JPS6324261B2 - - 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 carbon dissolved in molten steel in a melting furnace or ladle at a steelmaking site. It is.

In general, carbon is added in an appropriate amount to steel to improve its mechanical, electrical, and other material properties, and is also used as a deoxidizing agent to clean molten steel. It has a great effect on deoxidizing, and is extremely effective as a deoxidizing method that does not produce solid inclusions in the molten metal, especially when used as a deoxidizing agent. If the amount of carbon 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 carbon in steel: an indirect measurement method in which molten steel is drawn from a melting furnace or a ladle, the sample is prepared and analyzed, and a thermocouple sensor is directly immersed in the molten steel to measure its thermoelectromotive force. There is a direct measurement method such as measuring .

The former is the most widely used method, and various methods have been developed, such as the gravimetric method and conductivity method, which are old chemical methods, and the infrared absorption method recently, and the accuracy is high and the time required for analysis has recently been reduced to 2 minutes or less. The speed has improved to 1 minute, and it has become widely established as a control analysis method in the steel manufacturing field.Although these methods can perform the analysis themselves quickly, they all require the preparation of a sample from solid metal. Because it takes time and effort to prepare analysis samples, including sampling, it is necessary to feed back the analysis results to the work site.
It has not yet reached the point where immediate and effective action can be taken.

The latter method, which directly measures carbon in molten steel, is preferable because it allows for quick feedback to the work site, but the measurement method using thermoelectromotive force using a thermocouple sensor requires that the molten metal be measured directly from the melting furnace or ladle. This is a method to indirectly determine the carbon content from the solidification temperature (freezing point) from the solidification curve of the molten metal that is pumped out, but there are still problems with operability and accuracy, and the total carbon content in steel cannot be measured unless the former indirect measurement method is used. The current situation is that this is not the case.

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 carbon, including carbides, suspended in molten steel by a direct method.

This method is characterized by utilizing the reverse reaction of the CO reaction (C+O→CO), which is generally applied to oxygen analysis in steel, and allowing this reaction to occur directly in molten steel.

That is, the present invention is a process of immersing a refractory probe containing an oxygen substance and creating an inert gas atmosphere into a molten metal, and bringing the oxygen substance and the molten metal into contact in a pipe to generate carbon monoxide and carbon dioxide. The gist of the present invention is a rapid analysis method for carbon in molten steel, which comprises the following steps: guiding the generated gas to a quantitative system to quantify the amount of carbon monoxide and carbon dioxide, and calculating the amount of carbon from them.

Oxygen substances as reaction media are suitable, for example, oxides such as copper oxide (CuO) or iron oxide (FeO). This oxide is filled into a refractory capsule, etc., and placed inside an opaque quartz tube of a probe. A small hole is provided at the tip of the reaction tube to allow molten steel to enter, and an inert gas such as Ar or He whose pressure and flow rate are controlled in advance is fed into the tube. Inert gas pressure is 0.5~
1.5Kg/cm ² , and the flow rate is 1 to 2/min. The probe containing the oxide is inserted mechanically or manually into the molten steel to be measured directly. Molten steel enters the tube through a small hole at the tip, and a CO reaction occurs when it comes into contact with oxides. 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 having an inner diameter of 4 mmφ and an outer diameter of 6 mmφ, for example. The tube 8 extends and opens near the small diameter tube section 2 of the reaction tube 1 into which the oxygen substance is introduced, and an inert gas whose constant pressure is controlled in advance is sent into the reaction tube through the tube 8.

In the tube 9, a probe is inserted into the molten steel, the molten steel enters the small diameter tube section 2 of the reaction tube 1, and the carbon monoxide and carbon dioxide generated when it comes into contact with oxygenous substances are removed from the molten steel fed through the tube 8. This is a sampling gas transport pipe for taking out the active gas together with the sampling system outside the reaction tube, and opens near the base of the reaction tube 1.

Figure 2 shows an inert gas supply system A that sends a fixed amount of inert gas at a constant pressure to the probe, and a gas that takes out carbon monoxide and carbon dioxide generated in the probe together with the inert gas sent. It is a flowchart showing an example of a sampling system B and a quantitative system C that quantitatively determines the amount of carbon monoxide and carbon dioxide in the sampled gas and displays the amount of carbon in 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 regulating valve C ₂ , and adjusts the inert gas from the Ar or He cylinder to a fixed amount and constant pressure, and a filter f _{1 .} , 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 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 d that receives the moisture separated by the sampling unit. , its draining liquid consists of C ₄ .

The quantitative system C includes a CO and CO ₂ meter M using, for example, an infrared absorption method to quantify the amount of CO and CO ₂ in the sampling gas, a recorder K that monitors and records the measured values, and a CO and CO ₂ meter M. The sampling unit S is equipped with an integrator I that integrates the gas peak value obtained, a display P that prints the value, etc., and the sampling gas conveyed from the sampling unit S is passed through a flowmeter F ₂ by a three-way valve C ₅ and then sent to CO2.
and sent to CO ₂ meter M. The sent generated gas is quantified by a CO and CO ₂ 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 CO and CO ₂ meters M.

In order for the direct analysis method of carbon in molten steel of the present invention to be effective, it must be shown that there is a correlation between the molten steel carbon value of this method and the carbon analysis value of solid materials, but the relationship between the two is Figure 3 shows this.

In this measurement example, atmospheric melting was performed in a 1-ton high-frequency furnace.
The amount of carbon gas in the Fe-Ni alloy was measured using this method, and the values obtained by analyzing the carbon from the solid material collected at the same time are also shown. The method of the present invention uses CO,
It is a value obtained by converting the sum of the integral values of the peak areas of CO ₂ gas into the amount of C per 1 g of molten steel reaction amount (horizontal axis),
The numerical value of the solid data is the amount of carbon in the solid metal expressed in % by inert gas analysis method (vertical axis).
Although there is some variation between both methods, including errors in the amount of reaction in front of the furnace, they show a generally good correlation.
This shows that this method has sufficient accuracy for practical use.

When using the conventional indirect method, it takes about 30 minutes from sampling to obtain the results, making it impossible to immediately feed back the results to on-site operations. The carbon content behavior of the steel can be quickly grasped before the furnace, and therefore, for example, the carbon content can be effectively adjusted during tapping.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the mechanism of a probe inserted into molten steel suitable for implementing this method. Figure 2 shows an inert gas supply system A that delivers a fixed amount of inert gas at a constant pressure to the probe, and a generated gas sampling system B in the probe.
and a flowchart showing an example of a system C for quantifying carbon monoxide gas and carbon dioxide gas sampled. FIG. 3 is a chart comparing the carbon 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...Gripping part, 6...Connection fitting, 7...O ring, 8...Inertness gas supply pipe,
9... Sampling gas transport pipe, A... Inert gas supply system, B... Gas sampling system, C... Carbon monoxide gas, carbon dioxide gas quantitative system, P ₁ , P ₂
……Pressure gauge, C ₁ ……Pressure regulating valve, C ₂ ……Flow rate regulating valve,
f ₁ , f ₂ ... Filter, H ... Dehydrating agent, F ₁ , F ₂ ...
...Flowmeter, S...Sampling unit, d...
Drain pot, M...CO and CO ₂ meter,
K... Recorder, I... Integrator, P... Display,
C ₃ , C ₄ ... Kotsuku, C ₅ ... Mikata Kotsuku, B ₁ , B ₂
...Standard gas, In...Inert gas cylinder.

Claims (1)

[Scope of Claims] 1. A fire-resistant probe containing an oxygen substance and an inert gas atmosphere is immersed in molten metal to bring the oxygen substance and molten metal into contact within the pipe to generate carbon monoxide and carbon dioxide. 1. A method for rapid analysis of carbon in molten steel, comprising: a step of introducing the generated gas into a quantitative system to quantify the amount of carbon monoxide and carbon dioxide, and calculating the amount of carbon 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 part using a connecting fitting, and the oxygenous substance is stored 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 carbon in molten steel, characterized in that it is equipped with a probe having 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.