JPS6321864B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method and apparatus for directly, on-site, quickly and simply measuring the total amount of oxygen dissolved in molten steel in a melting furnace or ladle at a steelmaking site. It is.

In general, steel contains oxygen containing oxides, such as
Oxygen is contained in various forms such as SiO ₂ , MnO, and FeO, but if a large amount of these oxygen remains in steel, it deteriorates ductility and hot and cold workability, and also causes scratches on the material surface. Since harmful oxygen has an adverse effect, such as causing harmful oxygen, deoxidation treatment is performed in the steelmaking process to reduce and control harmful oxygen. If the amount of oxygen in molten steel could be directly measured in front of a melting furnace, ladle, etc., there would be great benefits in operations such as deoxidation.

There are two methods for measuring oxygen in steel: an indirect analysis method in which molten steel is drawn from a melting furnace or a ladle, the sample is prepared and analyzed, and a solid electrolyte sensor is directly immersed in the molten steel to detect its thermoelectromotive force. There are direct analysis methods such as measuring .

The former is the most common method, and various methods have been developed, from the old chemical method Hartey method to the vacuum dissolution method and inert gas blowing method, to the recent activation analysis method, and it is also highly accurate. In addition, the time required for analysis has recently improved from 2 minutes to 1 minute, and it has become widely established as a control analysis method in the steel manufacturing field, but the analysis itself can now be performed quickly. However, in both cases, it is necessary to prepare samples from solid metals, and preparation of analysis samples including sampling takes time and effort. I haven't reached it yet.

The latter method, which directly analyzes oxygen in molten steel, is preferable because it allows for quick feedback to the work site, but electrochemical methods using solid electrolytes are also less effective than the amount of gas released when molten steel solidifies. The gas pressure measurement method for estimating the amount of oxygen in molten steel is still in the experimental stage, and there are still problems with operability and accuracy, and all of these methods measure the amount of free oxygen in molten steel. Therefore, the current situation is that the measurement of the total oxygen content for evaluating the internal quality of steel must be performed using the former indirect analysis method.

In view of the above circumstances, an object of the present invention is to provide a simple and accurate method for quickly quantifying the total amount of oxygen, including oxides, suspended in molten steel by a direct method.

In the indirect analysis method described above, molten steel is pumped and solidified, this solid metal is melted in a high-temperature carbon crucible, and a reduction reaction C + O → using carbon (C) as a catalyst is performed.
The reaction product gas (CO) produced by CO can be measured and quantified using various methods, but the method of the present invention is characterized in that the CO reaction is directly produced in molten steel.

That is, the present invention includes a step of immersing a refractory probe with a carbonaceous material inside and an inert gas atmosphere in a molten metal to bring the carbonaceous material and the molten metal into contact in a pipe to generate carbon monoxide; The gist of this paper is a rapid analysis method for oxygen in molten steel, which consists of the steps of guiding the generated gas to a quantitative system, quantifying the amount of carbon monoxide, and then calculating the amount of oxygen.

For example, fibrous carbon is suitable as the carbonaceous material as the reaction medium. This carbon is filled into a refractory capsule, etc., and placed inside the opaque quartz tube of the probe. A small hole is provided at the tip of this reaction tube to allow molten steel to enter, and Ar or Helium gas is introduced into the tube with pre-controlled pressure and flow rate.
The inside of the pipe is maintained in an oxygen-free condition by supplying an inert gas such as Inert gas pressure 0.5 for this
~1.5Kg/ ^cm2 flow rate is 1-2/min. A carbon-filled probe is inserted mechanically or manually into the molten steel to be directly measured. Molten steel enters the tube through the small hole at the tip, and a CO reaction occurs when it comes into contact with carbon. The inert gas fed into the tube reduces the partial pressure of CO gas inside the reaction tube and promotes the CO reaction. The reaction product gas is sucked together with an inert gas by a gas sampling pump and sent to a quantitative analysis system. Quantitative analysis of the generated gas is performed, for example, by infrared absorption method.

FIG. 1 is a mechanical diagram of a probe including the above-mentioned CO reaction tube.

In the figure, reference numeral 1 denotes a reaction tube, which is made of, for example, an opaque quartz tube, and has a small diameter tube section 2 and a large diameter tube section 3 following the small diameter tube section. It has a small hole 4 through which molten steel is introduced.

The constricted portion serves as a reference line when the probe is immersed in molten steel, and is enlarged to prevent the molten metal from scattering into the subsequent large-diameter pipe portion during the CO reaction and block the small-diameter pipe portion.

Reference numeral 5 denotes a gripper made of a heat-resistant stainless steel tube, for example, and the base of the reaction tube 1 is attached to and removed from the tip of the gripper by means of connecting fittings 6a and 6b. That is, insert the base of the reaction tube 1 into the socket hole of the connecting fitting 6a that is screwed onto the grip tube side,
Fit the O-ring 7 around the ring-shaped connection fitting 6
By screwing b into the metal fitting 6a and tightening it, the reaction tube 1 is connected and fixed to the grip tube 5 in an airtight manner.

8 and 9 are stainless steel tubes with an inner diameter of 4 mm and an outer diameter of 6 mm, for example. The tube 8 extends and opens near the small diameter tube portion 2 of the reaction tube 1 into which the carbonaceous material is introduced, and an inert gas whose constant pressure is controlled in advance is fed into the reaction tube through the tube 8.

In the tube 9, a probe is inserted into the molten steel, and the molten steel enters the small diameter tube section 2 of the reaction tube 1, and carbon monoxide generated when it comes into contact with carbonaceous material is collected together with the inert gas sent from the tube 8. A sampling gas transport pipe for taking out to a sampling system outside the reaction tube opens near the base of the reaction tube 1.

FIG. 2 shows an inert gas supply system A that sends a fixed amount of inert gas at a constant pressure to the probe, a gas sampling system B that takes out carbon monoxide generated in the probe together with the inert gas sent, It is a flowchart showing an example of quantitative system C that quantitatively determines the amount of carbon monoxide in the sampled gas and displays the amount of oxygen in the steel.

The inert gas supply system A is equipped with pressure gauges P ₁ , P ₂ , a pressure regulating valve C ₁ , and a flow rate regulating valve C ₂ , and adjusts the inert gas from the Ar or He pump to a fixed amount and constant _pressure . , a dehydrating agent H, and an inert gas is sent out from the tube 8 of the probe via a flowmeter _F1 .

The gas sampling gas system B includes a sampling unit S that is equipped with a sampling pump and conveys the reaction product gas in the probe to the quantitative system C, a filter f ₂ that passes the sampling gas, and a drain pot that receives the moisture separated by the sampling unit. d. Consists of its drainage pot C ₄ .

The quantitative system C includes a CO meter M using an infrared absorption method to quantify the amount of CO in the sampling gas, a recorder K that monitors and records the measured value, and an integral that integrates the gas peak value obtained by the CO meter M. Display unit I and display unit P that prints its numerical value
The sampling gas conveyed from the sampling unit S is sent to the CO meter M via a flowmeter _F2 by a three-way valve _C5 . The generated CO gas sent is quantified by a CO meter M and recorded as a peak on a recording paper, and at the same time is integrated by area by an integrator I and digitally printed as a numerical value on a display section P. Note that B ₁ and B ₂ are standard gases for calibrating the CO meter M.

In order for the method of directly analyzing oxygen in molten steel of the present invention to be effective, it must be shown that there is a correlation between the molten steel oxygen value of this method and the gas analysis value of the solid material. Figure 3 shows this.

In this measurement example, atmospheric melting was performed in a 1-ton high-frequency furnace.
The amount of oxygen gas in the Fe-Ni alloy was measured using this method, and the values obtained by analyzing the oxygen from the solid material collected at the same time are also shown. The method of the present invention
This is the value obtained by converting the integrated value of the gas peak area into the amount of O ₂ per gram of molten steel reaction amount (horizontal axis), and the value of the solid data shows the total amount of oxygen in the solid metal in ppm according to the inert gas analysis method. (vertical axis). Although there are some variations between the two methods, including errors in the amount of reaction before the furnace, they show a generally good correlation, indicating that the present method has sufficient accuracy for practical use.

When relying on the conventional indirect method, it took about 30 minutes from sampling to obtain the results, which was too long, making it impossible to immediately feed back the results to on-site operations, but the present invention The oxygen content behavior can be quickly grasped in front of the furnace, and therefore, for example, the amount of deoxidizing agent input during tapping can be effectively adjusted.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the mechanism of a probe inserted into molten steel suitable for implementing this method. Figure 2 is an inert gas supply system A that delivers a fixed amount of inert gas to the probe at a constant pressure. Produced gas sampling system B
and a flowchart showing an example of a system C for quantifying carbon monoxide gas in a sampled gas. FIG. 3 is a chart comparing the oxygen value in molten steel obtained by this method with the gas analysis value obtained by the conventional inert gas blowing method. 1: reaction tube, 2: small diameter tube section, 3: large diameter tube section,
4: Small hole, 5: Grip, 6: Connection fitting, 7: O-ring, 8: Inert gas supply pipe, 9: Sampling gas transport pipe, A: Inert gas supply system, B: Gas sampling system , C: Carbon monoxide gas quantitative system, P ₁ ,
P ₂ : Pressure gauge, C ₁ : Pressure regulating valve, C ₂ : Flow regulating valve, f ₁ ,
f ₂ : Filter, Hs : Dehydrating agent, F ₁ , F ₂ : Flow meter,
S: Sampling unit, d: Drain pot,
M: CO meter, K: recorder, I: integrator,
P: Display, C ₃ , C ₄ : Kotoku, C ₅ : Three-way Kotoku,
B ₁ , B ₂ : Standard gas.

Claims (1)

[Claims] 1. A step of immersing a fire-resistant probe with a carbonaceous material inside and an inert gas atmosphere into molten metal to bring the carbonaceous material and molten metal into contact in the pipe to generate carbon monoxide; 1. A method for rapid analysis of oxygen in molten steel, comprising the steps of guiding the generated gas to a quantitative system, quantifying the amount of carbon monoxide, and calculating the amount of oxygen therefrom. 2. A reaction tube consisting of a small diameter tube section with a small hole at the tip and a large diameter tube section following the small diameter tube section is provided at its base so that it can be attached to and detached from the grip section using a connecting fitting, and the carbonaceous material is housed in the small diameter tube section. and an inert gas feed pipe that opens near the small diameter pipe portion of the reaction tube and feeds a fixed amount of inert gas at a constant pressure into the reaction tube;
A rapid analysis device for oxygen in molten steel, characterized in that the probe is equipped with a sampling gas take-off tube that opens into the reaction tube and carries generated gas to a gas sampling system, and is installed in airtight communication with the inside of the reaction tube.