阅读说明：本技术 一种用于生产尖角方管的生产方法及生产装置 (Production method and production device for producing sharp-angle square tubes ) 是由 王丰祥 王泰来 王振伟 张兴桥 王建刚 邹国顺 孔祥周 颜继生 赵康宁 雷刚 杨 于 2021-07-29 设计创作，主要内容包括：本发明涉及冷轧型尖角方管生产技术领域,公开了一种用于生产尖角方管的生产方法及生产装置；生产方法为从钢带两边的四分之一处同时起两个直角边,进行双边起对称轧制工艺；使直角边轧制到一定角度后,再从钢带中部位置进行中部轧制；再进行焊接；生产装置包括设置在地面上的双边起对称轧制机构,设置在地面上的中部轧制机构,以及设置在所述双边起对称轧制机构、中部轧制机构之间的C型旋转立辊；本技术方案能够改进现有尖角方管生产工艺,降低生产中轧辊的调试难度,提高尖角方管生产精度,大大缩减生产成本。(The invention relates to the technical field of cold rolling type sharp-angled square tube production, and discloses a production method and a production device for producing the sharp-angled square tube; the production method comprises the steps of starting two right-angle sides from one quarter of two sides of a steel strip at the same time, and carrying out bilateral symmetric rolling process; after the right-angle side is rolled to a certain angle, the middle part of the steel strip is rolled; then welding is carried out; the production device comprises a bilateral starting symmetric rolling mechanism arranged on the ground, a middle rolling mechanism arranged on the ground and a C-shaped rotating vertical roller arranged between the bilateral starting symmetric rolling mechanism and the middle rolling mechanism; according to the technical scheme, the existing production process of the sharp-corner square tube can be improved, the debugging difficulty of the roller in production is reduced, the production precision of the sharp-corner square tube is improved, and the production cost is greatly reduced.)

1. A production method for producing a sharp-angled square tube is characterized in that two right-angle edges are formed at one quarter of two sides of a steel strip at the same time, and a bilateral symmetric rolling process is carried out; after the right-angle side is rolled to a certain angle, the middle part of the steel strip is rolled; then welding is carried out;

the method specifically comprises the following steps:

the method comprises the following steps: stock preparation

Confirming the width of the steel strip according to the size of the finally formed sharp-angled square tube, the bending loss and the welding seam gap, and then cutting the steel strip;

step two: roll forming

Placing the cut steel strip on a rolling roller for rough rolling and fine rolling;

the rough rolling is that the rolling roller bends the steel strip from the quarter of the two sides of the width of the steel strip simultaneously through rolling pressure, and the two sides of the steel strip are symmetrically rolled;

then, a narrow upper roller is adopted to roll the middle part above the steel strip and two lower rollers are adopted to roll the middle part below the steel strip, and the middle part of the steel strip is bent through rolling pressure;

the fine rolling is to roll four surfaces of the bent steel strip from the periphery by adopting rolling rollers simultaneously so as to form a square pipe with a sharp angle to be welded;

step three: tack welding

A guide vertical roller is adopted to accurately position the welding seam of the square pipe with the sharp corner to be welded; welding the positioned welding line by adopting extrusion welding equipment to obtain a sharp-angled square tube;

step four: post-weld truing

And shaping the sharp-angled square tube by adopting a burnishing roll and a tubular torsion device in sequence, sizing and straightening.

2. The method according to claim 1, wherein in the second step, the two-sided symmetrical rolling uses two sets of bottom flat rolling rolls located below the middle of the width of the steel strip, two sets of bottom rolling rolls located on both sides of the bottom flat rolling rolls, and two sets of top rolling rolls located above the steel strip to bend the steel strip from one quarter of the two sides of the width of the steel strip simultaneously; symmetrically rolling the two sides of the steel strip to bend the steel strip for 6 times;

wherein, the quarter of the two sides are simultaneously bent for 14 degrees for the first time;

bending the quarter parts of the two sides for 16 degrees at the same time for the second time;

thirdly, bending the quarter parts of the two sides for 16 degrees simultaneously;

fourthly, bending the quarter of the two sides for 10 degrees simultaneously;

fifthly, bending the quarter of the two sides for 10 degrees simultaneously;

and sixthly, bending the quarter of the two sides simultaneously by 12 degrees.

3. The method according to claim 1, wherein 3 middle rolling passes are continuously performed in the middle of the width of the steel strip to symmetrically bend the middle of the steel strip;

wherein, the total angle of the middle bending of the first steel strip is 24 degrees;

the total angle of the second time of bending the middle part of the steel strip is 28 degrees;

the total angle of the third bend in the middle of the strip was 24.

4. The method for producing a square angular tube according to claim 1, wherein the finish rolling in the second step is performed 3 times; the first time and the second time adopt two upper rollers and two lower rollers to finish rolling four surfaces; fine rolling the four surfaces by adopting an upper roller and a lower roller for the third time;

wherein, the middle part of the steel strip is bent for 8 degrees for the first time, and the quarter parts of the two sides are simultaneously bent for 6 degrees;

bending the middle part of the steel belt for 2 degrees for the second time, and simultaneously bending the quarter parts of the two sides for 2 degrees;

and thirdly, bending the middle part of the steel strip by 4 degrees, and simultaneously bending the quarter parts of the two sides by 4 degrees.

5. The method for producing a sharp-angled square tube according to claim 1, wherein the extrusion welding device is a two-roll extrusion welding device or a three-roll extrusion welding device.

6. The method for producing a pointed square tube according to claim 1, wherein the rough rolling, the finish rolling in the second step, and the tack welding in the third step are performed with the steel strip perpendicular to the ground;

after welding, the deflection device is adopted to enable the square tube with the sharp angle to be welded to horizontally enter the burnishing roll and sequentially pass through the burnishing roll, the tubular torsion device, the sizing device and the straightening device.

7. The method for producing the sharp-angled square tube according to claim 1, wherein the middle bending part and the quarter bending parts at two sides are both double-R arc wrap angles.

8. The production device for producing the sharp-angled square tubes, which is used in the production method according to any one of claims 1 to 7, is characterized by comprising a bilateral starting symmetric rolling mechanism (1) arranged on the ground, a middle rolling mechanism (2) arranged on the ground, and a C-shaped rotating vertical roll (3) arranged between the bilateral starting symmetric rolling mechanism (1) and the middle rolling mechanism (2);

the bilateral starting symmetric rolling mechanism (1) comprises a first fixed rack (10), 6 groups of first die roller sets (11) sequentially arranged on the first fixed rack (10), and a first power assembly (12) used for driving the first die roller sets (11) to rotate;

the first die roller group (11) comprises two groups of bottom flat rollers (110) which are arranged on the first fixed rack (10) and are positioned in the middle of the lower part of the steel belt, two groups of lower side rollers (111) which are coaxial with the bottom flat rollers (110) and are positioned on two sides of the steel belt, and upper rollers (112) which are arranged above the steel belt and vertically correspond to the bottom flat rollers (110);

the bottom flat roll (110) is contacted with the lower surface of the middle part of the steel strip; the lower edge rollers (111) are in contact with the lower surfaces of the two sides of the steel strip; the upper roller (112) is in contact with the upper surface of the steel strip;

the middle rolling mechanism (2) comprises a second fixed rack (20), 3 groups of second die roller sets (21) which are sequentially arranged on the second fixed rack (20), and a second power assembly (22) which is arranged on the second die roller sets (21) and used for driving the second die roller sets (21);

the second die roller group (21) comprises two lower rollers (210) which are coaxially provided with the lower surface of the steel strip, and a narrow upper roller (211) which is arranged above the lower rollers (210) and is contacted with the middle part of the upper surface of the steel strip.

9. The production device for producing the pointed square tube according to claim 8, wherein the upper rolls (112) of the first two sets of first die rolls (11) on the first fixed frame (10) are in contact with the middle and the side parts of the upper surface of the steel strip; the upper rollers (112) in the first die roller groups (11) of the rear four groups are only contacted with the middle part of the upper surface of the steel belt.

10. The method for producing the sharp-angled square tube according to claim 1, wherein the middle bending part and the quarter bending parts at two sides are both double-R arc wrap angles.

Technical Field

The invention relates to the technical field of cold rolling type sharp-angled square tube production, in particular to a production method and a production device for producing the sharp-angled square tube.

Background

With the continuous increase of investment and the vigorous development of housing industrialization of national infrastructure, large-scale engineering projects such as highways, railways, bridges, yard houses and the like and high-rise building projects show an order of magnitude growth situation, and the demand on cold-rolled sharp-angled square tubes is increasingly greater; because the process of the sharp-corner square tube is greatly different from that of a common steel tube, the process window is small in the production of the sharp-corner square tube, one corner is a right angle, and the other three corners are round corners and are difficult to adjust; compared with the common steel pipe, the falling mass production of the sharp-angled square pipe has higher technical barriers.

The rolling technology of the sharp-angled square steel seen in the market at present is generally unilateral, namely in the roll bending process, the square steel is firstly rolled from a right-angle side of the sharp-angled square steel, the right-angle side is rolled to a certain angle and then rolls the opposite side of the right-angle side with two round corners, and when the edges of the two round corners are rolled to a certain angle, a group of oblique inserting rollers is adopted to complete the remaining rolling process.

The existing production technology has great technical defects in actual production. Firstly, the requirement on the precision of an equipment unit is high, a plurality of special-shaped rollers are needed in the production process, and the difficulty in debugging products is increased; secondly, the steel strip is easy to deviate due to an asymmetric rolling process, and the precision of the produced sharp-corner square steel is low; thirdly, the production cost is high due to the low yield.

Disclosure of Invention

The technical problem solved by the invention is as follows: the existing production process of the sharp-corner square tube is improved, the debugging difficulty of the roller in production is reduced, the production precision of the sharp-corner square tube is improved, and the production cost is greatly reduced.

The technical scheme of the invention is as follows: a production method for producing a sharp-angled square tube is characterized in that two right-angle edges are formed at one quarter of two sides of a steel strip at the same time, and a bilateral symmetric rolling process is carried out; after the right-angle side is rolled to a certain angle, the middle part of the steel strip is rolled; then welding is carried out;

the method specifically comprises the following steps:

the method comprises the following steps: stock preparation

Confirming the width of the steel strip according to the size of the finally formed sharp-angled square tube, the bending loss and the welding seam gap, and then cutting the steel strip;

step two: roll forming

Placing the cut steel strip on a rolling roller for rough rolling and fine rolling;

the rough rolling is that the rolling roller bends the steel strip from the quarter of the two sides of the width of the steel strip simultaneously through rolling pressure, and the two sides of the steel strip are symmetrically rolled;

then, a narrow upper roller is adopted to roll the middle part above the steel strip and two lower rollers are adopted to roll the middle part below the steel strip, and the middle part of the steel strip is bent through rolling pressure;

the fine rolling is to roll four surfaces of the bent steel strip from the periphery by adopting rolling rollers simultaneously so as to form a square pipe with a sharp angle to be welded;

step three: tack welding

A guide vertical roller is adopted to accurately position the welding seam of the square pipe with the sharp corner to be welded; welding the positioned welding line by adopting extrusion welding equipment to obtain a sharp-angled square tube;

step four: post-weld truing

And shaping the sharp-angled square tube by adopting a burnishing roll and a tubular torsion device in sequence, sizing and straightening.

Further, in the second step, two sets of bottom flat rolling rollers positioned below the middle part of the width of the steel strip, two sets of lower side rolling rollers respectively positioned at two sides of the bottom flat rolling rollers and two sets of upper side rolling rollers positioned above the steel strip are adopted for symmetrically rolling the two sides of the steel strip, so that the steel strip is simultaneously bent from one fourth of the two sides of the width of the steel strip; symmetrically rolling the two sides of the steel strip to bend the steel strip for 6 times;

wherein, the quarter of the two sides are simultaneously bent for 14 degrees for the first time;

bending the quarter parts of the two sides for 16 degrees at the same time for the second time;

thirdly, bending the quarter parts of the two sides for 16 degrees simultaneously;

fourthly, bending the quarter of the two sides for 10 degrees simultaneously;

fifthly, bending the quarter of the two sides for 10 degrees simultaneously;

and sixthly, bending the quarter of the two sides simultaneously by 12 degrees.

Through the reasonable distribution of the bending deformation of the steel belt each time, the stress of each rack is uniform, and the service life of the equipment and the die roller is prolonged.

Further, continuously performing middle rolling for 3 times in the middle of the width of the steel strip to symmetrically bend the middle of the steel strip;

wherein, the total angle of the middle bending of the first steel strip is 24 degrees;

the total angle of the second time of bending the middle part of the steel strip is 28 degrees;

the total angle of the third bend in the middle of the strip was 24.

Through 3 times middle part bending, the middle part can form double R circular arc wrap angles, the stability of bending forming is ensured, the resilience is prevented, and the accuracy is improved.

Further, finish rolling in the second step is performed for 3 times; the first time and the second time adopt two upper rollers and two lower rollers to finish rolling four surfaces; fine rolling the four surfaces by adopting an upper roller and a lower roller for the third time;

wherein, the middle part of the steel strip is bent for 8 degrees for the first time, and the quarter parts of the two sides are simultaneously bent for 6 degrees;

bending the middle part of the steel belt for 2 degrees for the second time, and simultaneously bending the quarter parts of the two sides for 2 degrees;

and thirdly, bending the middle part of the steel strip by 4 degrees, and simultaneously bending the quarter parts of the two sides by 4 degrees.

The three bends can be 90 degrees through fine rolling, and the rolling precision of the sharp-angled square tube is guaranteed.

Further, the extrusion welding equipment is two-roller extrusion welding equipment or three-roller extrusion welding equipment.

Two rollers, three-roller extrusion welding equipment can ensure that even full weld is realized at right angle seam crossing, ensures that seam bottom also realizes the welding.

Further, the steel strip is perpendicular to the ground in the rough rolling, the fine rolling and the positioning welding in the third step;

after welding, the deflection device is adopted to enable the square tube with the sharp angle to be welded to horizontally enter the burnishing roll and sequentially pass through the burnishing roll, the tubular torsion device, the sizing device and the straightening device.

The product quality is better by using the rolling process of vertical rolling and horizontal rolling and fine shaping.

The production device for producing the sharp-corner square tubes further comprises a bilateral starting symmetric rolling mechanism arranged on the ground, a middle rolling mechanism arranged on the ground and a C-shaped rotating vertical roll arranged between the bilateral starting symmetric rolling mechanism and the middle rolling mechanism;

the bilateral starting symmetric rolling mechanism comprises a first fixed rack, 6 groups of first die roller sets sequentially arranged on the first fixed rack, and a first power assembly used for driving the first die roller sets to rotate;

the first die roller group comprises two groups of bottom flat rollers which are arranged on the first fixed rack and positioned in the middle of the lower part of the steel belt, two groups of lower side rollers which have the same axial lead with the bottom flat rollers and are positioned at two sides of the steel belt, and upper rollers which are arranged above the steel belt and vertically correspond to the bottom flat rollers;

the bottom flat roller is contacted with the lower surface of the middle part of the steel belt; the lower edge rollers are contacted with the lower surfaces of the two sides of the steel strip; the upper roller is in contact with the upper surface of the steel belt;

the middle rolling mechanism comprises a second fixed rack, 3 groups of second die roller sets sequentially arranged on the second fixed rack, and a second power assembly arranged for driving the second die roller sets;

the second die roller group comprises two lower rollers and a narrow upper roller, the lower rollers are coaxially arranged on the lower surface of the steel strip, and the narrow upper rollers are arranged above the lower rollers and are in contact with the middle of the upper surface of the steel strip.

The upper rollers in the first two groups of first die roller sets on the first fixed rack are in contact with the middle part and the side part of the upper surface of the steel strip; the upper rollers in the first die roller groups of the rear four groups are only contacted with the middle part of the upper surface of the steel belt.

The invention has the beneficial effects that: according to the production method and the production device for producing the sharp-angle square tube, the quarter parts at two sides of the steel strip can be simultaneously bent through bilateral symmetrical rolling, and the double-R arc wrap angle is formed through multiple times of bending; rolling the middle part of the steel strip through a narrow upper roller to realize the bending of the middle part and form a double-R arc wrap angle; the symmetrical rolling process is integrally used, so that the steel belt is not easy to deviate, and the precision of a sharp-corner square steel product can be greatly improved.

The special-shaped roller does not exist in the whole rolling process, the rolling mode of straightening up and down not only ensures that the rolling is easy to control and convenient to debug, but also greatly simplifies the production process, and can effectively reduce the production difficulty and the production cost; the whole rolling process of vertical rolling and flat rolling is adopted, and the product quality is better through the shaping and the correction of a burnishing roll, a tubular torsion device, a sizing device and a straightening device.

Drawings

FIG. 1 is a schematic structural view of embodiment 1 of the present invention;

FIG. 2 is a view showing a change in bending of a steel strip according to example 2 of the present invention;

FIG. 3 is a schematic view of embodiment 2 of the present invention, wherein a quarter of two sides are simultaneously bent by 14 degrees for the first time;

FIG. 4 is a schematic view of embodiment 2 of the present invention, wherein the quarter portions of the two sides are simultaneously bent by 16 degrees for the second time;

FIG. 5 is a schematic view of a third embodiment 2 of the present invention, in which the quarter portions of the two sides are simultaneously bent by 16 degrees;

FIG. 6 is a schematic view of a fourth embodiment 2 of the present invention, in which the quarter portions of the two sides are simultaneously bent by 10 degrees;

FIG. 7 is a schematic view of a fifth embodiment 2 of the present invention, in which the quarter portions of the two sides are simultaneously bent by 10 degrees;

FIG. 8 is a schematic view of a sixth bending of both sides by 12 degrees simultaneously in the embodiment 2 of the present invention;

FIG. 9 is a schematic illustration of a first 24 bend in the middle of a strip rolled in the middle of example 2 of the present invention;

FIG. 10 is a schematic illustration of a first 28 bend in the middle of a strip of a mid-rolled steel strip in accordance with example 2 of the present invention;

FIG. 11 is a schematic illustration of a first 24 bend in the middle of a strip rolled in the middle of example 2 of the present invention;

FIG. 12 is a schematic view of the first and second finish rolling in example 2 of the present invention;

FIG. 13 is a schematic drawing of a third finish rolling in example 2 of the present invention;

the rolling device comprises a 1-double-side starting symmetric rolling mechanism, a 10-first fixed rack, a 11-first die roller group, a 110-bottom flat roller, a 111-lower side roller, a 112-upper roller, a 12-first power assembly, a 2-middle rolling mechanism, a 20-second fixed rack, a 21-second die roller group, a 210-lower roller, a 211-narrow upper roller, a 22-second power assembly and a 3-C type rotating vertical roller.

Detailed Description

Example 1:

the production device for producing the square tubes with sharp corners as shown in fig. 1 comprises a bilateral starting symmetric rolling mechanism 1 arranged on the ground, a middle rolling mechanism 2 arranged on the ground, and a C-shaped rotating vertical roll 3 arranged between the bilateral starting symmetric rolling mechanism 1 and the middle rolling mechanism 2;

the bilateral starting symmetric rolling mechanism 1 comprises a first fixed rack 10, 6 groups of first die roller sets 11 sequentially arranged on the first fixed rack 10 and a first power assembly 12 used for driving the first die roller sets 11 to rotate;

the first die roller group 11 comprises two groups of bottom flat rollers 110 which are arranged on the first fixed frame 10 and are positioned in the middle of the lower part of the steel belt, two groups of lower side rollers 111 which are coaxial with the bottom flat rollers 110 and are positioned at two sides of the steel belt, and upper rollers 112 which are arranged above the steel belt and vertically correspond to the bottom flat rollers 110;

the bottom flat roll 110 is in contact with the lower surface of the middle part of the steel strip; the lower edge rollers 111 are in contact with the lower surfaces of the two sides of the steel strip; the upper roller 112 is in contact with the upper surface of the steel strip;

the middle rolling mechanism 2 comprises a second fixed rack 20, a second die roller group 21 and a second power assembly 22, wherein the second fixed rack 20 and the second die roller group 3 are sequentially arranged on the second fixed rack 20, and the second power assembly 22 is arranged for driving the second die roller group 21;

the second die roller group 21 includes two lower rollers 210 coaxially provided with the lower surface of the steel strip and a narrow upper roller 211 provided above the lower rollers 210 to contact the middle of the upper surface of the steel strip.

The upper rollers 112 in the first two groups of first die roller sets 11 on the first fixed frame 10 are contacted with the middle part and the side part of the upper surface of the steel strip; the upper rolls 112 of the last four first die roll sets 11 are only in contact with the middle of the upper surface of the steel strip.

The C-shaped rotating vertical roll 3, the first power assembly 12 and the second power assembly 22 are all commercially available components, and the specific product type can be selected by workers in the field according to needs.

Example 2:

a production method for producing a sharp-angled square tube specifically comprises the following steps:

the method comprises the following steps: stock preparation

Confirming the width of the steel strip according to the size of the finally formed sharp-angled square tube, the bending loss and the welding seam gap, and then cutting the steel strip;

step two: roll forming

Placing the cut steel strip on a rolling roller for rough rolling and fine rolling;

the rough rolling is that the rolling roller bends the steel strip from the quarter of the two sides of the width of the steel strip simultaneously through rolling pressure, and the two sides of the steel strip are symmetrically rolled; specifically, 6 groups of first die roller sets 11 are adopted;

then, a narrow upper roller is adopted to roll the middle part above the steel strip and two lower rollers are adopted to roll the middle part below the steel strip, and the middle part of the steel strip is bent through rolling pressure; specifically, 3 sets of second die roller sets 21 are adopted;

the middle bending part and the quarter bending parts at the two sides are double-R arc wrap angles;

the fine rolling is to roll four surfaces of the bent steel strip from the periphery by adopting rolling rollers simultaneously so as to form a square pipe with a sharp angle to be welded;

the bilateral symmetric rolling adopts two groups of bottom flat rolling rollers positioned below the middle part of the width of the steel strip, two groups of lower side rolling rollers respectively positioned at two sides of the bottom flat rolling rollers and two groups of upper side rolling rollers positioned above the steel strip to simultaneously bend the steel strip from one fourth of two sides of the width of the steel strip; symmetrically rolling the two sides of the steel strip to bend the steel strip for 6 times;

wherein, the quarter of the two sides are simultaneously bent for 14 degrees for the first time;

bending the quarter parts of the two sides for 16 degrees at the same time for the second time;

thirdly, bending the quarter parts of the two sides for 16 degrees simultaneously;

fourthly, bending the quarter of the two sides for 10 degrees simultaneously;

fifthly, bending the quarter of the two sides for 10 degrees simultaneously;

and sixthly, bending the quarter of the two sides simultaneously by 12 degrees.

Continuously performing middle rolling for 3 times in the middle of the width of the steel strip to symmetrically bend the middle of the steel strip;

wherein, the total angle of the middle bending of the first steel strip is 24 degrees;

the total angle of the second time of bending the middle part of the steel strip is 28 degrees;

the total angle of the third bend in the middle of the strip was 24.

Fine rolling is carried out for 3 times; the first time and the second time adopt two upper rollers and two lower rollers to finish rolling four surfaces; fine rolling the four surfaces by adopting an upper roller and a lower roller for the third time;

wherein, the middle part of the steel strip is bent for 8 degrees for the first time, and the quarter parts of the two sides are simultaneously bent for 6 degrees;

bending the middle part of the steel belt for 2 degrees for the second time, and simultaneously bending the quarter parts of the two sides for 2 degrees;

and thirdly, bending the middle part of the steel strip by 4 degrees, and simultaneously bending the quarter parts of the two sides by 4 degrees.

Step three: tack welding

A guide vertical roller is adopted to accurately position the welding seam of the square pipe with the sharp corner to be welded; welding the positioned welding line by adopting extrusion welding equipment to obtain a sharp-angled square tube; wherein, the extrusion welding equipment is three-roller extrusion welding equipment.

It should be noted that the steel strip is always perpendicular to the ground in the rough rolling, the fine rolling and the positioning welding in the second step;

step four: post-weld truing

After welding, the deflection device is adopted to enable the square tube with the sharp angle to be welded to horizontally enter the burnishing roll and sequentially pass through the burnishing roll, the tubular torsion device, the sizing device and the straightening device.

Example 3:

a production method for producing a sharp-angled square tube specifically comprises the following steps:

the method comprises the following steps: stock preparation

Confirming the width of the steel strip according to the size of the finally formed sharp-angled square tube, the bending loss and the welding seam gap, and then cutting the steel strip;

step two: roll forming

Placing the cut steel strip on a rolling roller for rough rolling and fine rolling;

the rough rolling is that the rolling roller bends the steel strip from the quarter of the two sides of the width of the steel strip simultaneously through rolling pressure, and the two sides of the steel strip are symmetrically rolled; specifically, 6 groups of first die roller sets 11 are adopted;

then, a narrow upper roller is adopted to roll the middle part above the steel strip and two lower rollers are adopted to roll the middle part below the steel strip, and the middle part of the steel strip is bent through rolling pressure; specifically, 3 sets of second die roller sets 21 are adopted;

the middle bending part and the quarter bending parts at the two sides are double-R arc wrap angles;

the fine rolling is to roll four surfaces of the bent steel strip from the periphery by adopting rolling rollers simultaneously so as to form a square pipe with a sharp angle to be welded;

the bilateral symmetric rolling adopts two groups of bottom flat rolling rollers positioned below the middle part of the width of the steel strip, two groups of lower side rolling rollers respectively positioned at two sides of the bottom flat rolling rollers and two groups of upper side rolling rollers positioned above the steel strip to simultaneously bend the steel strip from one fourth of two sides of the width of the steel strip; symmetrically rolling the two sides of the steel strip to bend the steel strip for 6 times;

wherein, the quarter of the two sides are simultaneously bent for 14 degrees for the first time;

bending the quarter parts of the two sides for 13 degrees at the same time for the second time;

thirdly, bending the quarter parts of the two sides for 13 degrees simultaneously;

fourthly, bending the quarter of the two sides at 13 degrees simultaneously;

fifthly, bending the quarter parts of the two sides for 13 degrees simultaneously;

and sixthly, bending the quarter of the two sides simultaneously by 12 degrees.

Continuously performing middle rolling for 3 times in the middle of the width of the steel strip to symmetrically bend the middle of the steel strip;

wherein, the total angle of the middle bending of the first steel strip is 26 degrees;

the total angle of the second time of bending the middle part of the steel strip is 24 degrees;

the total angle of the third bend in the middle of the strip was 26.

Fine rolling is carried out for 3 times; the first time and the second time adopt two upper rollers and two lower rollers to finish rolling four surfaces; fine rolling the four surfaces by adopting an upper roller and a lower roller for the third time;

wherein, the middle part of the steel strip is bent for 5 degrees for the first time, and the quarter parts of the two sides are simultaneously bent for 4 degrees;

bending the middle part of the steel belt for 5 degrees for the second time, and simultaneously bending the quarter parts of the two sides for 4 degrees;

and thirdly, bending the middle part of the steel strip by 4 degrees, and simultaneously bending the quarter parts of the two sides by 4 degrees.

Step three: tack welding

A guide vertical roller is adopted to accurately position the welding seam of the square pipe with the sharp corner to be welded; welding the positioned welding line by adopting extrusion welding equipment to obtain a sharp-angled square tube; wherein, the extrusion welding equipment is two-roller extrusion welding equipment. And in the rough rolling, the fine rolling and the positioning welding in the second step, the steel strip is always vertical to the ground.

Step four: post-weld truing

After welding, the deflection device is adopted to enable the square tube with the sharp angle to be welded to horizontally enter the burnishing roll and sequentially pass through the burnishing roll, the tubular torsion device, the sizing device and the straightening device.

Finally, it should be noted that the above embodiment is only a preferred embodiment of the present invention in practical production, and is not the only limitation of the technology implemented by the present invention, and different bending angle parameters and bending times of the first die roller set 11 and the second die roller set 21 can be reasonably adopted according to the parameters of the steel strip material property, the dimension specification, and the like of the actual production of the sharp-angled square tube.

Therefore, it will be appreciated by those skilled in the art that modifications may be made to the embodiments described above, and any such modifications, equivalents and alternatives falling within the spirit and principles of the present invention are intended to be included within the scope of the present invention.