JP2001018002A - Manufacture of wide flange shape steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a surface defect due to that the material is lapped inside a fillet part, in intermediate rolling, by forming a relief part on the whole periphery of a radius part side face of a horizontal roll of a rough universal mill and rolling so that a roll gap reducing quantity per one pass of a vertical roll is set smaller than a relief quantity of the horizontal roll. SOLUTION: A large wide flange shape steel is produced a rough rolling process using a breakdown mill, an intermediate rolling process using a rough universal mill/edging mill and a finish rolling process using a finish universal mill. A horizontal roll 31 has a relief part 31a on the whole periphery of an radius part side face. A relief quantity (dx) of the relief part 31 is preferably <=15 mm. A roll gap reduction quantity X of a vertical roll 32 is made smaller than a relief quantity (dx) per one pass. Further, the distance from a roll face in the direction orthogonal to the roll axis at a start point of the relief part 31a at a roll side face is preferably more than ten times of the relief quantity (dx).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an H-section steel, and more particularly, to a method for manufacturing a large-sized and wide H-section steel. The large wide H-section steel according to the present invention has a web height of 400 mm or more, a flange width of 400 mm or more, and a flange thickness of 40 mm.
H-shaped steel with a size exceeding

[0002]

2. Description of the Related Art H-section steels are manufactured, for example, by a process using rolling mills arranged as shown in FIG. The heated rolled material is subjected to a rough rolling process of forming a rough steel slab A having an H-shaped cross section that can be rolled by a universal mill in a hole mill 2 and rolling back and forth between a rough universal mill 3 and an edging mill 4 a plurality of times. Thus, an H-section steel product 6 is formed through an intermediate rolling step of forming an H-section B and a finish rolling of an H-section C having a uniform cross-sectional dimension, such as raising a flange in the finishing universal mill 5.

[0003] Coarse steel slab A to be provided to a coarse universal mill
Has a web inner width substantially matching the roll width of the horizontal roll of the coarse universal mill, and a flange leg length substantially matching the product leg length. For this reason, it is necessary to separately produce coarse steel slabs having different cross-sectional shapes for each product nominal dimension in the rough rolling step. Therefore, for example, as shown in FIG.
1, using a breakdown mill having a grooved roll 10 having a belly box-shaped mold 13 and a flat box-shaped mold 12, in a rough rolling step of rolling a crude steel slab, according to the size and shape of the target cross section, In addition to the rolling process for adjusting the shape of the flange portion, the rolling process for reducing the web thickness, a rolling process for securing the flange leg length, a rolling process for adjusting the web height, or a rolling process for reducing the flange width, etc. Will be applied.

[0004] Here, large and wide H-section steels having various cross-sectional dimensions are subjected to a rough rolling step using a breakdown mill in a rough rolling step.
When manufacturing using two rolls, conventionally, to balance the rolling reduction of the web and flange according to the cross section,
As shown in FIG. 4, in the final pass of the breakdown mill,
The web thickness (tw _R ) of the coarse billet is determined by the web thickness (t
w) and the thickness of the flange (tf), tw / tf, to adjust the thickness appropriately.

[0005]

However, a large-sized product manufactured through such a rough rolling process, an intermediate rolling process using a rough universal mill and an edging mill, and a finish rolling process using a finishing universal mill. In the case of the wide H-shaped steel, there is a problem in that a surface defect occurs due to the breaking of the material inside the fillet portion (the root portion between the flange and the web).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a large and wide H-section steel which can advantageously solve the above-mentioned problems of the prior art and can prevent surface defects occurring inside a fillet portion.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have focused on an intermediate rolling step following a rough rolling step and have studied diligently. In the rough rolling process for large and wide H-section steel, the roll gap is changed multiple times in one hole using an open hole roll according to the target ratio of the web thickness and the flange thickness of the rough steel slab. It is generally rolled. In this rough rolling step, when the ratio of the flange section cross-sectional area to the entire cross section increases, when the thickness of the web section is reduced, as shown in FIG.
The width is widened until the flange strongly presses against the outer wall of the roll-hole type, and (ii) a part extends in the longitudinal direction of rolling, and accordingly, a part (b part) of the flange is reduced. (Iii) Further, a phenomenon occurs in which a part of the thickness returns to the thickness of the web (portion c).

[0008] Due to such a phenomenon, when a plurality of passes are rolled in the same hole die to reduce the thickness of the web portion, the portion b becomes unfilled, and the amount fluctuates and is not constant. Was. For this reason, in the large-sized and wide-width crude steel slab for an H-section steel, a large thickness reduction 21 occurs on the inner surface of the flange, and a surplus portion 22 occurs in the fillet portion.

[0009] The present inventors, when rolling the coarse steel slab A having such a surplus portion 22 in a coarse universal mill, the surplus portion is increased by the horizontal roll of the coarse universal mill in the initial stage of rolling. It is lowered (Fig. 3 (a)),
(FIG. 3 (b)) has occurred and has been found to be reduced in subsequent passes and eventually to defect 25 (FIG. 3 (c)). Then, they came to think that there was a problem in the shape of the side surface of the horizontal roll of the used coarse universal mill.

[0010] In order to prevent the surplus portion generated in the coarse steel slab from being broken during the rolling by the horizontal roll, the present inventors have a horizontal roll shape with a relief portion all around the radius side surface. It was found that by forming the shape and rolling the roll so that the roll gap reduction amount per pass of the vertical roll was smaller than the relief amount of the horizontal roll, it was possible to prevent the occurrence of breakage and consequently the occurrence of defects. .

The present invention has been completed by further study based on the above findings. That is, the present invention provides a method for producing an H-section steel through a rough rolling step using a breakdown mill, an intermediate rolling step using a rough universal mill and an edging mill, and a finish rolling step using a finishing universal mill. In the intermediate rolling, the horizontal roll of the coarse universal mill is a horizontal roll having a relief portion formed on the entire circumference of the radius portion thereof, and the roll gap reduction per pass of the vertical roll is calculated from the relief amount of the horizontal roll. This is a method for producing an H-section steel, which is reduced in size and rolled.

[0012]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a rolled material is sequentially passed through a rough rolling process using a breakdown mill, an intermediate rolling process using a rough universal mill and an edging mill, and a finish rolling process using a finishing universal mill. ,
Manufactures large and wide H-section steel. In the present invention, in a rough universal mill in an intermediate rolling step, a round roll having a round shape as shown in a preferred example in FIGS. 1B and 1C is used. That is, the horizontal roll 31 used in the present invention has a relief portion 31a all around the radius side surface. In addition, FIG.
(D) is a cross-sectional shape in a cross-section including the roll axis of the round portion of FIG. 1 (a).

The relief portion 31a referred to in the present invention is a notch formed between the side surface of the horizontal roll and a round portion (chamfer) (radius r in FIG. 1) and formed over the entire circumference of the roll. Here, dx shown in FIGS. 1B and 1C is the escape amount, and dy is the escape height. The relief amount dx is the relief part on the side of the roll.
31a from the starting point S to the intersection (line) R of the tangent (surface) α of the relief portion and the tangent (surface) β of the roll surface at the boundary K with the radius portion in the roll axis direction. Missed height
dy refers to the distance from the roll surface in the direction perpendicular to the roll axis of the starting point of the relief portion 31a on the side surface of the roll.

The escape amount dx is preferably 15 mm or less. If dx exceeds 15 mm, there is a disadvantage that a difference in flange thickness remains after rolling by a finishing universal mill. Further, dy is preferably set to 10 times or more dx from the roll surface for the same reason. Although FIG. 1B shows an example of a linear relief portion, the relief portion has a shape that does not cause folding by a horizontal roll as described later from the excess portion of the fillet portion as shown in FIG. If so, it may have any shape and may be a straight line or a curved line, preferably a circular arc, and need not be particularly limited. In the case of an arc, it may be a single radius or a double radius in combination.

FIG. 1C shows an example of a horizontal roll having a curved relief portion. The definitions of dx and dy are the same as in the case of FIG. FIG. 1D shows a conventional horizontal roll shape without a relief portion as in the present invention. There is simply a radius for chamfering. Intermediate rolling may be performed by using a horizontal roll provided with a relief portion as shown in FIG. 1 (b) and further reducing the roll gap reduction amount x of the vertical roll to the above-mentioned horizontal roll relief amount dx per pass. ,
As shown in FIGS. 2 (a) and 2 (b), the web can be rolled without greatly reducing the excess thickness portion 22 so that the horizontal roll 31 is folded, and the occurrence of folding can be prevented. . 2A shows the state before the rolling and FIG. 2B shows the state after the rolling.

On the other hand, the roll gap reduction amount X of the vertical roll is 1
If it is larger than dx per pass, it becomes as shown in FIG.
As shown in (1), the horizontal roll largely presses down the surplus portion 22, and as in the conventional case, the fold 23 occurs and a flaw (defect 25) occurs. (FIG. 2C shows the state before the reduction, and FIG. 2D shows the state after the reduction.)

[0017]

[Examples] Continuous cast slabs (thickness: 310 mm, width: 1800 mm) were used as rolling materials, subjected to a rough rolling process using a breakdown mill to obtain coarse shaped slabs. After an intermediate rolling process using a universal mill and an edging mill and a finish rolling process using a finishing universal mill, a product H-section steel of H700 × 500 × 50 × 70 was obtained. In the intermediate rolling process, the horizontal roll of the coarse universal mill is
1 (b), the relief amount d over the entire circumference of the side surface of the radius portion
A horizontal roll having a relief portion 31a for x and a relief amount dx changed as shown in Table 1 is used. Further, the maximum value X of the roll gap reduction amount per pass of the vertical roll of the coarse universal mill is defined as Intermediate rolling was performed as shown in Table 1.
An example in which a horizontal roll having the shape shown in FIG.
).

The surface of the product H-section steel thus obtained is visually inspected to check for flaws (surface defects). The results are shown in Table 1.

[0019]

[Table 1]

In the examples of the present invention, no generation of surface defects was observed, and good surface properties were exhibited. Further, in the inventive examples, no reduction in the rolling efficiency was observed. On the other hand, in the comparative examples and the conventional examples outside the scope of the present invention, occurrence of surface defects was observed.

[0021]

According to the present invention, a large and wide H-section steel can be manufactured at high rolling efficiency without occurrence of surface defects inside the fillet portion, and the industrially remarkable effect is achieved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the round shape (b) and (c) of a horizontal roll for a rough universal mill suitable for carrying out the present invention and the round shape (d) of a conventional horizontal roll.

FIG. 2 is a schematic diagram showing a state of reduction by a horizontal roll in a coarse universal mill.

FIG. 3 is a schematic view showing a state of reduction by a horizontal roll in a conventional coarse universal mill.

FIG. 4 shows the ratio of the final web thickness of the crude billet to the product web thickness and the flange thickness in the conventional rough rolling step, tw / tf.
6 is a graph showing the relationship of.

FIG. 5 is an explanatory view schematically showing a situation in which a flange is thinned and a surplus portion is generated in a crude steel slab in a breakdown mill.

FIG. 6 is an explanatory view schematically showing an example of a method for adjusting a shape of a coarse steel slab in a breakdown mill.

FIG. 7 is an explanatory view showing one example of a mill arrangement for manufacturing an H-section steel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 2 Breakdown mill 3 Coarse universal mill 4 Edging mill 5 Finishing universal mill 6 H-shaped steel product 10 Hole roll 11 Sizing hole type 12 Flat box type hole shape 13 Bery box type hole type 21 Filling 22 Extra thickness 23 Fold 25 Defect 31 Horizontal roll 31a Relief section 32 Vertical roll

Claims (1)

[Claims] 1. A method for producing an H-section steel through a rough rolling step using a breakdown mill, an intermediate rolling step using a rough universal mill and an edging mill, and a finish rolling step using a finishing universal mill in order.
In the intermediate rolling step, the horizontal roll of the coarse universal mill is a horizontal roll having a relief portion formed on the entire circumference of the radius portion thereof, and the roll gap reduction per pass of the vertical roll is calculated from the relief amount of the horizontal roll. A method for producing an H-section steel, comprising reducing and rolling.