JP2007291435A - Method for measuring refractory profile in converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the profile of a high temperature refractory with high accuracy without being affected by dust etc., when the profile is measured by using a non-contacting type range finder utilizing a light wave, such as laser beam. <P>SOLUTION: When the profile of a converter refractory is measured by using the non-contacting type range finder utilizing the light wave, the dust density is lowered by blowing gas at the gas-flowing rate of ≥10% of the furnace volume per unit time from a tuyere at the furnace bottom after tapping molten steel and removing slag from the converter and successively, the above profile is measured by using the non-contacting type range finder set at the front position of the furnace opening hole in the converter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring a profile of a refractory for a converter with high accuracy using a non-contact distance meter using a light wave such as a laser.

  Although the refractories stretched inside the converter are gradually eroded by molten steel, they are not necessarily uniformly damaged, they do not get rid of local damage, and such parts are generally used while being repaired. Is. Therefore, it is necessary to diagnose the deterioration status of the refractory in order to grasp the repair time and the replacement time of the refractory. Conventionally, there is a device that measures a refractory profile while bringing a contact sensor into contact with the inner wall of a refractory container.

  On the other hand, using a non-contact distance meter, a light wave distance meter as shown in Patent Document 1 is inserted inside the refractory container, and the distance from the vicinity of the refractory to the refractory is measured. Some measured the refractory profile.

However, even with a non-contact sensor such as Patent Document 1, the refractory profile cannot be measured unless the temperature of the refractory in the converter is lowered to some extent, and the temperature of the refractory is high as in the converter. When dust or the like remains inside the converter after steelmaking, there is a problem that the measurement error increases due to the dust or the like becoming noise.
JP 60-138407 A

  Therefore, when measuring the profile of a high-temperature converter refractory using a non-contact distance meter using light waves such as a laser, the present invention can perform measurement with high accuracy without being affected by dust or the like. The problem is to do so.

The gist of the present invention made to solve the above problems is as follows.
(1) When measuring the profile of the converter refractory using a non-contact distance meter, the molten steel is removed from the converter, and after it is discharged, the furnace bottom has a volume of 10% or more of the furnace volume per unit time. A converter characterized in that gas is blown at a gas flow rate to reduce the dust concentration in the furnace, and then the profile is measured using a non-contact distance meter using light waves installed at a position in front of the furnace port of the converter. Refractory profile measurement method.
(2) The converter refractory profile measuring method according to (1), wherein the total amount of gas blown from the furnace bottom tuyere is 1.2 times or more of the furnace internal capacity.

  According to the present invention, it is possible to measure the profile of a high-temperature refractory with high accuracy even if dust or the like remains after steel output as in a converter.

Hereinafter, the present invention will be described by taking as an example the case of using a laser distance meter as a non-contact distance meter utilizing light waves.
In the top-bottom blown converter, a cold iron source such as scrap and hot metal are charged into the converter, and then agitation gas is blown from the furnace bottom while blowing oxygen using a lance, and carbon is burned to achieve a predetermined component and temperature. Molten steel is discharged and slag remaining in the furnace is also removed. Therefore, a lot of dust remains in the furnace immediately after evacuation, so that the laser emitted from the laser rangefinder is scattered and the intensity of the reflected laser after collision with the furnace wall decreases, resulting in a measurement error. Has become larger or impossible to measure.

In the past, it was better to leave it for a while until the dust settled, but the longer it took, the longer the non-operation time of the converter, the lower the operation rate, and the temperature of the refractory of the converter As a result, the temperature deviation of the converter refractory increases in the hot metal receiving during the next converter blowing, which may adversely affect the refractory.
Therefore, the present inventors diligently studied a method for discharging dust. As a result, we have found that if the gas blown from the bottom of the furnace is used to discharge dust from the furnace port, the measurement can be performed accurately with minimal influence of dust.

FIG. 1 shows a 370 ton converter (furnace capacity: 320 m ³ ) and three levels of gas injection flow rate per unit time from the furnace bottom (25 Nm ³ / min: 8% of the furnace volume, 32 Nm ³ / min: furnace volume 10%, 70 Nm ³ / min: 22% of the furnace volume), and by changing the blowing time, the results of the investigation of the occurrence rate of measurement defects in the converters (rates that could not be measured at all) by each laser distance meter Is shown. As can be seen from FIG. 1, the defect occurrence rate gradually decreases as the flow rate of the blown gas per unit time increases.

This is considered to be because the gas blown from the bottom of the furnace causes the dust in the furnace to be discharged from the furnace port, thereby reducing the influence of the dust on the laser distance meter. In particular, when the blowing time was increased at less than 32 Nm ³ / min, the defect occurrence rate did not decrease easily, but at 32 Nm ³ / min or more, the behavior was clearly different, and it took less time from the start of gas blowing. It has been found that it is about 5% or less, which is an acceptable defect occurrence rate that does not cause trouble without causing a major trouble during the refining preparation time and operation of the actual machine.

Even if it is less than 32 Nm ³ / min, that is, less than 10% of the furnace volume, although there is an effect of reducing the defect occurrence rate, there is a reason that the elapsed time until the defect occurrence rate reaches 5% or less at 32 Nm ³ / min or more can be significantly shortened. It is thought that there is a suppression of the heat effect generated from bricks and slag in the furnace.
Generally, the brick temperature in the furnace after the converter steel is a high temperature of 1300 to 1600 ° C. although there are differences depending on the temperature of the molten steel and the material of the brick. Therefore, a heat flux corresponding to the brick temperature is generated from the brick that has become high temperature mainly due to the influence of radiation. For this reason, the dust generated in the furnace floats and causes the above-mentioned measurement obstacles. If the influence of radiant heat, which is the main cause of floating dust, can be reduced in addition to the above-mentioned discharge of dust to the outside of the furnace when gas is blown, the defect occurrence rate will quickly reach 5% or less. Connected.

Therefore, as shown in FIG. 1, when the gas flow rate from the furnace bottom is set to 32 Nm ³ / min or more, it has a cooling capability to overcome the heat flux generated from the furnace, and the dust concentration in the furnace can be measured. It is presumed that it was able to be reduced stably and in a short time to the point where there was no. In addition, it is speculated that light waves such as lasers are likely to be irregularly reflected and prone to measurement failure when the measurement surface has a rough surface with little irregularities. It is presumed that there is also an effect of improving the wall surface close to the mirror surface by cooling the adhered inner wall surface of the furnace and solidifying the adhered liquid slag.

Further, from FIG. 1, since the measurement failure occurrence rate decreases with time, it can be estimated that the total gas amount is also effective in reducing the measurement failure occurrence rate. Therefore, in order to determine the influence of the total amount of gas injected, the product was arranged by the product of the gas injection flow rate V per unit time from the furnace bottom and the time T. FIG. 2 shows that the gas flow rate from the furnace bottom is set at two levels of 32 Nm ³ / min and 70 Nm ³ / min (corresponding to 10% and 22% of the furnace volume, respectively), and the total gas amount (total blown gas amount) The result of investigating the relationship with the measurement defect occurrence rate is shown.

From FIG. 2, it was confirmed that even when the gas flow rate V changes, the total gas amount (product of the gas blowing flow rate V and time T) and the defect occurrence rate decrease with substantially the same tendency. And in the region where the total amount of gas blown is 1.2 times or more of the converter furnace volume W (320 m ^{3 in} the case of the present 370 ton converter), it is found that the defect occurrence rate is stable to 5% or less of the standard. It was. In other words, if the gas is blown and replaced by 1.2 times or more of the furnace volume, the influence of dust, which becomes a measurement error of the distance meter, can be greatly suppressed.

  However, if the total gas amount is 1.2 times or more of the furnace volume, the failure rate will be 5% or less of the standard. However, even if the total gas amount is increased to 1.5 times or more of the furnace volume, the failure rate will be reduced. There is no significant improvement, and conversely, the refractory temperature in the furnace decreases as the amount of blown gas increases, so there is a possibility that the temperature drop in the next blowing will be too great and damage to the refractory will increase. For this reason, it is desirable that the total gas amount be 1.5 times or less the furnace volume.

  In addition, although the case where the laser distance meter was used was described above, it is not necessary to limit to this, and other non-contact type distance meters such as a light wave distance meter and an ultrasonic distance meter also generate errors due to the influence of dust. It is known that if the gas replacement is performed under the same conditions, the same effect is considered.

Each level of the profile of the refractory in the converter was measured 40 times using a laser distance meter from the front of the furnace port after steel blowing and discharge after blowing. At that time, the measurement was performed by varying the flow rate V of gas blown from the furnace bottom and the measurement start timing after the discharge.
Table 1 shows the gas blowing and measurement timing conditions and the measurement results. As the blowing gas, nitrogen gas was used so as not to cause an oxidation reaction.

No. using a 370 ton converter (volume 320 m ³ ). 1-No. No. 2 is an example in which gas blowing from the furnace bottom is a condition within the scope of the present invention, the number of occurrences of measurement failures was at most once, and the failure occurrence rate was as low as 5% or less. . In particular, No. 1 under the condition that the total gas amount (gas flow rate x time) is 1.2 times or more of the furnace volume. 3-No. In No. 6, no measurement failure occurred. However, NO. No. 6 is a NO. With total gas volume (gas flow rate x time) exceeding 1.5 times the furnace volume. For No. 6, the hot metal temperature drop was larger than other conditions. Furthermore, the same measurement was performed using a 180 ton converter (volume 150 m ³ ). 7 and NO. However, the failure occurrence rate is 5% or less, and, as in the case of the 370t converter, the total gas amount is 1.2 times or more of the furnace volume. In No. 8, no measurement failure occurred.

On the other hand, no. No. 9 had a gas flow rate of less than 32 Nm ³ / min in a 370 t converter, that is, 10% or less of the furnace volume, so that many measurement failures occurred and the occurrence rate exceeded 5%. This is a NO. 10 is the same. NO. No. 11 has a gas flow rate of 25 Nm ³ / min or less in a 370 t converter, and the total gas amount was increased to 45 minutes, but the defect occurrence rate was No. 11. Although it was lower than 9, it was not less than 5%, and conversely, the total gas amount increased, so the hot metal temperature drop of the next blowing was increased.

  As described above, under the gas blowing conditions of the present invention, it was confirmed that the measurement failure occurrence rate when measuring using a non-contact distance meter utilizing light waves was 5% or less of the reference.

The figure showing the gas blowing time from a furnace bottom, and a measurement defect incidence. The figure showing the product of the gas blowing speed from a furnace bottom, time, and a measurement defect occurrence rate.

Claims (2)

  When measuring the profile of the converter refractory using a non-contact distance meter using light waves, the molten steel is removed from the converter and discharged. A converter refractory profile characterized in that gas is blown at a gas flow rate to reduce the dust concentration in the furnace, and then the profile is measured using a non-contact distance meter installed at a position in front of the furnace port of the converter. Measuring method.   2. The converter refractory profile measuring method according to claim 1, wherein the total amount of gas blown from the furnace bottom tuyere is 1.2 times or more of the furnace capacity.

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