JPH0540091A - Molten metal composition analysis method - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain accurate analysis results automatically and quickly by significantly shortening the transportation time and the pretreatment time for cooling, cutting, polishing, etc. of the sample whose components are to be analyzed. [Structure] Before separating the paper tube 1 from the sublance, the sampled sample S is held by holding mechanisms 13 and 14, and cooled by jetting cooling water, cut by a cutting machine 15, and polished by nitrogen purging. Then, the component analysis of the sample S is performed by the laser emission spectroscopy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal component analysis method for analyzing components of molten metal such as molten steel by laser emission spectroscopy.

[0002]

2. Description of the Related Art In refining work of molten metal, particularly in converter refining of steel, molten metal (molten steel)
There is a strong demand for higher accuracy in the component analysis and reduction of analysis time.

At present, as a typical component analysis method for molten steel used in the refining process of iron and steel, there is a discharge emission spectroscopic analysis method using electric discharge. In this method, for example, a sample that is a part of molten steel is sampled in a sampling container by the sublance method shown in Iron and Steel Handbook VOL2, p490, and then analyzed in a fully-equipped analytical room. ..

In this analysis method, the sample is sampled, the sample is taken out of the sampling container, the sample is transferred into the analysis chamber, the sample is cooled, cut, and polished. It takes about 5 minutes from the start of sampling to the completion of analysis processing. Considering that the refining process takes about 20 minutes, this 5 minutes can be said to be a very long time. For this reason, when the analysis results are obtained, the analyzed molten steel may have been already refined and transferred to the next step, or the components may be significantly different, and the analysis results cannot be effectively used. There are difficulties.

As a method for solving such a difficulty, for example, a method of analyzing the components of a pumped sample in the vicinity of the sublance rising end can be considered. In addition, after sampling a sample with a sublance or a similar device and then analyzing the components in the molten steel state in the vicinity of the sampling device, attempts have been made to shorten the sample transportation time and pretreatment time. There is.

Different from the above-described discharge emission spectroscopy, there have been attempts to directly analyze the components of molten metal (molten steel). Among such direct analysis methods, a sample is irradiated with laser light to generate plasma light on its surface, and the plasma light is spectrally analyzed to directly analyze the components of the molten metal, so-called laser emission spectroscopy. The method is widely used. Compared to discharge emission spectroscopy, this laser emission spectroscopy is less susceptible to changes in distance from the sample surface, has a short response time, and is capable of analyzing samples at a distance of about 1 m. It is advantageous in that it can be automated without being consumed. An example of a method and an apparatus for directly analyzing molten steel by using this laser emission spectroscopic analysis method is disclosed in JP-A-62-282247.

The method disclosed in Japanese Patent Laid-Open No. 62-282247 is such that a sample (molten steel) in a converter is pumped up by a heat-resistant cup, and the pumped sample is conveyed to a laser spectroscope for component analysis. Is. The cup attached to the tip of the sublance or a similar pumping device is provided with a suitable lid, and during sampling, the lid comes off in the molten steel after passing through the slag part on the molten steel. Molten steel flows in. After that, the cup passes through the slag again and the sample is pumped out of the converter. Since the slag and oxide film are mixed in the pumped sample, these are removed by tilting the cup and pouring out the molten steel. After that, the sample is conveyed to an analysis device arranged near the sampling device, and component analysis is performed while purging the sample surface with Ar gas. In this way, the method disclosed in Japanese Patent Laid-Open No. 62-282247 seeks to shorten the sample transport time and the pretreatment time and to speed up the analysis work.

Although various methods for directly analyzing molten steel by laser emission spectroscopy have been studied, it is difficult to transmit the laser light when the molten steel in the converter is directly irradiated with laser light for analysis. For some reason, stable analysis results cannot be obtained for a long period of time due to the reason that the optical system has to be arranged in a harsh environment, and it can be said that the present technology is impossible. Therefore, the above-mentioned Japanese Patent Laid-Open No. 62-282247
The method disclosed in the publication is practical as a laser emission spectroscopic analysis method.

[0009]

Immediately after sampling,
In the method of component analysis near the sublance by discharge emission spectroscopy, the transport time can be shortened,
It has not been possible to shorten the sample extraction time from the paper tube, sample cooling time, sample cutting and polishing time. The cooling, cutting, and polishing times of this sample depend on the cross-sectional area of the sample,
This cross-sectional area depends on the measurement area in discharge emission spectroscopy. In discharge emission spectroscopy, analysis is performed at least at two or more points on a measuring surface having a diameter of about 10 mm, and therefore the diameter of the sample needs to be several tens of mm or more, which cannot be made so small at present. Therefore, the current sample cooling, cutting,
It takes more than 1 minute for the polishing process, and it is necessary to increase the sublance.
Considering that it takes about 50 seconds, it is hard to say that this method can sufficiently shorten the analysis time.

On the other hand, in the method of directly analyzing molten steel by using the laser emission spectroscopy, since the sample pumped in the molten state is analyzed, the surface thereof is very likely to be oxidized. Therefore, it is difficult to stably prepare the sample surface from which the oxide film has been removed, and there is a problem that the analysis result obtained when online is automatically analyzed is not reliable.

The present invention has been made in view of such circumstances, and by carrying out the pretreatment of the sample before separating the paper tube from the sublance, it is possible to shorten the transportation time.
Further, by using the laser emission spectroscopic analysis method, the area of the sample can be reduced, the pretreatment time of the sample can be shortened, and the component analysis of the molten metal can be performed automatically and quickly. It is a main object to provide a method for analyzing a component of molten metal.

Another object of the present invention is to analyze a component of molten metal by sampling the molten metal using a container whose inner surface is coated with a refractory heat insulating material to obtain a sample having no space inside. To provide a method.

[0013]

According to a first aspect of the present invention, there is provided a method for analyzing a component of a molten metal, the method comprising: analyzing a component of the molten metal using a laser emission spectroscopy. Is sampled by the sublance method to obtain a sample having a cross-sectional diameter of 25 mm or less, and before the paper tube is separated from the sublance, the sample is cooled and cut, and the component analysis of the sample is performed.

The molten metal component analysis method according to the second invention of the present application is characterized in that, in the first invention, when a part of the molten metal is sampled, a container having an inner surface coated with a fireproof heat insulating material is used. And

[0015]

In the first invention, before the paper tube is separated from the sublance,
Since the analysis is performed by performing pretreatments such as cooling, cutting, and polishing, the transportation time can be significantly shortened.

Further, in the laser emission spectroscopic analysis method, it is possible to change the measurement area within the range where the power density of the laser beam is sufficiently obtained, but if the measurement area is made too small, the components of the sample will be affected by the influence of minute segregation. The reflected spectrum light cannot be obtained. As a result of investigating a measurement area capable of averaging minute segregation when measuring a solid sample by laser emission spectroscopy, when the irradiation diameter is about 1.5 mm or more, the analysis variation due to segregation is 1% in relative standard deviation.
We have found that we can do the following. On the other hand, if the measurement area is made too large, the power density of the laser light will decrease, the emission intensity will decrease, and the analysis accuracy will deteriorate. Therefore, it was found that a suitable irradiation diameter of the laser light is 1.5 to 2 mm. did. As described above, when the laser emission spectroscopic analysis method is used, the analysis can be performed in a smaller measurement area and the cross-sectional area of the sample to be sampled can be made smaller than when the discharge emission spectroscopic analysis method is used. Therefore, the time required for pretreatment such as cooling, cutting, and polishing of the sample is significantly reduced.

In the second aspect of the invention, when the molten metal flows into the container whose inner surface is covered with the refractory heat insulating material, the inflowing molten metal is not rapidly cooled, but the inside of the container is sufficiently filled with the molten metal. Later it begins to solidify. Further, the sample does not adhere to the inner surface of the container when cooled. Therefore, a sample having no space inside can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof by way of example of composition analysis of molten steel.

FIG. 1 is a schematic sectional view showing a part of the structure of a sampling device used in the method for analyzing the composition of molten metal (molten steel) according to the present invention. In the figure, 1 and 2 are papers connected vertically. It is a tube. From the lower part of the upper paper tube 1 to the central part of the lower paper tube 2, a container 3 for pumping the molten steel of the sample is housed. The container 3 has an inner diameter of 10 mm and a depth of 100 mm, and the container 3 is made of, for example, cast iron having a wall thickness of 3 to 6 mm, and the wall thickness is thin at the central cut portion. The inner surface of the container 3 is covered with the fireproof heat insulating material 4. A refractory material 5 is provided inside the paper tube 1 above the container 3.
Further, a molten steel intake port 6 is opened on the side wall of the paper tube 1 above the container 3, and a metal cap 7 is attached to the molten steel intake port 6. When the sublance descends and the paper tubes 1 and 2 are immersed in the molten steel, the metal cap 7 melts and comes off in contact with the molten steel, and the molten steel flows into the container 3 through the molten steel intake port 6. There is. In addition, container 3
The refractory heat insulating material 4 coated on the inner surface of is originally not intended to keep the molten steel warm for a long time, and thus is coated sufficiently thin.

Next, the sampling operation of the sample will be described. A paper tube 1, as shown in FIG.
Connect 2 to the sublance. The sub-lance is lowered to pass the slag and the paper tubes 1 and 2 are immersed in the molten steel. When the paper tubes 1 and 2 are immersed in molten steel, the metal cap 7
Melts and comes off, and the sample molten steel flows into the container 3 through the molten steel intake port 6. Since the inner surface of the container 3 is covered with the refractory heat insulating material 4, the molten steel that has flowed into the container 3 is not rapidly cooled, and begins to solidify after the inside of the container 3 is sufficiently filled with the molten steel. Further, since the sample does not come into close contact with the inner surface of the container 3 when the sample is cooled, no space is created inside the sample. After sampling the molten steel to be the sample, the sublance is raised, and the components of the sampled sample are analyzed at the highest rising position by the procedure described below.

FIG. 2 is a schematic diagram showing an implementation state of the molten metal (molten steel) component analysis method according to the present invention. Figure 2
(A) and (b) show the state of pretreatment, and FIG. 2 (c) shows the state at the time of analysis. Hereinafter, the procedure of the preprocessing and the analysis processing will be described with reference to FIG.

After raising the paper tubes 1 and 2 to the sub-lance rising end position, the paper tube 2 is removed, and the sample S is precooled together with the paper tube 1, and then the sample S is held and cooled while the sample S is cooled.
Is cut (FIG. 2 (a)). The sample S and the paper tube 1 are pre-cooled by jetting the cooling water from the cooling tube 11. The base end portion of the sample S is held by the holding mechanism 13 having the cooling water jetting portion 12 and forcibly positioned. After holding the sample S by the holding mechanism 13, the tip of the sample S is held by another holding mechanism 14, and the cutting machine 15 cuts the central position of the sample S. At the time of this cutting, the sample S is continuously cooled by the jet of cooling water from the cooling water jetting unit 12.

After cutting, the sample S held by the holding mechanism 14
Then, the surface is polished in some cases, and after nitrogen purging (FIG. 2B), the sample S is carried to the analysis position while being held by the holding mechanism 14. And in an argon gas atmosphere,
The sample S is irradiated with laser light in the arrow direction from the laser waveguide 16, and the components of the sample S are analyzed by spectral analysis of plasma light generated on the surface of the sample S (FIG. 2C).

When the molten steel was sampled by the above procedure and the composition analysis of the sampled molten steel was carried out, the required time in each step was specifically as follows. It takes 23 seconds to raise the sublance after the paper tubes 1 and 2 are immersed in the molten steel, and precooling and holding of the sample S are 3 seconds.
Seconds, cutting of sample S for 3 seconds, polishing purge for 5 seconds, transport for 5 seconds
Second, analysis was 20 seconds, and a series of analysis processing was completed in about 60 seconds in total. This processing time greatly shortens the time required for the conventional example.

Although molten steel is taken as an example in the above-mentioned embodiment, it is needless to say that the component analysis can be similarly performed in the case of other molten metals as well.

[0026]

As described above in detail, in the molten metal component analyzing method of the first invention, since the pretreatment is performed before the sublance is separated from the paper tube, the carrying time can be shortened and the laser emission spectroscopy can be performed. Since the analysis method is used, the measurement area of the sample can be reduced and the time required for pretreatment can be shortened. As a result, the molten metal (molten steel) can be automatically and quickly analyzed for its components during converter refining or immediately after the completion of refining. Furthermore, the analysis results can be fed back to the refining process. It becomes possible to shift to the next step after confirming.

Further, in the second invention, since the inner surface of the container to be sampled is covered with the refractory heat insulating material, it is possible to obtain a sample having no space inside.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of part of a sampling device used in a method for analyzing a component of molten metal according to the present invention.

FIG. 2 is a schematic diagram showing a state of implementation of pretreatment and component analysis in the molten metal component analysis method of the present invention.

[Explanation of symbols]

 1 Paper Tube 2 Paper Tube 3 Container 4 Refractory Insulation Material 6 Molten Steel Intake Port 11 Cooling Pipe 12 Cooling Water Jet 13 Holding Mechanism 14 Holding Mechanism 15 Cutting Machine 16 Laser Waveguide S Sample

Claims (2)

[Claims] 1. A method for analyzing a component of a molten metal by using a laser emission spectroscopic analysis method, wherein a part of the molten metal to be analyzed is sampled by a sublance method and a diameter of a cross section is
A method for analyzing a component of a molten metal, wherein a sample having a size of 25 mm or less is obtained, and before the paper tube is separated from the sublance, the sample is cooled and cut to analyze the component of the sample. 2. The method for analyzing a component of molten metal according to claim 1, wherein a container having an inner surface coated with a refractory heat insulating material is used when sampling a part of the molten metal.