JP7726188B2 - Rolling method - Google Patents

Description

The present invention relates to technology for suppressing rotation (also known as tilt) of the steel material being rolled (rolled material) when producing steel materials such as steel bars and wire rods through continuous rolling.

Patent Document 1 discloses a technique for suppressing wear of guide rollers in an entry guide member. Specifically, it discloses a rolled steel material guide device having first and second row guide rollers connected to the exit side of the entry guide member. The first row guide rollers have a roll barrel made of metal. The second row guide rollers have a roll barrel made of silicon nitride ceramic.
It also describes that when the exit width of the entry guide member is We, the first row guide roller spacing is Wr1, and the roller spacing of the second row guide rollers is Wr2, the device is designed to satisfy the following formula: In other words, the document discloses a rolled steel material guide device in which the following relationship is set with respect to the width dimension Ws of the steel material to be rolled.

We>Wr1>Ws≧Wr2
However, the method of Patent Document 1 has a problem in that the gap between the rollers of the guide is small compared to the dimensions of the steel material, and therefore the load on the guide is large.
Furthermore, Patent Document 2 describes a technique for suppressing the rotation of steel material. Specifically, it discloses that the ratio K/M of the spring constant K of the roller guide portion of the roller guide device to the gradient M of the plastic curve when the steel material is pressed down by the guide rollers is set to 0.5 or more.
However, the method of Patent Document 2 may require extensive modification of the equipment.

Japanese Utility Model Application Publication No. 62-179105 Japanese Unexamined Patent Publication No. 6-190425

As a result of various investigations, the present inventors have reached the following findings. That is, when the relationship between the cross-sectional shape of the steel material to be rolled and the shape of the guide roller caliber does not match, the steel material rotates. Conventional guide roller calibers have caliber shapes that are close to perfect circles, which creates an environment in which the steel material rotates. When the steel material rotates, the steel material gets stuck in the rolling mill or guide device, causing misrolling. Or, there is a risk of product defects (crease defects) occurring due to the steel material getting caught in the roll caliber.
The present invention has been made in consideration of the above points, and aims to provide a rolling method and a method for manufacturing a steel material that do not require large-scale equipment modifications, do not place a large load on the guides, and when continuously rolling steel material made of straight bars or wire rods, can suppress rotation of the steel material between rolling mills, thereby making it possible to continuously roll the steel material without the occurrence of misrolling or product defects (folding defects).

Based on the above findings, the present invention introduces a new concept of steel material retention derived from the guide roller groove shape and steel material dimensions in order to solve the problem, and sets the range of this steel material retention as a rolling condition.
In order to solve the problems, one aspect of the present invention is a rolling method for producing a steel material consisting of a straight bar or a wire rod by continuous rolling using a plurality of rolling mills lined up along a pass line, wherein a pair of guide rollers is provided to guide the steel material on the entry side of at least one of the plurality of rolling mills, and when the area reduction rate in a front-stage rolling mill that is the rolling mill immediately preceding the guide rollers is 12% or more, the rolling conditions are set for the guide rollers so that the steel material retention ability α, defined by the following formula, is in the range of 0.75 to 1.2.

α = (w/H)×cosθ
where:
H: height dimension of the steel material, w: contact width between the steel material and the guide roller, θ: angle formed by a perpendicular to the curved surface of the guide roller and the opposing direction of the pair of guide rollers at the contact end between the steel material and the guide roller.

According to this aspect of the present invention, it is possible to provide a rolling method and a steel manufacturing method that do not require major equipment modifications, do not place a large load on the guides, and when continuously rolling steel material consisting of straight bars or wire rods, suppresses the steel material from rotating between rolling mills, thereby enabling continuous rolling of steel material without the occurrence of misrolls or product defects (folding defects).

FIG. 2 is a diagram illustrating an example of an arrangement of rolling mills. FIG. 2 is a diagram showing an example of a guide device arranged on the entry side of a rolling mill. 1A and 1B are diagrams illustrating a guide device, in which FIG. 1A is a top view and FIG. 1B is a side view. FIG. 10 is a diagram for explaining the derivation of steel material retention ability α. FIG. 10 is a diagram illustrating the relationship between steel material retention ability α and area reduction rate.

Next, this embodiment will be described with reference to the drawings.
1, the rolling facility of this embodiment is configured such that a plurality of rolling mills 1 are arranged along a pass line, and the plurality of rows of rolling mills 1 continuously roll a steel material 3 to produce a steel material 3 made of a straight bar. The present disclosure can also be applied to the production of a steel material made of a wire rod.
In FIG. 1, steel material 3 extracted from a heating furnace 2 is rolled in the order of a compact rolling mill 1A, a roughing rolling mill 1B, an intermediate rolling mill 1C, a finishing rolling mill 1D, and a four-roll bar rolling mill 1E to produce the target steel material.

In this embodiment, in a row of compact rolling mills 1A, roughing rolling mills 1B, intermediate rolling mills 1C, and finishing rolling mills 1D, rolling mills equipped with horizontal rolls and rolling mills equipped with vertical rolls are arranged alternately, as shown in the schematic diagram of Figure 2. In addition, a guide device 4 is provided on the entry side of the rolling mill to guide and hold the steel material 3 into the grooves of the rolls. A rolling mill having a guide device 4 on the entry side is also referred to as a target rolling mill 1X. In addition, a rolling mill in the stage preceding the guide device 4 is also referred to as a front-stage rolling mill 1Y.
The guide device 4 includes, for example, two rows of guide rollers 5 as shown in Fig. 3, and is capable of holding the steel material 3 between the rollers. In Fig. 3, reference numeral 4a denotes a roller holder. Each guide roller 5 is formed of a pair of guide rollers 5, and the opposing direction of the pair of guide rollers 5 is set to the same direction as the opposing direction of the rolling rollers of the front-stage rolling mill 1Y.

In this embodiment, in a guide device 4 in which the area reduction rate in the front-stage rolling mill 1Y is set to 12% or more, the rolling conditions of at least one guide roller 5 in the row of guide rollers 5 that the guide device 4 has are set so that the steel retention α defined by the following formula is in the range of 0.75 or more and 1.2 or less.
The steel material retention ability α was defined by the following formula.
α = (w/H)×cosθ
Here, as shown in FIG.
H: height dimension of steel material 3 w: contact width between steel material 3 and guide roller 5 θ: angle formed by a perpendicular line to the curved surface of the roller groove shape and a vertical line (in the opposing direction of the pair of guide rollers) at the contact end between steel material 3 and guide roller 5.

Next, the derivation of the steel material retention ability α will be explained.
The pair of guide rollers 5, each having a groove 5a facing each other, are arranged as shown in FIG.
At this time, when the steel material 3 tries to rotate, a thrust force is generated in the steel material 3, and a force F1 that rotates the steel material 3 and a moment m1 that tries to rotate the steel material 3 are generated, as shown in Figure 4.
In addition, in response to the rotational moment m1, a force F2 by which the guide roller holds the steel material 3 and a moment m2 by which the guide roller holds the steel material 3 are generated at the contact end between the steel material 3 and the guide roller 5.

In addition, in FIG.
H: Height dimension of steel material 3 (roll groove depth x 2 + roll gap)
w: contact width between the steel material 3 and the guide roller 5 (measured by measuring the contact mark on the guide roller 5)
θ: the angle formed by the perpendicular line to the roller curved surface and the vertical line (the opposing direction of the pair of guide rollers) at the contact end between the steel material 3 and the guide roller 5.
These values can be derived from the design drawing of the guide roller 5 and the actual measured value of the contact width.
Since moments m1 and m2 are mechanical moments, the following relationship holds:

m1=(H/2)×F1...(1)
m2=(w/2)×F2×cosθ...(2)
When the steel material 3 can be held by the guide rollers 5, m1 < m2 holds. Therefore, formulas (1) and (2) can be rearranged to obtain formula (3) below.
F1 <(w/H)×cosθ×F2...(3)
In this embodiment, the coefficient multiplied by F2 in equation (3) is α, which is used as an evaluation index for the steel material retention ability of the guide rollers 5.
That is, the steel material retention ability α was set to (w/H)×cos θ.

When experiments were carried out under the above conditions, it was confirmed that, as shown in Table 1, rotation of the steel material 3 was suppressed when 0.75 or more≦α≦1.2, preferably 0.75≦α≦0.95.
To bring the steel material retention ability α into the above range, for example, the groove shape of the guide roller 5 can be changed from a conventional shape close to a perfect circle to an elliptical shape that reduces the undulations in the steel material height direction and widens in the steel material width direction.
The present invention is effective as long as the distance between the front-stage rolling mill 1Y and the guide rollers 5 is, for example, within 12 m. Preferably, the distance between the front-stage rolling mill 1Y and the guide rollers 5 is within 6 m.

(Operations etc.)
The area reduction rate of the steel material 3 in the front-stage rolling mill 1Y of the target guide roller 5 is ensured to be 12% or more. This suppresses the rotation of the steel material 3 in the rolls of the front-stage rolling mill 1Y. The upper limit of the area reduction rate is 35%.
In addition, by reducing the height dimension of the steel material 3 relative to the guide rollers 5 in the front-stage rolling mill 1Y, the moment that causes the steel material 3 to rotate can be reduced, and the rotation of the steel material 3 can be suppressed.
Under the above conditions, by setting the steel material retention ability α within the range of 0.75≦α≦0.95, it becomes possible to more reliably prevent the steel material from rotating three times on the guide rollers 5 .

Here, setting the steel material retention ability α within the range of 0.75≦α≦0.95 means that the groove shape of the guide roller 5 is changed from a perfect circular shape to an elliptical shape that is wider in the steel material width direction and has less undulation in the steel material height direction than in the conventional case. This increases the contact width between the steel material 3 and the guide roller 5, improves the moment with which the guide roller 5 retains the steel material 3, and can suppress rotation of the steel material 3.
Furthermore, it is preferable to set the steel material retention ability α within the above range to ensure that the rotation of the steel material 3 on the guide rollers 5 is suppressed, and then set the steel material aspect ratio (steel material width dimension W/steel material height dimension H) after the first-stage rolling to 1.5 or less. In this case, more stable continuous rolling is possible. Here, by setting the steel material retention ability α to 0.75 or more and 1.2 or less, the rotation of the steel material 3 on the guide rollers 5 can be suppressed, but based on past experience, the steel material retention ability α is preferably 0.95 or less. Furthermore, if the steel material aspect ratio is greater than 1.5, the cross section of the steel material 3 will be excessively rolled in the height direction. As a result, the dimension in the steel material width direction will increase, becoming larger than the roll gap of the rear-stage rolling mill, which may cause problems such as the steel material 3 not being able to enter or being clogged in the target rolling mill 1X in the rear stage.

In order to ensure the contact width between the steel material 3 and the guide rollers 5, it is desirable that the curvature of the roll groove of the front-stage rolling mill 1Y and the curvature of the guide rollers 5 be the same.
Here, it is desirable that the gap between the guide rollers 5 and the steel material 3 is set to -0.3 to 0.0 mm on one side (setting to contact the steel material 3 or further narrower). When the steel material 3 enters between the pair of rollers of the guide rollers 5, the gap between the pair of rollers corresponds to the height dimension of the steel material 3 against the springs that bias the pair of rollers.
Here, the guide device 4 may be, for example, a leaf spring-like device having a mechanism and material with a flexible allowance. The spring coefficient for biasing the opposing rollers of the guide rollers 5 is preferably equal to or greater than 22 N/mm. There are no particular limitations on this spring coefficient.

(others)
The present disclosure may also have the following configuration.
(1) A rolling method for producing a steel material consisting of a straight bar or a wire rod by continuous rolling using a plurality of rolling mills arranged along a pass line,
a pair of guide rollers for guiding the steel material to an inlet side of at least one of the plurality of rolling mills;
When the area reduction rate of the front-stage rolling mill, which is the rolling mill immediately preceding the guide roller, is 12% or more, the rolling conditions for the guide roller are set so that the steel material retention α defined by the following formula is in the range of 0.75 to 1.2:
A rolling method characterized by:

α = (w/H)×cosθ
where:
H: height dimension of the steel material, w: contact width between the steel material and the guide roller, θ: angle formed by a perpendicular to the curved surface of the guide roller and the opposing direction of the pair of guide rollers at the contact end between the steel material and the guide roller.
(2) The aspect ratio (steel width/steel height) of the steel material after rolling in the front-stage rolling mill is set to 1.5 or less.
(3) The opposing direction of the rolling rollers of the first-stage rolling mill and the opposing direction of the pair of guide rollers are set to the same direction, and the curvature of the groove shape of the rolling rollers of the first-stage rolling mill and the curvature of the groove shape of the guide rollers are set to the same value.
(4) A method for producing a steel material consisting of a straight rod or wire rod, characterized by rolling using the rolling method disclosed herein.

Example 1
An experiment was actually carried out under the rolling conditions shown in Table 1 below, and the relationship between the steel material retention ability α and the rotation of the steel material 3 was evaluated.
Here, the evaluation of the rotation of the steel material 3 was judged based on the presence or absence of misalignment of the rolling marks relative to the grooves of the pair of guide rollers. The misalignment was checked visually on the entry side of the target rolling stand to see if there was any contact mark. For example, a piece of wood was placed against the steel material 3 on the exit side of the guide to check for any contact marks.
When there was a trace of contact, it was evaluated that rotation had occurred in the steel material 3, and when there was no trace of contact that could be visually confirmed, it was evaluated that there was no rotation in the steel material 3.

Based on the actual transport speed of the product diameter, the transport speed of the target rolling stand was set in the range of 0.5 m/s to 3.9 m/s. Note that the smaller the product diameter, the faster the transport speed. However, it is believed that the transport speed of the target rolling stand does not have much effect on the rotation of the steel material 3.
As can be seen from Table 1, it was found that the rotation of the steel material 3 can be effectively suppressed by setting the steel material retention ability α in the range of 0.75 to 0.95.
Example 2
In addition, the relationship between the area reduction rate in the front-stage rolling mill 1Y and the steel material retention ability α in the guide rollers 5 of the guide device 4 arranged on the inlet side of the target rolling mill was determined, and the results shown in Figure 5 were obtained.
As can be seen from FIG. 5, when the area reduction rate in the upstream rolling mill is 12% or more, it has been found that by setting the steel material retention ability α to 0.75 or more, rotation of the steel material 3 can be prevented more stably.
Furthermore, the inventors have confirmed that by applying the rolling conditions of the present invention to product diameters (47 mm to 60 mm) where rotation of steel material frequently occurred in the past, the steel material retention force in the rolling mill and guide rollers was improved, and the rolling stoppage time due to steel material rotation problems was reduced by 15%.

1 Rolling mill 1X Target rolling mill 1Y Front stage rolling mill 3 Steel material 4 Guide device 5 Guide roller 5a Groove α Steel material retention

Claims (5)

A rolling method for producing a steel material consisting of a straight bar or a wire rod by continuous rolling using a plurality of rolling mills arranged along a pass line, comprising:
a pair of guide rollers for guiding the steel material to an inlet side of at least one of the plurality of rolling mills;
When the area reduction rate of the front-stage rolling mill, which is the rolling mill immediately preceding the guide roller, is 12% or more, the rolling conditions for the guide roller are set so that the steel material retention α defined by the following formula is in the range of 0.75 to 1.2:
A rolling method characterized by:

α = (w/H)×cosθ
where:
H: height dimension of the steel material, w: contact width between the steel material and the guide roller, θ: angle formed by a perpendicular to the curved surface of the guide roller and the opposing direction of the pair of guide rollers at the contact end between the steel material and the guide roller. The rolling method described in claim 1, characterized in that the aspect ratio (steel width dimension/steel height dimension) of the steel material after rolling in the front-stage rolling mill is set to 1.5 or less. the opposing direction of the rolling rollers of the first-stage rolling mill and the opposing direction of the pair of guide rollers are set to the same direction, and the curvature of the groove of the rolling roller of the first-stage rolling mill and the curvature of the groove of the guide roller are set to the same value.
3. The rolling method according to claim 1 or 2. A method for producing steel material consisting of straight rods or wire rods, characterized by rolling using the rolling method described in claim 1 or 2. A method for producing a steel material made of a straight rod or wire rod, characterized in that the steel material is rolled using the rolling method according to claim 3.