Method of pre-controlling shapes of continuous-casting slab head and tail for reducing head and tail cut amount of hot rolling intermediate slab

Abstract

A method of pre-controlling the shapes of a continuous-casting slab head and tail for reducing the cut amount of the head and tail of the hot rolling intermediate slab. The continuous-casting slab head and tail, is cut into a shape such that an end surface of the head concaves inwards and the tail projects outwards. The head and tail of a slab is cut in a curve that is symmetric to the center line in width thereof. Arc height, i.e. a maximum value of the concave amount at the head or that of the projection amount at the tail, is controlled within 0 mm-50 mm.

Claims

1. A method of pre-controlling shapes of continuous-casting slab's head and tail for reducing a cut amount of the head and tail of hot rolling intermediate slab, comprising: cutting at a position at the slab's head and tail a displacement y, wherein the displacement y is relative to a coordinate of an arc top of the slab, the (x, y) coordinate of the arc top of the slab is (0,0), x is a distance between a position and a center line of a width W of the slab, and the displacement y is calculated according to one of the following expressions, wherein H is an arc height which is a maximum value of a concave amount at the head or a projection amount at the tail $\begin{array}{cc}y=\frac{2H}{W}\mathrm{abs}\left(x\right),\mathrm{wherein}-\frac{W}{2}x\frac{W}{2},\mathrm{and}& \left(i\right)\end{array}$ wherein the resulting shape of the curve is a broken line symmetric to the center line of a width W of the slab; and $\begin{array}{cc}\{\begin{array}{cc}y=0& \mathrm{if}\mathrm{abs}\left(x\right)\frac{W^{}}{2}\\ y=\frac{2H}{W-W^{}}\mathrm{abs}\left(x\right)& \mathrm{if}\frac{W^{}}{2}\mathrm{abs}\left(x\right)\frac{W}{2}\end{array}& \left(\mathrm{ii}\right)\end{array}$ wherein W is an adjustable width, and wherein the resulting shape of the curve is a trapezoid and is symmetric to the center line of a width W of the slab; and wherein H being set between 15 mm and 30 mm, and cutting the slab into a shape according to one of the expressions results with an end surface of its head concaving inwards and an end surface of its tail projecting outwards.

2. The method of pre-controlling the shapes of continuous-casting slab's head and tail according to claim 1, characterized in that a head shape of the slab matches with a tail shape of a slab produced prior to the slab, and the tail shape of the slab matches with the head shape of a slab produced after the slab, that is, the slab produced prior to the slab and the slab produced after the slab are cut from the same continuous-casting slab.

3. The method of pre-controlling the shapes of continuous-casting slab's head and tail according to claim 1, characterized in that the curve is a broken and straight line, when the slab is wide, the head and tail of the slab are cut in an adjustable width of the middle part according to item (i) described in claim 1, two sides of the middle part are cut to a straight line, and the middle part and its two sides combine together to form the head and tail shapes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the schematic view of the configuration of the equipments in a conventional hot rolling line.

(2) FIG. 2 is the schematic view showing the deformation of the material head and tail before and after rough rolling.

(3) FIG. 3 is the schematic view of the pre-control method for the shape of the head and tail of the continuous-casting slab (the top plan view of the slab) according to the present invention.

(4) FIG. 4 is the schematic view of the curve cutting method according to the present invention.

(5) FIG. 5 is the schematic view of the straight and arc line cutting method according to the present invention.

(6) FIG. 6 is the schematic view of the broken line cutting method according to the present invention.

(7) FIG. 7 is the schematic view of the straight and broken line cutting method according to the present invention.

(8) FIG. 8 is the schematic view of the trapezoid line cutting method according to the present invention.

(9) FIG. 9 is the schematic view of the multi-broken line cutting method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(10) Thereinafter the present invention will be described in conjunction with the drawings and detailed embodiments.

(11) With reference to FIG. 3, a method of pre-controlling the shapes of continuous-casting slab head and tail for reducing the cut amount of the head and tail of the hot rolling intermediate slab, adopts the way of pre-controlling to cut the continuous-casting slab head and tail, that is, cutting the slab into the shapethe end surface of the head concaving inwards and that of the tail projecting outwards.

(12) The head shape of the slab matches with the tail shape of the former one, and the tail shape of the slab matches with the head shape of the latter one, that is, the former and latter slabs are cut from the same continuous-casting slab.

(13) The irregular deformation of the head and tail of the slab during hot rough rolling has a certain relationship with the factors such as the width, the rolling reduction in width, the thickness, the rolling reduction in thickness, the heating temperature of the slab, the steel grade, the load distribution of each frame, wherein the total rolling reduction in thickness, the width and the rolling reduction in width have the largest impact on the shape of the head and tail.

(14) Although the accurate dimension data of the final products cannot be obtained yet during cutting the continuous-casting slab, and the thickness and the width of the hot rolling intermediate slab can neither be confirmed, the thickness of the intermediate slab in a hot rolling line is kept within a certain range, according to which the thickness reduction ratio of the slab in the rough rolling region can be obtained. The range of a intermediate slab in a conventional hot rolling line is usually within 35 mm-65 mm, and assuming that the thickness of the continuous-casting slab is 230 mm, the rolling reduction ratio of the slab in the rough rolling region is about 3.5-6.5, thereby the pre-controlling amount can be confirmed. The specific pre-controlling shape thereof needs to be determined according to the function of the cutting machine.

(15) During manufacturing slabs in the continuous casting line, the head of the first continuous-casting slab can be cut according to the pre-controlling method of the present invention or according to the existing way of straight line; similarly, the tail of the last continuous-casting material can be cut according to the pre-controlling method of the present invention or according to the existing way of straight line. The slabs from the second one to the penultimate one are cut using the method for pre-controlling the shapes of the continuous-casting slab head and tail in accordance with the present invention, thereby the length of the irregular parts at the head and the tail of the intermediate slab after rough rolling is remarkably reduced, the head and tail cut amount drops and the yield is improved.

(16) The method for pre-controlling the shapes of the continuous-casting slab head and tail will be described in detail thereinafter.

(17) 1. The curve line pre-control methodcutting the continuous-casting slab head and tail in a curve which is symmetric to the center line in width of the slab to achieve the objective of compensating uneven deformation of the head and the tail. The arc height H, i.e. the maximum value of the head concaving inwards or the tail projecting outwards, is controlled within 0 mm-50 mm, as shown in FIG. 4; the range of the preferred arc height H is 15 mm-30 mm.

(18) This solution is suitable for the case that the cutting machine for the continuous-casting slab can adjust the cutting curve based on the width and assure the arc height.

(19) The curve line may be a circle arc, an ellipse arc, a sine curve, a polynomial curve or the like.

(20) Taking the circle arc line control method as an example, the cutting curve can be determined by the slab width W and its arc height H. Herein the slab head shape calculation is taken as an example, which is the same as the slab tail shape calculation; assuming that the coordinates of the arc top are (0,0), and the distance between a position and the center line in width is x as shown in FIG. 4, the displacement y of the position relative to the arc top coordinates (0,0) may be calculated according to the following expression:

(21) $y=\frac{H^2+W^2/4}{2H}-\sqrt{{\left(\frac{H^2+W^2/4}{2H}\right)}^2-x^2},\mathrm{wherein}-\frac{W}{2}x\frac{W}{2}.$

(22) 2. The straight and arc line pre-control method. If the continuous-casting slab cutting machine cannot control to cut in a curve line based on the width of the slab, the straight and arc line pre-control method may be used. When the slab is wide, in the adjustable width in the middle part, the head and the tail of the slab may be cut according to the arc line pre-control method, and the two sides can be cut in a straight line. The two parts combine together to form the head and tail shapes, as shown in FIG. 5.

(23) 3. The broken line cutting method 1. In consideration of the convenience of cutting the continuous-casting slab, the broken line cutting method may be used, as shown in FIG. 6. The cutting line can be determined based on the width W and the arc height H of the slab. Herein the calculation of the slab head shape is taken as an example, which is the same as that of the slab tail shape; assuming that the coordinates of the head top are (0, 0) and the distance between a position and the center line in width is x, the displacement y of the position relative to the slab head top coordinates (0, 0) may be calculated according to the following expression:

(24) $y=\frac{2H}{W}\mathrm{abs}\left(x\right),\mathrm{wherein}-\frac{W}{2}x\frac{W}{2}.$

(25) 4. The broken line cutting method 2.

(26) In consideration of the stability of the rough rolling, on basis of the broken line cutting method 1, the two sides of the shape are cut into straight lines according to the broken and straight line pre-control method. When the slab is wide, in the adjustable width in the middle part the head and tail of the slab may be cut according to the broken line pre-control method and the two sides can be cut in a straight line. The two parts combine together to form the head and tail shapes, as shown in FIG. 7.

(27) 5. The trapezoid pre-control cutting method. As shown in FIG. 8, the cutting line can be determined on basis of the width W, the adjustable width W, and the arc height H of the slab. Herein the slab head shape calculation is taken as an example, which is the same as the slab tail shape calculation; in the adjustable width in the middle part, the head and tail of the slab is cut along a straight line according to the trapezoid pre-control cutting method, and the two sides thereof is cut along an inclined line. The two parts combine together to form the head and tail shapes. Assuming that the coordinates of the middle position of the head top are (0,0) and the distance between a position and the center line in width of the slab is x, the displacement y of the position relative to the coordinates (0,0) of the middle position of the head top may be calculated according to the following expression:

(28) $\{\begin{array}{cc}y=0& \mathrm{if}\mathrm{abs}\left(x\right)\frac{W^{}}{2}\\ y=\frac{2H}{W-W^{}}\mathrm{abs}\left(x\right)& \mathrm{if}\frac{W^{}}{2}\mathrm{abs}\left(x\right)\frac{W}{2}\end{array}$

(29) 6. The multi-broken line pre-control cutting method, as shown in FIG. 9. The multi broken lines are used to form the shapethe head of the slab concaving inwards and the tail thereof projecting outwards.

Embodiments

(30) To testify the effect of the method of pre-controlling the slab head and tail shapes, a cutting and rolling test is done in the hot rolling line. In the test, the way of pre-controlling the slab head and tail shapes, the head and tail cut amount of the intermediate slab after rolling and the effect for reducing the cut amount is described.

(31) The conditions of the slab: to testify the effect of pre-controlling the shapes of the slab head and tail under different arc heights, four groups of tests are designed. In each group of test, two slabs with the identical thickness and width is selected, one of which is used for the head and tail pre-control process (the arc at the head assumes concaving and that at the tail assumes projecting), and another is a conventional cuboid slab for comparison. Eight slabs are selected, the relative data of which is shown in the tables 1-1 to 1-4.

(32) TABLE-US-00001 TABLE 1-1 The First Group Of Test Slabs (Unit: mm) Head Tail Target Target Precontrol Arc Arc Slab Slab Steel Steel No. Steel No. Flag Height Height Thickness Width Thickness Thickness 1-1 13170551 Yes 8 10 230 1150 3.01 1044 1-2 13170552 No 0 0 230 1150 3.01 1044

(33) TABLE-US-00002 TABLE 1-2 The Second Group Of Test Slabs (Unit: mm) Head Tail Target Target Precontrol Arc Arc Slab Slab Steel Steel No. Steel No. Flag Height Height Thickness Width Thickness Thickness 2-1 13170545 Yes 19 18 230 1150 3.97 1121 2-2 13170546 No 0 0 230 1150 3.97 1121

(34) TABLE-US-00003 TABLE 1-3 The Third Group Of Test Slabs (Unit: mm) Head Tail Target Target Precontrol Arc Arc Slab Slab Steel Steel No. Steel No. Flag Height Height Thickness Width Thickness Thickness 3-1 13170548 Yes 20 23 230 1150 3.53 1080 3-2 13170549 No 0 0 230 1150 3.53 1080

(35) TABLE-US-00004 TABLE 1-4 The Fourth Group Of Test Slabs (Unit: mm) Head Tail Target Target Precontrol Arc Arc Slab Slab Steel Steel No. Steel No. Flag Height Height Thickness Width Thickness Thickness 4-1 1317065 Yes 35 38 230 1000 4.97 979 4-2 1317066 No 0 0 230 1000 4.97 979

(36) The method of pre-controlling the shapes of the slab head and tail used in the tests is the circle arc line control method.

(37) In each group of tests, the slab is processed by the same heating and rolling technique. The results of the cut amount at the head and tail of the intermediate slab is shown in tables 2-1 to 2-4, wherein the cut area is the graph area of the head and tail shape detector, but not the surface area of the real thing.

(38) TABLE-US-00005 TABLE 2-1 The First Test Slab Result (Unit of Cut Surface Area: cm.sup.2) Head Tail Cut Cut Precontrol Arc Arc Head Tail Total Cut Optimize No. Steel No. Flag Height Height Area Area Area Effect 1-1 13170551 Yes 8 10 15.01 14.86 29.87 5.59% 1-2 13170552 No 0 0 20.86 10.78 31.64

(39) TABLE-US-00006 TABLE 2-2 The Second Test Slab Result (Unit of Cut Surface Area: cm.sup.2) Head Tail Cut Cut Precontrol Arc Arc Head Tail Total Cut Optimize No. Steel No. Flag Height Height Area Area Area Effect 2-1 13170545 Yes 19 18 10.91 10.14 21.05 35.56% 2-2 13170546 No 0 0 15.11 17.56 32.67

(40) TABLE-US-00007 TABLE 2-3 The Third Test Slab Result (Unit of Cut Surface Area: cm.sup.2) Head Tail Cut Cut Precontrol Arc Arc Head Tail Total Cut Optimize No. Steel No. Flag Height Height Area Area Area Effect 3-1 13170548 Yes 20 23 10.75 14.41 25.16 20.48% 3-2 13170549 No 0 0 19.74 11.9 31.64

(41) TABLE-US-00008 TABLE 2-4 The Fourth Test Slab Result (Unit of Cut Surface Area: cm.sup.2) Head Tail Cut Cut Precontrol Arc Arc Head Tail Total Cut Optimize No. Steel No. Flag Height Height Area Area Area Effect 4-1 1317065 Yes 35 38 15.01 14.86 29.87 4.62% 4-2 1317066 No 0 0 17.35 13.97 31.32

(42) Conclusion: the aforementioned four groups of test results show that all the cut amounts of the head and tail of the intermediate slab after rough rolling drops after being pre-controlled in shapes. There are different cut amount drop extents under different arc heights, and in the test conditions, the highest drop extent is 35.56%, which is a remarkable effect.

(43) The description above is only the preferred embodiment of the present invention, but not used for limiting the protection scope of the present invention, therefore, any modification, equivalent alternative, improvement and the like within the spirit and principle of the present invention shall fall into the protection scope of the present invention.