JPH11309501A - Method for edging of slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely diminish a shortage in the width of a slab at the forward end part and rear end part after rolling by improving the setting accuracy of a rolling reduction width which determines the width and the length in the wide width region of the forward end part and rear end part. SOLUTION: Regarding a slab 2 heated in a heating furnace 1, a rolling reduction width E is set based on the size of a slab, a rolling condition or the like so that the widths of terminal parts 2a, 2b become wider than the width of a normal part 2c by an amount according to the differences of turning back widths between the terminal parts 2a, 2b and the normal part 2c caused by rolling and then, holding and pressing are executed along the whole length of the slab. In this case, the widths of rolling reduction of the terminal parts 2a, 2b are corrected based on a slab temperature and a temperature difference in the slab.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab in which hot slab is rolled to a predetermined width in a hot rolling operation before the heated slab is rolled. It relates to a width reduction method.

[0002]

2. Description of the Related Art Since there are remarkable advantages in energy saving and process shortening by consolidation of continuous casting (hereinafter, continuous casting) molds, in recent years, a width reduction process is sometimes introduced into an upper process of a hot rolling line.

In this width reduction process, when the slab width is set so that the width of the slab becomes the same width from the front end to the rear end, and the slab is pressed, the cross-sectional shape in the width direction of the slab after processing is as shown in FIG. As shown in FIG. 5, at the front end and the rear end, the central portion in the width direction has a relatively thick shape (see FIG. 5A),
In addition, the stationary portion has a so-called dog bone shape in which the thickness at the end portion in the width direction is large (see FIG. 5B). For this reason,
When subsequent rolling is performed, a shortage of width occurs at the leading end and the trailing end of the slab due to the material flow in the longitudinal direction.

That is, since the width return at the time of rolling is larger in the steady portion than in the leading end portion and the trailing end portion, the width of the steady portion and the end portion (the leading end portion and the trailing end) are reduced by the width reduction before rolling. If the width of each part is formed to be the same, shortage occurs at the leading end and the trailing end after rolling.

As a method of addressing this problem and reducing the lack of width at the leading end and the trailing end, a conventional method has been disclosed in, for example,
There are known slab width reduction methods described in JP-A-79721 and JP-A-5-200411.

[0006] The method described in Japanese Patent Publication No. 6-79721 discloses a method in which when a slab is pressed by a pair of press tools, the difference in width return between the end portion and the steady portion due to slab dimensions and the like. According to the width of the constant width wider than the width of the steady portion, the front end and the rear end of the slab are subjected to squeezing at the leading end and the rear end with a constant reduction width wider than the steady portion. This is a method for forming a wide area.

In the method described in Japanese Patent Application Laid-Open No. 5-200411, the width of each wide area provided to the leading end and the trailing end is sequentially determined while forming a plurality of steps toward the stationary part. This is a width reduction method for a slab that performs squeezing by controlling the reduction width so as to reduce the width.

That is, in the conventional width reduction method, the width return amounts of the leading end, the trailing end, and the steady portion are predicted based on the dimensions of the slab, rolling conditions, and the like, and the leading end and the trailing end are accordingly adjusted. The pressing process is performed by setting the rolling width so as to be wider than the stationary portion.

[0009]

However, in the above conventional width reduction method, the width and length of the wide area at the front end and the rear end are determined by the slab dimensions (slab width and slab thickness),
The slab width after pinching and the rolling conditions (roll diameter, rolling reduction) are determined. Even if the parameters (slab width, etc.) are the same, the slab width at the leading end and the trailing end is In some cases, the width shortage fluctuated, and the width shortage could not be sufficiently reduced.

According to the present invention, by increasing the accuracy of setting the rolling width for determining the width and length of the wide area at the leading end and the trailing end, the shortage of the width at the leading end and the trailing end after rolling is ensured. The task is to make it smaller.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention relates to a slab after heating and before rolling, wherein at least one end portion of the front end portion and the rear end portion is provided. The width of the rolling reduction based on the slab dimensions, rolling conditions, etc., so that the width of the rolling portion is wider than the width of the steady portion by an amount corresponding to the difference in the width return amount between the end portion and the steady portion due to the rolling. A width reduction method for a slab in which a slab width reduction is performed by setting and pressing the entire length of the slab, wherein a reduction width of the end portion is corrected based on a slab temperature and a temperature difference in the slab. Things.

Here, the above-mentioned terminal region is generally 1
It is in the range of about 50 to 2000 mm. The present inventors have investigated the shortage of the width at the leading end portion and the trailing end portion after rolling and the cause of the fluctuation, and found that a slab dimension (slab dimension) which is a parameter used when determining the rolling width by the conventional method. In addition to width, slab thickness), slab width after pinching, and rolling conditions (roll diameter, rolling reduction), slab temperature conditions (slab temperature, temperature difference in slab) contribute to the above-mentioned fluctuations in width shortage, etc. I found what I was doing.

The present invention has been made on the basis of the above-mentioned knowledge, and corrects the rolling width of the end portion based on the slab temperature conditions (slab temperature, temperature difference in the slab), so that the leading and trailing ends after rolling are corrected. This is to reduce the width shortage in the part.

In hot rolling, the slab is heated to a predetermined heating temperature in a heating furnace, but the temperature distribution in the slab is not always uniform. For example, as shown in FIG. The temperature rises due to the influence of the heating furnace wall, and in the steady part, there is a temperature reduction part called a skid mark accompanying the contact with the slab transport part.

Then, the slab having the same slab dimensions (slab width, slab thickness), slab width after squeezing, and rolling conditions (roll diameter, squeezing rate) having the same slab width setting conditions are subjected to slab pressing and rolling. Is performed, as shown in FIG.
The width shortage differs depending on the slab temperature conditions (slab temperature, temperature difference in the slab) before the pressing, and it has been found that the width shortage has a certain correlation with the slab temperature conditions.

Further, as can be seen from FIG. 6, even if the slab temperature Ts is the same, the width shortage tends to increase as the temperature difference ΔT within the same slab increases. This is because the larger the temperature difference ΔT in the slab before the pinching is, the more the longitudinal flow of the material is promoted at the leading and trailing ends where the material restraining force in the longitudinal direction is weaker than the widthwise flow of the material. It is thought to be easier. It should be noted that the present invention does not correct the width shortage simply by the slab temperature.

Accordingly, the slab temperature conditions (slab temperature, slab temperature,
If the correlation between the temperature difference within the slab) and the width shortage is determined, the rolling width at the end is corrected based on the temperature conditions (slab temperature, temperature difference within the slab) of the target slab. Later shortage of the distal end is reduced.

That is, if the difference between the width of the slab after the pressing in the steady portion and the width of the slab at the distal end is defined as the step-pressing amount △ Wp (see the following equation (1)), In addition to the slab dimensions (slab width and slab thickness), the slab width after the squeezing process, and the rolling conditions (roll diameter, reduction ratio), which are the conventional rolling width setting conditions, The slab temperature condition (slab temperature, temperature difference in the slab) is set as a variable, for example, based on the following equation (2). That is, by correcting the slab temperature condition (slab temperature, temperature difference in the slab) in addition to the conventional reduction width setting condition, the width shortage of the end portion after rolling is reduced.

△ Wp = Wp ₀ −Wp ₁ (1) Wp ₀ : Slab width after pinching of the end portion Wp ₁ : Slab width after pinching of the steady portion ΔWp = f (Hs, Ws, Wp ₁ , D, r, Ts, ΔT) (2) Here, Hs: slab thickness Ws: slab width D: rolling roll diameter r: rolling reduction ratio.

Next, according to the present invention, the width of at least one of the leading end and the trailing end of the slab after the heating and before the rolling is set so that the width of the slab is equal to the width of the rolling end. The width of the slab is set such that it is wider than the width of the steady part by an amount corresponding to the difference in the width return amount between the slab and the slab that performs pinching over the entire length of the slab based on the slab dimensions and rolling conditions. It is an object of the present invention to provide a width reduction method for a slab, wherein the slab is heated so that the temperature difference in the slab is reduced, and then the slab is subjected to the pinching process.

Next, a third aspect of the present invention is the same as the second aspect, except that the slab dimensions, the slab width after the pressing, the rolling conditions, the slab temperature, the slab temperature difference, and the rolling From the correlation with the width shortage that occurs at the later end,
Obtaining the upper limit of the temperature difference in the slab corresponding to the upper limit of the allowable width shortage amount, heating the slab so that the temperature difference in the slab is equal to or less than the upper limit of the temperature difference, and then performing the pinching process. It is characterized by the following.

As shown in FIG. 6, it can be seen that, even at the same slab temperature, the width shortage based on the slab temperature condition is reduced by reducing the temperature difference in the slab. When the slab dimensions and the like and the slab temperature are determined, the relationship between the temperature difference in the slab and the width shortage is uniquely determined, and the upper limit value of the temperature difference in the slab in which the width shortage is within an allowable range is determined. Can be

Therefore, by reducing the temperature difference in the slab before the squeezing process, preferably by soaking to a temperature equal to or lower than the upper limit value of the temperature difference, even if the rolling is performed with the same rolling width as the conventional one, the width shortage is reduced. It is acceptable. That is, the fluctuation of the width shortage amount based on the heating temperature condition decreases, and the absolute value of the width shortage amount also decreases.

Here, the slab temperature is determined by hot rolling conditions in order to obtain a predetermined product material.

[0025]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an upstream side of a hot rolling line L to which the slab width reduction method of the present invention is adopted.

In FIG. 1, reference numeral 1 denotes a heating furnace, and the temperature in the furnace is controlled by a heating furnace temperature control device 10.
The slab 2 extracted from the heating furnace 1 is pressed by a pressing device 3
2A, the width of the leading end 2a and the trailing end 2b, which are the trailing ends, is changed by the following rough rolling to the leading end 2a, the trailing end 2b, and the stationary part 2c. The width is wider than the width of the stationary portion 2c by an amount corresponding to the difference between the width return amounts. Subsequently, the slab 2A is rolled by the rolling mill 4 to be a predetermined steel plate 2C.

The pressing device 3 includes a pair of press tools 3a whose pressing surfaces face each other on the left and right sides. The pressing width E of the pair of pressing tools 3a is controlled by a command from the pressing width setting device 5.

As in the conventional case, the slab width information 7 of the slab 2 extracted from the heating furnace 1, the slab width method 8 after the squeezing process, and the rolling condition information 9
Is entered.

A temperature sensor 6 is arranged on the line L on the upstream side of the press device 3, and the temperature sensor 6 controls the surface temperature at the center in the width direction of the slab 2 moving toward the press device 3 in the longitudinal direction. The measurement signal can be supplied to the rolling width setting device 5.

In the rolling width setting device 5, the temperature sensor 6
2A, the surface temperatures Tb and Tc, which are the highest temperature and the lowest temperature at the center position in the width direction of the slab 2, are obtained as shown in FIG. 2A. This surface temperature T
The slab temperature Ts (= Tc) and the temperature difference ΔT (= Tb−Tc) in the slab are determined based on b and Tc, and the step clamping pressure at the front end 2a and the rear end 2b is calculated by the above equation (2). Then, the amount of reduction in the width of the squeezing width in the longitudinal direction at the front end portion 2a, the steady portion 2c, and the rear end portion 2b is determined. However, as for the rolling width of the steady portion 2c, as in the conventional case,
The slab temperature condition may be obtained without using it as a parameter.

With the above configuration, the heated slab 2
Is reduced in width by a pair of press tools 3a, and the width of the leading end 2a and the trailing end 2b is reduced by the difference in the width return amount between the leading end 2a or the trailing end 2b and the steady part 2c by rolling, respectively. The width becomes wider than the width of the stationary portion 2c by the corresponding amount. When the rolling width E for this rolling is set, the slab temperature is corrected by correcting the rolling width at the front end portion 2a and the rear end portion 2b based on the slab temperature Ts and the temperature difference ΔT in the same slab. Ts and temperature difference Δ in the same slab
The influence of T on the width shortage after rolling of the leading end portion 2a and the trailing end portion 2b is reduced.

Here, in the above description, the temperature difference in the slab △
As T, the difference between the temperature difference Tb and Tc at the center in the width direction of the slab 2 is used, and Tc is used as the slab temperature Ts. Slab 2 using temperature Ta
Slab temperature Ts and the temperature difference in the slab △
Obviously, a defined temperature other than the above may be used as long as it expresses T.

In the above embodiment, the surface temperature of the slab 2 extracted from the heating furnace 1 is directly measured, but the slab temperature Ts and the temperature difference ΔT in the slab are estimated from the temperature distribution in the heating furnace 1 and the like. You may do so.

In the above-described embodiment, the amount of reduction is determined based on the above equation (2).
After calculating the rolling width once with (Hs, Ws, Wp ₁ , D, r), the rolling width is corrected for the end portions 2 a and 2 b based on the corresponding temperature conditions (Ts, ΔT). You may do so.

Next, a second embodiment will be described with reference to the drawings. Note that the same devices and the like as those in the above-described embodiment will be described with the same reference numerals. As shown in FIG. 3, the basic configuration of the line L is the same as the conventional one. In the rolling width setting device 5, based on the slab dimension information 7, the slab width method 8 after the pinching process, and the rolling condition information 9. The rolling width is set so that the width of the end portions 2a and 2b is wider than the width of the steady portion 2c by an amount corresponding to the difference in the width return amount between the end portions 2a and 2b and the steady portion 2c by rolling. decide.

In this embodiment, the temperature difference control device 1
1 is provided. The temperature difference control device 11 includes a temperature difference measurement unit 11A and a temperature difference control unit 11B. The temperature difference measuring means 11A calculates or measures the temperature distribution in the slab in the heating furnace 1 based on the control amount by the heating furnace temperature control device 10, the furnace temperature, and the like.

The temperature difference control means 11B is supplied with the allowable width shortage upper limit information 12, the slab dimension information 7, the slab width method 8 after the pressing and the rolling condition information 9, and the temperature difference control means 11B. The slab temperature Ts and the current temperature difference ΔT in the slab are input from the measuring means 11A.

The temperature difference control means 11B calculates the temperature difference ΔT in the slab and the end of the slab 2 based on the slab size of the target slab 2, the slab width after pinching, the rolling conditions, and the slab temperature Ts. The upper limit of the temperature difference in the slab corresponding to the allowable width shortage is obtained from the correlation with the width shortage generated in the portions 2a and 2b. As described below, the heating furnace temperature control device 10 is operated while appropriately inputting the current slab temperature difference information from the temperature difference measuring means 11A,
Further, a slab extraction signal is output when the temperature falls below the target temperature difference upper limit value.

In the above configuration, the slab 2 is extracted from the heating furnace 1 in a state where the slab 2 is equal to or less than the predetermined upper limit of the temperature difference,
The width reduction performed by the press device 3 reduces the influence of the slab temperature Ts and the temperature difference ΔT within the slab on the width shortage of the end portions 2a and 2b even if the reduction width control similar to the related art is performed. .

As a result, even if the rolling width control is carried out under the same conditions as in the prior art, the fluctuation of the width shortage of the leading end 2a and the rear end 2b of the slab 2 after rolling is small and the absolute width shortage is absolute. The value is also small.

Here, in the above-described embodiment, the temperature of the heating furnace 1 is directly operated to make the temperature difference ΔT in the slab uniform so that the slab 2 extracted from the heating furnace 1 is removed. A heating device for uniform heating is provided separately on the upstream side of the press device 3, and the temperature difference Δ
You may make it carry out soaking heating so that T may be made small.

In the above embodiment, the predetermined slab temperature Ts determined by the slab size, the slab temperature Ts, and the like are used.
Although it is described that the soaking is performed so as to be equal to or less than the temperature difference, the temperature difference ΔT in the slab regardless of the slab temperature Ts or the like.
May be performed so as to reduce the temperature.

[0043]

EXAMPLE The slab 2 under the condition that the slab temperature Ts was 1200 ° C. and the temperature difference ΔT in the slab was 70 ° C. was subjected to pinching and rolling.

At this time, when temperature conditions were not taken into consideration as the rolling width setting conditions, as shown in FIG. 4 (a), the width shortage in the leading end portion 2a and the trailing end portion 2b after rolling was averaged. 5 mm was generated.

On the other hand, the slab temperature Ts = 12
Based on the temperature difference of 00 ° C. and the temperature difference ΔT in the slab = 70 ° C., the step clamping pressure was set to 5
As shown in FIG. 4 (b), the width of the leading end portion 2a and the trailing end portion 2b after rolling was reduced by 1 mm on average, as shown in FIG.
Reduced to

Further, under the same conditions as above, the soaking was carried out so as to reduce the temperature difference ΔT in the slab to 30 ° C., and the shortage of the width of the leading end portion 2a and the trailing end portion 2b after rolling was 1 mm on average. It became.

[0047]

As described above, in the present invention, by correcting the rolling width of the end portion based on the slab temperature and the temperature difference in the slab, or by heating the slab so that the temperature difference in the slab becomes small, There is an effect that the width shortage at the end of the slab after rolling is small and stable.

As a result, it is possible to realize a significant reduction required for the width integration of the continuous casting slab, to save energy and shorten the process.
Further, the yield is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a device configuration according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams for explaining the temperature distribution in the slab in a complex manner, wherein FIG. 2A is a plan view of the slab, and FIG.

FIG. 3 is a diagram showing a device configuration according to a second embodiment of the present invention.

4A and 4B are diagrams illustrating the effect of preventing a width shortage according to the present invention, wherein FIG. 4A is a diagram of a comparative example, and FIG. 4B is a diagram of an example based on the present invention.

FIG. 5 is a cross-sectional view in the width direction of the slab after the pinching process;
(A) is a cross-sectional view at a terminal portion, and (b) is a cross-sectional view at a steady portion.

FIG. 6 is a diagram for explaining the relationship between the slab temperature condition and the width shortage in a complex manner.

[Explanation of symbols]

 L line Ts slab temperature ΔT temperature difference in slab E reduction width 1 heating furnace 2 slab 2a tip 2b rear end 2c steady part 3 pressing device 4 rolling mill 5 reduction width setting device 6 temperature sensor 7 slab dimension information 8 after processing Slab width information 9 Rolling information 10 Heating furnace temperature control device 11 Temperature difference control device 11A Temperature difference measurement means 11B Temperature difference control means

Claims (3)

[Claims] The width of at least one of the leading end and the trailing end of the slab after heating and before rolling is determined according to the difference in width return between the leading end and the stationary part due to the rolling. The width of the slab is reduced by setting the reduction width based on the slab dimensions, rolling conditions, and the like so that the width is wider than the width of the steady portion by a predetermined amount. A width reduction method for a slab, wherein the width is corrected based on a slab temperature and a temperature difference in the slab. 2. The width of at least one end of the leading end and the rear end of the slab after heating and before rolling is determined according to the difference in width return between the end and the steady part due to the rolling. The width difference of the slab in the slab width reduction method in which the reduction width is set based on the slab dimensions, rolling conditions, and the like, and the slab is subjected to squeezing processing over the entire length of the slab so that the width is wider than the width of the steady portion by the amount A method for reducing the width of a slab, comprising heating the slab to a smaller size and then performing the pinching. 3. An allowable width shortage from a slab dimension, a slab width after pinching, a rolling condition, and a correlation between a slab temperature, a temperature difference in the slab, and a width shortage generated at an end portion after rolling. Calculating the upper limit of the temperature difference in the slab corresponding to the upper limit, heating the slab so that the temperature difference in the slab is equal to or less than the upper limit of the temperature difference, and then performing the pinching process. 2. The method for reducing the width of a slab according to 2.