A precision seamless steel tube cold-drawing die lubricating system and control method

Abstract

The application discloses a precision seamless steel pipe cold-drawing die lubricating system and a control method. The lubricating system comprises a die assembly and a hydraulic system. The die assembly comprises a die, an upper die fixing base and a lower die fixing base. The die is a hollow cylindrical boss. A plurality of oil injection holes are formed in the cylindrical surface of the die, and a steel pipe is sleeved in the cylindrical surface. Curve lubricating oil grooves are arranged on the inner walls of the semi-cylindrical cavities of the upper die fixing base and the lower die fixing base, and the curve lubricating oil grooves are communicated with the oil injection holes. Straight lubricating oil grooves are arranged on the connecting surfaces of the upper die fixing base and the lower die fixing base, and the two straight lubricating oil grooves are respectively communicated with the two ends of the curve lubricating oil grooves. One of the straight lubricating oil grooves is provided with an oil inlet connected with an oil tank, and the other straight lubricating oil groove is provided with an oil outlet. After working, the lubricating oil returns to the oil tank. The application can reduce the surface roughness of the drawn steel pipe and the abrasion of the die during the lubricating process.

Description

Technical Field

[0001] This invention relates to the field of precision seamless steel pipe processing technology, specifically to a lubrication system and control method for a precision seamless steel pipe cold drawing die. Background Technology

[0002] Precision seamless steel pipes are precision steel pipes produced through cold rolling or cold drawing. Due to their advantages such as no oxide layer on the inner and outer walls, high pressure resistance without leakage, high precision, high surface finish, and no deformation after cold bending, they are widely used in aerospace, petrochemical, engineering machinery, shipbuilding, and rail transportation, and are known as the "blood vessels of modern industry." Currently, before cold drawing, precision seamless steel pipes generally only undergo surface lubrication treatment of the die using processes such as phosphating and acid treatment. Further lubrication is lacking during the drawing process, and the high heat generated by the die during drawing causes deformation of both the steel pipe and the die, affecting the forming accuracy of the drawn pipe. Insufficient lubrication can also further increase the drawing force, increasing system power consumption and cost. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention provides a lubrication system and control method for a precision seamless steel pipe cold drawing die.

[0004] The technical solution adopted in this invention is as follows:

[0005] In a first aspect, the present invention proposes a lubrication system for a precision seamless steel pipe cold drawing die, used to lubricate the steel pipe during the drawing process of a drawing machine; comprising:

[0006] A mold assembly includes a mold, an upper mold fixing seat, and a lower mold fixing seat. The mold is a hollow cylinder with a connecting flange at the front end. Multiple oil injection holes communicating with the inner cavity are evenly distributed on the cylinder, through which a steel pipe passes. Both the upper and lower mold fixing seats have semi-cylindrical mold cavities, which are detachably connected. The two semi-cylindrical cavities form a cylindrical mold cavity, with the cylinder extending into the cavity and in close contact with the cavity wall. The connecting flange of the mold is detachably connected to the upper and lower mold fixing seats. Curved lubricating oil grooves are provided on the walls of the two semi-cylindrical mold cavities, communicating with the oil injection holes. Straight lubricating oil grooves are provided on the connecting surfaces on the left and right sides of the upper and lower mold fixing seats, respectively, and the two straight lubricating oil grooves are connected to the two ends of the two curved lubricating oil grooves. One straight lubricating oil groove has an oil inlet, and the other has an oil outlet.

[0007] A hydraulic system is used to provide high-pressure oil to the mold; the hydraulic system includes an oil tank, a hydraulic pump, a switching valve (24) and a lubricating oil proportional flow valve; the hydraulic pump is connected to the lubricating oil proportional flow valve via the switching valve; the lubricating oil proportional flow valve is connected to the inlet pipe on a linear lubricating oil groove; the outlet on another linear lubricating oil groove is connected to the oil tank via a pipeline.

[0008] As a further improvement of the present invention, the lubrication system also includes a lubricating oil recovery tank, which is located below the mold assembly. The lubricating oil recovery tank has an oil discharge port, which is connected to the oil tank pipeline.

[0009] As a further improvement of the present invention, the recovery oil tank is provided with a filter screen, which is used to filter the lubricating oil dripping from the mold assembly when lubricating the steel pipe.

[0010] As a further improvement of the present invention, the oil injection hole is circular in shape and has a diameter of 2-3 mm.

[0011] As a further improvement of the present invention, there are 24 oil injection holes, which are arranged in 4 rows on the circumferential direction of the cylindrical surface, and 6 holes are arranged in each row along the axial direction.

[0012] As a further improvement of the present invention, the curved lubricating oil groove is U-shaped.

[0013] As a further improvement of the present invention, the hydraulic system also includes a return oil temperature sensor, which is located on the pipeline between the oil outlet on the linear lubricating oil groove and the oil tank.

[0014] As a further improvement of the present invention, a tapered inlet is provided at the front end of the inner cavity of the mold. The large diameter of the tapered inlet is greater than or equal to the diameter of the steel pipe, and the small diameter is the same as the inner cavity diameter. The tapered inlet is used to reduce the diameter of the steel pipe.

[0015] As a further improvement of the present invention, the lubrication system also includes a pulling carriage located behind the mold assembly for clamping the steel pipe and pulling it backward.

[0016] Secondly, this invention also proposes a lubrication control method for precision seamless steel tube cold drawing dies, comprising the following steps:

[0017] Step S1: Calculate the theoretical control voltage U1 related to speed, U2 related to temperature, and U3 related to diameter reduction ratio of the lubricating oil proportional flow valve according to different process parameters. These are specifically divided into three categories:

[0018] The first category is based on the drawing speed v of the drawing machine, and the maximum drawing speed v of the drawing machine. maxThe maximum control voltage U of the lubricating oil proportional flow valve max Calculate the speed-related theoretical control voltage U1, v max The value range is 0.3m / s-0.4m / s, and the specific formula is as follows:

[0019]

[0020] The second category is based on the oil return temperature error ΔT of the mold components and the maximum oil return temperature error ΔT. max The theoretical control voltage U2 related to temperature error is calculated using the following formula:

[0021]

[0022] In the formula, ΔT=T back -T0, T back T is the return oil temperature of the mold assembly. back The return oil temperature is collected by a return oil temperature sensor. T0 is the desired return oil temperature, and the value of T0 ranges from 20℃ to 30℃. ΔT max For maximum oil return

[0023] Temperature error, ΔT max =T max -T0, T max The maximum return oil temperature threshold is defined as 65℃-75℃; the third category is based on the steel pipe's drawing reduction ratio δ and the maximum drawing reduction ratio δ. max The theoretical control voltage U3 related to the reduction ratio is calculated using the following formula:

[0024]

[0025] In the formula, D is the outer diameter of the steel pipe before drawing, d is the outer diameter of the steel pipe after drawing, and δ max The value range is 0.2-0.3;

[0026] Step S2: Set the control voltage of the lubricating oil proportional flow valve to U = max{U1,U2,U3};

[0027] Step S3: After time t, where t ranges from 30s to 60s, determine the value of T. back ≥T max If the condition is met, stop pulling and issue an oil high temperature alarm to remind the lubricating oil to be cooled. If the condition is not met, repeat steps S1 to S3.

[0028] The beneficial effects of this invention are:

[0029] (1) The seamless steel pipe cold drawing die lubrication system of the present invention can provide lubricating oil during the steel pipe drawing process, reduce the surface friction coefficient between the die and the steel pipe during steel pipe drawing, reduce die wear, and reduce the surface roughness and drawing force of the produced steel pipe;

[0030] (2) The lubrication system of the present invention has a curved lubrication oil groove on the mold cavity of the mold component. The lubricating oil can not only enter the oil injection hole through the curved lubrication oil groove to reach the surface of the steel pipe to lubricate the steel pipe, but also flow on the outer surface of the mold in a specific path, which can reduce the temperature of the mold, reduce the amount of deformation caused by the heat of the mold, and effectively improve the precision of the produced steel pipe.

[0031] (3) The oil injection holes of the mold of the present invention are evenly distributed on the cylindrical surface of the rear end of the mold, which is conducive to the full lubrication of the steel pipe;

[0032] (4) The lubrication control method of the present invention adopts different setting strategies for the control voltage of the lubricating oil proportional flow valve according to the different drawing speed, the magnitude of the return oil temperature error of the mold assembly and the size of the diameter reduction ratio of the steel pipe, which can improve the lubrication and cold drawing effect. Attached Figure Description

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Figure 1 This is a schematic diagram of the overall framework of the mold lubrication device of the present invention;

[0035] Figure 2 This is an isometric view of the mold assembly and lubricating oil recovery box of the present invention;

[0036] Figure 3 This is an exploded view of the mold assembly of the present invention;

[0037] Figure 4 This is a cross-sectional schematic diagram of the mold assembly of the present invention;

[0038] Figure 5 Schematic diagram of the lubrication oil passage of the upper mold fixing seat of the present invention;

[0039] Figure 6 This is a control flowchart of the cold drawing die lubrication system of the present invention;

[0040] In the diagram: 1-Mold assembly; 11-Mold; 110-Oil injection hole; 111-Conical inlet; 12-Upper mold fixing seat; 120-Curved lubricating oil groove; 121-Straight lubricating oil groove; 122-Oil inlet; 123-Oil outlet; 13-Lower mold fixing seat; 2-Hydraulic system; 21-Oil tank; 22-Level sensor; 23-Hydraulic pump; 24-Switch valve; 25-Oil tank temperature sensor; 26-Lubricating oil proportional flow valve; 27-Return oil temperature sensor; 28-Relief valve; 29-Suction filter; 3-Lubricating oil recovery tank; 4-Pulling trolley; 5-Steel pipe. Detailed Implementation

[0041] like Figure 1-5 As shown, a precision seamless steel pipe cold drawing die lubrication system is used to lubricate the steel pipe 5 during the drawing process of the drawing machine.

[0042] The lubrication system includes a mold assembly 1, a hydraulic system 2, a lubricating oil recovery tank 3, and a drawing trolley 4. The lubrication system is also part of the drawing machine. The mold assembly 1 consists of three parts: a mold 11, an upper mold fixing seat 12, and a lower mold fixing seat 13. The mold assembly 1 is used to reduce the diameter of the steel pipe 5, i.e., to reduce the diameter of the steel pipe 5. The mold 11 is a hollow cylindrical boss with a connecting flange at the front end and a cylinder at the rear end. Multiple oil injection holes 110 are evenly distributed on the cylindrical surface of the cylinder, and the oil injection holes 110 communicate with the inner cavity. Specifically, there are 24 oil injection holes 110, arranged in 4 rows circumferentially, with 6 holes arranged axially in each row. Both the upper mold fixing seat 12 and the lower mold fixing seat 13 are provided with semi-cylindrical mold cavities, and the upper mold fixing seat 12 and the lower mold fixing seat 13 are connected by fasteners. Two semi-cylindrical mold cavities form a cylindrical mold cavity. The cylindrical surface of mold 11 extends into the interior of the cylindrical mold cavity and is in close contact with the cavity wall. The connecting flange of mold 11 is connected to the upper mold fixing seat 12 and the lower mold fixing seat 13 by fasteners. The front end of the inner cavity of mold 11 is a tapered inlet 111, the large diameter of which is greater than or equal to the diameter of steel pipe 5, and the small diameter is the same as the inner cavity diameter.

[0043] like Figure 5 As shown, curved lubricating oil grooves 120 are provided on the walls of the two semi-circular mold cavities. The two curved oil grooves are identical in shape, both being U-shaped. They communicate with the oil injection holes 110, and the vertical lines of the U-shapes of the two curved lubricating oil grooves 120 overlap with the four rows of oil injection holes. Straight lubricating oil grooves 121 are provided on the left and right connecting surfaces of the upper mold fixing seat 12 and the lower mold fixing seat 13. The two straight lubricating oil grooves 121 are connected to the two ends of the two curved lubricating oil grooves 120, respectively. One of the straight lubricating oil grooves 121 has an oil inlet 122, and the other straight lubricating oil groove 121 has an oil outlet 123.

[0044] Hydraulic system 2 includes an oil tank 21, a level sensor 22, a hydraulic pump 23, a switching valve 24, an oil tank temperature sensor 25, a lubricating oil proportional flow valve 26, a return oil temperature sensor 27, a relief valve 28, and a suction filter 29. The oil tank 21 contains the level sensor 22 and the oil tank temperature sensor 25. The outlet of the suction filter 29 is connected to the inlet of the hydraulic pump 23 via a pipeline; the outlet of the hydraulic pump 23 is connected to the inlet of the switching valve 24 via a pipeline, and is also connected to the relief valve 28. The outlet of the switching valve 24 is connected to the inlet of the lubricating oil proportional flow valve 26 via a pipeline. The outlet of the lubricating oil proportional flow valve 26 is connected to the inlet of the mold assembly 1 via a pipeline. The outlet of the mold assembly 1 is connected to the oil tank 21 via a pipeline, and the return oil temperature sensor 27 is installed on the pipeline between the outlet of the mold assembly 1 and the oil tank 21.

[0045] The lubricating oil recovery tank 3 is located below the mold assembly 1. An oil discharge port is provided on the lubricating oil recovery tank 3, and the discharge port is connected to the oil tank 21 via pipeline. The lubricating oil recovery tank 3 is used to collect lubricating oil dripping from the surface of the steel pipe during operation. A filter screen is installed inside the recovery tank 3 to filter impurities in the lubricating oil and prevent clogging of the oil pipe. The pulling trolley 4 is located at the rear of the mold assembly 1.

[0046] The flow path of the lubricating oil in this lubrication system is as follows: oil tank 21—oil suction filter 29—hydraulic pump 23—switching valve 24—lubricating oil proportional flow valve 26—mold assembly 1—oil inlet 122—straight lubricating oil groove 121—curved lubricating oil groove 120—oil outlet 123—oil tank 21. When the lubricating oil enters from the oil inlet 122, it enters the two curved lubricating oil grooves 120 from both the top and bottom directions, and then merges at the other end before flowing out from the oil outlet 123.

[0047] The drawing process of steel pipe 5 is as follows: The feeding mechanism feeds steel pipe 5 into the inner cavity of mold 11 with a certain thrust. Passing through the conical inlet 111 and the inner cavity of mold 11, the diameter of steel pipe 5 is reduced to a predetermined diameter. Once the rear end of steel pipe 5 emerges from the inner cavity of mold 11, the drawing trolley 4 clamps steel pipe 5 and generates a backward pulling force, pulling steel pipe 5 out of mold 11. The reduction in diameter of steel pipe 5 is determined by the ratio of the large opening to the small opening of the conical inlet 111. Simultaneously, the travel speed of steel pipe 5, also called the drawing speed, can be adjusted according to requirements.

[0048] On the one hand, this invention provides high-pressure oil through a hydraulic system to lubricate the steel pipe 5 during the drawing process, reducing its surface roughness and allowing it to pass smoothly through the inner cavity of the mold 11. On the other hand, since heat is generated during the drawing process, designing the curved lubricating oil groove as U-shaped or other shapes can extend its flow path, thereby reducing the temperature of the mold 11 and preventing deformation of the inner cavity of the mold 11.

[0049] To improve lubrication and cold drawing effects, this invention also proposes a lubrication control method for precision seamless steel tube cold drawing dies, comprising the following steps:

[0050] Step S1: Calculate the theoretical control voltage U1 related to speed, U2 related to temperature, and U3 related to diameter reduction ratio of the lubricating oil proportional flow valve (26) according to different process parameters. Specifically, they are divided into three categories:

[0051] The first category is based on the drawing speed v of the drawing machine, and the maximum drawing speed v of the drawing machine. max The maximum control voltage U of the lubricating oil proportional flow valve (26) max Calculate the speed-related theoretical control voltage U1, v max The value range is 0.3m / s-0.4m / s, and the specific formula is as follows:

[0052]

[0053] The second category is based on the return oil temperature error ΔT and the maximum return oil temperature error ΔT of mold component 1. max The theoretical control voltage U2 related to temperature error is calculated using the following formula:

[0054]

[0055] In the formula, ΔT=T back -T0, T back T represents the return oil temperature of mold component 1. back The return oil temperature is collected by sensor 27. T0 is the desired return oil temperature, and the value of T0 ranges from 20℃ to 30℃. ΔT max For the maximum return oil temperature error, ΔT max =T max -T0, T max The maximum return oil temperature threshold is defined as 65℃-75℃.

[0056] The third category is based on the reduction ratio δ during drawing of the steel pipe and the maximum reduction ratio δ. max The theoretical control voltage U3 related to the reduction ratio is calculated using the following formula:

[0057]

[0058] In the formula, D is the outer diameter of the steel pipe before drawing, d is the outer diameter of the steel pipe after drawing, and δ max The value range is 0.2-0.3;

[0059] Step S2: Set the control voltage of the lubricating oil proportional flow valve 26 to U = max{U1,U2,U3};

[0060] Step S3: After time t, where t ranges from 30s to 60s, determine the value of T. back ≥T max If the condition is met, stop pulling and issue an oil high temperature alarm to remind the lubricating oil to be cooled. If the condition is not met, repeat steps S1 to S3.

[0061] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A lubrication control method for a precision seamless steel pipe cold drawing die, characterized in that, The precision seamless steel tube cold drawing die lubrication system includes a die assembly (1) and a hydraulic system (2). The hydraulic system (2) provides high-pressure oil to the die (11) of the die assembly (1). The hydraulic system (2) includes an oil tank (21), a hydraulic pump (23), a switching valve (24), and a lubricating oil proportional flow valve (26). The hydraulic pump (23) is connected to the lubricating oil proportional flow valve (26) via the switching valve (24). The hydraulic system (2) also includes a return oil temperature sensor (27). The system is used to lubricate the steel pipe (5) during the drawing process of the drawing machine, and includes the following steps: Step S1: Calculate the speed-related theoretical control voltage of the lubricating oil proportional flow valve (26) according to different process parameters. Temperature-related theory control voltage Theoretical control voltage related to the reduction ratio Specifically, they are divided into three categories: The first category is based on the drawing speed of the drawing machine. Maximum drawing speed of the drawing machine The maximum control voltage of the lubricating oil proportional flow valve (26) Calculate the speed-related theoretical control voltage , The value range is 0.3m / s-0.4m / s, and the specific formula is as follows: ， The second category is based on the return oil temperature error of the mold component (1). and maximum return oil temperature error Calculate the theoretical control voltage related to temperature error The specific calculation formula is as follows: ， In the formula, , The return oil temperature of mold assembly (1) Data is collected by the return oil temperature sensor (27). To achieve the desired oil return temperature, The value range is 20℃-30℃. For the maximum return oil temperature error, , The maximum return oil temperature threshold is defined as 65℃-75℃. The third category is based on the reduction ratio of the drawn diameter of the steel pipe (5). With maximum drawing reduction ratio Calculate the theoretical control voltage related to the reduction ratio. The specific formula is as follows: ， In the formula, , The outer diameter of the steel pipe before drawing. The outer diameter of the steel pipe after drawing. The value range is 0.2-0.3; Step S2: Set the control voltage of the lubricating oil proportional flow valve (26) to... ; Step S3, after After a period of time, The value range is 30s-60s, and the judgment is... If the condition is met, stop pulling and issue an oil high temperature alarm to remind the lubricating oil to be cooled. If the condition is not met, repeat steps S1 to S3.

2. The lubrication control method for precision seamless steel pipe cold drawing die according to claim 1, characterized in that, The mold assembly (1) includes a mold (11), an upper mold fixing seat (12), and a lower mold fixing seat (13). The mold (11) is a hollow cylinder with a connecting flange at the front end. Multiple oil injection holes (110) communicating with the inner cavity are evenly opened on the cylinder. The inner cavity is for the steel pipe (5) to pass through. Both the upper mold fixing seat (12) and the lower mold fixing seat (13) are provided with semi-cylindrical mold cavities. The upper mold fixing seat (12) and the lower mold fixing seat (13) are detachably connected. The two semi-cylindrical mold cavities form a cylindrical mold cavity. The cylinder extends into the cylindrical mold cavity and is in close contact with the mold cavity wall. The connecting flange of the mold (11) is detachably connected to the upper mold fixing seat (12) and the lower mold fixing seat (13). Curved lubricating oil grooves (120) are provided on the walls of the two semi-cylindrical mold cavities. The curved lubricating oil grooves (120) are connected to the oil injection holes (110) of the upper mold fixing seat (12) and the lower mold fixing seat (13). The holes (110) are connected; straight lubricating oil grooves (121) are provided on the connecting surfaces of the upper mold fixing seat (12) and the lower mold fixing seat (13) on both sides; the two straight lubricating oil grooves (121) of the upper mold fixing seat (12) or the lower mold fixing seat (13) are respectively connected to the two ends of the curved lubricating oil groove (120); one of the straight lubricating oil grooves (121) is provided with an oil inlet (122), and the other straight lubricating oil groove (121) is provided with an oil outlet (123); the lubricating oil proportional flow valve (26) is connected to the oil inlet (122) pipe on the straight lubricating oil groove (121); the oil outlet (123) on the other straight lubricating oil groove (121) is connected to the oil tank (21) pipe; the return oil temperature sensor (27) is located on the pipe between the oil outlet (123) on the straight lubricating oil groove (121) and the oil tank (21).

3. The lubrication control method for precision seamless steel pipe cold drawing dies according to claim 1, characterized in that, The system also includes a lubricating oil recovery tank (3), which is located below the mold assembly (1). The lubricating oil recovery tank (3) has an oil discharge port, which is connected to the oil tank (21) via a pipeline.

4. The lubrication control method for precision seamless steel pipe cold drawing dies according to claim 3, characterized in that, The lubricating oil recovery tank (3) is equipped with a filter screen, which is used to filter the lubricating oil dripping from the mold assembly (1) when lubricating the steel pipe (5).

5. The lubrication control method for precision seamless steel pipe cold drawing die according to claim 2, characterized in that, The oil injection hole (110) is circular in shape and has a diameter of 2-3 mm.

6. The lubrication control method for precision seamless steel pipe cold drawing die according to claim 2, characterized in that, There are 24 oil injection holes (110), arranged in 4 rows on the circumferential direction of the cylindrical surface, with 6 holes in each row along the axial direction.

7. The lubrication control method for precision seamless steel pipe cold drawing dies according to claim 2, characterized in that, The curved lubricating oil groove (120) is U-shaped.

8. The lubrication control method for precision seamless steel pipe cold drawing die according to claim 2, characterized in that, A tapered inlet (111) is provided at the front end of the inner cavity of the mold (11). The large diameter of the tapered inlet (111) is greater than or equal to the diameter of the steel pipe (5), and the small diameter is the same as the inner cavity diameter. The tapered inlet (111) is used to reduce the diameter of the steel pipe (5).

9. The lubrication control method for precision seamless steel pipe cold drawing die according to claim 1, characterized in that, The system also includes a pulling trolley (4), which is located behind the mold assembly (1) and is used to clamp the steel pipe (5) and pull it backward.

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