Manufacturing method of equal-diameter perforated steel pipe

Abstract

The invention discloses a manufacturing method of an equal-diameter perforated steel pipe, and belongs to the technical field of pipe blank perforation. The method comprises the following steps: (1) heating a blank in a steel pipe manufacturing process; (2) the perforating process is improved; the process parameters in the heating process are adjusted, and the hole pattern design part and the perforating process of the perforating machine are improved: the taper angle of a roller outlet is reduced, the diameter of an ejector head is reduced, the length of the ejector head is increased, and the roller distance, the guide plate distance, the forward extension of the ejector head and the size of a feed angle are adjusted. The defects that high alloy steel is poor in thermoplasticity, and inner surface tearing, wall deviation, end outer diameter sudden change and the like are prone to occurring due to the fact that the diameter expanding amount is large in the hot rolling perforation process are overcome, the yield is increased, the rejection rate is reduced, and the contract redemption rate is increased.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a uniform diameter perforated steel pipe, belonging to the technical field of pipe blank perforation. Background Art

[0002] The amount of deformation that the piercing machine bears in the entire unit is getting larger and larger. The parameters that represent the piercing deformation are: diameter expansion rate, elongation coefficient, reduction at the rolled strip, and reduction before the plug.

[0003] The diameter expansion rate of hot-rolled perforated rough pipe is generally in the range of 5-20%, and the expansion rate of the tapered roller perforator is significantly higher than that of the barrel roller perforator. A large expansion rate is prone to internal and external surface defects or worsen uneven wall thickness, so it is best to use equal diameter or small expansion perforation.

[0004] When producing high-alloy steel pipes, the piercing machine rolls usually used are conical piercing machines with a diameter expansion rate of about 7%. Due to the poor thermoplasticity of high-alloy steels, defects such as inner surface tearing, wall deviation, and sudden change in outer diameter at the end are very likely to occur during the production of high-alloy steels. Therefore, a new process that meets the requirements of high-alloy steel piercing is urgently needed on site. Equal-diameter hot-rolled piercing can effectively solve the problems of inner surface tearing, wall deviation, and sudden change in outer diameter at the end during the hot-rolled piercing process. Summary of the invention

[0005] The present invention aims to provide a method for manufacturing equal-diameter perforated steel pipes, which belongs to a method for manufacturing high-alloy steel. The present invention is mainly used to solve the problem that high-alloy steel has poor thermoplasticity and is very likely to produce defects such as inner surface tearing, wall deviation, and sudden change in outer diameter at the end due to large diameter expansion during hot rolling and perforation, thereby improving the yield rate, reducing the scrap rate, and improving the contract fulfillment rate.

[0006] The technical concept of the present invention is as follows: During the process of expanding and punching, the metal is subjected to a large transverse tensile stress, which can easily cause tearing of the inner surface of the metal and instability when rolled to the tail. Compared with expanding and punching, equal-diameter punching has a smaller transverse tensile stress, which can stabilize the rolling process and improve the quality of the inner surface of the steel pipe. The method adopted by the present invention is: by designing the tooling and adjusting the rolling parameters, the purpose of equal-diameter punching is achieved. The main factors that determine the outer diameter of the rough pipe are the hole design of the punch and the adjustment of the punch parameters: the hole design mainly involves the roller, the head, the guide plate, and the push rod; the punching parameters involve the roller spacing, the guide plate spacing, the head extension, and the feed angle (after the head is reduced, in order to ensure the wall thickness, the roller spacing and the feed angle must be adjusted to compensate for the increase in wall thickness caused by the reduction of the head). Through this process, a steel pipe with the same outer diameter of the blank and the rough pipe can be produced. The outer diameter size of the manufactured steel pipe is controlled to meet the rolling requirements of the rolling mill to ensure the dimensional accuracy requirements of the finished product. The inner hole is inspected for defects such as cracks, hairlines, scratches, and burrs, and the outer surface is inspected for defects such as cracks, scratches, and folds.

[0007] The manufacturing method of the steel pipe provided by the present invention comprises the following production process: blank inspection → blank sawing → centering → blank heating → perforation → straightening and flattening → pickling → grinding → cold rolling → degreasing → heat treatment → straightening and flattening → pickling → finished product. The present invention improves the key process flow: (1) blank inspection; (2) blank sawing; (3) centering; (4) blank heating; (5) perforation process.

[0008] The present invention provides a method for manufacturing a uniform diameter perforated steel pipe, comprising the following contents: (1) Billet inspection: The blanks were inspected and the ultrasonic non-destructive testing did not exceed the φ3mm bottom wave testing sensitivity standard line, and no large defects or cracks were found on the outer surface; (2) Billet sawing: The finished product is cut to size based on marking and sawing according to its weight. The length of the blank is 1300mm-3200mm, and the end face cutting slope is ≤3mm.

[0009] (3) Centering drilling: When drilling the centering hole, locate the head position. The centering hole has a diameter of 40mm and a depth of 20mm. The centering hole is smooth and has no burrs. (4) Billet heating: Heating is carried out in an inclined bottom furnace, and the heating system is strictly carried out in accordance with the following process conditions: ① preheating section temperature: 950±30℃, heating time: 4 hours; ② heating section temperature: 1100±20℃, heating time: 2 hours; ③ equalizing section temperature: 1180±20℃, heating time: 0.5 hour.

[0010] In the heating section, the blank needs to be flipped 180°: during the heating process, the blank needs to be rolled forward every half an hour, and the bottom side needs to be turned up during rolling, so it needs to be 180 degrees to prevent the generation of yin and yang sides during heating.

[0011] (5) Punch deformation The present invention improves the punching process parameters and the punching machine hole design, which specifically includes the following contents: ① Some improvements in the hole design of the punch include: The exit cone angle of the roller is 2.8°. Reducing the exit cone angle of the roller can limit the increase in the outer diameter of the steel pipe during the rolling process.

[0012] The piercing machine has a head diameter of 180mm, a head length of 335mm, a guide plate size of 210-220mm, and a head rod diameter of 168mm. Reducing the head diameter and increasing the head length ensures stable deformation and reduced diameter expansion during hot rolling piercing.

[0013] ②The top curve design is as follows: The plug diameter D is 180mm, the plug length L is 335mm, the plug reverse cone length L4 is 15mm, the sizing section length L2 is 5mm, the averaging section length L3 is 115mm, and the diameter of the ejector rod is 168mm. The plug tip arc R2 is 24mm, the deformation section arc R1 is 396.96mm, and the reverse cone arc R3 is 18mm. Theoretical weight is 45kg.

[0014] ③The perforation process parameters are adjusted as follows: The piercing parameters involve the roll spacing, guide plate spacing, plug extension, and feed angle. D1 is the billet diameter, L is the plug length; the roll spacing is designed to be D1*0.9, the guide plate spacing is designed to be D1*0.98, the plug extension is designed to be L*0.53, the roll speed is designed to be 22r / min, and the feed angle is designed to be 8°.

[0015] Beneficial effects of the present invention: The present invention provides a manufacturing method for equal-diameter perforations, which is innovatively manufactured through a perforation process. The outer diameter size of the manufactured rough pipe is controlled to meet the rolling requirements of the rolling mill, ensuring the dimensional accuracy requirements of the finished product. The inner hole is inspected to be free of defects such as cracks, hairlines, scratches, and burrs, and the outer surface is inspected to be free of defects such as cracks, scratches, and folds, thereby greatly reducing the production cost and improving the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the plug curve designed for the present invention.

[0017] Figure 2 Schematic diagram of the perforation process.

[0018] Figure 3 for Figure 2 Partial cross-sectional view along line AA.

[0019] Figure 4 for Figure 2 Top view of the .

[0020] In the figure: 1-roller, 2-guide plate, 3-head, 4-thrust rod, 5-blank, 6-rough pipe, a is the feed angle, which is the angle between the roll and the rolling center. DETAILED DESCRIPTION

[0021] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0022] Comparative Example 1: Implementation process before improvement Φ219 billet expansion and perforation Φ235*15mm (1) Billet inspection: The size of the blank is Φ219mm, and the ultrasonic non-destructive testing does not exceed the bottom wave testing sensitivity standard line of φ3mm. No large defects or cracks are found on the outer surface.

[0023] (2) Billet sawing The finished product is cut to size based on marking and sawing according to its weight. The length of the blank is 1500mm and the end face cutting inclination is ≤3mm.

[0024] (3) Centering drilling The centering hole is used to locate the head position. The diameter of the centering hole is 40mm and the depth is 20mm. The centering hole is smooth and free of burrs.

[0025] (4) Billet heating The billet is heated in an inclined bottom furnace, and the heating system is strictly in accordance with the following table. In the heating section, the billet needs to be turned 180°:

[0026] (5) Punch deformation The control parameters are as follows: the outlet cone angle of the roll is 3.2°; the head diameter of the piercing machine is 194mm, the head length is 280mm, the guide plate size is 220-230mm, and the diameter of the push rod is 180mm; the roll spacing is 201mm, the guide plate spacing is 224mm, the head extension is 46mm, the roll speed is 25r / min, and the feed angle is 10°.

[0027] Through this comparative process, the specification of the Φ219mm billet after expansion and perforation is Φ235*15mm. The main problems are: warping of the inner hole and horseshoe mouth at the tail.

[0028] The horseshoe-mouth defect caused by the expansion perforation can only be eliminated by sawing. The tail length is about 350mm and the yield loss is about 3.5%.

[0029] Embodiment 1: The manufacturing process of the equal-diameter perforated steel pipe using the method of the present invention comprises the following specific steps: Φ219 billet equal diameter perforation Φ219*15mm (1) Blank inspection: The size of the blank is Φ219mm, and the ultrasonic non-destructive testing does not exceed the bottom wave testing sensitivity standard line of φ3mm. No large defects or cracks are found on the outer surface.

[0030] (2) Billet sawing The finished product is cut to size based on marking and sawing according to its weight. The length of the blank is 1500mm and the end face cutting inclination is ≤3mm.

[0031] (3) Centering drilling The centering hole is used to locate the head position. The diameter of the centering hole is 40mm and the depth is 20mm. The centering hole is smooth and free of burrs.

[0032] (4) Billet heating The billet is heated in an inclined bottom furnace, and the heating system is strictly in accordance with the following table. In the heating section, the billet needs to be turned 180° (the billet needs to be turned forward once every half an hour during heating, and the bottom side needs to be turned up when rolling, that is, turned 180° to prevent the generation of yin and yang sides during heating):

[0033] (5) Punch deformation This embodiment improves the punching process parameters and the punching machine hole design, specifically including the following: ① Some improvements in the hole design of the punch include: The exit cone angle of the roller is 2.8°. Reducing the exit cone angle of the roller can limit the increase in the outer diameter of the steel pipe during the rolling process.

[0034] The piercing machine has a head diameter of 180mm, a head length of 335mm, a guide plate size of 210-220mm, and a head rod diameter of 168mm. Reducing the head diameter and increasing the head length ensures stable deformation and reduced diameter expansion during hot rolling piercing.

[0035] ②The top curve design is as follows: Figure 1 This is the design drawing of the plug curve: the plug diameter D is 180mm, the plug length L is 335mm, the plug reverse cone length L4 is 15mm, the sizing section length L2 is 5mm, the averaging section length L3 is 115mm, and the diameter of the ejector rod is 168mm. The plug tip arc R2 is 24mm, the deformation section arc R1 is 396.96mm, and the reverse cone arc R3 is 18mm. Theoretical weight is 45kg.

[0036] The technical requirements for the plug are as follows: chemical composition: Mo matrix, Ti=0.5%, Zr=0.08-0.10%, C=0.02-0.03%; the hardness should be uniform and the transition section connection should be smooth; in addition to meeting the dimensions shown in the figure, the surface of the piercing machine plug shell is not allowed to have any defects that damage the surface of the steel pipe, such as scratches, tears, etc.; the casting body should not have defects, especially shrinkage holes, cracks or weld breakpoints; no chamfer 1*45° is added.

[0037] ③The perforation process parameters are adjusted as follows: The piercing parameters involve the roll spacing, guide plate spacing, plug extension, and feed angle. D1 is the billet diameter (219mm), L is the plug length; the roll spacing is designed to be D1*0.9, i.e. 197mm, the guide plate spacing is designed to be D1*0.98, i.e. 215mm, the plug extension is designed to be L*0.53, i.e. 177mm, the roll speed is designed to be 22r / min, and the feed angle is designed to be 8°.

[0038] Through the above hole design and adjustment of perforation process parameters, the final specification of the rough pipe is: Φ219×15mm, achieving equal diameter perforation.

[0039] After the equal-diameter perforation method is adopted, the horseshoe mouth defect of the tail is eliminated.

[0040] After using the design of the present invention, it is easy to realize mass production, and the project implementation effect is good. The present invention solves the problem that the high alloy steel has poor thermoplasticity, and is very likely to produce defects such as inner surface tearing, wall deviation, and end outer diameter mutation due to large diameter expansion during hot rolling and piercing, directly increases the yield rate by 3.5%, reduces the scrap rate, and improves the contract fulfillment rate.

Claims

1. A method for manufacturing a uniform diameter perforated steel pipe, characterized in that Includes the following: (1) Billet inspection: The blank was inspected and the ultrasonic non-destructive testing did not exceed the φ3mm bottom wave testing sensitivity standard line, and no large defect cracks were found on the outer surface; (2) Billet sawing: The finished product is cut to size according to the weight of the finished product. The length of the blank is 1300mm-3200mm, and the end face cutting slope is ≤3mm; (3) Centering drilling: When drilling the centering hole, locate the head position. The centering hole has a diameter of 40mm and a depth of 20mm. The centering hole is smooth and has no burrs. (4) Billet heating: Heating is carried out in an inclined bottom furnace, and the heating system is strictly carried out in accordance with the following process conditions: ① preheating section temperature: 950±30℃, billet heating time: 4 hours; ② heating section temperature: 1100±20℃, heating time: 2 hours; ③ soaking section temperature: 1180±20℃, heating time: 0.5 hours; (5) Punch deformation: It includes improvements in the hole design of the piercing machine and adjustments to the piercing process: reducing the roller outlet cone angle, reducing the plug diameter, increasing the plug length, adjusting the roller spacing, guide plate spacing, plug extension, and feed angle.

2. The method for manufacturing a uniform diameter perforated steel pipe according to claim 1, characterized in that: Some improvements in the punch hole design include: The exit cone angle of the roller is 2.8°, which limits the increase in the outer diameter of the steel pipe during the rolling process; the piercing machine has a head diameter of 180mm, a head length of 335mm, a guide plate size of 210-220mm, and a mandrel diameter of 168mm; this ensures that the deformation is stable and the diameter expansion is reduced during the hot rolling piercing process.

3. The method for manufacturing a uniform perforated steel pipe according to claim 2, characterized in that: The plug design is as follows: the plug reverse cone length L4 is 15mm, the sizing section length L2 is 5mm, the sizing section length L3 is 115mm, the plug tip arc R2 is 24mm, the deformation section arc R1 is 396.96mm, and the reverse cone arc R3 is 18mm; the theoretical weight is 45kg.

4. The method for manufacturing a uniform diameter perforated steel pipe according to claim 3, characterized in that: The technical parameters of the plug are: chemical composition: Mo matrix, Ti=0.5%, Zr=0.08-0.10%, C=0.02-0.03%; the hardness should be uniform and the transition section connection should be smooth.

5. The method for manufacturing a uniform diameter perforated steel pipe according to claim 1, characterized in that: The piercing process parameters are adjusted as follows: D1 is the billet diameter, L is the plug length; the roller spacing is D1*0.9, the guide plate spacing is D1*0.98, the plug extension is L*0.53, the roller speed is 22r / min, and the feed angle is 8°.

Images