vacuuming and sealing it, the manufacturing cost can be reduced, and moreover,
Since diffusion escape of gas in the molten steel is suppressed, more accurate analysis value can be obtained without performing a work such as separately collecting and analyzing the escape gas, and therefore the analysis work is also facilitated.

In the sampling method of the present invention, even if the diameter of the lower side of the reduced diameter portion in the molten steel holding portion is made smaller, the molten steel can be allowed to flow into this portion by natural inflow, and as a result, the solidification of the entire portion is further increased. It is possible to obtain a solidified body having no shrinkage pores more quickly.

That is, the molten steel that has flowed into the sampling pipe through the molten steel inflow port has a large surface tension, and it becomes difficult for the molten steel to flow into the small diameter portion below the reduced diameter portion due to the air remaining in this portion.

Therefore, in the method of the present invention, the internal space of the sampling pipe is hermetically sealed in the molten steel except for the molten steel inflow port. At this time, the internal air expands about 7 times in volume when immersed in molten steel at a temperature of 1600 ° C., for example, and the expanded portion is discharged to the outside of the sampling pipe through the molten steel inflow port during the immersion process. Therefore, the internal air is in a lean state with a density of 1/7. This state is maintained inside the molten steel except for the molten steel inflow port, so that it is maintained during the inflow of molten steel, so that the molten steel that has flowed into the sampling pipe further flows into the small diameter portion below the reduced diameter portion. When this is done, a smooth replacement of the remaining lean air with the molten steel occurs, and as a result, even if the diameter of this portion is small, it is possible to ensure that the molten steel has flowed into this region.

As described above, even when the molten steel is allowed to naturally flow into the sampling pipe with the lower end side having a smaller diameter, the molten steel can more reliably flow into the lower end side. Can be further accelerated, and a solidified body having no shrinkage hole can be more reliably obtained in this portion.

Then, the molten steel obtained in this way is rapidly cooled with a refrigerant to solidify it, and the overall cooling rate is further increased, resulting in a finer structure and gas in the steel. The diffusion is further suppressed, which allows a more accurate analysis.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In FIG. 1, reference numeral 1 denotes a molten steel sampling pipe, which is made of heat-resistant quartz. In the present embodiment, the sampling tube 1 is constructed by welding the lower end of the upper pipe portion 3 to the upper end of the lower pipe portion 2 so that the upper pipe portion 3 is continuously provided above the lower pipe portion 2. There is. The lower pipe part 2 has a bottom, the outer diameter is 8 mm, and the vertical dimension is 23 m.
m, wall thickness 0.5 mm. The upper and lower ends of the upper pipe portion 3 are open, the lower end portion is reduced in diameter to form a reduced diameter portion, and the upper end of the lower pipe portion 2 is joined to the end surface of this reduced diameter portion. The upper pipe portion 3 has an outer diameter of 20 mm, a vertical dimension of 180 mm, and a wall thickness of 1.5 m.
m.

The molten steel inflow port 4 has a diameter of 8 mm, and the dimension from the center of the inflow port 4 to the lower end of the upper pipe part 3 is 60 mm, and the upper pipe part 3 is opened at a midway position in the vertical direction. The molten steel flows in through the inflow port 4 at the time of immersion in the molten steel, which will be described later, and thereafter, when the sampling pipe 1 is pulled up from the molten steel, the molten steel flowed in above the inflow port 4 flows out through the inflow port 4. Then, the molten steel that has flowed in below the inflow port 4 is held as it is, and then cooled and solidified by a cooling device described later. Therefore, in the above, the portion below the molten steel inflow port 4 is configured as the molten steel holding portion.

Reference numeral 5 denotes a slag intrusion prevention material, which is made of copper having a melting point lower than that of molten steel, has an annular shape, and is fitted on the upper pipe portion 3 to close the inflow port 4, and its thickness is set to 0.3 mm.

6 is a paper tube, which is externally fitted to the upper end of the upper tube portion 3 and is joined with a screw 7 and an adhesive, and has an outer diameter of 30 mm, a vertical dimension of 300 mm,
The wall thickness is 6.5 mm. The paper tube 6 may be replaced by a glass fiber or ceramic tube, as long as it has a low thermal conductivity.

Reference numeral 8 denotes a molten steel inflow prevention member (closing member), which is filled in the upper opening of the upper pipe portion 3 to close the opening.

Then, a steel rod (not shown) is fitted into the upper end opening of the paper tube 6, and the steel pipe is held to hold the molten steel (about 1600) in the furnace.
℃) for about 3 seconds. As a result, the slag intrusion prevention material 5 melts and molten steel flows into the sampling pipe 1 through the inflow port 4. The slag intrusion prevention material 5 prevents the slag on the molten steel surface in the furnace from invading the sampling pipe 1.

It should be noted that in the above, the molten steel is allowed to naturally flow into the sampling pipe 1 without being evacuated. At this time, the air in the sampling tube 1 immersed in the molten steel is heated to about 1600 ° C.,
The volume expands about 7 times. This expanded amount is discharged from the inflow port 4. Therefore, the density of the air inside is 1/7
Becomes a sparse state. This state is maintained even during the inflow of molten steel because the upper end of the sampling pipe 1 is closed by the inflow prevention material 8, and therefore, the molten steel that has flowed into the sampling pipe 1 through the inflow port 4 has a small diameter. The lean air remaining in the side pipe portion 2 is also replaced in the side pipe portion 2 and surely flows into this portion.

After the molten steel is collected in the sampling pipe 1 in this manner, the sampling pipe 1 is then cooled with a refrigerant (water of 0 ° C. in this embodiment) to be solidified. At this time, cooling is performed while maintaining the vertical positional relationship between the upper pipe portion 3 and the lower pipe portion 2. Then, as shown in FIG. 2, of the solidified molten steel, the portion solidified in the lower tube portion 2 is used as a gas analysis sample 9.

In the gas analysis, the sample 9 is divided into a plurality of pieces according to the type of gas to be analyzed, and the surface is polished before use. In this embodiment, the lower end side 9a of the sample 9 is hydrogen and the upper side thereof is
9b was subjected to oxygen and nitrogen analysis. This is used for the analysis of hydrogen which is easy to diffuse because the cooling rate is higher toward the lower end and the structure is densified and gas diffusion is less likely to occur.

FIG. 3 shows the results of quantifying hydrogen according to this example in comparison with the results of quantifying hydrogen according to the conventional techniques shown in FIGS. 5 and 6. Since the one shown in FIG. 6 is considered to be theoretically the best, its analytical value is used as a reference value. In FIG. 3, the horizontal axis is the reference value and the vertical axis is the analysis value. ● indicates the analysis result according to this embodiment, ⊚ indicates the analysis result according to FIG. 5, and the solid line indicates the reference analysis according to FIG. The values are shown, and the two-dot chain line shows the deviation (%) from the standard analysis value. As a result,
The analysis value according to this example shows an analysis value within a range of ± 10% from the reference value, whereas the analysis value according to FIG. 5 is 20 to 70% lower than the reference value. It can be seen that the analysis value obtained by is highly accurate.

(Effect of the Invention) According to the present invention, when the molten steel collecting pipe is immersed in the molten steel to collect the molten steel, the molten steel can be collected by natural inflow without using vacuum suction, and the molten steel collecting pipe is also provided. It is possible to obtain a solidified body in which the generation of shrinkage holes is suppressed at the lower end side of the, and a gas analysis sample in which diffusion escape of gas is suppressed can be obtained from this portion.

Therefore, it is not necessary to evacuate the inside of the sampling tube in advance, and a shape having a small diameter and a thin wall at the lower end side can be relatively easily produced by using, for example, a quartz tube. Since it is not necessary to perform a vacuuming and sealing process, the manufacturing cost can be reduced. Moreover, since it is possible to obtain a sample in which diffusion escape of gas in molten steel is suppressed, a more accurate analysis value can be obtained without performing work such as separately collecting and analyzing escape gas. ,
Analysis work becomes easy.

[Brief description of drawings]

FIG. 1 is a front view of a sampling device according to an embodiment of the present invention, FIG. 2 is a sample for the same gas analysis, FIG. 3 is a diagram showing the results of the same analysis, and FIG. 4 is a sampling for a conventional example. FIG. 5 is a cross-sectional view of a sample collecting tube according to another conventional example, and FIG. 6 is a perspective view of a sample collecting tube according to still another conventional example. 1 ... Molten steel sampling pipe, 2 ... Lower pipe part, 3 ... Upper pipe part,
4 ... Molten steel inlet, 8 ... Inflow prevention material (blocking member), 9
…… A sample for gas analysis.

Continuation of the front page (56) Bibliography Sho 56-9040 (JP, U) Japan Society for the Promotion of Science "Commentary on Rapid Iron and Steel Analysis" Maruzen P. 517-524 (1966)

Claims (3)

(57) [Claims] 1. A molten steel sampling pipe, into which molten steel flows into the molten steel through a molten steel inflow port by immersing the molten steel in the molten steel, wherein the molten steel sampling pipe is provided with a molten steel holding portion at a lower end extending downward from the molten steel inflow port. In addition to being formed, the lower side of the molten steel holding portion is smaller in diameter and thinner than the upper side with a reduced diameter portion provided at a midway position in the up-down direction sandwiched between the molten steel holding portion. Instrument for collecting gas analysis samples. 2. A molten steel sampling pipe having a molten steel holding portion that is closed at the lower end and extends downward from the molten steel inflow port, and the lower side of the reduced diameter portion of the molten steel holding portion at a midway position in the vertical direction is formed to have a smaller diameter than the upper side. A method for collecting a sample for gas analysis performed by using a method in which the internal space communicating with the molten steel inflow port of the molten steel sampling pipe is made to be a closed state in the molten steel except for the molten steel inflow port, and then the molten steel is allowed to naturally flow in. A method for collecting a sample for gas analysis in molten steel, which comprises pulling up and rapidly cooling with a refrigerant, and using a solidified body below a reduced diameter portion in the molten steel holding portion as a sample for gas analysis. 3. The molten steel sampling pipe is formed in an upper end opening shape and a molten steel inflow port is provided on a side wall surface. A closing member for closing the upper end opening is attached to the molten steel sampling pipe, and the molten steel is immersed in the molten steel to melt the molten steel. The method for collecting a sample for gas analysis in molten steel according to claim 2, wherein the method is a natural inflow.