JPH01107902A - Method for rolling h-shape steel - Google Patents

Abstract

PURPOSE:To prevent the bending of a web and to decrease the press correcting load after the generation of the web bend by adjusting the respective circumferential speeds of upper and lower horizontal rolls according to the predicted quantity of the web bend and restraining both side edge parts of the flanges of a material to be rolled on the outlet side of a rolling mill. CONSTITUTION:The rotating speed of the lower horizontal roll 21B is set higher than the rotating speed of the upper horizontal roll 21A and the material is rolled vertically symmetrically under the conditions to generate the longitudinal direction of the web if the quantity of the web bend predicted in the material to be rolled after the rolling crowns upward at the time of operating the rolling mill 20. Furthermore, the two side edge parts of the flanges of the material to be rolled are restrained by flange guides 24 and the longitudinal upward camber to be generated in the material to be rolled is corrected to straighten the outside shape of the material to be rolled in the longitudinal direction. The quantity of the upward crowning web bend initially predicted in the material to be rolled is eventually negated by the transverse camber generated as a result of correcting the longitudinal upward camber. The above- mentioned correction is reversed and the rotating speed of the upper horizontal roll 21A is set higher than the rotating speed of the lower horizontal roll 21B if the quantity of the web bend crowns downward.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for rolling H-section steel.

[Prior Art] FIG. 4 is a schematic diagram showing the rolling process of H-beam steel by universal rolling. Rolled materials such as slabs and beam blanks are heated to a predetermined temperature in a heating furnace 1, and then formed into rough shaped steel slabs by a breakdown rolling mill 2.Then, they are passed through a transfer device 3 and then passed through a rough universal rolling mill 4. Then, reverse rolling is performed in an edger rolling mill 5 to reduce the thickness. Thereafter, it is finished rolled into a predetermined shape in a finishing universal rolling mill 6 and manufactured into a product.

FIGS. 5(A) to 5(C) are schematic diagrams showing rolling conditions in each rolling mill in the universal rolling. In the rough universal rolling mill 4, as shown in FIG. 5(A), upper and lower horizontal rolls 7A, 7B and left and right vertical rolls 8A, 8 are used.
B rolls the web and flange, respectively. Further, in the edger pressure kLR5, as shown in FIG. 5(B), the tip of the flange is rolled by grooved rolls 9A and 9B. Furthermore, finishing universal rolling mill 6
Now, as shown in Fig. 5(C), the upper and lower horizontal rolls I
The web and the flange are rolled down by the OA, IOB, and the left and right vertical rolls IIA, IIB, respectively, and the angle of the flange is formed into a substantially right angle.

By the way, the left and right flanges of the H-section steel after being rolled by a universal finishing mill may not be parallel to each other. This phenomenon may occur due to web bending as shown in FIG. 3 even when each flange is joined at right angles to the web. The allowable range of the amount of web bending δ is defined in JIS G31112, and is 2 mm or less when the nominal web height is less than 600 mm, and 3 mm or less when the nominal web height is over 800 mm.

If the web bends beyond the above-mentioned allowable range, it is necessary to correct it using a press, leading to an increase in manufacturing costs.

Note that the above web bending occurs when the web thickness is thin or the web height is large, which reduces the rigidity of the material and makes it easier to deform.
It occurs more noticeably in shaped steel.

Conventionally, the above-mentioned web bending was thought to be caused by a temperature difference between the upper and lower surfaces of the web during rolling. That is,
During hot rolling of H-section steel, the upper surface of the web is filled with roll cooling water,
While the temperature decreases due to the accumulation of flowing water such as descaler water, the lower surface of the web is not affected by this accumulated water, and the upper surface of the web is affected by the heat retention effect of the semi-closed space formed by the lower ends of the left and right flanges. Therefore, a temperature difference inevitably occurs between the upper and lower surfaces of the web, and when the rolled material is cooled to room temperature, there is a difference in the amount of heat shrinkage between the upper and lower surfaces of the web, resulting in web bending. It is thought that this causes

Therefore, in the conventional rolling method for H-section steel, in order to prevent the occurrence of web bending, the temperature difference between the upper and lower surfaces of the web is reduced by reducing the amount of roll cooling water, descaler water, etc., and strengthening the water drainage on the upper surface of the web. We are currently making adjustments.

[Problems to be Solved by the Invention] However, when web bending was observed using an actual machine, it was found that web bending was not necessarily caused only by the temperature difference between the upper and lower surfaces of the web.

In other words, if the web bending is caused only by the temperature difference between the upper and lower surfaces of the web, 1. Normally, the temperature on the upper surface of the nib is lower than the temperature on the lower surface of the web, so only an upwardly convex web bending will occur. In some actual rolling results, web bending with a downward convexity is observed.

In addition, when we look at rolled materials with thin webs (web thickness of about 1O2 or less), since the web is thin, the temperature difference between the upper and lower surfaces tends to be equalized by heat conduction in the web thickness direction. be. Therefore, even in this case, if the web bending was caused only by the temperature difference between the upper and lower surfaces of the web, the web bending would not occur due to the uniformity of the temperature difference. According to.

It is observed that more pronounced web bending occurs in thin web rolled materials.

Therefore, it is not possible to eliminate web bending only by reducing the temperature difference between the upper and lower surfaces of the web, and it is desired to provide a more direct countermeasure against web bending.

The present invention aims to reliably prevent web bending.

[Means for Solving the Problems] The present invention provides a rolling method for H-section steel in which a web is rolled down by upper and lower horizontal rolls of a universal finishing mill, and a flange is rolled down by left and right vertical rolls. The circumferential speeds of the upper and lower horizontal rolls are mutually adjusted according to the amount of web bending that is expected to occur in the material to be rolled later, and the edges on both sides of the flange of the material to be rolled are adjusted at the exit side of the universal finishing mill. It is designed to restrict the parts of the body.

[Function] As a result of various studies on the causes of web bending other than the temperature difference between the upper and lower surfaces of the web, the present inventor has found that web bending is related to vertical warpage in the longitudinal direction of the rolled material. Ta. In other words, ordinary rolled materials often warp upward or downward, especially at the rolling tip.
It is thought that the rolled material warps vertically in the longitudinal direction due to various factors. However, at the stage of rolling by a finishing universal rolling mill, the length of the rolled material is longer and the thickness of each part of the cross section is thinner than in the initial stage of rolling, so the longitudinal shape of the rolled material is different from the rolling machine. It becomes almost straight due to the bending moment due to the side guides and the bending moment due to its own weight. However, even if the rolled material has an external shape that is straight in the longitudinal direction, if it is rolled under conditions that should naturally cause upward or downward warpage in the longitudinal direction, the warpage in the longitudinal direction will be caused in the width direction. This results in warpage, or web bending. This phenomenon is caused by the same mechanism as shown in FIG. 2, where when a thin plate warped in the longitudinal direction is straightened and straightened in the longitudinal direction, warpage occurs in the width direction perpendicular to this. In other words, when attempting to correct the warpage by bending a material that is warped downward in the longitudinal direction in the longitudinal direction shown in FIG. 2, compressive strain,
A tensile strain occurs in the longitudinal direction of the back surface, a tensile strain occurs in the longitudinal direction (width direction) of the 0 surface, and a compressive strain occurs in the longitudinal direction of the back surface, resulting in the warpage in the width direction (upward This results in a convex bend).

The present invention actively utilizes the above-mentioned knowledge, and when a certain amount of web bending is expected to occur in a rolled material after rolling by a universal finishing mill.

■The circumferential speeds of the upper and lower horizontal rolls that roll down the web are mutually adjusted to perform vertical and asymmetric rolling under conditions that should cause upward or downward warpage in the longitudinal direction of the web. The both edges of the flange of the rolled material are restrained, the longitudinal warpage of the rolled material that would occur under the conditions of (■) above is corrected, the external shape of the rolled material is straightened in the longitudinal direction, and the longitudinal direction of (■) above is corrected. The warp in the width direction that occurs as a result of warp correction makes it possible to cancel out the amount of web bending originally envisioned in the rolled material.

A more specific explanation of the web bending prevention mechanism according to the present invention is as follows.

FIG. 1 is a side view showing an example of a universal finishing mill used for carrying out the present invention.

The universal finishing mill 20 has upper and lower horizontal rolls 21A.
, 21B roll down the web of the rolled material, and the right and left vertical rolls 22A, 22B roll down the flange of the rolled material. The rolling mill 20 has upper and lower horizontal rolls 21A and 21B.
A web guide 23 is provided on the entry side, and a flange guide 24 is provided on the exit side.

During operation of the rolling mill 20, if the expected web bending of the rolled material after rolling forms an upward convexity (the bending state shown in Fig. 3), Roll 21A
The rotation speed is higher than that of 2, and the rolling is carried out symmetrically from top to bottom under conditions that should cause upward warping in the longitudinal direction of the web, and the flange guides 24 restrain both side edges of the flange of the material to be rolled. The warping in the longitudinal direction that should occur in the rolled material is corrected, the external shape of the rolled material is straightened in the longitudinal direction, and the warping in the width direction (downwardly convex web The amount of convex web bending that was originally envisioned in the rolled material is canceled out by the bending.

On the other hand, when the rolling mill 20" (7) is operated, if the expected amount of web bending in the rolled material after rolling forms a downward convex shape (curved shape S opposite to that in Fig. 3), Conversely, the rotational speed of the upper horizontal roll 21A is set higher than the rotational speed of the lower horizontal roll 21B.

[Example] Using an experimental rolling mill as shown in Fig. 1, which is 1/8 scale of the actual machine, 8500X, which is an example of a material to be rolled by the actual machine, was
Rolling was performed using an H-shaped material made of pure lead (93.98% pb) equivalent to 200%. The dimensions of the rolled material are web thickness =
1.45 mm, flange thickness = 2.95■■, web inner width = IOm+s, flange width x 33.5 mg, and this is a 1/8 model of H3O0x200. The target reduction rate for the web and flange of the rolled material is 8% and 1, respectively.
The roll gap between the horizontal roll and the vertical roll was set as 2%, and the rotational speed of the upper and lower horizontal rolls was varied within a range of ±20%. As a result of this rolling, the tip of the rolled material was free until it was supported by the flange guide, but after it started coming into contact with the flange guide, it was corrected and became almost straight. Figures 6 and 7 were obtained as a result of measuring the curved shape in the web radial direction using a profile meter after rolling was performed by changing the rotational speed of the upper and lower horizontal rolls. Figure 6 shows the upper horizontal roll as E.
Figure 7 shows the results of rolling the lower horizontal roll at 5 rpm and the lower horizontal roll at 8 rpm, and the upper horizontal roll at 5 rpm.
This is the result of rolling as rp*. Figure 6 shows rolling where the upper horizontal roll is faster and causes a downward warp in the longitudinal direction of the web, and it is clear that correcting this with the flange guide results in an upwardly convex web bend. be. On the other hand, it is clear that if the lower horizontal roll is made faster as shown in FIG. 7, a downwardly convex bending of the web will occur.

From these measurement results, the relationship between the measured value of the web bending amount δ and the true speed rate φ determined by the following equation is shown in FIG.

According to the lower roll rotation speed figure 8, it is recognized that a linear relationship exists between the true speed rate φ of the upper and lower horizontal rolls during universal rolling and the amount of web bending δ after rolling. It is clear that the web can be straightened after finishing rolling by adjusting the rotational speed of the upper and lower horizontal rolls of the finishing universal rolling mill according to the web bending amount δ after finishing rolling.

What? As means for detecting the amount of web bending, techniques such as manual measurement using a depth gauge in the cooling bed, automatic measurement using a light cutting method, laser distance meter, etc. on the line after finishing universal rolling can be used.

In the present invention, the above-mentioned (1) of the actual measured value of the web bending amount and the vertical and horizontal roll rotation control basket in the direction to cancel this
The rotational speed control amount of the upper and lower horizontal rolls is determined from the relational expression shown in the following equation, and a straight web is created by controlling the rotational speed of the upper and lower horizontal rolls through automatic control using a dedicated calculation device or manual adjustment using operator guidance. It becomes possible to obtain.

That is, if the actual value of the web bending amount is δ;0.2■■, then from FIG. 8, φ! 0.1, so for example, if the lower horizontal roll is toorp■, the upper horizontal roll is 110
It is set to rP■.

This shows the results of rolling a 1501) x 200 rolled material at different circumferential speeds on an actual machine.Since the actual machine does not have separate upper and lower drives, the rotation speed of the rolls cannot be changed arbitrarily.Therefore, the universal finishing mill was developed. Roll diameters of the horizontal rolls were 1220 φ for the upper horizontal roll and 1320 φ for the lower horizontal roll, and rolling was performed at different circumferential speeds with the upper and lower diameters being different. The true speed rate φ in this case is -0,078. For comparison, rolling was also carried out using upper and lower horizontal rolls having the same diameter of 1300 mm. After rolling under these conditions, a sample was taken from the top side of the rolled material after crop cutting with a hot saw, and the amount of web bending was measured using a depth gauge. These results are shown in FIG. The average value of the amount of upward web bending is reduced by performing upper and lower different diameter rolling compared to upper and lower equal diameter rolling, and the lower roll circumferential speed is higher than the upper roll circumferential speed.
It is clear that the amount of web bending is affected.

In the above experiment, the present invention was carried out by rolling with the rotational speed of the upper and lower rolls being constant, but it is also possible to control the amount of web bending by changing the rotational speed of the rolls.

[Effects of the Invention] As described above, according to the present invention, by taking direct measures against web bending, web bending can be reliably prevented and the press straightening load after web bending can be reduced. can.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a rolling mill used in carrying out the present invention, Fig. 2 is a schematic diagram showing the mechanism of widthwise warping based on longitudinal warpage correction, and Fig. 3 is a schematic diagram showing a web bending state. , Figure 4 is a layout diagram showing the layout of the H-section steel rolling mill, Figure 5 is a schematic diagram showing the rolling state of H-section steel, and Figure 6 is a schematic diagram showing the rolling state of H-section steel.
The figure is a diagram showing the web bending state when the rotation speed of the upper horizontal roll is high. Figure 7 is a diagram showing the web bending state when the rotation speed of the lower horizontal roll is high. Figure 8 is a diagram showing the web bending state when the rotation speed of the lower horizontal roll is high. FIG. 9 is a diagram showing the relationship between the true speed rate of the horizontal roll and the amount of web bending, and is a chart showing the effects of the present invention. 20...Universal rolling mill. 21A, 21B...Upper and lower horizontal rolls, 24...Flange guide. Agent Patent Attorney Osamu Shiokawa 1 Figure 2 Figure 3 Figure 4 Figure 5 (A) (B) Figure 8 Figure 9

Claims (2)

[Claims] (1) In the rolling method of H-beam steel, in which the web is rolled down by the upper and lower horizontal rolls of the universal finishing mill, and the flange is rolled down by the left and right vertical rolls, it is expected that formation will occur in the rolled material after rolling by the universal finishing mill. The H-shape is characterized in that the peripheral speeds of the upper and lower horizontal rolls are mutually adjusted according to the amount of web bending, and that both side edges of the flange of the rolled material are restrained on the exit side of the universal finishing mill. Steel rolling method. (2) In claim 1, if the expected amount of web bending in the rolled material is upwardly convex, the circumferential speed of the lower horizontal roll is higher than the circumferential speed of the upper horizontal roll, and A method of rolling H-shaped steel in which the circumferential speed of the upper horizontal roll is higher than the circumferential speed of the lower horizontal roll.