JP2011200885A - Method for rolling steel bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the rolling of a plurality of steel bars without deteriorating rolling efficiency regardless of the presence or absence of cooling treatment.SOLUTION: When manufacturing the steel bar by performing the rough rolling of a bloom subjected to continuous casting and then performing finish rolling, a retreating line for retreating a base stock for rolling from the conveying line, is provided on the conveying line for conveying the base stock delivered from a roughing mill to a finishing mill, and as for the base stock for rolling, which requires cooling before the finish rolling, the base stock for rolling is transferred once from the conveying line to the retreating line and necessary cooling is performed on this retreating line. After the base stock for rolling is cooled down to a desired temperature, it is made to return to the conveying line and conveyed to the finishing mill. On the other hand, as for the base stock for rolling which does not require the cooling before the finish rolling, it is made to passing through the conveying line as it is and guided to the finishing mill.

Description

  The present invention relates to a method for rolling steel bars, and in particular, intends to perform an appropriate cooling process on a rolling material without reducing rolling efficiency between rough rolling and finish rolling.

  In conventional steel bar rolling, a heated steel material is roughly rolled, then subjected to intermediate rolling as necessary, and then finished to obtain a product. In such steel bar rolling, it is known that the material of the steel bar can be improved by making the finish rolling a controlled rolling with the temperature regulated.

  For example, as a method for producing non-tempered steel, in Patent Document 1, first stage rolling is performed in a temperature range of 800 to 1100 ° C., then second stage rolling is performed in a temperature range of 650 to 900 ° C., and then cooled. Thus, a technique for improving the low temperature toughness is disclosed. Here, the first stage rolling is considered to be rough rolling, and the second stage rolling is considered to be finish rolling.

  Further, in Patent Document 2, after performing rough rolling and intermediate rolling by heating to 1030 to 1200 ° C, preliminary water cooling is performed as necessary, and then finish rolling is performed in a temperature range of 750 to 850 ° C. Discloses a technique for improving the cold workability of a steel bar.

  In addition, as a method for cooling the steel bar, Patent Document 3 discloses a technique for cooling the steel bar during hot rolling or after hot rolling.

JP-A-5-9576 JP-A-5-171262 JP-A-5-317941

In Patent Document 1 and Patent Document 2 listed above, water cooling or the like is mentioned as a cooling means before finish rolling. However, when controlled rolling is necessary, sufficient cooling cannot be performed, and the temperature of the rolling material can be reduced. In some cases, the amount of descent was insufficient.
In addition, Patent Document 3 discloses a cooling control technique. However, when such control cooling is performed on a conveyance line, cooling for a long time is required, which may hinder subsequent rolling. there were.

  The present invention advantageously solves the above-mentioned problem. When a rolling material retreat line is separately provided in the rolling material conveyance line and a certain cooling time such as controlled cooling is required, this cooling material is used. The purpose of the present invention is to propose a method for rolling a steel bar in which the rolling-inhibiting factors associated with the cooling treatment of the preceding rolled material are removed from the subsequent rolled material by performing the above operation on the retreat line.

That is, the gist configuration of the present invention is as follows.
1. After rolling the continuously cast bloom into a raw material for rolling steel bar, when producing the steel bar by subjecting the rolling material to finish rolling,
In the conveyance line that conveys the rolling material that has exited the rough rolling mill to the finishing rolling mill, a retreat line that retracts the rolling material from the conveyance line is provided,
For the rolling material that needs to be cooled before finish rolling, the rolling material is once transferred from the transfer line to the evacuation line, and necessary cooling is performed in the evacuation line, and the rolling material is cooled to a desired temperature. After that, it is returned to the transport line and transported to the finish rolling mill, while the rolling material that does not require cooling before finish rolling is passed through the transport line as it is and guided to the finish mill. Steel bar rolling method.

2. 2. The method for rolling steel bars according to 1 above, wherein the retreat line is provided in a plurality of rows for each conveyance line.

According to the present invention, a rolling material that requires cooling for a long time can be cooled off-line off the conveyance line, so that sufficient cooling can be performed without being restricted by rolling. .
Moreover, since the subsequent rolling raw material which does not require cooling can be conveyed to a finishing mill as it is, rolling efficiency does not fall.

It is a schematic diagram which shows an example of a suitable rolling equipment used for implementation of this invention. It is detail drawing of an evacuation line.

Hereinafter, the present invention will be specifically described.
Now, in general, when manufacturing steel bars, the raw material bloom is heated to about 1000 to 1200 ° C. in a heating furnace and then subjected to rough rolling. The end temperature of rough rolling is usually about 950 to 1100 ° C. Next, finish rolling is usually performed with a finish rolling completion temperature of about 900 to 1000 ° C. as a target temperature.
In such a rolling process, in order to improve the material such as the toughness of the steel bar, the material temperature at the start of finish rolling is adjusted, and the finish rolling is performed at a lower temperature than normal (for example, 700 to 850 ° C.). Control rolling may be performed.

When performing controlled rolling, depending on the size of the rolling material after rough rolling, it may take a long time to cool. However, if such a cooling process is performed on the transfer line, the rolling material remains in the transfer line for a long time, and thus rolling is continued even if the subsequent rolling material does not necessarily require cooling. Cannot be achieved, resulting in a significant reduction in rolling efficiency.
Therefore, in the present invention, a retreat line is provided in the rolling material conveyance line, and for the rolling material that requires long-time cooling, a separate cooling process is performed on this retreat line. .

FIG. 1 schematically shows an example of rolling equipment suitable for use in the practice of the present invention. In the figure, reference numeral 1 is a continuous cast slab (bloom), 2 is a heating furnace, 3 is a rough rolling mill, 4 is a finish rolling mill, and 5 is a conveying line. 6 is a raw material for rolling bar steel that has undergone rough rolling, and 7 is a product bar steel after finish rolling. Reference numeral 8 denotes a retreat line, and 9 is a cooling facility provided in the retreat line 8.
Usually, the raw material 6 for rolling after rough rolling is conveyed to the finishing mill 4 by the conveying line 5 constituted by the conveying rolls 5a, and is rolled to a desired diameter by the finishing mill 4.

However, when performing controlled rolling for the purpose of improving the material quality of the steel bar, it is necessary to perform finish rolling at a lower temperature than usual, and thus a long cooling process is required. Therefore, in the present invention, such a rolling material that requires cooling for a long time is transferred from the transfer line to the retreat line 8 and is subjected to a cooling process in the retreat line 8.
FIG. 2 shows details of the evacuation line 8.
During normal rolling, the rolling material 6 is conveyed toward the finishing mill 4 by the conveying line 5, that is, in the direction of the arrow 10.
The evacuation line 8 is for evacuating the rolling raw material 6 from the conveyance line 5 to the outside of the conveyance line 5. The evacuation line 8 shown in FIG. 2 extends over the length of the rolling material 6 in the conveying line 5 between the conveying rolls 5a and 5a in the direction perpendicular to the conveying direction 10 (direction of arrow 12). The drive roller group 11 for transferring 6 is arranged. The driving roller group 11 is supported by driving roller support means 13 that can be raised and lowered. When it is not necessary to cool the rolling material 6, the driving roller support means 13 is lowered so as not to hinder the conveyance of the rolling material 6 by the conveying line 5. On the other hand, the raw material for rolling 6 that needs to be cooled is raised with the driving roller support means 13 in a state where the raw material for rolling 6 is located at the intersection of the conveying line 5 and the retreat line 8, and the conveying roll 5a It is possible to lift the rolling material 6 supported by the drive roller group 11 and retreat it in the direction of the arrow 12.

  By adopting the above line configuration, the rolling material that requires controlled rolling can be sufficiently cooled off-line, and when the subsequent rolling material does not particularly require cooling. Since it can be conveyed to finish rolling as it is, the rolling process can be carried out efficiently regardless of the presence or absence of a long-time cooling process.

In the present invention, the direction in which the retreat line is provided with respect to the transport line is not particularly limited, but it is advantageous to provide the retraction drive roller group between the transport rolls in a direction perpendicular to the transport line. It is.
Further, the drive roller group for evacuation is normally kept below the transport roll level, and the drive roller group is raised at a necessary time to guide the rolling material to the evacuation position.

Note that the above-described evacuation line is not necessarily limited to one, and two or more evacuation lines may be provided for the transport line.
By adopting such a configuration, control rolling is required even when a rolling material that does not require a cooling process is fed after a plurality of rolling materials that require a cooling process are continued. As for the rolling material to be used, sufficient cooling can be performed, while the rolling material that does not require cooling treatment can be subjected to finish rolling without any problem.

  In the present invention, the raw material for rolling after rough rolling can be subjected to sufficient cooling treatment for those that require cooling treatment, while those that do not require cooling treatment can be subjected to finish rolling as they are, thus reducing the rolling efficiency. It is possible to roll steel bars without causing them to occur.

1 Continuous cast slab (bloom)
2 Heating furnace 3 Coarse rolling mill 4 Finish rolling mill 5 Conveying line 5a Conveying roll 6 Rolling material 7 Product bar 8 Retreat line 9 Cooling equipment
10 Transport direction
11 Drive roller group
12 Retraction direction
13 Driving roller support means

Claims (2)

After rolling the continuously cast bloom into a raw material for rolling steel bar, when producing the steel bar by subjecting the rolling material to finish rolling,
In the conveyance line that conveys the rolling material that has exited the rough rolling mill to the finishing rolling mill, a retreat line that retracts the rolling material from the conveyance line is provided,
For the rolling material that needs to be cooled before finish rolling, the rolling material is once transferred from the transfer line to the evacuation line, and necessary cooling is performed in the evacuation line, and the rolling material is cooled to a desired temperature. After that, it is returned to the transport line and transported to the finish rolling mill, while the rolling material that does not require cooling before finish rolling is passed through the transport line as it is and guided to the finish mill. Steel bar rolling method.   The steel bar rolling method according to claim 1, wherein a plurality of the retreat lines are provided for each of the transport lines.

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