Forging method of H13 extrusion container lining for special extrusion forming

Abstract

The invention relates to a forging method of an H13 extrusion container lining for special extrusion forming. Comprising the following steps that (1) an electroslag ingot is placed in a furnace to be heated, heat preservation is conducted at the temperature of 450-550 DEG C, the temperature is increased to 800-900 DEG C at the speed smaller than or equal to 60 DEG C / h for heat preservation, then the temperature is increased to 1250-1270 DEG C at the speed smaller than or equal to 120 DEG C / h for heat preservation, (2) an upper spherical upsetting plate lower platform is adopted to conduct upsetting in the axial direction, upsetting is conducted in the radial direction, upsetting is conducted in the other radial direction, the two times of radial upsetting form an angle of 90 degrees, and the electroslag ingot is drawn out in the axial direction to form a square blank; (3) axial upsetting is carried out, a punch is used for punching a through hole, and a saddle is used for expanding after punching; the method comprises the following steps of (1) forging blanks, (2) forging the blanks, (3) forging the blanks, (4) drawing on an upper-flat lower V anvil by using a mandrel with the size 10-20mm smaller than that of the holes to the length of an extrusion container, (5) reaming on the upper and lower flat anvils by using a mandrel supporter to the size of a finished product, (6) carrying out hole closing, finishing forming and end face flattening on the upper and lower V anvils, and (7) feeding the forged blanks to an annealing furnace for heat treatment. The products are good in consistency and uniformity and high in production efficiency, and process excess materials on the inner wall are reduced.

Description

Technical Field

[0001] This invention belongs to the field of special steel forging technology, specifically relating to a forging method for H13 extrusion cylinder bushings for special extrusion molding. Background Technology

[0002] The H13 extrusion cylinder is a core component of extrusion equipment, also known as the extrusion chamber. It is one of the main extrusion tools in an extrusion press, and its material cost is the highest among extrusion tools, far exceeding that of other extrusion tools such as extrusion pads, extrusion rods, and extrusion dies. Especially for extrusion cylinders of large extrusion presses, the manufacturing cost is even higher. For example, the manufacturing cost of the extrusion cylinder for a 125 MN extrusion press exceeds 5 million yuan, and the cost of the extrusion cylinder often accounts for more than 30% of the total extrusion cost. The extrusion cylinder must withstand high temperature, high pressure, alternating loads, and high friction during operation, making its working conditions extremely harsh. Currently, extrusion cylinder blanks are mainly manufactured using a forging method involving H13 electroslag ingots, upsetting, punching, reaming, mandrel elongation, and finishing. This manufacturing method has the following problems: Due to the large size of the extrusion cylinder and insufficient deformation during the process, the hypoeutectic carbides were not fully broken down, resulting in minimal improvement in the particle size and distribution of the carbides. This led to cracking in the early stages of use, affecting the service life. During the forming process, uneven deformation resulted in irregular waste material at both ends, and the tapered inner hole formed during the mandrel elongation process, leading to a low final yield and high manufacturing costs. Furthermore, the sawing process at both ends after forging was prone to skewing, causing the entire workpiece to be scrapped.

[0003] With technological advancements and iterative upgrades of extrusion equipment, extrusion equipment is developing towards larger extrusion pressures and more complex forming processes. The extrusion process has also evolved from primarily producing extruded non-ferrous metals such as aluminum alloys and magnesium alloys, which are easily deformable, have good plasticity, and low deformation temperatures, to an emerging industry producing extruded special alloy profiles such as stainless steel, heat-resistant steel, corrosion-resistant steel, high-temperature alloys, and copper alloys, which are difficult to deform, have poor plasticity, and high deformation temperatures. For example, thermal power boiler tubes, automotive flanges, omega tubes, finned tubes, profiles for nuclear power, military applications, high-speed rail applications, and aircraft applications are all formed using extrusion processes. The extruded workpieces have high temperatures, poor plasticity, and high deformation resistance. The extrusion dies operate in extremely harsh environments with high temperatures, high pressures, and high friction. Therefore, the die steel is required to have high hardness, strength, impact toughness, and thermal fatigue performance at the operating temperature.

[0004] Therefore, the current manufacturing method of H13 extrusion cylinders cannot meet the needs of development. Developing new forging methods for extrusion cylinders to improve internal quality and maintain the original cost competitiveness is the trend of industry development. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings in the prior art and provide a forging method for H13 extrusion cylinder bushings for special extrusion molding. This method solves a series of problems such as poor quality stability, low yield, and low production efficiency. It can meet the requirements for extrusion molding of special alloy profiles such as stainless steel, heat-resistant steel, corrosion-resistant steel, high-temperature alloys, and copper alloys that are difficult to deform, have poor plasticity, and high deformation temperature.

[0006] The technical solution of this invention is implemented as follows: a forging method for an H13 extrusion cylinder bushing for special extrusion molding, the forging method comprising the following steps: Step 1) Place the electroslag ingot in the furnace and heat it. First, hold it at a temperature of 450-550℃, then raise the temperature to 800-900℃ at a rate of ≤60℃ / h and hold it there. Then raise the temperature to 1250-1270℃ at a rate of ≤120℃ / h and hold it there. The holding time is calculated as 3.0-4.0h per 100mm cross-sectional diameter. After holding it at 1250-1270℃ for 3h, remove it from the furnace and remove the protective plate. Then return it to the furnace to continue holding it for the required time. After the holding time is completed, remove it from the furnace and forge it. Step 2) After the electroslag ingot from the furnace in Step 1) is heated, it is sent to the hydraulic press. The upper spherical upsetting plate and the lower platform are used to upset the electroslag ingot along the axial direction. The height after upsetting is 0.5 to 0.6 times the original height. The upset billet is then upset along one radial direction on the upper plate and the lower platform, with a reduction of 35% to 55%. The upset billet is then rotated 90° and upset along another radial direction on the upper plate and the lower platform, with a reduction of 35% to 55%. The two radial upsettings are at a 90° angle to each other. Then, the billet is drawn along the axial direction to a square shape using upper and lower flat anvils, chamfered, and reduced by 40 to 80 mm. The ratio of the length of the drawn billet to the side length of the drawn square is controlled between 1.8 and 2.4. Step 3) The billet drawn in Step 2) is axially upset to a height-to-diameter ratio of 0.45 to 0.65. Then, a punch is used to punch a through hole. The diameter of the punch is no more than 1 / 3 of the diameter of the billet after upsetting. After punching, a lever is used to further enlarge the hole. The wall thickness after enlargement is at least 400 mm less than the final extrusion cylinder forging billet wall thickness. Step 4) Using a mandrel 10-20mm smaller than the hole size, the blank after the hole enlargement in Step 3) is drawn out on an upper flat and lower V anvil until it reaches the length of the extrusion cylinder. The two ends are flattened to prevent horseshoe or irregular shapes from forming. The wall thickness of the drawn blank should be at least 200mm less than the final wall thickness of the extrusion cylinder forging blank. Step 5) Use a reamer to enlarge the cylindrical billet from Step 4) on the upper and lower flat anvils to the final size, ensuring uniform wall thickness. Note that the rotation angle of the forging billet should be adjusted in time during the enlargement process to ensure the uniformity of the wall thickness of the forging billet after enlargement. When the reamer is used, the deformation area of ​​the metal is subjected to better stress, making it less prone to cracking. The metal has good fluidity, and the difference in wall thickness is easy to control. After the enlargement is completed and the end face is flattened, return it to the furnace for reheating. Return it to the 1200-1250℃ heating furnace and hold it for 1.0-2.0 hours before taking it out of the furnace for forging. Step 6) After the blank in Step 5) is enlarged, the blank is 10-15mm smaller on the upper and lower V anvils, finished and shaped, and the end face is flattened to obtain the required extrusion cylinder forging blank size; Step 7) Send the billet after forging in Step 6) to an annealing furnace for heat treatment.

[0007] In step 1), after holding at 1250-1270℃ for 3 hours, the ingot is removed from the furnace and the protective plate is removed. Then it is returned to the furnace to continue to make up for the remaining holding time. The total holding time required for the electroslag ingot is calculated based on 3.0-4.0 hours per 100mm cross section. Then, 3.5 hours is subtracted to get the remaining holding time. After the holding is completed, the ingot is removed from the furnace for forging. This reduces the auxiliary time such as removing the protective plate during the main deformation process, which is conducive to the compaction and welding during the deformation process.

[0008] In step 5), after the hole is enlarged and the end face is flattened, the furnace is returned to the furnace for reheating. The furnace is heated to 1200-1250℃ and held for 1.0-2.0 hours before being taken out of the furnace for forging.

[0009] Throughout the entire forging process described above, depending on the material temperature, the process may involve either reheating in the furnace or continuing to the next step.

[0010] Using this forging method solves the problems of conventional production methods and has the following positive effects: This invention provides a forming method that involves forging at high temperature for an extended period, using a special hydraulic press for blank deformation, upsetting, punching, mandrel elongation, lever hole enlargement, and finishing of the outer diameter and end face. This method achieves a uniform microstructure, eliminates the taper of the forged blank's inner hole, and reduces waste material at both ends. This approach solves problems such as poor microstructure uniformity, significantly improves material yield, and reduces manufacturing costs.

[0011] First, the product consistency and uniformity are good, and the utilization rate is increased by about 5%. Second, the two ends of the forging billet are flattened in each firing, and the entire forging billet is fully utilized, eliminating the waste material from sawing the two ends and improving production efficiency. Third, the final forming uses the frame hole expansion method to eliminate the inner wall taper and reduce the inner wall process waste material. Detailed Implementation

[0012] The specific embodiments of the present invention will be further described and illustrated below with reference to the examples. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0013] A forging method for a special extrusion forming H13 extrusion cylinder bushing is analyzed, taking the forging of a Φ922 / φ595*1920mm extrusion cylinder forging blank from a 6.9-ton (Φ790 / Φ830mm) electroslag ingot as an example. The specific forging method is as follows: Step 1) Place the electroslag ingot in the furnace and heat it. First, hold it at 530℃ for 4.5 hours. Then, raise the temperature to 850℃ at a rate of ≤60℃ / h and hold it for 5.0 hours. Next, raise the temperature to 1250℃ at a rate of ≤120℃ / h and hold it for 25 hours. During this period, hold it at 1250℃ for 3 hours. After that, remove it from the furnace and remove the protective plate. Then, return it to the furnace to continue holding it for the required time. After the holding period is over, remove it from the furnace and forge it. Step 2) After heating, the electroslag ingot is sent to the hydraulic press. The upper spherical upsetting plate and the lower platform are used to upset the electroslag ingot axially to H=800 (~Φ1220) mm. The upset ingot is then upset radially to 750 mm on the upper plate and the lower platform. The upset ingot is then rotated 90° and upset radially to 850 mm on the upper plate and the lower platform. The two radial upsettings are at a 90° angle to each other. Then, the ingot is drawn axially to a square of 790° using a 600° anvil, chamfered, and reduced by 40~80 mm. Step 3) The drawn billet is axially upset to H=700 (~Φ1290) mm, and then a Φ350 punch is used to punch a through hole. After punching, a lever is used to further enlarge the hole to Φ465 mm. Step 4) After the hole is enlarged, the blank is drawn to 1950mm using a Φ450 mandrel on an upper flat and lower V anvil. During the drawing process, the two ends are flattened in time to prevent horseshoe or irregular shapes from being formed. Step 5) After the elongated cylindrical billet is stretched, it is enlarged to the final forging size using a frame on the upper and lower flat anvils. After the enlargement is completed and the end face is flattened, it is returned to the furnace for reheating. It is then returned to the 1230℃ heating furnace and held at that temperature for 1.0h before being taken out of the furnace for forging. Step 6) After the reaming is completed, the blank is reamed by 10-15mm on the upper and lower V anvils, finished and shaped, and the end face is flattened to obtain the required extrusion cylinder forging blank size; Step 7) After forging, the billet is sent to an annealing furnace for heat treatment.

[0014] By adopting the above special forging methods and strictly controlling the process production parameters, the produced extruded cylinder forgings have good consistency and better microstructure uniformity than before. At the same time, the yield is greatly improved, the manufacturing cost is reduced, and the production cycle is shortened.

Claims

1. A forging method for an H13 extrusion cylinder bushing for special extrusion molding, characterized in that: The specific forging steps are as follows: Step 1) Place the electroslag ingot in the furnace and heat it. First, hold it at a temperature of 450-550℃, then raise the temperature to 800-900℃ at a rate of ≤60℃ / h and hold it there. Then raise the temperature to 1250-1270℃ at a rate of ≤120℃ / h and hold it there. The holding time is calculated as 3.0-4.0h per 100mm cross-sectional diameter. After holding it at 1250-1270℃ for 3h, remove it from the furnace and remove the protective plate. Then return it to the furnace to continue holding it for the required time. After the holding time is completed, remove it from the furnace and forge it. Step 2) After the electroslag ingot from the furnace in Step 1) is heated, it is sent to the hydraulic press. The upper spherical upsetting plate and the lower platform are used to upset the electroslag ingot along the axial direction. The height after upsetting is 0.5 to 0.6 times the original height. The upset billet is then upset along one radial direction on the upper plate and the lower platform, with a reduction of 35% to 55%. The upset billet is then rotated 90° and upset along another radial direction on the upper plate and the lower platform, with a reduction of 35% to 55%. The two radial upsettings are at a 90° angle to each other. Then, the billet is drawn along the axial direction to a square shape using upper and lower flat anvils, chamfered, and reduced by 40 to 80 mm. The ratio of the length of the drawn billet to the side length of the drawn square is controlled between 1.8 and 2.

4. Step 3) The billet drawn in Step 2) is axially upset to a height-to-diameter ratio of 0.45 to 0.

65. Then, a punch is used to punch a through hole. The diameter of the punch is no more than 1 / 3 of the diameter of the billet after upsetting. After punching, a lever is used to further enlarge the hole. The wall thickness after enlargement is at least 400 mm less than the final extrusion cylinder forging billet wall thickness. Step 4) Using a mandrel 10-20mm smaller than the hole size, the blank after the hole enlargement in Step 3) is drawn out on an upper flat and lower V anvil until it reaches the length of the extrusion cylinder. The two ends are flattened to prevent horseshoe or irregular shapes from forming. The wall thickness of the drawn blank should be at least 200mm less than the final wall thickness of the extrusion cylinder forging blank. Step 5) Use a reamer to enlarge the cylindrical billet from Step 4) on the upper and lower flat anvils to the final size, ensuring uniform wall thickness. Note that the rotation angle of the forging billet should be adjusted in time during the enlargement process to ensure the uniformity of the wall thickness of the forging billet after enlargement. When the reamer is used, the deformation area of ​​the metal is subjected to better stress, making it less prone to cracking. The metal has good fluidity, and the difference in wall thickness is easy to control. After the enlargement is completed and the end face is flattened, return it to the furnace for reheating. Return it to the 1200-1250℃ heating furnace and hold it for 1.0-2.0 hours before taking it out of the furnace for forging. Step 6) After the blank in Step 5) is enlarged, the blank is 10-15mm smaller on the upper and lower V anvils, finished and shaped, and the end face is flattened to obtain the required extrusion cylinder forging blank size; Step 7) Send the billet after forging in Step 6) to an annealing furnace for heat treatment.

2. The forging method for an H13 extrusion cylinder bushing for special extrusion molding according to claim 1, characterized in that: In step 1), after holding at 1250-1270℃ for 3 hours, the ingot is removed from the furnace and the protective plate is removed. Then it is returned to the furnace to continue to make up for the remaining holding time. The total holding time required for the electroslag ingot is calculated based on 3.0-4.0 hours per 100mm cross section. Then, 3.5 hours is subtracted to get the remaining holding time. After the holding is completed, the ingot is removed from the furnace for forging. This reduces the auxiliary time such as removing the protective plate during the main deformation process, which is conducive to the compaction and welding during the deformation process.

3. The forging method for an H13 extrusion cylinder bushing for special extrusion molding according to claim 1, characterized in that: In step 5), after the hole is enlarged and the end face is flattened, the furnace is returned to the furnace for reheating. The furnace is heated to 1200-1250℃ and held for 1.0-2.0 hours before being taken out of the furnace for forging.