JP2000233202A - Four-roll rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To roll a bar material whose cross section is approximately circular and which is passed through a rolling mill in a preceding stage into an approximately square cross section by one pass. SOLUTION: This method is the one by which a steel bar 1 is rolled into the approximately circular cross section with the rolling mill C in the preceding stage and the steel bar 1 after its tail end is passed through the rolling mill C is rolled into the approximately square cross section using a four-roll rolling mill 3. By forcedly pressing the steel bar 1 having the approximately circular cross section into the four-roll rolling mill 3 using a pinch roll 4, this steel bar 1 is rolled into the approximately square cross section at the reduction rate of area of >=5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling mill having a substantially circular cross section by a rolling mill in the preceding process, and after passing through the rolling mill, the bar is rolled into a substantially square cross section using a four-roll rolling mill. About the method.

[0002]

2. Description of the Related Art In hot rolling of steel bars, rolling is performed by a four-roll rolling mill. In this case, it is common to roll from square steel to round steel.

[0003]

However, when a steel bar rolled into a substantially circular cross section by a rolling mill in the preceding process is passed through the rolling mill and then rolled into a substantially square cross section using a four-roll rolling mill. In order to reduce the cross-sectional shape of the steel bar from round to square in one pass, the area reduction rate (= (cross-sectional area of material before rolling A ₀ -cross-sectional area of material after rolling A) / cut of material before rolling It is necessary to increase the area A ₀ ). As a result, there is a disadvantage that the bite of the bar with respect to the four-roll rolling mill is deteriorated, and it becomes difficult to roll the bar from a round shape to a square shape in one pass. .

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and is a four roll capable of rolling a bar having a substantially circular cross section having passed through a rolling mill in a previous step into a substantially square cross section in one pass. An object is to provide a rolling method.

[0005]

In order to achieve the above object, a four-roll rolling method according to the present invention is to roll a bar into a substantially circular cross section by a rolling mill in a preceding step, and to set the tail end of the rolling mill in the rolling mill. Is a method of rolling the bar having a substantially rectangular cross section using a four-roll rolling mill after passing through, and forcing the bar having a substantially circular cross section into the four-roll rolling mill using a pushing means. The bar is rolled into a substantially square cross section with a reduction of 5% or more in area.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory schematic diagram for explaining a four-roll rolling method as an example of an embodiment of the present invention, FIG. 2 is a diagram showing a cross-sectional shape of a steel bar before and after rolling by a four-roll rolling mill, and FIG. FIG. 4 is a graph showing the relationship between the area reduction rate, biting property, and the ratio of the flat part of the four-roll rolling mill in the method according to the present invention. FIG. 5 is a graph showing the relationship with the ratio, FIG. 5 is a diagram showing a modification of the cross-sectional shape of the steel bar before and after rolling by a four-roll rolling mill, and FIGS. 6 and 7 are diagrams showing another embodiment of the present invention. .

In FIG. 1, reference numeral A denotes a heating furnace, B denotes a row of rough rolling mills, C denotes a row of intermediate rolling mills, and both the row of rough rolling mills B and the row of intermediate rolling mills C are traveling directions (rolling directions) of the bar 1. And a plurality of two-roll rolling mills 2 arranged in such a manner that the rolling directions are alternately perpendicular to each other. A sizing rolling pass D is disposed downstream of the intermediate rolling mill row C, and the sizing rolling pass D is disposed on a single 4-roll rolling mill 3 and on the upstream side of the 4-roll rolling mill 3. Pinch roll (pressing means) 4.

[0008] Then, the steel bar 1 discharged from the heating furnace A is rolled into a substantially circular cross section by the rough rolling mill row B and the intermediate rolling mill row C, and then the bar steel after the tail end has passed through the intermediate rolling mill row C. 1 is forcibly pushed into the four-roll rolling mill 3 by the pinch roll 4, whereby the bite 1 is rolled by the four-roll rolling mill 3 into a substantially rectangular cross section in one pass by the four-roll rolling mill 3.

In this embodiment, the area reduction rate of the four-roll rolling mill 3 is set to 5% or more and 30% or less. When the area reduction rate is less than 5%, the cross-sectional shape of the steel bar 1 rolled by the four-roll rolling mill 3 is hardly rounded and almost square,
On the other hand, if it exceeds 30%, it becomes difficult to roll the steel bar 1 into a square cross section in one pass. As described above, in this embodiment, the bar steel 1 rolled into a substantially circular cross section by the rough rolling mill row B and the intermediate rolling mill row C is pinch rolled after the tail end of the steel bar 1 passes through the intermediate rolling mill row C. 4 in 4 roll mill 3
, So that the biting property of the four-roll rolling mill 3 can be ensured even with a surface reduction rate of 5% or more. Can be rolled into a substantially square cross section in one pass using a four-roll rolling mill 3 (see FIG. 2).

In addition, since the steel bar 1 having a substantially circular cross section can be rolled into a substantially square cross section at a reduction ratio of 5% or more,
The ratio (b / a) of the flat portion of the bar 1 rolled by the four-roll rolling mill 3 can be freely adjusted, and the ratio b / a of the flat portion can be reduced.
Since the R of the corners in the cross-sectional shape of (1) can be increased to make the bar 1 roll easily, the transportability of the bar 1 can be improved.

FIG. 3 shows the relationship among the area reduction ratio, the biting property, and the ratio of the flat portion in the conventional four-roll rolling mill.
FIG. 4 shows the relationship among the area reduction ratio, biting property, and ratio of the flat portion of the four-roll rolling mill in the method of the present invention. The same conditions are applied to both the method of the present invention and the conventional example except that a pinch roll is disposed downstream of the four-roll mill in the method of the present invention.

In the conventional method shown in FIG. 3, when the area reduction rate increases with the ratio (b / a) of the flat portion to 5% or more, the biting property of the four-roll rolling mill deteriorates. It can be seen that in the invention method, even if the area reduction rate increases with the ratio of the flat portion (b / a) to 5% or more, the biting property of the four-roll rolling mill is maintained in a good state. In the above-described embodiment, the case where the steel bar 1 having a substantially circular cross section is rolled into a substantially square cross section is taken as an example. However, as shown in FIG. The steel bar 1 having a substantially circular cross section may be rolled into a rectangular cross section by changing the rolling ratio of the steel bar.

In the above-described embodiment, a pinch roll is taken as an example of the pushing means. However, the present invention is not limited to this. For example, as shown in FIG. When the roll rolling mills 3a and 3b are provided, the bar steel 1 whose tail end has passed through the intermediate rolling mill row C in the upstream four roll rolling mill 3a is sent while being held under light pressure. You may make it forcefully push into the downstream 4 roll rolling mill 3b.

Further, in FIG. 6, four corners of the bar 1 rolled into a substantially square cross section by the four-roll rolling mill 3 are arranged with a phase shifted by 45 ° with respect to the four-roll rolling mill 3. This is an example in which the steel bar 1 is rolled by a four-roll rolling mill 5, whereby the steel bar 1 having a substantially octagonal cross section can be obtained.

[0015]

As is apparent from the above description, according to the present invention, it is possible to roll a rod having a substantially circular cross section that has passed through a rolling mill in the preceding process into a substantially square cross section in one pass. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory schematic diagram for explaining a four-roll rolling method which is an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional shape of a steel bar before and after rolling by a four-roll rolling mill.

FIG. 3 is a graph showing the relationship between the area reduction ratio, the biting property, and the ratio of a flat portion of a four-roll rolling mill in a conventional method.

FIG. 4 is a graph showing the relationship between the area reduction rate, biting property, and flat portion ratio of a four-roll rolling mill in the method of the present invention.

FIG. 5 is a diagram showing a modified example of the cross-sectional shape of a steel bar before and after rolling by a four-roll rolling mill.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 A: Heating furnace B: Rough rolling mill row C: Intermediate rolling mill row D: Sizing rolling pass 1: Steel bar (bar material) 3: 4-roll rolling mill 4: Pinch roll (pressing means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E002 AB06 AC12 AC14 BA04 BB01 BB05 BC01 BC05 BD08 CB06 CB08

Claims (1)

[Claims] 1. A bar material is rolled into a substantially circular cross section by a rolling mill in a previous process, and the bar material after its tail end has passed through the rolling mill is rolled into a substantially square cross section using a four-roll rolling mill. Wherein the bar having a substantially circular cross section is pressed by using a pressing means.
A four-roll rolling method, wherein the bar is forcibly pushed into a roll rolling mill to roll the bar into a substantially square cross section at a reduction in area of 5% or more.