A method for sizing rolling of a casing steel pipe

Abstract

A sizing rolling method of oil jacket steel pipe adopts five sizing stands for sizing rolling. Firstly, finite element simulation analysis is carried out on the original pass set to determine the mechanism of the concave surface, and the control variable method is used to explore the influence of the deformation, ellipticity, deformation difference and ellipticity difference of the sizing stands on the depth of the concave surface. In the case of constant total deformation, the deformation and ellipticity of the single sizing stand are changed, and the deformation and ellipticity difference between the sizing stands are within the control range. A new pass set is designed to solve the concave surface of the oil jacket steel pipe. The depth of the concave surface is determined through finite element simulation, and the depth of the concave surface is reduced to 1mm. The pass set after the design is used for trial production, the depth of the concave surface is less than 1mm, the threading requirement is met, and cutting is not needed, thereby reducing the metal consumption and cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgy, and relates to a sizing rolling method of an oil jacket steel pipe. BACKGROUND

[0002] In the sizing rolling method of the oil jacket steel pipe, the existing sizing rack adopts a 3-sizing rack. The concave surface depth generated in the sizing process of the oil jacket steel pipe due to the bevel at both ends is about 3mm, which seriously affects the thread quality. Research shows that if the concave surface depth is less than 1.5mm, there is no effect on the thread quality.

[0003] When the oil jacket steel pipe passes through the two-roll fixed mandrel continuous pipe mill unit, the head and tail of the oil jacket steel pipe will produce a bevel due to uneven deformation. In the process of passing through the three-roll sizing sizing rack to the finished product, a concave surface with a depth of about 3mm is generated at a distance of about 650mm between the head and tail, which affects the quality of the oil jacket steel pipe and needs to be cut off, accounting for about 2% of the cutting loss, thereby increasing the metal consumption and cost.

[0004] Currently, the fixed mandrel continuous pipe mill unit generally has the problem of bevel at the end of the oil jacket steel pipe. The main reason is that the end of the oil jacket steel pipe is not constrained during deformation, the metal flow is not equal, which leads to uneven deformation of the oil jacket steel pipe, resulting in a bevel at the end of the oil jacket steel pipe. During the sizing process, the oil jacket steel pipe continues to deform. Due to the bevel problem, the end of the oil jacket steel pipe deforms unevenly, causing a concave surface with a depth of about 3mm to be generated at a distance of about 650mm from the head and tail during the process of entering and exiting the sizing rack, which seriously affects the subsequent thread quality of the oil jacket steel pipe and needs to be cut off. SUMMARY

[0005] The present application aims to provide a sizing rolling method of an oil jacket steel pipe, which solves the problem of concave surface generated on the surface of the oil jacket steel pipe due to the bevel at the end of the oil jacket steel pipe during the sizing process by optimizing the sizing deformation process through finite element, controls the concave surface depth within the range that does not affect the thread, improves the quality of the oil jacket steel pipe, and reduces the metal consumption.

[0006] The technical scheme of the present application is as follows:

[0007] A sizing rolling method of an oil jacket steel pipe, the key process steps are as follows:

[0008] (1) Design five sizing racks for reducing diameter, calculate the total reducing rate of the oil jacket steel pipe and distribute it to each sizing rack;

[0009] (2) Adjust the reducing rate of each sizing rack, follow the rule of decreasing in turn, and the reducing rates of the 1~5 sizing racks are 0.84%, 0.78%, 0.74%, 0.53% and 0.23% respectively;

[0010] (3) design 5 sizing rack ellipticity, follow the law of decreasing in turn and the last two sizing rack ellipticity close law, 1~5 sizing rack ellipticity is 1.014, 1.012, 1.011, 1.0035, 1 respectively;

[0011] (4) according to the sizing rack deformation and ellipticity, the sizing rack long semi axis and short semi axis are calculated, and the sizing rack is processed, the long semi axis of 1 sizing rack is 178.13, the short semi axis is 175.67, the long semi axis of 2 sizing rack is 176.57, the short semi axis is 174.68, the long semi axis of 3 sizing rack is 175.17, the short semi axis is 173.27, the long semi axis of 4 sizing rack is 173.6, the short semi axis is 173, and the 5 sizing rack is a circular sizing rack, the radius is 172.92.

[0012] Invention principle: firstly, the finite element simulation analysis is carried out on the original hole type unit, the mechanism of the concave surface is determined, the control variable method is used to explore the influence of the deformation amount, the ellipticity, the deformation amount difference and the ellipticity difference of the sizing rack on the concave surface depth, under the condition that the total deformation amount is unchanged, the deformation amount and the ellipticity of the single sizing rack are changed, and the deformation amount and the ellipticity difference between the sizing racks are within the control range, a new hole type unit for solving the concave surface of the oil jacket steel pipe is designed, the concave surface depth is determined through the finite element simulation, the concave surface depth is reduced to 1mm, the hole type after the design is used for trial production, the concave surface depth is less than 1mm, the threading requirement is met, and cutting is not needed, so that the metal consumption and the cost are reduced.

[0013] The effective effect of the application: the deformation amount and the ellipticity of the single sizing rack are reduced, the deformation of the oil jacket steel pipe is more uniform when passing through each sizing rack, especially when the elliptical sizing rack is transitioned to the circular sizing rack, the deformation is more coordinated, and the concave surface of the oil jacket steel pipe is not deepened. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The flow chart for the oil jacket steel pipe sizing rolling hole type of the method of the application.

[0015] Figure 2 The depth change graph of the existing technology 3 rack bevel and concave surface.

[0016] Figure 3 The concave surface depth simulation graph of the 5 sizing rack of the method of the application.

[0017] Figure 4 The concave surface depth physical graph of the 5 sizing rack of the method of the application.

[0018] In the figure, 1 is a sizing rack, 2 is an oil jacket steel pipe, and 3 is a concave surface. DETAILED DESCRIPTION

[0019] The embodiments will be described below with reference to the drawings.

[0020] Figure 1 As shown: the sizing rolling method of the oil jacket steel pipe of the application, the process flow is that the rough pipe after continuous rolling, in the sizing process, the number of sizing racks is designed according to the total deformation, and is distributed to each sizing rack according to the gradually decreasing rule, and the ovality of each sizing rack is designed according to the gradually decreasing rule, the major and minor axes of the sizing rack are determined to carry out finished product sizing rolling, five sizing racks are adopted, including the following steps:

[0021] (1) five sizing racks are designed for reducing diameter, the total reducing rate of the oil jacket steel pipe is calculated and distributed to each sizing rack.

[0022] (2) the reducing rate of the single sizing rack is adjusted, the reducing rate of the first to fifth sizing rack is 0.84%, 0.78%, 0.74%, 0.53% and 0.23% respectively according to the gradually decreasing rule.

[0023] (3) the ovality of the five sizing racks is designed, the first to fifth sizing rack ovality is 1.014, 1.012, 1.011, 1.0035 and 1 respectively according to the gradually decreasing rule and the last two sizing rack ovality close rule.

[0024] (4) the major and minor axes of the sizing rack are calculated according to the deformation and ovality of the sizing rack, and the sizing rack is processed, the major and minor axes of the first sizing rack are 178.13 and 175.67, the major and minor axes of the second sizing rack are 176.57 and 174.68, the major and minor axes of the third sizing rack are 175.17 and 173.27, the major and minor axes of the fourth sizing rack are 173.6 and 173, and the fifth sizing rack is a circular sizing rack with a radius of 172.92.

[0025] Figure 2As shown in the figure: the concave depth and bevel change diagram of the three sizing rack rolling, the simulation result analysis, the concave is the deepest when the bevel is 30°, the bevel and the concave depth change diagram. The deformation simulation diagram of the concave of the oil jacket steel pipe is consistent with the defects of the field object, the principle of the concave is determined, the end of the oil jacket steel pipe is warped and sunken when passing through the last sizing rack due to the bevel problem, the concave is formed, the concave is the deepest when the bevel is 30°; in the case that the total deformation amount is unchanged, the relationship between the deformation amount and the concave depth is determined by changing the single sizing rack deformation amount, the single sizing rack deformation amount is less than 1%, and the deformation amount gradually decreases with the sizing rack deformation amount; in the case that the total deformation amount is unchanged, the influence law of the ellipticity on the concave depth is determined by changing the ellipticity of the single sizing rack, the ellipticity gradually decreases with the sizing rack, and the ellipticity of the elliptical sizing rack is similar to that of the transition round sizing rack; the new pass is designed, the deformation amount and the ellipticity of each sizing rack are determined, the major axis and the minor axis are calculated, and the concave depth is determined; the trial production is carried out by using the pass parameters, and the concave depth of the finished product is determined to be within the required range. The pass parameters of the three sizing racks in the prior art are shown in table 1.

[0026] Figure 3 、 Figure 4 As shown in the figure: the concave simulation diagram and the object diagram of the new pass of the method of the application are shown in the figure, the concave depth is 0.6mm, the trial rolling oil jacket steel pipe exists concave, the deepest is about 0.8mm, the simulation result and the object result are consistent. The new pass parameters of the five sizing racks in the application are shown in table 2. At present, the five sizing racks belong to the technical scheme with the optimal number of sizing racks, the lowest energy consumption, and the concave depth is reduced within the range of not affecting the quality. If the number of sizing racks is further increased within the range allowed by the equipment, the deformation amount and the ellipticity of each sizing rack are further reduced, which will increase the energy consumption and the cost.

[0027] Table 1 pass parameters of three sizing racks

[0028] .

[0029] Table 2 pass parameters of five sizing racks

[0030] .

Claims

1. A method of sizing a casing steel pipe, characterized by: Adopt 5 sizing stands to roll; The key process steps are: (1) design 5 sizing stands to reduce the diameter, calculate the total reducing rate of the oil jacket steel pipe and distribute to each sizing stand; (2) adjust the reducing rate of single sizing stand, follow the law of decreasing in turn, the reducing rate of No. 1~5 sizing stand is 0.84%, 0.78%, 0.74%, 0.53%, 0.23% respectively; (3) design 5 sizing stand ellipticity, follow the law of decreasing in turn and the law of the ellipticity of the last two sizing stands close, the ellipticity of No. 1~5 sizing stand is 1.014, 1.012, 1.011, 1.0035, 1 respectively; (4) calculate the long semi-axis and short semi-axis of the sizing stand according to the deformation and ellipticity of the sizing stand, and process the sizing stand, the long semi-axis and short semi-axis of No. 1 sizing stand is 178.13, 175.67, the long semi-axis and short semi-axis of No. 2 sizing stand is 176.57, 174.68, the long semi-axis and short semi-axis of No. 3 sizing stand is 175.17, 173.27, the long semi-axis and short semi-axis of No. 4 sizing stand is 173.6, 173, the radius of No. 5 sizing stand is 172.92.

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