Roller arc side wall pass opening design method based on pipe ovality control

Abstract

The invention relates to a roller arc side wall pass opening design method based on pipe ovality control. The roller arc side wall pass opening design method comprises the steps that the outer diameter and the wall thickness of a pipe blank, the outer diameter and the wall thickness of a finished pipe, a roller gap, the length of a deformation area and an arc side wall pass opening angle are input; determining a circular arc critical point O of a hole pattern opening area; the feeding amount in the pipe rolling process is input; further representing the circular arc radius of the hole pattern opening area; and after the outer diameter profile of the fed pipe coincides with the critical point O, the opening width of the circular arc side wall hole pattern can be calculated. The outer diameter contour line of the fed pipe is controlled to be located on the inner side of the critical point O, the uniformity of metal extrusion deformation can be achieved, the pipe rolling efficiency is improved, the ovality of the cold-rolled pipe in the rolling process is precisely controlled, and the size precision of a product is improved.

Description

Technical Field

[0001] This invention relates to the field of cold rolling technology for metal tubes, and in particular to a method for designing the opening of the arc-shaped sidewall of a roll based on the control of the tube's ellipticity. Background Technology

[0002] Cold-rolled seamless steel pipes are an important type of industrial pipe material, widely used in many fields. For example, in the petrochemical industry, due to their good pressure resistance and corrosion resistance, they are often used to transport various oils, gases, and chemical media; in the machinery manufacturing industry, thanks to their high precision and excellent mechanical properties, they are used as raw materials for manufacturing key components; and in the construction industry, they are suitable for building structures and decoration projects with high requirements for structural strength and appearance quality. Currently, in the production of cold-rolled seamless steel pipes, rolling with arc-shaped sidewall openings on the rolls is a common process. However, this process has significant drawbacks: Firstly, in traditional rolling, the feed rate of the pipe is not directly related to the arc-shaped sidewall opening, resulting in significant metal deformation. Due to the characteristics of the roll pass structure, the stress distribution on the metal as it passes through the rolls is uneven, leading to complex metal flow and difficulty in precisely controlling the degree of deformation. This not only increases energy consumption but also affects the uniformity of the internal microstructure of the pipe, thereby reducing its overall performance. Secondly, the rolled pipe has a large ellipticity. The traditional arc-shaped sidewall opening width is relatively small, resulting in greater flow constraint on the metal in the width direction, causing inconsistent deformation in different parts, ultimately leading to an ellipticity of the pipe cross-section exceeding the ideal range. Excessively elliptic pipes will affect the fitting accuracy with other components in subsequent use, reducing the stability and reliability of the entire system. Given the aforementioned drawbacks of the open-roll mill with circular arc sidewalls, there is an urgent need to improve it to reduce the ellipticity of the tube and make the metal deformation more uniform. This is of great significance for improving the quality and production efficiency of cold-rolled seamless steel tubes. It can not only meet the downstream industry's demand for high-precision tubes, but also effectively reduce the scrap rate and lower production costs. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method for designing the arc-shaped sidewall opening of a roll based on the control of tube ellipticity. By establishing the relationship between the feed rate and the metal flow at the arc-shaped sidewall opening, the maximum tube feed rate under a given opening is found, and the arc-shaped sidewall opening size is designed, which can reduce the ellipticity of the tube and improve the dimensional accuracy of the finished tube.

[0004] The technical solution adopted in this invention is as follows: The roll arc sidewall opening design method based on tube ellipticity control proposed in this invention specifically includes the following steps: Step 1: Determine the outer diameter of the tube blank and wall thickness Outer diameter of finished pipe and wall thickness Roll gap Length of deformation zone and the opening angle of the arc-shaped sidewall hole ; Step 2: Determine the angle bisector of the opening angle of the arc-shaped sidewall hole and the critical point O of the arc in the opening area of ​​the hole; Step 3: Input the feed rate for the pipe rolling process ; Step 4: Based on the critical point O and the feed rate Determine the radius of the arc in the opening area of ​​the hole. The radius of the arc of the aperture opening area is expressed by the following formula. :

[0005] in: For the pipe deformation section The radius of the center arc of the opening area of ​​the cross-section hole; The angle between the radius of the arc of the opening area of ​​the die and the side opening line of the roll groove; The angle between the radius of the arc in the opening area of ​​the hole and the center line of the arc; Step 5: Calculate the opening width of the arc-shaped sidewall hole using the following formula. :

[0006] in: for The radius of the arc of the opening area of ​​the time hole.

[0007] Furthermore, in step 1, the pipe is a small-diameter, thin-walled seamless steel pipe with a circular arc sidewall opening angle. The angle is 20°-35°; the roll gap is 1mm-2mm.

[0008] Furthermore, in step 2, the intersection of the angle bisector of the opening angle of the arc-shaped sidewall hole and the arc of the hole opening area is the critical point O.

[0009] Furthermore, in step 3, the feed rate of the tube rolling process is input. There is a maximum value when the radius of the arc in the orifice opening area approaches infinity, i.e., when the arc is approximately tangent, the feed rate... To maximize the feed rate, the feed amount is determined according to the following formula. Maximum value:

[0010] in: This is the total reduction ratio of the pipe's outer diameter; The total reduction ratio of the pipe's outer diameter is calculated using the following formula. :

[0011] Input the feed rate during the pipe rolling process There is a minimum value; the feed rate is determined when the radius of the arc of the die opening area is the same as the radius of the arc of the roll groove. Minimum value .

[0012] Furthermore, in step 4, the radius of the arc of the aperture opening area... Based on the center O1 of the hole cross-section, the center line of the arc of the hole opening area and the radius of the arc of the hole opening area are defined. It is based on the actual center O2 of the arc.

[0013] Furthermore, in step 4, the deformed section of the pipe... The radius of the center arc of the opening area of ​​the cross-section hole It is necessary to pass the critical point O and the feed rate. It is determined that when the critical point O is located in the deformed section of the pipe... The radius of the arc can be determined from the outer contour of the cross-section and calculated using the following formula. :

[0014] in: For the pipe deformation zone The radius of the arc of the roller groove at the cross-section.

[0015] Furthermore, in step 4, the angle between the radius of the arc of the aperture opening area and the center line of the arc is calculated using the following formula: .

[0016] Furthermore, in step 5, the width of the arc-shaped sidewall opening is calculated. At that time, the small arc segment of the opening in the roll gap area is approximated as a straight line.

[0017] Compared with the prior art, the present invention has the following advantages: The present invention, through the above technical solution, achieves a result with a known outer diameter of the tube blank. and wall thickness Outer diameter of finished pipe and wall thickness Roll gap Length of deformation zone and the opening angle of the arc-shaped sidewall hole Next, locate the critical point O of the arc-shaped opening area on the arc-shaped sidewall; input the feed rate of the pipe. ,limit The critical point O of the hole-shaped cross-section is located at The deformation section of the pipe is determined at the outer diameter of the pipe cross-section. The radius of the center arc of the opening area of ​​the cross-section hole Then determine the radius of the arc in the opening area of ​​the hole. The final calculation yielded the opening width of the arc-shaped sidewall hole. The design of the arc-shaped sidewall opening takes into account the effects of feed rate and metal deformation, which can effectively reduce severe metal deformation, thereby improving rolling efficiency, reducing the ovality of the tube, and improving the dimensional accuracy of the tube. Attached Figure Description

[0018] Figure 1 This is a flowchart of the roll arc sidewall opening design method based on tube ellipticity control proposed in this invention; Figure 2 This is a schematic diagram of the longitudinal and arc-shaped transverse sections of a cold-rolled seamless steel pipe. Figure 3 This is a critical schematic diagram of the transverse cross-section of a circular arc sidewall hole. Figure 4 Schematic diagram of the arc design for the arc-shaped opening area of ​​the arc-shaped sidewall hole; Figure 5 This is an enlarged schematic diagram of the arc-shaped sidewall opening and the roller gap area. Detailed Implementation

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] The Pilger cold rolling mill uses two rolls 1 and a mandrel 3 in the middle to extrude and roll the tube blank 2 into a small-diameter, thin-walled, seamless steel tube, such as... Figure 2 As shown, with the feeding of the tube, the opening degree of the arc-shaped sidewall die 4 is smaller than that of the straight sidewall die, resulting in greater deformation of the metal in the die opening area. This will increase the ellipticity of the tube during rolling, which will seriously affect the subsequent stable rolling. Therefore, it is necessary to control the feeding amount of the tube, establish the relationship between the feeding amount and the arc-shaped sidewall die opening, improve the uniformity of metal deformation, and control the ellipticity of the tube.

[0021] When the pipe is sent in After length, Specific parameters of the pipe's transverse cross-section at the location are as follows: Figure 3 As shown, the critical point O of the arc-shaped opening region of the arc-shaped sidewall is located at... On the outer diameter of the pipe cross-section, when the critical point O of the circular arc is located... The feed rate is less than or equal to the maximum allowable feed rate, located on the outer diameter of the pipe cross-section or on the outer side. At the same time, it can significantly reduce uneven deformation of metal and improve the ovality of pipes. Specific parameters and positional relationships are as follows: Figure 3 As shown.

[0022] When the center radius of the arc-shaped opening area of ​​the arc sidewall is obtained Then, the angle between the radius of the arc of the opening area of ​​the die and the edge line of the opening on the side of the roll groove is determined. and the angle between the radius of the arc of the aperture opening area and the center line of the arc. Calculate the radius of the arc in the opening area of ​​the hole. ,like Figure 4 As shown. Due to the small roll gap, the calculation of the arc-shaped sidewall opening width is... At that time, the small arc segment of the opening in the roll gap area is approximated as a straight line, such as... Figure 5 As shown.

[0023] See appendix Figure 1 The roll arc sidewall opening design method based on tube ellipticity control proposed in this invention specifically includes the following steps: Step 1: Determine the outer diameter of the tube blank and wall thickness Outer diameter of finished pipe and wall thickness Roll gap Length of deformation zone and the opening angle of the arc-shaped sidewall hole ; The tube is a small-diameter, thin-walled seamless steel pipe. Because the opening angle of the arc-shaped sidewall die is smaller than that of the straight sidewall, the metal deformation is relatively larger. Therefore, to better control the dimensional accuracy of the steel pipe and reduce problems such as ovality and wall thickness unevenness during rolling, the arc-shaped sidewall die opening angle is... Use 20°-35°; the roll gap should be 1mm-2mm.

[0024] Step 2: Determine the angle bisector of the opening angle of the arc-shaped sidewall hole and the critical point O of the arc in the opening area of ​​the hole; the intersection of the angle bisector of the opening angle of the arc-shaped sidewall hole and the arc in the opening area of ​​the hole is the critical point O.

[0025] Step 3: Input the feed rate for the pipe rolling process ; Input the feed rate during the pipe rolling process There is a maximum value (generally undesirable). When the radius of the arc in the orifice opening area approaches infinity, i.e., when the arc is approximately tangent, the feed rate... To maximize the feed rate, the feed volume can be determined using the following formula. Maximum value:

[0026] in: This is the total reduction ratio of the pipe's outer diameter.

[0027] The total reduction ratio of the pipe's outer diameter is calculated using the following formula. :

[0028] Input the feed rate during the pipe rolling process There is a minimum value (generally undesirable). When the radius of the arc of the die opening area is the same as the radius of the arc of the roll groove, the feed rate... Minimum value .

[0029] Step 4: Based on the critical point O and the feed rate Determine the radius of the arc in the opening area of ​​the hole. The radius of the arc of the aperture opening area is expressed by the following formula. :

[0030] in: For the pipe deformation section The radius of the center arc of the opening area of ​​the cross-section hole; The angle between the radius of the arc of the opening area of ​​the die and the side opening line of the roll groove; The angle between the radius of the arc in the opening area of ​​the hole and the center line of the arc.

[0031] radius of the arc of the aperture opening area Based on the center O1 of the hole cross-section, the center line of the arc of the hole opening area and the radius of the arc of the hole opening area are defined. It is based on the actual center O2 of the arc.

[0032] Pipe Deformation Section The radius of the center arc of the opening area of ​​the cross-section hole It is necessary to pass the critical point O and the feed rate. It is determined that when the critical point O is located in the deformed section of the pipe... The radius of the arc can be determined from the outer contour of the cross-section and calculated using the following formula. :

[0033] in: For the pipe deformation zone The radius of the arc of the roller groove at the cross-section.

[0034] The angle between the radius of the arc in the aperture area and the center line of the arc is calculated using the following formula: .

[0035] Step 5: Calculate the opening width of the arc-shaped sidewall hole using the following formula. :

[0036] in: for The radius of the arc of the opening area of ​​the time hole.

[0037] Because the roll gap is small, the calculation of the opening width of the arc-shaped sidewall is necessary. At that time, the small arc segment of the opening in the roll gap area is approximated as a straight line.

[0038] Determine the width of the arc-shaped sidewall opening. B x Subsequently, the designed arc-shaped sidewall opening facilitates the deformation and flow of metal, controls the ellipticity of the pipe, and improves the dimensional accuracy of the pipe.

[0039] The invention will be further illustrated below with specific examples: The method for designing the opening of the arc-shaped sidewall of a roll based on the ellipticity control of the tube includes the following steps: Step 1, determine the outer diameter of the tube blank. and wall thickness Outer diameter of finished pipe and wall thickness Roll gap Length of deformation zone and the opening angle of the arc-shaped sidewall hole ; Step 2: Determine the angle bisector of the opening angle of the arc-shaped sidewall hole and the critical point O of the arc in the opening area of ​​the hole; Step 3: Input the feed rate for the pipe rolling process. ; Step 4, based on the critical point O and the feed rate Determine the radius of the arc in the opening area of ​​the hole. The radius of the arc of the aperture opening area is expressed by the following formula. :

[0040] Step 5: Calculate the opening width of the arc-shaped sidewall hole using the following formula. , here x Taking 2 as an example, the relevant calculation formula is:

[0041] The critical point O is the intersection of the angle bisector of the opening angle of the arc-shaped sidewall hole and the arc of the hole opening area.

[0042] Input the feed rate during the pipe rolling process There is a maximum value (generally undesirable). When the radius of the arc in the orifice opening area approaches infinity, i.e., when the arc is approximately tangent, the feed rate... To maximize the feed rate, the feed volume is calculated using the following formula. The maximum value is 9.7 mm, and the relevant calculation formula is:

[0043] The total reduction ratio of the pipe's outer diameter is calculated using the following formula. The relevant calculation formula is:

[0044] Simultaneously input the feed rate during the pipe rolling process. There is a minimum value (generally undesirable). When the radius of the arc of the die opening area is the same as the radius of the arc of the roll groove, the feed rate... Minimum value .

[0045] The radius of the arc of the aperture area Based on the center O1 of the hole cross-section, the center line of the arc of the hole opening area and the radius of the arc of the hole opening area are defined. It is based on the actual center O2 of the arc.

[0046] Pipe Deformation Section The radius of the center arc of the opening area of ​​the cross-section hole It is necessary to pass the critical point O and the feed rate. It is determined that when the critical point O is located in the deformed section of the pipe... It can be determined from the outer contour of the cross-section, here x Taking 2 as an example, the center radius of the arc is calculated using the following formula. The relevant calculation formula is:

[0047] The angle between the radius of the arc of the aperture region and the center line of the arc can be calculated using the following formula. The relevant calculation formula is: .

[0048] Table 1. Location of the deformation section during pipe rolling and ellipticity of the finished pipe.

[0049] Experimental measurement data shows that when the feed rate is 2 mm and the opening angle is 25°, the difference between the major and minor axes of the tube at the initial position is only 0.12 mm. During the rolling process, the ellipticity of the tube gradually decreases, and the ellipticity of the finished tube reaches 0.376%. Compared with the traditional arc-shaped sidewall die, the ellipticity is better controlled, and the dimensional accuracy of the tube is significantly improved. Therefore, the arc-shaped sidewall die opening design method for controlling the ellipticity of cold-rolled tubes proposed in this invention has a significant effect on improving the ellipticity of tubes and enhancing dimensional accuracy.

[0050] All matters not covered in this invention are common knowledge.

[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for designing the opening of the arc-shaped sidewall of a roll based on the control of the ellipticity of the tube, characterized in that, The method includes the following steps: Step 1: Determine the outer diameter of the tube blank and wall thickness Outer diameter of finished pipe and wall thickness Roll gap Length of deformation zone and the opening angle of the arc-shaped sidewall hole ; Step 2: Determine the angle bisector of the opening angle of the arc-shaped sidewall hole and the critical point O of the arc in the opening area of ​​the hole; Step 3: Input the feed rate for the pipe rolling process ; Step 4: Based on the critical point O and the feed rate Determine the radius of the arc in the opening area of ​​the hole. The radius of the arc of the aperture opening area is expressed by the following formula. : in: For the pipe deformation section The radius of the center arc of the opening area of ​​the cross-section hole; The angle between the radius of the arc of the opening area of ​​the die and the side opening line of the roll groove; The angle between the radius of the arc in the opening area of ​​the hole and the center line of the arc; Step 5: Calculate the opening width of the arc-shaped sidewall hole using the following formula. : in: for The radius of the arc of the opening area of ​​the time hole.

2. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 1, characterized in that: In step 1, the pipe is a small-diameter, thin-walled seamless steel pipe with a rounded sidewall opening angle. The angle is 20°-35°; the roll gap is 1mm-2mm.

3. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 1, characterized in that: In step 2, the intersection of the angle bisector of the opening angle of the arc-shaped sidewall hole and the arc of the hole opening area is the critical point O.

4. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 1, characterized in that: In step 3, the feed rate of the tube rolling process is input. There is a maximum value when the radius of the arc in the orifice opening area approaches infinity, i.e., when the arc is approximately tangent, the feed rate... To maximize the feed rate, the feed amount is determined according to the following formula. Maximum value: in: This is the total reduction ratio of the pipe's outer diameter; The total reduction ratio of the pipe's outer diameter is calculated using the following formula. : Input the feed rate during the pipe rolling process There is a minimum value; the feed rate is determined when the radius of the arc of the die opening area is the same as the radius of the arc of the roll groove. Minimum value .

5. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 1, characterized in that: In step 4, the radius of the arc of the aperture area Based on the center O1 of the hole cross-section, the center line of the arc of the hole opening area and the radius of the arc of the hole opening area are defined. It is based on the actual center O2 of the arc.

6. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 5, characterized in that: In step 4, the deformed section of the pipe The radius of the center arc of the opening area of ​​the cross-section hole It is necessary to pass the critical point O and the feed rate. It is determined that when the critical point O is located in the deformed section of the pipe... The radius of the arc can be determined from the outer contour of the cross-section and calculated using the following formula. : in: For the pipe deformation zone The radius of the arc of the roller groove at the cross-section.

7. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 6, characterized in that: In step 4, the angle between the radius of the arc of the aperture area and the center line of the arc is calculated using the following formula: 。 8. The method for designing the arc-shaped opening of the roll sidewall based on tube ellipticity control according to claim 1, characterized in that: In step 5, the width of the arc-shaped hole opening on the sidewall is calculated. At that time, the small arc segment of the opening in the roll gap area is approximated as a straight line.

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