A method for forging forming an ultra-long and ultra-high pressure pipe

Abstract

The application relates to a forging forming method of an ultra-long, high-performance and high-toughness ultra-long and super-high pressure pipe, which utilizes an oil press and a radial precision forging machine to produce the ultra-long and super-high pressure pipe by changing a material deformation mode and controlling a metal plastic deformation process, and comprises the following steps: 1) high-temperature diffusion heating; 2) staggered protection of ingot plates; 3) upsetting; 4) length drawing; 5) intermediate forging; 6) hot sawing; 7) normalizing; 8) heating; 9) precision forging forming; 10) hot sawing; and 11) complete annealing. The process is not complex, the required equipment is little, the electric slag ingot is subjected to high-temperature diffusion heating, micro-segregation in the steel ingot can be removed, chemical components are uniform, diffusion impurity distribution is realized, banding is improved, the plasticity of the steel is improved, after primary forging, normalizing and secondary forging, not only can the cast structure of the original blank be fully broken, original structure defects such as pores and loose are welded, the grains are refined, and the structure is uniform, but also the length limitation of the forging equipment can be avoided, the performance and the fracture toughness of the product are improved, and the service life is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of metal plastic forming technology, and relates to a forging method for ultra-long, high-performance, and high-toughness ultra-long ultra-high pressure tubes. Background Technology

[0002] Ultra-high pressure tubular reactors typically consist of multiple jacketed tube sections, each with an external cooling water jacket. Each section is generally 7–12 meters long and is characterized by its thinness, length, and thickness. They often operate in environments with high temperature and pressure, complex external corrosion, and low-cycle fatigue, making their working conditions extremely complex and demanding. In recent years, with the rapid development of the polyethylene industry, polymerization stress and reactor production capacity have increased rapidly. To improve the load-bearing capacity and fatigue life of ultra-high pressure polyethylene reactor tubes and ensure safe, reliable, and long-term operation of the equipment, there is an urgent need for ultra-long, high-performance, and high-toughness ultra-high pressure tubes. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a forging method for producing ultra-long and ultra-high pressure tubes by using a hydraulic press and a radial precision forging machine, and controlling the metal plastic deformation process by changing the material deformation mode.

[0004] The technical solution of this invention is implemented as follows:

[0005] A forging method for an ultra-long, ultra-high pressure tube includes the following steps:

[0006] Step 1) High-temperature diffusion heating: The electroslag ingot is loaded into a chamber heating furnace and heated to 1200℃~1270℃ through a three-stage heating method. The temperature is held for 25~30h to remove micro-segregation in the steel ingot, homogenize the chemical composition, and achieve plastic forging.

[0007] Step 2) Offset the ingot tail guard plate: Offset the ingot tail guard plate on the hydraulic press and flatten the ingot tail end face;

[0008] Step 3) Upsetting: Upsetting is performed using a hydraulic press to ensure that the height-to-diameter ratio after upsetting is between 0.64 and 0.72, and the upsetting coefficient is between 1.7 and 2.4;

[0009] Step 4) Lengthening: Lengthen twice on the upsetting plate and the lower platform, with a reduction rate of 35% to 45%, and then lengthen square and octagonal shapes on the upper and lower flat anvils;

[0010] Step 5) Forging intermediate billet: Forging intermediate billet using a radial forging machine to ensure that the forging ratio from intermediate billet to finished product is 2.5 to 4;

[0011] Step 6) Hot sawing: Hot saw off the process waste at both ends, prioritizing the amount of material removed from the ingot tail, and then hot sawing to the specified length according to the process length.

[0012] Step 7) Normalizing: Hold at 550-650℃ for 2-4 hours, cool rapidly to 280-320℃, put into the furnace and hold at 280-320℃ for 4-6 hours, rapidly heat up to 890±10℃, hold for ≥3 hours, and air cool to 280-320℃ after taking out of the furnace.

[0013] Step 8) Heating: Rapidly raise the temperature to 1000-1050℃ and hold for 1.5-2.5 hours;

[0014] Step 9) Precision forging: Forging is performed using a radial forging machine. During the forming process, the dimensions are controlled according to the hot dimensions. No deviation is allowed. The dimensions are measured and adjusted in a timely manner during the forming process to prevent large differences in the dimensions at both ends. The initial forging temperature is controlled at 950-850℃, and the final forging temperature is ≥800℃.

[0015] Step 10) Hot sawing: After the finished product is hot sawed, the length of the process hot dimension must be guaranteed. After hot sawing, the forging is air-cooled on the cooling bed to 250-320℃ to prevent the material from bending. Avoid the end of the forging and measure the temperature in the middle of the forging. After reaching the temperature, use 7500mm C-type clamps to lift and cut the material. Ground personnel assist with the hook to prevent bumps.

[0016] Step 11) Full annealing: Air cool to 250-320℃ and put into the furnace for full annealing. Remove from the furnace at the set temperature to complete the forging process of the ultra-long and ultra-high pressure tube.

[0017] The length of the ultra-long ultra-high pressure tube is ≥16000mm, and the outer diameter is ≤250mm.

[0018] The ultra-long and ultra-high pressure tube requires two forging processes. The first forging is an upsetting and drawing process to create an intermediate billet. The second forging is a process where the billet is normalized and then reheated in a furnace to form the finished product.

[0019] The positive effects of this invention are as follows: the process flow is not complex, requires few equipment, and the high-temperature diffusion heating of the electroslag ingot can remove micro-segregation in the steel ingot, homogenize the chemical composition, diffuse impurity distribution, improve banding, and enhance the plasticity of the steel. Through a first forging followed by normalizing and then a second forging, not only can the as-cast structure of the original billet be fully broken down, original structural defects such as porosity and looseness be welded together, grains be refined, and the structure homogenized, but the length limitations of forging equipment can also be avoided, improving the product's performance and fracture toughness, and increasing its service life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the original blank for an ultra-long, ultra-high pressure tube.

[0021] Figure 2 This is a schematic diagram of hot sawing the intermediate billet for forging of ultra-long and ultra-high pressure tubes.

[0022] Figure 3This is a schematic diagram of the forging process for ultra-long and ultra-high pressure pipes.

[0023] The diagram is labeled as follows: L0, original billet length; D0, original billet diameter; L1, total length of intermediate billet; D1, diameter of intermediate billet; L2, length of waste material at the tail end of the ingot; L3, length of intermediate billet blanking.

[0024] 1. M2 control mechanism; 2. Ultra-long and ultra-high pressure forgings; 3. Radial forging machine hammer; 4. M1 control mechanism. Detailed Implementation

[0025] The technical solution of the present invention will be illustrated below with specific embodiments:

[0026] Example 1: The electroslag ingot used for the ultra-long and ultra-high pressure forging in this example weighs 4.8t, the crystallizer specifications are Φ660 / Φ710mm, the material is 26CrNi4MoV, the forging specifications are Φ180*18720mm, and the forging operation process of the ultra-long and ultra-high pressure tube is as follows:

[0027] Step 1) High-temperature diffusion heating: The electroslag ingot is loaded into a chamber heating furnace and heated to 1250℃ through a three-stage heating method. It is held for 25 hours to remove micro-segregation in the steel ingot, homogenize the chemical composition, and achieve plastic forging.

[0028] Step 2) Offset the ingot tail guard plate: Offset the ingot tail guard plate on the hydraulic press and flatten the ingot tail end face;

[0029] Step 3) Upsetting: Upset using a hydraulic press to a height of 700mm (diameter of Φ1060mm);

[0030] Step 4) Lengthening: Lengthen twice on the upsetting plate and the lower platform, with the reduction rate controlled at 40%. Lengthen to 400mm on the hot square on the upper and lower flat anvils, and then to 420mm on the hot square.

[0031] Step 5) Forging intermediate billet: Precision forging to hot Φ320mm using a radial forging machine;

[0032] Step 6) Hot sawing: Cut off the waste material at a fixed length of 460±30mm from the tail end of the ingot, and then cut the material at a fixed length of 6500±30mm using the cut surface.

[0033] Step 7) Normalizing: Hold at 550-650℃ for 2 hours, then quickly cool to 280-320℃, put into the furnace and hold at 280-320℃ for 5 hours, then quickly heat up to 890±10℃, and hold for ≥3 hours. Remove from the furnace and air cool to 280-320℃.

[0034] Step 8) Heating: Rapidly raise the temperature to 1000±10℃ and hold for 1.5 hours;

[0035] Step 9) Precision forging: Forge to a finished product Φ183mm using a radial forging machine. Control the hot dimensions during the forming process, and do not allow any deviation. Measure the dimensions in a timely manner during the forming process to make adjustments and prevent large differences in dimensions at both ends. Control the initial forging temperature to 950~850℃ and the final forging temperature to ≥800℃.

[0036] Step 10) Hot sawing: Hot saw off ~300mm of waste material from the tail end and riser end of the ingot. After hot sawing, air cool the forging on the cooling bed to 250~320℃ to prevent the material from bending. Avoid the end of the forging and measure the temperature in the middle of the forging. After reaching the temperature, use 7500mm C-type clamps to lift and unload the material. Ground personnel assist with the hook to prevent bumps.

[0037] Step 11) Full annealing: Air cool to 250-320℃ and put into the furnace for full annealing. Remove from the furnace at the set temperature to complete the forging process of the ultra-long and ultra-high pressure tube.

[0038] As shown in the figure, the figures of this invention are labeled as follows: L0 is the original billet length; D0 is the original billet diameter; L1 is the total length of the intermediate billet; D1 is the diameter of the intermediate billet; L2 is the length of the scrap at the tail end of the ingot; L3 is the length of the intermediate billet blank; 1 is the M2 manipulator; 2 is the ultra-long ultra-high pressure forging; 3 is the radial forging machine hammer; 4 is the M1 manipulator. During the forming process, the ultra-long ultra-high pressure forging 2 is held by the M2 manipulator 1 and the M1 manipulator 4, rotates around its own axis and moves axially. It is subjected to high-frequency pulsed multi-directional forging by the four radial forging machine hammers 3 symmetrically distributed around the billet. This allows the billet to be subjected to triaxial compressive stress during deformation, which is beneficial to eliminate internal defects in the billet, improve the microstructure segregation, and obtain a uniform and fine microstructure with ideal metal fiber flow direction. Moreover, the temperature drop during the forging process is small, which makes it easy to achieve near-isothermal forging. It can better control the grain size and achieve fine grain forging of the entire cross section.

Claims

1. A forging method for an ultra-long, ultra-high pressure tube, characterized in that, Includes the following steps: Step 1) High-temperature diffusion heating: The electroslag ingot is loaded into a chamber heating furnace and heated to 1200℃~1270℃ through a three-stage heating method. The temperature is held for 25~30h to remove micro-segregation in the steel ingot, homogenize the chemical composition, and achieve plastic forging. Step 2) Offset the ingot tail guard plate: Offset the ingot tail guard plate on the hydraulic press and flatten the ingot tail end face; Step 3) Upsetting: Upsetting is performed using a hydraulic press to ensure that the height-to-diameter ratio after upsetting is between 0.64 and 0.72, and the upsetting coefficient is between 1.7 and 2.4; Step 4) Lengthening: Lengthen twice on the upsetting plate and the lower platform, with a reduction rate of 35% to 45%, and then lengthen square and octagonal shapes on the upper and lower flat anvils; Step 5) Forging intermediate billet: Forging intermediate billet using a radial forging machine to ensure that the forging ratio from intermediate billet to finished product is 2.5 to 4; Step 6) Hot sawing: Hot saw off the process waste at both ends, prioritizing the amount of material removed from the ingot tail, and then hot sawing to the specified length according to the process length. Step 7) Normalizing: Hold at 550-650℃ for 2-4 hours, cool rapidly to 280-320℃, put into the furnace and hold at 280-320℃ for 4-6 hours, rapidly heat up to 890±10℃, hold for ≥3 hours, and then air cool to 280-320℃ after removing from the furnace. Step 8) Heating: Rapidly raise the temperature to 1000-1050℃ and hold for 1.5-2.5 hours; Step 9) Precision forging: Forging is performed using a radial forging machine. During the forming process, the dimensions are controlled according to the hot dimensions. No deviation is allowed. The dimensions are measured and adjusted in a timely manner during the forming process to prevent large differences in the dimensions at both ends. The initial forging temperature is controlled at 950-850℃, and the final forging temperature is ≥800℃. Step 10) Hot sawing: After the finished product is hot sawed, the length of the process hot dimension must be guaranteed. After hot sawing, the forging is air-cooled on the cooling bed to 250-320℃ to prevent the material from bending. Avoid the end of the forging and measure the temperature in the middle of the forging. After reaching the temperature, use 7500mm C-type clamps to lift and cut the material. Ground personnel assist with the hook to prevent bumps. Step 11) Full annealing: Air cool to 250-320℃ and put into the furnace for full annealing. Remove from the furnace at the set temperature to complete the forging process of the ultra-long and ultra-high pressure tube.

2. The forging method for an ultra-long, ultra-high pressure tube according to claim 1, characterized in that, The length of the ultra-long ultra-high pressure tube is ≥16000mm, and the outer diameter is ≤250mm.

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