JPS5910841B2 - Blowing method for rough shaped steel slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for blooming a rough-shaped steel billet for forming a steel ingot.

More specifically, by improving the pass schedule of blooming rolling, twisting can be prevented, and by using this to enable strong reduction, crop loss can be reduced, rolling efficiency can be improved by reducing the number of passes, and This invention relates to a method for blooming rough-shaped steel slabs that improves the rolling finishing temperature.

When blooming a steel ingot into a rough shaped steel billet for shaped steel, a high-lift mill performs reverse rolling while turning the steel ingot vertically and horizontally each time for width and thickness reduction. This process is repeated thoroughly to produce a rough shaped steel piece with the specified dimensions.

By the way, in blooming rolling, as mentioned above, the steel ingot is rolled back and forth between the front and back of the high lift mill, that is, reverse rolling is repeated, and the top and bottom parts of the finished rough-shaped slab form crops called fishtails and overlapping. occurs.

Minimizing this crop as much as possible directly contributes to improving the yield, and improving the yield in the blooming process, which is located at the beginning of the hot rolling process, clearly has important significance.

For this reason, improvements have been made to conventional path schedules and the like.

For example, in the slab blooming method where a slab is bloomed from a steel ingot, in order to eliminate fishtails and overlapping clots, the pass schedule adopts a pattern of heavy reduction in thickness in the first half and strong reduction in width in the latter half. What you can do is
This was proposed in Japanese Patent Publication No. 53-43381.

This late-stage strong reduction method of the pass schedule is extremely effective for reducing clotpulosus even in rough billet rolling.

In addition, various reduction distribution methods have been proposed in order to eliminate clotpulosus in slab blooming rolling.

For example, in Japanese Patent Publication No. 50-24900, fishtails and overlaps at the end of the slab are concentrated on one side of the top or bottom of the slab to reduce clotup loss. A single-pass method has been proposed in which rolling is performed to approximately the desired thickness using either a single pass or an even number of passes.

Furthermore, a combination method of a special reduction method at the initial stage of rolling and a subsequent ordinary blooming method has been proposed to reduce the clots loss of the slab.

That is, at the initial stage of steel ingot rolling, at least one pair of opposing surfaces of the head and bottom of the steel ingot are formed with four parts by rolling rolls, and then during the normal blooming process, a fishtail metal flow is created. It has been proposed to fill the recesses to form a fishtail and eliminate clothopuros.

However, it is difficult to simply apply the late-stage strong reduction method of the pass schedule, which is effective for reducing the clots loss of the slab, to the rough-shaped steel billet blooming method.

Furthermore, it is difficult to simply apply the slab reduction amount distribution method to the rough-shaped steel billet blooming method.

In other words, in the hole-type rolling of rough-shaped steel strips for shaped steel, the thickness reduction was uniformly strong in the rolling direction, but the width reduction had the problem of torsion as described later, and it was not possible to achieve a uniform strong reduction in the rolling direction. was Fumachi Noh.

For this reason, it was necessary to increase the number of passes by reducing the amount of width reduction, or to reduce the amount of width expansion in order to reduce the number of passes of width reduction, that is, to reduce the thickness reduction of the previous pass.

Therefore, preventing twisting is essential not only to secure the shape but also to reduce the number of passes and improve yield.

The inventors of the present invention focused on the twisting phenomenon that occurs when width reduction is actually performed in a mill, and as a result of repeated trials, they found that at the point when the rolling tip leaves the guide, the twisting force is greater than the guide restraining force. We found that when the material becomes too large, the guide is short relative to the length of the material to be rolled and the restraining force is small, so the material becomes unstable and twists when it comes out of the guide.

From this, we focused on the fact that twisting occurs when the azurol length and rolling reduction amount reach a certain limit, and quantified this relationship. That's what it means.

) It was confirmed that twisting does not occur if the pressure is lowered.

In a reversible rolling mill, the present invention stipulates the maximum width reduction amount that does not cause twisting in the azure length in order to prevent the rolled material from twisting during the width reduction rolling pass after the thick reduction rolling pass in the latter half of the steel ingot rolling pass schedule. It is characterized in that the width reduction rolling pass is performed according to the torsion limit curve.

This makes it possible to apply the maximum width reduction without twisting the material to be rolled, and also enables strong reduction in the thick reduction pass before the width reduction pass, making it possible to perform late strong reduction, reducing clot loss and reducing the number of passes. This results in improved rolling efficiency and improved rolling finishing temperature.

In addition, based on the knowledge that overlap of clotsupuros occurs when passing through the rolling method with a certain amount of rolling in either the reciprocating pass rolling method or the single-pass rolling method, it is assumed that the overlap occurs in all passes during the rolling schedule or in passes at a certain period of time. ,
The material to be rolled is rolled at the specified rolling reduction amount without passing through.
It has been proposed in Japanese Patent Publication No. 51-35383 to reduce the amount of rolling until the slab comes out of the roll, but this proposal is aimed at blooming of slabs, so it is difficult to prevent twisting. There is no awareness of the problem.

Therefore, even if the method of the present invention and this proposal are apparently similar,
The problem of the invention and the technical object thereof are completely different.

Furthermore, it is known from the above-mentioned Japanese Patent Publication No. 53-4 that twist generally occurs in the later stages of the reduction schedule when the roll length becomes longer, and that strong reduction in this area has a large effect on the yield.
This is a well-known fact from Publication No. 3381, etc.

This method is an improvement on the reduction method in this area.

The blooming method of the present invention will be explained in detail below.

Figure 1 shows the roll hole type of the high-lift mill, and in the latter half of the reduction pass schedule of 1 yen by the high-lift mill,
When the rough-shaped steel slab 3 is obtained by reducing the thickness using the hole type (3) of the caliber rolls 1 and 2, the rough-shaped steel slab 3 is protruded, or so-called widened.

This width expansion becomes larger as the thickness is reduced to reduce clotupulosus.

When width reduction is performed on this part 4 with the hole type ■, it is desirable to apply a strong width reduction to reduce the clots loss. As shown, the rough shaped steel piece 3 is twisted.

If this relationship is shown in Fig. 3, with the length L of the rough shaped steel slab on the horizontal axis and the width reduction amount Δ■ on the vertical axis, h1, h2...h
Obtain a curve connecting points i and hn, that is, a torsion limit diagram ■.

More specifically, if rolling is performed with a certain width reduction amount ΔVi, twisting occurs at the azure roll length Li.

If rolled with ΔVn larger than detailed i, it will twist from the initial rolling Ll (10), and with Δ■1 smaller than ΔVi, the total length Ln
(=L), no twisting occurs.

The line connecting these points 111+-hiyhn is the so-called torsion limit curve (2).

That is, if the roll is rolled in a region below this curve ①, in other words, in a light roll range, no twisting will occur.

However, in order to improve the rolling efficiency by reducing the number of passes, etc., it is sufficient to roll according to this limit curve (■).

This curve (■) differs depending on the rolling temperature, the size of the steel ingot, the size of the rough shaped steel billet, etc., and it is necessary to subdivide and maintain it.

FIG. 4 shows a preferred rolling control device for the /'% Irift mill for carrying out the blooming method of the present invention, and 1 and 2 are upper and lower hole type rolls equipped with the hole types I and II shown in FIG. So, 7
1 is a roll reduction device for the north roll 1, 8 is a reduction position control device that controls this device 7, 9 is a pulse transmitter that transmits a pulse number according to the rotation speed of the roll 1, and 10 is a rolling load signal that is transmitted. In the load cell, 11.12 is a thermometer that measures the temperature of the rolled material 3 placed at the front and rear surfaces of the high lift mill, and 13.14 is a thermometer that measures the temperature of the rolled material 3 placed at the front and rear surfaces of the high lift mill. This is a group of detectors for the leading and trailing ends of rolled materials such as wholesalers, which are arranged along the line.

15 is an input device for various data.

Reference numeral 16 denotes a general control device which calculates a pass schedule and outputs a rolling position reference signal to the rolling position control device 8 for each pass.

This control device 16 has a torsion limit curve (2) or a torsion limit drop amount as shown in FIG. 3, which are subdivided using parameters such as rolling temperature, steel ingot size, rough shape steel billet size, etc., and the input device Based on the above dimensions and temperature information given from 15,
It has a function of creating a pass schedule for late-stage heavy reduction type (particularly late-stage strong reduction type) prior to rolling by using the above-mentioned torsion limit curve.

It also has a function of outputting a rolling position reference signal to the rolling position control device 8 for each pass in accordance with this pass schedule.

Specifically, the late heavy thickness reduction type pass schedule firstly takes into account the input information and sequentially determines the amount of width or thickness reduction (uniformity in the rolling direction) for each pass in the first half of the series of passes.

Next, when entering the latter half of the series of passes and reaching the stage where strong width reduction causes twisting, first the thickness reduction amount of the thick reduction pass is determined in consideration of the twist limit curve of the next width reduction pass.

This thickness reduction amount is calculated using the torsion limit curve or the reduction amount selected based on the input information.

For example, the amount of heavy thickness reduction is equal to or slightly smaller than the amount of reduction obtained by adding the maximum width reduction amount and minimum width reduction amount of the torsion limit curve determined by the azurol length of the rolled material after this amount of rolling. (This is in order to add width reduction and also eliminate the protrusion.) A strong thickness reduction amount (uniform reduction amount pass in the rolling direction) is applied to the extent that the protrusion occurs.

In other words, the width reduction pass (two reciprocating passes) following the strong thickness reduction pass (
The amount of reduction is strong enough to eliminate at least the amount of bite that occurs during the thick reduction pass without twisting during the non-uniform reduction amount pass in the rolling direction.

Such a calculation process is performed once or multiple times in the latter half of a series of passes to complete a pass schedule.

Note that the thick rolling pass for obtaining the heavy thick rolling amount in the latter stage may be obtained in one pass or in two or more consecutive passes.

Further, the subsequent width reduction passes may also be obtained by two consecutive passes or two or more consecutive passes (for example, four passes).

Here, a roll-down position reference signal is output to the roll-down position control device 8 for each pass according to the pass schedule.

To talk about this, first of all, regarding the first half of the series pass,
Before each rolling pass, a rolling position reference signal (constant during the pass) is given to the device 8 according to the rolling reduction amount of each pass.

In addition, in the latter half of the pass schedule, the rolling position reference signal for this pass (constant during the pass) is set according to the above-mentioned heavy thickness rolling amount.
is output to the device 8, and in the first pass (outward pass) of the two width reduction passes following this strong reduction, for example, the reduction amount is different in the rolling direction, that is, the reduction amount is different in the azu roll length, that is, the twist limit curve is In order to perform width reduction rolling along the width, the device 8 sends a reduction position reference signal (changes during the pass) according to the azure length.
Output to.

In the second pass (return pass), a width reduction position reference signal (constant during the pass) that corresponds to the width reduction substantially along the twist limit curve is output.

This l-th pass will be specifically explained.

Now, for example, rolling in the first half of the pass schedule has been completed, and the second half of the pass schedule has been reached, where strong reduction is applied in two passes using the hole pattern ■ of rolls 1 and 2 in Fig. 1, and the rolling begins as shown in Figs. 1 and 6. Suppose that 4,4 occurs and width expansion occurs.

(In this example, the amount of bite is pass scheduled so that it becomes the sum of the maximum amount of reduction and the minimum amount of reduction on the torsion limit curve.

) Next, when applying the width reduction in the groove type I of the rolls 1 and 2 in FIG. It is applied to the reduction position control device 8.

The device 8 automatically operates the reduction device 7 and the reduction is set.

Next, when the material 3 to be rolled is bitten by the rolls 1 and 2 and a biting signal is given from the dowel 10, the pulses from the pulse generator 9 are counted and the rolling length (as-roll length) is calculated. , the device 1 is adjusted so as to give a rolling reduction amount ΔVi according to the torsion limit curve ■ in FIG.
6 gives a reference signal for the rolling position in the direction of opening the roll to the device 8, and in accordance with this, the device 8 operates the device 7 to open the opening so as to provide the rolling amount according to the curve shown in FIG. The part number 5 in East Fig. 6 shows the rolling reduction amount and rolling direction reduction amount distribution by this pass. It holds down the part and makes it flat, making it easier to bite in the next pass.

Since the twisting limit reduction amount is given to the entire length of the rolled material 3 in this manner, twisting does not occur even if the rolled material 3 is separated from the guide.

In the next second pass, in order to give the final reduction amount aimed at eliminating at least the protruding portions that were not rolled in the previous pass, the rolling is set by the device 16 via the devices 8 and 7, and the material 3 to be rolled is Rolled.

In this pass, in terms of the amount of reduction of the material to be rolled, the amount of reduction is the same as the first pass, the amount of reduction is distributed, and no twisting occurs.

The reference numeral 6 in Fig. 6 indicates the amount of reduction and the distribution of the amount of reduction in this pass, and in this way, the protruding portions 4, 4 caused by the previous strong reduction pass disappear without twisting in two passes. become.

In this example, the reduction amount is continuously controlled according to the azurol length along the torsion limit curve (■) in Figure 5. The reduction may be performed in the following manner, or the reduction may be reduced in steps as indicated by the broken line (■) in the same figure.

Furthermore, in the device example shown in FIG. 4, the azurol length is monitored by the pulse transmitter and the load cell, but the leading and trailing end detector groups 13.1
The azurol length can be detected using the tip detection signal No. 4, and the rolling reduction timing can be obtained.

Further, in the blooming method of the present invention, the rolling down position of the rolls can be manually controlled while observing the as-roll length.

The method of the present invention will be explained below with reference to Examples.

Table 1 shows an example of the basic rolling schedule pattern when rolling a rough-shaped steel billet with a web thickness of 80 m/m and a web height of 440 m/m from a steel ingot with a thickness of 860 m/m and a width of 945 m/m using the conventional method (later method). Width reduction is divided into two methods: the method of applying uniform reduction in the rolling direction by an amount that does not cause twisting) and the method of the present invention (the later width reduction pass is a method of applying different reduction amounts in the rolling direction along the twist limit curve). It is something.

The values are expressed in caliber opening.

As shown in Table 1, this method completes the rolling of the protruding portion in the minimum number of passes, so that the restriction on thickness reduction can be lifted and late-stage strong reduction can be performed to improve yield.

Furthermore, it has become possible to reduce the number of passes and ensure the finishing temperature.

The implementation results of Table 1 are shown in Table 2.

It can be seen that this method not only improves yield but also improves rolling efficiency and finishing temperature, making it an indispensable method for direct and semi-direct rolling after blooming.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the late rolling situation in the groove die, Fig. 2 is a diagram of the torsion state, Fig. 3 is an explanatory diagram of an example of the torsion limit curve, and Fig. 4 is a suitable diagram of a high lift mill implementing the method of the present invention. Fig. 5 is an explanatory diagram of the torsion limit curve adopted during width reduction in the latter stage, and Fig. 6 shows the bite situation after heavy thickness rolling and the amount of reduction and reduction by the width reduction rolling pass. It is an explanatory diagram showing amount distribution. 1...Top roll, 2...Bottom roll, 3
... Rough shaped steel billet (rolled material), 4 ... Bulging part, 5 ... Amount of width reduction in the 1st pass, 6
...Killing amount of the second pass of width pressure, 7...
Roll lowering device, 8... Rolling down position control device, 9
...Pulse transmitter, 10...Load cell, 11,12...Thermometer, 13,14...
. . . front and rear end detector groups, 15 . . . input device,
16...General control device.

Claims (1)

[Claims] 1 In order to prevent twisting of the rolled material during width reduction rolling after thick reduction rolling in the latter stage of steel ingot rolling, the maximum width reduction amount without twisting was specified in the azurol length in the town reverse double block rolling mill. A method for blooming a rough-shaped steel billet, characterized by width reduction rolling according to a torsion limit curve.