Roll profile of three-roll skew rolling tube mill

Abstract

The present invention relates to a roll profile of a three-roll skew rolling tube mill (referred to as an Assel tube mill), belonging to the field of hot-rolling steel pipe rolling process in the iron and steel metallurgy industry. The present invention is used to solve the pain point problem of serious spiral channel defects on the inner and outer surfaces of the steel pipe after Assel rolling: the shape of the roll is a truncated cone, the value range of the roll diameter D is 280-1100 mm, and the value range of the roll body length L is 300-800 mm. The conical surface of the roll consists of four major parts: an inlet cone, a roll shoulder, an sizing section, and an outlet cone. The roll profile provided by the present invention can significantly reduce the additional deformation during Assel rolling, reduce the non-uniformity of deformation, and can control the depth of the spiral channels on the inner and outer surfaces of the steel pipe after Assel rolling within 0.3 mm, thereby achieving high-quality production.

Description

Technical Field

[0001] The present invention belongs to the field of hot-rolled steel pipe rolling processes in the iron and steel metallurgy industry, and relates to a roll profile of a three-roll skew rolling mill. Background Art

[0002] The three-roll skew rolling mill, abbreviated as the Assel rolling mill, belongs to a high-precision skew rolling mill and has great advantages in the production of medium and thick-walled steel pipes: large single-machine deformation, high wall thickness accuracy, flexible adjustment, simple specification change, few rolling tools, etc. It is one of the important models indispensable in the current production of hot-rolled seamless steel pipes. However, when this rolling mill actually produces steel pipes (especially thin-wall specifications), quality problems such as uneven spiral wall thickness of the pierced billet after rolling and serious internal thread depth are likely to occur, seriously affecting its use effect. Therefore, the research on controlling the generation of internal threads or reducing the internal thread depth undoubtedly has important theoretical and practical significance for improving the quality of seamless pipes and reducing the accident rate during use. Theoretical research and production practice have shown that the roll profile design of the Assel rolling mill directly affects the degree of internal thread defects in the pierced billet after rolling. Summary of the Invention

[0003] In view of this, aiming at the pain point problem of serious internal and external spiral groove quality defects of steel pipes that are likely to occur during the production process of the Assel rolling mill, the purpose of the present invention is to provide a roll profile of a three-roll skew rolling mill. Through a series of optimization designs of the shape and size of the roll profile, it is possible to control the depth of internal and external spiral threads of the pierced billet after rolling to ≤0.3 mm.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A roll profile of a three-roll skew rolling mill includes a roll. The outer shape of the roll is in the shape of a truncated cone. The roll diameter D ranges from 280 to 1100 mm, and the roll body length L ranges from 300 to 800 mm. The conical surface of the roll sequentially includes four parts: an inlet cone, a roll shoulder, an sizing section, and an outlet cone.

[0006] Optionally, the inlet cone is composed of a rounded corner and a straight line segment at an angle φ with the horizontal line, and the angle φ is 1 to 3°.

[0007] Optionally, the roll shoulder is formed by two directly tangent large and small arcs to form a step with a height of h, and h < 10 mm.

[0008] Optionally, the quantitative relationship between the radii of the two large and small arcs of the roll shoulder and the step height h is R1 = h, and R2 = 1.71h.

[0009] Optionally, the sizing section is a large arc.

[0010] Optionally, the arc radius R3 of the sizing section is 1500 to 2500 mm.

[0011] Optionally, the length of the equalizing circular arc section is not less than 1.5 times the pitch of the incoming rolled piece.

[0012] Optionally, the exit cone consists of a small circular arc, a straight line segment making an angle α with the horizontal line, and a fillet, where the angle α is 2 - 4°.

[0013] Optionally, the small circular arcs of the exit cone are tangent to the equalizing section and the straight line segment of the exit cone respectively, forming a smooth transition.

[0014] Optionally, the radius R4 of the small circular arc of the exit cone is 300 - 400 mm.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention focuses on optimizing the design of several key factors affecting the spiral thread defects of the rolled rough tube in the roll profile design, namely the roll shoulder, the equalizing section (rolling belt), and the exit cone, so as to achieve a smooth transition of the metal in the roll profile during the rolling process, reduce the additional torsional deformation, and ensure the uniformity of deformation as much as possible, thereby realizing the control of the internal and external spiral thread depths of the rolled rough tube and improving the surface quality of the steel pipe.

[0017] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent description, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail with reference to the accompanying drawings, where:

[0019] Figure 1 is a schematic diagram of the roll profile solution of the present invention;

[0020] Figure 2 is the pass structure of a three-roll skew rolling mill;

[0021] Figure 3 is the frame structure of a three-roll skew rolling mill;

[0022] Figure 4 is the external spiral thread defect characteristics of the rolled rough tube after rolling by a three-roll skew rolling mill;

[0023] Figure 5 is the internal spiral thread defect characteristics of the rolled rough tube after rolling by a three-roll skew rolling mill.

[0024] Reference numerals: entrance cone 1, roll shoulder 2, equalizing section 3, transition section 4, exit cone 5. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0026] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than actual diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0027] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0028] Please refer to Figures 1 to 5 , Figure 4 and Figure 5 which show the internal and external spiral thread features that are likely to appear after the steel pipe is rolled by the Assel pipe mill. The spiral threads reflect a wall thickness non-uniformity on the inner and outer surfaces of the steel pipe in the spiral direction. Its essence is caused by various non-uniform deformations during the rolling process, including additional shear deformation and torsional deformation during the rolling process, non-uniform deformation caused by the connection and transition in different rolling stages, non-uniform wall thickness equalization deformation during the rolling process, etc. The quality of the roll profile design directly affects the degree of this non-uniform deformation. Figure 2 and Figure 3 which show the Assel pipe mill stand and pass structure. The Assel pipe mill is a single-stand skew rolling mill, and its stand consists of 3 rolls that are 120° apart from each other, and the rolls are conical. During operation, the 3 rolls and the long mandrel jointly complete the processes of biting the incoming billet, reducing the diameter, concentrating the wall thickness reduction, equalizing the wall thickness, and sizing and discharging the steel, achieving a large reduction in deformation. Figure 1The roll profile solution of the present invention is shown as follows. The shape of the roll is a frustum of a cone. The value range of the roll diameter D is 280 - 1100 mm, and the value range of the roll body length L is 300 - 800 mm. The roll profile consists of four major parts: the entrance cone 1, the roll shoulder 2, the sizing section 3, and the exit cone 5, which respectively correspond to the diameter reduction area, the wall thickness reduction area, the rolling area, and the roundness area from the perspective of deformation. Among them, the roll entrance cone 1 consists of a section of rounded corner + a straight line section with an angle φ to the horizontal line, and the angle φ is 1 - 3°; the roll shoulder 2 consists of two directly tangent large and small arcs, forming a step with a height of h, h < 10 mm, and the quantitative relationship between the radii of the two large and small arcs and the step height h is R1 = h, R2 = 1.71h; the sizing section 3 is a large arc, the arc radius R3 is 1500 - 2500 mm, and the length of the arc section is not less than 1.5 times the pitch of the incoming rolled piece; the exit cone 4 consists of a small arc + a straight line section with an angle α to the horizontal line + a section of rounded corner, the angle α is 2 - 4°, the small arc is tangent to the sizing section 3 and the straight line section of the exit cone 5 respectively to form a smooth transition, and the radius of the small arc R4 is 300 - 400 mm. A transition section 4 is provided between the exit cone 5 and the sizing section 3. Theoretical research shows that the above Figure 4 shown roll profile solution can significantly reduce the additional deformation in the Assel rolling process and reduce the non-uniformity of deformation, thereby effectively reducing the depths of the internal and external surface spiral grooves of the steel pipe after Assel rolling.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A roll profile of a three-roll skew tube rolling mill, characterized in that: It includes a roll. The outer shape of the roll is in the shape of a frustum of a cone. The diameter D of the roll ranges from 280 to 1100 mm, and the body length L of the roll ranges from 300 to 800 mm. The conical surface of the roll successively includes four major parts: an inlet cone, a roll shoulder, an equalizing section, and an outlet cone. The inlet cone consists of a rounded corner and a straight line segment that forms an angle φ with the horizontal line, and the angle φ ranges from 1 to 3°. The roll shoulder is formed by two directly tangent large and small arcs to form a step with a height of h, where h < 10 mm. The equalizing section is a large arc. The arc radius R3 of the equalizing section ranges from 1500 to 2500 mm. The arc length of the equalizing section is not less than 1.5 times the pitch of the inlet rolled piece. The outlet cone consists of a small arc, a straight line segment that forms an angle α with the horizontal line, and a rounded corner, and the angle α ranges from 2 to 4°. The radius R4 of the small arc of the outlet cone ranges from 300 to 400 mm.

2. The roll profile of the three-roll skew tube rolling mill according to claim 1, characterized in that: The quantitative relationship between the radii of the two large and small arcs of the roll shoulder and the step height h is R1 = h and R2 = 1.71h.

3. The roll profile of the three-roll skew tube rolling mill according to claim 1, characterized in that: The small arcs of the outlet cone are respectively tangent to the equalizing section and the straight line segment of the outlet cone to form a smooth transition.

Images