JP4285372B2 - Method for cutting continuous cast slab to remove splash - Google Patents

Description

  The present invention relates to a method for cutting a slab that can remove the splash that occurs when a slab is cut by a torch in manufacturing a slab by continuous casting and remains on the slab surface. More specifically, the present invention relates to a simple and inexpensive method for cutting a continuous cast slab for preventing surface flaws from being generated in a plate making process due to splash remaining on the upper surface of a slab.

  When the splash generated when the hot slab cast by continuous casting is gas-cut adheres to the upper surface of the slab and remains, wrinkles are generated on the surface of the steel sheet in the hot rolling and cold rolling processes.

  FIG. 1 is a view showing a cold-rolled steel photograph of a cold-rolled steel sheet generated due to a foreign substance on the slab surface. As seen in the figure, streaky cold rolled steel is generated on the surface of the steel sheet, leading to a downgrade of the cold rolled steel sheet product.

  Therefore, foreign matter such as splash remaining on the surface of the slab needs to be removed before the plate making process. Conventionally, foreign matter that occurs when the slab is cut and remains on the surface of the slab has Or by mechanical treatment with a grinder.

  The removal by the scarf care described above causes an increase in the removal cost due to an increase in the number of scarf man-hours. In the case of mechanical removal by a grinder, a large removal facility is required. Further, in any case, it is necessary to take a measure for removing foreign matters in the slab after cooling, and therefore it is impossible to avoid a thermal energy loss, an increase in physical distribution cost, and a lead time loss based on this.

  As a method for removing high-temperature slab surface defects, for example, there are methods disclosed in Patent Document 1, Patent Document 2, and the like.

  In the above-mentioned Patent Document 1, the surface of the hot piece slab after the partial rolling and the cross-sectional defect wrinkles are partially removed by relatively large wrinkles, and the remaining wrinkles are then removed by a hot entire surface scarfing device. An interslab slab cutting method is disclosed. However, the method disclosed in Patent Document 1 is not preferable because, as described above, the maintenance cost increases due to an increase in the number of work steps due to scarf maintenance. Moreover, it is not preferable in terms of lead time because it is a method in which scarf care is performed after partial rolling rather than gas cutting of a continuously cast slab.

  Further, Patent Document 2 discloses a method and an apparatus for removing surface flaws of a slab by arranging and rotating a water turbine attached with a rotary tool for wrinkle in the vicinity of the surface of a high-temperature metal slab. However, there are problems such as a considerable cost burden on the equipment, difficulty in removing wrinkles uniformly in the width direction of the slab, and the need for replacement / replenishment due to wear of the rotary tool for removing wrinkles.

  As described above, there still remains a problem that must be solved in order to easily and inexpensively remove foreign substances such as splash that are generated when the cast slab is cut with a gas torch and adhere to the surface of the slab.

JP-A-53-142952 (claims, etc.)

JP 60-24215 A (claims, etc.)

  The present invention has been made in order to solve the above-mentioned problems, and the problem is that the surface generated in the plate making process is caused by the splash generated during the gas cutting of the continuous cast slab adhering to the upper surface of the slab. An object of the present invention is to provide a simple and inexpensive method for cutting a continuous cast slab for preventing generation of flaws.

  In order to solve the above-described problems, the present inventors have studied a method for removing the splash remaining on the upper surface of the slab based on the above-described conventional problems, and the following (a) to (d) Knowledge was obtained and the present invention was completed.

  (A) As a method of removing the splash adhering to the upper surface of the slab, a method of rubbing the lower end portion of the plate-like tool against the upper surface of the slab conveyed on the table roller, or a gas from a gas injection nozzle arranged in the width direction of the slab The spraying method is simple and inexpensive.

  (B) As a method of rubbing the plate-shaped tool (a) on the upper surface of the slab, the plate-shaped tool is pivotally supported above the slab and rotatably about an axis facing the width direction of the slab, or The plate tool is suspended from above the slab, and in either case, the lower end of the plate tool is placed on the slab upper surface so that the line of intersection between the plate surface of the plate tool and the slab upper surface faces in the width direction of the slab. It is effective to make it contact.

  (C) In the case of (b) above, the angle formed between the upper surface of the slab in the slab conveying direction and the plate surface of the plate tool with respect to the contact position between the lower end of the plate tool and the upper surface of the slab is an acute angle (90 Less), the removed splash can be efficiently removed without scattering.

  (D) In the method of injecting the gas of (a), one or more gas injection nozzles are arranged at a height within 200 mm from the upper surface of the slab and in the width direction of the slab. It is effective to inject at a pressure of 7 MPa or more.

The present invention has been completed on the basis of the above knowledge, and the gist thereof is a method for cutting a continuous cast slab shown in the following (1) and (2 ).

  (1) A method of cutting a slab that removes splash adhering to the upper surface of a slab when the continuous cast slab is gas-cut and then transported on a table roller. Are pivotally supported around an axis that faces the width direction of the slab, or the plate-like tool is suspended from above the slab, and the plate surface of the plate-like tool and the upper surface of the slab, respectively The lower end of the plate-shaped tool is brought into contact with the slab upper surface so that the line of crossing faces the width direction of the slab, and the upper surface of the slab upstream of the slab transport direction from the contact position and the plate surface of the plate-shaped tool. A method of cutting a continuous cast slab characterized in that the formed angle is an acute angle, and the splash is removed by rubbing a plate-like tool against the upper surface of the slab (hereinafter also referred to as “first invention”).

( 2 ) In the continuous casting slab cutting method according to (1), one or two or more gas injection nozzles are arranged in the width direction of the slab at a height within 200 mm from the upper surface of the slab, It is preferable to remove the splash by injecting gas from the nozzle at a pressure of 0.7 MPa or more and blowing the gas on the upper surface of the slab (hereinafter also referred to as “ second invention”).

  In the present invention, the “axis facing the width direction of the slab” means an axis that faces a direction that does not coincide with the longitudinal direction of the slab, an axis that faces a direction perpendicular to the longitudinal direction (conveying direction) of the slab, and the longitudinal direction Including an axis oriented in a direction inclined with respect to a direction perpendicular to the axis.

  Further, “the line of intersection between the plate surface and the upper surface of the slab faces the width direction of the slab” means that the line of intersection of the two planes faces a direction that does not coincide with the longitudinal direction of the slab, as described above.

  According to the present invention, it is possible to manufacture a continuous cast slab generated by gas cutting of a continuous cast slab and having extremely little surface foreign matter such as splash that causes cold-rolled steel sheet by a simple and inexpensive method. it can.

  As described above, in the present invention, after gas cutting a continuous cast slab, a plate-like tool is pivotally supported above the slab in order to remove splash adhering to the upper surface of the slab due to gas cutting. Alternatively, the plate tool is suspended from above the slab so that the plate tool comes into contact with the slab upper surface, and the angle between the slab upper surface upstream of the contact position with the slab upper surface and the tool is an acute angle. This is a slab cutting method in which splash is removed by rubbing a plate-like tool against the upper surface of the slab.

Further, in addition to the installation of the plate-shaped tool described above, preferably, one or two or more gas injection nozzles are arranged in the width direction of the slab at a height within 200 mm from the upper surface of the slab, and gas is supplied from the nozzle. This is a slab cutting method in which splash is removed by spraying at a pressure of 0.7 MPa or more and blowing gas on the upper surface of the slab.
In the method of the present invention, as described above, in order to reduce thermal energy loss, suppress increase in distribution cost, and reduce lead time loss, immediately after the continuous casting slab is gas cut hot, Removal is preferably performed.

  FIG. 2 is a perspective view schematically showing the method for cutting a continuous cast slab according to the present invention. As shown in the figure, the continuously cast slab 1 gas-cut by the slab cutting gas torch is conveyed on the table roller 2 in the direction indicated by the arrow X in the figure.

  Then, the splash 7 remaining on the upper surface of the continuous casting slab 1 is removed by the plate-like tool 3 rubbed against the upper surface of the slab. Further, the splash 7 adhering to the upper surface of the slab is also blown off and removed by the compressed gas 61 blown from the gas injection nozzle 6 arranged in the width direction of the slab.

  FIG. 3 is a side view showing the continuous casting slab cutting method of the present invention. FIG. 3 (a) shows that the plate-like tool is pivotally supported above the slab and rubbed against the upper surface of the slab. Further, a method of removing the splash by blowing gas, and FIG. 5B shows a method of removing the splash by suspending the plate-like tool from above the slab and rubbing it on the upper surface of the slab and further blowing gas. Show.

  In the method shown in FIG. 5A, the plate-like tool 3 is pivotally supported around a shaft 5 that is above the slab and faces the width direction of the slab, and is provided at the lower end of the plate-like tool 3. Contacts the upper surface of the slab and is rubbed against the upper surface of the slab. Further, the angle (θ in the figure) formed by the upper surface of the slab upstream of the contact position in the slab conveying direction and the plate surface of the plate-like tool is set to an acute angle (less than 90 degrees). In this state, the splash 7 that has reached the lower end of the plate-like tool 7 is peeled and removed from the upper surface of the slab. Further, the splash that has not been sufficiently removed by the plate-like tool 3 and small foreign matters remaining on the upper surface of the slab are removed from the upper surface of the slab by the compressed gas 61 blown from the gas injection nozzle 6.

  In the method shown in FIG. 5B, the plate-like tool 3 is suspended from above the slab by the suspension device chain 8, and the lower end portion of the plate-like tool 3 is in contact with the upper surface of the slab and rubs against the upper surface of the slab. It has been. Other conditions are the same as in the case of FIG. 5A, and the splash 7 reaching the lower end of the plate-like tool 7 is peeled and removed from the upper surface of the slab.

  The reason why the scope of the present invention is defined as described above and the preferred scope of the invention will be described below.

(A) Position for removing foreign matters such as splash In any case of the method for removing a crush using a plate-like tool or the method for removing a splash using gas injection, the slab after gas cutting should be in an area where it is conveyed horizontally by a table roller. For example, the method of the present invention can be applied. However, continuous casting slabs are hot in terms of ease of peeling of foreign matters such as splash adhering to the slab surface at high temperatures, reduction of thermal energy loss, logistics cost, and reduction of lead time loss. Immediately after gas cutting, it is preferable to remove foreign matters such as splash.

(B) Removal by a plate-like tool 1) Method of pivoting or suspending a tool The method of the first invention for removing splash by a plate-like tool has a great effect of mechanically peeling and removing the splash adhered to the upper surface of the slab. . Even when the plate tool is pivotably supported above the upper surface of the slab or when the plate tool is suspended from above the upper surface of the slab, the plate surface of the plate tool and the upper surface of the slab By rubbing the lower end of the plate-shaped tool against the upper surface of the slab so that the line of intersection with the slab faces in the width direction, the splash adhered to the upper surface of the slab is mechanically peeled off.

  When pivoting a plate-like tool so that it can be pivoted, a method of pivotally pivoting around the upper side of the plate-like tool as an axis, around an axis passing through the plate surface of the plate-like tool Any method may be used, such as a method of pivoting pivotally or a method of pivoting pivotally about an axis parallel to the plate surface of the plate-like tool and outside the plate surface.

  When rubbing the lower end of the plate tool against the upper surface of the slab due to the weight of the plate tool, make sure that the pressing force exerted on the upper surface of the slab by the lower end of the plate tool is sufficient to peel off the splash. In consideration of the position of the center of gravity of the plate-like tool, it is preferable that the plate-like tool is pivotally supported around an axis passing through the upper side or one side of the upper portion. In the method of suspending the plate tool from above and rubbing the lower end portion of the plate tool against the upper surface of the slab, when the lower end portion of the plate tool is rubbed against the upper surface of the slab by the weight of the plate tool, the same as above. The suspension position of the plate-like tool is preferably determined so that a sufficient pressing force can be obtained.

  According to this method, it is possible to easily follow the vertical movement at the time of transporting (moving) the slab, and it is possible to remove foreign substances by the weight of the tool without a load meter or a pressure device. Therefore, it can be carried out simply and inexpensively.

  When the tool is rubbed against the upper surface of the slab by a mechanical pressing force such as a spring regardless of the weight of the plate-like tool, the pressing force may be set and adjusted separately.

2) Angle, material, mass, etc. between the plate surface of the tool and the slab upper surface Angle between the slab upper surface upstream of the contact position between the lower end of the plate tool and the slab upper surface and the plate surface of the plate tool (θ ) Must be an acute angle (less than 90 degrees). This is because by setting the above angle to an acute angle, foreign matters such as splash peeled off from the upper surface of the slab can be efficiently removed and accumulated without scattering again. In addition, by making the angle (θ) an acute angle, it is possible to prevent the cut continuous cast slab from causing interference such as a collision with the plate-like tool.

  The line of intersection between the plate surface of the tool and the upper surface of the slab needs to face the width direction of the slab. This is because when the intersecting line of the two planes coincides with the longitudinal direction, it does not have a tool splash removal action. However, the intersecting line does not necessarily exactly coincide with the width direction of the slab, that is, does not need to be orthogonal to the conveyance direction of the slab, and may be appropriately inclined. This is because, by appropriately tilting the intersecting line, the separated foreign matters such as splash can be accumulated and removed in the side surface direction of a specific direction of the slab.

  As the material of the plate-like tool, it is preferable to use carbon steel, stainless steel, or the like from the viewpoints of wear resistance, heat resistance, and splash peeling and removing action.

  The width of the plate tool is preferably set in accordance with the maximum width of the cast slab to be cast. This is because it is complicated to replace the tool with a different width each time the slab width changes.

  Moreover, it is preferable that the mass of a plate-shaped tool shall be 50 kg or more from a viewpoint of improving the removal effect of a splash. In particular, if the pivot position or suspension position is near the center of gravity of the tool from one side above the tool, the pressing force of the lower end of the tool on the upper surface of the slab tends to decrease. It is preferable to do.

In the first invention, the pressing force of the plate tool on the upper surface of the slab is preferably 390 N or more per unit length (m) in the width direction of the slab. However, with only the removal method using a plate-like tool, a minute splash or small foreign matter may partially remain on the upper surface of the slab. In such a case, in addition to the removal method using a plate-like tool, a method of spraying compressed gas from a gas injection nozzle is effective.

(C) Removal by gas blowing 1) Gas pressure and the height from the upper surface of the slab to the gas injection nozzle
In addition to the removal by the plate-like tool, the method of the second invention in which the spray is blown off by blowing the compressed gas from the gas injection nozzle onto the upper surface of the slab, in particular, the splash or small size that is not in close contact with the upper surface of the slab. This is effective in removing the foreign matter from the upper surface of the slab by blowing it away with the compressed gas injected from the nozzle.

The pressure of the gas injected from the gas injection nozzle is preferably 0.7 MPa or more. When the gas pressure is less than 0.7 MPa, the scattering force of foreign matter such as splash due to the injection gas becomes weak, and foreign matter remains on the upper surface of the slab, which causes cold rolling. Here, the gas pressure may be the value of the original pressure of the compressed gas. According to the investigations of the present inventors, in general factory equipment, the gas source pressure and the gas pressure in the pipe before the nozzle are almost the same value, and the pressure loss to the injection nozzle outlet is negligible. Because it is small.

The height from the upper surface of the slab to the gas injection nozzle is preferably within 200 mm. When the nozzle height from the upper surface of the slab becomes higher than 200 mm, the scattering force of foreign matters such as splash decreases as in the case where the injection gas pressure is low, and foreign matters remain on the upper surface of the slab. It is because it becomes the cause. The height from the upper surface of the slab to the gas injection nozzle is set to 30 mm or more in order to prevent the possibility of damage to the nozzle due to collision between the vertically slab and the nozzle and in consideration of the heat resistance of the nozzle. It is preferable.

2) Gas type, nozzle arrangement in the width direction of the slab, etc. As the compressed gas, compressed air that is inexpensive and can be used in large quantities is preferable. However, when importance is attached to non-oxidizing conditions, it is preferable to use nitrogen gas, argon gas, or the like.

  The gas injection nozzle may be of a general type, and no particular nozzle type is specified. The arrangement of the injection nozzles in the width direction of the slab is preferably an arrangement capable of exhibiting a foreign matter removing effect such as splash by compressed gas over the entire width of the slab.

  Moreover, it is preferable that the direction which injects gas shall be the direction inclined in the upstream of the slab conveyance direction. Even if foreign matter such as splash is blown off by gas injection, it may remain on the upper surface of the slab. In such a case, the possibility of removing the foreign matter again by gas injection is increased. is there. A preferred range of the angle (α in FIG. 3) formed by the slab upper surface and the injection nozzle axis is 15 to 90 degrees.

Furthermore, if the method of the 2nd invention described in said (B) and (C) is used, the more reliable peeling scattering removal effect, such as a splash, can be acquired.

  In order to confirm the effect of the method of the present invention, a slab is manufactured by continuous casting and the method of the present invention is applied at the time of cutting the slab, and then hot rolling and cold rolling are performed to manufacture a cold-rolled steel sheet. A test was conducted.

  Table 1 shows the range of change in the dimensional specifications of the cast slab and the steel plate in each process of continuous casting, hot rolling and cold rolling.

In addition, the steel component composition made into object is the mass%, C: 1.0% or less, Si: 3.2% or less, Mn: 2.3% or less, P: 0.12% or less, S: 0 0.02% or less.
In Table 2, the test conditions include the presence or absence of a plate-like tool, the support conditions for the plate-like tool, the angle between the tool and the slab, the spraying gas pressure, and the height of the injection nozzle. The quality is shown respectively.

  Foreign matter removal tests such as gas cutting of the cast slab and splash on the upper surface of the slab were performed by the method described with reference to FIGS.

  In a test using a plate-shaped tool, a carbon steel plate-shaped tool having a width of 1300 mm, a height (length) of 300 mm, a thickness of 22 mm, and a mass of 67 kg can be rotated about the upper side of the plate. A method of pivoting and a method of connecting a steel chain near the one side and suspending it from above the upper surface of the slab were used.

  Moreover, in the test which sprayed compressed gas, the nozzle for 1-10 gas injection was installed in the predetermined height position from the slab upper surface in the width direction of the slab, and compressed air was injected from the nozzle. The direction of the injection nozzle was inclined upstream in the slab conveying direction, and the angle (α) formed by the slab upper surface and the injection nozzle axis was in the range of 15 to 90 degrees.

  The test results were evaluated by the surface quality of the cold rolled coil. That is, the occurrence of surface flaws is visually inspected, the mass ratio (%) of the downgraded coil including the surface flaw occurrence part is calculated, and this is defined as the surface flaw occurrence rate (%). It was divided into three stages as follows. That is, the case where the surface flaw occurrence rate is less than 0.2% is extremely good (◎ in Table 2), and the case where the occurrence rate is 0.2% or more and less than 0.4% is good (◯ in Table 2). And the case where the rate of occurrence was 0.4% or more was regarded as defective (x in Table 2).

Test ID NO: 1 through 7 is a test for the present invention examples within the scope of range or the second invention of the first invention. Test numbers 8 to 13 relate to the second invention in which both the rubbing of the plate-like tool and the spraying of the compressed gas are performed, and are tests for the reference example in which only the compressed gas is sprayed. Further, the test number 1 4 is a test for a comparative example not performed any of the blowing of rubbing and the compressed gas of the plate-shaped tool.

Test numbers 1 and 2 are tests in which foreign matters such as splash are removed by a method that satisfies the conditions specified in the second invention. As a result, the surface flaw occurrence rate of the cold-rolled coil was less than 0.2%, and the surface quality was extremely good.

  Test Nos. 3 to 7 are tests that satisfy the conditions specified in the first invention, and the support method of the plate-like tool used both pivot support and suspension. In all the tests, foreign matters such as splash were well removed, and the surface flaw occurrence rate of the cold rolled coil was in the range of 0.2% to less than 0.4%, and the surface quality was good.

Test numbers 8 and 9 as reference examples were tests in which only compressed gas was sprayed , foreign matters such as splash were well removed, and the surface quality of the cold-rolled coil was good.

On the other hand, test numbers 10 and 11 which are reference examples are tests in which the height of the gas injection nozzle from the top surface of the slab is too high, and test numbers 12 and 13 which are also reference examples have the injection gas pressure of The test was too low. In either case, the surface quality of the cold-rolled coil was poor due to insufficient removal of foreign matters such as splash.

Test No. 14 is a comparative example, a test was not performed Splash removal that due to any of the methods of the plate-shaped tool and the compressed gas, the surface defects of the cold-rolled coil caused by foreign matter such as splash a large amount of generated The surface quality was poor.

  According to the present invention, it is possible to manufacture a continuous cast slab generated by gas cutting of a continuous cast slab and having extremely little surface foreign matter such as splash that causes cold-rolled steel sheet by a simple and inexpensive method. it can. Therefore, the method of the present invention can be widely applied as a method of manufacturing a slab having a clean surface after cutting in a gas cutting process of a continuously cast slab.

It is a figure which shows the cold-rolled steel photograph of the cold-rolled steel plate which originated in the foreign material on the slab surface. It is a perspective view which shows typically the cutting method of the continuous cast slab of this invention. It is a side view which shows the cutting method of the continuous cast slab of this invention, The figure (a) is pivotally supported so that a plate-shaped tool can be rotated above a slab, and is rubbed on the slab upper surface, and also gas is sprayed. FIG. 4B shows a method of removing the splash by suspending the plate-shaped tool from above the slab, rubbing it on the upper surface of the slab, and further blowing gas.

Explanation of symbols

1: continuous cast slab, 2: table roller, 3: plate tool,
4: gas torch for slab cutting, 5: pivot shaft, 6: nozzle for gas injection,
61: Compressed gas, 7: Splash, 8: Suspension device (chain)

Claims (2)

  A method of cutting a slab that removes splash adhering to the upper surface of a slab when the continuous cast slab is gas-cut and then transported on a table roller. The plate-shaped tool is moved above the slab. And pivotally supported about an axis facing the width direction of the slab, or the plate-like tool is suspended from above the slab, and the plate surface of the plate-like tool and the upper surface of the slab are respectively The lower end of the plate-shaped tool is brought into contact with the slab upper surface so that the intersection line faces the width direction of the slab, and the upper surface of the slab upstream of the contact position in the slab conveying direction and the plate surface of the plate-shaped tool are formed. A method for cutting a continuous cast slab, characterized in that the splash is removed by rubbing a plate-like tool on the upper surface of the slab and forming an acute angle.   One or two or more gas injection nozzles are arranged in the width direction of the slab at a height within 200 mm from the upper surface of the slab, gas is injected from the nozzle at a pressure of 0.7 MPa or more, and the gas is injected onto the upper surface of the slab. The method for cutting a continuous cast slab according to claim 1, wherein the splash is removed by spraying.

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