JP4089543B2 - Universal rolling method for narrow flange width H-section steel - Google Patents

Description

  The present invention relates to a universal rolling method for narrow flange width H-section steel whose flange width is smaller than 1/4 of the web height, and more particularly to a rolling setting method for the universal rolling.

  A shape steel having a flange such as an H-shape steel is generally manufactured in a rolling line having a breakdown rolling mill, a universal rolling mill, and an edger rolling mill. The material steel slab that has come out of the heating furnace is first rolled into a shape suitable for the intended product dimensions by a breakdown rolling mill BD that is a double rolling mill. Subsequently, in the rough universal rolling mill group including the rough universal rolling mill U and the edger rolling mill E, the thickness is reduced and the flange end is formed. Furthermore, a flange is shape | molded at right angle by the finishing universal rolling mill F, and becomes an H-shaped product.

  The conventional H-section steel generally has a dimensional ratio that the flange width is 1/3 or more of the web height. Particularly, in the case of a large-section H-section steel having a web height of 500 mm or more, it is more than 1/4 of the web height. There are very few product examples of H-section steel having a small flange width. In recent years, an increasing number of cases where two strips are welded to form a T-shaped steel and used as a reinforcing material for a hull of a large ship. In order to obtain the cross-sectional performance required as a reinforcing material for such a T-shaped steel for shipbuilding applications, an elongated cross-sectional shape having a web height of about 2 to 5 times the flange width is suitable. In the method of welding two strips, the ratio between the web height and the flange width can be widely changed by arbitrarily selecting the plate width of each strip.

  However, in the T-shaped steel manufactured by welding, joint failure may occur in the welded portion, and the reliability when used as a reinforcing material is inferior. Moreover, since the surface of the weld has irregularities and is not a smooth surface, there is a risk of stress concentration. Furthermore, since the heat applied to the steel material by welding adversely affects the material, there is a possibility that the material is deteriorated.

  On the other hand, when manufacturing a T-shaped steel by cutting an H-shaped steel manufactured by rolling at the center of the web, the web height with respect to the flange width of the H-shaped steel is usually three times or less. With such an H-shaped steel, a T-shaped steel desirable as a hull reinforcing material could not be obtained. On the other hand, for example, Japanese Patent Laid-Open No. 2002-301501 (Patent Document 1) discloses that (web height / flange width) ≧ 4.0 (T-shaped steel web height / flange width is 2.0 to 3). 5) is produced, and the I-shaped steel is divided into two in the longitudinal direction to obtain a T-shaped steel.

JP 2002-301501 A

  In said Unexamined-Japanese-Patent No. 2002-301501 (patent document 1), although I shape steel of (web height / flange width)> = 4.0 is manufactured using a universal rolling mill, Although it is described that the upper and lower, left and right guides prevent warping and bending, the web and flange reduction for universal rolling of a shape steel whose web height is larger than the flange width. No conditions are disclosed. Although it is extremely important to appropriately select the rolling conditions for each pass in rolling, such a method has not been disclosed in the above prior art (Patent Document 1).

  The present invention has been made to solve such problems, and provides a method for producing a narrow flange width H-section steel that can stably produce a narrow flange width H-section steel. With the goal.

  The inventors of the present invention have disclosed a narrow flange having a flange width smaller than ¼ of the web height, in which the flange and the web are integrally manufactured, and the flange width is a T-shaped steel material smaller than ½ of the web height. In order to develop a method for efficiently producing wide H-shaped steels by universal rolling, many numerical experiments and rolling experiments using model rolling mills, as well as rolling tests with actual machines, were conducted and various studies were repeated. It came to invent the rolling method of this invention which has such a characteristic.

In the universal rolling method according to the present invention, a raw steel slab is rolled into a substantially H shape to form a rough steel slab, and then the web thickness and the flange thickness are reduced by a universal rolling mill, and the flange width is reduced by an edger rolling mill. When rolling a narrow flange width H-section steel having a flange width smaller than 1/4 of the web height, the flange leg length at the start of universal rolling and the total web and flange reduction strain are as follows: To do.
0.4 ≦ HE _ini / HE _p ≦ 1.0
1.0 ≦ ln (tw _ini / tw _p ) / ln (tf _ini / tf _p ) ≦ 1.1
Here, HE _ini , tf _ini , and tw _ini are the flange leg length, flange thickness, and web thickness in the cross section of the rough steel slab at the start of universal rolling, respectively, and HE _p , tf _p , and tw _p are narrow flanges, respectively. It is the flange leg length, flange thickness, and web thickness in the product cross section of the width H-section steel. Preferably, the appropriate range of the rolling balance (λ _f −λ _w ) of each universal rolling pass is set as the range of the following equation.
-0.02 ≦ λ _f −λ _w ≦ 0.02

  In the present invention, by reducing the amount of web and flange reduction in universal rolling within the range of the above equation, a narrow flange width H-section steel having a flange width of ¼ or less of the web height is stably produced. It is possible.

  FIG. 1 is an overall configuration diagram illustrating an example of a shape steel rolling facility to which a universal rolling method of a narrow flange width H-shaped steel according to an embodiment of the present invention is applied. The raw steel slab from the heating furnace 10 is subjected to a rough steel slab having a substantially H cross-sectional shape suitable for the product size of the target narrow flange width H-section steel by a double breakdown rolling mill (BD mill) 11 ( (See FIG. 6). Subsequently, rolling is performed in a state where the flange is inclined in a rough universal rolling mill group (R mill) 14 including a rough universal rolling mill (U) 12 and an edger rolling mill (E) 13, and the thickness is reduced. The flange end is formed. Further, a flange is formed at a right angle by a finishing universal rolling mill (F mill) 16 to form an H-shaped cross-sectional shape and sent to the cooling bed 17.

  FIG. 4 is a view showing an example of a cross-sectional shape of a narrow flange width H-section steel targeted by the present embodiment, and FIG. 5 is a T-section steel manufactured by cutting the narrow flange width H-section steel of FIG. It is the figure which showed an example. As shown in FIG. 4, since the flange width B is smaller than ¼ of the web height H, it is a very horizontally long H-section steel. By cutting the web center of the narrow flange width H-section steel in the longitudinal direction, a T-section steel as illustrated in FIG. 5 can be easily manufactured.

  The inventors have investigated and studied the rolling conditions suitable for the narrow flange width H-section steel, paying attention to the universal rolling process in which the product shape is made from the rough shaped steel slab in the above-described process. As a result, in the universal rolling of the narrow flange width H-section steel, it was found that a very large flange width expansion about twice that of the conventional H-section steel occurs.

FIG. 2 is a characteristic diagram showing the result of the flange width expansion obtained by experiment. The flange width spread on the vertical axis is the flange width spread strain λ _B defined by the following equation.
λ _B = ln (B ₁ / B ₀ ) (Formula 1)
Where B ₀ : flange width before universal rolling,
B ₁ : Flange width after universal rolling. The horizontal axis is the reduction balance, which is a parameter indicating the difference in sheet thickness reduction conditions between the flange and the web. The reduction balance λ _f −λ _w is defined by the following equation.
λ _f −λ _w = ln ( _{t f 0} / _{t f 1} ) −ln (tw ₀ / tw ₁ ) (Equation 2)
Where tf ₀ : flange thickness before universal rolling,
tf ₁ : Flange thickness after universal rolling,
tw ₀ : web thickness before universal rolling,
tw ₁ : Web thickness after universal rolling.

  The characteristic diagram of FIG. 2 shows the results for H600 mm (web height) × 300 mm (flange width) as a conventional H-section steel and H600 mm (web height) × 125 mm (flange width) as a narrow flange width H-section steel. It is plotted. With a narrow flange width of H600x125, the flange width spread distortion changes greatly with changes in the rolling balance, and when the relationship between the two is linearly approximated, the slope is about 0.58, twice that of H600x300. It is about. Also, the section with respect to the Y-axis where the rolling balance is 0 is slightly larger in the narrow flange width H-section steel. From the above, when rolling with the same reduction balance, it can be seen that the narrow flange width H-section steel has a flange width spread twice or more that of the conventional size H-section steel.

  The narrow flange width H-shaped steel has the following problems when the flange width spread is large. In the universal rolling, even if the flange width does not change, the web thickness is reduced after rolling. Therefore, the flange leg length HE, which is the distance between the flange tip and the web surface, is increased by half the web thickness reduction amount. Further, when a large width spread occurs in the universal rolling, the flange leg length increase amount is (web thickness reduction amount + width spread amount) / 2. The edger rolling mill 13 installed adjacent to the universal rolling mill serves to reduce the flange width. If the increase in the flange leg length in universal rolling is not reduced by edger rolling, the flange width becomes larger for each pass and the target dimension cannot be achieved. The amount of reduction in the flange width must be large.

  FIGS. 3A and 3B are views showing the situation of edger rolling and universal rolling when the flange width spread is large. As shown in FIG. 3A, most of the cross-sectional area of the portion reduced by the edger rolling appears as an increase in the flange thickness. Then, in the next universal rolling, as shown in FIG. 3 (B), in order to obtain a target flange thickness, the reduction of the flange thickness must be increased, and the reduction balance becomes large and the flange becomes large. It falls into a vicious circle of widening. In this way, both the edger rolling and the universal rolling increase the reduction of the flange, which increases the wear of the rolling roll, and causes the occurrence of surface flaws on the rolled material and an increase in rolling power, increasing the manufacturing cost and quality. Problems such as lowering of the level occur.

In order to solve the problem in universal rolling peculiar to such a narrow flange width H-shaped steel, the present inventors have studied for the purpose of optimizing the rolling conditions of the web and flange of universal rolling, and universal rolling. It has been found that by setting the flange leg length at the start and the total web and flange reduction amount within the following ranges, a product with good dimensional accuracy can be rolled while suppressing an excessive expansion of the flange width.
0.4 ≦ HE _ini / HE _p ≦ 1.0 (Equation 3)
1.0 ≦ ln (tw _ini / tw _p ) / ln (tf _ini / tf _p ) ≦ 1.1 (Formula 4)
Here, HE _ini , tf _ini , and tw _ini are the flange leg length, the flange thickness, and the web thickness in the cross section of the rough steel slab at the start of universal rolling after the rough shaping rolling shown in FIG. HE _p , tf _p , and tw _p are the flange leg length, flange thickness, and web thickness in the cross section of the narrow flange width H-section steel shown in FIG.

  The reason why the flange leg length at the start of universal rolling is less than or equal to the flange leg length of the product is that edger rolling is performed by reducing the flange width at the start of rolling in advance in consideration of the characteristics of universal rolling that the flange width spread is large. This is to reduce the flange width reduction at, thereby suppressing excessive flange width spread. However, the flange width at the start of universal rolling cannot be made extremely small. To obtain the minimum flange width that satisfies the dimensional tolerance of the product, the flange leg length at the start of universal rolling is 0.4 times the product flange leg length. It is necessary to do it above. Also, if the flange leg length is small at the start of universal rolling, there is a higher risk of the flange portion being caught between horizontal rolls and damaging the roll, so the flange leg length at the start of universal rolling is preferably 0.7 times the product leg length or more. Should.

The reason for defining the relationship between the total reduction amount of the web and the flange at the start of universal rolling as shown in (Equation 4) is as follows. It can be seen from the characteristic diagram of FIG. 2 that the rolling balance (λ _f −λ _w ) should be reduced in order to suppress the flange width spread. Therefore, by making ln (tw _ini / tw _p ), which is the total rolling strain of the web in universal rolling, larger than ln (tf _ini / tf _p ), which is the total rolling strain of the flange, the rolling balance in the universal rolling process ( λ _f −λ _w ) can be set to 0 or less on average. If the rolling balance is 0 or less, the flange width will increase little or conversely, so universal rolling will be performed while suppressing the flange width expansion, and products with the target flange thickness and flange width will be manufactured accurately. be able to. If the total web strain is too large compared to the flange total strain, dimensional defects such as insufficient flange width will occur, so ln (tw _ini / tw _p ) will be ln (tf _ini / tf _p ) is preferably 1.1 times or less.

In addition, in order to determine more detailed universal rolling conditions, the present inventors examined a method for optimizing the balance between the universal rolling flange and the web in each pass. In other words, in a narrow flange width H-section steel whose flange width is less than 1/4 of the web height, the appropriate range of the rolling balance (λ _f −λ _w ) of each universal rolling pass can be expressed by the following formulas. Derived from experimental results.
-0.02 ≦ λ _f −λ _w ≦ 0.02 (Formula 5)

  In the range where the rolling balance is larger than 0.02, the width spread in universal rolling becomes positive and the width spread becomes large, which is not preferable. On the other hand, when the reduction balance is less than -0.02, there is a problem that the flange width becomes too small and the flange width cannot be reduced by edger rolling.

  Rolling in the range of the above rolling balance needs to be strictly strictly observed from the initial stage to the middle stage of the universal rolling process in which the flange is relatively thick. On the other hand, in the latter stage of the universal rolling process in which the thickness of the flange is reduced, the effect of increasing the flange thickness due to the reduction of the flange width is reduced. Therefore, rolling is possible even in the range of the reduction balance according to the normal H-section steel. From such knowledge, it was found that it was in the first half of the universal rolling process that it was necessary to limit the range of the rolling balance. However, in this embodiment, the flange leg length HE of the rolled material at the start of universal rolling may be smaller than the flange leg length of the product, and the flange width may not be reduced by edger rolling at the beginning of universal rolling. In such a case, since it is less necessary to suppress the flange width spread, the pass that limits the range of the reduction balance may be between the flange width reduction start pass and the intermediate pass by the edger in the universal rolling process. .

  By the way, the H-section steel whose flange width is smaller than 1/10 of the web height is likely to be rolled in a state where the material to be rolled is shifted to the left and right with respect to the rolls by rough and universal rolling. In reality, mass production is impossible because there is a risk of roll defects caused by rolling the flange portion between horizontal rolls. For this reason, in this embodiment, the narrow flange H-section steel whose flange width is 1/4 to 1/10 of the web height is targeted.

Example 1
As Example 1 of the present invention, a narrow flange width H-section steel was manufactured using the section steel manufacturing facility shown in FIG. Here, the target product dimensions were a web height of 600 mm, a flange width of 125 mm, a flange leg length of 56.5 mm, a web thickness of 12 mm, and a flange thickness of 18 mm. The flange width is 1 / 4.8 of the web height. The material was a continuous cast slab having a rectangular cross section, and the cross sectional dimensions were 900 mm wide and 250 mm thick. This slab was rolled in 11 passes with a plurality of perforations to form a roughly H-shaped rough slab, followed by a total of 15 passes with a rough universal rolling mill and an edger rolling mill, and finally one pass with a finishing universal rolling mill. Was rolled. At this time, the flange leg length in the state of the rough steel slab was the dimension shown in the condition number (1) of Table 1, and was 51 mm, the flange thickness was 120 mm, and the web thickness was 88 mm. Therefore, the total rolling strain of the flange in the universal rolling process was 1.90, and the total rolling strain of the web was 1.99, which satisfied the conditions of (Equation 3) and (Equation 4). As a result of rolling under the above conditions, it was possible to produce a narrow flange width H-section steel having a target thickness, flange width, and web height.

(Example 2)
Next, as Example 2 of the present invention, the pass schedule and the hole shape of the rough shaping rolling were changed so that the flange leg length of the material dimensions was 47 mm, and other dimensions were rough conditions of condition number (2) in Table 1. Universal rolling was performed under the conditions satisfying (Formula 3) and (Formula 4) as a shape steel piece. At this time, the rolling balance λf−λw in each pass of the universal rolling was set to approximately 0, and the rolling was performed under the condition satisfying (Equation 5). A product having a target cross-sectional dimension was obtained under the above conditions.

  Further, in the same rough steel slab size as the rolling of the condition number (2), rolling was performed with a reduction balance of 0.04 in the fifth halfway of the first half of all 16 universal rolling passes. As a result, in the subsequent fifth pass edger rolling, the width of the entry side flange was large, so that the amount of reduction was excessive, the load of edger rolling increased, and the phenomenon that the flange fell to the outside occurred and the rolling became unstable. In such a case, since the flange width of the product fluctuates in the rolling direction and the dimensional accuracy may deteriorate, the reduction balance is set so as to be in the range of (Equation 5) in each universal rolling pass. I found it desirable.

  Furthermore, rolling was performed under other conditions of the present invention in which the dimensions of the rough steel slabs were the values shown in Table 1 (3) and (4). Condition number (3) is when the flange leg length is 0.43 times that of the product and the ratio of the total rolling strain is 1.01, and the rolled product has a flange width 1.9 mm smaller than the target. The tolerance was within ± 2.5 mm. Condition number (4) is when the flange leg length is 0.97 times that of the product and the ratio of the total rolling strain is 1.09. The product after rolling had a flange width of 1.8 mm larger than the target. As in (3) of 1, it was within the dimensional tolerance.

(Comparative example)
On the other hand, as a comparative example, universal rolling was carried out under the rolling conditions as shown in Table 1 (5) to (8). In condition numbers (5) and (6), the flange leg length before the start of rough universal rolling does not satisfy the condition of (Expression 3), and condition numbers (7) and (8) satisfy the condition of (Expression 4). Did not meet. When rolling was performed under these conditions, the result was that the product dimensions could not be rolled as intended. For example, in the case of condition numbers (5) and (7), the flange leg length increases as rough universal rolling proceeds, the flange width reduction amount in edger rolling increases, and the flange thickness after edger rolling also increases. It was. For this reason, the rolling reduction of the flange became substantially large in the next rough universal rolling pass, and the rolling became unstable. In addition, when the finished dimensions of the narrow flange width H-shaped steel were measured, it was found that the flange width was 3 mm larger than the target, which was outside the dimensional tolerance of the product. This is thought to be because the flange leg length increased due to the flange falling to the outside in the late rolling stage when the flange was thin, in addition to the large flange width spread during rolling.

  Further, in the condition numbers (6) and (8), when the product shape of the rolled narrow flange width H-section steel was examined, there was a thickness drop of about 3 mm at the corner of the flange tip, resulting in a defective cross-sectional shape. It was. It is considered that since the total reduction ratio of the flange was made too small relative to the web, the flange width spread was too small, and the flange tip reduction at the edger was insufficient.

  From the above, it has been found that according to the universal rolling method of the present invention, it is possible to accurately finish product dimensions to a target value.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows an example of the shape steel hot rolling equipment with which implementation of this invention is provided. It is a figure which shows the relationship between a rolling balance and flange width expansion. It is a figure which shows the condition of edger rolling and universal rolling when a flange width extension is large. It is the figure which showed an example of the cross-sectional shape of the narrow flange width H-section steel of this invention. It is the figure which showed an example of the cross-sectional shape of the T-section steel manufactured by cut | disconnecting the narrow flange width H-section steel of this invention. It is the figure which showed an example of the cross-sectional shape of the rough steel slab at the time of the start of the universal rolling used for the universal rolling method of this invention.

Explanation of symbols

10: heating furnace, 12: rough universal rolling mill, 13: edger rolling mill, 14: rough universal rolling mill group, 16: finishing universal rolling mill, 17: cooling bed.

Claims (1)

After rolling the raw steel slab into a roughly H-shaped slab, the web thickness and the flange thickness are reduced by a universal rolling mill , the flange width is reduced by an edger rolling mill , and the flange width becomes the web height. On the other hand , when rolling a narrow flange width H-shaped steel having a dimension smaller than 1/4, the flange leg length at the start of universal rolling and the total rolling strain of the web and flange are within the following ranges. .
0.4 ≦ HE _ini / HE _p ≦ 1.0
1.0 ≦ ln (tw _ini / tw _p ) / ln (tf _ini / tf _p ) ≦ 1.1
Here, HE _ini , tf _ini , and tw _ini are the flange leg length, flange thickness, and web thickness in the cross section of the rough steel slab at the start of universal rolling, respectively, and HE _p , tf _p , and tw _p are narrow flanges, respectively. It is the flange leg length, flange thickness, and web thickness in the product cross section of the width H-section steel.

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