JP3039231B2 - Method and apparatus for rapid analysis of steel components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for quickly measuring the chemical composition of molten steel in order to grasp the state of refining during the refining of steel.

[0002]

2. Description of the Related Art Since the composition of steel greatly affects the properties of steel, its composition analysis is indispensable for quality control. In particular, in oxygen blowing of steelmaking, the blowing time is as short as about 15 minutes, and the analysis is performed at the end of the period to feed back the data and control the operation so that the steel composition and the molten steel temperature fall within the planned range. Speed in seconds is required.

[0003] As a conventional method for analyzing a billet, JIS-G
The mainstream is an emission analysis method by spark or arc discharge excitation specified in -1253 and the like. in this way,
It is characterized in that, by appropriately preparing and appropriately analyzing a massive sample, the analysis of carbon, which is particularly important in the steel composition, can be performed relatively quickly.

[0004] The appropriate adjustment and appropriate conditions include the following. In order to avoid the selectivity of the discharge point, the analysis part of the sample should be smooth and the surface roughness should be constant, the influence of the sample temperature on the measured value should be large, and the sample temperature should be controlled within a certain range. If there is a defect such as a pinhole, abnormal discharge occurs and a correct result cannot be obtained. Therefore, it is necessary to identify abnormal discharge by repeated measurement and eliminate the result.

In order to maintain such conditions, the speed of analysis has been limited. That is, before the molten steel sample is collected and before it is set in the analyzer, transport of the collected sample, cooling, cutting, rough polishing of the cut surface, preparation of surface roughness adjustment by finish polishing, etc., are necessary. Multiple locations must be analyzed.

[0006] Measures have been proposed for these restrictions. For example, in Japanese Patent Application Laid-Open No. 3-261842,
A method is disclosed in which rough polishing and finish polishing are selectively used by controlling the rotation speed and contact pressure of a grindstone, and the same device is continuously used to save time for mounting and removing a sample to and from a device. Japanese Patent Application Laid-Open No. 62-220835 discloses a method for analyzing a high-temperature sample without waiting for cooling to room temperature by measuring the temperature of a massive sample and correcting the analysis value. The technology is shown.
Further, Japanese Patent Application Laid-Open No. 62-245946 discloses a technique for setting a discharge position avoiding a defective position by providing an image processing device as a measure against a defect such as a pinhole.

On the other hand, a massive sample is not directly emitted, but is irradiated with a laser in a sample chamber in an inert gas atmosphere, and a part of the sample is vaporized into fine particles. The fine particles are analyzed by an ICP (High Frequency Inductively Coupled Plasma) analyzer. There is a method (referred to as laser / ICP analysis) in which light is emitted or ionized for analysis. In this method, the accuracy of carbon analysis is questionable and is not practical in steel composition analysis, but attempts have been made to shorten the operation time. For example, Japanese Unexamined Patent Publication No. Hei.
No. 6 discloses a sample exchange device which makes the lower half of the sample chamber slidable, thereby facilitating attachment and detachment of the massive sample to the sample chamber and adjustment of the position.

[0008]

However, any of the techniques disclosed in Japanese Patent Application Laid-Open Nos. 3-261843, 62-245946 and 3-167446 is based on the premise that cutting preparation of a sample is inevitable. This is a stand-alone improvement that allows a slight reduction in time, but has not significantly improved the speed. Also, the technique disclosed in Japanese Patent Application Laid-Open No. 62-220835 does not essentially eliminate the drawback of emission spectroscopy, which is greatly affected by the sample temperature, so that the correction by the disclosed method is restricted to a limited temperature range. Is valid within. The disclosed study range is 200 ° C
Up to this point, the effect and reliability of a hot sample of about 1000 ° C. in a red-hot state are questionable.

As described above, the conventional rapid analysis technique requires a sample preparation for obtaining an analysis surface that is smooth, has a constant surface roughness, and has no defect in emission spectrometry, and has a large influence of the sample temperature, and has a large influence on a high-temperature sample. Since the analysis value cannot be guaranteed, there is a limit to the speed of analysis, and the conventional laser / ICP analysis also has a limit to the speedup because sample preparation is premised. Questions about the analytical values remained.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and it does not require the preparation and cooling of a massive sample, which overcomes the conventional limitation of speeding up, and includes a more rapid measure including a measure for carbon component analysis. An object of the present invention is to provide a technique for analyzing steel components.

[0011]

Means for achieving the above object is to provide a rapid analysis for measuring the component composition of molten steel by laser / ICP analysis on a massive sample obtained by collecting a part of molten steel and solidifying it. The sample is put into a sample holding section in a sample chamber in an inert gas atmosphere of an analyzer in a red-hot state, and fine particles generated by irradiating the surface of the massive sample with a pulse laser beam are supplied to an ICP analyzer with an inert gas. This is a steel component rapid analysis method characterized in that the component is analyzed by analyzing only the fine particles that have been conveyed and generated from a depth of 25 μm or more below the surface. In addition, as one of the apparatuses for performing this method, a sample chamber for storing a massive sample having a predetermined shape, a laser oscillator for irradiating the massive sample with pulsed laser light to generate fine particles, An ICP analyzer for transporting the fine particles and analyzing their components, and a carrier gas piping system for sending a carrier gas to the sample chamber and further connecting the sample chamber and the ICP analyzer, wherein the sample chamber is An analysis cell portion and a sample holding portion communicating with the analysis hole portion through an exposure hole are provided.
The laser is irradiated inside the sample through the
Pass the laser light and inactive transport the generated fine particles
Configured to circulate gas and transport it to the ICP analyzer
And the sample holding part has the same curved surface as the bulk sample of the predetermined shape.

Further, in the method and the apparatus, which are preferred embodiments of the above-described method and apparatus for rapid analysis of steel components, the pipe material of the carrier gas piping system is metal or glass, and the pipe for sending the carrier gas to the sample chamber. The system is equipped with a gas purification device for removing carbon components in the carrier gas, and the sample chamber has a mechanism for preventing the sample from being oxidized by keeping the sample chamber closed except for the inlet and outlet of the carrier gas. The above-mentioned steel component rapid analyzer and the use of Ar gas as an inert gas, which is highly refined to use a carbon content of 1 μg / L or less, and retains a massive sample in an inert gas atmosphere Using a pulsed laser that oscillates at a frequency of 100 Hz or more, the irradiation spot density of the laser light is set to 10 ⁸ W / cm ² or more and 10 ¹¹ W / cm ² or less, and the oxidation is prevented. Do not move the position This is a method for rapid analysis of steel components in which laser beam irradiation is performed.

[0013]

According to the present invention, a lump for analysis obtained from molten steel is used.
Put the sample into the sample holder in the sample chamber while keeping it hot
Analysis without having to wait for sample cooling.
The analysis can be started. Also, as described later,
Can be analyzed without cutting, but as is well known
Even at room temperature, even hard steel is very soft in the glowing state,
Sample cutting can also be easily performed. Lump test as sample holder
If a material with the same curved surface is used,
At the same time, the lump sample is stored on the sample holder close to this same curved surface.
Will be delivered. In this way, the massive sample is put into the sample holder.
The sample is stored just by
Installation work of the sample becomes easy. By the way, in this invention
Since dealing with a bulk sample of the red-hot state at room temperature in the sample chamber,
The sample temperature changes every moment during the analysis . When irradiating a pulsed laser beam to the massive sample whose temperature is changing to generate fine particles, it is extremely important how the analytical value is affected.

In the irradiation of the pulse laser, high-density energy is applied, so that the temperature at the irradiation point becomes extremely high. Also, in the process of atomization, a part of the massive sample may be faithfully atomized instead of asking the excited state of the element as in emission analysis. Therefore, it is considered that the influence of the temperature of the massive sample is extremely small. To confirm this, 1000
A laser / ICP analysis was performed on the massive sample heated to a temperature of ℃ or more using a pulsed laser beam during the cooling process to examine the effect.

FIG. 3 shows the result. In the figure, the vertical axis represents the analysis value and the horizontal axis represents the sample temperature. (A) FIG.
(B) The result of P is shown in FIG. Regarding any component, even if the temperature changes, the analytical value hardly changes and is not affected by the temperature.

In a laser / ICP analysis in which a fine particle sample is obtained by irradiating a pulsed laser beam, even if the sample temperature changes in the red heat state, the analysis value is essentially not affected by the temperature of the block sample. Therefore, a reliable analysis value can be obtained. It goes without saying that the cooled sample undergoes less temperature change and is therefore equally reliable.

In the case of a massive sample obtained by solidifying molten steel, the surface is more or less affected by oxygen in the atmosphere, and the surface layer does not represent the component composition of the sample. Fig. 4 shows the result of examining this situation.
Shown in The cross-section of a cut sample of a truncated cone with a small diameter of 30 mm and a large diameter of 33 mm was subjected to line analysis from side to inside using SIMS and XMA. The measurement components were P and M.
n and S. In the figure, the vertical axis represents the measured intensity of each component, and the horizontal axis represents the distance from the surface.

The measured values of any of the components fluctuated up to a few tens of μm , but the fluctuations were not observed by 20 μm.
When it is 25 μm or more, it does not change from the inside of the massive sample.
It turns out that the effect of atmospheric oxygen is not received. Note that M
small peaks seen in n and S, the position is considered to segregation of MnS inclusions from the same thing. Based on the above knowledge
According to the present invention, in the case of a depth of 25 μm or more below the surface of the sample,
Perform analysis on the part.

Since it is easy to dig down about 25 μm from the surface by laser light irradiation, the fine particles generated from a depth of 25 μm or more below the surface are not analyzed, but the initial fine particles after the start of irradiation. Thus, fine particles sufficiently representing the sample can be obtained without preparation such as cutting or polishing the massive sample.

Next, the problem of impairing the sample representativeness of the fine particles is a problem of contamination and a problem of selective evaporation. Regarding a decrease in the accuracy of ICP analysis, there are fluctuations in the generation speed and size of the fine particles and variations in the transport amount. In the ICP analysis, the transported fine particles
r Excited by plasma flame, high purity Ar
The use of gas is convenient because it does not contain any interfering elements.

However, commercially available high-purity Ar gas contains several μg / L of carbon in the form of hydrocarbon or the like. By using this impurity carbon at 1 μg / L or less, trace carbon in steel can be analyzed with high accuracy.

In order to remove the impurity carbon, a metal getter type purifying apparatus can be used, and the purifying apparatus may be provided in a piping system for sending the carrier gas to the sample chamber. And
In order to prevent re-contamination during transportation, a metal or glass from which a clean surface is easily obtained is used as a piping material. The selective evaporation, the generation speed of the fine particles, and the size of the fine particles are affected by the laser light irradiation conditions.

The reason for using the pulse laser is to increase the irradiation point density of the laser beam and to reduce the selectivity of evaporation. When the irradiation point density of the laser beam is low, the generation speed of the fine particles is low, resulting in insufficient ICP analysis sensitivity and high selectivity of evaporation. If it is too large, Ar gas is ionized to generate plasma. This is called a breakdown phenomenon. When this phenomenon occurs, the energy of the laser beam does not contribute to the generation of fine particles. The allowable range of laser beam irradiation point density is 10 ⁸ W / cm ² or more and 10 ¹¹ W / cm
cm ² or less. In addition, under these conditions, the diameter of the obtained fine particles is 0.1 μm or less, and is regarded as uniform in the ICP flame.

The analysis accuracy when the pulse frequency is 20 Hz is significantly different from that when the pulse frequency is 100 Hz or more, and deteriorates. It is considered that the supply of the fine particles to the ICP flame is not stable when the frequency is low. Above 100 Hz, there is no difference and it is good.

In addition, continuous irradiation of the same point with a high-frequency pulse promotes selective evaporation and shifts between the irradiation surface and the focus with the number of irradiations, thereby reducing the amount of generated fine particles. By moving the irradiation point, these two points are eliminated, and furthermore, it is possible to avoid an extreme influence on the analysis value of the decontamination unit.

Next, the operation of the apparatus will be described with reference to FIG. In the figure, 1 is an analysis cell section, 2 is a sample holding section, 3 is a bulk sample, 4 is a laser oscillator, 7 is a carrier gas pipe, 8 is an ICP analyzer, 10 is a laser beam, and 21 is an exposure hole.

The sample chamber is composed of an analysis cell section 1 and an exposure hole 21 therein.
The mass sample 3 is accommodated in the sample holding unit 2. The laser light 10
The laser beam is emitted from the laser oscillator 4, passes through the analysis cell 1 and the exposure hole 21, and is irradiated on the surface of the massive sample 3. Analysis cell part 1
The sample holding unit 2 has an inert gas atmosphere to prevent oxidation of the sample, and an inert carrier gas is sent to the analysis cell unit 1. Fine particles generated by laser light irradiation
With this carrier gas, the carrier gas pipe 7
Through the ICP analyzer 8 where it is analyzed.

It is important to send the generated fine particles to the ICP analyzer 8 at a constant speed, in order to ensure the analysis accuracy, but the sample holder 2 has the same curved surface as the massive sample 3. And these surfaces are in close contact and the exposed hole 21 is
And the carrier gas containing the fine particles does not escape to the sample holding unit 2, so that the fine particles are stably
It can be sent to the CP analyzer 8. Further, when the side surface of the massive sample 3 is housed in close contact with the exposure hole 21, the focus of the laser beam 10 can be fixed and the control time can be reduced.

When the mass sample 1 is delivered, the sample chamber is divided into the analysis cell section 1 and the sample holding section 2, so that it is not necessary to directly expose the analysis cell section 1 to the atmosphere when storing the sample.
Therefore, the operation of replacing the atmosphere in the analysis cell unit 1 with the inert gas is omitted.

Since the sample holder 2 is exposed to the atmosphere when the sample is stored, it must be replaced with an inert gas after storing the massive sample. In this gas replacement, the sample holder 2 has the same curved surface as the massive sample 3. In this case, the gap between the sample holder 2 and the massive sample 3 is small, the amount of replacement gas is small, and the time required for replacement is reduced.

The change in the composition of the massive sample itself is a problem peculiar to the red-hot sample, and decarburization by oxygen on the surface layer affects the carbon analysis value. This is why the sample holder is provided with a mechanism to prevent oxidation of the sample. This mechanism not only accommodates massive samples in the sample holder and creates an inert gas atmosphere, but also cools the sample as quickly as possible. Is desired.

[0032]

EXAMPLE Using the sample chamber shown in FIG. 2, a lump sample solidified by pumping from a converter was analyzed. The sample had a diameter of 30 at the bottom.
mm, an upper diameter of 33 mm, and a height of 70 mm. The inside of the sample holding unit 2 is a truncated cone-shaped space having a bottom diameter of 30.5 mm and a height of 120 mm and the same curved surface as the massive sample 3. An intake port 24 is provided at an upper portion of the sample holding section 2 and an exhaust port 25 is provided at a lower portion thereof, which is connected to a suction pump (not shown). did.

The peripheral wall was a double wall made of copper. Cooling water was supplied from a water supply / drain port 27 between the walls to protect the wall, and the massive sample 3 was quickly cooled to prevent its oxidation as much as possible. That is, the gas short-time replacement mechanism and the high-speed cooling mechanism of the sample serve as an oxidation prevention mechanism. The exposure hole 21 is a rectangle of 4 mm × 8 mm. The sample chamber was set so that the sample holder 2 was inclined 45 ° with respect to the vertical in order to make the side surface of the massive sample 3 closely contact the exposure hole 21.

The analysis cell section 1 also has a truncated cone shape, and a surface facing the exposure hole 21 is a laser transmission window 12 made of quartz glass. A carrier gas inlet 13 is provided near the transmission window,
The carry-out port 14 was provided near the exposure hole 21. Ar was used as a carrier gas, a Zr getter type purification device was used for purification, and a SUS pipe whose surface was purified was used as a pipe material.

As the laser oscillator, an Nd / YAG laser (wavelength 1.06 μm) with an ultrasonic Q switch was used.
The irradiation point and the focal point were controlled by the reflecting mirror 30 and the condenser lens 40. The irradiation point can be moved by rotating the reflecting mirror or moving the condenser lens in parallel. That is, the focal point is determined by the condenser lens, and the irradiation point moves in one axis direction by rotating the reflecting mirror 30. On the other hand, when the condenser lens 40 is moved in parallel within the effective diameter range, the irradiation point moves by the same amount in the same direction. By combining these two operations, scanning irradiation was performed by moving the irradiation point two-dimensionally.

The analysis was performed as follows. A commercially available high-purity Ar gas was used as an inert gas, and by purifying the same, the C concentration was from 4 to 5 μg / L to 0.2 μm.
g / L. The surface temperature of the massive sample 3 immediately before being subjected to the analysis was 1100 ° C. This massive sample is called Ar
The gas is stored in the sample holding unit that keeps flowing the gas at 10 L / min, and the gas is exhausted to 1 atm by a suction pump of 50 L / min.
After that, both the intake and exhaust ports were sealed. It took about 5 seconds during this time. Cooling water continued to flow.

The reflecting mirror was rotated at a cycle of 30 Hz so that the deflection width of the focusing position was 2 mm, and the focusing lens was moved in parallel at a speed of 5 mm / minute to move the irradiation point. The moving speed was 300 mm / min, and the spot diameter at the focal point was 100 μm. It is preferable that the scanning be performed while scanning over 1 mm square, but the moving speed should be based on the product of the beam diameter and the pulse frequency.

As a preliminary treatment, scanning irradiation for 10 seconds was performed to remove 200 μm of the surface layer, and then measurement was performed. The flow rate of the carrier gas is 1 L / min. The laser beam was irradiated at a pulse frequency of 50 Hz or 1 kHz and an average output of 10 W.

An ICP emission spectrometer was used as the ICP analyzer. Regarding the conditions for generating the plasma flame, the high frequency output was 1.5 kW, the frequency was 27.12 MHz, the plasma gas flow rate was 15 L / min, and the auxiliary gas flow rate was 1 L / min. The transported fine particles were directly excited to emit light.

The spectroscope was a Passen-Runge type spectrometer, and the inside of the spectrometer was evacuated so that wavelengths of 200 nm or less could be measured. The analysis lines are C193 nm, P178 nm, S1
81 nm, Si 212 nm, Mn 252 nm, Al39
6 nm, Ni 232 nm, Cr 268 nm, Mo202
nm, Cu 325 nm, Fe 271 nm and 170 nm
Therefore, a multi-element simultaneous measurement system was adopted.

The light intensity was converted into a current by a photomultiplier, which was further converted into a voltage, and the integrated light intensity for 10 seconds was defined as the measured light intensity. In the analysis, an internal standard intensity ratio method using a ratio with the Fe intensity as a measured value was adopted. The conversion of the measured value to an analytical value was performed by measuring a standard sample to prepare a calibration curve and using the calibration curve.

The results of the analysis and the time required for the analysis, including the pretreatment, are compared with those of the conventionally used spark emission method.
It is shown in Table 1. Example 1 irradiated the laser beam at a pulse frequency of 50 Hz, and Example 2 irradiated the laser beam at 1 kHz. Further, in each case, the measurement was performed on a sample that was drawn from the same molten steel and solidified.

[0043]

[Table 1]

In the embodiment of the present invention, the difference in the analysis value between the samples is small, but in the conventional example, the difference is large, for example, 0.00 to 0.36% as seen in the analysis value of C. In the case of spark emission, the discharge range in one analysis is about 6 mmφ. However, if there are irregularities such as pinholes in this range, discharge is likely to occur in the convex parts and abnormal discharge cannot be avoided. This is considered to give a large difference in the analysis value between the samples.

On the other hand, in the case of laser irradiation, even if a projection exists in the irradiation range, the irradiation does not concentrate on the projection. The problem of laser irradiation is rather selective evaporation and stable production of fine particles of a certain amount or more. In particular, in Example 2 in which the laser irradiation conditions are limited, extremely excellent repetition accuracy can be obtained even with a partial component. ing. Furthermore, comparing the analysis times, in the embodiment of the present invention which does not require cooling of the solidified sample, the analysis is completed in about 60 seconds after the solidification of the molten steel, and the analysis time is reduced to less than half the conventional time.

[0046]

According to the present invention, a fine particle sample is collected from a lump sample by laser irradiation and the fine particle sample is excited. Therefore, unlike the conventional spark emission method, abnormal discharge does not occur and the influence of a change in the sample temperature is eliminated. Analytical values can be obtained without receiving. Therefore, cooling, cutting, polishing, and the like of the solidified sample are not required, and consideration is given to the setting of the sample in the analyzer, so that the molten steel component can be analyzed quickly. In addition, changes in the sample, contamination of the fine particle sample, the amount generated at the time of generation, stability, and selective evaporation are taken into account, so that highly accurate analysis results can be obtained.

As a result, the data feedback to the steelmaking operation control was quickened, and the control accuracy of the composition, temperature, etc. of the molten steel was improved. As a result, deviations from component specifications are reduced, efficiency is prevented from being lowered by after-blowing or addition of a cooling material, and energy saving is achieved. As described above, the effect of the present invention that the red-hot sample can be analyzed as it is is great.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an apparatus for explaining an apparatus of the present invention.

FIG. 2 is a conceptual diagram of a part of an apparatus used in an embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a mass sample temperature and an analysis value for explaining one principle of the present invention.

FIG. 4 is a diagram illustrating a relationship between a distance from the surface of a massive sample and measured intensity of a component for explaining another principle of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Analysis cell part 2 Sample holding part 3 Lumped sample 4 Laser oscillator 5 Laser light control device 6 Flow rate controller 7 Carrier gas piping 8 ICP analyzer 10 Laser light 12 Transmission window 13 Inlet 14 Outlet 21 Exposure hole 24 Inlet 25 Exhaust port 27 Water supply / drain port 30 Reflector 40 Condenser lens

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroaki Miyahara 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. Examiner Toshimitsu Suzuki (56) References JP-A-63-208738 (JP, A) JP-A-5-107186 (JP, A) JP-A-5-78108 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/62-21/74 G01N 33/20 G01N 1/02

Claims (4)

(57) [Claims] 1. A lump sample obtained by solidifying a part of molten steel and solidifying it
In the rapid analysis of measuring the component composition of the molten steel by laser / ICP analysis , a massive sample is put into a sample holding section in a sample chamber in an inert gas atmosphere of an analyzer while being in a red hot state, and the surface of the massive sample is A steel component characterized in that fine particles generated by irradiating a pulsed laser beam are conveyed to an ICP analyzer by an inert gas, and components are analyzed by detecting only fine particles generated from a depth of 25 μm or more below the surface. Quick analysis method. 2. An Ar gas is used as an inert gas, which is highly refined to use a carbon content of 1 μg / L or less, and a lump sample is charged into a sample holding section in an inert gas atmosphere and then charged. Prevents oxidation and 100Hz
The laser beam irradiation is performed by using a pulsed laser oscillating at the above frequency, setting the irradiation point density of the laser beam to 10 ⁸ W / cm ² or more and 10 ¹¹ W / cm ² or less and moving the irradiation point position. The steel composition rapid analysis method described. 3. A sample chamber for accommodating a massive sample of a predetermined shape, a laser oscillator for irradiating the massive sample with pulsed laser light to generate fine particles, and for transporting the generated fine particles and analyzing their components. And a carrier gas piping system for sending a carrier gas to the sample chamber and further connecting the sample chamber and the ICP analyzer, and the sample chamber communicates with the analysis cell section through an exposure hole. A sample holding unit, and this analysis cell unit
Laser light inside so that the laser light
The generated fine particles are passed through an inert carrier gas.
And transported to the ICP analyzer,
In addition, the sample holding section has the same curved surface as that of the bulk sample having the predetermined shape. 4. A piping system for transferring a carrier gas to a sample chamber, wherein the pipe material of the carrier gas piping system is a metal material or glass, and a gas purification device for removing a carbon component in the carrier gas is provided. 4. The steel component rapid analyzer according to claim 3, wherein the sample holding unit has a mechanism for preventing oxidation of the sample held and sealed except for the inlet / outlet of the carrier gas.