JPS6215281B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a section steel, and aims to provide a method for producing a section steel from a continuously cast slab, which can effectively suppress the occurrence of cropping at both ends in the longitudinal direction. As a method of manufacturing steel sections such as H-shaped steel and channel steel, slabs obtained by continuous casting are cut into predetermined lengths to produce blooms, beam blanks, etc., and the steel slabs are heated. However, a method is known in which this is rolled into a section steel through rough rolling, intermediate rolling, finishing rolling, etc. Figure 1 shows an example of the arrangement of such a rolling line, where 1 is a heating furnace, 2 is a rough rolling mill, 3 and 4 are intermediate rolling mills, a rough universal rolling mill and an edger rolling mill, and 5 is a finishing universal mill. This is a rolling mill, and the rolled material that has been rolled by these mills is sawed into predetermined lengths by a saw cutter 6.
However, in this type of rolling, crops occur at both ends of the rolled material in the longitudinal direction due to unbalanced rolling (web rolling ratio > flange rolling ratio).
This poses a major problem in that it leads to a decrease in the yield of shaped steel manufacturing. Figures 2A and 2B show the occurrence of cropping in H-section steel and channel steel. As shown in Fig. 3, the occurrence of this crop A tends to be particularly noticeable during the rough rolling stage where the unbalance of the reduction mentioned above is large. This can cause troubles such as defective biting in the next process such as cutting, etc. Therefore, conventionally, as shown in Fig. 1, an intermediate saw 7 (tang cut saw) is installed at the rear of the rough rolling mill 2. The reality is that unless measures are taken to cut off the crops before rolling, smooth operation of the line cannot be expected. The present invention was devised in view of the above circumstances, and its basic feature is that restraining members are placed around the slab at appropriate intervals in the longitudinal direction of the slab obtained by continuous casting. By performing preforming by compressing with a jig through the window hole of the restraining member while restraining the part, a recess corresponding to the desired shape of the steel section is formed at the part that receives the web rolling during the rolling stage. is formed over a predetermined length, and this slab is sequentially cut at approximately the central position in the longitudinal direction of the recessed portion to cut out a steel slab having recessed portions at both ends in the longitudinal direction, and this steel slab is rolled into a section steel. In this way, by forming concave portions at the parts of both ends of the steel billet that are subject to web reduction during the rolling stage, the internal reduction balance within the cross section at both ends of the steel billet during the rolling stage is made uniform. The occurrence of cropping can be effectively reduced. In consideration of the fact that, in the manufacture of section steel, the balance of the cross-sectional reduction at both ends of a steel piece, that is, the condition of web reduction ratio > flange reduction ratio, is the cause of cropping, the present invention has developed an uneven cross-sectional reduction balance. In order to solve this problem, the steel slab obtained from continuous casting is preformed so that both ends of the slab in the longitudinal direction after being cut have recesses created by compression processing. Therefore, the present invention is applicable to various types of steel sections such as H-section steel, channel steel, I-section steel, and T-section steel, in which the web reduction ratio exceeds the flange reduction ratio during manufacture. I can do it. Therefore, to explain the preforming method using compression processing in more detail, this preforming is performed on an uncut slab obtained from continuous casting. In addition, this preforming is performed at appropriate intervals in the longitudinal direction of the continuous cast piece that is continuously manufactured, and over a predetermined length, and the interval corresponds to the length of the steel piece to be cut. do. In the method of the present invention, after such preforming, the slab is cut at a position approximately in the longitudinal direction of the recess formed by this preforming. It can be said that the position corresponds to a predetermined position where the slab is to be cut, and more specifically, the preforming is performed so that the approximate center position in the longitudinal direction of the concave portion is at the scheduled cutting position of the slab. It is necessary to make sure that it is applied accordingly. Therefore, the specific location and degree of formation of the recessed portion by such preforming are determined depending on the desired shape of the steel section to be rolled. For example, in the case of H-shaped steel, it is preferable to provide recesses at the top and bottom of the slab, and in the case of channel steel, it is preferable to provide recesses at either the top or bottom of both ends of the slab. ,
The present invention is not necessarily limited to this, but in short, it is sufficient to at least press the portion of the slab that receives web rolling during the rolling step to form a concave portion. Further, since the recessed portion is cut approximately at its longitudinal center position as described above, it needs to have a predetermined length. Further, in the present invention, the above-mentioned preforming is performed by compressing the portion to be processed using a jig through a window hole in the restraining member while restraining the periphery of the portion to be processed by a restraining member. This is because when pressure processing is performed without restraining the surrounding area of the slab, the excess metal due to the compression flows in the width direction of the slab, resulting in poor end shape of the slab and hindering the rolling process, which is the next process. This is because, in the present invention, the periphery of the processed portion is restrained and compression processing is performed so that this excess material does not flow in the width direction. The slab, which has been preformed at appropriate intervals in the longitudinal direction, is then cut into steel slabs of a predetermined length by a cutting device.
The cutting position of this slab is approximately the center position in the longitudinal direction of the recessed portion, and is also the predetermined cut portion as described above. The steel piece cut out in this manner has concave portions at both ends in the longitudinal direction, and the steel piece is subsequently subjected to rolling starting from rough rolling to produce a section steel. However, during this rolling, since recesses are provided at the parts of both ends of the billet that receive web rolling, the web rolling reduction rate is reduced, and this results in a balance of cross-sectional reduction at both ends of the billet. is evened out, thereby effectively reducing the occurrence of cropping. In addition,
The above-mentioned preforming before rolling can be carried out in the cold state, but when carried out in the cold state, the deformation resistance of the steel billet is large, and therefore it is preferable to carry out the preforming in the hot state. Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows an embodiment in which the present invention is applied to the manufacture of H-beam steel. That is, portions of the continuously cast slab 8 shown in FIG. 4A are compressed at appropriate intervals in the longitudinal direction using jigs 9 and 9' as shown in FIG. 4B. The area to be compressed is the area that receives web reduction in the rolling stage, and in the case of H-beam steel like the one in this example, the central part in the width direction of the slab 8 is compressed from above and below at the same time, as shown in Figure C. Recesses B and B' are formed symmetrically above and below the slab 8 at appropriate intervals. Further, in the figure, C indicates a portion of the slab to be cut, and the compression processing using the jigs 9 and 9' must be performed so that the approximately center in the longitudinal direction thereof is placed on the portion C to be cut. Therefore, the above-described compression processing is performed while the periphery of the compression processing portion is restrained. That is, if the slab 8 is simply compressed with the jigs 9 and 9', the end shape of the slab after cutting will become defective due to the flow of the excess thickness of the pressed portion in the width direction of the slab, as shown in FIG. It is from. FIGS. 6 to 8 show the situation in which compression processing is performed while being restrained. That is, the portion of the slab 8 to be compressed is placed on its upper and lower surfaces 81, 82 and both side surfaces 83, 83.
The window holes 10 provided on the upper and lower surfaces of the restraining member 10 are restrained by the restraining portion 10 that is in close contact with the
1,101', the slab 8 is compressed using compression jigs 9, 9', and by doing this, the excess thickness at the compressed part flows in the longitudinal direction of the slab, thereby preventing shape defects. This is prevented, and the slab 8 is preformed into the shape shown in FIG. 4C. In this way, by preforming, the concave portion B,
The cast slab 8 with B' formed therein is cut at a predetermined cut portion C located approximately in the longitudinal center of the concave portions B and B', thereby creating concave portions B and B at both longitudinal ends, respectively. A steel piece 11 having a diameter of 1 is cut out.
Then, the steel piece 11 is subsequently rolled into a section steel through a rolling process starting with rough rolling. In addition,
Compression by the compression jigs 9, 9' is performed using an appropriate driving force such as electric or hydraulic power. The embodiments described above are cases in which the method of the present invention is applied to the production of H-section steel, but the procedure similar to the above embodiments can also be used when producing other section steels. For example, when manufacturing channel steel, the upper and lower parts of the slab may be compressed and preformed to provide recesses at the top and bottom, as described above, but generally only the upper part of the slab is processed. In this method, the steel is preformed by compression to form a concave portion only in the upper part, and then rolled. By doing this, it is possible to manufacture a channel steel with less cropping. It goes without saying that the preforming in this case is also performed with the periphery of the slab restrained. In addition, although the above embodiment described the case where the steel piece cut out from the cast slab is a bloom, the method of the present invention can also be applied to other cases where the steel piece cut out is a beam blank or the like. . The table below shows the yield improvement effect when the method of the present invention is applied to the production of H-section steel, and specifies the dimensional conditions of a, b, and c of the recessed part as shown in Figure 9. This was carried out as follows.

[Table] As is clear from the above, according to the present invention, the generation of crops is appropriately suppressed, so that the yield can be improved by 0.3 to 0.4% by weight compared to products manufactured by conventional methods. It is something. According to the manufacturing method of the present invention described above, when a steel slab obtained from a continuously cast slab is rolled into a section steel, unevenness in the cross-sectional reduction balance that occurs at both ends of the steel slab in the longitudinal direction is eliminated, and uniform rolling reduction is achieved. Since the steel slab can be rolled into a section steel under the same conditions, it is possible to properly prevent the occurrence of cropping at both longitudinal ends of the section steel, thereby improving the yield.
It has excellent effects such as enabling smooth operation of the rolling line since dangers such as jamming defects can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional shape steel rolling line. Figures 2A and 2B are explanatory diagrams showing the occurrence of cropping in a section steel. FIG. 3 is an explanatory diagram showing the occurrence of crops at the end of rough rolling. FIGS. 4A to 4C are explanatory diagrams showing the preforming process in the present invention. FIG. 5 is an explanatory diagram showing a situation where the end shape is defective when preforming is performed without restraint.
6 to 8 show the preforming situation in the present invention more specifically, FIG. 6 is a perspective view, FIG. 7 is a sectional view taken along the line in FIG. 6, and FIG. 8 is a similar view. FIG. 6 is a sectional view taken along the line in FIG. FIG. 9 is an explanatory diagram for defining the dimensional conditions of the recessed portion. In the figure, 8 is a slab, 9 and 9' are jigs, and 10
11 is a restraining member, 11 is a steel piece, and B and B' are concave portions.

Claims (1)

[Claims] 1 In a method in which a slab obtained by continuous casting is cut into steel slabs of a predetermined length and then rolled into sections, restraining members are placed around the slab at appropriate intervals in the longitudinal direction of the slab. By performing preforming by compression processing using a jig through the window hole of the restraining member while restraining the part, a concave portion corresponding to the desired shape of the steel section is created at the part that is subjected to web rolling during the rolling stage of the relevant part. A steel slab is formed over a predetermined length, and this slab is sequentially cut at approximately the central position in the longitudinal direction of the recessed portion to cut out a steel slab having recessed portions at both ends in the longitudinal direction, and this steel slab is rolled into a section steel. A method for rolling section steel characterized by: