JP4677921B2 - Rolling method for H-section steel - Google Patents

Description

  The present invention relates to a method for rolling H-section steel.

  In general, as shown in FIG. 6, for example, hot rolling of H-section steel is performed by using raw steel slabs extracted from a heating furnace 11 as a rough mill 12, a rough universal mill group 13, an intermediate universal mill group 14, and a finishing universal mill 15. It is performed by rolling in the order. As the material steel slab, a steel slab having a rectangular cross section (slab), a steel slab having a square cross section (bloom), or a steel slab having a substantially H cross section (beam blank) is used. Then, the raw steel slab is shaped into a predetermined coarse steel slab for H-shaped steel by a coarse mill 12 in which one or a plurality of modeling hole molds are engraved. The rough shaped steel slab formed by the coarse mill 12 is subjected to reciprocal rolling of a plurality of passes by the coarse unibar mill group 13 and then by the intermediate universal mill group 14 and then formed by the finish unibar mill 15 in one pass. And rolled into an H-shaped steel (see, for example, Patent Document 1).

Incidentally, FIG. 2 shows the cross-sectional shape of the H-section steel that has been rolled into a product, and includes a web height H, a flange width B, a web thickness t1, and a flange thickness t2.
JP 2000-233201 A

  In the hot rolling method for H-section steel as described above, when a steel piece (bloom) having a square cross section as shown in FIG. 3 is used as a material steel piece, the outer flange surface of the product as shown in FIG. A crimped ridge 21 may occur. For this reason, a care work for removing the crimping bar 21 after rolling is required, leading to a decrease in manufacturing efficiency and an increase in manufacturing cost.

  The present invention has been made to solve the above-described problems, and is generated on the outer surface of a flange when an H-section steel is manufactured by hot rolling using a square-section steel slab (bloom) as a raw material slab. An object of the present invention is to provide a method for rolling H-section steel that can appropriately prevent crimping defects.

  In order to solve the above problems, the present invention has the following features.

[1] Using a square cross-section steel slab as a raw steel slab, a predetermined coarse steel slab for H-shaped steel is modeled by one coarse mill in which one or a plurality of modeling hole molds are engraved. When manufacturing H-shaped steel from hot rolled shape steel slab by hot rolling, the ratio of the thickness T of the square section steel slab to the product flange width B of the H-shaped steel, the dimensional accuracy of the product flange width The ratio T / B that does not cause biting in the shaping hole mold of the rough mill is arranged in advance, and rolling is performed using a square-section steel slab having the ratio T / B. A rolling method for H-section steel.

  In the present invention, when a H-section steel is manufactured by hot rolling using a square cross-section steel slab as a raw steel slab, it is possible to appropriately prevent crimping flaws generated on the outer surface of the flange. As a result, the manufacturing efficiency can be improved and the manufacturing cost can be reduced.

  The present inventors have investigated and investigated the cause of the occurrence of crimping flaws on the outer surface of the flange of a product when a H-section steel is manufactured by hot rolling using a square-section steel slab (rough angle) as a material steel slab. I did it. As a result, in the modeling hole mold 12a of the rough mill 12 shown as an example in FIG. Therefore, it was estimated that the biting 22 was caused by the crimping bar 21.

  Therefore, the present inventors have studied a method for suppressing the occurrence of the biting 22 in the modeling hole mold 12a, and as a result, in order to suppress the occurrence of the biting 22, the square cross-section steel piece (rough angle) It came to the idea that the thickness should be an appropriate ratio to the flange width of the H-shaped steel.

  That is, normally, the square cross-section steel piece (rough angle) shown in FIG. 3 has a rough angle thickness T which is a vertical dimension when the rough angle is rolled by the shaping hole mold 12a and a horizontal dimension. The rough angle width L is determined in relation to the product dimensions, but the rough angle thickness T is determined in the direction of increasing the thickness from the viewpoint of stably securing the formability of the flange and the dimensional accuracy of the flange width. Therefore, it was determined that this led to the occurrence of biting 22 in the modeling hole mold 12a.

  Therefore, by setting the rough angle thickness T to an appropriate ratio with respect to the product flange width B, the biting 22 in the shaping hole mold 12a is suppressed while ensuring the formability of the flange and the dimensional accuracy of the flange width. Therefore, it was considered that the generation of the crimping ridge 21 can be prevented.

  FIG. 1 shows an embodiment of the present invention in which the relationship between the rough angle thickness T and the product flange width B is arranged based on the above concept.

  In FIG. 1, a region below the straight line T = 1.3B (that is, a region where T <1.3B) is a region where the dimensional accuracy of the flange width of the product cannot be ensured. On the other hand, the region above the straight line T = 1.5B (that is, the region where T> 1.5B) is a region where biting occurs in the modeling hole mold (a region where a square in FIG. 1 is located). In contrast, the region sandwiched between the straight line T = 1.3B and the straight line T = 1.5B (that is, the region of 1.3B ≦ T ≦ 1.5B) ensures the dimensional accuracy of the product flange width. On the other hand, this is a region where the biting 22 in the modeling hole mold 12a can be prevented (a region where the mark ◆ is located in FIG. 1).

  From the above, in this embodiment, when the H-section steel is manufactured by hot rolling using the square-section steel slab (rough angle) as the raw steel slab, the thickness T of the rough angle is set to the flange width of the H-section steel. 1.3 to 1.5 times B (that is, T / B = 1.3 to 1.5).

  As a result, while ensuring the dimensional accuracy of the flange width of the product, it is possible to prevent biting in the shaping hole mold and appropriately prevent the occurrence of flange crimping flaws. As a result, the manufacturing efficiency can be improved and the manufacturing cost can be reduced.

  For H-shaped steel with a web height H of 300 mm and a flange width B of 150 mm, as a conventional example, a rough angle at which the rough angle height T is 1.63 times the flange width B (T / B = 1.63). When compared with the case of rolling using a rough angle where the rough angle height T is 1.50 times the flange width B (T / B = 1.50).

  As a result, the occurrence rate of flange crimping flaws was 1% or more in the conventional example, whereas the occurrence of flange crimping flaws was completely eliminated in the present invention example.

It is a figure which shows the relationship between the rough angle thickness and product flange width in one Embodiment of this invention. It is sectional drawing of H-section steel. It is sectional drawing of a square steel piece (rough angle). It is explanatory drawing of the biting in a modeling hole type | mold. It is explanatory drawing of the crimping tack of a flange. It is an arrangement plan of rolling equipment of H section steel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Heating furnace 12 Coarse mill 12a Modeling hole type 13 Coarse universal mill group 14 Intermediate universal mill group 15 Finish universal mill 21 Crimp rod 22 Biting out

Claims (1)

Using a square cross-section steel slab as a raw steel slab, it is formed into a predetermined H-section steel rough slab by one coarse mill in which one or a plurality of modeling hole molds are engraved, and for the H-section steel When manufacturing H-section steel from rough section by hot rolling , the dimensional accuracy of the product flange width is ensured with respect to the ratio of the thickness T of the square-section section to the product flange width B of the H-section steel. On the other hand, a ratio T / B in which biting does not occur in the shaping hole mold of the rough mill is arranged in advance, and rolling is performed using a square section steel slab having the ratio T / B. Rolling method.

Images