JPS6146361A - Device for measuring thickness of molten layer of cc powder - Google Patents

Abstract

PURPOSE:To measure continuously the thickness of a molten powder layer with good accuracy without contacting by attaching a bar-shaped ray source and vertically movable gamma ray detector to the walls of a mold facing each other and disposing a device for measuring the level of a molten metal above the molten steel surface. CONSTITUTION:The bar-shaped gamma ray source 3 along the vertical direction is disposed to one mold wall 1 in continuous casting in proximity to the inside wall 4 and the gamma ray detector 5 is provided vertically movably by a moving device 7 to the other mold wall 2 in proximity to the inside wall 6. The relation between the quantity of the transmitted rays corresponding to the molten metallic layer A, molten powder layer B, powder grain layer C and air layer D and the moving position of the detector 5 is determined and is corrected by a level measuring device 9. The online measurement of the thickness of the layer B is thus executed. The continuous measurement of the thickness of the molten powder layer with good accuracy without contacting is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an apparatus for measuring the thickness of a molten liquid layer (powder molten layer) of powder introduced into a continuous casting mold.

(Prior art and its problems) In continuous casting equipment, measuring the thickness of the molten powder layer on the surface of molten steel is extremely important in order to produce high-quality slabs and prevent operational troubles such as breakouts. is important.

Conventional electrode-type powder molten layer measuring equipment measures the resistance value in each layer by lowering the probe into the moulme at a constant speed, and detects that the resistance value changes discontinuously as it passes through each layer. This method attempts to measure the molten powder layer by measuring the time interval when the discontinuity point passes using the conventional device.However, with this conventional device, measurements must be made intermittently.During the measurement Measurement errors due to fluctuations in the hot water level cannot be avoided.Since there is a tundish above the mold, it is difficult to install the probe and its vertical movement mechanism above the mold.Furthermore, instead of the electrodes mentioned above, Therefore, a measurement method using ultrasonic waves that takes advantage of the fact that in the molten powder region a characteristic waveform due to reflection on the molten steel surface is proposed has been proposed in Japanese Patent Laid-Open No. 57-56146. In addition to these problems, there are other problems such as adhesion of molten steel to measurement terminals or melting damage.

In addition, the temperature measuring powder fused layer measurement device uses the fact that iron wire melts in molten steel but remains unmelted in the powder fused layer, while copper wire melts in the molten steel and powder fused layer. The purpose is to measure the thickness of the molten powder layer by inserting a rod-shaped object wrapped around it into a mold, immersing it in the mold, taking it out after a few seconds, and measuring the difference in remaining length between the iron wire and the copper wire. However, this conventional device has no choice but to perform intermittent measurements.

Measurement errors that occur due to human measurements such as how to determine the immersion time related to the amount of erosion, reading errors, etc., and measurement errors due to fluctuations in the hot water level during measurement cannot be avoided. We were unable to avoid the problem of being exposed to danger when working above the mold.

(Object of the Invention) The present invention was devised in order to solve the above-mentioned conventional problems, and an object of the present invention is to enable non-contact and almost continuous measurement of the thickness of the molten powder layer with high accuracy. .

(Structure of the Invention) The powder molten layer thickness measuring device in the continuous casting mold of the present invention includes a bar-shaped gamma ray source disposed along the vertical direction on one side of the opposing mold wall, and a bar-shaped gamma ray source disposed on the other side of the mold wall. It is characterized by comprising a gamma ray detector arranged to be movable up and down and a hot water level measuring device.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 and 2 are opposing mold walls, and inside one mold wall 1, there is a rod-shaped gamma ray source 3 along the vertical direction that covers the fluctuation range of the powder molten layer B and the powder powder layer C. It is arranged close to the inner wall 4. Inside the other mold wall 2, a gamma ray detector, for example, a scintillation counter 5, is movable up and down by a moving device 7 in the fluctuation range of the powder particle layer A and the powder molten layer B close to the mold inner wall 6. Moreover, it is arranged so that its position can be detected by a movement distance detector 8 provided in the device 7.

Reference numeral 9 denotes a conventionally known microwave or laser light type hot water level measuring device, which is disposed above the hot water level 10 between the mold walls 1 and 2. The device 9 injects microwave or laser light toward the hot water surface 10, captures the reflected wave from the hot water surface 10, and detects the hot water surface based on the interference wave or incidence/reflection angle of the microwave or laser light. The structure is such that the level can be detected.

(Function) The γ-rays emitted from the γ-ray source 3 pass through the molten metal layer A1 powder molten layer B1 powder particle layer C1 air layer and reach the scintillation counter 5, where the intensity thereof is detected. On the other hand, the position of the scintillation counter 5 is detected by a moving distance detector 8.

J, average distance from the two sources to the detector (crn) Si/
1: Area of each layer in the total area S1: Build-up coefficient in each layer μm: Linear absorption coefficient in each layer ′ (Ol): Expressed in source unit capacity (CVcIn).

The linear absorption coefficient μ of each layer is 0 in the case of molten steel in molten metal layer A.
．． 46. Since the transmission ratio of γ rays is different in each layer: 0.141 in the powder fusion layer B, 0.064 in the powder particle layer C, and almost O in the air layer, the scintillation counter 5 is lowered from the origin O. The relationship curve between the γ-ray intensity output and the detector position obtained by
, b, and c correspond to each other.

Therefore, if the above-mentioned relationship curve is obtained, it is possible to distinguish each layer and calculate the thickness of each layer based on the positions a, b, and c corresponding to the inflection points.

In reality, since there are fluctuations in the hot water level, the hot water level measurement device 9 measures the fluctuations in the hot water level 10 (the surface of the powder layer C) in parallel with the measurement of the gamma rays and the detector position. Then, it is necessary to correct the detector position so that the origin 0 of the detector position is aligned. The relationship curve is determined for the corrected detector position.

According to experiments, the above measurement work could be carried out almost continuously with a period of about 5 seconds at the shortest.

Moreover, the measurement accuracy was improved compared to the conventional powder fused layer measuring device using iron wire and copper wire, and the accuracy was confirmed to be within ±1 m8.

In this embodiment, the hot water level measuring device was of the microwave or laser type, but may be of an optical type using a TV.

(Effects of the Invention) As described above, the present invention makes effective use of the fact that the transmission ratio of gamma rays is different between the molten metal, the powder melt layer, the powder particle layer, and the air layer, so that the gamma ray detector can be moved in the vertical direction. The correlation between the position and the amount of gamma ray transmission (intensity) is determined while moving the powder, and the correlation is corrected based on the level of the molten metal. , online measurement is possible because it can be measured with high accuracy. When the thickness of the molten powder layer is thin, it is possible to reduce the casting speed to prevent breakouts caused by film breakage, and to control the powder supply amount reliably and quickly, increasing the yield of high-quality slabs. Can be manufactured well.

In addition, unlike the electrode type and ultrasonic type, there is no interference between the measuring device and the operator on the upper surface of the mold, making it a highly practical measuring device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the area ratio of each layer, and FIG. 3 is a diagram showing a relationship curve between detector position and γ-ray intensity. 1.2... Mold wall, 3... Gamma ray source, 4, 6... Mold inner wall, 5... Scintillation counter, 7... Moving device, 8... Moving distance detector, 9... Hot water level Measuring device, 1o... Hot water surface, A... Molten metal layer, B... Powder molten layer, C... Powder particle layer, D... Air layer, a, b
,c...Layer boundary position. Figure 1 Prisoner 2 Figure 3

Claims (1)

[Claims] A bar-shaped gamma ray source disposed along the vertical direction on one side of the opposing mold wall, a gamma ray detector disposed vertically movably on the other side of the mold wall, and a hot water level measuring device. A CC powder melt layer thickness measuring device characterized by the following.