JPS59138956A - Quantitative determination of hydrogen in molten metal - Google Patents

Abstract

PURPOSE:To eliminate an error in measurement by coating a release agent on the outside wall of a sampling vessel, dipping the same in a molten metal to sample the molten metal and putting the vessel in a gas capturing vessel and rupturing the vessel. CONSTITUTION:A release agent which prevents sticking of slag and molten steel is coated on the outside wall of a sampling vessel 1 of an internal capturing type of hydrogen by vacuum suction and release and is dried and thereafter the vessel is dipped in the molten steel. The top end 3 thereof is corroded by the molten steel, then the molten steel is sucked in the vessel to fill a conduit 2 and arrives at a chiller 10, thus closing a vent hole 11 and soldifying. The hydrogen to be released in the stage of cooling on solidifying is captured in a vacuum chamber 4. The sampling vessel right after the sampling is put into a capturing vessel 6 with a rupturing mechanism which is then closed hermetically with a cover 12 and the inside thereof is evacuated to vacuum or substd. with gas for carrier. The sampling vessel is ruptured to release hydrogen into the capturing vessel. The hydrogen is quantitatively determined with a mass spectrograph or a heat conductivity detector with a gas chromatograph.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining the amount of hydrogen in molten metal.

In steelmaking and aluminum smelting, it is important to reduce the amount of hydrogen in molten metal as much as possible in order to improve the mechanical properties of the final product. Molten metal (hereinafter referred to as molten metal)
Conventionally, to quantify the amount of hydrogen in the molten metal, it is necessary to suck it up directly from the molten metal or after pumping it up in a quartz tube, quench it with water, and then store it immediately or in dry ice or liquid nitrogen before making it into a specified size. After cutting and polishing, it is generally quantified by melting in an inert gas-gas chromatography separation-thermal conductivity detection method.

However, (1) the solubility of hydrogen drastically decreases when the molten metal solidifies, so a large amount of hydrogen is released into the atmosphere during solidification of the sample and cannot be quantified; and (2) hydrogen is supersaturated at room temperature after solidification. Therefore, it is difficult to accurately quantify the amount of hydrogen in the molten metal using the above-mentioned method because hydrogen also dissipates during preparation for analysis such as cutting and polishing the sample.

Several proposals have been made to solve these difficulties. The first method involves sucking up the molten metal into a vacuum quartz tube filled with thin-walled cylindrical stainless steel, allowing the hydrogen released during solidification to be absorbed into the stainless steel, which has a high hydrogen solubility, and then cutting the sample along with the stainless steel cylinder. It is used for quantitative determination (Narita Sei, "Tetsu to Hagane", 1979. p1620)
. However, when this method is used, a fine gap is created at the boundary between the solidified metal and the stainless steel cylinder, and water that enters the gap during water cooling decomposes and generates hydrogen when melting the sample for analysis, causing errors. In addition, the stainless steel cylinder to be inserted must be completely dehydrogenated beforehand, otherwise the error will become large.

As shown in Fig. 1, a conduit 2 for solidifying molten steel into a certain rod shape is placed inside a pongee pipe 1 made of a thin steel plate, and the tip 3 sealed in a vacuum is immersed in the molten steel. After the molten steel is sucked into the molten steel 2, it is slowly cooled to completely release the hydrogen in the molten steel and collected in the vacuum chamber 4, and then, as shown in FIG. Sample collection container 7 in 6
The amount of hydrogen is determined by measuring the hydrogen collected by perforating the pongee pipe section 1 using the thermal conductivity detection method, and dividing the amount by the amount of molten metal drawn into the pipe section 2 (Special Publications Publication No. 1973). -451.57). This method prevents the hydrogen released during solidification from escaping, and also eliminates the need for cutting and polishing the sample, thereby preventing errors caused by hydrogen dissipation during cutting and polishing. However, this proposal still has some drawbacks.

That is, most of the molten metal in the sample collection container 7 is in the conduit section 2.
Normally, a suction base 8 is not provided to prevent the molten metal from being sucked up through the pongee pipe and being sucked up between the pongee pipe part 1 and the conduit part 2. It is made so as to close the path leading to the middle of the section 1 and the conduit section 2. However, if the hydrogen released from this part is added to the hydrogen released from the conduit section 2, an error will occur, so as shown in FIG. It is necessary to seal so that only the hydrogen in section 2 can be measured, but molten steel and slag adhere to the outer periphery near the tip, making the sealing at seal section 9 incomplete, causing hydrogen to escape and resulting in low values. It may become.

In addition, there is a possibility that the hydrogen released when the molten metal sucked into the suction base 8 solidifies is collected in the vacuum chamber 4 together with the hydrogen released from the molten metal in the conduit section 2, resulting in a high error. There is also. Furthermore, there is a fear that hydrogen may not be completely released just by collecting a sample and slowly cooling it. As a countermeasure against this, if the entire collection container 7 is heated, a portion of the hydrogen in the molten metal that is sucked into the suction base 8 as well as the conduit portion 2 and solidified is released into the interior, resulting in a high temperature. therefore,
After quantifying the hydrogen released during solidification collected in the vacuum chamber 4, it is necessary to cut the sample collection container 7, take out only the sample in the conduit portion 2, and heat it to completely extract the hydrogen.

The present invention has been made regarding a sample collection method and a quantitative method in order to solve the above-mentioned problems in the method of quantifying the amount of hydrogen in molten metal. A part of the container is melted down, and a certain part of the container is sucked in and solidified, and the hydrogen released during solidification is collected in the internal vacuum space and quantitatively determined.A mold release agent is applied to the outer wall of the collection container and melted. This invention relates to a method for quantifying the amount of hydrogen in molten metal, which prevents the adhesion of metal and slag and is characterized in that the container is placed in a gas collection container that is isolated from the outside air and then ruptured.

The present invention will be explained in detail below. First, a mold release agent made of BN, graphite, etc., to prevent slag and molten steel from adhering to the outer wall of a general vacuum suction/release hydrogen internal collection type sample collection container as shown in Figure 3 is applied. smear. After drying, scrape off the slag on the molten steel and immerse it in the molten steel. The tip 3 is eroded by the molten steel, and the molten steel is sucked in and fills the conduit 2 made of a thin steel plate that has been previously dehydrogenated, reaches the previously dehydrogenated chiller 10, closes the vent hole 11, and solidifies. . Hydrogen released during solidification and cooling is collected in the vacuum chamber 4 either directly as a gas or by diffusion in the thickness direction of the conduit 2. Immediately after collection, the collection container is placed in a collection container 6 with a breaking mechanism as shown in Fig. 4, sealed with a lid 12, and the inside is replaced with carrier gas or evacuated, and then placed inside the collection container isolated from outside air. The collection container 7 is ruptured to release the hydrogen in the vacuum chamber, and the hydrogen inside is released into the collection container 6. Further, if necessary, the sample is heated to release residual hydrogen in the sample. The released hydrogen is quantified by a mass spectrometer directly by opening and closing the valve of the collection vessel or by being transported by a carrier gas and quantified by an analyzer such as a gas chromatograph-thermal conductivity detector.

In the above quantitative operation, by preventing the adhesion of molten steel and slag by the mold release agent, which is the first feature of the present invention, hydrogen escape at the sealing part of the collection container as shown in Fig. 2 is prevented. Ru. In addition, since there is no external adhesion, hydrogen release from external adhesion can be ignored, and the second feature is that it is possible to break the collection container by placing it in a collection container that is cut off from the outside air, reducing the possibility of hydrogen leakage. Completely prevented.

In addition, with the above improvements, it is possible to reheat the entire sample collection tube 7 (4ζ) to increase the hydrogen extraction rate and improve the accuracy and precision of quantitative determination. It is necessary to confirm that the hydrogen in the molten steel does not change by reacting with the slag.

Next, the present invention will be explained more specifically using examples.

Example A sampling container shaped as shown in Fig. 3 (however, the outside is entirely made of quartz, with an outer diameter of 12 mm, an inner diameter of 10 mm, and a length of 150 mm; the inside is made of dehydrogenated cold-rolled thin steel plate with a plate thickness of Q, 3 mm; A conduit with a diameter of 6 rrm and a length of 70 mm and a suction base made of mild steel, which was also dehydrogenated, were coated with fine powdered BN as a mold release agent using an aerosol spray, and dried. Jxs 5S41 in casting mold
Two samples were taken from molten steel of comparable composition. Immediately, without cooling, each sample was placed in a three-cylinder stainless steel collection container 6 (shown in FIG. 4) preheated to 700°C with a heater 16, as shown in FIG. After connecting the thermal conductivity detection type gas analyzer 5 and replacing the inside of each collection container 6 with Ar gas, the valve 1
The quartz container was broken with No. 7 closed. Next, by opening and closing the valve 17 and the three-way valve 18, the hydrogen in the collection container was transported to the gas chromatograph 5 using Ar carrier gas, and was quantified by thermal conductivity detection. The molten metal was collected in a separately prepared collection container of the same shape, and the sample weight was determined from the change in weight before and after, and this was used to determine the amount of hydrogen per unit weight. For comparison, two samples were simultaneously collected using a dropper suction type quartz tube using the conventional method, immediately cooled with water, cut, polished, and weighed. Quantitated. The results are shown in Table 1.

Table 1 Hydrogen analysis values obtained by the method of the present invention (unit: pPm) As is clear from Table 1, the conventional method shows a much lower value than the method of the present invention, and this is due to the dissipation of hydrogen released during solidification and the dissipation of hydrogen during cutting and polishing. This is thought to be due to hydrogen dissipation. Furthermore, reproducibility is poor due to variations in these factors. Since the method of the present invention solves these problems, the quantitative values are accurate and have good accuracy.

In addition, one end of a quartz tube with an outer diameter of 12 cm was sealed, and the outer wall was coated with BN or graphite as a mold release agent using an aerosol, and the tube was immersed in molten steel to examine its effectiveness in preventing molten steel and slag from adhering to the outer wall. The results are shown in Table 2.

Table 2 Mold Release Agent Effect Confirmation Test As is clear from Table 2, by applying a mold release agent, adhesion of molten steel and slag can be completely prevented.

That is, by using a mold release agent to prevent the adhesion of the outer wall -\, a quantitative method that yields the good results shown in Table 1 has become possible.

The present invention has been described in detail through examples above, but the type of mold release agent and application method are not limited to those shown in the examples. A substance that has the effect of preventing adhesion to the outer wall of the collection container and does not serve as a hydrogen source may be dispersed in an aqueous solution or organic solvent and applied, or a tingling film may be formed by aerosol, vapor deposition, etc. Regarding the collection container, in the example, a quartz suction base member is shown, but the outer tube may be made of metal, and the shape of the suction base and conduit portion may be changed in any way. It is valid even if the Furthermore, if the sample weight at the suction base is negligible compared to the sample weight at the conduit section, the heating operation shown in the example can be omitted. Furthermore, regarding the collection container and the gas analysis method,
Although one embodiment example for embodying the method of the present invention has been shown, correct values may be obtained in other embodiments within the scope of the present invention, such as using mass spectrometry instead of gas chromatography-thermal conductivity detection method. Needless to say, can be obtained with high accuracy.

As described above, according to the present invention, it is possible to solve the difficulties of conventional methods in quantifying the amount of hydrogen in molten metal, obtain accurate and accurate results, and greatly contribute to the prevention of hydrogen embrittlement of metal materials. It is.

[Brief explanation of drawings]

Figure 1 is an example of a sample collection container, and Figure 2 is an explanation showing the relationship between the sample collection container, a collection container for quantifying collected hydrogen, and a gas analyzer in one embodiment of the conventional quantitative method. Figure 3 is an explanatory diagram of a general vacuum suction-released hydrogen internal collection type sample collection container, Figure 4 is an explanatory diagram of a rupture type collection container, and Figure 5 is an illustration of the collection container and gas analyzer. It is a connection explanatory diagram. 1... Thin (steel) pipe, 2 Conduit, 3... Tip,
4... Vacuum chamber, 5... Gas analyzer, 6...
- Collection container, 7... Sample collection container, 8... Sucking base, 9... Seal part, ]O... Chilled gold, Moon...
Ventilation hole, 12... Lid, ] 3... Blade, 14... Bellows, 15... Drive screw, 16... Heater 1,
17... Valve, 18... Three-way valve Patent attorney Patent attorney Tomoyuki Yafuki (1 idiot) Figure 1 Figure 2 Whistle 3 Figure 4 Figure 7 Figure 5

Claims (1)

[Claims] A collection container that has been evacuated in advance is immersed in molten metal to melt a portion of the container, which is then sucked into a certain space inside to solidify, and the hydrogen released during solidification is collected in the internal vacuum space and quantified. In this process, a release agent is applied to the outer wall of the collection container to prevent the adhesion of molten metal and slag, and the container is placed in a gas collection container that is shut off from the outside air to break the molten metal. Method for quantifying hydrogen amount.