JPH0894609A - Preparation method and device for sample for component analysis of pig iron - Google Patents

Abstract

PURPOSE: To quickly obtain accurate result of component analysis of pig sample provided to luminescence spectroscopic analysis or fluorescence X-ray analysis. CONSTITUTION: A column shape pig iron sample 1 is cut with a grindstone cutter 4 to eliminate the edges and obtain a plane cut surface. Then, the cut surface is heated with a high frequency induction heater 5 while measuring the surface temperature. As soon as it reaches a specific temperature, the heating is terminated and the pig is quenched under a cooling water spray 8 and the surface is polished to be a surface for analysis with a polisher 9. As grapphite deposited in the sample pig annihilate by heat quenching and decarbonized layer is removed by the polishing, white pig iron not affected by decarbonation can surely be obtained and the accuracy of analysis is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preparing a sample when components in pig iron are analyzed by fluorescent X-ray analysis or emission spectroscopy.

[0002]

2. Description of the Related Art Hot metal from a blast furnace is subjected to hot metal pretreatment such as desiliconization, dephosphorization, and desulfurization, and then transferred to steelmaking processes such as converter blowing, but refining in the steelmaking process is accurate. In order to perform efficiently and efficiently, samples for component analysis are collected at each stage,
Components such as carbon, silicon, manganese, phosphorus and sulfur are analyzed.

In addition to accuracy, these analyzes are required to obtain analysis results quickly, and application of instrumental analysis such as emission spectroscopy and fluorescent X-ray method has been desired. However, in these analysis methods, the sample is made mainly in a circular shape, a columnar shape,
The cross section was subjected to final polishing to be used as an analysis surface, but pig iron contained a large amount of carbon, unlike steel, and graphite was likely to precipitate during solidification, which hindered their application. That is, the deposited graphite causes discharge disturbance or abnormal discharge in the emission spectroscopy, and the fluorescent X
The line was the cause of the decrease in accuracy.

In order to solve this problem, a method of preventing precipitation of graphite has heretofore been considered by dissolving a pig iron sample once or by rapidly cooling and solidifying it into a limited shape at the stage of taking a sample from the hot metal. For example, Analytical Chemistry Vol. 37,
In p589, 1988, hot metal is shallowly poured into a thick-walled copper mold having a circular bottom surface at the time of sampling to prepare a disk-shaped sample whose analysis surface is rapidly cooled. And, it is reported that the accuracy of X-ray fluorescence analysis is improved in this sample.

[0005]

However, in the case of a disk-shaped sample, the disk has to be thinned for the purpose of quenching, and the slag remains or there is a pinhole on the analysis surface. Therefore, all the collected samples could not be used for analysis. Also, the conditions for collecting the analysis sample,
For example, since the hot metal temperature and components are not constant, the degree of quenching is different and the reproducibility is not sufficient.

In order to solve this problem, the present invention has been made, and even in the case of a columnar sample in which graphite is precipitated, the influence of the precipitated graphite is eliminated by subjecting it to an appropriate heat treatment, which is particularly important. The aim is to improve the analysis accuracy of carbon, which is a major component.

[0007]

Means for achieving the object is to cut and remove the tip of a columnar sample of pig iron, heat it by high frequency induction until the temperature of the cut surface reaches a predetermined temperature, and then rapidly cool it. A method for preparing a sample for pig iron component analysis for finishing polishing the cut surface to form an analysis surface, and a preparation device suitable for executing this preparation method, wherein a moving platform for mounting and moving a columnar sample A grinder cutting machine, a radiation thermometer, a high-frequency induction heater, a cooling water ejector, a finishing polisher and an air ejector are arranged in this order along with a control device that controls the operation of these devices and the movement of the sample. It is a device for preparing a sample for the component analysis of pig iron.

[0008]

[Function] In the gradually cooled pig iron lump, defects such as slag residue and pinholes are concentrated in a special place such as the tip of the lump. The reason why the tip end of the columnar sample is cut and removed is to remove a portion where the components are biased, and even in the case of the cast sample, it is sufficient to remove the tip end of about 10 mm. Also, cutting results in a flat cut surface. This operation can be omitted in a cut sample with a clear history.

[0009] The hot metal contains about 4 wt% of C, and since this sample is gradually cooled, precipitation of graphite is inevitable and it is a gray cast iron. When this sample is heated, the precipitated graphite disappears. When rapidly cooled in that state, so-called white pig iron in which the precipitated graphite disappears is obtained, and the influence of the precipitated graphite is removed.

Since it is sufficient that the white pig iron is formed in the vicinity of the analysis surface, it is not necessary to heat the entire sample. The heating time is preferably short because of the rapidity of analysis, and high-frequency induction heating is suitable for heating the vicinity of the analysis surface.

FIG. 2 shows the relationship between the temperature reached on the cut surface and the depth of the white pig iron layer after the heat treatment. If the white pig iron layer is heated to about 800 ° C., a white pig iron layer having a thickness of more than 1 mm can be obtained.

Decarburization must be paid special attention to in the heat treatment. Unlike the steel sample, the pig iron sample contains a large amount of carbon, so the decarburization rate is high. If the ultimate temperature is not set in consideration of this reduction in decarburization, the white pig iron layer will lack sample representativeness. In order to suppress the decarburization amount to the minimum, high-frequency induction heating is a suitable heating method because heating can be started and stopped quickly and temperature can be raised in a short time.

FIG. 3 shows the results of investigating the depth of the decarburized layer by changing the ultimate temperature of the cut surface of the sample having a carbon content of 4 to 4.7 wt%. The time from the heating stop to the water cooling start is 3
Seconds.

When the temperature reached is about 800 ° C, the decarburized layer is less than 0.2 mm, but when it reaches 1400 ° C, it is 0.5 mm.
Reach near In emission analysis and fluorescent X-ray analysis, the analysis surface is subjected to finish polishing in order to make the influence of the analysis surface on the irradiation line constant, but the thickness of the surface layer removed by this finish polishing is 0.5 mm. It is a degree.

Further, when the ultimate temperature reaches 1400 ° C., the sample may melt and the shape may be lost. As described above, it is most appropriate to determine the ultimate temperature in the range of 900 ° C to 1200 ° C in consideration of white pig ironing and decarburization. In this case, the white pig ironed layer having a sufficient depth can be obtained and the decarburized layer Is sufficiently removed by finish polishing.

Such sample preparation is also easy to perform automatically. That is, while a columnar sample is placed on a gantry and moved, first a flat cutting surface is made by a grindstone cutting machine, and then a coil for high frequency induction heating is heated with the cutting surfaces facing each other. At this time, the temperature of the cut surface is measured by a radiation thermometer, the fact that the temperature has reached a predetermined temperature is detected, and the heating is stopped. Immediately after the heating is stopped, it moves to the cooling position and jets cooling water to quench it. After that, finish polishing is performed to remove polishing powder and the like, and the finished surface is cleaned to be an analysis surface. The cleaning may be performed by jetting air, and it is not necessary to perform wet cleaning.

[0017]

EXAMPLE A sample was taken from the hot metal immediately before being inserted into a converter, and fluorescent X-ray analysis and emission spectroscopic analysis were carried out to examine the sample yield and analysis accuracy.

The samples are columnar ones having a diameter of 33 mm and a height of about 50 mm, and conventional disc-shaped ones having the same diameter and a thickness of 5 mm.

An apparatus for preparing a columnar sample is shown in FIG. Sample 1
Is held by the supporter 2 and moves on the movable base 3. First, the grindstone cutting machine 4 cuts an upper portion of about 15 mm to remove an end portion where a defect may exist and to form a cut surface. Next, it is heated by the high frequency induction heater 5. At this time, the temperature of the cut surface is measured by the radiation thermometer 6, and when the temperature reaches 1000 ° C., the control device 7 stops the heating of the high frequency induction heater 5. The heating conditions were 350 kHz and 3 kW, and the heating time was about 30 seconds. After this, the sample 1 immediately moves and is cooled by the cooling water jetting device 8, a smooth surface is obtained by the finishing polisher 9, and polishing dust is removed by the air jetting device 10 for finishing.
It takes about 2 seconds from the end of heating to the start of water cooling, and the cooling time is about 20 seconds.
Second, the amount of cooling water jetted was 1 liter per minute, and a cup grinder was used for finish polishing.

Table 1 shows the results of investigating the carbon content by fluorescent X-ray analysis and emission spectroscopic analysis together with a comparative example using a columnar sample but not heating and cooling, and a conventional example using a disc-shaped sample. Show.

The number of samples is 50 each, and the reproducibility of the analytical value (σd) is about 50 to 3.5 wt% of carbon content.
However, some disc-shaped samples could not be analyzed because of pinholes, residual slag, etc., and these samples were excluded.

[0022]

[Table 1]

In both the results of the fluorescent X-ray analysis and the emission spectroscopic analysis, the yield of the prepared sample was 1 in the example of the present invention.
Reproducibility is 0.029 wt% and 0.036, respectively.
It was very good with wt%. On the other hand, in the comparative example, the yield of the sample was good in the fluorescent X-ray analysis but the reproducibility was poor, and the yield and the reproducibility of the sample were poor in the emission spectroscopic analysis. The reason why the sample yield was poor in the emission spectroscopic analysis was that the sample with carbon concentration of 4.3 wt% or more could not emit light because of precipitated graphite. In the conventional example, the yield of the sample was poor and the reproducibility was inferior by one digit as compared with the example.

The reproducibility of the comparative example is poor because the precipitated graphite has not disappeared, and the reproducibility of the conventional example is inferior to that of the example because the degree of quenching is not as stable as that of the example. is there.

[0025]

As described above, according to the present invention, a pig iron columnar sample is used, and the cut surface thereof is heated at a reached temperature limited, quenched, and finally polished to obtain an analysis surface. As a result, a sample free from defects such as pinholes, white pig iron, and unaffected by decarburization was obtained, and the analysis accuracy was dramatically improved. As described above, the effect of the present invention that enables rapid analysis such as fluorescent X-ray analysis or emission spectroscopic analysis with satisfactory accuracy is particularly large in steel manufacturing control.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus for preparing a sample for pig iron component analysis used in Examples.

FIG. 2 is a diagram showing a relationship between an ultimate temperature and a depth of a white pig iron layer when a sample is heated.

FIG. 3 is a diagram showing a relationship between an ultimate temperature and a depth of a decarburized layer when heating a sample.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Specimen 2 Supporter 3 Moving stand 4 Grinding stone cutting machine 5 High frequency induction heater 6 Radiation thermometer 7 Control device 8 Cooling water ejector 9 Polisher 10 Air ejector

Claims (2)

[Claims] 1. After cutting a columnar sample of pig iron, it is heated by high-frequency induction heating until the temperature of the cut surface reaches a predetermined temperature and then rapidly cooled, and the cut surface is finish-polished to be an analysis surface. Method for preparing a sample for component analysis of pig iron. 2. A grindstone cutting machine, a radiation thermometer, a high-frequency induction heater, along a moving base on which a columnar sample is placed and moved.
An apparatus for preparing a sample for pig iron component analysis, comprising a cooling water ejector, a finish polisher, and an air ejector, which are arranged in this order, and which is equipped with a control device for controlling the operation of these devices and the movement of the sample.