A seamless steel pipe processing method and production line based on automatic pipe rolling mill

Abstract

The present invention relates to the field of seamless steel pipe processing, and in particular discloses a seamless steel pipe processing method based on an automatic pipe rolling machine, including an initial rolling pass and a finishing pass, wherein the hollow rough pipe obtained by the previous process is rolled 1 or 2 times by the initial rolling pass, and then the initial rolling rough pipe is moved into the finishing pass and rolled at least 2 times to obtain the finishing rough pipe; the ovality of the finishing pass is smaller than the ovality of the initial rolling pass. The wall thickness of the steel pipe processed based on this scheme is uniform and the yield rate is high.

Description

Technical Field

[0001] This scheme involves the rolling process of hot-rolled seamless steel pipes, specifically the automatic pipe rolling machine, rolling process and production line in the pipe rolling process of the automatic pipe rolling unit. Background Art

[0002] Since its invention in 1903, the automatic tube rolling mill has been one of the main production units for hot-rolled seamless steel pipes. The complete rolling process of the automatic tube rolling mill is as follows: the heated tube billet is sent to the oblique rolling piercing machine, which pierces the solid tube billet into a hollow rough tube, and the hollow rough tube is sent to the automatic tube rolling mill, which reduces the diameter and wall of the hollow rough tube into a rough tube by the automatic tube rolling mill, and the rough tube is sent to the leveling machine, which levels the wall thickness of the rough tube to become a rough tube with high wall thickness accuracy, and the rough tube from the leveling machine is sent to the sizing machine, which presses down and regularizes the outer diameter of the rough tube to obtain a high-temperature finished tube, and the high-temperature finished tube is then cooled, cut, inspected and tested (collectively referred to as finishing), and finally a finished seamless steel tube is obtained.

[0003] Since the working rhythm of the leveling machine is lower than that of the automatic tube rolling machine, to realize the above complete process, one automatic tube rolling machine needs to be equipped with two leveling machines. In addition, the rough tubes rolled by the automatic tube rolling machine have ovality, full-length bending and low temperature. The two leveling machines often get stuck during operation, especially when rolling thin-walled tubes, which affects the smooth operation of the production line. When the above production line is introduced in China, the leveling machine process is often omitted based on cost and production smoothness considerations. That is, the existing automatic tube rolling machines in China generally do not have the leveling machine program, which leads to the low wall thickness accuracy of the steel tubes processed by the existing automatic tube rolling machine production lines in China.

[0004] With the development of society, all walks of life have continuously improved their requirements for product quality. The products produced by the automatic tube rolling machine production line that omitted the leveling machine in order to save costs can no longer meet the market demand and are gradually being idled and eliminated. Relevant foreign companies have also continuously tried to upgrade and transform the automatic tube rolling machine production line, but the results have not been ideal.

[0005] We have conducted an in-depth analysis of the problems existing in automatic tube rolling machines and believe that the biggest problem with the steel pipes produced by automatic tube rolling machines is the large deviation in wall thickness of the rough tubes, which affects the yield rate.

[0006] The automatic tube rolling mill consists of four parts: the main machine, the return roller, the front stage and the back stage. The main machine is a two-roller irreversible longitudinal rolling mill. Figure 1As shown, a pair of high-speed reverse-rotating return rollers 12 are installed behind the working rollers 11. At the same time, in order to meet the needs of the return rollers 12, a rapid lifting mechanism for the upper working rollers 11 and the lower return rollers 12 is provided. When the steel pipe is rolled from the front stage to the back stage, the steel pipe only contacts the working rollers and does not contact the return rollers. After rolling is completed, the entire steel pipe completely passes through the working rollers, and the top 14 falls off under the action of its own gravity. At this time, the upper working rollers 11 and the lower return rollers 12 are lifted up, leaving enough space for the steel pipe to return between the upper working rollers and the lower working rollers. The lifting action allows the lower return roller 12 to contact the steel pipe, while the lower working roller 11 is out of contact with the steel pipe. Under the action of the two return rollers 12, the steel pipe quickly returns to the front stage. Compared with previous rolling mills, this steel pipe return process is automatically realized, so it is called an automatic pipe rolling mill.

[0007] like Figure 2 As shown, the working roll 11 is provided with a circular hole groove. Figure 1 In the process, the rough pipe 15 sent from the previous process is rolled in the annular hole formed by the circular hole groove and the plug 14 to achieve diameter reduction and wall reduction shaping.

[0008] Usually, two passes are rolled. The product obtained after the first pass is called the primary rough pipe 151, and the product obtained after the second pass is called the secondary rough pipe. After each pass, the upper working roll 11 and the lower return roll 12 are lifted to a certain height, and the primary rough pipe 151 or the rough pipe is sent back to the front desk by the return roll 12, and then the roll 11 is restored to its original working position, and the primary rough pipe 151 is turned 90°, and then the second pass is rolled in the same hole groove to obtain the secondary rough pipe. If only two passes are required in the process, the secondary rough pipe is actually the finished rough pipe. After the rolled rough pipe is sent back to the front desk, it is moved horizontally to the next process.

[0009] From the above, purely for the automatic tube rolling machine itself, the uneven wall thickness of the rolled steel tube is mainly caused by two reasons:

[0010] 1. Causes of hole type:

[0011] refer to Figure 2 As shown in the figure (the upper and lower hole grooves are symmetrical, only the upper half of the hole groove is marked in the figure), there is an angle of φ=30° to 32° from the side wall of the circular hole groove to the roll gap, which is called the hole opening angle. The corresponding hole ellipticity is 1.04 to 1.05, that is, the ratio of the diameter b at the roll gap to the diameter a at the bottom of the hole groove: b / a=(1.04 to 1.05). The upper radius R2 of this section is greater than the radius R1 of the bottom of the hole, that is, the roll gap between the head and the bottom of the hole groove is small, and the roll gap between the head and the side wall is large, so as to meet the needs of lateral flow of metal:

[0012] When the φ angle is small, the wall thickness of the processed steel pipe is more uniform, while when the φ angle is large, the wall thickness of the processed steel pipe is less uniform. However, when the φ angle is small, it is easy to have difficulty in biting during rolling, and the rolled steel pipe is easily squeezed into the roll gap due to the lack of sufficient lateral flow space, forming ribs on the steel pipe (commonly known as ears). Therefore, almost all automatic pipe rolling mill manufacturers choose φ = 30 to 32°.

[0013] Since the automatic tube rolling machine needs to transport the rolled tube back to the front desk, the transportation process takes a certain amount of time. In order to improve the processing efficiency and save the return time, a double-hole processing method was later developed, that is, two round hole grooves are set, and the first rough tube is rolled in the first round hole groove for the first time to obtain the first primary rough tube 151, and then the first primary rough tube 151 is translated to the position corresponding to the second round hole groove in the front desk, and the second rolling is carried out to obtain the first secondary rough tube. This first secondary rough tube is not immediately sent back to the front desk, but waits in the back desk. At this time, the second rough tube is rolled in the first round hole groove for the first time to obtain the second primary rough tube 151 to the back desk, and then the first secondary rough tube and the second primary rough tube 151 are transported back to the front desk at the same time, thereby saving the time for the rough tube to be transported back to the front desk and improving work efficiency. However, in the prior art, in this processing method, no matter how many times the rolling is performed, the first round hole groove and the second round hole groove use the same hole type.

[0014] Please note that in the following text, "steel pipe" will be used as a general term when there is no need to distinguish between rough pipes, primary rough pipes, secondary rough pipes, etc.

[0015] In summary, whether rolling two passes in one circular hole groove, or rolling the first pass in the first circular hole groove and the second pass in the second circular hole groove, in the existing rolling process, the hole profile experienced by the steel pipe is the same, and the hole profile with an opening angle φ=30 to 32° is used.

[0016] 2. Causes of top:

[0017] In the automatic tube rolling machine, the surface finish of the spherical plug that forms the annular hole is poor, the hardness is low, and the friction coefficient with the metal is large, which hinders the longitudinal extension of the metal, increases the lateral flow of the metal, and increases the lateral wall thickness unevenness;

[0018] Based on the above technical problems, if the above problems of automatic pipe rolling machine can be solved, it will be of great value to revitalize the existing idle and backward automatic pipe rolling machine production line resources. Summary of the invention

[0019] The technical problem to be solved by the present invention is to provide a seamless steel pipe processing method based on an automatic pipe rolling mill.

[0020] The specific technical solution of the present invention to solve the above technical problems is:

[0021] It includes an initial rolling pass and a finishing rolling pass. The hollow rough tube obtained by the previous process is rolled 1 or 2 times by the initial rolling pass (called: initial rolling rough tube), and then moved into the finishing rolling pass and rolled twice to obtain the finishing rough tube; the ovality and opening degree of the finishing rolling pass are smaller than the ovality and opening degree of the initial rolling pass.

[0022] According to the present scheme, the wall thickness reduction of the rough tube is large when the rough tube enters the automatic tube rolling machine for rolling, that is, the deformation of the first rolling is large, so the first rolling is carried out by using the existing hole type (hereinafter referred to as the initial rolling hole type). According to the process requirements, the second rolling can also be selected to obtain the rough tube with a large difference in wall thickness. After that, the rough tube is rolled for two times in the finishing hole type to obtain the finished rough tube. Since the finishing hole type has a smaller ellipticity and a smaller opening than the rough tube type, the space for the lateral flow of metal in the steel tube is small, and the steel tube mainly extends longitudinally during the rolling process, the lateral wall thickness of the steel tube after rolling with the finishing hole type will be more uniform, and the rough tube rolled with the initial rolling hole type has a smaller deformation in the finishing hole type than the rough tube, so it can be smoothly bitten into the roller without biting difficulties or ear problems. The steel tube processed by the above scheme has a more uniform lateral wall thickness and a high yield rate.

[0023] Furthermore, the preliminary rolling pass and the finishing rolling pass are both formed by the cooperation of the rolling groove and the head to form an annular working pass, the rolling groove includes an upper rolling groove and a lower rolling groove which are distributed up and down, have the same structure and rotate in opposite directions, the butt joint between the upper rolling groove and the lower rolling groove is a roll gap, the upper rolling groove and the lower rolling groove both include a groove bottom section and a groove wall section, the angle between the line connecting the intersection of the groove bottom section and the groove wall section and the center of the groove bottom section and the surface where the roll gap is located is the hole opening angle φ, and the opening angle of the preliminary rolling pass is φ 初 , and 30°≤φ 初 ≤32°, the opening angle of the finishing pass is φ 精 , and φ 精 <30°.

[0024] The beneficial effect of adopting the above further scheme is that the preliminary rolling pass is set to 30° to 32°, which is the ideal pass opening angle obtained based on years of experience. At this angle, the surface quality of the steel pipe and the rolling bite can achieve a relatively ideal balance. The pass opening angle of the finishing pass is set to φ 精 <30°, reducing the lateral flow space of the metal in the rollers, restricting the lateral flow of the steel pipe, increasing the circumferential constrained area of ​​the steel pipe, and effectively improving the lateral uniformity of the steel pipe wall thickness.

[0025] Furthermore, according to the method for processing seamless steel pipes based on an automatic pipe rolling mill according to claim 2, it is characterized in that φ精 ≤10°.

[0026] φ 精 The smaller the angle, the smaller the lateral flow space of the metal during rolling, forcing the metal to flow longitudinally, so the lateral wall thickness is more uniform.

[0027] Furthermore, the surface of the plug is chrome-plated; the plug after chrome-plating has high hardness and high smoothness, and has low friction with the inner wall of the steel pipe during rolling, which can reduce the lateral flow of the metal during rolling, is conducive to the longitudinal flow of the metal, and further improves the uniformity of the wall thickness.

[0028] Furthermore, the plug is a spherical plug; compared with a conical plug, a spherical plug has a longer service life and lower consumption.

[0029] Furthermore, during the process of rolling the steel pipe 1 or 2 times in the initial rolling hole type and 2 times in the finishing rolling hole type (initial rolling and finishing rolling are 3-4 times in total), the cross section of the steel pipe rolled in each time has corresponding hole bottom part, hole wall part (corresponding to the hole opening angle) and roll gap part. In order to make the wall thickness of the steel pipe uniform, from the rolling process of the initial rolling hole type, the rolling process of the finishing rolling hole type, and after the initial rolling of the rough pipe to the finishing rolling hole type, the steel pipe is flipped 90° after the previous rolling, so that the hole bottom part, hole wall part and roll gap part of the previous steel pipe are exchanged in position during the next rolling; in other words, during the rolling 1 or 2 times in the initial rolling hole type, the rolling 2 times in the finishing rolling hole type and the adjacent passes of switching between the above two hole types, the rolled steel pipe needs to be flipped 90° before subsequent rolling; the two rollings can make the roundness and wall thickness accuracy of the steel pipe better, so as to make the previous rolling The metal located at the groove wall during the first rolling will be located at the groove bottom during the next rolling. Since the metal flow space at the groove wall is large and there is a big difference with the designed wall thickness, the steel pipe wall located at the groove wall during a single rolling will be squeezed and flow laterally to "hide" in the groove wall position, making it difficult to obtain a steel pipe with uniform wall thickness. After rotating 90 degrees, the next rolling is performed, forcing the steel pipe wall part that "hides" in the groove wall position during the first rolling to be located at the groove bottom during the next rolling. The squeezed steel pipe at the groove bottom has no flow space in the lateral direction, so the metal material can only be extended longitudinally, so uniform wall thickness can be obtained.

[0030] Furthermore, the plug diameter of the finishing pass is d 精 , the head diameter of the initial rolling hole is d 初 ,and:

[0031] (d 初 +0.2mm)≤d 精 ≤(d 初 +0.5mm);

[0032] The purpose of setting the finishing pass is to obtain steel pipes with more precise dimensions. The plug diameter of the finishing pass is larger than that of the initial rolling pass, which can enable the initial rolled rough pipe to be effectively rolled again in the entire finishing pass, thereby obtaining a steel pipe with uniform wall thickness, avoiding the situation where part of the steel pipe wall cannot be effectively rolled when using the same diameter plug, affecting the quality of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the working principle of an automatic pipe rolling machine in the prior art;

[0034] Figure 2 It is the hole structure diagram;

[0035] Figure 3 is a flow chart of the present invention;

[0036] Figure 4 This is a schematic diagram of the production line layout of Example 1;

[0037] Figure 5 This is a schematic diagram of the production line layout of Example 2;

[0038] Figure 6 This is a schematic diagram of the production line layout of Example 3;

[0039] Figure 7 This is a schematic diagram of the plan to add a salt spray pipe.

[0040] In the accompanying drawings, the component names represented by the reference numerals are listed as follows:

[0041] 11. Working roller; 12. Return roller; 13. Ejector rod; 14. Ejector head; 15. Rough pipe; 151. Primary rough pipe; 16. Front desk; 17. Back desk; 18. Salt spraying pipe; 19. Salt spraying port. DETAILED DESCRIPTION

[0042] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0043] like Figure 3 As shown, a method for processing a seamless steel pipe based on an automatic pipe rolling mill comprises the following steps:

[0044] The hollow rough tube 15 obtained in the previous process is rolled through the initial rolling groove for one or two passes, and then moved into the finishing rolling groove for two passes to obtain a seamless steel tube.

[0045] The hole profile is formed by the rolling groove and the head 14 to form a circular working hole profile, such as Figure 2As shown, the rolling groove includes an upper rolling groove and a lower rolling groove which are distributed up and down and are identical. The joint between the upper rolling groove and the lower rolling groove is a roll gap. The upper rolling groove and the lower rolling groove both include a groove bottom section C and a groove wall section D. The radii of the arcs corresponding to the groove bottom section C and the groove wall section D are different, and the radius R2 of the arc corresponding to the groove wall section D is greater than the radius R1 of the arc corresponding to the groove bottom section C. The angle between the line connecting the intersection of the groove bottom section C and the groove wall section D and the center of the circle corresponding to the groove bottom section arc and the surface where the roll gap is located is called the hole opening angle φ.

[0046] The opening angle of the initial rolling pass is φ 初 , and 30°≤φ 初 ≤32°.

[0047] The opening angle of the finishing pass is φ 精 , and φ 精 <30°.

[0048] The plug 14 is a spherical plug 14 with a hard chrome-plated surface to improve the surface finish and hardness of the spherical plug 14, reduce the friction between the plug 14 and the inner wall of the rough tube 15, thereby reducing the lateral flow of metal on the inner wall of the steel tube caused by friction, increasing the longitudinal flow extension of the metal during rolling, and improving product quality.

[0049] For the same specification of steel pipe, the diameter d of the plug 14 corresponding to the finishing pass is 精 Larger than the initial rolling hole corresponding to the head 14 diameter d 初 20 silk, i.e. d 精 =d 初 +0.2mm, more precise hole shape to obtain more precise wall thickness.

[0050] Furthermore, if Figure 7As shown, a salt spraying pipe 18 is provided on the front desk 16. The salt spraying pipe 18 sprays granular industrial salt into the capillary tube based on compressed air. The capillary tube melts into a molten state when it contacts the high temperature. The molten state at high temperature plays a role in lubricating the plug and the tube wall. Since the length of the rough tube is generally about 10 meters, simply spraying salt on the tube head has limited lubrication effect. Therefore, when the rough tube just arrives at the front desk, the compressed air pressure is adjusted from high to low to change the throwing distance of the blown granular industrial salt. For example, initially 0.5Mpa pressure of compressed air is used to spray salt, and then the pressure is gradually reduced to 0.02Mpa (the pressure can be set to 0Mpa). At the maximum pressure, it is enough to spray the industrial salt to 10 meters away, covering the entire length of the rough tube. At 0.02Mpa, the spraying distance of the granular salt is about 0 to 0.1 meters, thereby achieving the effect of salting the entire length of the inside of the rough tube, and with the help of the rolling of the rough tube on the front desk, the molten industrial salt is spread all over the inner wall of the rough tube, so that the industrial salt can play a role in the subsequent rolling process, reduce the friction between the head and the inner cavity of the steel pipe, reduce the lateral flow of metal in the thickness of the steel pipe wall, and improve product quality.

[0051] Production line layout example 1:

[0052] like Figure 4 As shown, the automatic tube rolling unit of this production line includes a front desk 16, an automatic tube rolling machine equipped with a double-groove roller and a return roller 12, and a back desk 17 adapted to two slots. One of the slot holes of the double-groove roller is a preliminary rolling hole type, and the other slot hole is a finishing rolling hole type. The front desk 16 can only meet the use of a single slot, and the front desk 16 can switch positions to adapt to the specific hole type of the double-groove roller.

[0053] The rolling process of the steel pipe is: each time the steel pipe is rolled from the front stage 16 to the back stage 17 by the rolling rollers, and then transported back to the front stage 16 from the back stage 17 to prepare for the next rolling.

[0054] In this production line, the rough tube 15 is rolled 1 or 2 times in the "initial rolling hole" to obtain the initial rolled rough tube, and returns to the front desk 16. The front desk 16 moves horizontally to the "finishing rolling hole" position with the initial rolled rough tube, flips 90 degrees, and then rolls at least 2 times in the "finishing rolling hole" again to obtain the finished rolled rough tube with uniform wall thickness. The finished rolled rough tube leaves the front desk 16 and enters the next process. The front desk 16 is reset to receive the next rough tube 15.

[0055] Relatively speaking, the equipment of this production line is relatively simple. The disadvantage is that there is only one front desk 16. The working rhythm of the whole production line is limited by the movement of the front desk 16, because it is necessary to wait for the rough pipe of fine rolling to completely leave the front desk 16 before the front desk 16 can return to the initial rolling hole position to prepare to receive the next rough pipe 15. Therefore, the production capacity is relatively low.

[0056] Production line layout example 2:

[0057] like Figure 5 As shown, the automatic tube rolling unit of this production line includes a front desk 16 that can meet the simultaneous operation of two pass types, an automatic tube rolling machine equipped with double-groove rollers and a return roller, and a back desk 17 adapted to two notches. One of the slots of the double-groove roller is a preliminary rolling pass type, and the other slot is a finishing rolling pass type. The front desk 16 can meet the use of double slots without the need for position switching and movement.

[0058] After the rough tube 15 is rolled 1 or 2 times in the "rough rolling pass", the rough tube is moved to the position corresponding to the finishing pass on the foreground 16 and turned 90 degrees. The finishing pass rolls the rough tube once to the backstage 17 and waits. At this time, the rough tube 15 continues to be rolled by the rough rolling pass and the next rough tube is rolled to the backstage 17. At this time, the backstage 17 has two rough tubes at the same time (one is located at the corresponding position of the rough rolling pass, and the other is located at the corresponding position of the finishing pass), and the upper work is started at the same time Roller 11 and lower return roller 12 are lifted up, and the two steel pipes are simultaneously returned to the corresponding front desk 16, and the steel pipes are rolled again through the initial rolling hole and the finishing rolling hole in turn, so as to obtain a finished rough pipe with uniform wall thickness at the "finishing rolling hole" position, and an initial rolled rough pipe is obtained at the "initial rolling hole" position, and the two steel pipes are simultaneously sent back to the front desk 16 again, and the finished rough pipe obtained leaves the front desk 16 and enters the next process, and the initial rolled rough pipe obtained is transferred to the finishing hole position, and the initial rolling hole position receives the next rough pipe again, and so on.

[0059] In this production line, the return program can return two steel pipes at the same time, which saves the return time compared to returning one by one. Therefore, the waiting time is shorter and the processing efficiency is higher than that of Example 1.

[0060] Production line layout example 3:

[0061] like Figure 6 As shown, in this embodiment, two parallel automatic tube rolling mills and return rollers are used. The two parallel tube rolling mills and return rollers mentioned here can be multi-slot or single-slot. Two single-slot automatic tube rolling mills and return rollers are preferred, that is, two independent automatic tube rolling mills and return rollers are arranged in parallel, one of which is equipped with an initial rolling hole type, and the other is equipped with a finishing hole type. The rough tube 15 is rolled 1 or 2 times in the "initial rolling hole type" of the first automatic tube rolling mill to obtain an initial rolled rough tube. The initial rolled rough tube is moved horizontally to the second automatic tube rolling mill, and after 2 times of rolling through the "finishing rolling hole type" of the second automatic tube rolling mill, a finishing rough tube with uniform wall thickness is obtained. The finishing rough tube leaves the front desk 16 and enters the next process.

[0062] In this embodiment, since there are two completely independent automatic tube rolling mills and return rollers, the corresponding rollers, return rollers, front desk 16 and back desk 17 do not interfere with each other, and there is no need to wait. The processing efficiency is the highest, but the equipment investment cost is also the highest.

[0063] The specific arrangement of the two automatic tube rolling mills and the return rollers in the factory can be arranged side by side, or arranged one after the other, or staggered. The above implementation is for illustration only and can be flexibly configured based on the existing production line layout of the factory, which is not exhaustive here. Specific embodiment 4:

[0065] A certain company has a simple automatic tube rolling unit production line with an actual annual production capacity of about 100,000 tons. The specifications are steel tubes with diameters of 108 to 168 mm and wall thicknesses of 4 to 20 mm. It mainly produces thin-walled tubes (more than 70%). In order to obtain steel tubes with wall thickness standards, the automatic tube rolling machine needs to perform three rolling passes when rolling thin-walled tubes. Even so, the uniformity of the wall thickness of the thin-walled tubes is still not ideal, and the yield rate of thin-walled tubes is about 87%, which seriously affects the company's operations. Medium and thick-walled tubes have a large absolute value of wall thickness tolerance and are easy to meet the standard wall thickness tolerance requirements. They only need to be rolled twice, with a yield rate of 92%.

[0066] Based on the above technical solution, the production line is transformed, a multi-slot automatic tube rolling mill is transformed into a single-slot automatic tube rolling mill, and a single-slot automatic tube rolling mill is newly installed, forming a production line of two parallel automatic tube rolling mills similar to that in Example 3. The hole type of the first automatic tube rolling mill is the initial rolling hole type (φ 初 =30°) round hole type, the hole type of the second automatic tube rolling mill is the finishing hole type (φ 精 =0°) round hole type; the top head 14 adopts a spherical top head 14 with a chrome-plated surface, with a total investment of 4 million yuan:

[0067] 1. Rolling process: The rough tube 15 is rolled twice at the hole type "initial rolling hole type" of the first automatic tube rolling mill to obtain the initial rolled rough tube, which is then moved horizontally to the "finishing rolling hole type" position of the second automatic tube rolling mill and rolled twice at the "finishing rolling hole type"; then the finished rolled rough tube leaves the front stage 16 and enters the next process;

[0068] 2. Improvement effect:

[0069] 1) Yield rate: The problem of uneven wall thickness has been greatly improved, and the yield rate of thin-walled steel pipes has increased from 87% before the transformation to more than 92%;

[0070] 2) Annual production capacity: the number of thin-walled tube rolling passes on an automatic tube rolling mill has been reduced from 3 to 2, which has improved the rolling rhythm and increased the annual output from 100,000 tons to 150,000 tons, of which 70% are thin-walled tubes;

[0071] 3) Annual benefits:

[0072] a. According to the fact that every one percentage point increase in the yield rate can increase the profit by 40 yuan / ton, the actual yield rate increases by 5 points: 5*40=200 yuan / ton. According to the designed annual output of 150,000 tons and 70% thin-walled tube production capacity: 15*70% 10,000 tons of benefits are: 15*70%*200=21 million yuan,

[0073] b. Adding a single-slot automatic tube rolling mill will increase the process cost by 40 yuan / ton (only two automatic tube rolling mills are used to produce thin-walled tubes for a total of 4 passes, and one automatic tube rolling mill (initial rolling pass) is still used for the production of medium and thick-walled tubes for 2 passes), then the annual increase in cost is: 40*15*70%=4.2 million yuan,

[0074] c. Annual output increases by 50,000 tons, diluting fixed costs: annual output is 100,000 tons, original price is 100 yuan / ton, total fixed cost is 10 million yuan; after transformation, fixed cost remains unchanged at 10 million yuan, annual output is 150,000 tons, then unit fixed cost is 1000 / 15=66.7 yuan / ton, reduced by 33.3 yuan / ton, annual benefit: 33.3*15=4.995 million yuan;

[0075] d. The additional output (sales) of 50,000 tons, with a profit of 100 yuan / ton, is: 5*100=5 million yuan;

[0076] In summary, the annual efficiency increase of the production line after the transformation compared with the production line before the transformation is: 2100-420+499.5+500=26.795 million yuan

[0077] 3) Payback period:

[0078] The payback period is: 400 / (2679.5 / 12)=400 / 223.3=1.79 months, with significant benefits.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for processing seamless steel pipes based on an automatic pipe rolling mill, characterized in that: The automatic tube rolling machine includes an initial rolling hole and a finishing rolling hole. The ovality of the finishing rolling hole is smaller than that of the initial rolling hole. The hollow rough tube obtained by the previous process is rolled 1 or 2 times by the initial rolling hole to obtain an initial rolling rough tube. The initial rolling rough tube is moved into the finishing rolling hole and rolled twice to obtain a finishing rough tube. The initial rolling hole and the finishing rolling hole are both formed into an annular working hole by the cooperation of a rolling groove and a mandrel. The rolling groove includes an upper rolling groove and a lower rolling groove that are distributed up and down and are the same. The joint between the upper rolling groove and the lower rolling groove is a roller gap. The upper rolling groove and the lower rolling groove both include a groove bottom section and a groove wall section. The angle between the line connecting the intersection of the groove bottom section and the groove wall section and the center of the groove bottom section and the surface where the roller gap is located is the hole opening angle φ. The opening angle of the initial rolling hole is φ 初 , and 30°≤φ 初 ≤32°, the opening angle of the finishing pass is φ 精 , and φ 精 <30°.

2. The method for processing seamless steel pipes based on an automatic pipe rolling mill according to claim 1, characterized in that: f 精 ≤10°。 3. The method for processing seamless steel pipes based on an automatic pipe rolling mill according to any one of claims 1 to 2, characterized in that: The surface of the top head is chrome-plated.

4. The method for processing seamless steel pipes based on an automatic pipe rolling mill according to claim 3, characterized in that: The top head is a spherical top head.

5. The method for processing seamless steel pipes based on an automatic pipe rolling mill according to claim 1, characterized in that: During the entire rolling process of the steel pipe including 1 or 2 passes of preliminary rolling and 2 passes of finishing rolling, the steel pipe needs to be turned 90° after the previous rolling and then rolled for the next rolling.

6. The method for processing seamless steel pipes based on an automatic pipe rolling mill according to claim 5, characterized in that: The top diameter of the finishing pass is d 精 The head diameter of the initial rolling hole is d 初 ,and: (d 初 +0.2mm)≤d 精 ≤(d 初 +0.5mm)。 7. A seamless steel pipe processing production line for implementing the seamless steel pipe processing method based on an automatic pipe rolling mill as described in any one of claims 1 to 6, characterized in that: It includes two automatic tube rolling mills, each of which has its own rollers, return rollers, front and back ends. One of the automatic tube rolling mills is equipped with a preliminary rolling hole profile, and the other is equipped with a finishing rolling hole profile. The rough tube to be processed is rolled successively by the tube rolling mill equipped with the preliminary rolling hole profile and the tube rolling mill equipped with the finishing rolling hole profile.

8. The processing line according to claim 7, characterized in that: The automatic tube rolling machine with the preliminary rolling hole type is placed side by side with the automatic tube rolling machine with the finishing rolling hole type, and a tube feeding machine is arranged between the two. The tube feeding machine is used to transfer the steel tube on the front stage of the automatic tube rolling machine with the preliminary rolling hole type to the front stage of the automatic tube rolling machine with the finishing rolling hole type.

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