Production method of w-containing high-mo hot work die steel

Abstract

The application belongs to the technical field of hot work die steel production, and proposes a production method of W-containing high-Mo hot work die steel and a forging-time return-furnace auxiliary equipment, the W-containing high-Mo hot work die steel contains the following components in percentage by mass: C 0.35%, Mo 2.50%, Cr 5.0%, V 0.40%, W 0.75%, Si 0.20%, Mn 0.25%, and the balance is Fe; the specific production steps include electric arc furnace smelting, secondary refining, gas protection casting, electric-shaft ingot remelting, pre-forging heating, forging-time return-furnace, and post-forging heat treatment, and the forging-time return-furnace auxiliary equipment of the W-containing high-Mo hot work die steel is used for removing the oxide skin in the three-up-three-down forging process. The application is beneficial to improving the performance of the product in terms of thermal fatigue cracking, thermal impact cracking, thermal wear, and plastic deformation, is beneficial to producing the hot work die steel used for precision molds, and is beneficial to improving the three-up-three-down forging efficiency and production safety.

Description

Technical Field

[0001] This invention belongs to the field of hot work die steel production technology, and particularly relates to a production method of W-containing high Mo hot work die steel. Background Technology

[0002] Hot work die steel is a die material that withstands high temperatures, high pressures, alternating hot and cold impacts, and frictional wear. It is mainly used for processing hot metals, such as dies for forging, extrusion, and die casting. In recent years, the Chinese automotive market has seen over a hundred new car models added annually. Since most automotive parts are manufactured using molds, the annual value of newly developed molds alone exceeds 10 billion yuan. Therefore, improving the quality and lifespan of mold manufacturing is crucial to the quality of automotive products and the development of the automotive industry, yielding significant economic and social benefits.

[0003] 1.2344 hot work die steel is a type of hot work die steel under the German DIN standard. While possessing good toughness and resistance to high-temperature fatigue, and suitable for demanding precision hot work die applications, its silicon content is typically 0.80%-1.20%, molybdenum 1.20%-1.50%, vanadium 0.90%-1.10%, and chromium 4.80%-5.50%, and it does not contain tungsten. By adjusting the raw material ratios and processes, new hot work die steels can be obtained, exhibiting even better performance in toughness, thermal fatigue resistance, and tempering resistance. Summary of the Invention

[0004] This invention addresses the technical problems existing in the aforementioned hot work die steel by proposing a production method for W- and Mo-rich hot work die steel. This method enables forgings to possess excellent resistance to thermal fatigue cracking, thermal shock cracking, thermal wear, and plastic deformation, which is beneficial for producing hot work die steel for precision molds and also helps improve the efficiency and safety of three-upsetting and three-drawing forging.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows: A method for producing W-containing high-Mo hot work die steel, wherein the W-containing high-Mo hot work die steel comprises, by mass percentage: C 0.35%, Mo 2.50%, Cr 5.0%, V 0.40%, W 0.75%, Si 0.20%, Mn 0.25%, with the balance being Fe; and includes the following specific production steps:

[0006] S1, electric arc furnace smelting;

[0007] S2, Ladle refining: The molten steel smelted in S1 enters the refining furnace, alloys are added in batches, and after smelting for a period of time, it is transferred to a vacuum furnace for degassing.

[0008] S3, Gas-protected casting: The molten steel refined by S2 is cast into a steel billet using a die casting process, and argon gas is introduced into the cavity of the die casting process for protection.

[0009] S4. Electroslag ingot remelting: An electroslag furnace with argon protection is used. The steel billet in S3 is used as a consumable electrode. The consumable electrode is remelted in the molten slag pool. The remelted steel flows into a water-cooled crystallizer and solidifies into a dense steel ingot with a size of φ600mm×(2600~4000)mm.

[0010] S5. Pre-forging heating: The S4 steel ingot is pre-forged using a three-stage heating curve process until the initial forging temperature is 1180℃–1200℃.

[0011] S6. During forging, the steel ingot is reheated in the furnace and then forged again. A 4000t upsetting press is used to upset and draw the steel ingot using a three-upsetting and three-drawing method. Auxiliary equipment is used to remove the oxide scale on the surface of the forging during each upsetting and drawing. After the first upsetting and drawing, the steel ingot is reheated to 1100℃ and held for 1.5~3 hours for high-temperature diffusion. After the second upsetting and drawing, the steel ingot is reheated to 1100℃ and held for 1.5~2 hours for high-temperature diffusion. The final forging temperature is 850℃–900℃. The total ratio of the three forgings is 6~8.

[0012] S7. Post-forging heat treatment.

[0013] As a preferred option, the three-stage heating curve in S5 includes: heating at 60℃ / h to 600℃ and holding for 1~1.5h to eliminate residual stress at room temperature in the billet and prevent cracks from forming during subsequent rapid heating; then heating at 70~80℃ / h to 900℃ and holding for 1.5~2h to ensure uniform internal temperature of the billet and alleviate the temperature gradient caused by differences in the thermal conductivity of alloying elements; and finally heating at 100℃ / h to the target temperature of 1150℃–1200℃ and holding for 2~3h to bring the billet to the plastic state required for initial forging, slightly promote the diffusion of alloying elements, and provide favorable conditions for forging.

[0014] As a preferred option, the specific steps of S7 include: using double normalizing to spray water mist after exiting the furnace at 1180℃, cooling the billet to 680~720℃; transferring the billet cooled to the target range to an isothermal furnace for isothermal spheroidization, with the isothermal furnace temperature controlled at 20℃–50℃ below the Ac1 line (828℃), i.e., 778~808℃, holding for 5~7 hours, and after holding, furnace cooling to 500~530℃, and then air cooling after exiting the furnace.

[0015] A forging remelting auxiliary device for high-Mo hot work die steel containing W includes a hydraulic clamping device and a hook. A scissor lift is provided below the hook. The scissor lift has a vertical mode and a horizontal mode. A vertical attachment assembly for engaging with the hook in the vertical mode is provided at the top of the scissor lift. A horizontal attachment assembly for engaging with the hook in the horizontal mode is provided in the middle of the scissor lift. A chain drive mechanism that opens and closes with the scissor lift's opening and closing action is provided on the side of the scissor lift. The transmission surface of the chain drive mechanism in the vertical mode is used to remove oxide scale from the forging during the drawing forging process, and the transmission surface of the chain drive mechanism in the horizontal mode is used to remove oxide scale from the forging during the upsetting forging process.

[0016] Preferably, the inner side of the scissor lifter is provided with a pair of friction transmission mechanisms for frictional transmission with the surface of the forging. A bevel gear transmission mechanism is provided between the friction transmission mechanism and the chain transmission mechanism. The bevel gear transmission mechanism converts the axial relative motion between the friction transmission mechanism and the forging into the circumferential relative motion between the chain transmission mechanism and the surface of the forging.

[0017] Preferably, the chain drive mechanism includes a central sprocket group and two opening and closing sprocket groups. The central sprocket group includes four coaxially distributed central sprockets, and the opening and closing sprocket groups include two coaxially distributed opening and closing sprockets. The two opening and closing sprocket groups are axially staggered and are connected to the central sprocket by a chain. Both the opening and closing sprockets and the central sprockets include a number of chain teeth and tooth grooves.

[0018] Preferably, a fixed sprocket group is provided on one side of the opening and closing sprocket group. Each fixed sprocket group includes two fixed sprockets, and a tensioning assembly is provided between the fixed sprockets. The tensioning assembly includes a tension spring plate, and the tension spring plate includes a C-shaped segment. One end of the C-shaped segment is provided with a positioning hole, which cooperates with a positioning shaft provided on the end face of the fixed sprocket. The other end of the C-shaped segment is provided with a braking segment, which bends and extends outward toward the outside of the fixed sprocket group. The end of the braking segment is provided with a connecting hole, and a tensioning shaft is provided in the connecting hole. A tensioning roller is provided on the tensioning shaft, and the roller surface of the tensioning roller contacts and cooperates with the transmission surface of the chain.

[0019] Preferably, the friction transmission mechanism includes a contact wheel with a groove on its surface, a transmission wheel above the contact wheel with an annular protrusion on its surface, and the transmission wheel's surface and annular protrusion respectively frictionally engaging with the contact wheel's surface and groove. A rotating shaft is located at the center of the transmission wheel, with a bearing seat at one end of the shaft, which is mounted on a transmission arm. A fixed shaft for mounting the contact wheel is located on the transmission arm, and the other end of the rotating shaft is located inside a transmission housing. The bevel gear transmission mechanism includes a small bevel gear connected to the rotating shaft and a large bevel gear rotating coaxially with the chain transmission mechanism.

[0020] Preferably, the scissor lift includes a pair of left connecting arms and a pair of right connecting arms. The top ends of the left and right connecting arms are provided with top hinge pins. The bottom ends of the left and right connecting arms are respectively provided with left and right hinge pins. A pair of left hook arms and a pair of right hook arms are respectively mounted on the left and right hinge pins. A middle hinge pin, located on the same vertical line as the top hinge pins, is provided between the left and right hook arms. Each left and right hook arm has a reinforcing shaft at its respective turning point. A positioning cylinder is mounted on the reinforcing shaft. A positioning plate is mounted on the cylinder wall of the positioning cylinder. The positioning plate engages with slots on the left and right hook arms. The positioning plate is used to limit the minimum opening diameter of the scissor lift.

[0021] Preferably, the horizontal hanging assembly includes a U-shaped plate with two pairs of spaced guide holes that correspond to the left and right hinge shafts respectively, and the ends of the U-shaped plate are provided with horizontal lifting lugs; the vertical hanging assembly includes a lever head that rotates with the top hinge shaft, the top of the lever head is provided with a connecting bar, and the top of the connecting bar is provided with a vertical lifting lug.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0023] 1. The production method of W-containing high-Mo hot work die steel provided by the present invention, from the perspective of raw material composition, reduces the silicon ratio while increasing the molybdenum and tungsten ratio, which is beneficial to improving the hardenability, tempering resistance, hot cracking resistance and toughness of the product, and is beneficial to improving the application performance of the product in precision molds; from the perspective of process, the forging ratio is increased, and the side upsetting forging and drawing forging core are used to make the core structure more compact, improving the core quality of the forging. In addition, the high temperature diffusion during forging, timely removal of oxide scale, and double normalizing at 1180°C after forging and water mist spraying are beneficial to refining the grains and increasing the core hardness, thereby helping to obtain high-quality hot work die steel.

[0024] 2. The forging remelting auxiliary equipment for high-Mo hot work die steel containing W provided by this invention uses a scissor lifter. This scissor lifter can not only be used for lifting and transferring forgings, but also, through a chain drive mechanism in conjunction with the scissor lifter, allows workers to remotely remove oxide scale from forgings during the three-upsetting and three-drawing operations. This reduces the time and frequency of close-range manual operations, improving production safety and increasing the efficiency of multiple remelting processes. This invention improves the product's resistance to thermal fatigue cracking, thermal shock cracking, thermal wear, and plastic deformation, facilitates the production of hot work die steel for precision molds, and enhances the efficiency and safety of three-upsetting and three-drawing forging. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Microstructure diagram of W-containing high-Mo hot work die steel provided for the embodiments;

[0027] Figure 2 Working diagram of auxiliary equipment for forging and remelting of hot work die steel containing W and high Mo;

[0028] Figure 3 A three-dimensional view of the auxiliary equipment for remelting hot work die steel containing W and high Mo during forging in vertical mode;

[0029] Figure 4 A side view of the auxiliary equipment for forging and remelting of hot work die steel containing W and high Mo in vertical mode;

[0030] Figure 5 for Figure 4 A cross-sectional view of the auxiliary equipment for forging and remelting of hot work die steel with high W and Mo content in the HH direction;

[0031] Figure 6 for Figure 5 Enlarged schematic diagram of the auxiliary equipment for forging and remelting of hot work die steel with high W and Mo content at point A;

[0032] Figure 7 An exploded view of the fixed sprocket assembly and tensioning components;

[0033] Figure 8 This is a partial schematic diagram of the chain in a chain drive mechanism;

[0034] Figure 9 A front view of the auxiliary equipment for forging and remelting of hot work die steel containing W and high Mo in a transverse orientation.

[0035] Figure 10 A three-dimensional view of the auxiliary equipment for remelting hot work die steel containing W and high Mo during forging in a transverse configuration;

[0036] In the above figures: 1. Hydraulic clamping device; 2. Hook; 3. Scissor lift; 31. Left connecting arm; 32. Right connecting arm; 33. Top hinge shaft; 34. Left hinge shaft; 35. Right hinge shaft; 36. Left hook arm; 37. Right hook arm; 38. Middle hinge shaft; 39. Reinforcing shaft; 310. Positioning shaft sleeve; 311. Positioning plate; 312. Slot; 4. Vertical hanging assembly; 5. Horizontal hanging assembly; 51. U-shaped plate; 52. Guide hole; 53. Horizontal lifting lug; 6. Chain drive mechanism; 631. Chain link; 6311. Chain groove; 6312. Shaft hole; 632. Inner chain. 633. Outer chain buckle; 634. Pin; 7. Fixed sprocket assembly; 8. Tensioning assembly; 81. Tensioning spring plate; 811. C-section; 812. Positioning hole; 813. Braking section; 814. Connecting hole; 82. Positioning shaft; 83. Tensioning shaft; 84. Tensioning roller; 9. Friction transmission mechanism; 91. Contact wheel; 92. Wheel groove; 93. Transmission wheel; 94. Ring protrusion; 95. Rotating shaft; 96. Bearing seat; 97. Transmission arm; 98. Fixed shaft; 99. Transmission box; 10. Bevel gear transmission mechanism; 101. Small bevel gear; 102. Bevel gear; 11. Forging. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other. For ease of description, the terms "left" and "right" will appear below to indicate a different version from the attached drawings. Figure 5 The left and right directions are consistent and do not limit the structure.

[0038] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0039] Examples, such as Figure 1As shown, the W-containing high-Mo hot work die steel provided by this invention comprises the following components by mass percentage: C 0.35%, Mo 2.50%, Cr 5.0%, V 0.40%, W 0.75%, Si 0.20%, Mn 0.25%, with the balance being Fe. The hot work die steel of this invention adopts a low-silicon, high-molybdenum alloying ratio. From the perspective of raw material ratio, reducing silicon has the advantages of: (1) reducing segregation; (2) refining austenite crystals; (3) improving plasticity and toughness; (4) improving resistance to hot cracking. Increasing the molybdenum ratio has the advantages of: (1) improving hardenability; (2) improving resistance to tempering; (3) improving resistance to hot cracking; (4) improving toughness; (5) refining eutectic carbides and uniformly distributing carbides. Increasing the tungsten ratio has the advantages of: (1) integration into the matrix, strong carbon... 1) Carbide-forming elements (WC) refine grains and improve strength, tempering stability, thermal stability, and toughness; 2) Due to the high hardness of WC, wear resistance is increased and secondary precipitation strengthening is possible; 3) Quenching temperature is increased, and tempering stability is improved; 4) Martensite stability is improved, and hardenability is greatly improved; 5) The hot strength of pearlitic steel is improved, and the quenching temperature is increased; 6) Due to the formation of carbides, the tendency for intergranular corrosion is reduced. Fe3W2 and Fe2W are both very stable compounds, which improve strength and thermal stability.

[0040] The method for producing high-Mo hot work die steel containing W provided by this invention includes the following specific production steps:

[0041] S1, electric arc furnace smelting;

[0042] S2, Ladle refining: The molten steel smelted in S1 enters the refining furnace, alloys are added in batches, and after smelting for a period of time, it is transferred to a vacuum furnace for degassing.

[0043] S3, Gas-protected casting: The molten steel refined by S2 is cast into a steel billet using a die casting process, and argon gas is introduced into the cavity of the die casting process for protection.

[0044] S4. Electroslag ingot remelting: An electroslag furnace with argon protection is used. The steel billet in S3 is used as a consumable electrode. The consumable electrode is remelted in the molten slag pool. The remelted steel flows into a water-cooled crystallizer and solidifies into a dense steel ingot with a size of φ600mm×(2600~4000)mm.

[0045] S5. Pre-forging heating: A three-stage heating curve process is used to pre-heat the S4 steel ingot until the initial forging temperature reaches 1180℃–1200℃. The three-stage heating curve includes: heating at 60℃ / h to 600℃ and holding for 1~1.5h to eliminate residual stress at room temperature and avoid cracking caused by subsequent rapid heating; heating at 70~80℃ / h to 900℃ and holding for 1.5~2h to make the internal temperature of the steel ingot uniform and alleviate the temperature gradient caused by the difference in thermal conductivity of alloying elements; finally, heating at 100℃ / h to the target temperature of 1150℃–1200℃ and holding for 2~3h to make the steel ingot reach the plastic state required for initial forging, slightly promote the diffusion of alloying elements, and provide good conditions for forging.

[0046] S6. During forging, the steel ingot is reheated in the furnace and then forged again. A 4000t upsetting press is used to upset and draw the steel ingot using a three-upsetting and three-drawing method. Auxiliary equipment is used to remove the oxide scale on the surface of the forging during each upsetting and drawing. After the first upsetting and drawing, the steel ingot is reheated to 1100℃ and held for 1.5~3 hours for high-temperature diffusion. After the second upsetting and drawing, the steel ingot is reheated to 1100℃ and held for 1.5~2 hours for high-temperature diffusion. The final forging temperature is 850℃–900℃. The total ratio of the three forgings is 6~8.

[0047] S7. Post-forging heat treatment: Double normalizing at 1180℃ followed by water mist spraying after billet is cooled to 680~720℃. The billet cooled to the target range is then transferred to an isothermal furnace for isothermal spheroidization. The isothermal furnace temperature is controlled at 20℃–50℃ below the Ac1 line (828℃), i.e., 778~808℃. The temperature is held for 5~7 hours. After holding, the temperature is furnace cooled to 500~530℃, and then air-cooled after being removed from the furnace.

[0048] The production method of W-containing high-Mo hot work die steel provided by this invention adopts a three-upsetting and three-drawing process during forging to increase the forging ratio. Side upsetting and drawing forging are used to make the core structure of the module more compact and improve the core quality. S7 adopts double normalizing forging at 1180℃ and water mist spraying after exiting the furnace to increase the cooling rate, refine the grains, and increase the core hardness. By reheating (high-temperature diffusion) during forging, dendrite segregation is reduced or eliminated, and the distribution of chemical composition is improved to improve the hot working performance of the steel ingot and ultimately improve the quality of the forging. The forging adopts double normalizing to refine the grains, homogenize the structure, eliminate internal stress, and improve defects such as Widmanstätten, coarse grains, and overheating defects and banded structures. The present invention can achieve a core hardness of 51~53HRC through heat treatment, and has excellent thermal fatigue resistance under the same experimental conditions; the tempering stability and thermal stability are even better. For example, when the tempering temperature exceeds 650℃, the hardness still remains above 45HRC, and after tempering at 700℃ for 24 hours, the hardness is still 28~30HRC.

[0049] like Figure 2 ~as Figure 10As shown, an auxiliary device for remelting hot work die steel containing W and high Mo during forging includes a hydraulic clamping device 1 and a hook 2. A scissor lifter 3 is provided below the hook 2. The scissor lifter 3 includes a vertical mode and a horizontal mode. The top of the scissor lifter 3 is provided with a vertical hook assembly 4 for cooperating with the hook 2 in the vertical mode. The middle of the scissor lifter 3 is provided with a horizontal hook assembly 5 for cooperating with the hook 2 in the horizontal mode. The side of the scissor lifter 3 is provided with a chain drive mechanism 6 that opens and closes together with its opening and closing action. The transmission surface of the chain drive mechanism 6 in the vertical mode is used to remove oxide scale from the forging 11 during the drawing forging process. The transmission surface of the chain drive mechanism 6 in the horizontal mode is used to remove oxide scale from the forging 11 during the upsetting forging process. The scissor lift 3 is a prior art high-strength structural unit in the forging workshop. Specifically, it includes a pair of left connecting arms 31 and a pair of right connecting arms 32. Top hinge pins 33 are provided at the top of the left and right connecting arms 31 and 32, respectively. Left hinge pins 34 and 35 are provided at the bottom of the left and right connecting arms 31 and 32, respectively. A pair of left hook arms 36 and a pair of right hook arms 37 are provided on the left and right hinge pins 34 and 35, respectively. A middle hinge pin 38, located on the same vertical line as the top hinge pins 33, is provided between the left and right hook arms 36 and 37. Reinforcing shafts 39 are provided at the respective turning points of the left and right hook arms 36 and 37. The hydraulic clamping device 1 is powered by the hydraulic trolley in the forging workshop and is located at the front end of the hydraulic trolley for adjusting the orientation of the forging 11. The hook 2 is powered by the overhead crane in the forging workshop and is used to directly engage with the scissor lift 3.

[0050] Specifically, the most basic mode of the scissor lift 3 is the vertical mode. The basic function of this mode is to lift and transfer the forging 11. For example, with the help of the crane, the hook 2 lifts the scissor lift 3 and moves it to the position of the forging 11. The scissor lift 3 is gradually lowered so that the left hook arm 36 and the right hook arm 37 open around the central hinge 38 until the ends of the left hook arm 36 and the right hook arm 37 are stuck under the forging 11. If the scissor lift 3 is raised, the left hook arm 36 and the right hook arm 37 will make a linkage movement and effectively clamp the forging 11. The forging 11 can be transferred by remote control of the crane.

[0051] Based on this, the present invention employs a chain drive mechanism 6 in conjunction with the scissor lift 3. The transmission surface of the chain drive mechanism 6 can directly contact the oxide scale. In particular, the three upsetting and three drawing operations are repetitive and the forging time is relatively long. Using mechanical removal of oxide scale can effectively reduce the time and frequency of close-range manual operation. At the same time, the scissor lift 3 adopts two specific modes. By switching the working mode, it can be effectively matched with upsetting and drawing forging. In particular, the chain in the vertical mode has a larger contact surface with the forging 11, while the chain in the horizontal mode is folded and extended by the scissor lift 3, allowing the chain to extend to the vicinity of the forging press, which is conducive to contacting the upsetting forging 11. It is highly practical and improves the production efficiency of multiple remelting of products while improving production safety.

[0052] To improve the cleaning efficiency of the forging 11 surface in vertical mode, the scissor lifter 3 provided by the present invention is provided with a pair of friction transmission mechanisms 9 for friction transmission with the surface of the forging 11. A bevel gear transmission mechanism 10 is provided between the friction transmission mechanism 9 and the chain transmission mechanism 6. The bevel gear transmission mechanism 10 converts the axial relative motion between the friction transmission mechanism 9 and the forging 11 into the circumferential relative motion between the chain transmission mechanism 6 and the surface of the forging 11. In vertical mode, the scissor lift 3 clamps the elongated forging 11. The transmission surface of the chain drive mechanism 6 rests on the surface of the forging 11, while the forging 11 remains fixed by the hydraulic clamping device 1. Therefore, the position of the forging 11 is not affected by the movement of the scissor lift 3. By controlling the trolley to move the scissor lift 3 along the length of the forging 11, the friction drive mechanism 9 rotates relative to the surface of the forging 11. The two friction drive mechanisms 9 contact the forging 11 from symmetrical directions, which ensures the balance and safety of the scissor lift 3 and increases the friction drive surface, allowing the friction drive mechanism 9 to transmit the power to the bevel gear drive mechanism 10. The bevel gear drive mechanism 10 switches the transmission direction, thereby providing the chain drive mechanism 6 with the driving force to move. Under the traction of the scissor lift 3 and the drive of the transmission force, the chain drive mechanism 6 can effectively remove the oxide scale from the surface of the forging 11. At the same time, when the left hook arm 36 and the right hook arm 37 touch the surface of the forging 11, they can also remove some of the oxide scale.

[0053] Furthermore, the chain drive mechanism 6 provided by the present invention includes a central sprocket group and two opening and closing sprocket groups. The rotation center of the central sprocket group is the central hinge shaft 38, and the rotation centers of the two opening and closing sprocket groups are the left hinge shaft and the right hinge shaft, respectively. The central sprocket group includes four coaxially distributed central sprockets, and the opening and closing sprocket groups include two coaxially distributed opening and closing sprockets. The two opening and closing sprocket groups are axially staggered and are connected to the central sprockets by a chain. Both the opening and closing sprockets and the central sprockets include a number of chain teeth and tooth grooves. The central sprocket assembly and the opening / closing sprocket assembly work together to allow the chain to open a larger transmission surface, especially so that the span of the two chains in the vertical mode can cover the upper half of the forging 11, and the two chains in the horizontal mode can also obtain a larger contact surface with the forging 11; in addition, the opening / closing sprocket assembly adopts a double sprocket side by side design, which can further increase the effective transmission surface of the chain, thereby improving the removal efficiency of oxide scale on the surface of the forging 11, and thus shortening the adjustment time interval between the upsetting and drawing postures of the forging 11.

[0054] To improve the working efficiency of the chain, the chain provided by the present invention includes a chain link 631, an inner chain buckle 632, an outer chain buckle 633, and a pin 634. The chain link 631 has a V-shaped structure and a chain groove 6311 is provided on the side facing the sprocket. The chain groove 6311 simultaneously engages with two chain teeth at the same axial position. The adjacent parts of two adjacent chain links 631 engage with two tooth grooves at the same axial position. The inner chain buckle 632 and the outer chain buckle 633 are both parallelograms, and the two opposite corners of the parallelograms are used to connect the pin 634. The top and bottom ends of the chain link 631 are respectively provided with a shaft hole 6312 for cooperating with the pin 634. The inner link 632 connects adjacent links 631, while the outer link 633 connects adjacent inner links 632, thus creating a continuous transmission surface that allows for sprocket engagement. After adjacent links 631 are connected, their grooves 6311 engage with the teeth, and adjacent portions of the links 631 form a meshing structure that mates with the tooth grooves, ensuring the continuity of the transmission surface. Specifically, the V-shaped surface formed between adjacent links 631 can constitute a bucket-shaped structure for removing oxide scale. For scale residue trapped between links 631, a tilting surface is formed as the links 631 change direction due to the curvature of the sprocket. Furthermore, the tail of the chain link 631 produces a small-amplitude scraping action against the opposite wall surface, which can promote the discharge of shavings and avoid the formation of large slag deposits. The inner chain buckle 632 and outer chain buckle 633 provided by the present invention adopt a special parallelogram design, which provides an effective rotation node by utilizing the hinge center at the diagonal position. This not only meets the curve transition requirements of the chain, sprocket and forging 11 surface, but also utilizes its diagonal characteristics to obtain several pairs of small-height sharp corners on the transmission surface, mainly appearing on the curvature surface of the sprocket. This is beneficial to improving the peeling efficiency of oxide scale on the surface of forging 11, especially for the peeling efficiency of the chain on the upset forging 11 in the transverse mode.

[0055] Since the two hook arms of the scissor lift 3 are folded in the lateral mode, i.e., the opening and closing angle is minimal and the forging 11 is not clamped, in order to improve the tension performance of the chain during the process of cleaning the oxide scale on the upsetting forging 11, this invention provides a tensioning component 8 to ensure the working performance of the chain. Specifically, a fixed sprocket group 7 is provided on one side of the opening and closing sprocket group. One side of the fixed sprocket group 7 is located close to the scissor lift 3, while the other side of the fixed sprocket group 7 is located away from the scissor lift 3. This position takes into full account the spatial transmission position of the two opening and closing sprocket groups and the central sprocket group. Each fixed sprocket group 7 includes two fixed sprockets, and a tensioning component 8 is provided between the fixed sprockets. The tensioning component 8 includes a tensioning spring plate 81. The tension spring plate 81 includes a C-shaped section 811. One end of the C-shaped section 811 has a positioning hole 812, which engages with a positioning shaft 82 located on the end face of the fixed sprocket. The other end of the C-shaped section 811 has a braking section 813, which bends outward toward the outside of the fixed sprocket assembly 7 and has a connecting hole 814 at its end. A tensioning shaft is installed in the connecting hole 814, and a tensioning roller 84 is installed on the tensioning shaft. The roller surface of the tensioning roller 84 contacts the transmission surface of the chain. Due to the staggered distribution of the two chains of the chain drive mechanism 6, there is a wheelbase in the axial direction. To prevent oxide residue from getting stuck between the sprocket and the hook arm, this invention integrates the opening and closing sprocket assembly while also arranging the fixed sprocket assembly 7. The paired fixed sprockets of the fixed sprocket assembly 7 can both prevent oxide residue from getting stuck on the equipment and provide an installation and support foundation for the tensioning assembly 8. The fixed sprocket is connected to the reinforcing shaft 39 by a key connection. The reinforcing shaft 39 does not rotate, and the fixed sprocket does not rotate either. The range of shaft movement of the two fixed sprockets is used to cooperate with the C-shaped section 811 of the tension spring plate 81. In its natural state, the C-shaped section 811 can drive the tension roller 84 to press against the transmission surface of the chain. If the forging 11 is clamped in the clamping mouth of the scissor lift 3, the curved surface of the forging 11 can open the chain and transmit the pressure to the tension roller 84 and the braking section 813. When the braking section 813 deforms, the C-shaped opening of the C-shaped section 811 also changes, thereby obtaining a certain elastic tension. This allows the chain to maintain a certain tension as the clamping mouth of the scissor lift 3 changes, avoiding the problem of chain derailment in the lateral mode, which would directly affect the cleaning operation on the surface of the forging 11.

[0056] To improve the practicality of the friction transmission mechanism 9, the friction transmission mechanism 9 provided by the present invention does not require additional power, that is, no additional power is required to install on the scissor lift 3. Specifically, the friction transmission mechanism 9 provided by the present invention includes a contact wheel 91, a groove 92 is provided on the wheel surface of the contact wheel 91, a transmission wheel 93 is provided above the contact wheel 91, an annular protrusion 94 is provided on the wheel surface of the transmission wheel 93, the wheel surface and the annular protrusion 94 of the transmission wheel 93 respectively frictionally engage with the wheel surface and the groove 92 of the contact wheel 91, a rotating shaft 95 is provided at the center of the transmission wheel 93, a bearing seat 96 is provided at one end of the rotating shaft 95, the bearing seat 96 is provided on the transmission arm 97, the forward and backward swing of the transmission arm 97 is limited by the internal space of the scissor lift and will not swing significantly, a fixed shaft 98 for mounting the contact wheel 91 is provided on the transmission arm 97, the other end of the rotating shaft 95 is provided in the transmission box 99, and the bevel gear transmission mechanism 10 includes a small bevel gear 101 connected to the rotating shaft 95 and a large bevel gear that rotates coaxially with the chain transmission mechanism 6. Two contact wheels 91 are effectively and reliably mounted on the transmission arm 97 via a fixed shaft 98 and locking nuts at both ends of the fixed shaft 98. The contact wheels 91 are used to contact the surface of the forging 11. The wheel surface adopts a design of wheel groove 92, which on the one hand avoids irregular surface positions on the forging 11 and reduces the frequency of bumps. On the other hand, it can cooperate with the transmission wheel 93 to add a transmission surface with wheel groove 92 and ring protrusion 94 as friction supplement on the basis of wheel surface friction, thereby improving the stability and reliability of providing transmission force to the rotating shaft 95.

[0057] Furthermore, the rotating shaft 95 synchronously transmits power to the small bevel gear 101, which then transmits it to the large bevel gear 102 to complete the switching of power direction. The transmission box 99 is designed with cast walls that mate with the large bevel gear 102 and the small bevel gear 101, as well as a support bearing that mates with the intermediate hinge shaft 38, to ensure the transmission quality between the large bevel gear 102 and the small bevel gear 101. The friction transmission mechanism 9 and the bevel gear transmission mechanism 10 provided by this invention cleverly utilize the spatial characteristics of the scissor lift 3, leveraging the structural strength advantages of the scissor lift 3 while achieving a rational power transmission.

[0058] To improve the stability and balance of the scissor lift 3 in lateral mode, the reinforcing shaft 39 provided by the present invention is provided with a positioning shaft cylinder 310, and a positioning plate 311 is provided on the cylinder wall of the positioning shaft cylinder 310. The positioning plate 311 cooperates with the slots 312 provided on the left hook arm 36 and the right hook arm 37. The positioning plate 311 is used to limit the minimum opening and closing diameter of the scissor lift 3. The positioning cylinder 310, through the relationship between the positioning plate 311 and the slot 312, can remain relatively stationary with the two hook arms. The interior of the positioning cylinder 310 is connected to the reinforcing shaft 39 by a key to ensure the non-rotational performance of the reinforcing shaft 39. With the cooperation of the positioning plate 311 and the slot 312, an effective limit is provided for the closing action of the left hook arm 36 and the right hook arm 37. When the scissor lift 3 switches from vertical mode to horizontal mode, the two hook arms will naturally close due to the characteristics of gravity distribution. For the hook arm that originally has the function of clamping the forging 11, the limit provided can prevent the opening and closing sprocket sets from colliding, and also ensure that the two opening and closing sprocket sets have a certain combined opening surface, thereby improving its cleaning efficiency of the surface of the forging 11 during this period.

[0059] To improve the safety of the scissor lift 3 in different modes, the lateral attachment assembly 5 provided by the present invention includes a U-shaped plate 51. The U-shaped plate 51 is provided with two pairs of spaced guide holes 52, which correspond to the left hinge shaft 34 and the right hinge shaft 35 respectively. The U-shaped plate 51 also has a stepped angle at the transition position between itself and the left hinge shaft 34 and the right hinge shaft 35, which helps to improve the safety of the left hinge shaft 34 and the right hinge shaft 35 reaching the automatic balance position. The end of the U-shaped plate 51 is provided with a lateral lifting lug 53. The guide holes 52 provide an effective folding and unfolding stroke for the left hinge shaft 34 and the right hinge shaft 35. Especially in the lateral mode, it can keep the two hinge shafts in a balanced position, which helps to improve the controllability of the position of the scissor lift 3 as it moves with the trolley.

[0060] Furthermore, the vertical mounting assembly 4 provided by the present invention includes a lever head that rotatably engages with the top hinge shaft 33. A connecting bar is provided at the top of the lever head, and a vertical lifting lug is provided at the top of the connecting bar. The lever head is used to flexibly rotate and move with the top hinge shaft 33. When the scissor lift 3 is switched to horizontal mode, the vertical mounting assembly 4 automatically hangs down, balancing the entire scissor lift 3. To improve the balancing effect of the vertical mounting assembly 4, the present invention provides angular grooves on both sides of the connecting rod. Counterweights are installed in the angular grooves and fixedly connected to the angular grooves with bolts, improving the overall balance performance of the equipment. Based on this, the present invention provides two sets of chain drive mechanisms 6, distributed on the front and rear sides of the scissor lift 3. If a single set of chain drive mechanisms 6 is used, a counterweight bar can be welded to the end of the top hinge shaft 33 to achieve a balancing effect.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for producing high-Mo hot work die steel containing W, characterized in that, The W-containing high-Mo hot work die steel comprises, by mass percentage: C 0.35%, Mo 2.50%, Cr 5.0%, V 0.40%, W 0.75%, Si 0.20%, Mn 0.25%, with the balance being Fe; The specific production steps include the following: S1, electric arc furnace smelting; S2, Ladle refining: The molten steel smelted in S1 enters the refining furnace, alloys are added in batches, and after smelting for a period of time, it is transferred to a vacuum furnace for degassing. S3, Gas-protected casting: The molten steel refined by S2 is cast into a steel billet using a die casting process, and argon gas is introduced into the cavity of the die casting process for protection. S4. Electroslag ingot remelting: An electroslag furnace with argon protection is used. The steel billet in S3 is used as a consumable electrode. The consumable electrode is remelted in the molten slag pool. The remelted steel flows into a water-cooled crystallizer and solidifies into a dense steel ingot with a size of φ600mm×(2600~4000)mm. S5. Pre-forging heating: The S4 steel ingot is pre-forged using a three-stage heating curve process until the initial forging temperature is 1180℃-1200℃. S6. During forging, the steel ingot is reheated in the furnace. The forging blank is then prepared using a 4000t upsetting press employing a three-upsetting and three-drawing method. Auxiliary equipment is used to remove oxide scale from the forging surface during each upsetting and drawing process. After the first upsetting and drawing, the ingot is reheated to 1100℃ and held for 1.5-3 hours for high-temperature diffusion. After the second upsetting and drawing, the ingot is reheated to 1100℃ and held for 1.5-2 hours for high-temperature diffusion. The final forging temperature is 850℃-900℃. The total forging ratio is 6-8. The auxiliary equipment is a reheating auxiliary device, which includes a hydraulic clamping device and a hook. A hook is positioned below the hook. The device is equipped with a scissor lift, which includes a vertical mode and a horizontal mode. The top of the scissor lift is provided with a vertical hook assembly for engaging with a hook in the vertical mode, and the middle of the scissor lift is provided with a horizontal hook assembly for engaging with a hook in the horizontal mode. The side of the scissor lift is provided with a chain drive mechanism that opens and closes together with its opening and closing action. The drive surface of the chain drive mechanism in the vertical mode is used to remove oxide scale from the forgings during the drawing forging process, and the drive surface of the chain drive mechanism in the horizontal mode is used to remove oxide scale from the forgings during the upsetting forging process. S7. Post-forging heat treatment.

2. The method for producing W-containing high-Mo hot work die steel according to claim 1, characterized in that, The three-stage heating curve in S5 includes: heating at 60℃ / h to 600℃ and holding for 1~1.5h to eliminate residual stress at room temperature in the billet and prevent cracks from forming during subsequent rapid heating; then heating at 70~80℃ / h to 900℃ and holding for 1.5~2h to ensure uniform internal temperature of the billet and alleviate the temperature gradient caused by differences in the thermal conductivity of alloying elements; finally heating at 100℃ / h to the target temperature of 1150℃-1200℃ and holding for 2~3h to bring the billet to the plastic state required for initial forging, slightly promote the diffusion of alloying elements, and provide favorable conditions for forging.

3. The method for producing W-containing high-Mo hot work die steel according to claim 2, characterized in that, The specific steps of S7 include: using double normalizing to spray water mist after exiting the furnace at 1180℃, cooling the billet to 680~720℃; transferring the cooled billet to an isothermal furnace for isothermal spheroidization, controlling the isothermal furnace temperature at 20℃–50℃ below the Ac1 line (828℃), i.e., 778~808℃, holding for 5~7 hours, and after holding, furnace cooling to 500~530℃, and then air cooling after exiting the furnace.

4. The method for producing W-containing high-Mo hot work die steel according to claim 1, characterized in that, The inner side of the scissor lifter is provided with a pair of friction transmission mechanisms for friction transmission with the surface of the forging. A bevel gear transmission mechanism is provided between the friction transmission mechanism and the chain transmission mechanism. The bevel gear transmission mechanism converts the axial relative motion between the friction transmission mechanism and the forging into the circumferential relative motion between the chain transmission mechanism and the surface of the forging.

5. The method for producing W-containing high-Mo hot work die steel according to claim 4, characterized in that, The chain drive mechanism includes a central sprocket assembly and two opening / closing sprocket assemblies. The central sprocket assembly includes four coaxially distributed central sprockets, and the opening / closing sprocket assemblies include two coaxially distributed opening / closing sprockets. The two opening / closing sprocket assemblies are axially staggered, and each of the two opening / closing sprocket assemblies is connected to the central sprocket via a chain. Both the opening / closing sprockets and the central sprockets include several chain teeth and tooth grooves.

6. The method for producing W-containing high-Mo hot work die steel according to claim 5, characterized in that, One side of the opening and closing sprocket assembly is provided with a fixed sprocket assembly, each fixed sprocket assembly including two fixed sprockets. A tensioning assembly is provided between the fixed sprockets. The tensioning assembly includes a tension spring plate, and the tension spring plate includes a C-shaped segment. One end of the C-shaped segment is provided with a positioning hole, which cooperates with a positioning shaft provided on the end face of the fixed sprocket. The other end of the C-shaped segment is provided with a braking segment, which bends and extends outward toward the fixed sprocket assembly. The end of the braking segment is provided with a connecting hole, and a tensioning shaft is provided in the connecting hole. A tensioning roller is provided on the tensioning shaft, and the roller surface of the tensioning roller contacts and cooperates with the drive surface of the chain.

7. The method for producing W-containing high-Mo hot work die steel according to claim 4, characterized in that, The friction transmission mechanism includes a contact wheel with a groove on its surface. A transmission wheel is positioned above the contact wheel with an annular protrusion on its surface. The surface and annular protrusion of the transmission wheel are in frictional engagement with the surface and groove of the contact wheel, respectively. A rotating shaft is positioned at the center of the transmission wheel. A bearing seat is positioned at one end of the rotating shaft and is mounted on a transmission arm. A fixed shaft for mounting the contact wheel is positioned on the transmission arm. The other end of the rotating shaft is positioned inside a transmission box. The bevel gear transmission mechanism includes a small bevel gear connected to the rotating shaft and a large bevel gear that rotates coaxially with the chain transmission mechanism.

8. The method for producing W-containing high-Mo hot work die steel according to claim 1, characterized in that, The scissor lift includes a pair of left connecting arms and a pair of right connecting arms. Top hinges are provided at the top of the left and right connecting arms. Left and right hinges are respectively provided at the bottom of the left and right connecting arms. A pair of left hook arms and a pair of right hook arms are respectively mounted on the left and right hinges. An intermediate hinge, aligned vertically with the top hinges, is provided between the left and right hook arms. Reinforcing shafts are provided at their respective turning points on the left and right hook arms. Positioning cylinders are mounted on the reinforcing shafts. Positioning plates are provided on the walls of the positioning cylinders. The positioning plates engage with slots on the left and right hook arms. The positioning plates limit the minimum opening diameter of the scissor lift.

9. The method for producing W-containing high-Mo hot work die steel according to claim 8, characterized in that, The horizontal hanging assembly includes a U-shaped plate with two pairs of spaced guide holes that correspond to the left and right hinge shafts respectively. The end of the U-shaped plate is provided with a horizontal lifting lug. The vertical hanging assembly includes a lever head that rotates with the top hinge shaft. The top of the lever head is provided with a connecting bar, and the top of the connecting bar is provided with a vertical lifting lug.

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