Special large steel bar hole pattern speed difference straightening and bending method

Abstract

The invention provides a special large steel bar pass speed difference straightening and bending method which comprises the following steps: feeding a bent head of a to-be-corrected rolled piece into a speed difference straightening hole between an upper roller and a lower roller, in one side of the upper side or the lower side of the speed difference straightening hole, enabling the left side of the bent head of the rolled piece to be in contact with a point A on the inner wall of the speed difference straightening hole, and enabling the left side of the bent head of the rolled piece to be in contact with a point B on the inner wall of the speed difference straightening hole; the right side of the bent head is in contact with a point B on the inner wall of the speed difference straightening hole, and the vertical height of the point A is lower than that of the point B; on the same section, the metal deformation at the point A is faster than the metal deformation at the point B, and the metal at the point B generates tensile stress to the metal at the point A, so that the bending of the bent head of the to-be-corrected rolled piece is corrected under the action of the tensile stress. The quality requirement of high-end special round steel is met, and the breakthrough of low-cost and high-efficiency square steel rolling is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of special steel rolling, and in particular to a special steel large bar hole speed difference straightening and bending method. Background Art

[0002] Special steel includes three categories: high-quality carbon steel, alloy steel, and high-alloy steel. If the special steel rolling equipment is not designed properly or the process control is improper, it is easy to cause surface defects such as bending, cracks, wrinkles, folds, etc. of the rolled piece head. Optimizing the hole design and changing the roller speed difference can effectively avoid the bending of the rolled piece head formed after deformation.

[0003] The bending of the head of large bar rolling pieces is a problem that has always existed in the steel rolling process. When the large bar rolling mill has fewer stands (usually 3-4 stands), the mill's correction ability is insufficient, and even if the heating furnace meets the 30°C temperature difference range, the problem of bending of the head of the rolling piece is easy to occur. The method adopts the method of reducing the size of the inner hall of the guide guard at the exit of the final rolling unit, and forcibly straightening the bent steel through the guide guard, but this method is easy to cause scratches on the surface of the steel, defects and quality problems, and the guide guard loss is large, which increases the cost consumption of the guide guard per ton of steel. Summary of the invention

[0004] According to the above-mentioned prior art, the problem of scratching the steel surface caused by the bending of the rolled piece head is solved, and thus a method for straightening the bending of a special steel large bar by using the speed difference of the hole type is provided. The present invention straightens the bending of the rolled piece head caused by the bending of the steel by designing a reasonable hole type and automatically correcting the steel by using the technology of different metal deformation speed differences generated by contacting different metal positions of the hole type when the steel is rolled in the hole type.

[0005] The technical means adopted by the present invention are as follows:

[0006] A speed difference straightening and bending method for a hole type of a special steel large bar comprises the following steps: feeding a bent head of a rolled piece to be corrected into a speed difference straightening hole between an upper roller and a lower roller; on one side of the upper or lower side of the speed difference straightening hole, the left side of the bent head contacts point A of the inner wall of the speed difference straightening hole, and the right side of the bent head contacts point B of the inner wall of the speed difference straightening hole, wherein the vertical height of point A is lower than the vertical height of point B; in the same cross section, the metal deformation at point A is faster than the metal deformation at point B, and the metal at point B generates tensile stress on the metal at point A, so that the bending of the bent head of the rolled piece to be corrected is corrected under the action of the tensile stress.

[0007] Furthermore, the speed difference straightening hole is symmetrical up and down, and the speed difference straightening hole is symmetrical left and right. The speed difference straightening hole on one of the upper side or the lower side includes a top arc surface, and both sides of the top arc surface are respectively connected to the upper part of a side wall, and the lower part of the side wall is connected to the horizontal edge. The side wall is inclined from top to bottom toward the outer side of the top arc surface, and the angle between the side wall and the horizontal edge is an obtuse angle.

[0008] Furthermore, the angle between the side wall and the vertical line ranges from 15° to 22°.

[0009] Furthermore, the angle between the side wall and the horizontal edge is 112°.

[0010] Furthermore, the calculation formula of the slope of the side wall is as follows:

[0011] α=0.635η*(D / 2-B k ) / h

[0012] Among them, α is the side wall slope, η is the correction coefficient, D is the groove depth, B k is the hole width.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] The present invention uses a special hole type technology to eliminate the stress difference caused by the asymmetric rolling stress on both sides of the steel caused by the temperature difference under the reverse force generated by the speed difference of the rolled piece with bent head, thereby solving the bending defect of the rolled piece head of the large bar.

[0015] The present invention eliminates the bending defect of the head of the steel rolled piece, and reduces the risk of the rolling line equipment being damaged by the bending of the head of the rolled piece colliding with auxiliary equipment such as guides and rollers.

[0016] The invention solves the scratch defect caused by the steel material contacting the roller cover plate or the guide side wall due to the bending of the steel material.

[0017] The invention corrects and controls the bending of the head of a large bar rolled piece, ensures that the bar is rolled straight, reduces the straightening cost of a finishing process and the labor intensity of workers, and shortens the contract delivery cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 This is a diagram showing the situation of the rolled piece to be corrected in the speed difference straightening hole according to the present invention.

[0020] Figure 2 It is a schematic diagram of the speed difference straightening hole of the present invention.

[0021] Figure 3 This is a diagram showing the straightening of the bent head of the rolled piece in the pass according to the present invention.

[0022] In the figure: 1. top curved surface; 2. side wall; 3. horizontal edge. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0027] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0028] like Figure 1 As shown, the present invention provides a special steel large bar hole speed difference straightening and bending method, comprising the following steps: feeding the bent head of the rolled piece to be corrected into the speed difference straightening hole between the upper roller and the lower roller,

[0029] On one side of the upper or lower side of the speed difference straightening hole, the left side of the bent head contacts point A of the inner wall of the speed difference straightening hole, and the right side of the bent head contacts point B of the inner wall of the speed difference straightening hole, and the vertical height of point A is lower than the vertical height of point B; in the same cross-section, the metal deformation at point A is faster than the metal deformation at point B, and the metal at point B produces tensile stress on the metal at point A, so that the bending of the bent head of the rolled piece to be corrected is corrected under the action of tensile stress.

[0030] The speed difference straightening hole is symmetrical up and down, and symmetrical left and right. The speed difference straightening hole on one of the upper side or the lower side includes a top arc surface 1, and the two sides of the top arc surface are respectively connected to the upper part of a side wall 2, and the lower part of the side wall is connected to the horizontal edge 3. The side wall is inclined from top to bottom toward the outer side of the top arc surface, and the angle between the side wall and the horizontal edge is an obtuse angle.

[0031] 1. Reasons for the head bending caused by the temperature difference of the steel billet: 1. The large bar heating furnace is an end-in-end step-beam heating furnace. The steel billet is discharged from the heating furnace in the equalizing section. The furnace door is opened to discharge steel, and the heat loss is serious, with a temperature loss of 30℃-40℃. The production process repeatedly and continuously discharges steel, resulting in a low temperature on the side of the steel billet in the furnace facing the furnace door, and a large temperature difference in the billet (large yin and yang sides). 2. In the process of conveying the billet to the rolling mill on the roller table, the lower surface of the billet contacts the rollers (with cooling water), and the temperature of the lower surface drops by 10℃-20℃, resulting in a large temperature difference between the upper and lower surfaces of the steel billet (small yin and yang sides), causing the steel billet to extend differently up and down during rolling in the rolling mill, thus causing head bending deformation. 3. When a steel billet with a large temperature difference is rolled by the rolling mill, the metal deformation speed of the same cross section of the steel billet is different, and the metal flow speed on the high temperature side is higher than the metal flow speed on the low temperature side V1<V2 (see Figure 1 ), causing tensile stress and bending the raw head of the steel.

[0032] 2. Technical solution to the bending of rolled piece head: 1. Speed ​​difference analysis

[0033] The same cross section of the rolled piece contacts different positions of the pass, and there is a difference in the roller diameter at the contact point A and point B. For example, the roller diameter of the 850 rolling mill is 900mm. When the rolled piece is deformed in the elliptical pass, the roller diameter at point A is D. A =815.6mm, D B =775.6mm, calculated according to the linear speed formula:

[0034]

[0035] V A =0.299m / s, V B =0.271m / s, so the linear speed of metal deformation is inconsistent in different parts of the hole.

[0036] 2. Hole design with steel straightening head bending: Due to the symmetry of the elliptical hole design, the diameters on both sides of the center symmetry are generally the same, and the line speed is also the same V A >V B In the elliptical hole type, the smooth arc side wall is designed as a straight side wall to increase the linear velocity gradient, and the slope is designed to be 15°-22°, such as Figure 2 shown.

[0037] The temperature difference of the steel material causes the steel head to bend. At the moment when the steel head bites into the hole, the contact positions of the two sides are asymmetrical, one side is at point A, the other side is at point B, V A =0.299m / s>V B =0.271m / s. In the same cross section, the metal at A deforms faster than the metal at B, resulting in the metal at B exerting tensile stress on the metal at A, causing the bending of the steel head to be corrected under the tensile stress. Figure 3 shown.

[0038] Example 1

[0039] Ф210 hook bending solution implementation:

[0040] BD rolling mill + V1 vertical 850 rolling mill + H850 flat roll rolling mill + V3 vertical 850 rolling mill, producing 210mm round steel, the temperature of both sides is 953℃, 1002℃, resulting in rolling bending. 2# elliptical hole side wall 112°, bottom arc R400mm, rolling speed 0.4m / s, rolling piece contact hole type A point roller diameter 815.5mm, V A =0.363m / s, roller diameter at contact point B Ф722.2mm, V B =0.322m / s, V A >V BSpeed ​​difference. During the rolling deformation process, the deformation speed of point A is faster than that of point B. During the rolling deformation process, the metal flow at point A is subject to the tensile stress of the metal flow at point B. Under the tensile stress, the metal at point A flows toward the center of the hole, and the metal at point B flows away from the center of the hole. Finally, the metal speeds at points A and B are close to the same V A ≈V B The rolling deformation stress is basically symmetrical and equal, and the hook bend basically disappears.

[0041] Example 2

[0042] Ф250 hook bending solution implementation:

[0043] BD rolling mill + V1 vertical 850 rolling mill + H850 flat roll rolling mill + V3 vertical 850 rolling mill, producing 250mm round steel, the temperature of both sides is 933℃, 1105℃, resulting in rolling bending. 2# elliptical hole side wall 112°, bottom arc R800mm, rolling speed 0.430m / s, rolling piece contact hole type A point roller diameter 810mm, V A =0.387m / s, roller diameter at contact point B Ф735.5mm, V B =0.352m / s, V A >V B Speed ​​difference. During the rolling deformation process, the deformation speed of point A is faster than that of point B. During the rolling deformation process, the metal flow at point A is subject to the tensile stress of the metal flow at point B. Under the tensile stress, the metal at point A flows toward the center of the hole, and the metal at point B flows away from the center of the hole. Finally, the metal speeds at points A and B are close to the same V A ≈V B The rolling deformation stress is basically symmetrical and equal, and the hook bend basically disappears.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A special steel large bar hole speed difference straightening and bending method, characterized in that: The invention comprises the following steps: feeding the bent head of the rolled piece to be corrected into the speed difference straightening hole between the upper roller and the lower roller; on one side of the upper side or the lower side of the speed difference straightening hole, the left side of the bent head contacts the point A of the inner wall of the speed difference straightening hole, and the right side of the bent head contacts the point B of the inner wall of the speed difference straightening hole, wherein the vertical height of the point A is lower than the vertical height of the point B; in the same cross section, the metal deformation at the point A is faster than the metal deformation at the point B, and the metal at the point B generates tensile stress on the metal at the point A, so that the bending of the bent head of the rolled piece to be corrected is corrected under the action of the tensile stress.

2. The special steel large bar hole speed difference straightening and bending method according to claim 1 is characterized in that: The speed difference straightening hole is symmetrical up and down, and symmetrical left and right. The speed difference straightening hole on one of the upper side or the lower side includes a top arc surface, and the two sides of the top arc surface are respectively connected to the upper part of a side wall, and the lower part of the side wall is connected to the horizontal edge. The side wall is inclined from top to bottom toward the outer side of the top arc surface, and the angle between the side wall and the horizontal edge is an obtuse angle.

3. The special steel large bar hole speed difference straightening and bending method according to claim 1 is characterized in that: The angle range between the side wall and the vertical line, that is, the slope of the side wall, is 15°-22°.

4. The special steel large bar hole speed difference straightening and bending method according to claim 1 is characterized in that: The included angle between the side wall and the horizontal edge is 112°.

5. The special steel large bar hole speed difference straightening and bending method according to claim 1, characterized in that: The calculation formula of the slope of the side wall is as follows: α=0.635η*(D / 2-B k ) / h Among them, α is the side wall slope, η is the correction coefficient, D is the groove depth, B k is the hole width.

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