JPH01228606A - Method for hot edging of metal slab - Google Patents

Abstract

PURPOSE:To reduce power and to improve the quality by finding a position of the peak of a locally sheet thickness increased part in a caliber groove and setting a horizontal roll gap value by finding a horizontal roll output side sheet thickness by which the above position is in the caliber groove and in adjacent parts to the caliber peak part. CONSTITUTION:By use of a structure consisting of vertical rolls 2, 4 provided with a caliber and horizontal rolls 3, a locally sheet thickness increased part 5 of a rolled stock caused by an edging amount W1 is drafted by the rolls 3 at a peak 7 of the part 5 in a region where no biting flaw is generated. After performing sheet width change to a target sheet width, the stock is rolled to have a target thickness value by a horizontal rolling mill. Hence, a rolling power of the horizontal mill is reduced and a recess shape in the central part of the stock is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for hot width rolling of metal slabs.

[Conventional technology]

In order to realize a process that directly connects the continuous casting process that can utilize the sensible heat retained by the continuous casting slab to the rolling process that creates the product shape, it is necessary to calculate the difference between the width of the continuous casting slab and the width of the steel plate desired by the rolling process. The basic problem is that it must be kept within a certain range. For this reason, continuous casting slabs are rolled in the width direction to change the slab width.

This metal slab is rolled in the width direction using a vertical rolling mill with grooves, but when the amount of width change is increased by increasing the amount of reduction in the width direction, the cross section of the slab develops a locally increased thickness called a dog bone. Occur.

If this locally increased thickness increases, surface flaws may occur due to bite from the hole, and rolling power during widthwise rolling may increase. As a hot width reduction rolling method for this purpose, for example, it is proposed in Japanese Patent Application Laid-open No. 117501/1983.
There is a method of width rolling a metal slab, in which only the locally increased part of the plate thickness caused by width rolling is horizontally reduced to the same thickness as the supplied metal slab thickness, and width rolling is repeatedly performed again using slotted rolls.

[Problem to be solved by the invention]

The characteristics of the hot width rolling method for metal slabs are that, unlike the conventional blooming method for steel ingots, it targets continuously cast slabs, and the ratio of the roll contact arc length to the average plate width during rolling;
That is, the roll gap shape ratio is as small as 0.1-0.2;
- The amount of repetition width reduction per cycle is as large as 200 to 300 fins. For this reason, the width reduction blade by the vertical rolls during width rolling does not propagate to the center of the width, resulting in localized plate thickness increase portions at both ends of the plate width. As proposed in the prior art, when performing so-called tongue-bone leveling rolling, in which the thickened portion is horizontally rolled to the original thickness of the metal slab, the thickened portion occurs at both ends of the sheet width. As a result, a width return phenomenon occurs in which some parts are stretched in the longitudinal direction but some parts are not restrained and spread in the board width direction. Therefore, the width change amount is obtained by subtracting the width return amount due to dogbone leveling rolling from the width reduction amount, and the width change efficiency, that is, the ratio of the width change amount and the reduction amount, is 60 to 80%. In addition, the actual total width reduction, which is the difference between the optical width of the metal slab and the target slab width, is 1.3 to 1.5 times the actual total width reduction, taking into account the amount of width return during dogbone rolling. Become.

Furthermore, compared to rolling of a rectangular flat plate with the same area, dogbone leveling rolling using a horizontal rolling mill generates large internal friction not only in the locally deformed area but also in the center area in the width direction. In addition, when the thickened areas at both ends of the plate width are stretched in the longitudinal direction, the central area in the width direction is also pulled in the longitudinal direction. A depression 10 to 20 fins deep occurs. Compressive stress due to rolling does not act on this concave area, but is simply a tensile phenomenon, so the internal quality is different from the local deformation areas at both ends of the plate width.The internal solidified structure does not undergo plastic processing due to rolling. It becomes inferior in quality.

For this reason, in the width rolling process, which has conventionally directly connected the continuous casting process and the hot rolling process, rolling efficiency is not hindered.
There has been a strong desire for a method for hot width rolling of metal slabs that reduces the rolling load and reduces the depression in the central region during width rolling.

The present invention provides an effective method for hot width rolling of metal slabs that solves the above problems.

[Means to solve the problem]

The present invention provides a method for solving the above problems, and the gist thereof is as follows.

A method of reversibly rolling a metal slab to a target dimension by arranging a vertical rolling mill using caliber hole type rolls in a skewer shape on the input and output sides of a horizontal rolling mill using horizontal rolls, When rolling the locally increased thickness on both sides of the slab in the width direction, which is caused by rolling the slab in the width direction with rolls, with the horizontal rolls, the cross-sectional dimensions of the slab on the exit side of the horizontal rolls and the next caliber hole type are used. Based on the radius of the roll and the amount of width reduction by the caliber groove roll, determine the position within the caliber groove of the peak of the local thickness increase on both sides of the slab width direction that occurs when rolling with the caliber groove roll. A method for hot width rolling of a metal slab, characterized in that the roll gap value of the horizontal roll is set by determining the exit side thickness of the horizontal roll whose position is within the caliber hole mold and near the tip of the caliber. It is.

[For production]

Hereinafter, the operation of the present invention will be explained with reference to the drawings. Figure 2 (a
) is an example of the stand configuration of width reduction rolling mills V, V2, in which a horizontal roll 3 is disposed between the stands of vertical rolls 2 and 4 with calibers 2-1.4-1. The metal slab 1 is reversibly rolled between each roll 2, 3.4. Figure 2(b),
(c) and (d) illustrate the cross-sectional shape of the slab during the rolling process.

That is, the continuous casting slab having a rectangular cross-sectional shape with a width Wo and a thickness h0 shown in FIG. 2(b) is rolled in the width direction as shown in FIG. 2(c) by a vertical roll 2.4 with a caliber. When rolling is performed by a reduction amount Δw I (−ΔW+/2+ΔW + /2) and the slab ledger W0 is set to W, a local thickness increase portion, a so-called tongue pawn 5, is generated at both ends of the width of the metal slab. If this locally increased thickness increases, surface flaws may occur due to bite from the holes of the vertical rolls, and rolling power may increase due to width direction rolling. These factors restrict the amount of width rolling that can be rolled, so the horizontal roll 3 of the horizontal rolling mill H horizontally rolls down the locally increased thickness part, as shown in Figure 2(d). Dogbone part 5 shown in
The plate thickness and the plate thickness h0+h are brought to the same plate thickness h0 as the other plate thicknesses, and width rolling is performed in the plate width direction again to reduce the plate width W+ (Δw+=(ΔWl/2+Δw+/2)). The so-called rolling process shown in FIG. 2(c) and FIG. 2(d) is repeated. In this case, as shown in Fig. 2(d), the metal slab has a depression 6 at the center of the width of the plate due to the phenomenon of thinning, and the center of the width of the plate has a thickness h - smaller than the ends of the width of the plate (ho - h).
-) cross-sectional shape. Further, the plate width W1 becomes the plate width W2 due to a so-called width return phenomenon in which the tongue bone portion 5 expands by Δwz (ΔW2/2+ΔWz/2) in the width direction. In addition, the width change rate in this case is (w wz) / (w,,
wl) or (ΔW1-ΔW2)/ΔW.

The present inventors have developed the above width rolling method as shown in Fig. 2(a).
Under the configuration of the vertical rolls 2 and 4 with calibers and the horizontal roll 3 shown in Fig. 1, only the peak part of the locally increased thickness part produced by rolling in the width direction is rolled by a horizontal rolling mill, and by repeating this process. After obtaining the target metal slab width,
Continuously cast slabs with a width of 1800 mm are produced by rolling in the thickness direction, including locally increased thickness areas, to obtain a predetermined shape.
mm, thickness 280 mm, slab width (750 ~
As a result of rolling various slab width sizes of 1800) Dragon and thickness 25011, the following findings were obtained.

In other words, the surface flaws on the metal slab due to the bite from the hole of the vertical roll with caliber are determined by the following formula (1) % formula %) The peak position of the tongue bone part Lllllll
This problem will not occur if it is kept within the range of the roll hole height direction, and the amount of width return will be reduced if the horizontal roll opening is widened when rolling a dogbone part (locally increased thickness). Δw z (Δwz) becomes smaller, and the width change rate (ΔW
, -Δwz(ΔW, ))/ΔW1, the depth of the recess at the center of the width, the crop weight generated at the front and rear ends of the slab, the rolling power, etc. were investigated, and results showed that they could be significantly improved.

Figure 4 shows the dogbone part (
The width return amount Δw2 necessary to obtain the above w0 is investigated when rolling a locally increased thickness part.

In other words, the horizontal roll opening is determined by the slab original thickness h0 as shown in Figure 2.
By rolling only the dog bone part to a greater thickness than the roll opening that maintains the width, the width return amount Δw z (ΔW3
) becomes smaller, and the width change rate (ΔW1−Δwz(ΔW,)
)/Δw, is improved.

FIG. 5 illustrates the relationship between the depth of the depression 6 generated in the central part of the slab in the width direction due to width rolling and the total width reduction amount for obtaining the target width of the width-rolled finished slab from the continuous casting slab width. The rolling of the peak of the tongue bone part (pointed head) by the horizontal roll of a horizontal rolling mill does not cause thinning phenomenon in the width center part, and after the width rolling is completed, the thickness reduction including the dog bone part is carried out, so the normal width is reduced. Compared to rolling, the depth of the depression at the center of the width is significantly improved.

FIG. 6 shows the relationship between the crop weight generated at the front and tail portions of the continuous casting slab and the total width reduction amount for obtaining the width rolling finished target slab width from the continuous casting slab width. The method of rolling only the peak of the dogbone section using a horizontal rolling mill greatly improves the cropping amount because it alleviates the metal flow in the rolling direction.

FIG. 7 illustrates the relationship between the rolling power required to process the slab and the total width reduction amount.

In the method of rolling only the peak of the dogbone part using a horizontal rolling mill, the amount of deformation of the slab metal is small, so the rolling power is significantly improved.

Based on these findings, the present inventors have determined that the width reduction amount ΔW,
Following the flow shown in Fig. 3, the local plate thickness increase area 5 that occurs is applied with a horizontal roll to the pointed area 7 of the local plate thickness increase in an area where no bite flaws occur. Thereafter, by repeating the rolling process shown in Figure 1 (b) and (C), the width is changed to the target width, and then a hot width rolling method is used in which the strip is rolled to the target thickness using a horizontal rolling mill. This is a proposal.

〔Example〕

Next, an example of the method of the present invention will be shown. The rolling conditions are as shown in Table 1, and as shown in Figure 2, the first vertical rolling mill
Horizontal rolling mill H - 2nd vertical rolling mill a V Z 3 stands (
An example in which a continuously cast slab with a width of 1800 mm and a thickness of 280 mm was manufactured into target slab dimensions of a width of 750 mm and a thickness of 250 I using a reverse rolling mill (hereinafter referred to as V, , H, and V2) is shown below.

At the same time, the conventional rolling method carried out as a comparative example is as shown in Table 2 (a), as shown in the rolling schedule of
Rolling was carried out as described in Japanese Patent No. 7501.

In contrast, in the present invention, as shown in the rolling schedule shown in Table 2 (b), the dogbones generated by rolling in the width direction during horizontal rolling aH are not rolled, and only the pointed portions of the dogbones are rolled. It was rolled for leveling so that the mold was filled with metal. Note that the values in parentheses in Table 2 indicate the actual reduction amount taking into account the width return and the dogbone part (locally increased thickness part). The target value is determined by considering the accuracy of model formula (1),
The caliber (K in Figure 8) fits within the height b. = 16
This is the result of setting the distance to 0m.

As is clear from the comparative examples of the conventional method and the method of the present invention in Table 3, the width changing efficiency was significantly improved, and as a result, the width center depression amount, cropping amount, and rolling power were also significantly improved.

Table 1 Rolling Conditions Table 2 Example of Rolling Schedule In this example, (1) Hot continuous casting slab size width 1800 x thickness 284 ■ Sodium hot continuous casting target slab size width 972 x thickness 253 mm (2) Of the N baths, Although V-V-H is repeated N times (the first pass is V-H), the 2nd to (N-1)th V
-For V-H, apply the procedure shown in the flowchart of FIG. (Since the 1st bath is the first bath, the Nth bath is not applicable because it involves thickness reduction.) (3) The coefficient of 2 (1) is a
=0.00105, b =0.39663, C=-
624,3266, d = 1358.4335 is used.

(Example) Dog bone beak position during 2nd pass VVH, B = a x (1745-1532) + b
(1745/324) + c X (1250/ 2
/ 324) + d-156,4 [Target] [Target straightness] (4) The width return amount during thickness rolling by H is the method 2 to 4 of the present invention
The following formula is used for the pass number.

wn = e x (wo wl) + r
X (WO/F■+)+gx (R/l(+)+
hx (H+ -Hz)/Hr+i
... (2) Use.

WD = Min(ΔB+, ΔB2) ・(
3) ΔB, =0.0427XWo 24.51ΔB
z = C1X j'n(wow+) C2C+
=0.0161X Wo 8.225C2=C,X
1nlQ Table 3 Comparison example between the conventional method and the method of the present invention [Effects of the invention] The rolling method of the conventional method in width direction rolling of a metal slab under a process that directly connects the continuous casting process and the hot rolling process is rolling using a horizontal rolling mill. The power and the depression in the center of the width are large. On the other hand, according to the method of the present invention, it is possible to reduce the rolling power of the horizontal rolling mill without interfering with the rolling time, and also to improve the internal quality of the metal slab because it is possible to improve the depression in the center of the width. has a beneficial effect.

[Brief Description of the Drawings] Figures 1 (a), (b), and (c) are explanatory diagrams showing changes in the cross-section of the slab in the width direction during the width rolling process according to the method of the present invention, and Figure 2 (a) is an explanatory diagram showing the changes in the widthwise cross section of the slab according to the method of the present invention. An example of the stand configuration of a width reduction rolling mill for carrying out the method is shown, and FIG. 2 and 3 are flow diagrams for carrying out the rolling method according to the present invention, and FIG. Figure 5 is a graph showing the relationship between width return and width reduction using the horizontal roll opening as a parameter when rolling. Figure 6 is a graph illustrating the relationship between the total width reduction amount to obtain the width finishing target slab width, and Fig. 6 shows the relationship between the crop weight percentage and the total width reduction amount, with the conventional method crop weight at 1200 am as 100%. The illustrated graph, Fig. 7, is a graph illustrating the relationship between electric power consumption and total width reduction amount, Fig. 8.
The figure shows a part of the vertical roll in detail.

Claims (1)

[Claims] A method of reversibly rolling a metal slab to a target dimension by arranging a vertical rolling mill using caliber hole type rolls in a skewer shape at the input and exit sides of a horizontal rolling mill using horizontal rolls. In this case, when rolling the locally increased thickness on both sides of the slab in the width direction, which is generated by rolling the slab in the width direction with the caliber groove roll, with the horizontal roll, the cross-sectional dimension of the slab on the exit side of the horizontal roll and , based on the radius of the next caliber groove roll and the amount of width reduction by the caliber groove roll, calculate the peak of the local thickness increase on both sides of the slab width direction that occurs when rolling with the caliber groove roll. A metal slab characterized in that the position within the caliber hole mold is determined, the thickness of the exit side of the horizontal roll where this position is within the caliber hole mold and near the tip of the caliber is determined, and the roll gap value of the horizontal roll is set. hot width rolling method.