A multi-dimensional collaborative segmented preheating process for a die casting ingot die suitable for a low temperature environment

Abstract

The application belongs to the technical field of low-temperature environment die casting and discloses a die casting ingot die multi-dimensional collaborative segmented preheating process suitable for a low-temperature environment, which comprises four modules, namely, ingot die partition precise preheating, workshop environment heat compensation linkage, ingot die material differentiation preheating correction and preheating-pouring parameter dynamic matching, and a stable heat environment of the low-temperature environment die casting is constructed through four-dimensional collaboration, and the whole process is implemented by relying on existing die casting equipment. Through five-zone differentiated segmented preheating of a melt flow path, ingot die periphery microenvironment heat protection, different material ingot die exclusive preheating scheme, linkage adjustment of preheating effect and pouring parameters, the problems of insufficient pouring, high cold separation defect rate, easy thermal shock cracking of the ingot die and poor production stability in a low-temperature workshop in the north in winter are solved, the casting insufficient pouring defect rate under the low-temperature environment can be reduced from 20% to below 2.5%, the cold separation defect rate can be reduced to below 0.8%, and the die casting production qualified rate can be increased from 75% to above 98%.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature environment casting technology, specifically involving a multi-dimensional collaborative segmented preheating process for casting ingots suitable for low-temperature environments. It is applicable to the casting production of various cast steel, cast iron, stainless steel and other castings of 50-300 tons in workshops in northern winters (ambient temperature -10℃ to 5℃). Background Technology

[0002] In northern regions, the ambient temperature in mold casting workshops during winter is often between -10℃ and 5℃. This low-temperature environment has a significant negative impact on mold casting production. On the one hand, the low-temperature ingot mold causes the high-temperature melt to dissipate heat rapidly, resulting in a sharp drop in melt fluidity and a defect rate of up to 20% for incomplete filling. At the same time, uneven cooling at the melt front can easily form cold shuts, seriously affecting the integrity of the casting. On the other hand, the rapid cooling rate after the melt comes into contact with the low-temperature ingot mold can easily form a coarse grain structure, causing the tensile strength of the casting to decrease by 10%-15% and the impact toughness to decrease by more than 25%. Furthermore, a large temperature difference between the ingot mold and the melt can also cause thermal shock, leading to ingot mold cracking and a shortened service life.

[0003] Traditional low-temperature ingot casting preheating schemes have several limitations: First, the use of a single, overall preheating method makes it impossible to achieve precise temperature control based on the functional differences of different areas of the ingot mold. Insufficient preheating in the pouring cup area leads to premature cooling of the melt, while overheating in the bottom area of ​​the cavity can easily cause localized overheating. Second, it neglects thermal compensation in the workshop environment, making the ingot mold susceptible to temperature drops after preheating due to the influence of low-temperature air, thus significantly reducing the preheating effect. Third, it fails to develop differentiated preheating strategies for ingot mold materials. Cast iron ingot molds are prone to cracking due to rapid temperature rise, while copper ingot molds are difficult to maintain the preheating temperature due to their high thermal conductivity. Fourth, preheating is disconnected from the casting process, making it impossible to dynamically adjust casting parameters based on the actual preheating effect, further exacerbating the risk of defects.

[0004] Current technologies for improving low-temperature mold casting primarily focus on single aspects: some technologies increase the overall ambient temperature by adding large workshop heating equipment, but this is energy-intensive and has a limited temperature control range, failing to achieve precise thermal protection around the ingot mold; some technologies use dedicated ingot mold preheating furnaces for overall temperature control, but the equipment purchase cost is high and cannot provide differentiated preheating based on the functional needs of different areas of the ingot mold, resulting in poor adaptability; other technologies only alleviate the problem of rapid cooling of the melt at low temperatures by optimizing the pouring temperature, but excessively high pouring temperatures can lead to coarse grains in the casting, failing to balance pouring integrity and microstructure uniformity. Furthermore, some existing patented technologies only achieve localized preheating optimization of the ingot mold, without constructing a multi-dimensional collaborative preheating system, making it difficult to completely solve the core pain points of low-temperature mold casting production. With the continuous increase in mold casting capacity demand in northern winters, the industry urgently needs to develop a low-cost, multi-dimensional, and highly adaptable ingot mold preheating process to fill the technological gap in stable and high-quality production of low-temperature mold casting. Summary of the Invention

[0005] The core objective of this invention is to provide a multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments, in order to solve various defects in ingot casting workshops in northern winters. Specific objectives include: constructing a four-dimensional collaborative system of "regional graded preheating + environmental thermal compensation + material adaptation and control + casting linkage" to reduce the incomplete filling and cold shut defect rates in low-temperature environments, and improve the uniformity of casting grains; developing differentiated preheating schemes for different ingot mold materials to avoid thermal shock damage to the ingot molds and extend their service life; and achieving dynamic matching between preheating and casting processes to ensure melt fluidity and solidification uniformity in low-temperature environments, thereby improving the stability of ingot casting production in winter.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments. The core technical solution lies in precise segmented preheating of the ingot mold, coordinated thermal compensation of the workshop environment, differentiated preheating correction based on ingot mold material, and dynamic matching of preheating-pouring parameters. This four-dimensional collaborative process constructs a stable thermal environment for low-temperature ingot casting and is implemented entirely using existing equipment. Specifically, it includes: 1) Precise preheating of ingot mold zones: Based on the melt flow path and solidification characteristics, the ingot mold is divided into five functional areas: the pouring cup area, the sprue area, the runner area, the cavity core area, and the cavity bottom area. Existing high-frequency, medium-frequency, and low-frequency induction heating coils are used to achieve differentiated preheating for each area, and the temperature and holding time of each area are strictly adapted to its functional positioning.

[0007] The pouring cup area uses high-frequency induction heating with a frequency of 10-15kHz and a preheating temperature of 320-400℃. During the heating process, the temperature is monitored in real time by an existing infrared thermometer, and the temperature deviation is controlled within ±5℃ to ensure that the melt maintains good fluidity before entering the mold cavity and to avoid the melt flow being obstructed due to excessive temperature drop at the inlet.

[0008] Direct casting section: Medium frequency induction heating is adopted, with a frequency of 2-5kHz and a preheating temperature of 250-320℃; one temperature measuring point is set at the inlet and outlet of the direct casting section to monitor the temperature gradient at the inlet and outlet in real time, and control the gradient range within 20-30℃ / m to prevent the melt from turbulently flowing and slag entrapment due to excessive temperature difference along the process.

[0009] Horizontal runner area: Medium frequency induction heating is adopted, with a frequency of 2kHz and a preheating temperature of 220-280℃; at the same time, shallow annular grooves with a depth of 2-4mm are opened on the inner wall of the horizontal runner to enhance the heat radiation absorption efficiency during the preheating stage and ensure uniform temperature in all sections of the horizontal runner.

[0010] Core area of ​​the cavity: Low-frequency induction heating is adopted, with a frequency of 500-800Hz and a preheating temperature of 170-250℃; the upper limit of the temperature is adjusted according to the casting material: 230-250℃ for cast steel and 200-220℃ for cast iron, taking into account both melt fluidity and the requirements for finer grains in the casting.

[0011] Bottom area of ​​the cavity: Low-frequency induction heating is used, with a frequency of 500Hz and a preheating temperature of 120-180℃; a 4-6mm thick graphite insulation pad is laid at the bottom of the cavity to form a bottom heat buffer layer to prevent the melt from cooling rapidly after contacting the bottom of the mold.

[0012] 2) Workshop environmental thermal compensation linkage: While the ingot mold is preheating, the existing local temperature control equipment in the workshop is activated to create a micro-environmental thermal protection zone around the ingot mold, offsetting heat loss from the low-temperature environment: Thermal protection zone setup: When the workshop ambient temperature is <0℃, turn on 3 hot air cannons around the ingot mold. The hot air cannon outlet temperature should be 60-80℃ and the air volume should be 5m³ / h. 3 / min, forming a closed thermal protection zone with a radius of 1.5-2.5m around the ingot mold, so that the ambient temperature around the surface of the ingot mold is stably maintained at 15-20℃; if the ambient temperature in the workshop is in the range of 0-5℃, then turn on 2 hot air cannons to maintain the ambient temperature around the ingot mold at 10-15℃. Dynamic temperature control adjustment: During the entire preheating process, environmental data is collected in real time by the workshop temperature and humidity sensor. If the ambient temperature fluctuates by more than ±5℃, the power of the hot air gun will be automatically adjusted. The power adjustment range is 50%-100% to ensure the stability of the ingot mold preheating environment and avoid temperature drop after the ingot mold preheating is completed.

[0013] 3) Preheating correction for ingot mold material differences: We developed a customized preheating sub-solution to address the thermophysical properties of three mainstream ingot mold materials: cast iron, copper, and ceramic. This solution avoids thermal shock damage and ensures both effective preheating and longevity of the ingot mold.

[0014] For cast iron ingot molds: the preheating temperature of the gating cup area should be controlled at 350-400℃, and the holding time should be 18-22 minutes; the preheating temperature of the sprue area should be 280-320℃, and the holding time should be 13-17 minutes; the preheating temperature of the runner area should be 250-280℃, and the holding time should be 10-14 minutes; the preheating temperature of the core area of ​​the cavity should be 200-250℃, and the holding time should be 16-20 minutes; the preheating temperature of the bottom area of ​​the cavity should be 150-180℃, and the holding time should be 8-12 minutes.

[0015] Before preheating, perform a low-temperature drying pretreatment for 8-12 minutes, with the pretreatment temperature controlled at 80-100℃, to remove residual moisture inside the mold cavity; then execute the preheating according to the above-mentioned zone preheating parameters, with the heating rate controlled at 20-30℃ / min to avoid cracking of the cast iron ingot mold due to excessive heating.

[0016] For copper ingot molds: the preheating temperature of the gating cup area should be controlled at 320-370℃, and the holding time should be 12-15 minutes; the preheating temperature of the sprue area should be 250-290℃, and the holding time should be 7-10 minutes; the preheating temperature of the runner area should be 220-250℃, and the holding time should be 4-7 minutes; the preheating temperature of the core area of ​​the cavity should be 170-220℃, and the holding time should be 10-13 minutes; the preheating temperature of the bottom area of ​​the cavity should be 120-150℃, and the holding time should be 2-5 minutes.

[0017] Based on the high thermal conductivity of copper, the upper limit of the preheating temperature in each area is lowered, and a shorter holding time is used to achieve rapid temperature uniformity. At the same time, a 1-2mm high-temperature resistant heat insulation coating is sprayed on the mold wall. The thermal conductivity of the high-temperature resistant heat insulation coating is ≤0.5W / (m•K), which reduces the heat loss of the ingot mold after preheating.

[0018] For ceramic ingot molds: the preheating temperature of the gating cup area should be controlled at 350-400℃, and the holding time should be 30-35min; the preheating temperature of the sprue area should be 280-320℃, and the holding time should be 25-30min; the preheating temperature of the runner area should be 250-280℃, and the holding time should be 22-27min; the preheating temperature of the core area of ​​the cavity should be 200-250℃, and the holding time should be 28-33min; the preheating temperature of the bottom area of ​​the cavity should be 150-180℃, and the holding time should be 20-25min.

[0019] The "step heating" mode is adopted, with the temperature increasing by 40-60℃ every 4-6 minutes until the target preheating temperature of each area is reached; a longer heat preservation time is used to ensure uniform temperature inside the ceramic ingot mold; after preheating, it is left to stand for 4-6 minutes to eliminate internal thermal stress before the casting operation is carried out to avoid damage to the ceramic ingot mold due to thermal shock.

[0020] 4) Dynamic matching of preheating and casting parameters: By integrating the preheating data of each area of ​​the ingot mold into the existing PLC casting control system, the preheating effect and casting process can be linked and adjusted to ensure casting quality in low-temperature environments. Steady-state casting strategy: When the preheating temperature of each area of ​​the ingot mold meets the standard (the actual temperature deviates from the target value by ≤±5℃) and the environmental thermal protection is stable, the "low-speed steady flow" casting strategy is adopted, and the casting speed is controlled at 0.6-0.7m / s to reduce the impact of the melt on the cavity and the air entrapment, while taking into account the integrity of casting and the uniformity of the casting structure.

[0021] Slight Deviation Emergency Compensation Strategy: When the actual preheating temperature of the core area of ​​the ingot mold cavity deviates from the target value by -5℃ to -20℃ (slight non-compliance), and cannot be corrected by extending the holding time due to continuous production cycle limitations, the pouring temperature is increased according to the actual preheating temperature difference, based on the standard room temperature pouring temperature corresponding to the material and specifications of the casting. For every 10℃ decrease in temperature difference, the pouring temperature is increased by 8~10℃, and the pouring speed is increased to 0.8~1.0m / s to compensate for the loss of melt fluidity under low temperature conditions.

[0022] Termination strategy for severe deviation: When the actual preheating temperature deviation of the core area of ​​the ingot mold cavity is <-20℃, simply increasing the pouring temperature will cause irreversible defects such as coarse grains, thermal cracks, and shrinkage cavities. At this time, pouring should be stopped immediately, and the ingot mold preheating program should be re-executed until the temperature reaches the standard.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention achieves a multi-dimensional breakthrough compared to traditional low-temperature ingot casting preheating technology through a multi-dimensional collaborative segmented preheating process for ingot molds. Specific beneficial effects are as follows: 1. Significantly reduced casting defects and improved casting quality: Through a four-dimensional collaborative preheating system of "regional graded preheating + environmental heat compensation + material adaptation and control + casting linkage", the incomplete casting defect rate of castings in the low-temperature environment of northern winters has been reduced from 20% to below 2.5% in the traditional process, and the cold shut defect rate has been reduced to below 0.8%. The grain uniformity of castings has been improved by more than 40% compared with the traditional process. The grain uniformity is evaluated by the relative deviation of the average grain size at different positions of the casting cross-section. The smaller the relative deviation, the higher the uniformity. The batch deviation of tensile strength of cast steel parts has been reduced to ±5MPa, and the low-temperature impact toughness has been improved by more than 25% compared with the traditional process. The internal quality and mechanical property stability of castings have been significantly improved.

[0024] 2. No new dedicated equipment required, significant cost and energy advantages: This process relies entirely on the existing induction heating and local temperature control equipment in the workshop. The cost of modifying a single production line is ≤200,000 yuan, and there is no need to purchase large-scale dedicated preheating devices. Moreover, the environmental heat compensation uses local hot air cannons to build a micro-environmental heat protection circle, which reduces energy consumption by 60% compared with the traditional overall workshop heating mode, and reduces the operation and maintenance cost of mold casting production by 30% in winter.

[0025] 3. Extended ingot mold lifespan and strong process adaptability: Differentiated preheating solutions for different ingot mold materials fundamentally avoid thermal shock damage to ingot molds. The lifespan of cast iron ingot molds is extended by 15% compared to traditional processes, and the preheating breakage rate of ceramic ingot molds is reduced to below 1%. The process is adaptable to various castings such as cast steel, cast iron, stainless steel, and heat-resistant steel, as well as the three mainstream ingot mold materials of cast iron, copper, and ceramics, without the need to replace the core equipment of the production line.

[0026] 4. Enhanced production stability and strong capacity guarantee in winter: The dynamic matching mechanism between preheating effect and pouring parameters increases the pass rate of die casting production in the low-temperature environment of northern winter from 75% of the traditional process to more than 98%. The uniformity of the casting grains fully meets the technical requirements of precision mechanical castings, and completely solves the technical problem of low production capacity and quality of die casting in northern winter. Attached Figure Description

[0027] Figure 1 This is a three-dimensional schematic diagram of the ingot mold of the present invention.

[0028] Figure 1 The gating cup area is the funnel-shaped opening that receives molten steel, while the sprue area is the area that enters the mold cavity vertically after entering the gating cup area.

[0029] Figure 2 This is the front view of the ingot mold of the present invention.

[0030] Figure 3 This is a top view of the ingot mold of the present invention.

[0031] In the diagram: 1-Gating cup area, 2-Straight runner area, 3-Horizontal runner area, 4-Cavity core area, 5-Cavity bottom area. Detailed Implementation

[0032] To further describe the present invention, specific embodiments are provided below, which will more clearly demonstrate the advantages and various effects of the present invention. Those skilled in the art should understand that these specific embodiments are illustrative of the invention and not intended to limit it.

[0033] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] This invention belongs to the field of low-temperature environment casting technology, specifically involving a four-dimensional collaborative ingot mold preheating device and process that integrates regional graded preheating, environmental thermal compensation, material adaptation control, and casting linkage. It is suitable for casting production of various cast steel, cast iron, and stainless steel castings weighing 50-300 tons in northern winter workshops (ambient temperature -10℃ to 5℃), especially suitable for precision mechanical castings and heavy equipment castings with stringent requirements for casting stability and grain uniformity. It can solve defects such as incomplete filling and cold shuts caused by rapid cooling of the melt in low-temperature environments without adding dedicated preheating equipment, ensuring high quality and stability in winter casting production. The invention is described in detail below through six specific embodiments, which can be found in [reference needed]. Figures 1-3 The embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection.

[0036] Example 1: 100-ton Q235 cast steel parts (cast iron ingot mold, workshop temperature -5℃) Ingot mold parameters: see Figures 1-3 The cast iron ingot mold is divided into five preheating zones: the pouring cup zone is heated to 350℃ using 10kHz high-frequency induction heating and held for 20 minutes; the sprue zone is heated to 280℃ using 2kHz medium-frequency induction heating and held for 15 minutes; the runner zone is heated to 250℃ using 2kHz medium-frequency induction heating and held for 12 minutes; the core cavity zone is heated to 230℃ using 500Hz low-frequency induction heating and held for 18 minutes; and the bottom cavity zone is heated to 150℃ using 500Hz low-frequency induction heating and held for 10 minutes. A 5mm thick graphite insulation pad is laid at the bottom of the cavity. Temperature measuring points are set at the inlet and outlet of the sprue to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to 25℃ / m. A 3mm deep annular shallow groove is made on the inner wall of the runner. Process parameters: Before preheating, a low-temperature drying pretreatment at 80℃ for 10 minutes is performed; the heating rate during preheating is controlled at 25℃ / min; three hot air guns are activated to maintain an ambient temperature of 15℃ within a 2m radius around the ingot mold; the actual preheating temperature of the core area of ​​the cavity meets the standard; low-speed steady-flow pouring is adopted, with a pouring speed of 0.7m / s and a pouring temperature of 1520℃. Implementation results: The incomplete casting defect rate is 2.0%, with no cold shut defects; the uniformity of the grain size in the casting cross-section is improved by 42% compared to the traditional process, and the relative deviation of the average grain size is controlled within 8%; the ingot mold experiences no thermal shock cracking, and the service life per furnace is extended by 15% compared to the traditional process; the measured tensile strength of the casting body is 425MPa, the yield strength is 240MPa, and the batch tensile strength deviation within the same batch is ±3MPa, fully meeting the technical requirements of heavy machinery frames.

[0037] Example 2: 80-ton HT200 cast iron parts (ceramic ingot mold, workshop temperature 0℃) Ingot mold parameters: see Figures 1-3The ceramic ingot mold employs a stepped heating mode with a temperature increase of 50℃ every 5 minutes. The pouring cup area is heated to 380℃ using 12kHz high-frequency induction heating and held for 30 minutes; the sprue area is heated to 300℃ using 3kHz medium-frequency induction heating and held for 25 minutes; the runner area is heated to 260℃ using 2kHz medium-frequency induction heating and held for 22 minutes; the cavity core area is heated to 200℃ using 600Hz low-frequency induction heating and held for 28 minutes; and the cavity bottom area is heated to 160℃ using 500Hz low-frequency induction heating and held for 20 minutes. After preheating, the mold is allowed to stand for 5 minutes. Temperature measuring points are set at the sprue inlet and outlet to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to within 20℃ / m. A 3mm deep annular shallow groove is made on the inner wall of the runner. Process parameters: Two hot air cannons were activated to maintain an ambient temperature of 10℃ within a 2m radius around the ingot mold; the preheating temperature of the core area of ​​the cavity met the standard; the pouring speed was 0.6m / s; and the pouring temperature was 1380℃. Implementation results: The incomplete filling defect rate was 1.8%, and the cold shut defect rate was 0.5%; the grain uniformity of the casting cross-section was improved by 40% compared to the traditional process, and the relative deviation of the average grain size was controlled within 9%; the ceramic ingot mold experienced no thermal shock damage, and the service life of a single furnace was extended by 20% compared to the traditional process; the measured hardness of the casting was HB195-205, and the hardness uniformity deviation within the same batch was ±3HB, fully meeting the requirements for casting use.

[0038] Example 3: 150-ton 304 stainless steel parts (copper ingot mold, workshop temperature -8℃) Ingot mold parameters: see Figures 1-3The mold is constructed using copper ingots. The sprue area is heated to 360℃ using 15kHz high-frequency induction heating and held for 12 minutes; the sprue area is heated to 280℃ using 5kHz medium-frequency induction heating and held for 10 minutes; the runner area is heated to 240℃ using 2kHz medium-frequency induction heating and held for 7 minutes; the core cavity area is heated to 210℃ using 800Hz low-frequency induction heating and held for 10 minutes; and the bottom cavity area is heated to 140℃ using 500Hz low-frequency induction heating and held for 5 minutes. A 2mm thick high-temperature resistant heat-insulating coating is applied to the mold wall. Temperature measuring points are installed at the sprue inlet and outlet to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to within 30℃ / m. A 3mm deep annular shallow groove is created on the inner wall of the runner. Process parameters: Three hot air cannons were activated to maintain an ambient temperature of 20℃ within a 2m radius around the ingot mold; the actual preheating temperature of the core area of ​​the cavity was 15℃ lower than the target value (a slight deviation within the range of -5℃ to -20℃), and due to the limitations of continuous production cycle, the holding time could not be extended to compensate. Based on the standard room temperature pouring temperature of 1540℃ for 304 stainless steel, the pouring temperature was increased by 15℃ to 1555℃, and the pouring speed was adjusted to 1.0m / s. Implementation results: The incomplete casting defect rate was 2.3%, with no cold shut defects; the uniformity of the grain size of the casting cross-section was improved by 45% compared to the traditional process, and the relative deviation of the average grain size was controlled within 7%; the heat loss after preheating of the copper ingot mold was reduced by 50% compared to the traditional process, and the service life of a single furnace was extended by 18% compared to the traditional process; the corrosion resistance of the casting met the standards in the neutral salt spray test, fully meeting the requirements for use in food machinery equipment.

[0039] Example 4: 50-ton 42CrMo alloy steel parts (cast iron ingot mold, workshop temperature 2℃) Ingot mold parameters: see Figures 1-3The cast iron ingot mold undergoes a low-temperature drying pretreatment at 100℃ for 10 minutes before preheating, with the heating rate controlled at 30℃ / min. The gating cup area is heated to 400℃ using 10kHz high-frequency induction heating and held for 20 minutes; the sprue area is heated to 320℃ using 2kHz medium-frequency induction heating and held for 15 minutes; the runner area is heated to 280℃ using 2kHz medium-frequency induction heating and held for 12 minutes; the cavity core area is heated to 250℃ using 500Hz low-frequency induction heating and held for 18 minutes; and the cavity bottom area is heated to 180℃ using 500Hz low-frequency induction heating and held for 10 minutes. Temperature measuring points are set at the sprue inlet and outlet to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to 20℃ / m. A 3mm deep annular shallow groove is made on the inner wall of the runner. Process parameters: Two hot air cannons were activated to maintain an ambient temperature of 12℃ within a 2m radius around the ingot mold; preheating temperatures in all areas met standards; low-speed steady-flow casting was adopted, with a casting speed of 0.6m / s and a casting temperature of 1540℃. Implementation results: The incomplete casting defect rate was 1.5%, and the cold shut defect rate was 0.3%; the grain uniformity of the casting cross-section was improved by 43% compared to traditional processes, and the relative deviation of the average grain size was controlled within 7%; the measured tensile strength of the casting body was 990MPa, the yield strength was 860MPa, and the batch tensile strength deviation was ±4MPa, fully meeting the technical requirements of wind turbine main shafts.

[0040] Example 5: 200-ton 12Cr1MoV heat-resistant steel parts (ceramic ingot mold, workshop temperature -10℃) Ingot mold parameters: see Figures 1-3 The ceramic ingot mold employs a stepped heating mode with a temperature increase of 50℃ every 5 minutes. The pouring cup area is heated to 390℃ using 12kHz high-frequency induction heating and held for 35 minutes; the sprue area is heated to 310℃ using 3kHz medium-frequency induction heating and held for 28 minutes; the runner area is heated to 270℃ using 2kHz medium-frequency induction heating and held for 25 minutes; the cavity core area is heated to 220℃ using 700Hz low-frequency induction heating and held for 30 minutes; and the cavity bottom area is heated to 170℃ using 500Hz low-frequency induction heating and held for 22 minutes. After preheating, the mold is allowed to stand for 5 minutes. Temperature measuring points are set at the sprue inlet and outlet to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to 26℃ / m. A 3mm deep annular shallow groove is made on the inner wall of the runner. Process parameters: Three hot air cannons were activated to maintain an ambient temperature of 18℃ within a 2m radius around the ingot mold; the preheating temperature of the core area of ​​the cavity met the standard; the pouring speed was 0.7m / s; and the pouring temperature was 1560℃. Implementation results: The incomplete casting defect rate was 2.2%, with no cold shut defects; the grain uniformity of the casting cross-section was improved by 41% compared to the traditional process, and the relative deviation of the average grain size was controlled within 8%; the high-temperature creep strength of the casting at 550℃ for 1000 hours was 185MPa, fully meeting the technical requirements of thermal power equipment; the ceramic ingot mold experienced no thermal shock damage, and the service life per furnace was extended by 22% compared to the traditional process.

[0041] Example 6: 120-ton 20CrMnTi gear steel parts (cast iron ingot mold, workshop temperature 5℃) Ingot mold parameters: see Figures 1-3 The cast iron ingot mold was preheated at 90℃ for 10 minutes before preheating, with the heating rate controlled at 25℃ / min. The gating cup area was heated to 370℃ using 10kHz high-frequency induction heating and held for 20 minutes; the sprue area was heated to 290℃ using 2kHz medium-frequency induction heating and held for 15 minutes; the runner area was heated to 260℃ using 2kHz medium-frequency induction heating and held for 12 minutes; the cavity core area was heated to 240℃ using 600Hz low-frequency induction heating and held for 18 minutes; and the cavity bottom area was heated to 160℃ using 500Hz low-frequency induction heating and held for 10 minutes. Temperature measuring points were set at the sprue inlet and outlet to monitor the temperature gradient in real time, controlling the inlet and outlet gradient to 22℃ / m. A 3mm deep annular shallow groove was made on the inner wall of the runner. Process parameters: Two hot air cannons were activated to maintain an ambient temperature of 10℃ within a 2m radius around the ingot mold; preheating temperatures in all areas met standards; low-speed, steady-flow pouring was employed at a pouring speed of 0.6m / s and a pouring temperature of 1530℃. Implementation results: The incomplete casting defect rate was 1.2%, and the cold shut defect rate was 0.2%; the grain uniformity of the casting cross-section was improved by 44% compared to traditional processes, and the average relative deviation of grain size was controlled within 6%; the gear tooth surface hardness after machining was HRC59-61, with excellent surface quality, fully meeting the requirements for heavy-duty vehicle gearbox gears.

[0042] The above embodiments demonstrate that the low-temperature environment casting multi-dimensional collaborative ingot mold segmented preheating process of the present invention can play a stable role under different low-temperature environments, different ingot mold materials and casting types, and has the advantages of defect control, quality improvement and cost, providing reliable technical support for casting production in northern winters.

[0043] This invention divides the ingot mold into five core areas according to the melt flow path. For different functional requirements such as the gating cup area and the core cavity area, it matches high-frequency, medium-frequency, and low-frequency induction heating schemes, solving the precise temperature control problems of insufficient preheating of the gating gate and overheating of the bottom in traditional technologies. A new environmental heat compensation linkage design is added, constructing a micro-environmental heat protection ring through local hot air cannons. The number and power of equipment activated are dynamically adjusted according to the workshop temperature to avoid temperature drop caused by low-temperature air after ingot mold preheating. A dynamic matching mechanism for preheating and pouring is established, integrating preheating data into the PLC control system. The pouring temperature and speed can be automatically adjusted according to the actual preheating effect, achieving intelligent switching between low-temperature compensation and steady-state pouring. Customized preheating strategies are developed for the thermophysical characteristics of three mainstream ingot mold materials: cast iron, copper, and ceramic. Cast iron ingot molds incorporate low-temperature drying pretreatment to control the heating rate; copper ingot molds have lowered preheating temperatures and are equipped with heat-insulating coatings; and ceramic ingot molds employ stepped heating and static resting to eliminate thermal stress. This design avoids the problems of mold cracking and shortened lifespan caused by traditional uniform preheating, and significantly improves process adaptability.

[0044] This invention achieves efficient upgrades by leveraging existing equipment, eliminating the need for additional dedicated preheating equipment. It utilizes existing induction heating, temperature control, and insulation devices in the workshop to complete the process modification, with a single production line modification cost of ≤200,000 RMB. This significantly reduces the purchase and maintenance costs of large preheating furnaces in traditional technologies. Thermal compensation uses localized hot air cannons instead of overall workshop heating, reducing energy consumption by 60%. Simultaneously, it reduces the incomplete casting defect rate from 20% to below 2.5%, and improves the uniformity of casting grains by 40%, achieving a dual breakthrough in cost control and quality improvement.

[0045] This invention is applicable to workshop environments in northern winters ranging from -10℃ to 5℃, and can be adapted to the production of various castings such as cast steel, cast iron, and stainless steel, ranging from 50 to 300 tons. It particularly meets the stringent requirements of precision machinery and heavy equipment for casting stability and grain uniformity. Compared with existing technologies that only focus on a single casting type or local preheating optimization, the multi-dimensional collaborative system achieves comprehensive coverage of low-temperature ingot casting scenarios.

[0046] Those skilled in the art should recognize that the above embodiments are merely illustrative of the invention and not intended to limit it, but are similarly limited to the scope of the invention. Variations and modifications to the above embodiments will fall within the protection scope of the claims. It should be understood that the endpoints and values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of various ranges, the endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0047] It should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Additionally, the term "and / or" as used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone.

[0048] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A multi-dimensional collaborative segmented preheating process for ingot casting molds suitable for low-temperature environments, characterized in that, Specifically, it includes: 1) Partial preheating of ingot mold: The mold is divided into five functional areas: the sprue cup area, the sprue area, the runner area, the cavity core area, and the cavity bottom area. Induction heating coils are used to achieve differentiated preheating for each area: sprue cup area, frequency 10-15kHz, preheating temperature controlled at 320-400℃; sprue area, frequency 2-5kHz, preheating temperature 250-320℃; runner area, frequency 2kHz, preheating temperature 220-280℃; cavity core area, frequency 500-800Hz, preheating temperature 170-250℃; cavity bottom area, frequency 500Hz, preheating temperature 120-180℃. 2) Workshop environmental thermal compensation linkage: When the ambient temperature in the workshop is <0℃, a closed thermal protection zone is formed around the ingot mold to keep the ambient temperature around the surface of the ingot mold stable at 15-20℃; if the ambient temperature in the workshop is in the range of 0-5℃, the ambient temperature around the ingot mold is maintained at 10-15℃. 3) Dynamic matching of preheating and casting parameters: Real-time data collection of preheating temperatures in various areas of the ingot mold and connection to the PLC pouring control system enables coordinated adjustment of preheating effect and pouring process: When the deviation between the actual preheating temperature and the target value in the core area of ​​the ingot mold cavity is -5℃ to -20℃ and cannot be corrected by extending the holding time, the standard pouring temperature corresponding to the material and specifications of the casting is used as the benchmark, and the pouring temperature is increased accordingly based on the actual preheating temperature deviation. For every 10℃ decrease in the actual preheating temperature difference, the pouring temperature is increased by 8~10℃, and the pouring speed is increased to 0.8~1.0m / s. If the preheating temperature meets the standard and the environmental thermal protection is stable, the pouring speed is controlled at 0.6~0.7m / s. If the actual preheating temperature deviation is less than -20℃, stop pouring and repeat the preheating procedure until the standard is met.

2. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, In step 1), temperature measuring points are set at the inlet and outlet of the sprue to monitor the temperature gradient in real time and control the temperature gradient at the inlet and outlet of the sprue to be 20-30℃ / m.

3. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, A shallow annular groove with a depth of 2-4mm is made on the inner wall of the horizontal runner.

4. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, In step 1), the preheating temperature of the core area of ​​the cavity is adjusted according to the casting material: when the casting is cast steel, the upper limit of the preheating temperature is 230-250℃; when the casting is cast iron, the upper limit of the preheating temperature is 200-220℃.

5. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, Lay a 4-6mm thick graphite insulation pad at the bottom of the cavity.

6. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, For cast iron ingot molds: the preheating temperature of the gating cup area should be controlled at 350-400℃, with a holding time of 18-22 minutes; the preheating temperature of the sprue area should be 280-320℃, with a holding time of 13-17 minutes; the preheating temperature of the runner area should be 250-280℃, with a holding time of 10-14 minutes; the preheating temperature of the cavity core area should be 200-250℃, with a holding time of 16-20 minutes; the preheating temperature of the cavity bottom area should be 150-180℃, with a holding time of 8-12 minutes; the heating rate during the preheating process should be controlled at 20-30℃ / min. Before preheating, perform a low-temperature drying pretreatment. The pretreatment temperature is controlled at 80-100℃ and the pretreatment time is 8-12 minutes.

7. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, For copper ingot molds: the preheating temperature of the gating cup area is controlled at 320-370℃, and the holding time is 12-15 minutes; the preheating temperature of the sprue area is 250-290℃, and the holding time is 7-10 minutes; the preheating temperature of the runner area is 220-250℃, and the holding time is 4-7 minutes; the preheating temperature of the core area of ​​the cavity is 170-220℃, and the holding time is 10-13 minutes; the preheating temperature of the bottom area of ​​the cavity is 120-150℃, and the holding time is 2-5 minutes; at the same time, a 1-2 mm high-temperature resistant heat-insulating coating is sprayed on the mold wall, and the thermal conductivity of the high-temperature resistant heat-insulating coating is ≤0.5W / (m•K).

8. The multi-dimensional collaborative segmented preheating process for ingot molds suitable for low-temperature environments according to claim 1, characterized in that, For ceramic ingot molds: the preheating temperature of the pouring cup area should be controlled at 350-400℃, and the holding time should be 30-35 minutes; the preheating temperature of the sprue area should be 280-320℃, and the holding time should be 25-30 minutes; the preheating temperature of the runner area should be 250-280℃, and the holding time should be 22-27 minutes; the preheating temperature of the core cavity area should be 200-250℃, and the holding time should be 28-33 minutes; the preheating temperature of the bottom cavity area should be 150-180℃, and the holding time should be 20-25 minutes; the temperature should be increased by 40-60℃ every 4-6 minutes until the target preheating temperature of each area is reached; after preheating, let it stand for 4-6 minutes before pouring.

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