JP2002205116A - Two-roll straightening method with low residual strain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a straightening method of a seamless steel tube with low residual strain by controlling contact surfaces of the steel tube to be straightened and a roll to prevent generation of any local residual strain. SOLUTION: In a two-roll straightening method with low residual strain, rolls are used so as to ensure the three-point contact of the contact surfaces between a concave roll and a convex roll by setting the curvature of roll surfaces of the concave roll and the convex roll to be 1-7 deg., and allowing the curve shape of the concave roll to satisfy the conditions of b/c=0.25-0.35, and a/b=0.008-0.012 in the two-roll system with the concave roll and the convex roll arranged facing each other, where (a) is the margin at the center, (b) is the margin width at the center, and (c) is the length of the roll surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting low residual strain in two rolls of a seamless steel pipe.

[0002]

2. Description of the Related Art A straightening machine conventionally used for straightening a line contact type seamless steel pipe is shown in FIG. That is,
FIG. 5A is a perspective view, and FIG. 5B is a transverse sectional view. As shown in FIGS. 5 (a) and 5 (b), for example, in a two-roll line contact type straightening machine, the line contact type roll 1 has an uneven shape, a concave roll 2 on the upper surface and a convex roll 3 on the lower surface. The bending is performed by bending the seamless steel pipe 4 as a product in the longitudinal direction between the line contact type rolls 1 having the shape, and rotating the bending surface in accordance with the feed. . Also,
The guide shoe 5 is arranged vertically so that the product does not come off the roll during molding.

FIG. 6 is a diagram showing a straightening machine used for straightening a conventional air vent type seamless steel pipe. That is, FIG. 6A is a transverse sectional view, and FIG. 6B is a front sectional view. As shown in FIGS. 6A and 6B, for example, in an air vent type straightening machine,
The air vent type roll, which is composed of a concave roll 2 and a convex roll 3 and has the shape thereof, is formed by three points of the concave roll 2 and the convex roll 3 and the guide shoe 5 so as to be formed by two points of the concave roll and one point of the convex roll. The seamless steel pipe 4 as a product is bent in the longitudinal direction by the contact surface to perform low-speed bending correction.

[0004]

As described above, the conventional line contact type straightening machine is capable of high-speed straightening. However, when straightening the seamless steel pipe 4 with this line contact type straightening machine, the concave roll 2 is required. Since the contact surface between the roller and the convex roll 3 contacts the entire surface and is corrected, a large amount of high-level residual strain is generated in the seamless steel pipe 4 due to the reduction between the concave and convex rolls. In such a state, after the straightening, it is sent to the ring cutting or the inner and outer surface cutting process as secondary processing, and when the secondary processing is performed there is a high level of residual strain in the steel pipe. It returns to the state before correction,
There is a problem that the shape such as roundness and straightness deteriorates. On the other hand, the air vent type straightening machine of the three-point support type has a problem that it is low-speed straightening though the generation of residual strain is small.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive developments, and as a result, by controlling the contact surface between the steel pipe as the material to be corrected and the roll, a local area is obtained. An object of the present invention is to provide a method for straightening a seamless steel pipe having a low residual strain, which can prevent a residual strain from occurring and can perform a high-speed straightening. The gist of the invention is as follows: (1) In two rolls in which a concave roll and a convex roll are arranged to face each other, the curvature of the roll surface of the concave roll and the convex roll is 1 to 7
° and the roll curve shape of the concave roll is b / c
= 0.25-0.35, a / b = 0.008-0.01
A roll having a concave roll shape that satisfies the condition 2 is used, so that a contact surface between the concave roll and the convex roll is configured to ensure three-point contact. Straightening method. However, a: center part clearance, b: center part width, c: roll surface length (2) In the method described in the above (1), the concave roll angle 1
A low residual distortion correction method for two rolls, wherein the correction is performed on a three-point contact surface having a roll roll reduction of 0.10 to 3.00 mm with a convex roll angle of 8 to 24 ° and a convex roll angle of 15 to 18 °.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing a straightening machine used for straightening a seamless steel pipe according to the present invention. FIG. 1A is a front sectional view, and FIG. 1B is a transverse sectional view. As shown in this figure, a pair of cylindrical rolls having a curvature on the roll surface, drawing a smooth curve, and having respective concave and convex profiles. That is, the concave roll 2 and the convex roll 3
Are arranged opposite to each other, the curvature of the roll surface of the concave roll and the convex roll is set to 1 to 7 °, and the roll curve shape of the concave roll is b / c = 0.25 to 0.35, a / b =
A concave roll shape that satisfies the condition of 0.008 to 0.012 is formed.
The configuration is such that point contact can be ensured.

That is, the curvatures of the roll surfaces of the concave roll 2 and the convex roll 3 are changed in the range of 1 to 7 °, and the roll curve shape of the concave roll is b / c = 0.25 to 0.35, a /
By making the concave roll shape satisfying the condition of b = 0.008 to 0.012, the contact surface 6 between the concave roll 2 and the convex roll 3 is provided at two places in the concave roll 2 and one place in the convex roll 3. 3 point contact can be secured. By using such a roll having the curvature of the roll surface and the roll curve shape of the concave roll, good roundness and straightness can be obtained.

FIG. 2 is an explanatory diagram for determining a roll angle of the straightening machine according to the present invention. FIG. 2A is a top view of the straightening machine, and FIG. 2B is a cross-sectional view. As shown in this figure, the concave roll 2 and the convex roll 3 show angles of θ ₁ and θ ₂ with respect to the traveling direction of the steel pipe, respectively. The theta ₁ a concave roll angle, the theta ₂ a convex roll angle. Further, as can be seen from FIG. 2B, the concave roll and the convex roll are in a parallel state having no angle with the traveling direction of the steel pipe.

[0009]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples. Outer diameter: 15.0-114.
A hot-rolled material having a thickness of 0 mm and a thickness of 2.0 to 20.0 mm was subjected to heat treatment after cold rolling, and then the concave roll angle adjustment and the convex roll angle adjustment were performed, and then the roll reduction amount was adjusted, and the straightening was performed. As the roll angle at that time, a concave roll angle of 18 to
Correction was performed at a three-point contact surface with a roll roll reduction of 0.10 to 3.00 mm at 24 ° and a convex roll angle of 15 to 18 °. The residual strain was evaluated by a slit test. This slit test method refers to a method in which a test piece having a length of 60 mm is sampled from a location at a position of, for example, about 1000 mm from an end of a material to be corrected after correction, for example, about 1000 mm, and this sample piece is cut with a cutter width of 3 mm. In the sealing, the slit is divided in the axial direction, and due to the vertical division, the distortion inherent in the correction appears and the slit width is increased. The increase value of the slit width at this time is defined as residual strain. The results are shown as evaluation of residual strain.

FIG. 3 is a diagram showing the transition of the slit opening in the conventional method and the present invention. As shown in this figure, the slit opening (%) after the improvement according to the present invention is about 3%, compared to the line contact type of about 3.5% and the air vent type of 3.15 to 3.3%, which are the conventional methods. It can be seen that the slit opening degree in the conventional method was as small as 0.2%. FIG. 4 is a diagram showing the transition of the straightening speed according to the conventional method and the present invention. As shown in this figure, the speed is 3 to 22 m / min in the case of the conventional line contact type, and 3 to 18 m / min in the case of the conventional air vent type. In the case of the present invention, the straightening can be performed at a high speed of 40 to 75 m / min. This indicates that the residual strain was greatly improved despite the high speed correction.

[0011]

As described above, by controlling the contact surface between the material to be straightened and the straightening roll according to the present invention, the occurrence of local residual strain is prevented, and a steel pipe with low residual strain is manufactured. As a result, it was possible to prevent the deterioration of the shape after the secondary processing, and it was possible to manufacture a product having a very excellent shape at a high speed.

[Brief description of the drawings]

FIG. 1 is a view showing a straightening machine used for straightening a seamless steel pipe according to the present invention;

FIG. 2 is an explanatory view for determining a roll angle of the straightening machine according to the present invention,

FIG. 3 is a diagram showing a transition of a slit opening degree in a conventional method and the present invention,

FIG. 4 is a diagram showing the transition of the straightening speed according to the conventional method and the present invention,

FIG. 5 shows a straightening machine used for straightening a conventional line contact type seamless steel pipe;

FIG. 6 is a diagram showing a straightening machine used for straightening a conventional air vent type seamless steel pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Line contact type roll 2 Concave roll 3 Convex roll 4 Seamless steel pipe 5 Guide shoe 6 Contact surface

Continuing on the front page (72) Inventor Morizuki Kimura 3007 one-letter character in Nakashima, Shima-ku, Himeji-shi, Hyogo Sanyo Special Steel Co., Ltd. Inside the company

Claims (2)

[Claims] 1. A method in which a concave roll and a convex roll are arranged to face each other.
In the roll, the curvature of the roll surface of the concave roll and the convex roll is 1 to 7 °, and the roll curve shape of the concave roll is b / c = 0.25 to 0.35, a / b = 0.008 to
A roll having a concave roll shape that satisfies the condition of 0.012, wherein a roll configured to ensure three-point contact with the contact surfaces of the concave roll and the convex roll is used. Low residual distortion correction method. However,
a: center clearance, b: center clearance, c: roll surface length 2. The method according to claim 1, wherein the concave roll angle is 18 to 24 ° and the convex roll angle is 15 to 18 °, and the correction is performed at a three-point contact surface with a roll reduction amount of 0.10 to 3.00 mm. A characteristic method for correcting low residual distortion in two rolls.