JP2006289454A - Bloom rolling method for round billet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bloom rolling method for a round billet, which prevents the distortion or similar deformation of a material to be rolled and can perform bloom rolling in a stable state. <P>SOLUTION: In the invented bloom rolling method for the round billet, finish rolling of the material to be rolled is performed with round caliber rolls under the conditions meeting the following formula (1): α≥-0.000734×D+1.034 where α is a ratio of a contact width of the roll Bm(mm) to a width of material to be rolled at an inlet side of roll B(mm), and D is the diameter (mm) of the round billet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a round billet rolling method for producing round billets by continuous rolling using a continuous cast slab or an ingot, and in particular, rolling in a stable state while preventing torsion of the material to be rolled. The present invention relates to a method for rolling a billet of a round billet.

  In the batch rolling method, materials such as continuously cast slabs and ingots are sequentially rolled using a perforated roll having various perforations, thereby reducing the size of the cross section, and rounding of a predetermined dimension. It is a method of manufacturing a billet or a square billet.

  The round billet rolling method involves rolling a material with a rectangular cross-section (bloom, etc.) with a box hole roll, and then rolling with an intermediate hole (leader hole, octagon hole, oval hole, etc.) roll. In general, rolling with a round perforated roll is used as finish rolling. FIG. 1 shows an example of a typical rolling pass schedule in the round rolling of a round billet, and FIG. 2 shows examples of the hole shape of various hole rolls used for the round rolling of the round billet.

  Here, in particular, when finish rolling is performed with a round hole roll, the material to be rolled is likely to be twisted or tilted, and this causes a problem that the dimensional accuracy of the round billet after rolling deteriorates. In particular, when the twist or the like is significant, the material to be rolled is reversed (twisted), and the material to be rolled bites out of the roll gap of the round hole type roll, so that scrap treatment may be required.

  As a method of rolling in a stable state while preventing such a material to be rolled and twisted, for example, in Patent Document 1 and Non-Patent Document 1, an induction guide for guiding the material to be rolled into a hole shape is used. A method has been proposed. However, since it is difficult to bring such a guide into close contact with the perforated roll, there is a problem that a case where the material to be rolled is twisted after passing through the guide guide occurs. In addition, when the material to be rolled is twisted or the like, there is a problem that a large external force acts on the induction guide from the material to be rolled, resulting in a case where the induction guide is damaged.

On the other hand, in order to roll the material to be rolled in a stable state, it is conceivable to devise the hole shape of the hole roll itself. From such a viewpoint, Patent Document 2 proposes a diamond hole roll having a predetermined hole shape. However, the diamond perforated roll described in Patent Document 2 is a perforated roll for rolling a square billet and cannot be used for finish rolling of a round billet.
Japanese Patent No. 2628116 Japanese Utility Model Publication No. 62-174703 Edited by Japan Iron and Steel Institute, “Third Edition Steel Handbook III (1)”, Maruzen, 1980, p.155

  The present invention has been made to solve the above-described problems of the prior art, and provides a method for split rolling of a round billet that can prevent torsion of a material to be rolled and perform batch rolling in a stable state. The task is to do.

  In order to solve the above-mentioned problems, the inventors of the present invention first considered the reason why twisting or the like occurs when the material to be rolled is subjected to finish rolling with a round hole roll. FIG. 3 is an explanatory view for explaining moments generated in the cross section of the material to be rolled when rolling the material to be rolled. FIG. 3 (a) shows a case where the roll contact width is large, and FIG. 3 (b) shows a roll contact width. The case where is small is shown. 3A and 3B are a perspective view showing the upper half of the material to be rolled in order from the left, a side view and a front view showing a state in which the material to be rolled is rolled with a pair of upper and lower flat rolls. The figure (the figure seen from the rolling direction exit side) is shown. As shown in FIG. 3A, when a material to be rolled having a rectangular cross section is rolled with a flat roll, a rolling load P from the roll acts on the material to be rolled, and the rolling load P causes a cross section of the material to be rolled. Is considered to generate a moment M. As shown in FIG. 3 (b), the same applies to the case where a material to be rolled having a substantially circular cross section and only a part of the upper surface is flat rolled with a flat roll (FIG. 3 (b) shows a clockwise moment). Only M1 is shown). The inventors of the present invention normally have these moments M balanced on the left and right, that is, M1 (= P1 × L1) and M2 (= P2 × L2) are equal in FIG. However, when this balance is lost, it is considered that twisting or the like occurs in the material to be rolled.

  Here, since the moment M can be expressed by M = P × L (L is the distance from the center of the material to be rolled), the case where the roll contact width (the contact width between the material to be rolled and the roll on the roll entry side) is large. Is large (L1 in FIG. 3 (a)> L1 in FIG. 3 (b)), and the balanced moment itself is large (M1 in FIG. 3 (a)> M1 in FIG. 3 (b)). In addition, in FIG. 3 (a) and (b), in order to make description easy, although the case where it rolled with a flat roll was demonstrated, it is thought that it is the same also when rolling using a round hole type roll. And, the inventors of the present invention, if the roll contact width is increased and the moment generated when rolling is increased, the moment collapse due to temperature unevenness in the cross section of the material to be rolled and the movement in the thrust direction of the roll. It was considered that the material to be rolled was hardly affected by this, and it was difficult for the material to be rolled to twist.

Based on the above findings, the inventors of the present invention have conducted the ingot rolling test under various conditions. As a result, the inventors have identified the optimum parameters and completed the present invention. That is, the present invention provides a round billet partial rolling method characterized by rolling under a condition satisfying the following expression (1) when performing finish rolling on a material to be rolled using a round hole roll. Is.
α ≧ −0.000734 × D + 1.034 (1)
Here, in the above equation (1), α = roll contact width Bm (mm) / width B (mm) of the material to be rolled on the roll entry side, and D means the diameter (mm) of the round billet.

  As shown in FIG. 4, the roll contact width Bm means the distance between the first contact points of the material to be rolled and the round hole mold on the roll entry side, and the diameter D of the round billet is shown in FIG. The diameter of the round billet which tied the site | part corresponded to the groove bottom part of a round hole type roll as shown in FIG.

  According to the method of rolling a round billet according to the present invention, it is possible to prevent the to-be-rolled material from being twisted and to perform the batch rolling in a stable state, and thus it is possible to obtain a round billet with good dimensional accuracy. .

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 6 shows various blooms or ingots rolled using various types of intermediate hole type rolls such as a box hole type, octagon hole type, leader hole type, oval hole type, etc., and then finished and rolled using a round hole type roll. The diameter D (mm) and α (α = roll contact width Bm (mm) / roll entry width B (mm) of the roll entry side) and roundness of the round billet obtained when the billet was produced It is a figure which shows a relationship. FIG. 7 is a table showing various conditions corresponding to the data shown in FIG. As shown in FIG. 5, the roundness is roundness when the diameter of the round billet connecting the portions corresponding to the edge portions of the round hole roll is D1 (mm) and D2 (mm). = ABS (D1−D2) × 100 / Diameter D (Here, ABS (·) means an absolute value in ()). Moreover, the numerical value described in the column of “intermediate hole mold” in FIG. 7 means various conditions of the intermediate hole roll used in the rolling pass immediately before the finish rolling. Moreover, the numerical value described in the column of each symbol (B0, R0, etc.) in FIG. Furthermore, the unit of the numerical values shown in FIG. 7 is degrees (°) for the numerical values described in the θ column, dimensionless amounts for the numerical values described in the α column, and% for the numerical values described in the circularity column. All the numerical values described in the other columns are mm.

As shown in FIG. 6, there is a correlation between the diameter D of the round billet and α and the roundness, and if the condition is set so that α is equal to or larger than a predetermined value according to the diameter D of the round billet, It was found that twisting of the rolled material was reduced and good roundness (roundness ≦ 3%) was obtained. That is, the round billet partial rolling method according to the present embodiment is characterized by rolling under a condition satisfying the following expression (1) when performing finish rolling on a material to be rolled using a round hole roll. .
α ≧ −0.000734 × D + 1.034 (1)
Here, in the above equation (1), α = roll contact width Bm (mm) / width B (mm) of the material to be rolled on the roll entry side, and D means the diameter (mm) of the round billet.

  According to the round billet split rolling method according to the present embodiment, as shown in FIG. 6, it is possible to prevent the to-be-rolled material from being twisted and the like and to perform the split roll in a stable state, and hence the dimensional accuracy is good ( (Roundness ≦ 3%)) round billets can be obtained.

FIG. 1 shows a typical rolling pass schedule example in the round rolling of a round billet. FIG. 2 shows examples of the hole shape of various hole rolls used for ingot rolling of round billets. FIG. 3 is an explanatory view for explaining moments generated in the cross section of the material to be rolled when the material to be rolled is rolled. FIG. 4 is an explanatory diagram for explaining the meaning of phrases such as the roll contact width Bm. FIG. 5 is an explanatory diagram for explaining the meanings of the words of round billet diameter and roundness. FIG. 6 is a diagram showing the relationship between the diameter D, α, and roundness of a round billet. FIG. 7 is a table showing various conditions corresponding to the data shown in FIG.

Claims (1)

A round billet partial rolling method characterized by rolling under a condition satisfying the following expression (1) when a rolled material is subjected to finish rolling using a round hole roll.
α ≧ −0.000734 × D + 1.034 (1)
Here, in the above equation (1), α = roll contact width Bm (mm) / width B (mm) of the material to be rolled on the roll entry side, and D means the diameter (mm) of the round billet.

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