JPH11347601A - Rolling method of coarse billet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method for rolling a rough shaped steel piece capable of changing a flange thickness. SOLUTION: Rolled material 40 in rough rolling in hot rolling
In the step of shaping the flange portion, the flange portion of the material to be rolled 40 is interrupted and rolled using the shaping die 1 having the protruding portion 1b, and the end 41 of the material to be rolled 40 is the bottom of the shaping die of the shaping die 1 After rolling, the material to be rolled 40 is rolled by applying a further reduction without restraining both ends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of rolling a rough shaped billet of a shaped steel.

[0002]

2. Description of the Related Art FIG. 10 is a view schematically showing a hot rolling process of a section steel such as an H-section steel. First, the outline of the hot rolling process of a section steel will be described with reference to FIG. Heating furnace 5
A material such as a slab, a bloom or a beam blank heated to a predetermined temperature in 1 is rolled into a coarse shaped slab by a shaping mill 52, and thereafter, a universal mill 53a, 5
The rolls are rolled to the product shape and dimensions by a group of coarse universal rolling mills consisting of 3b and edger rolling mills 54a and 54b or a group of horizontal rolling mills having a die for forming steel and a finishing mill 55.

[0003] In the forming and rolling mill 52, for example, when a slab 61 as shown in FIG. 11 is used as a raw material to roll a crude steel slab for H-section steel, a plurality of edging rolling box hole dies 62 for forming a flange portion, 63, 64, and the thickness of the portion corresponding to the web is reduced, and a desired coarse shaped slab is rolled by a hole die 65 that is roll-formed into a substantially H shape. A method of forming such a coarse shaped steel slab is disclosed in, for example, Japanese Patent Publication No. 58-19361.

[0004] The process of forming a flange portion in the conventional method will be described in detail with reference to FIG. First, the end face of the slab is restrained by the side wall 62a of the die 62 for edging rolling, and an interruption is made by the projection 62b. Next, the material to be rolled is punched by the die 63 having a large die width, a large protrusion height and a large projection angle. While being constrained by the side of the mold, the interruption formed by the
At 3b, the depth is increased, the interruption angle is increased, and the flange portion is formed.

[0005] Next, the portion of the material to be rolled into which the depth of the roll is deepened is pushed and expanded by the die 64 and edging pressure is reduced to form a flange portion. At this time, the flange width can be increased by increasing the edging reduction amount, and the rolling stability can be secured by constraining by the groove side wall 64a in the latter half of the edging reduction. Finally, the thickness of the portion corresponding to the web is reduced by the die 65, and the desired crude steel slab is rolled by rolling and forming into a substantially H-shape.

[0006]

If it is possible to form a coarse shaped steel slab having a thick flange portion from a slab having the same thickness, not only can a large-sized shaped steel be manufactured,
Since it is possible to increase the thickness reduction in the flash part in the subsequent process, there is a great merit that it is possible to manufacture a flaw-free product by increasing the reduction amount in the subsequent process. However, in the conventional method for rolling a crude steel slab as described above, it is extremely difficult to form a coarse steel slab having a thick flange portion from a slab having the same thickness. Hereinafter, the reason will be described.

First, in the step of forming the groove 62, since the slab 61 is slit, the thickness of the flange portion is at most half the thickness of the slab. In addition, in the step of the die 63, the material to be rolled is restrained by the die side surface 63a, so that it is difficult to increase the thickness of the flange portion. Here, the restriction by the hole-shaped side surface 63a is because this restriction was considered to be indispensable for stably expanding the interruption.

Further, in the step of forming the groove 64, when the width reduction by edging is increased, as shown in FIG.
Only the flange foot contacting the hole side wall 64a is increased in thickness,
A bad effect such as generation of a lap flaw in a post-rolling process occurs, and the thickness of the flange portion cannot be effectively increased.
Furthermore, it is well known that in the process of the die 65, the so-called flange thinning occurs in which the web is mainly pressed down and the flange is elongated by stretching the web, so that the thickness of the flange is reduced. Therefore, it is difficult to increase the thickness of the flange portion.

As described above, in the conventional method for rolling a rough shaped steel slab, it was extremely difficult to form a rough shaped steel slab having a thick flange portion from a slab having the same thickness.

[0010] Another problem is that, in the conventional method for rolling a crude steel slab, all the dies have side walls indispensable. It has become difficult to arrange all these holes in the roll body length, which has been a constraint on the build size.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method of rolling a crude steel billet capable of changing a flange thickness.
It is another object of the present invention to provide a method for rolling a rough shaped slab having good efficiency and good rolling stability. Further, it is another object of the present invention to provide a method for rolling a coarse shaped billet, which can effectively increase the thickness of a flange portion. It is another object of the present invention to provide a method for rolling a coarse steel slab which enables the shaping of a large sized coarse steel slab by effectively utilizing the roll body length.

[0012]

According to the present invention, there is provided a method for rolling a rough billet according to the present invention, wherein a shaping die having a projection is used in a step of forming a flange portion of a material to be rolled in rough rolling in hot rolling. After the flange portion of the material to be rolled is interrupted and the end of the material to be rolled comes into contact with the bottom of the molding die of the shaping die, without restraining both ends of the material to be rolled, the rolling is further reduced. In addition, it is rolled.

[0013] Further, the one-pass reduction when the end portion of the material to be rolled is further reduced after contacting the end portion with the bottom of the die is larger than the strain at which the change rate of the deformation resistance of the material to be rolled to the strain is saturated. This is performed with a reduction amount that causes distortion.

Further, in the above-mentioned molding die, a sum of an angle of a half of an apex angle of the projection and an angle of a bottom of the die is 45 ° or less.

Further, the present invention is characterized in that the projections of the molding hole are used as side walls of an adjacent hole.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an explanatory diagram of a hole type used in an embodiment of the present invention. The die 1 shown in FIG. 1 is used in a rolling process using a die 63 shown in FIG. 11 showing a conventional example. As shown in FIG. 1, the mold 1 has only the protrusion 1b and does not have a side wall.

Hereinafter, the rolling method of the present invention using the die 1 will be described with reference to the steps leading to its completion.
While the slab end face is constrained by the side wall 62a of the die 62 shown in the conventional example, an interruption is made by the projection 62b. Then, the material to be rolled 40 with the interruption is formed by the die 1.
The end 41 is rolled until it contacts the bottom of the die as shown in FIG. 1 (b). Up to this point, it is the same as the conventional method.

In the conventional example, it is considered that it is indispensable to restrain both ends of the material to be rolled in order to perform the subsequent reduction stably. The material to be rolled is constrained by the side wall 63a to perform rolling.
However, in this step, if both ends of the material to be rolled are constrained by the side walls of the hole, the thickness of the flange cannot be increased. Therefore, the present inventors have made intensive studies to enable stable rolling without restraint by the side wall of the groove and to increase the thickness of the flange in this step. As a result, they have found the following new findings.

That is, after the end portion 41 of the material to be rolled comes into contact with the bottom of the die, the material can be rolled stably without further restraining both sides of the end portion of the material to be rolled by further applying a large reduction. At the same time, the thickness of the flange can be effectively increased. Hereinafter, the process leading to this finding will be described. The inventor of the present invention enlarges the material to be rolled by a groove-shaped projection 1b having a height Hs, and makes the total amount of reduction after the end 41 of the material to be rolled contact with the bottom of the hole-shaped material equal to one-pass reduction. The amount (2 × ΔWe) was variously changed, and changes in rolling stability and flange thickness were investigated. Table 1 shows the results.

[0020]

[Table 1]

From Table 1, the one-pass reduction amount (2 × ΔWe)
) And rolling stability are related, and the one-pass rolling reduction (2 ×
It was found that the larger [Delta] We), the more stable the rolling. FIG. 2 is a diagram showing the relationship between the flange thickening strain εfw (vertical axis) and the rolling reduction (2 × ΔWe) (horizontal axis) under the condition 4 in Table 1. From FIG. 2, it was found that the thickness of the flange portion can be efficiently increased in proportion to the amount of reduction under the condition that stable rolling is possible.

Next, as the rolling reduction in one pass (2 × ΔWe) is larger, the rolling is more stable, and the thickness of the flange portion can be efficiently increased in proportion to the rolling reduction. The analysis was performed, and the value of the one-pass reduction amount was examined. FIG. 3 shows that the material to be rolled is interrupted and enlarged by a hole-shaped projection 1b having a height Hs.
3 shows a state in which 1 is in contact with the bottom of the die (FIG. 3A) and a deformed state in which further reduction is applied thereafter (FIG. 3B). Hereinafter, the analysis result will be described based on FIG.

The length of the rolled material end 41 in the vertical direction before rolling is equal to the height of the hole-shaped projection and is Hs. When the reduction amount in one pass is 2 × ΔWe, a new flange portion 43 is created due to the interruption caused by the rolling of one side ΔWe, and the flange portion before rolling and the created flange portion are vertically spaced by ΔWe. Is applied. Distortion this εfw
Εfw = ln (Hs / (Hs + ΔWe)).

As shown in FIG. 3 (b), rolling reaction forces P1 and P2 act on the toe of the flange portion of the material to be rolled and the bottom of the die, and this value causes a vertical rolling strain εfw. It is almost proportional to the product of the deformation resistance kf and the contact areas C1 and C2. There is a certain relationship between the deformation resistance kf and the strain. FIG. 4 shows, as an example, the relationship between the strain and the deformation resistance in a compression test of 0.20% C carbon steel at 1200 ° C. As can be seen from FIG. 4, in a relatively small region where the rolling distortion is 0.15 or less, the rate of change of the deformation resistance with respect to the distortion is large,
When the rolling strain is about 0.15 or more, the rate of change decreases.

That is, when the length lf of the formed flange portion due to interruption in the previous pass of the material to be rolled before rolling is left and right non-uniform for some reason, or the right and left leveling of the roll is inappropriate. In this case, there is a difference in the rolling distortion between the left and right flange portions in the path, but when the rolling reduction is relatively small, that is, when the rolling distortion is relatively small, the difference in deformation resistance between the left and right flange portions due to the difference in distortion is small. It becomes larger, and the rolling counterforce P1 on the left and right sides of the flange acting on the bottom of the die
It is considered that there is a difference in P2, which causes rolling instability.

Further, if the rolling amounts of the right and left flange portions are different, a difference occurs in the area of the contact region, which further promotes rolling instability. Further, in the case where a desired reduction amount is rolled with a small reduction amount for each pass, the number of passes increases, so that the chance of receiving disturbances that impair stability increases.

That is, conventionally, it was thought that the rolling reduction would be unstable if the rolling reduction per pass was increased, but in fact it was not so, but the rolling reduction was unstable because the rolling reduction per pass was small. It is.

According to the above factor analysis, as described above, after the end 41 of the material to be rolled comes into contact with the bottom of the die, if a further large reduction is applied and rolling is performed so as to cause a large distortion, the lateral length of the flange portion is reduced. It was found that rolling was stable even if there was a difference in the rolling distortion on the left and right sides of the flange due to unevenness and the like.
Because, as shown in FIG. 4, if the rolling strain is made larger than the strain (about 0.15 in FIG. 4) at which the rate of change of the deformation resistance of the material to be rolled saturates, the rolling strain on the left and right of the flange portion is reduced. Even if there is some difference, the difference in deformation resistance is small, and the rolling counterforce P1 on the left and right sides of the flange acting on the bottom of the die
, P2 are not different.

That is, it is desirable to satisfy the following conditions in order to secure rolling stability. ln ((Hs + ΔWe) / Hs) ≧ 0.15

Further, in the flange forming and rolling of the present invention,
Since processing is applied only to the end of the material to be rolled, stretching by rolling is extremely small at 5% or less, and the thickness of the flange portion increases efficiently with respect to the reduction amount of 2 × ΔWe, and has the following relationship. ln (T2 / t2) = α × ln ((Hs + ΔWe) / Hs) α = 0.9 to 0.6 t2; Flange thickness before rolling T2; Flange thickness after rolling Hs; Protrusion height 2 × ΔWe; amount

Embodiment 2 Next, the protrusion 1 shown in FIG.
By changing the angle 2xA of the apex angle of b and the angle B of the bottom of the hole type,
The relationship between the angle 2 × A of the apex angle of the protrusion 1b, the angle B of the hole-shaped bottom, and the increase in the thickness of the flange portion was investigated using the angle G = A + B as a parameter.

FIG. 6 shows the results of this investigation, with the vertical axis representing the flange thickness distortion and the horizontal axis representing the angle G = A + B. As can be seen from FIG. 6, as the angle G increases, the wall thickening distortion of the flange gradually decreases to about 45 °.
When the angle exceeds 0 °, the reduction of the wall thickening distortion of the flange becomes large.
In order to realize an efficient increase in the thickness of the flange portion, it has been found that it is desirable that the sum of the angle of the half of the apex angle of the projection 1b and the angle of the bottom of the hole is about 45 °. Was.

Embodiment 3 FIG. 7 is an explanatory diagram of the third embodiment, and shows a hole shape in which the hole-shaped protrusions having no side wall shown in the first embodiment are used as the side walls of the adjacent hole shape. Hereinafter, Embodiment 3 will be described with reference to FIG. In this example, the present invention is applied to a case where a slab 30 is used as a raw material to form and roll a crude steel slab for H-section steel.

In the third embodiment, a first-stage die 62 for forming a flange portion with an interruption at the end surface of the slab.
And a second-stage die 1 (only the protrusion 1b having no side wall) in which the interruption of the material to be rolled by the die 62 is enlarged to increase the thickness of the flange while forming the flange. (The mold described in the first embodiment), a third mold 64 for expanding and edging a flange portion having the projection 1b of the mold 1 as a side wall, and a substantially H-shaped web mainly reduced in thickness. The hole mold 65 of the fourth stage is used.

The first, third, and fourth steps are performed in the same manner as in the conventional example, and the second step is performed in the same manner as in the first embodiment.

In the present embodiment, the mold 1 at the second stage does not have a side wall, and the projection 1b of the mold 1 is used as one side wall of the mold 64 at the third stage. Therefore, the roll body length used as a hole type becomes shorter, conversely,
The shaping of large-sized coarse slabs becomes possible. FIG.
In the conventional method shown in FIG. 1, since the side wall 63 is required for the die 63 corresponding to the die 1 of the third embodiment, a large-size rough type which fully uses the roll body length as shown in FIG. The shaping of the shaped steel slab is not possible because the hole mold cannot be inserted in the same roll body length as in the present invention.

[0037]

EXAMPLE 1 A rectangular slab 30 having a thickness of 250 mm and a width of 1100 mm was used as a material, and molding and rolling were performed using a die 1 of the present invention shown in FIG. 8 and a die 63 (see FIG. 11) of a conventional example as a comparative example. Carried out. The rolling conditions were the same until the flange end of the material to be rolled came in contact with the bottom of the die, and the subsequent rolling schedule was performed under the conditions shown in Table 2. Table 2 also shows the results.

[0038]

[Table 2]

As shown in Table 2, in the case of the comparative example,
In addition to wobbling during rolling, the thickness of the flange portion was uneven at four locations, while the rolling of the rolling schedule of the present invention was stable and the thickness of the flange portion was uneven at four locations. Was also small. Example 1
Thus, the effect of the present invention was demonstrated.

Example 2 A slab having a thickness of 250 mm and a width of 1300 mm was used as a raw material, and was subjected to rolling in the same manner as in Example 1 by using a hole type (a) of the present invention shown in FIG. 9 and a hole type (b) different from the present invention. After the flange end of the material came into contact with the groove bottom, modeling rolling was performed according to the rolling schedule shown in Table 3. Table 3 also shows the results.

[0041]

[Table 3]

In both cases, the rolling stability was good,
Although the width of the end portion of the material to be rolled was increased in the comparative groove rolling, the increase in the thickness of the flange portion was insufficient, and the difference from the present invention in this point was clearly understood. That is, in the present invention, it is possible to form a flange having a thickness of 1/2 or more of the slab thickness, which has been difficult in the related art. It was secured at the end. From the above, it was proved that the shape of the hole shown in the second embodiment was effective in increasing the thickness of the slab.

[0043]

Since the present invention is configured as described above, it has the following effects.

The flange portion of the material to be rolled is interrupted and rolled by using a shaping die having a projection, and after the end of the material to be rolled comes into contact with the bottom of the shaping die of the shaping die, the material to be rolled is removed. Since the rolling is performed by further reducing the rolling without restraining both sides of the end, the flange thickness can be made larger than 1/2 of the slab thickness in the rough rolling step. This makes it possible to manufacture large-sized section steel from slabs of the same thickness.

In addition, when a further reduction is performed after the end of the material to be rolled is brought into contact with the bottom of the grooved mold, a one-pass reduction is more than a strain that causes the rate of change in the deformation resistance of the material to be rolled to be saturated. Was performed with the reduction amount that causes
Efficiency and rolling stability improved.

Furthermore, since the sum of the angle of the half of the apex angle of the projection and the angle of the bottom of the groove is 45 ° or less, the thickness of the flange can be effectively increased.

Further, since the projections of the molding die are used as the side walls of the adjacent die, the large body size of the rough shaped steel slab can be formed by effectively utilizing the roll body length. Becomes

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a groove type used in an embodiment of the present invention.

FIG. 2 Flange thickening strain εfw under condition 4 in Table 4
FIG. 4 is a diagram showing a relationship between (vertical axis) and reduction (2 × ΔWe) (horizontal axis).

FIG. 3 is an explanatory diagram of a theoretical analysis according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between strain (horizontal axis) and deformation resistance (vertical axis).

FIG. 5 is an explanatory diagram of Embodiment 2 of the present invention.

FIG. 6 is an explanatory diagram of a change in a flange thickness increasing strain in the second embodiment of the present invention.

FIG. 7 is an explanatory diagram of Embodiment 3 of the present invention.

FIG. 8 is an explanatory diagram of the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of Embodiment 2 of the present invention.

FIG. 10 is a view schematically showing a hot rolling process of a section steel such as an H section steel.

FIG. 11 is an explanatory view of a conventional rolling method.

FIG. 12 is an explanatory diagram of a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hole type 1b Projection part 40 Material to be rolled 41 End part of material to be rolled

Claims (4)

[Claims] In a step of forming a flange portion of a material to be rolled in rough rolling in hot rolling, the flange portion of the material to be rolled is interrupted and rolled using a molding die having a projection, and the material to be rolled is formed. A method of rolling a crude steel slab, characterized in that, after an end of the roll comes into contact with the bottom of the molding die, the material to be rolled is rolled without further restraining both ends of the end. 2. The one-pass reduction when the end of the material to be rolled is further reduced after the end of the material comes into contact with the bottom of the die is larger than the strain at which the rate of change of the deformation resistance of the material to be rolled saturates. 2. The method for rolling a crude steel slab according to claim 1, wherein the rolling is performed with a reduction amount that causes distortion. 3. The shaping die according to claim 1, wherein the shaping die has a vertex angle of 1 / of the protrusion.
3. The method according to claim 1, wherein the sum of the angle of (2) and the angle of the groove bottom is 45 ° or less. 4. The method according to claim 1, wherein the projections of the molding die are used as side walls of an adjacent die.