High strength drive wheel casting process

Abstract

The present application relates to the technical field of casting process, and more particularly to a high-strength driving wheel casting process. The steps include: step one, alloy material preparation, step two, smelting and micro-alloying treatment, step three, mold preparation and pouring, step four, solidification cooling and grading control, and step five, heat treatment process. Through alloy component optimization, mold structure improvement, smelting and pouring precision control, and heat treatment process adaptation, the technical problems of insufficient strength, high defect rate, and poor forming precision of the existing driving wheel are solved. The cooling chamber is improved in structure and adapted in process. The controllable atmosphere cooling chamber is combined with the grading cooling process, and the partition isolation component, waste heat recovery component, and temperature control unit are set, so that the independent cooling of the casting, precise temperature control, and waste heat reuse are realized, and the problems of "air flow interference, uneven cooling, and energy waste" of the existing cooling chamber are solved.

Description

Technical Field

[0001] This invention relates to the field of casting technology, and in particular to a high-strength drive wheel casting process. Background Technology

[0002] As a core load-bearing component of vehicles and construction machinery, the drive wheel must withstand the weight of the entire vehicle, dynamic loads, and impacts under complex road conditions for extended periods. Its strength, toughness, and molding precision directly determine the operational safety and reliability of the equipment. Currently, existing drive wheel casting processes mainly suffer from the following technical defects:

[0003] Traditional drive wheels are mostly made of ordinary cast iron or basic cast steel without targeted alloy micro-alloying optimization. Their tensile strength and yield strength are insufficient, making it difficult to meet the requirements of heavy-duty scenarios and prone to problems such as rim cracking and hub deformation. Some processes use the addition of a single alloying element, which cannot achieve a synergistic improvement in strength and toughness.

[0004] Conventional sand casting is a complex process that requires core making, makes it difficult to control wall thickness, and is prone to defects such as porosity, shrinkage cavities, and slag inclusions, resulting in a high scrap rate. Although lost foam casting does not require core making, the white pattern has low strength and is prone to deformation during processes such as brushing, drying, and embedding, affecting the forming accuracy and structural integrity of the casting. In the application of graphite molds, there are problems such as difficulty in cleaning risers and uneven microstructure.

[0005] The smelting process is simple, but the purity of the molten metal is insufficient, which easily leads to the formation of oxide inclusions. The casting method is unreasonable, and the molten steel is easily exposed to air and oxidized. Furthermore, the casting speed and temperature are not accurately controlled, resulting in a loose internal structure and unstable mechanical properties in the casting.

[0006] The cooling process was not graded and controlled, resulting in an excessive temperature difference between the inside and outside of the casting, which easily generates thermal stress and leads to crack defects. The heat treatment process parameters were poorly adapted and were not optimized according to the material characteristics of the drive wheel, which failed to fully utilize the potential of the material's mechanical properties and made it difficult to achieve a balance between high strength and high toughness.

[0007] Chinese invention patent 201610386903.7 discloses a low-alloy high-strength and high-toughness cast steel and its preparation method. The steel composition is C 0.3%-0.4%, Si 0.6%-1.4%, Mn 0.8%-1.3%, Cr 0.6%-1.4%, Mo 0.1%-0.4%, V 0.06%-0.15%, and RE 0.03%-0.1%, and it employs a quenching and tempering treatment. However, this patent has the following drawbacks: First, the alloy system does not contain Nb, resulting in limited grain refinement, and the excessively high Si content (0.6%-1.4%) reduces low-temperature impact toughness. Second, the casting process does not use graphite molds and argon-protected pouring, making the castings prone to oxide inclusions and porosity defects. Third, the solidification and cooling process lacks graded control, making thermal stress prone to causing cracks. Fourth, the heat treatment only employs quenching and tempering, lacking normalizing pretreatment and low-temperature aging, which fails to fully eliminate residual stress and stabilize the microstructure.

[0008] Therefore, there is an urgent need to develop a high-strength drive wheel casting process that can solve the above-mentioned defects and balance strength and molding quality. Summary of the Invention

[0009] Therefore, in response to the above problems, this invention proposes a high-strength drive wheel casting process, which solves the technical problems of insufficient strength, high defect rate and poor forming accuracy of existing drive wheels by optimizing alloy composition, improving mold structure, accurately controlling melting and pouring and adapting heat treatment process.

[0010] To achieve the above objectives, the present invention adopts the following technical solution, comprising the following steps:

[0011] Step 1: Alloy Material Preparation: Prepare the alloy raw materials according to the following mass percentages: C 0.38%–0.40%, Si 0.30%–0.50%, Mn 1.20%–1.50%, Cr 0.80%–1.20%, Ni 0.60%–0.90%, Mo 0.30%–0.50%, Nb 0.03%–0.06%, V 0.04%–0.08%, RE 0.02%–0.05%, P≤0.020%, S≤0.015%, with the balance being Fe and unavoidable impurities; wherein, the mass ratio of Mo to Nb is controlled between 9:1 and 11:1, and the mass ratio of V to RE is controlled between 1.8:1 and 2.2:1;

[0012] Step 2, Smelting and Microalloying: The alloy raw materials prepared in Step 1 are put into a medium-frequency induction furnace for smelting. After deoxidation, the composition of the molten metal is adjusted to the target range.

[0013] Step 3, mold preparation and pouring: Graphite molds are used, and argon gas is used for pouring. The pouring temperature is controlled at 1520-1540℃.

[0014] Step 4: Solidification and Cooling Stage Control: After pouring, the mold is placed in a cooling chamber for staged cooling. Staged cooling includes at least a forced air cooling stage, and the casting temperature drops to 800-850℃ after the forced air cooling stage. The cooling chamber is a controlled atmosphere cooling chamber, which includes a track on its lower interior, a side fan assembly installed on the inner side wall of the cooling chamber, a guide component installed on the upper wall of the cooling chamber, and a partition isolation component on the track. Forced air cooling is achieved through the cooperation of the side fan assembly and the guide component. Different castings are cooled in separate zones through the partition isolation component. Temperature sensors and airflow adjustment devices are also installed inside the cooling chamber to monitor and adjust the cooling rate in real time.

[0015] Step 5, Heat Treatment Process: The casting obtained in Step 4 is subjected to heat treatment, which includes normalizing, quenching, tempering and low-temperature aging in sequence; wherein, the quenching is performed using a polymer quenching medium, the tempering temperature is controlled at 560-600℃, and the low-temperature aging temperature is controlled at 180-220℃.

[0016] Furthermore, the RE mentioned in step one is a lanthanide rare earth mixture, wherein La accounts for 25%-30% of the total mass of RE, Ce accounts for 20%-25%, Pr accounts for 15%-20%, and Nd accounts for 25%-30%.

[0017] Furthermore, in step two, the smelting temperature is controlled at 1620-1650℃, and the deoxidation treatment includes adding aluminum wire accounting for 0.10%-0.15% of the total mass of the molten metal for precipitation deoxidation, and then adding silicon-calcium alloy accounting for 0.05%-0.08% of the total mass of the molten metal for diffusion deoxidation. The tapping temperature is controlled at 1580-1600℃.

[0018] Furthermore, in step three, the inner surface of the graphite mold is coated with zircon powder coating with a thickness of 0.3-0.5 mm. After the coating is dried, the mold temperature is controlled at 150-200℃. The gating system adopts bottom pouring, and a foam ceramic filter screen with a pore size of 10-15 ppi is set at the pouring cup. The argon flow rate for the argon-protected pouring is 15-25 L / min, and the pouring speed is controlled at 3-5 kg / s.

[0019] Furthermore, the staged cooling described in step four includes:

[0020] First stage cooling: The mold is naturally cooled to 1000-1050℃ in the cooling chamber, with the cooling rate controlled at 15-20℃ / min;

[0021] Second stage of cooling: When the casting temperature drops to 1000-1050℃, start the cooling chamber fan for forced air cooling, with the cooling rate controlled at 25-35℃ / min, cooling to 800-850℃;

[0022] Third stage of cooling: Turn off the fan and let the casting cool naturally to 300-350℃ in the cooling chamber, then open the box and take out the casting.

[0023] Furthermore, the normalizing treatment described in step five involves heating the casting to 920-940℃, holding it for 1.5-2.0 min / mm based on the effective wall thickness of the casting, and then removing it from the furnace and air-cooling it to room temperature.

[0024] The quenching process involves heating the normalized casting to 860-880℃, holding it for 1.2-1.5 min / mm based on the effective wall thickness, and then quenching it with a PAG-type water-soluble polymer quenching medium. The quenching medium has a mass concentration of 10%-15%, a temperature of 30-40℃, and a quenching cooling time of 3-5 min.

[0025] The tempering process involves heating the quenched casting to 560-600℃, holding it for 2.0-2.5 min / mm based on the effective wall thickness, and then air-cooling it to room temperature after holding.

[0026] The low-temperature aging treatment involves heating the tempered casting to 180-220℃, holding it for 3.0-4.0 min / mm based on the effective wall thickness, and then cooling it in the furnace to below 100℃ before air cooling.

[0027] Furthermore, the normalizing, quenching, tempering and low-temperature aging treatments described in step five are carried out in a continuous heat treatment furnace with a nitrogen protective atmosphere inside the furnace; the quenching cooling time is controlled at 3.5-4.5 min.

[0028] Furthermore, the drive wheel manufactured using this process has a hardness difference between the rim and hub controlled within ±3HB, an impact absorption energy of 48-55J at -20℃, a tensile strength of 1000-1050MPa, a yield strength of 850-880MPa, and an elongation of 13%-15%.

[0029] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0030] This invention improves the structure and adapts the process of the cooling chamber, combining the controlled atmosphere cooling chamber with the staged cooling process. It sets up a partition isolation component, a waste heat recovery component, and a temperature control unit, realizing independent partitioned cooling of castings, precise temperature control, and waste heat reuse. It solves the problems of "airflow interference, uneven cooling, and energy waste" in existing cooling chambers. This deep integration of equipment structure and process steps cannot be achieved by ordinary technicians simply combining existing equipment with conventional processes.

[0031] By strictly controlling the mass percentages of C, Si, Mn, Cr, Ni, Mo, Nb, V, and rare earth element REs, and limiting the specific ratios of Mo to Nb and V to REs, combined with the addition of lanthanide rare earth composites, the grain size can be significantly refined, grain boundaries purified, and carbide morphology and distribution improved, greatly enhancing the strength and toughness of the drive wheel. The prepared drive wheel has a tensile strength of 1000~1050MPa, a yield strength of 850~880MPa, an elongation of 13~15%, and a low-temperature impact absorption energy of 48~55J at -20℃, exhibiting both high strength and good low-temperature toughness, meeting the requirements for heavy-load and harsh operating conditions.

[0032] The system employs a three-stage cooling process of "natural cooling - forced air cooling - natural cooling" and precisely controls the cooling rate at each stage. Combined with controlled atmosphere and argon protection during casting, it avoids internal stress, deformation, shrinkage cavities, and oxide inclusion defects caused by rapid heating and cooling of the casting. Directional air delivery is provided to weak areas such as the drive wheel teeth to achieve synchronous and uniform cooling of the entire structure and key parts, significantly reducing the deformation and cracking tendency of thin-walled gear rings and improving the casting yield.

[0033] Furthermore, by using partitioned isolation components to form independent annular cooling cavities, coupled with multi-zone independent temperature control units and staggered cooling fans, independent cooling of different castings and different parts can be achieved, avoiding airflow collisions and temperature interference. With adjustable airflow direction and volume fans and a flow guide structure, adaptive and precise temperature control is achieved during the cooling process, ensuring the cooling rate remains stable within a preset range. Simultaneously, a waste heat recovery component is installed in the cooling chamber to recover the waste heat from the 100~800℃ high-temperature exhaust gas, heating it into hot water for reuse in mold preheating and cleaning processes, achieving resource utilization of waste heat. The fans and water pumps adopt variable frequency speed regulation and are linked to temperature control, intelligently adjusting their operating power according to the cooling stage. Combined with condensate collection and recycling, this significantly reduces energy and water consumption, resulting in higher production efficiency. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the drive wheel structure of the present invention;

[0035] Figure 2 This is a schematic diagram of the cooling chamber structure of the present invention. Figure 1 ;

[0036] Figure 3This is a schematic diagram of the cooling chamber structure of the present invention. Figure 2 ;

[0037] Figure 4 This is a schematic diagram of the installation structure of the partition isolation component and the flow guide of the present invention;

[0038] Figure 5 This is a schematic diagram of the partition isolation component of the present invention;

[0039] Figure 6 This is a schematic diagram of the structure of the support platform of the present invention;

[0040] In the diagram: Cooling chamber shell-1, base-2, track-3, waste heat recovery assembly-4, side fan assembly-5, air guide-6, partition isolation assembly-7, mounting base-71, height adjustment mechanism-72, support platform-73, drive rod-74, No. 1 isolation plate-75, No. 2 isolation plate-76, vent-7a, mounting ring-7b, air cooler-77, platform-731, inner ring area-732, outer ring area-733, ventilation perforation-734, telescopic adjustment column-735, telescopic sleeve-736, movable rod-737, positioning sheath-738, flexible contact plate-739. Detailed Implementation

[0041] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0042] refer to Figures 1-6 This embodiment provides a high-strength drive wheel casting process, the structure of which includes the following steps:

[0043] Step 1: Alloy Material Preparation: Prepare the alloy raw materials according to the following mass percentages: C 0.38%–0.40%, Si 0.30%–0.50%, Mn 1.20%–1.50%, Cr 0.80%–1.20%, Ni 0.60%–0.90%, Mo 0.30%–0.50%, Nb 0.03%–0.06%, V 0.04%–0.08%, RE 0.02%–0.05%, P≤0.020%, S≤0.015%, with the balance being Fe and unavoidable impurities; wherein, the mass ratio of Mo to Nb is controlled between 9:1 and 11:1, and the mass ratio of V to RE is controlled between 1.8:1 and 2.2:1;

[0044] In this specific embodiment, RE is a mixture of lanthanide rare earth elements, wherein La accounts for 25%-30% of the total mass of RE, Ce accounts for 20%-25%, Pr accounts for 15%-20%, and Nd accounts for 25%-30%.

[0045] Step 2, Smelting and Microalloying: The alloy raw materials prepared in Step 1 are put into a medium-frequency induction furnace for smelting. After deoxidation, the composition of the molten metal is adjusted to the target range.

[0046] In this specific embodiment, the smelting temperature is controlled at 1620-1650℃, and the deoxidation treatment includes adding aluminum wire accounting for 0.10%-0.15% of the total mass of the molten metal for precipitation deoxidation, and then adding silicon-calcium alloy accounting for 0.05%-0.08% of the total mass of the molten metal for diffusion deoxidation. The tapping temperature is controlled at 1580-1600℃.

[0047] Step 3, mold preparation and pouring: Graphite molds are used, and argon gas is used for pouring. The pouring temperature is controlled at 1520-1540℃.

[0048] In this specific embodiment, the inner surface of the graphite mold is coated with zircon powder coating with a thickness of 0.3-0.5mm. After the coating is dried, the mold temperature is controlled at 150-200℃. The gating system adopts bottom pouring, and a foam ceramic filter screen with a pore size of 10-15ppi is set at the pouring cup. The argon flow rate for argon-protected pouring is 15-25L / min, and the pouring speed is controlled at 3-5kg / s.

[0049] Step 4: Solidification and Cooling Stage Control: After pouring, place the mold in a cooling chamber for staged cooling. Staged cooling includes at least a forced air cooling stage, and the casting temperature drops to 800-850℃ after the forced air cooling stage.

[0050] In this specific embodiment, the cooling chamber is a controlled atmosphere cooling chamber, and the staged cooling includes:

[0051] First stage cooling: The mold is naturally cooled to 1000-1050℃ in the cooling chamber, with the cooling rate controlled at 15-20℃ / min;

[0052] Second stage of cooling: When the casting temperature drops to 1000-1050℃, start the cooling chamber fan for forced air cooling, with the cooling rate controlled at 25-35℃ / min, cooling to 800-850℃;

[0053] Third stage of cooling: Turn off the fan and let the casting cool naturally to 300-350℃ in the cooling chamber, then open the box and take out the casting.

[0054] Step 5, Heat Treatment Process: The castings obtained in Step 4 are subjected to heat treatment, which includes normalizing, quenching, tempering and low-temperature aging in sequence. Among them, the quenching is carried out using polymer quenching medium, the tempering temperature is controlled at 560-600℃, and the low-temperature aging temperature is controlled at 180-220℃.

[0055] In step five, the normalizing treatment involves heating the casting to 920-940℃, holding it for 1.5-2.0 min / mm based on the effective wall thickness of the casting, and then removing it from the furnace and air-cooling it to room temperature.

[0056] The quenching process involves heating the normalized casting to 860-880℃, holding it for 1.2-1.5 min / mm based on the effective wall thickness, and then quenching it with a PAG-type water-soluble polymer quenching medium. The quenching medium has a mass concentration of 10%-15%, a temperature of 30-40℃, and a quenching cooling time of 3-5 min.

[0057] Tempering involves heating the quenched casting to 560-600℃, holding it for 2.0-2.5 min / mm of effective wall thickness, and then air-cooling it to room temperature after holding.

[0058] Low-temperature aging treatment involves heating the tempered casting to 180-220℃, holding it for 3.0-4.0 min / mm based on the effective wall thickness, and then cooling it in the furnace to below 100℃ before air cooling.

[0059] In step five, the normalizing, quenching, tempering and low-temperature aging treatments are carried out in a continuous heat treatment furnace with a nitrogen protective atmosphere inside the furnace; the quenching cooling time is controlled at 3.5-4.5 min.

[0060] The drive wheel manufactured using this process has a hardness difference between the rim and hub controlled within ±3HB, an impact absorption energy of 48-55J at -20℃, a tensile strength of 1000-1050MPa, a yield strength of 850-880MPa, and an elongation of 13%-15%.

[0061] To further improve the performance of the above casting process, the cooling chamber in step four includes a cooling chamber shell 1, a base 2 located below the cooling chamber shell 1, a track 3 located on its lower interior side, a waste heat recovery assembly 4 installed on the exterior of the cooling chamber shell 1, a side fan assembly 5 installed on the inner wall of the cooling chamber shell 1, a guide 6 installed on the upper interior wall of the cooling chamber shell 1, and a partition isolation assembly 7 installed on the track 3. Forced air cooling in the staged cooling process is achieved through the cooperation of the side fan assembly 5 and the guide 6. Different castings are cooled in different partitions through the partition isolation assembly 7. Temperature sensors and airflow adjustment devices are also installed inside the cooling chamber to monitor and adjust the cooling rate in real time.

[0062] The base 2 is equipped with a drive mechanism that moves linearly back and forth on the track 3, which is isolated from the drive partition component 7;

[0063] The aforementioned drive mechanism is existing technology and can be a geared motor or a linear reciprocating motion mechanism, etc. The specific choice can be made according to the actual application.

[0064] Because existing cooling chambers directly discharge a large amount of waste heat released by the castings during the cooling process, resulting in energy waste, and require continuous power consumption to drive fans and water pumps during the cooling process, the operating cost is high; therefore, in this embodiment, a waste heat recovery component 4 is installed at the exhaust port at the top of the cooling chamber shell 1, which is sealed to the exhaust port on the surface of the cooling chamber shell 1. It is used to exchange heat between the high-temperature waste gas (100-800℃) generated during the cooling process and the cold water in the heat exchanger, heating the cold water to 80-100℃; the heated hot water is connected to the casting preheating furnace and the hot water tank of the cleaning process through pipelines to realize the recovery and reuse of waste heat. Furthermore, variable frequency speed control modules are added to the cooling chamber fans and water pumps, which are linked with the temperature monitoring module to automatically adjust the operating power of the fans and water pumps according to the temperature requirements of the cooling stage (e.g., during the first stage of natural cooling, the fans and water pumps run at low speed to reduce energy consumption; during the second stage of forced air cooling, the power is increased as needed). At the same time, a condensate collection tank is set at the bottom of the cooling chamber to collect the condensate generated during the cooling process, filter it, and recycle it for water-cooled components to reduce water waste.

[0065] The side fan assembly 5 consists of a controllable speed fan and multiple cold air outlet ducts. Each cold air outlet duct has multiple adjustable airflow heads distributed on its surface. At least two of these cold air outlet ducts are positioned corresponding to the side of the drive wheel teeth. It should be noted that the air outlet of the side fan assembly 5 maintains a 20-30cm distance from the partition isolation assembly 7 to prevent the fan airflow from directly blowing onto the partition isolation assembly 7. The guide component 6 is installed on the top of the cooling chamber housing 1 and is installed corresponding to the partition isolation assembly 7. Specifically, the guide component 6 consists of a controllable speed fan and a guide shroud, and its upper part is detachably installed to the upper part of the cooling chamber housing 1 via an adjustable bracket. It should be noted that the guide component 6 does not contact the partition isolation assembly 7 below. The fan installation height is 15-20cm from the surface of the partition isolation assembly 7, and the air outlet faces the open area at the top of the cooling cavity of the partition isolation assembly 7, achieving unobstructed delivery of cold air into the cavity, thereby covering the entire surface of the drive wheel. Furthermore, the airflow guide can be adjusted to change the airflow direction according to the needs of the cold zone, and it is compatible with the structure of the drive wheel throughout the entire process.

[0066] The partition isolation component 7 includes a mounting base 71 mounted on the track 3, a height adjustment mechanism 72 disposed on the surface of the mounting base 71, a support platform 73 fixedly mounted to the top of the height adjustment mechanism 72, drive rods 74 disposed on the side of the support platform 73 and evenly distributed at equal intervals, a first isolation plate 75 connected to the end of the drive rods 74, and a second isolation plate 76 installed inside the first isolation plate 75. The first isolation plate 75 and the second isolation plate 76 have the same structure, and both have vents 7a on their surfaces and mounting rings 7b at their tops. An adjustable air cooler 77 is mounted on the mounting ring 7b on the top of the first isolation plate 75 in the inward direction, and an adjustable air cooler 77 is mounted on the mounting ring 7b on the top of the second isolation plate 76 in the outward direction. The air coolers 77 on the first isolation plate 75 and the second isolation plate 76 are staggered to avoid airflow collision.

[0067] It should be noted that the isolation plate is a breathable flexible plate. The top of the second isolation plate 76 is connected to the first isolation plate 75 via a mounting ring 7b and a detachable thin rod.

[0068] The drive rod 74 can be either an electric push rod or a lead screw, depending on the actual application.

[0069] In practical applications, the aforementioned drive rod 74 can be omitted. The ends of the first isolation plate 75 and the second isolation plate 76 are sealed to the surface of the support platform 73, forming an independent annular cooling cavity. The top of this cavity is completely open, while the lower part is sealed to the support platform, achieving a "top open, bottom enclosed" structure. The mounting ring 7b can also be telescopic, and the corresponding drive rod 74 can move vertically up and down. The lateral part connected to the isolation plate can also move horizontally, allowing adjustment of the annular cavity when the isolation plate is pushed horizontally. Specifically, a vertical connecting plate is provided on the surface of the isolation plate at the connection point of the drive rod 74 to facilitate cooperation with the drive rod 74 and the mounting ring 7b. The specific configuration is selected based on the actual application.

[0070] To further enhance the cooling effect of the drive wheel, a positioning device is installed in the middle of the surface of the support platform 73 to position the drive wheel before cooling, preventing poor cooling effect due to improper placement during the cooling process. The support platform 73 includes a hollow platform body 731, with a detachable telescopic adjustment column 735 in the middle of the platform body 731. The surface of the telescopic adjustment column 735 has telescopic sleeves 736 evenly and equidistantly distributed, and movable rods 737 that cooperate with the telescopic sleeves 736 to form telescopic adjustment. The surface of the telescopic sleeves 736 has positioning perforations, and the surface of the movable rod 737 also has positioning perforations at corresponding positions to the telescopic sleeves 736. Multiple positioning perforations are provided on the surface of the movable rod 737. The end of the movable rod 737 is provided with a flexible contact plate 739 that contacts the inner ring surface of the drive wheel. After the movable rod 737 and the telescopic sleeves 736 are adjusted to the required length, they are positioned in conjunction with the positioning sheath 738.

[0071] To address the problem of mutual interference between cold airflow and temperature in traditional drive wheel casting processes, this embodiment incorporates isolation plates in the solidification and cooling stage control of step four of the casting process. This achieves independent cooling for the entire system and its individual components. The cooling cavity is formed by the first isolation plate 75 and the second isolation plate 76. The specific support platform 73 includes a hollow platform body 731. The surface of the platform body 731 has an inner ring area 732 and an outer ring area 733, corresponding to the second isolation plate 76 and the first isolation plate 75, respectively. Since the platform body 731 has a hollow cavity structure, the cavity is divided into partitioned chambers corresponding to the inner ring area 732 and the outer ring area 733. These chambers correspond to the ventilation perforations 734 on the surface of the platform body 731, and each partitioned chamber has its own independent pipeline.

[0072] At the bottom of the side wall of the cooling chamber (corresponding to the inner and outer sides of the cooling chamber shell 1), there are 2-3 small exhaust holes. These exhaust holes are connected to different independent pipelines in the partitioned chambers, thereby ensuring that the exhaust gas and airflow in the cooling chamber shell 1 can be discharged independently and not cross-flow with the outside or other areas. Each exhaust hole is equipped with an adjustable valve, which can flexibly adjust the exhaust volume according to the amount of gas generated during the cooling stage.

[0073] The exhaust volume adjustment in this embodiment is specifically as follows:

[0074] During the first stage of natural cooling, the main fan of the cooling chamber runs at low speed, the opening of the temperature control valve of the waste heat recovery component 4 is reduced (about 30%), the cold air fan of the partition isolation component 7 is turned off, the exhaust port valve on the side wall of the cooling chamber shell 1 is opened at 30%, the temperature sensor collects the casting temperature in real time, and the ventilation volume adjustment device controls the cooling rate at 15-20℃ / min to reduce the rapid loss of heat in the cooling chamber.

[0075] During the second stage of forced air cooling, when the temperature sensor detects that the casting temperature has dropped to 1000-1050℃, the main control unit automatically increases the fan speed of the side fan assembly 5 and the guide 6 to 1500r / min, the cooling fan of the partition isolation assembly 7 starts (speed 1000r / min), the opening of the temperature control valve of the waste heat recovery assembly 4 is adjusted to 75%, the opening of the exhaust valve is adjusted to 75%, and the cooling rate is controlled at 25-35℃ / min through the air volume adjustment device, quickly discharging a large amount of waste gas and water vapor;

[0076] During the third stage of natural cooling, when the casting temperature drops to 800-850℃, the fan speed is gradually reduced to 500r / min, the opening of the temperature control valve of the waste heat recovery component 4 is gradually adjusted to 20%, and the opening of the exhaust valve is gradually adjusted to 20%. The natural cooling state is maintained by the air volume adjustment device until the casting temperature drops to 300-350℃, at which point the electrical control unit sends an opening signal.

[0077] The exhaust outlet faces downwards and outwards from the cooling chamber to prevent the high-temperature exhaust gas from directly contacting operators or surrounding equipment, thus improving operational safety.

[0078] Meanwhile, to achieve precise temperature control of different parts of the drive wheel during cooling, this embodiment configures an independent temperature control unit in each cooling area (the annular cooling cavity formed by the isolation plate). Each temperature control unit includes a temperature sensor, a controllable fan, a miniature water-cooling nozzle, and signal transmission lines. All temperature control units are electrically connected to the main electrical control unit of the cooling chamber, enabling centralized control and independent adjustment. The structure of the aforementioned temperature control units is existing conventional technology and will not be described in detail here.

[0079] It should be noted that the temperature sensor is a K-type thermocouple sensor, installed on each mounting ring 7b; the miniature water-cooled nozzles are made of stainless steel, with 2-4 evenly distributed within the guide member 6 (alternating with the top controllable speed fan, fixed by an independent bracket), and the nozzle orifice diameter is 2-3mm, enabling fine spraying. They are only activated when localized overheating occurs during the casting cooling process, requiring emergency cooling; the water-cooled nozzles are connected to the external water supply system of the cooling room via pipelines, and flow regulating valves are installed on the pipelines, with the flow rate automatically adjusted by the electronic control unit (adjustment range 0.5-2L / min).

[0080] In the above structure, the electronic control unit automatically calculates the current cooling rate based on the real-time temperature collected by the temperature sensor and compares it with a preset threshold. If the current rate is lower than the threshold, it automatically increases the corresponding fan speed (or activates the micro water-cooling nozzle); if the current rate is higher than the threshold, it automatically decreases the fan speed, ensuring that the cooling rate of each part remains stable within the preset range. This achieves adaptive temperature control and prevents deformation and cracking of the thin gear-shaped ring drive wheel due to uneven cooling. This operation can be implemented through existing programming, so it will not be elaborated here.

[0081] In this embodiment, the micro water-cooled nozzle in the above structure is set to start spraying at a flow rate of 0.5-2L / min when the local temperature of the casting is higher than the preset value of 50℃. The flow regulating valve on the pipeline is automatically controlled by the electronic control unit. The specific start-up conditions can be set according to the actual casting process.

[0082] It should be noted that the circuit control of the cooling chamber is electrically connected to an external control terminal, and this connection can be achieved through programming, so it will not be described in detail here.

[0083] Comparative Example (D1)

[0084] Traditional low-alloy high-strength and high-toughness cast steel and its preparation method. This comparative example prepares comparative specimens according to the technical solution disclosed in the comparative example, and conducts mechanical property comparison tests under the same test conditions as this application.

[0085] The alloy composition (wt%) of Comparative Example 1 is as follows: C 0.352%, Si 0.814%, Mn 1.128%, Cr 0.674%, Ce 0.066%, Mo 0.172%, V 0.093%, S 0.020%, P 0.023%, with the balance being Fe.

[0086] The smelting equipment was a 150kg industrial frequency furnace, with the smelting temperature controlled at 1620-1650℃. The smelting materials included scrap steel and ferrosilicon, ferromanganese, ferrochrome, rare earth ferrosilicon, ferromolybdenum, and ferrovanadium. Samples were taken and their composition before the furnace was tested using a direct-reading spectrometer, and adjustments were made accordingly. Rare earth ferrosilicon was added using a flushing method. When the molten steel temperature dropped to approximately 1560℃, a ceramic mold was poured in to cast a Kiel test block (simulating a drive wheel structure). After the mold cooled naturally to room temperature, the casting was removed from the mold.

[0087] Heat treatment: Heat the casting to 930℃ and hold for 2 hours, then quench it in water to room temperature; then heat it to 600℃ and hold for 2 hours, and finally air cool it to room temperature.

[0088] The following table compares the core performance indicators of the embodiments of the present invention with those of the comparative example (D1):

[0089]

[0090] The comparative experimental results above demonstrate that this invention, through alloy composition optimization (adding Ni and Nb, reducing Si, using composite rare earth elements, and limiting the Mo:Nb and V:RE ratios), improved casting process (graphite mold + argon-protected casting + bottom-pouring filtration system), graded cooling control (three-stage cooling with precise temperature control), and a complete heat treatment process chain (normalizing + quenching + tempering + low-temperature aging), combined with a zoned isolation structure of a controlled atmosphere cooling chamber, achieves unexpected technical effects compared to the comparative example (D1). All mechanical properties are significantly superior to those of the comparative example (D1), and the casting defect rate is greatly reduced, fully demonstrating the inventiveness and practicality of this invention.

[0091] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A high-strength drive wheel casting process, characterized in that, Includes the following steps: Step 1: Alloy Material Preparation: Prepare the alloy raw materials according to the following mass percentages: C 0.38%–0.40%, Si 0.30%–0.50%, Mn 1.20%–1.50%, Cr 0.80%–1.20%, Ni 0.60%–0.90%, Mo 0.30%–0.50%, Nb 0.03%–0.06%, V 0.04%–0.08%, RE 0.02%–0.05%, P≤0.020%, S≤0.015%, with the balance being Fe and unavoidable impurities; wherein, the mass ratio of Mo to Nb in the alloy raw materials is controlled between 9:1 and 11:1, and the mass ratio of V to RE is controlled between 1.8:1 and 2.2:1; Step 2, Smelting and Microalloying: The alloy raw materials prepared in Step 1 are put into a medium-frequency induction furnace for smelting. After deoxidation, the composition of the molten metal is adjusted to the target range. Step 3, mold preparation and pouring: Graphite molds are used, and argon gas is used for pouring. The pouring temperature is controlled at 1520-1540℃. Step 4, Solidification and Cooling Stage Control: After casting, the mold is placed in a cooling chamber for staged cooling. Staged cooling includes at least a forced air cooling stage, and the casting temperature drops to 800-850℃ after the forced air cooling stage. The cooling chamber is a controlled atmosphere cooling chamber, which includes a track (3) set on the lower side inside, a side fan assembly (5) installed on the inner side wall of the cooling chamber, a guide (6) installed on the upper wall of the cooling chamber, and a partition isolation assembly (7) set on the track (3). Forced air cooling is achieved through the cooperation of the side fan assembly (5) and the guide (6). Different castings are cooled in partitions through the partition isolation assembly (7). Temperature sensors and air volume adjustment devices are also set on the inner side of the cooling chamber to monitor and adjust the cooling rate in real time. Step 5, Heat treatment process: The casting obtained in Step 4 is subjected to heat treatment, which includes normalizing, quenching, tempering and low temperature aging in sequence; wherein, the quenching is performed using a polymer quenching medium, the tempering temperature is controlled at 560-600℃, and the low temperature aging temperature is controlled at 180-220℃. The staged cooling described in step four includes: First stage cooling: The mold is naturally cooled to 1000-1050℃ in the cooling chamber, with the cooling rate controlled at 15-20℃ / min; Second stage of cooling: When the casting temperature drops to 1000-1050℃, start the cooling chamber fan for forced air cooling, with the cooling rate controlled at 25-35℃ / min, cooling to 800-850℃; Third stage of cooling: Turn off the fan and let the casting cool naturally to 300-350℃ in the cooling chamber, then open the box and take out the casting.

2. The high-strength drive wheel casting process according to claim 1, characterized in that: The RE mentioned in step one is a mixture of lanthanide rare earth elements, wherein La accounts for 25%-30% of the total mass of RE, Ce accounts for 20%-25%, Pr accounts for 15%-20%, and Nd accounts for 25%-30%.

3. The high-strength drive wheel casting process according to claim 1, characterized in that: In step two, the smelting temperature is controlled at 1620-1650℃. The deoxidation treatment includes adding aluminum wire accounting for 0.10%-0.15% of the total mass of the molten metal for precipitation deoxidation, and then adding silicon-calcium alloy accounting for 0.05%-0.08% of the total mass of the molten metal for diffusion deoxidation. The tapping temperature is controlled at 1580-1600℃.

4. The high-strength drive wheel casting process according to claim 1, characterized in that: In step three, the inner surface of the graphite mold is coated with zircon powder coating with a thickness of 0.3-0.5 mm. After the coating is dried, the mold temperature is controlled at 150-200℃. The gating system adopts bottom pouring, and a foam ceramic filter screen with a pore size of 10-15 ppi is set at the pouring cup. The argon flow rate for the argon-protected pouring is 15-25 L / min, and the pouring speed is controlled at 3-5 kg / s.

5. The high-strength drive wheel casting process according to claim 1, characterized in that: The normalizing treatment described in step five involves heating the casting to 920-940℃, holding it for 1.5-2.0 min / mm based on the effective wall thickness of the casting, and then removing it from the furnace and air-cooling it to room temperature. The quenching process involves heating the normalized casting to 860-880℃, holding it for 1.2-1.5 min / mm based on the effective wall thickness, and then quenching it with a PAG-type water-soluble polymer quenching medium. The quenching medium has a mass concentration of 10%-15%, a temperature of 30-40℃, and a quenching cooling time of 3-5 min. The tempering process involves heating the quenched casting to 560-600℃, holding it for 2.0-2.5 min / mm based on the effective wall thickness, and then air-cooling it to room temperature after holding. The low-temperature aging treatment involves heating the tempered casting to 180-220℃, holding it for 3.0-4.0 min / mm based on the effective wall thickness, and then cooling it in the furnace to below 100℃ before air cooling.

6. The high-strength drive wheel casting process according to claim 5, characterized in that: The normalizing, quenching, tempering and low-temperature aging treatments described in step five are carried out in a continuous heat treatment furnace with a nitrogen protective atmosphere inside the furnace; the quenching cooling time is controlled at 3.5-4.5 min.

7. The high-strength drive wheel casting process according to claim 1, characterized in that: The drive wheel manufactured using this process has a hardness difference between the rim and hub controlled within ±3HB, an impact absorption energy of 48-55J at -20℃, a tensile strength of 1000-1050MPa, a yield strength of 850-880MPa, and an elongation of 13%-15%.

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