Hot rolling forming method for improving corner forming accuracy of thick-walled hexagonal steel pipes

Abstract

The invention discloses a hot rolling forming method capable of improving the corner forming accuracy of thick-walled hexagonal steel tubes, and solves the problem of how to improve the corner forming quality when hot rolling forming square tubes with hot-rolled seamless steel tubes as blanks. The hot-rolled seamless steel tubes are used as blanks for hot-rolled square tubes or rectangular tubes, and after preheating the hot-rolled seamless steel tube blanks to 800° C.-1000° C., continuous and gradual roll-bending is performed under the joint rolling of an outer roll group and an inner roll group of a roll-bending forming device. The roll-bending forming device comprises a blank feeding device, a roll-bending frame, a mandrel device, a mandrel supporting device and a roll holding device. The various devices cooperate with each other to roll the hot-rolled seamless steel tube blanks into square steel tubes or rectangular steel tubes. The continuous and gradual roll-bending of the seamless round tubes under the joint action of the outer roll group and the inner roll group is achieved, thereby improving the forming accuracy of the corners of the hexagonal steel tubes.

Description

Technical Field

[0001] The present invention relates to the technical field of hot-rolled seamless steel pipes, and in particular to a hot-rolling forming tool for thick-walled hexagonal steel pipes capable of improving corner forming quality. Background Art

[0002] Hexagonal steel tubes are used in construction fields such as steel structure, machinery manufacturing, and building frame construction. Currently, the forming processes of hexagonal steel tubes include hot rolling forming, cold drawing forming, and extrusion forming and welded square tube process. The cold drawing forming process has the defects of many steps, small deformation per pass, long production cycle and low forming efficiency. The welded hexagonal tube process uses hot-rolled strip steel as raw material, and is formed by multiple extrusion passes and welding. No heat treatment is performed during the entire process, and the stress generated during the extrusion forming process cannot be eliminated. For the welded hexagonal tube process, the cold-bent hexagonal steel tubes produced by this forming method, except for the limited area of ​​the bending angle, the material properties of the remaining parts of the tube body are basically similar to those of the parent body. In particular, the closure of the weld seam is not ideal, the forming process is unstable, and it is difficult to obtain high-quality products.

[0003] Hot-rolled seamless hexagonal tubes are suitable for mass production and have high production efficiency. Hot-rolled hexagonal steel tubes can destroy the casting structure of the steel ingot, refine the grains of the steel, and eliminate the defects of the microstructure, thereby making the steel structure denser and greatly improving the mechanical properties. However, during the hot rolling process, hexagonal steel tubes are prone to low forming accuracy, especially the problem of many corner forming defects. The defects include: asymmetry and fullness problems of corner forming, forming limit and internal corner cracking. If hot-rolled seamless steel tubes are used as billets, the forming efficiency of hot-rolled seamless hexagonal steel tubes can be greatly improved. However, how to improve the overall forming accuracy of the hexagonal steel tubes during hot rolling, especially to improve the quality of their corner forming, has become a difficult problem that needs to be solved on site. Summary of the Invention

[0004] The present invention provides a hot rolling forming method for thick-walled hexagonal steel pipes capable of improving corner forming quality, solving the technical problem of how to improve corner forming quality when hot rolling hexagonal steel pipes using hot-rolled seamless steel pipes as blanks.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The overall concept of the present invention is: hot-rolled seamless steel pipes are used as blanks for hot-rolled hexagonal tubes. After preheating the hot-rolled seamless steel pipe blanks to 800°C-1000°C, they are subjected to continuous and gradual roll bending under the joint rolling of an outer roll group and an inner roll group of a roll bending forming device; the roll bending forming device includes a blank feeding device, a roll bending frame, a mandrel device, a mandrel supporting device and a roll holding device; each device cooperates to roll the hot-rolled seamless steel pipe blank into a hexagonal steel pipe.

[0007] A hot rolling forming tool for thick-walled hexagonal steel pipes capable of improving the quality of corner forming, comprising a seamless round tube blank feeding mechanism, a blank conveying roller, a seamless round tube blank, a bite roll bending machine frame, a first roll bending machine frame, a second roll bending machine frame, a third roll bending machine frame, a fourth roll bending machine frame, a fifth roll bending machine frame, a sixth roll bending machine frame, a mandrel supporting device, a first mandrel holding roller device and a mandrel; a seamless round tube blank feeding mechanism is provided at the left end of the blank conveying roller, a first mandrel holding roller device, a bite roll bending machine frame, a first roll bending machine frame, a second roll bending machine frame, a third roll bending machine frame, a fourth roll bending machine frame, a fifth roll bending machine frame and a sixth roll bending machine frame, which are arranged in sequence from left to right, and a bite outer rolling group is provided in the bite roll bending machine frame, and a bite outer rolling group is provided in the bite roll bending machine frame. The three outer rollers in the roller group are arranged in an equilateral triangle; the left end of the mandrel passes through the sixth roller bending frame, the fifth roller bending frame, the fourth roller bending frame, the third roller bending frame, the second roller bending frame, the first roller bending frame and the bite roller bending frame from right to left in sequence, and is arranged on the left side of the bite roller bending frame, and the right end of the mandrel is arranged in the mandrel holding device; a first group of outer roller groups is arranged in the first roller bending frame, and the three outer rollers in the first group of outer roller groups are arranged in an equilateral triangle; a second group of outer roller groups is arranged in the second roller bending frame, and the three outer rollers in the second group of outer roller groups are also arranged in an equilateral triangle, and the three outer rollers in the first group of outer roller groups and the three outer rollers in the second group of outer roller groups form a right triangle in space along the left and right directions. Hexagonal rolling opening; a third group of outer rollers is provided in the third roll bending frame, and the three outer rollers in the third group of outer rollers are arranged in an equilateral triangle; a fourth group of outer rollers is provided in the fourth roll bending frame, and the three outer rollers in the fourth group of outer rollers are also arranged in an equilateral triangle, and the three outer rollers in the third group of outer rollers and the three outer rollers in the fourth group of outer rollers form a regular hexagonal rolling opening in space along the left and right directions; a fifth group of outer rollers is provided in the fifth roll bending frame, and the three outer rollers in the fifth group of outer rollers are arranged in an equilateral triangle; a sixth group of outer rollers is provided in the sixth roll bending frame, and the three outer rollers in the fifth group of outer rollers are also arranged in an equilateral triangle, and the fifth group of outer rollers The three outer rollers of the first group and the three outer rollers of the sixth group of outer rollers form a regular hexagonal rolling mouth in space along the left-right direction; on the mandrel, from left to right, the first group of inner angle forming rollers, the second group of inner angle forming rollers, the third group of inner angle forming rollers, the fourth group of inner angle forming rollers, the fifth group of inner angle forming rollers and the sixth group of inner angle forming rollers are arranged in sequence and at intervals; the first group of inner angle forming rollers and the first group of outer rollers are arranged correspondingly, the three outer rollers of the first group of outer rollers are respectively arranged on the 60°, 180° and 300° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel, and the three inner angle forming rollers of the first group of inner angle forming rollers are arranged on the 90°, 210° and 330° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel;The second group of inner angle forming rollers is arranged correspondingly to the second group of outer rollers. The three outer rollers in the second group of outer rollers are respectively arranged at 0°, 120° and 240° angle azimuth lines of a circular cross section perpendicular to the axis of the mandrel. The three inner angle forming rollers in the second group of inner angle forming rollers are arranged at 30°, 150° and 270° angle azimuth lines of a circular cross section perpendicular to the axis of the mandrel. The third group of inner angle forming rollers is arranged correspondingly to the third group of outer rollers, the fourth group of inner angle forming rollers is arranged correspondingly to the fourth group of outer rollers, the fifth group of inner angle forming rollers is arranged correspondingly to the fifth group of outer rollers, and the sixth group of inner angle forming rollers is arranged correspondingly to the sixth group of outer rollers. A seamless round tube billet is movably arranged on the billet conveying roller table. The right end of the seamless round tube billet is fed in and sleeved on the left end of the mandrel. The seamless round tube billet is fed to the right by the seamless round tube billet feeding mechanism.

[0008] A first set of guide rollers is provided at the left end of the mandrel, and a second set of guide rollers is provided at the right end of the mandrel; there are three guide rollers in the first set of guide rollers and three guide rollers in the second set of guide rollers.

[0009] The central axis of the triangular rolling mouth formed by the three outer rollers of each group of outer rollers coincides with the central axis of the mandrel; a spring is arranged between the guide roller and the mandrel to make the roller surface of the guide roller fit together with the inner surface of the seamless round tube blank; a second mandrel roller device and a third mandrel roller device are respectively arranged on the right side of the first mandrel roller device.

[0010] A hot rolling forming method for thick-walled hexagonal steel pipes capable of improving corner forming quality comprises a seamless round tube blank feeding mechanism, a blank conveying roller, a seamless round tube blank, a bite roll bending frame, a first roll bending frame, a second roll bending frame, a third roll bending frame, a fourth roll bending frame, a fifth roll bending frame, a sixth roll bending frame, a mandrel supporting device, a first mandrel holding roller device and a mandrel; the seamless round tube blank feeding mechanism is provided at the left end of the blank conveying roller, the first mandrel holding roller device is provided at the right end of the blank conveying roller, the bite roll bending frame, the first roll bending frame, the second roll bending frame, the third roll bending frame, the fourth roll bending frame, the fifth roll bending frame and the sixth roll bending frame are sequentially arranged on the blank conveying roller from left to right; the method is characterized by the following steps:

[0011] The first step is to determine the diameter of the seamless round tube billet according to the circumference of the pre-rolled thick-walled hexagonal steel tube; according to the diameter of the seamless round tube billet, select the mandrel;

[0012] The second step is to set a biting outer rolling roller group in the biting roll bending machine frame, set a first group of outer rolling roller group in the first roll bending machine frame, and the three outer rolling rollers in the first group of outer rolling roller group are arranged in an equilateral triangle; set a second group of outer rolling roller group in the second roll bending machine frame, and the three outer rolling rollers in the second group of outer rolling roller group are arranged in an equilateral triangle, and the three outer rolling rollers in the first group of outer rolling roller group and the three outer rolling rollers in the second group of outer rolling roller group form a regular hexagonal rolling opening in space along the left and right directions; according to the outer roller flower design drawing of the pre-rolled thick-walled hexagonal steel pipe, the installation positions of the biting outer rolling roller group, the three outer rolling rollers in the first group of outer rolling roller group, and the three outer rolling rollers in the second group of outer rolling roller group are determined respectively; the installation positions of the three outer rolling rollers in the third group of outer rolling roller group and the three outer rolling rollers in the fourth group of outer rolling roller group, as well as the installation positions of the three outer rolling rollers in the fifth group of outer rolling roller group and the three outer rolling rollers in the sixth group of outer rolling roller group are determined respectively by the same method;

[0013] Step 3: On the mandrel, from left to right, the first group of inner angle forming rollers, the second group of inner angle forming rollers, the third group of inner angle forming rollers, the fourth group of inner angle forming rollers, the fifth group of inner angle forming rollers and the sixth group of inner angle forming rollers are sequentially arranged at intervals; and the installation position of each group of inner angle forming rollers on the mandrel is determined according to the inner roller design drawing of the pre-rolled thick-walled hexagonal steel tube;

[0014] The fourth step is to pass the left end of the mandrel from right to left through the sixth roll bending frame, the fifth roll bending frame, the fourth roll bending frame, the third roll bending frame, the second roll bending frame, the first roll bending frame and the bite roll bending frame in sequence, and then set it on the left side of the bite roll bending frame, and the right end of the mandrel is set in the mandrel holding roller device; the first group of inner angle forming rollers is arranged corresponding to the first group of outer roller groups, and the three outer rollers in the first group of outer roller groups are respectively arranged on the 60°, 180° and 300° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel, and the three inner angle forming rollers in the first group of inner angle forming rollers are arranged on the 30°, 150° and 270° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel; the The two groups of inner angle forming rollers are arranged correspondingly to the second group of outer rollers. The three outer rollers in the second group of outer rollers are respectively arranged on the 0°, 120° and 240° azimuth lines of the circular cross section perpendicular to the axis of the mandrel. The three inner angle forming rollers in the second group of inner angle forming rollers are arranged on the 90°, 210° and 330° azimuth lines of the circular cross section perpendicular to the axis of the mandrel. In the same way, the third group of inner angle forming rollers are arranged correspondingly to the third group of outer rollers, the fourth group of inner angle forming rollers are arranged correspondingly to the fourth group of outer rollers, the fifth group of inner angle forming rollers are arranged correspondingly to the fifth group of outer rollers, and the sixth group of inner angle forming rollers are arranged correspondingly to the sixth group of outer rollers.

[0015] Step 5: Preheat the seamless steel tube billet to 800-1000℃, then, through the seamless tube billet feeding mechanism and the billet conveying roller, sleeve the right end of the preheated seamless tube billet on the first set of guide rollers on the right end of the mandrel; through the seamless tube billet feeding mechanism, feed the right end of the preheated seamless tube billet into the biting outer roller group in the first roll bending stand;

[0016] In the sixth step, the seamless round tube billet bitten by the outer rolling roller group is conveyed to the right and fed into the triangular rolling mouth of the first roll bending stand, and the right end of the seamless steel tube billet is subjected to the first forming rolling. Under the joint action of the first group of outer rolling rollers and the first group of inner angle forming rollers in the first roll bending stand, the right end of the seamless tube billet is rolled and then fed to the right; when the right end of the seamless round tube billet enters the triangular rolling mouth of the second roll bending stand, the right end of the seamless round tube billet is subjected to the second forming rolling under the joint action of the second group of outer rolling rollers and the second group of inner angle forming rollers in the second roll bending stand.

[0017] The seamless round tube billet rolled by the first and second roll bending stands is then sequentially fed into the third, fourth, fifth and sixth roll bending stands for rolling. After six passes of rolling, it is formed into a thick-walled hexagonal steel tube.

[0018] A mandrel supporting device is provided between the roll bending frames; before the seamless round tube blank is conveyed from left to right, the mandrel supporting device, the first mandrel holding roller device, the second mandrel holding roller device and the third mandrel holding roller device are in a mandrel holding working state; when the seamless round tube blank is conveyed from left to right, the mandrel supporting device, the first mandrel holding roller device, the second mandrel holding roller device and the third mandrel holding roller device are in a mandrel loosening working state in sequence; after the seamless round tube blank is conveyed from left to right, the mandrel supporting device, the first mandrel holding roller device, the second mandrel holding roller device and the third mandrel holding roller device are in a mandrel holding working state in sequence; the mandrel supporting device, the first mandrel holding roller device, the second mandrel holding roller device and the third mandrel holding roller device cooperate with each other to ensure the passability of the seamless round tube blank and at the same time ensure that the mandrel does not move.

[0019] The present invention uses hot-rolled seamless round tubes as blanks to roll-form hot-rolled seamless square or rectangular steel tubes, which can greatly improve the forming efficiency of square and rectangular tubes; the blanks are kept at a relatively high temperature and can be subjected to a small amount of supplementary heating to reach the temperature required for rolling, thereby reducing the energy consumption required for heating the blanks; the mandrel device of the present invention realizes continuous gradual roll bending of seamless round tubes under the joint action of the outer roller group and the inner roller group, thereby improving the forming accuracy of the corners of square or rectangular steel tubes; the inner rollers arranged on the mandrel device of the present invention can adjust their radial heights through pads, thereby realizing multiple uses of one core and realizing the forming of square tubes or torch-shaped tubes of different sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention;

[0021] Figure 2 This is a diagram showing the coordination relationship between the mandrel 4 and each group of outer rollers of the present invention;

[0022] Figure 3 This is a diagram showing the coordination relationship between the first set of outer rollers 19 and the first set of inner angle forming rollers 25 of the present invention;

[0023] Figure 4 It is a structural schematic diagram of the regular hexagonal rolling opening 31 formed in space by the first group of outer rollers 19 and the second group of outer rollers 20 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings:

[0025] A hot rolling forming tool for thick-walled hexagonal steel pipes that can improve the quality of corner forming, comprising a seamless round tube blank feeding mechanism 1, a blank conveying roller 2, a seamless round tube blank 3, a bite roll bending frame 5, a first roll bending frame 6, a second roll bending frame 7, a third roll bending frame 8, a fourth roll bending frame 9, a fifth roll bending frame 10, a sixth roll bending frame 11, a mandrel supporting device 15, a first mandrel holding roller device 12 and a mandrel 4; a seamless round tube blank feeding mechanism 1 is provided at the left end of the blank conveying roller 2, a first mandrel holding roller device 12, a bite roll bending frame 5, a first roll bending frame 6, a second roll bending frame 7, a third roll bending frame 8, a fourth roll bending frame 9, a fifth roll bending frame 10 and a sixth roll bending frame 11, from left to right, they are arranged in sequence at intervals, and a biting outer roller group 18 is provided in the biting roll bending frame 5, and the three outer rollers in the biting outer roller group 18 are arranged in an equilateral triangle; the left end of the mandrel 4, from right to left, passes through the sixth roll bending frame 11, the fifth roll bending frame 10, the fourth roll bending frame 9, the third roll bending frame 8, the second roll bending frame 7, the first roll bending frame 6 and the biting roll bending frame 5, and is arranged on the left side of the biting roll bending frame 5, and the right end of the mandrel 4 is arranged in the mandrel holding roller device 12; a first group of outer roller groups 19 are provided in the first roll bending frame 6, and the three outer rollers in the first group of outer roller groups 19 are arranged in an equilateral triangle, and a second group of outer roller groups 20 are provided in the second roll bending frame 7, and the second group of outer roller groups The three outer rollers in the first group of outer roller groups 19 and the three outer rollers in the second group of outer roller groups 20 form a regular hexagonal rolling opening 31 in the space along the left-right direction; the third group of outer roller groups 21 are provided in the third roll bending machine frame 8, and the three outer rollers in the third group of outer roller groups 21 are arranged in the shape of a regular triangle; the fourth group of outer roller groups 22 are provided in the fourth roll bending machine frame 9, and the three outer rollers in the fourth group of outer roller groups 22 are also arranged in the shape of a regular triangle; the three outer rollers in the third group of outer roller groups 21 and the three outer rollers in the fourth group of outer roller groups 22 form a regular hexagonal rolling opening in the space along the left-right direction; A fifth outer roller group 23 is provided in the frame 10, and the three outer rollers in the fifth outer roller group 23 are arranged in an equilateral triangle. A sixth outer roller group 24 is provided in the sixth roll bending frame 11, and the three outer rollers in the fifth outer roller group 23 are also arranged in an equilateral triangle. In addition, the three outer rollers in the fifth outer roller group 23 and the three outer rollers in the sixth outer roller group 24 form a regular hexagonal rolling opening in space along the left-right direction. On the mandrel 4, from left to right, a first group of inner angle forming rollers 25, a second group of inner angle forming rollers 26, a third group of inner angle forming rollers 27, a fourth group of inner angle forming rollers 28, a fifth group of inner angle forming rollers 29, and a sixth group of inner angle forming rollers 30 are sequentially arranged at intervals.The first group of inner angle forming rollers 25 is corresponding to the first group of outer rollers 19, and the three outer rollers in the first group of outer rollers 19 are respectively arranged on the 60°, 180° and 300° angular orientation lines of the circular cross-section perpendicular to the axis of the mandrel 4, and the three inner angle forming rollers in the first group of inner angle forming rollers 25 are respectively arranged on the 30°, 150° and 270° angular orientation lines of the circular cross-section perpendicular to the axis of the mandrel 4; the second group of inner angle forming rollers 26 is corresponding to the second group of outer rollers 20, and the three outer rollers in the second group of outer rollers 20 are respectively arranged on the 0°, 120° and 240° angular orientation lines of the circular cross-section perpendicular to the axis of the mandrel 4, and the three inner angle forming rollers in the second group of inner angle forming rollers 26 are respectively arranged on the 0°, 120° and 240° angular orientation lines of the circular cross-section perpendicular to the axis of the mandrel 4 The inner angle forming rollers are arranged at 90°, 210°, and 330° angles of the circular cross-section perpendicular to the axis of the mandrel 4; the third group of inner angle forming rollers 27 is arranged correspondingly to the third group of outer rollers 21, the fourth group of inner angle forming rollers 28 is arranged correspondingly to the fourth group of outer rollers 22, the fifth group of inner angle forming rollers 29 is arranged correspondingly to the fifth group of outer rollers 23, and the sixth group of inner angle forming rollers 30 is arranged correspondingly to the sixth group of outer rollers 24; a seamless round tube billet 3 is movably arranged on the billet conveying roller table 2, the right end of the seamless round tube billet 3 being fed in and sleeved onto the left end of the mandrel 4, and the seamless round tube billet 3 is fed rightward by the seamless round tube billet feeding mechanism 1.

[0026] A first set of guide rollers 16 is provided at the left end of the mandrel 4 , and a second set of guide rollers 17 is provided at the right end of the mandrel 4 ; there are three guide rollers in the first set of guide rollers 16 and three guide rollers in the second set of guide rollers 17 .

[0027] The central axis of the triangular rolling mouth formed by the three outer rollers of each group of outer rollers coincides with the central axis of the mandrel 4; a spring is arranged between the guide roller and the mandrel 4 to make the guide roller surface fit together with the inner surface of the seamless round tube blank 3; a second mandrel roller device 13 and a third mandrel roller device 14 are respectively arranged on the right side of the first mandrel roller device 12.

[0028] A hot rolling forming method for thick-walled hexagonal steel pipes capable of improving corner forming quality comprises a seamless round tube blank feeding mechanism 1, a blank conveying roller table 2, a seamless round tube blank 3, a bite roll bending frame 5, a first roll bending frame 6, a second roll bending frame 7, a third roll bending frame 8, a fourth roll bending frame 9, a fifth roll bending frame 10, a sixth roll bending frame 11, a mandrel supporting device 15, a first mandrel holding roller device 12 and a mandrel 4; the seamless round tube blank feeding mechanism 1 is provided at the left end of the blank conveying roller table 2, the first mandrel holding roller device 12, the bite roll bending frame 5, the first roll bending frame 6, the second roll bending frame 7, the third roll bending frame 8, the fourth roll bending frame 9, the fifth roll bending frame 10 and the sixth roll bending frame 11 are arranged in sequence from left to right; the method is characterized by the following steps:

[0029] The first step is to determine the diameter of the seamless round tube blank 3 according to the circumference of the pre-rolled thick-walled hexagonal steel tube; and select the mandrel 4 according to the diameter of the seamless round tube blank 3;

[0030] The second step is to set a bite outer roller group 18 in the bite roll bending frame 5, set a first group of outer roller group 19 in the first roll bending frame 6, and the three outer rollers in the first group of outer roller group 19 are arranged in an equilateral triangle. Set a second group of outer roller group 20 in the second roll bending frame 7, and the three outer rollers in the second group of outer roller group 20 are arranged in an equilateral triangle. In addition, the three outer rollers in the first group of outer roller group 19 and the three outer rollers in the second group of outer roller group 20 form a regular hexagonal shape in space along the left and right directions. The rolling mouth 31 is configured to determine the installation positions of the bite-in outer roller group 18, the three outer rollers in the first outer roller group 19, and the three outer rollers in the second outer roller group 20 according to the outer roller design drawing of the pre-rolled thick-walled hexagonal steel tube. The installation positions of the three outer rollers in the third outer roller group 21 and the three outer rollers in the fourth outer roller group 22, as well as the three outer rollers in the fifth outer roller group 23 and the three outer rollers in the sixth outer roller group 24 are determined in the same way.

[0031] Step 3: On the mandrel 4, from left to right, a first group of inner angle forming rollers 25, a second group of inner angle forming rollers 26, a third group of inner angle forming rollers 27, a fourth group of inner angle forming rollers 28, a fifth group of inner angle forming rollers 29 and a sixth group of inner angle forming rollers 30 are sequentially arranged at intervals; and the installation position of each group of inner angle forming rollers on the mandrel 4 is determined according to the inner roller design drawing of the pre-rolled thick-walled hexagonal steel tube;

[0032] The fourth step is to pass the left end of the mandrel 4 from right to left through the sixth roll bending frame 11, the fifth roll bending frame 10, the fourth roll bending frame 9, the third roll bending frame 8, the second roll bending frame 7, the first roll bending frame 6 and the bite roll bending frame 5 in sequence, and then set it on the left side of the bite roll bending frame 5, and the right end of the mandrel 4 is set in the mandrel holding roller device 12; the first group of inner angle forming rollers 25 and the first group of outer roller groups 19 are correspondingly arranged, and the three outer rollers in the first group of outer roller groups 19 are respectively arranged on the 60°, 180° and 300° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel 4, and the three inner angle forming rollers in the first group of inner angle forming rollers 25 are arranged on the 30°, 150° and 270° azimuth lines of the circular cross-section perpendicular to the axis of the mandrel 4; the The two groups of inner angle forming rollers 26 are arranged correspondingly to the second group of outer rollers 20. The three outer rollers in the second group of outer rollers 20 are respectively arranged at 0°, 120° and 240° angle azimuths of the circular cross section perpendicular to the axis of the mandrel 4. The three inner angle forming rollers in the second group of inner angle forming rollers 26 are arranged at 90°, 210° and 330° angle azimuths of the circular cross section perpendicular to the axis of the mandrel 4. In the same way, the third group of inner angle forming rollers 27 are arranged correspondingly to the third group of outer rollers 21, the fourth group of inner angle forming rollers 28 are arranged correspondingly to the fourth group of outer rollers 22, the fifth group of inner angle forming rollers 29 are arranged correspondingly to the fifth group of outer rollers 23, and the sixth group of inner angle forming rollers 30 are arranged correspondingly to the sixth group of outer rollers 24.

[0033] Step 5: Preheat the seamless steel tube billet 3 to 800-1000°C. Then, the right end of the preheated seamless tube billet 3 is sleeved on the first set of guide rollers 16 at the right end of the mandrel 4 through the seamless tube billet feeding mechanism 1 and the billet conveying roller 2. The right end of the preheated seamless tube billet 3 is fed into the biting outer roller group 18 in the first roll bending stand 5 through the seamless tube billet feeding mechanism 1.

[0034] In the sixth step, the seamless round tube billet 3 bitten by the outer rolling roller group 18 is conveyed to the right and fed into the triangular rolling mouth of the first roll bending stand 6, and the right end of the seamless steel tube billet 3 is subjected to the first forming rolling. Under the joint action of the first group of outer rolling rollers 19 and the first group of inner angle forming rollers 25 in the first roll bending stand 6, the right end of the seamless tube billet 3 is rolled and fed to the right; when the right end of the seamless round tube billet 3 enters the triangular rolling mouth of the second roll bending stand 7, the right end of the seamless round tube billet 3 is subjected to the second forming rolling under the joint action of the second group of outer rolling rollers 20 and the second group of inner angle forming rollers 26 in the second roll bending stand 7, and the right end of the seamless round tube billet 3 is rolled into a hexagon.

[0035] The seamless round tube billet 3 rolled by the first roll bending stand 6 and the second roll bending stand 7 is then sequentially fed into the third roll bending stand 8, the fourth roll bending stand 9, the fifth roll bending stand 10 and the sixth roll bending stand 11 for rolling. After six passes of rolling, a thick-walled hexagonal steel tube is formed.

Claims

1. A hot rolling forming method for thick-walled hexagonal steel pipes capable of improving the quality of corner forming, comprising a seamless round pipe blank feeding mechanism (1), a blank conveying roller (2), a seamless round pipe blank (3), a bite roll bending frame (5), a first roll bending frame (6), a second roll bending frame (7), a third roll bending frame (8), a fourth roll bending frame (9), a fifth roll bending frame (10), a sixth roll bending frame (11), a mandrel supporting device (15), a first mandrel holding roller device (1 2) and a mandrel (4); a seamless round tube billet feeding mechanism (1) is provided at the left end of the billet conveying roller (2); a first mandrel roller holding device (12) is provided at the right end of the billet conveying roller (2); a bite roll bending frame (5), a first roll bending frame (6), a second roll bending frame (7), a third roll bending frame (8), a fourth roll bending frame (9), a fifth roll bending frame (10) and a sixth roll bending frame (11) are arranged in sequence from left to right; it is characterized in that Follow these steps: The first step is to determine the diameter of the seamless round tube blank (3) according to the circumference of the pre-rolled thick-walled hexagonal steel tube; and select the mandrel (4) according to the diameter of the seamless round tube blank (3); The second step is to set a bite outer roller group (18) in the bite roll bending frame (5), set a first outer roller group (19) in the first roll bending frame (6), and the three outer rollers in the first outer roller group (19) are arranged in an equilateral triangle. The second outer roller group (20) is set in the second roll bending frame (7), and the three outer rollers in the second outer roller group (20) are arranged in an equilateral triangle. In addition, the three outer rollers in the first outer roller group (19) and the three outer rollers in the second outer roller group (20) form a regular hexagon in space along the left and right directions. The square rolling mouth (31) is used to determine the installation positions of the bite-in outer roller group (18), the three outer rollers in the first outer roller group (19), and the three outer rollers in the second outer roller group (20) according to the outer roller design drawing of the pre-rolled thick-walled hexagonal steel tube; the installation positions of the three outer rollers in the third outer roller group (21) and the three outer rollers in the fourth outer roller group (22), as well as the installation positions of the three outer rollers in the fifth outer roller group (23) and the three outer rollers in the sixth outer roller group (24) are determined by the same method; Step 3: On the mandrel (4), from left to right, a first group of inner angle forming rollers (25), a second group of inner angle forming rollers (26), a third group of inner angle forming rollers (27), a fourth group of inner angle forming rollers (28), a fifth group of inner angle forming rollers (29) and a sixth group of inner angle forming rollers (30) are sequentially arranged at intervals; and the installation positions of the respective groups of inner angle forming rollers on the mandrel (4) are determined according to the inner roller design drawing of the pre-rolled thick-walled hexagonal steel tube; Step 4: The left end of the mandrel (4) is passed through the sixth roll bending frame (11), the fifth roll bending frame (10), the fourth roll bending frame (9), the third roll bending frame (8), the second roll bending frame (7), the first roll bending frame (6) and the bite roll bending frame (5) from right to left, and then is set on the left side of the bite roll bending frame (5). The right end of the mandrel (4) is set in the first mandrel holding roller device (12); The first group of inner angle forming rollers (25) is arranged correspondingly to the first group of outer rollers (19), and the three outer rollers in the first group of outer rollers (19) are respectively arranged on the 60°, 180° and 300° azimuth lines of the circular cross section perpendicular to the axis of the mandrel (4), and the three inner angle forming rollers in the first group of inner angle forming rollers (25) are arranged on the 30°, 150° and 270° azimuth lines of the circular cross section perpendicular to the axis of the mandrel (4); the second group of inner angle forming rollers (26) is arranged correspondingly to the second group of outer rollers (20), and the three outer rollers in the second group of outer rollers (20) are respectively arranged on the 30°, 150° and 270° azimuth lines of the circular cross section perpendicular to the axis of the mandrel (4). On the 0°, 120° and 240° angle azimuth lines of the circle, three inner angle forming rollers in the second group of inner angle forming rollers (26) are arranged on the 90°, 210° and 330° angle azimuth lines of the circular cross section perpendicular to the axis of the mandrel (4); in the same manner, the third group of inner angle forming rollers (27) are arranged correspondingly to the third group of outer rollers (21), the fourth group of inner angle forming rollers (28) are arranged correspondingly to the fourth group of outer rollers (22), the fifth group of inner angle forming rollers (29) are arranged correspondingly to the fifth group of outer rollers (23), and the sixth group of inner angle forming rollers (30) are arranged correspondingly to the sixth group of outer rollers (24); Step 5: preheat the seamless round tube billet (3) to 800°C-1000°C, then, through the seamless round tube billet feeding mechanism (1) and the billet conveying roller (2), sleeve the right end of the preheated seamless round tube billet (3) on the first set of guide rollers (16) at the right end of the mandrel (4); through the seamless round tube billet feeding mechanism (1), feed the right end of the preheated seamless round tube billet (3) into the biting outer roller group (18) in the biting roller bending frame (5) and bite it; Step 6: The seamless round tube billet (3) bitten by the outer roller group (18) is conveyed to the right and fed into the triangular rolling mouth of the first roller bending stand (6), and the right end of the seamless round tube billet (3) is subjected to the first forming rolling. Under the joint action of the first group of outer rollers (19) and the first group of inner angle forming rollers (25) in the first roller bending stand (6), the right end of the seamless round tube billet (3) is rolled and fed to the right; when the right end of the seamless round tube billet (3) enters the triangular rolling mouth of the second roller bending stand (7), the right end of the seamless round tube billet (3) is subjected to the second forming rolling under the joint action of the second group of outer rollers (20) and the second group of inner angle forming rollers (26) in the second roller bending stand (7).

2. The hot rolling forming method of a thick-walled hexagonal steel pipe capable of improving corner forming quality according to claim 1, characterized in that: The seamless round tube billet (3) rolled by the first roller bending frame (6) and the second roller bending frame (7) is then sequentially fed into the third roller bending frame (8), the fourth roller bending frame (9), the fifth roller bending frame (10) and the sixth roller bending frame (11) for rolling. After six passes of rolling, the billet is formed into a thick-walled hexagonal steel tube.

3. The hot rolling forming method of thick-walled hexagonal steel pipe capable of improving corner forming quality according to claim 1, characterized in that: The central axis of the triangular rolling mouth formed by the three outer rollers of each group of outer rollers coincides with the central axis of the mandrel (4); a second mandrel holding roller device (13) and a third mandrel holding roller device (14) are respectively provided on the billet conveying roller table (2) on the right side of the first mandrel holding roller device (12).

4. A hot rolling forming method for thick-walled hexagonal steel pipes capable of improving corner forming quality according to claim 1 or 2, characterized in that: A first guide roller group (16) is provided at the left end of the mandrel (4), and a second guide roller group (17) is provided at the right end of the mandrel (4); the number of guide rollers in the first guide roller group (16) and the number of guide rollers in the second guide roller group (17) are both three.

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