A method for improving the wall thickness accuracy of the head and tail of obliquely rolled steel pipe

Abstract

The present invention relates to a tube rolling process, and specifically discloses a method for improving the wall thickness accuracy of the head and tail of a steel tube during oblique rolling, wherein the oblique rolling is based on a hole pattern formed by the cooperation of an outer tool and an inner tool to achieve rolling of a seamless steel tube, and is characterized in that a mechanism for stabilizing the inner tool is provided, wherein the mechanism for stabilizing the inner tool is used to provide support force to the inner tool when the inner tool just starts to contact the rolled billet and before the billet metal fills the hole pattern, and before the inner tool completely separates from the rolled billet, thereby reducing or eliminating the cantilever effect of the inner tool. This method solves the problem of unstable rolling process of the head and tail during tube rolling, greatly reduces the size of the head and tail cuts, improves the yield rate, and reduces production costs.

Description

Technical Field

[0001] The present invention relates to a skew rolling machine in the field of hot-rolled seamless steel pipes, and specifically to a method for improving the wall thickness accuracy of the head and tail of the skew-rolled steel pipe. Background Art

[0002] The main production units and process flow of seamless steel pipes at present:

[0003] 1) Continuous tube rolling mill: heated tube blank --- piercing machine --- continuous tube rolling mill --- sizing mill (or micro-tension reducing mill) --- cooling (finishing);

[0004] 2) Oblique tube rolling unit: heated tube blank --- piercing machine --- tube rolling machine --- sizing machine (or micro-tension reducing machine) --- cooling (finishing);

[0005] 3) Secondary piercing unit: heated tube blank --- piercing machine --- secondary piercing machine --- leveling machine --- sizing machine (or micro-tension reducing machine) --- cooling (finishing);

[0006] 4) Pipe expansion unit:

[0007] a. Heated tube blank --- piercing machine --- rotary expansion machine --- leveling machine --- sizing machine (or micro-tension reducing machine) --- cooling (finishing);

[0008] b. Heated finished pipe --- rotary expansion machine --- homogenizer --- sizing machine (or micro-tension reducing machine) --- cooling (finishing);

[0009] 5) Automatic tube rolling unit: heated tube blank --- piercing machine --- automatic tube rolling machine --- leveling machine --- sizing machine (or micro-tension reducing machine) --- cooling (finishing);

[0010] The piercing machines (two-roll type), tube rolling machines (two-roll type), secondary piercing machines (two-roll type), leveling machines (two-roll type), and rotary expanding machines (two-roll type) in the above-mentioned production lines are actually two-roll oblique rolling mills. They are just placed in different processes based on different specific uses, so they have different names.

[0011] Figure 1 The figure shows a punching machine, which punches the heated solid tube into a hollow rough tube;

[0012] Figure 2 The diagram shows a tube rolling mill, which reduces the wall, reduces the diameter or slightly expands the diameter of the hollow rough tube from the piercing machine and rolls it into a rough tube;

[0013] Figure 3 The diagram shows a secondary perforator, which reduces the wall and expands the diameter of the hollow rough tube from the perforator to make a rough tube;

[0014] Figure 4 The diagram shows a rotary expansion machine, which reduces the wall thickness and expands the diameter of the thinner hollow rough tube (or the heated finished steel tube 55) from the perforator into a large-diameter rough tube;

[0015] Figure 5 The diagram shows a leveling machine, which levels the wall thickness of the rough pipe from the secondary piercing machine, rotary expansion machine or automatic pipe rolling machine to obtain a leveled rough pipe with high wall thickness accuracy;

[0016] From the perspective of the processed incoming materials, the blank 44 of the punching machine is a solid round blank, while the incoming materials of other rolling mills are all hollow tube blanks. In the industry, the tube body coming out of the punching machine is generally called a rough tube, the tube body in the intermediate state processed by other units is called a rough tube, and the final finished tube body is called a finished steel tube. In the present invention, in order to simplify the description, the tube body (i.e., rough tube or rough tube) after rolling by the unit is collectively referred to as a steel tube 55.

[0017] The working principle of the oblique rolling mill is:

[0018] First, the specific hole type is formed by the outer tool and the inner tool, such as Figures 1 to 5 As shown, the outer tool is formed by two rolling mill rollers 11 and two conventional guide plates 22 together to form an elliptical closed hole; the inner tool refers to the plug or core rod 33, and the inner tool is placed at the center of the hole. The inner and outer tools form an annular elliptical hole.

[0019] The mandrel or core rod 33 is supported on the mandrel or support rod 66; the other end of the mandrel or support rod 66 is connected to the trolley 661, and multiple centering rollers 77 are distributed along the length direction of the mandrel or support rod 66 to hold the mandrel or support rod 66 to prevent the mandrel or support rod 66 from radially jumping.

[0020] During the rolling process of steel pipe 55, the positions of the inner and outer tools that make up the hole are relatively static (the rotation of each component along its own axis is not taken into account). After the incoming material is bitten into the hole, it is squeezed and dragged into the hole under the rotation of the active roller, and is constrained by the inner and outer tools to achieve extension deformation, which roughly includes three stages: the unstable process of the first rolling, the stable rolling process and the unstable process of the tail rolling.

[0021] The unstable process of head rolling refers to the process from the head of the billet 44 starting to enter the pass to the process of filling the pass; that is, the head of the heated billet 44 is bitten by the active roller at the entrance of the pass, and enters the closed pass composed of the roller and the conventional guide plate 22. The billet 44 is pierced by the head to form a hollow billet, and the hollow billet is rounded by the roller and the head to obtain a steel pipe 55. At this time, the pass is filled with the deformed billet 44 metal;

[0022] The stable rolling process refers to the continuous rolling process after the hole is filled, that is, the steel pipe 55 is continuously rolled out from the hole outlet. When the front end of the steel pipe 55 approaches the first centering roller 77, the first centering roller 77 changes from holding the top rod or support rod 66 to holding the steel pipe 55, commonly known as a small opening; the steel pipe 55 continues to move forward and encounters the second centering roller 77. The second centering roller 77 opens slightly and changes from holding the top rod or support rod 66 to holding the steel pipe 55, and so on.

[0023] The tail rolling unstable process refers to the rolling process from the tail end of the billet 44 entering the hole entrance until the billet 44 leaves the hole exit (i.e., the rolling is finished); the steel pipe 55 continues to move forward, and the centering rollers 77 are opened slightly in sequence, that is, they are turned from holding the top rod or support rod 66 to holding the steel pipe 55 in sequence. When the rolling is finished, all the centering rollers 77 are fully opened, the mandrel 33 and the top rod or support rod 66 are to be pulled out from the inner cavity of the steel pipe 55, and the steel pipe 55 is pulled away from the rolling line to enter the next process;

[0024] Then, the mandrel 33 and the ejector rod or support rod 66 are reset, and the centering roller 77 is reset to hold the ejector rod or support rod 66, preparing for the rolling of the next steel pipe 55.

[0025] In the above two unstable rolling processes:

[0026] The main problem of unstable head rolling process is the long distance of inner tool cantilever:

[0027] As can be seen from the figure, there is a certain cantilever distance between the plug or mandrel 33 and the first centering roller 77. Practice has proved that when the plug or mandrel 33 contacts the front end of the blank 44 (at this time, the plug or mandrel 33 is in a cantilever state, and the hole is empty), due to the effect of axial pressure, the plug or mandrel 33 and the push rod or support rod 66 will be elastically swung and deviated, that is, they cannot be immediately aligned with the center position of the front end of the blank 44, and the larger the cantilever distance, the greater the elastic deviation during contact, resulting in greater wall thickness deviation at the head of the steel pipe 55, and a greater length of the cut head of the steel pipe 55, which directly affects the yield rate; therefore, it is hoped that the first centering roller 77 is as close to the plug or mandrel 33 as possible; however, the position of the centering roller 77 is restricted by the on-site space:

[0028] If the main transmission shaft of the roller is in the direction of the exit platform, the space between the two transmission shafts at the exit of the pass is small, and the first centering roller 77 cannot be placed, so it has to be placed farther away from the exit of the pass;

[0029] If the main transmission shaft of the roll is in the direction of the hole entrance platform, the replacement of the conventional guide plate 22, shunting, hole measurement, etc. at the hole exit also require a certain amount of operating space. Therefore, it is required that the first centering roller 77 and the hole exit leave an operating distance of at least 1m for manual operation. In addition, the size of the roll bearing box and the length of the roll body ( Figure 1--5 shows that the tool extends through the roller throat), so in practice the distance from the first centering roller 77 to the mandrel is greater than 1.5m.

[0030] In order to reduce the cantilever distance, the first centering roller 77 is placed as close to the hole exit as possible. There is an attempt in the industry: when the main drive shaft of the roller is located in the direction of the hole entrance, the first centering roller 77 of the mill exit table is changed to a movable type, that is, when shunting, the first centering roller 77 is moved a certain distance away, and when producing, the first centering roller 77 is pushed to the hole exit to reduce the cantilever distance. In theory, this can indeed reduce the cantilever distance, but due to the poor conditions at the hole exit: there is cooling water, iron oxide, and shunting, replacement of guide plates, and specification changes are frequent, the movable slideway of the first centering roller 77 is easily worn, affecting the centering accuracy, and the centering roller 77 is difficult to stabilize during production, so this solution is not effective, but when the main drive shaft is located in the exit direction, this movable centering roller solution cannot be implemented;

[0031] The problem of unstable tail rolling process is mainly the swing problem of the plug or mandrel 33 and the push rod or support rod 66:

[0032] When the mandrel 33 gradually emerges from the rear end face of the blank 44, due to the oval hole shape, there is a large space in the direction of the guide plate. At this time, the length of the steel pipe 55 on the exit table is close to the required maximum length, and the centering rollers 77 are basically in a state of holding the steel pipe 55, and there is a large gap between the mandrel or support rod 66 and the inner cavity of the steel pipe 55. The other end of the mandrel or support rod 66 is connected to the trolley 661, and the trolley 661 bears the axial pressure transmitted by the mandrel or support rod 66, that is, the mandrel 33 and the mandrel or support rod 66 are in a state of being close to the required maximum length. Until the trolley 661 is in the "super-long cantilever" state, as more and more metal is exposed from the plug or mandrel 33, the space in the direction of the guide plate becomes larger and larger, and the fluctuation or swing amplitude of the plug or mandrel 33 becomes larger and larger, which leads to the worsening wall thickness accuracy of the tail part of the steel pipe 55, and finally leads to the longer and longer tail cutting length. In reality, the tail cutting length is at least 200-300mm. Every additional 100-200mm cut will affect the yield rate by 0.8-1.6%, and the cost will increase by 40-80 yuan / ton.

[0033] In summary, the above-mentioned two-roller oblique rolling mills experience an "unstable rolling" process during operation, specifically at the beginning and end of rolling. This "unstable rolling" process causes uneven wall thickness at the beginning and end of the rolled steel pipe 55, and a large amount of cutting. Summary of the invention

[0034] The technical problem to be solved by the present invention is how to reduce or eliminate the problem of uneven wall thickness at the head and tail of the obliquely rolled steel pipe.

[0035] The specific technical solution of the present invention to solve the above technical problems is:

[0036] A method for improving the wall thickness accuracy of the head and tail of an obliquely rolled steel pipe, wherein the oblique rolling is based on a hole profile formed by the cooperation of an outer tool and an inner tool to achieve rolling of a seamless steel pipe, and a mechanism for stabilizing the inner tool is provided. The mechanism for stabilizing the inner tool is used to provide support force for the inner tool within a range as small as possible from the inner tool (generally an inlet is between 0 and 1 meter, and an outlet is between 0.5 and 1.5 meters) when the inner tool just starts to contact the rolled billet and before the billet metal fills the hole profile and / or before the inner tool completely leaves the rolled billet, so as to reduce or eliminate the cantilever effect of the inner tool.

[0037] The mechanism for stabilizing the inner tool includes a head stabilizing mechanism and a tail stabilizing mechanism. The head stabilizing mechanism is used to provide supporting force to the inner tool when the inner tool just starts to contact the rolled billet and before the billet metal fills the hole mold; the tail stabilizing mechanism is used to provide supporting force to the inner tool before the inner tool completely separates from the rolled billet.

[0038] In the present invention, the outer tool refers to the components such as the roller, guide plate, guide disk, etc. that are surrounded to form an elliptical hole shape, and the inner tool refers to the components such as the head and mandrel that are arranged in the middle of the hole shape and cooperate with the outer tool to form a ring-shaped hole shape. Compared with the prior art, this scheme has the following technical effects: by setting a mechanism to stabilize the inner tool, when the inner tool just starts to contact the rolled billet to before the billet metal fills the hole shape and / or before the inner tool completely separates from the rolled billet, the inner tool is supported within a range as small as possible from the inner tool to reduce its cantilever distance, thereby reducing or even eliminating the cantilever effect of the inner tool, thereby reducing the radial deviation and swing of the inner tool, thereby ensuring the stability of the relative position between the inner tool and the outer tool, greatly weakening the unstable rolling situation, and ensuring the stability of the wall thickness accuracy of the rolled steel pipe.

[0039] Furthermore, the head stabilizing mechanism is a split-type arm, which is arranged on the hole outlet side, and can be specifically installed on the upper machine cover or on the side or lower base or foundation, that is, the installation position is determined according to conditions and needs, and is used to hold the support part of the inner tool before the arrival of the rolled steel pipe to limit the radial runout of the inner tool, but allow the inner tool to rotate around the axis. This method can reduce the cantilever distance, ensure that the inner tool can be stably located at the center of the billet when it first contacts the billet, thereby reducing the uneven wall thickness of the steel pipe head caused by the cantilever effect during the head rolling stage.

[0040] The split-arm can be realized by a variety of structures, such as mutually meshing gears, two parallel racks meshing with the same gear, power cylinders arranged oppositely, etc. The split-arm is best for synchronous movement, and a slight sequence of movements will not have a significant impact, as long as the centers of the two arms in the holding position coincide with the center of the inner tool.

[0041] Furthermore, the split arm includes two arms, each of which is an integrated arm or an articulated arm. The articulated arm can be bent, and the unfolded arm occupies less space. The specific setting of the integrated arm or the articulated arm can be flexibly selected based on the space on site.

[0042] Furthermore, the holding end of the split arm is provided with a rolling body or buckle shoe to match the size of the inner tool support part and reduce the friction between the split arm and the inner tool support part. The split arm does not hold the inner tool itself, but the support part that supports the inner tool. For example, the inner tool can be a plug or a mandrel. If it is a plug, the corresponding support part is called a push rod. If it is a mandrel, the corresponding support part is called a support rod. The split arm holds the push rod or the support rod. Of course, the closer the holding position is to the inner tool itself, the better.

[0043] Furthermore, the tail stabilizing mechanism is a sleeve arranged at the entrance of the hole type, and the inner tool is small at the front end and large at the rear end. When rolling the tube, the front end of the inner tool always sticks out of the tail end of the billet first, and then gradually expands until the entire inner tool is separated from the tail end of the billet. When the front end of the inner tool sticks out from the tail end of the billet, the sleeve follows up in time and covers the front end of the inner tool, limiting the radial runout of the inner tool, but allowing the inner tool to rotate around the axis, playing a role in stabilizing the inner tool. As a result, both ends of the inner tool have support force, avoiding the state of "extra-long cantilever" in traditional processing technology, and greatly reducing the instability of tail rolling.

[0044] Furthermore, the tail stabilizing mechanism is a stabilizing rod arranged at the front end of the inner tool and a centering device arranged in conjunction with the stabilizing rod. The diameter of the stabilizing rod is smaller than the diameter of the inner tool and is coaxial with the inner tool. When rolling a hollow tube (i.e., other machines other than a punching machine), the stabilizing rod will first pass through the tail end of the billet. When the stabilizing rod passes through the tail end of the billet and the inner tool is still in the billet, the centering device arranged on the inlet side holds the stabilizing rod, allowing the stabilizing rod to rotate but not allowing radial runout, thereby achieving the function of stabilizing the inner tool. This avoids the formation of an overlong cantilever after the inner tool protrudes from the tail end of the billet, reduces the radial runout or swing of the inner tool during tail rolling, and ensures the uniformity of the wall thickness of the tail of the steel pipe.

[0045] Furthermore, the centering device is a three-roller centering roller or a split-type arm.

[0046] Furthermore, a small plug is provided at the end of the stabilizer bar. After the small plug is provided, it can be applied to the punching machine, the original internal tool is a large plug, a stabilizer bar is provided at the front end of the original large plug, a small plug is provided at the front end of the stabilizer bar, and a split-type arm is provided at a position adapted to the stabilizer bar. When punching a solid tube billet, the small plug first protrudes from the tail end of the tube billet, and after the stabilizer bar part is also exposed, the split-type arm holds the stabilizer bar, and the large plug continues to be rolled in the billet until the rolling is completed, thereby avoiding the overlong cantilever formed after the large plug protrudes from the tube billet, and ensuring the uniformity of the wall thickness of the tail of the rolled steel pipe.

[0047] Furthermore, the stabilizing rod is telescopically arranged in the inner tool, and can be extended when needed and retracted when not needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic diagram of a punching machine;

[0049] Figure 2 is a schematic diagram of a tube rolling mill;

[0050] Figure 3 Schematic diagram of the secondary punching machine.

[0051] Figure 4 It is a schematic diagram of a rotary expander;

[0052] Figure 5 It is a schematic diagram of a leveling machine;

[0053] Figure 6 It is a schematic diagram of the principle of split-type arm;

[0054] Figure 7 This is a schematic diagram of an integrated split-type arm;

[0055] Figure 8 It is a schematic diagram of the articulated split-type arm;

[0056] Fig. 9 Schematic diagram of setting casing on the inlet side;

[0057] Fig.10 A schematic diagram of a stabilizer bar scheme for the front end of the inner tool;

[0058] Fig.11 Schematic diagram of the stabilizer bar scheme for the secondary punching machine;

[0059] Fig.12 Schematic diagram of the stabilizer bar scheme for leveling machine;

[0060] Fig.13 A schematic diagram of the first working state of the solution of setting a small plug at the front end of the stabilizer bar;

[0061] Fig.14A schematic diagram of the second working state of the solution of setting a small head at the front end of the stabilizer bar;

[0062] Fig.15 A schematic diagram of the first state of the scheme for transforming a puncher with a retractable stabilizer bar with a small plug;

[0063] Fig.16 Schematic diagram of the second state of the punching machine modification with a small-head retractable stabilizer bar.

[0064] In the accompanying drawings, the component names represented by the reference numerals are listed as follows:

[0065] 11. Rolling mill rolls; 111. Small diameter rolls; 112. Large diameter rolls; 22. Conventional guide plates; 221. Small guide plates; 222. Large guide plates; 33. Mandrel or core rod; 330. Sleeve; 331. Stabilizing rod; 332. Small mandrel; 333. Large mandrel; 334. Connecting rod; 335. Front mandrel; 336. Rear mandrel; 44. Billet; 55. Steel pipe; 66. Mandrel or support rod; 661. Trolley; 77. Centering roller; 88. Memorial arch; 99. Split arm; 991. Integrated arm; 992. Articulated arm; 101. Centering device; 102. Upper cover. DETAILED DESCRIPTION

[0066] 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.

[0067] A method for improving the wall thickness accuracy of the head and tail of an obliquely rolled steel tube 55, wherein the oblique rolling is based on a hole profile formed by the cooperation of an outer tool and an inner tool to achieve rolling of the seamless steel tube 55, and a mechanism for stabilizing the inner tool is provided. The mechanism for stabilizing the inner tool is used to provide support force to the inner tool from the time when the inner tool just starts to contact the rolled billet 44 to before the metal of the billet 44 fills the hole profile, and before the inner tool completely separates from the rolled billet 44, thereby reducing or eliminating the cantilever effect of the inner tool.

[0068] Example 1, split arm 99 scheme

[0069] The solution to the unstable process of the first rolling in this example is the split arm 99 method. The following is an example of a specific unit, but it is not limited to the following specific units. All oblique rolling units can be applied to the example:

[0070] When the rolling mill rolls 11 are arranged left and right, a split-type arm 99 (such as a clamp-type arm) is installed on the archway 88 at the hole exit. Figure 6As shown, it comprises two arms, and the distance between the arms and the mandrel or core rod 33 is very short, which can generally be controlled within the range of 0.5-1.5 meters, that is, the cantilever distance is very short, and the arms can hold the mandrel or support rod 66 when they are closed. When the steel pipe 55 rolled out of the pass reaches the arms, the pass will be filled with the deformed blank 44 metal, and the cantilever situation of the mandrel or core rod 33 disappears. At this time, the arms are opened in time to avoid blocking the continued rolling of the rolled steel pipe 55, thereby completing the mission of reducing the unstable process of the head rolling during this rolling process;

[0071] like Figure 7 As shown, a single arm of the split arm 99 can be an integrated arm 991. This form has a simple structure and is easy to make, but requires a larger space during the operation. It is suitable for the situation where there is no main transmission at the hole outlet and there is enough space for swinging the arm. There are many existing technologies that can realize synchronous arm movement, such as setting mutually meshing gears at the driving end, meshing the same gear between two parallel racks, and synchronous control of two hydraulic cylinders with displacement sensors. The gear rack system uses various power systems such as motors and hydraulic cylinders to drive one of the gears to rotate. Due to the mutual meshing of gears, the two arms can move synchronously, so the specific synchronization form and drive form are not limited, as long as they can meet the synchronous holding and separation actions.

[0072] Figure 8 The figure shows an articulated boom 992, in which a single boom is divided into two sections, the driving side is a boom, and the other end of the boom is hinged with a forearm, and the hinge point is set at the inner side end of the boom and the forearm. When the boom is swung up, the forearm can be driven up, but because the forearm and the boom are hinged, the forearm is in a drooping state when it is lifted up, so that the lateral distance occupies less space, which is suitable for the situation where there is a main transmission shaft and a narrow space at the hole outlet; when the boom is swung down to the right position, the forearm swings along with it, and because the hinge point is located at the inner side end of the boom and the forearm, when the vertical line where the center of gravity of the forearm is located passes through the hinge point, the hinge ends of the boom and the forearm abut against each other near the outer part, and the continued rotation of the boom will completely drive the forearm to rotate, thereby allowing the forearm to swing to the holding position of the top holding rod or the support rod 66, and at this time, the two closed forearms cannot move;

[0073] It should be noted that:

[0074] Since the roller and its main transmission shaft may be arranged left and right, or may be arranged up and down, the above embodiment is based on the premise that the roller and its main transmission shaft are arranged left and right. When the roller and its main transmission shaft are arranged up and down, the split arm 99 needs to be installed on both sides of the hole outlet, and the principle of its top holding rod or support rod 66 remains unchanged, but considering the space allowed at this time, the arm holding action can be other forms of arm holding, such as clamp arm holding, translation opening and closing arm holding, etc. Based on the existing mechanical and electrical industrial control technology, any technology that can realize the synchronous opening and closing of the two arms can be used;

[0075] A better solution for the split-type arm 99 in the present invention is "synchronous split-type arm". Synchronous means that the two arms move synchronously to avoid the situation where one side moves first when the positioning accuracy of the arms is poor, resulting in a center offset to the top rod or the support rod when holding. Of course, if the holding position control accuracy of the two arms is sufficient, it is sufficient to ensure that the holding position is concentric with the inner tool.

[0076] Furthermore, at the contact point between the two arms and the top rod or support rod 66, two rollers may be installed on each arm, that is, the top rod or support rod 66 is always held tightly by four rollers to reduce friction during the working process;

[0077] Alternatively, it is also possible to consider installing a semicircular buckle tile on each arm to hold the top rod or support rod 66 through the buckle tile. Because the buckle tile of the arm is held tightly for a limited time, it will not wear too quickly, thereby reducing the wear on the arm.

[0078] Embodiment 2, sleeve 330 scheme

[0079] like Fig. 9 As shown, in this example, the "sleeve 330" solution for the unstable process of tail rolling is explained by taking the piercing machine as an example, but it is not limited to the piercing machine:

[0080] When the plug or mandrel 33 gradually emerges from the end of the blank 44, the pipe rolling is nearing the end. When the exposed portion of the plug or mandrel 33 reaches a certain size, the sleeve 330 arranged at the entrance of the pass quickly moves forward to cover the front part of the exposed plug or mandrel 33. The sleeve 330 can be supported by a clamping seat at the entrance of the pass or can be installed on the upper cover 102 of the archway 88 at the entrance of the pass. After the sleeve 330 embraces the plug or mandrel 33, the plug or mandrel 33 is allowed to rotate, but the radial swing of the plug or mandrel 33 is limited, that is, to ensure that its rotation axis is stable and motionless, thereby playing a role in stabilizing the inner tool;

[0081] It should be pointed out that when implementing the sleeve 330 solution, it is necessary to detect the speed of the tail end of the blank 44 and the time for the blank 44 to pass through the plug or core rod 33 to adjust the time for the sleeve 330 to reach the plug or core rod 33. Only accurate and timely can it play a role in stabilizing the inner tool.

[0082] Embodiment 3, Stabilizer bar 331 solution

[0083] This example uses a rotary expansion machine as an example to explain the stabilizer bar 331 scheme. For oblique rolling mills (i.e., except for piercing machines) using hollow billets 44, the stabilizer bar 331 scheme can be used. Fig.10 As shown, a "stabilizing rod 331" is installed on the head of the plug or the core rod 33. The schematic diagram of the scheme of adding a stabilizing rod 331 to the secondary piercing machine is as follows Fig.11 As shown, the schematic diagram of the solution of adding a stabilizer bar 331 to the leveler is as follows Fig.12 As shown, the principle diagram of the scheme of adding a stabilizer bar 331 to the tube rolling mill is the same as Fig.10 , so I won’t repeat it:

[0084] When the steel pipe 55 moves forward and its tail end gradually exposes the part of the "stabilizing rod 331", the centering device 101 at the entrance of the hole type holds the "stabilizing rod 331", allowing it to rotate but not to swing, so as to achieve the effect of stabilizing the internal tool; the centering device 101 can be a three-roller centering roller or a split arm 99 installed at the entrance of the hole type.

[0085] It should be noted that:

[0086] 1) The mandrel is generally of limited motion type. If the length of the mandrel and its limited motion distance allow, the centering device 101 can directly hold the mandrel (without installing the "stabilizing rod 331"), so that it can rotate but cannot swing, thereby achieving the effect of stabilizing the inner tool;

[0087] 2) The "stabilizing rod 331" can be fixed or concealed. The so-called concealed type means that when it is needed, it is extended and held by the centering device 101, and when it is not needed, it is retracted into the inside of the plug or the core rod 33.

[0088] Embodiment 4, the stabilizer bar 331 with a small head 332:

[0089] like Fig.13 As shown, for a piercing machine with solid billet 44 as incoming material, a small plug 332 is installed at the front end of the stabilizer bar 331, thereby improving its rolling process: the original perforation hole type is changed to a one-time perforation hole type + a two-time perforation hole type + an internal split arm 99, such as Fig.13 Please note that Fig.13 Only the piercing machine structure is shown, but other types of oblique rolling mills are also applicable:

[0090] The primary pass is composed of two small-diameter rollers 111, a small guide plate 221, and a small top 332; the secondary pass is composed of two large-diameter rollers 112, a large guide plate 222, and a large top 333. The connecting rod 334 between the large top 333 and the small top 332 is equivalent to the aforementioned stabilizing rod 331; the internal split arm 99 is installed between the aforementioned primary pass and secondary pass.

[0091] like Fig.14 As shown, when the tail end face of the blank 44 leaves the small plug 332 and the connecting rod 334, the split arm 99 in the machine holds the connecting rod 334, and the blank 44 continues to move forward to the secondary pass for rolling. At this time, the small plug 332 and the large plug 333 can only rotate but cannot swing, thus playing a role in stabilizing the internal tool until the rolling is completed;

[0092] It should be noted that:

[0093] 1) The small roller and the large roller can be coaxial or not;

[0094] 2) The working principle of the split arm 99 is the same as above, but the installation position is different;

[0095] Example 5 Application of small plug 332 + telescopic stabilizer bar 331 solution in punching machine

[0096] like Fig.15 As shown, this example is still applied to a punching machine, and the conventional plug is divided into a front plug 335 and a rear plug 336. The front plug 335 is arranged on the stabilizing rod 331, and the stabilizing rod 331 is telescopically arranged in the rear plug 336. In other words, the front plug 335 is equivalent to the small plug 332 in Example 4, and the rear plug 336 is equivalent to the large plug 333 in Example 4. The present solution still arranges the small plug 332 at the end of the stabilizing rod 331, which is different from the embodiment 4. The difference of Example 4 is that in this example, the stabilizer rod 331 body is telescopically arranged in the rear head 336, and the front head 335 is actually the front end of the traditional large head 333. The stabilizer rod 331 can be retracted into the rear head 336 by a spring structure, or can be arranged in the rear head 336 by a hydraulic system. When the telescopic rod is retracted into the rear head 336, the front head 335 and the rear head 336 are abutted together to form the head part in the traditional process (the hole shape state is as shown in FIG. Fig.15 , Fig.16 Indicated), such as Fig.16 As shown, when the front plug 335 protrudes out of the blank 44, under the action of the built-in hydraulic system, the stabilizing rod 331 quickly extends out of the rear plug 336 and extends into the sleeve 330 on the inlet side (the sleeve 330 quickly meets the protruding front plug 335 and covers part of the front plug 335), allowing the front plug 335 to rotate around the axis but limiting the radial runout of the front plug 335, thereby achieving the purpose of stabilizing the inner tool.

[0097] In this example, there is no need to improve the rolls, nor is there a need to set up an in-machine synchronous split arm, so the modification is simpler. Of course, it is also possible to continue to use the in-machine synchronous split arm in this example. When the front head 335 protrudes out of the blank 44, the front head 335 quickly extends out of the rear head 336 under the push of the hydraulic system. The connecting rod between the front head 335 and the rear head 336 is equivalent to the stabilizing rod 331. The in-machine synchronous split arm can keep the connecting rod in time and can also play a role in stabilizing the internal tool. However, relatively speaking, the modification cost of using the sleeve 330 solution in this example is lower.

[0098] Example 6 Economic Benefit Analysis Example:

[0099] A factory has a 159 secondary perforation unit production line with a production specification of φ159-325x5-20mm and an annual production capacity of 200,000 tons, of which 70% are thin-walled steel pipes 55. Its process flow is as follows: annular furnace (heating solid billet) ---- perforator ---- secondary perforator ---- leveler ---- sizing machine ---- cooling (finishing); the wall thickness of thin-walled steel pipe 55 is seriously uneven at the head and tail, and at least 150mm of the head length and 250mm of the tail length need to be cut off, which seriously affects the yield rate. Therefore, the control measures for the wall thickness accuracy of the head and tail of the steel pipe 55 rolled by the perforator, secondary perforator and leveler are strengthened.

[0100] Reconstruction: Use the method of the present invention to transform the perforator, secondary perforator and leveler:

[0101] 1. The punching machine is transformed according to the scheme in Example 4:

[0102] 1) Adopt the process of the present invention: one-time perforation hole type + two-time perforation hole type + machine internal split arm 99;

[0103] 2) New production:

[0104] a) Make new rolls with smaller or larger diameters, or improve the original rolls if the roll surface length allows;

[0105] b) Newly manufacture small and large piercing heads and guide plates;

[0106] c) Install a split arm 99 at the hole exit, install two semicircular tiles to hold the top rod, the synchronization mechanism uses two gears of the same diameter to mesh, the power is a hydraulic cylinder, and the opening and closing control is realized based on the hot metal detector;

[0107] d) Install split-type arm 99 inside the aircraft, with the same action structure as above;

[0108] 3) Working principle:

[0109] The heated solid billet 44 is bitten into the primary pass by the small roller, and the metal passes through the small head 332 to be made into a hollow billet, which then crosses the connecting rod 334 and continues to move forward.

[0110] The large roll bites into the secondary hole, and the hollow billet is pierced through the large head 333 to form a steel pipe 55.

[0111] At this time, the split arm 99 installed at the hole exit is opened from the top rod state.

[0112] The steel pipe 55 continues to move forward, and when it encounters the first centering roller 77, the first centering roller 77 (small opening) changes from holding the top rod to holding the steel pipe 55, and so on.

[0113] When the tail end of the blank 44 leaves the small mandrel 332 and the connecting rod 334, the split arm 99 in the machine holds the connecting rod 334 until the rolling is finished, then the split arm 99 in the machine opens, all the centering rollers 77 are fully opened, and the small mandrel 332, the connecting rod 334 and the large mandrel 333 are driven by the mandrel to be pulled out of the inner cavity of the steel pipe 55, and the steel pipe 55 is pulled away from the rolling line and enters the next process;

[0114] Then, each one is reset to prepare for the next rolling.

[0115] 2. Secondary punching machine transformation:

[0116] 1) New production:

[0117] a) Install split arm 99 at the hole exit, its two semicircular tiles hold the top rod, the synchronization mechanism uses two gears of the same diameter to mesh, power hydraulic cylinder, infrared metal detector;

[0118] b) Install a stabilizing rod 331 at the nose of the mandrel, install a three-roll centering roller at the entrance of the pass, use a hot metal detector to detect the steel pipe 55, and control the movement of the centering roller 77;

[0119] 2) Working principle:

[0120] The hollow billet 44 from the piercing machine is bitten into the pass by the roller, and the billet 44 passes through the stabilizing rod 331 to reach the top, and is rolled into a steel pipe 55. When the steel pipe 55 reaches the exit of the pass, the split arm 99 opens, and the steel pipe 55 continues to move forward and encounters the first centering roller 77. The centering roller 77 (small opening) changes from holding the top rod to holding the steel pipe 55, and so on.

[0121] When the tail end of the billet 44 leaves the stabilizing rod 331 for a certain distance, the three-roll centering roller at the entrance of the pass embraces the stabilizing rod 331, and when the rolling is finished, all the centering rollers 77 are opened, the three-roll centering rollers are opened, and the top and top rods of the stabilizing rod 331 are pulled out of the inner cavity of the steel pipe 55, and the steel pipe 55 is pulled away from the rolling line and enters the next process;

[0122] Then, each one is reset to prepare for the next rolling;

[0123] 3. Renovation of the entire machine,

[0124] The content is the same as the above-mentioned secondary punching machine modification and will not be repeated here.

[0125] 4. Investment:

[0126] The perforator has an investment of 200,000 yuan: 99 sets of split-type arms and 99 sets of split-type arms are newly made; each set of synchronization mechanism is two identical gears meshing, and the power is a hydraulic cylinder; the detection adopts hot metal probe;

[0127] Other roll tops are tool consumption and directly enter the process cost;

[0128] The secondary puncher and leveler each invested 200,000 yuan, and each newly manufactured split-type arm 99 sets; each set of synchronization mechanism has two identical gears meshing, and the power is a hydraulic cylinder; the detection also uses a hot metal probe;

[0129] Each newly manufactured set of three-roller centering rollers;

[0130] Stabilizing rods are tool consumption and directly enter into process costs;

[0131] 5. Effect after transformation:

[0132] The cutting length of steel pipe 55 is within 100mm, and the cutting length of tail is within 150mm, which increases the yield rate by 1.5% compared with before the transformation. According to the above caliber calculation, the cost is reduced by 75 yuan / ton, and the profit of thin-walled steel pipe 55 is increased by 20*70%*75=10.5 million yuan / year;

[0133] Due to the large and small rollers, jacks, connecting rods 334, and stabilizing rods, the process cost increases by 10 yuan / ton, which means the increased cost is: 20*70%*10=1.4 million yuan;

[0134] The net increase in benefits: 10.5-1.4 = 9.1 million yuan;

[0135] Payback period: 60 / (910 / 12)=60 / 75.8=0.8 months;

[0136] Conclusion: After applying the transformation of the present invention, the benefits are significant.

[0137] 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 improving the wall thickness accuracy of the head and tail of a steel pipe during cross-rolling, wherein the cross-rolling is based on a hole shape formed by the cooperation of an outer tool and an inner tool to achieve rolling of the steel pipe (55), characterized in that: A mechanism for stabilizing the inner tool is provided, the mechanism for stabilizing the inner tool being used to provide a supporting force to the inner tool within a distance of 0-1.5 meters from the inner tool during the period from when the inner tool just contacts the rolled billet (44) to when the billet (44) metal fills the hole and / or before the inner tool completely leaves the rolled billet (44), thereby reducing or eliminating the cantilever effect of the inner tool; the mechanism for stabilizing the inner tool comprises a head stabilizing mechanism and a tail stabilizing mechanism, the head stabilizing mechanism being a split-type arm (99), the split-type arm (99) being provided at the hole outlet side, and being used to provide a supporting force to the inner tool during the period from when the inner tool just contacts the rolled billet (44) to when the billet (44) metal fills the hole; The tail stabilizing mechanism is a sleeve (330) arranged at the entrance of the hole type. The inner tool has a small front end and a large rear end. When the front end of the inner tool protrudes from the blank (44), the sleeve (330) follows up in time and covers the front end of the inner tool, thereby limiting the radial runout of the inner tool but allowing the inner tool to rotate around the axis, thereby stabilizing the inner tool. or A stabilizing rod (331) arranged at the front end of the inner tool and a centering device (101) matched with the stabilizing rod (331) are used to provide support force to the inner tool before the inner tool completely separates from the rolled blank (44).

2. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 1, characterized in that: The head stabilizing mechanism is used to hold the supporting portion of the inner tool before the rolled steel pipe (55) arrives, so as to limit the radial runout of the inner tool and allow the inner tool to rotate around the axis.

3. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 2, characterized in that: The split-type embracing arm (99) comprises two supporting arms, each supporting arm being an integrated embracing arm (991) or an articulated embracing arm (992).

4. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 3 is characterized in that: The holding end of the split holding arm (99) is provided with a rolling body or a buckle shoe to reduce the friction with the inner tool support part.

5. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 4, characterized in that: The diameter of the stabilizing rod (331) is smaller than the diameter of the inner tool and is coaxial with the inner tool. When rolling a tube, the stabilizing rod (331) first passes through the blank (44). When the stabilizing rod (331) passes through the blank (44) and the inner tool is still in the blank (44), a centering device (101) arranged on the entrance side of the hole pattern holds the stabilizing rod (331), allowing the stabilizing rod (331) to rotate but not allowing it to radially run out, thereby achieving the function of stabilizing the inner tool.

6. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 5, characterized in that: The centering device (101) is a three-roller centering roller or a split-type arm (99).

7. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to claim 5, characterized in that: A small pin (332) is provided at the end of the stabilizing rod (331).

8. The method for improving the wall thickness accuracy of the head and tail of the obliquely rolled steel pipe according to any one of claims 5 to 7, characterized in that: The stabilizing rod (331) is telescopically arranged in the inner tool, extending when needed and retracting when not needed.

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