A dynamic roll gap compensation solidification device and process for ultra-thick gauge die cast ingot

Abstract

The application belongs to the technical field of casting, and discloses a dynamic roll gap compensation solidification device and process for super-thick specification die casting, which comprises an ingot mold, a support frame and a hydraulic roller assembly. The hydraulic roller assembly is arranged around the ingot mold through the support frame, is arranged in layers and zones along the height direction of the ingot mold, and the hydraulic rollers in the same layer are uniformly distributed along the circumference of the ingot mold. The process is divided into four stages. According to the solidification process of the casting, the corresponding area of the hydraulic roller is started in stages, the working pressure of the roller, the roll gap adjustment frequency and the total stroke are dynamically adjusted, and the precise compensation of the shell deformation is realized. The dynamic roll gap compensation mechanism is introduced into the die casting solidification stage, the core structure of the existing die casting production line does not need to be changed, the straightening strain of the casting can be reduced from 1.2% to 1.8% in the traditional process to below 0.79%, the hot crack rate can be reduced from 1.5% to 3.0% to below 0.4%, the solidification period is shortened by 10% to 15%, and the subsequent straightening process is not needed.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, specifically relating to a dynamic roll gap compensation solidification device and process for ultra-thick die casting ingots, which is particularly suitable for the production of ultra-thick carbon steel, alloy steel, stainless steel and other ingots with a thickness ≥450mm. Background Technology

[0002] In industrial manufacturing, ultra-thick ingots (≥450mm) have become a key material for core components of major equipment due to their excellent structural load-bearing capacity and impact resistance. However, solidification defects encountered during the ingot casting process have long constrained product quality improvement. In traditional ingot casting, ingot solidification relies on the static support of the ingot mold for heat dissipation. Due to the long solidification period of ultra-thick ingots (usually 8-24 hours), a significant temperature gradient exists from the surface to the core of the billet shell during solidification, leading to a mismatch between the pressure in the internal liquid phase region and the strength of the billet shell, which easily results in bulging deformation of the billet shell. This deformation induces tensile stress inside the ingot. When the stress exceeds the yield strength of the material, defects such as hot cracks, central porosity, and segregation will form, seriously affecting the mechanical properties and service safety of the ingot.

[0003] In existing technologies, solutions to solidification defects in ingot casting mainly focus on three directions: First, optimizing the material and structure of the ingot mold, such as using copper alloy ingot molds with better thermal conductivity or setting heat dissipation fins. However, such solutions are costly and have limited effect on solidification control in the core area of ​​ultra-thick ingots. Second, adjusting the pouring process parameters, such as lowering the pouring temperature or using stepped pouring, can alleviate uneven solidification, but it will lead to a decrease in production efficiency and cannot fundamentally solve the stress concentration problem caused by the bulging of the billet shell. Third, introducing a subsequent straightening process to correct ingot deformation through mechanical external force. However, ultra-thick ingots have high rigidity and are prone to secondary cracks during the straightening process. Moreover, the straightening strain usually exceeds 1.2%, which is difficult to meet high precision requirements.

[0004] Meanwhile, anti-bulging technology in continuous casting has matured, effectively suppressing billet deformation during solidification by dynamically adjusting the spacing and pressure of the support rollers. However, the process characteristics of continuous casting and ingot casting differ significantly: continuous casting is a continuous forming process with stable billet movement, while ingot casting is a static forming process, and the billet shell deformation exhibits non-linear characteristics during ingot solidification; the thickness of continuously cast billets is typically ≤300mm, while the thickness of ultra-thick ingots is more than 1.5 times greater, making the solidification mechanism more complex. Therefore, existing anti-bulging technology in continuous casting cannot be directly transferred to ingot casting. The industry urgently needs a dynamic solidification control technology that can adapt to the static forming characteristics of ingot casting and does not require large-scale modifications to existing production lines.

[0005] Furthermore, the mechanical structures of existing die casting production lines are mostly fixed designs. Adopting entirely new molding equipment would not only result in high investment costs (over ten million yuan for the modification of a single production line) but also a long modification cycle, disrupting the company's normal production rhythm. Therefore, developing a technology that is compatible with existing die casting production lines and addresses the solidification defects of ultra-thick ingots through process parameter optimization rather than equipment upgrades has significant industrial application value. Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic roll gap compensation solidification device and process for ultra-thick ingot casting, to solve problems such as long solidification cycles, severe bulging deformation of the billet shell, high crack rate, and excessive straightening strain in existing ingot casting processes. By introducing a dynamic roll gap compensation mechanism into the ingot casting solidification stage, and without changing the core mechanical structure of the existing ingot casting production line, precise micro-extrusion of the billet shell is achieved through hydraulic rollers added around the ingot mold, compensating for the deformation pressure of the billet shell and realizing high-quality solidification of ultra-thick ingots.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A dynamic roll gap compensation solidification device for ultra-thick die casting ingots includes an ingot mold, a support frame, and a hydraulic roll assembly. The hydraulic roll assembly is mounted around the ingot mold via the support frame. The hydraulic roll assembly is arranged in layers along the height direction of the ingot mold, and the hydraulic rolls in the same layer are evenly distributed along the circumference of the ingot mold.

[0008] The ingot mold is made of heat-resistant alloy steel, with an inner cavity thickness ranging from 450 to 900 mm and a height ranging from 1200 to 3000 mm. The inner wall of the ingot mold is coated with a silicon nitride-based heat-insulating coating with a thickness of 20 to 50 μm.

[0009] The vertical spacing between two adjacent hydraulic rolls is 180-300mm, the circumferential central angle between adjacent hydraulic rolls in the same layer is 45°-90°, each hydraulic roll is equipped with an independent hydraulic drive unit, the working pressure range of the hydraulic system of the hydraulic drive unit is 15-45MPa, and the roll gap adjustment stroke of the hydraulic roll is 0-45mm.

[0010] The longitudinal spacing of the hydraulic rollers at the top of the ingot die is 250-300mm; the longitudinal spacing of the hydraulic rollers in the middle of the ingot die is 200-250mm; and the longitudinal spacing of the hydraulic rollers at the bottom of the ingot die is 180-200mm.

[0011] The upper part of the ingot mold accounts for 20%-30% of the total height of the ingot mold, the middle part of the ingot mold accounts for 55%-65% of the total height of the ingot mold, and the lower part of the ingot mold accounts for 10%-15% of the total height of the ingot mold.

[0012] The hydraulic roll body is made of tungsten carbide hard alloy, with a roll diameter range of 120-200mm and a roll body length of 200-400mm. The roll surface is provided with an arc-shaped groove that matches the curvature of the outer wall of the ingot. The radius of curvature of the groove is 500-800mm, and the surface roughness Ra≤0.4μm.

[0013] A dynamic roll gap compensation solidification process for ultra-thick die casting ingots, comprising four stages, wherein the shell thickness in each stage is the average shell thickness of the corresponding height region of the ingot mold: The first stage is 1-3 hours after casting, when the average shell thickness in the corresponding area is 50-100mm. Only the upper hydraulic rollers of the ingot mold are activated, using a low-pressure, small-stroke mode. The working pressure is adjusted to 15-20MPa, and the roller gap is adjusted every 2-3 minutes. The total adjustment stroke of the roller gap is 5-15mm to suppress the initial bulging deformation of the shell. The second stage is 3-8 hours after casting, when the average shell thickness in the corresponding area reaches 100-250mm. The hydraulic rollers in the middle and upper parts of the ingot mold are started to work together. The working pressure of the upper and middle rollers of the ingot mold is adjusted to 25-35MPa, the roller gap adjustment frequency is 1-2 times / minute, and the total cumulative adjustment stroke of the roller gap is 15-30mm to compensate for the uneven deformation of the shell caused by the temperature gradient. The third stage is 8-16 hours after casting, when the average shell thickness in the corresponding area is ≥250mm and the liquid phase zone still exists in the core of the ingot. All hydraulic rolls are started and a high-pressure precision mode is adopted. The working pressure of all hydraulic rolls is adjusted to 35-45MPa, the roll gap adjustment frequency is 0.5-1 times / minute, and the total cumulative adjustment stroke of the roll gap is 30-45mm. The roll gap is dynamically adjusted according to the shell shrinkage rate to control the straightening strain of the ingot below 0.8%. The fourth stage is 16-24 hours after casting, when the ingot core is completely solidified. The working pressure of all rolls is gradually reduced to 5-10 MPa, while keeping the roll gap position unchanged, until the overall temperature of the ingot drops below 800℃, in order to avoid secondary stress during the ingot cooling process.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) Through dynamic extrusion compensation of hydraulic rollers, the bulging deformation of the billet shell of ultra-thick ingots is effectively suppressed. The straightening strain of the ingot is reduced from 1.2%-1.8% in the traditional process to below 0.79%, the hot crack rate is reduced from 1.5%-3.0% in the traditional process to below 0.4%, the central porosity grade is reduced from 2.5-3.0 in the traditional process to below 1.0, and the compositional segregation grade is reduced from 2.0-2.5 in the traditional process to below 1.0. The internal quality of the ingot fully meets the requirements of the first-level standard of GB / T6402-2018 "Ultrasonic Testing and Classification of Steel Forgings".

[0015] 2) This technology does not require modification of the core structure of the existing mold casting production line. The upgrade can be completed simply by adding hydraulic roller components around the ingot mold. The cost of upgrading a single production line is controlled at 3-5 million yuan, and the upgrade cycle does not exceed 15 days. It can quickly adapt to the production of ultra-thick ingots of different thicknesses and materials, ranging from 450-900mm, without the need to replace the main body of the ingot mold or adjust the overall layout of the production line.

[0016] 3) Compared with the traditional die casting process, this technology accelerates the heat transfer of the billet shell through the dynamic extrusion of hydraulic rollers, shortening the overall solidification cycle of the ingot by 10%-15%, eliminating the need for subsequent offline straightening processes, significantly reducing the ingot processing allowance and production scrap rate, and reducing the comprehensive production cost per ton of ingot by 8%-12%. At the same time, the hydraulic rollers adopt tungsten carbide wear-resistant material and modular split design, and the service life of a single set of rollers can reach 8,000-10,000 heats. The modular replacement method significantly reduces maintenance time and spare parts costs, and the overall maintenance cost is only 30%-50% of the overhaul cost of traditional ingot mold structure.

[0017] 4) By using a “layered and zoned” roll arrangement and a phased roll gap dynamic compensation design, the problem of precise control of nonlinear deformation during the solidification process of ultra-thick ingots was solved. This broke through the technical limitations of “static forming and passive heat dissipation” in traditional die casting process, and provided a new technical path for high-quality and low-cost production of ultra-thick high-end ingots. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the invention.

[0019] In the diagram: 1-support frame, 2-spindle mold, 3-hydraulic roll. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] like Figure 1As shown, a dynamic roll gap compensation solidification device for ultra-thick die casting ingots includes an ingot mold 2, a support frame 1, and a hydraulic roll 3 assembly. The hydraulic roll 3 assembly is mounted around the ingot mold 2 via the support frame 1. The hydraulic roll 3 assembly is arranged in layers along the height direction of the ingot mold, and the hydraulic rolls 3 in the same layer are evenly distributed around the circumference of the ingot mold 2.

[0024] The ingot mold 2 is made of heat-resistant alloy steel (such as H13 or 3Cr2W8V), and has a rectangular or circular structure to fit the conventional ingot mold specifications of existing die casting production lines. The inner cavity thickness ranges from 450-900mm, and the height is 1200-3000mm. The inner wall of the ingot mold 2 is coated with a silicon nitride-based heat-insulating coating with a thickness of 20-50μm to control the ingot solidification rate gradient. The support frame 1 is welded from high-strength carbon steel and is fixedly arranged around the ingot mold 2. A space is reserved between the support frame 1 and the outer wall of the ingot mold 2 for the installation and operation of the rollers, which is used to mount the hydraulic roller 3 assembly.

[0025] The hydraulic roll 3 assembly is the core execution unit of the process. It is arranged in layers along the height direction of the ingot mold 2. The vertical distance between two adjacent layers of hydraulic rolls 3 is 180-300mm. The circumferential central angle between adjacent hydraulic rolls 3 in the same layer is 45°-90°. Each hydraulic roll 3 is equipped with an independent hydraulic drive unit. The hydraulic system working pressure range of the hydraulic drive unit is 15-45MPa. The roll gap adjustment stroke of the hydraulic roll is 0-45mm. The working pressure and roll gap stroke can be dynamically adjusted according to the thickness and strength of the billet shell during the solidification stage of the ingot.

[0026] To accommodate the top-to-bottom solidification characteristics of ultra-thick ingots, the hydraulic rolls 3 are arranged in a differentiated "layered and zoned" design: the hydraulic rolls 3 in the upper part of the ingot mold (early solidification zone) have a longitudinal spacing of 250-300mm, mainly used to suppress slight bulging deformation of the billet shell in the early solidification stage; the hydraulic rolls 3 in the middle part of the ingot mold (mid-solidification zone) have a longitudinal spacing of 200-250mm, focusing on compensating for nonlinear deformation of the billet shell during solidification; and the hydraulic rolls 3 in the lower part of the ingot mold (late solidification zone) have a longitudinal spacing of 180-200mm, used to precisely control the shrinkage deformation of the ingot core at the end of solidification. Furthermore, the roller surface of the hydraulic rolls 3 is equipped with arc-shaped grooves with a radius of curvature of 500-800mm, matching the curvature of the ingot's outer wall to ensure uniform extrusion force on the billet shell and avoid localized stress concentration.

[0027] The upper part of the ingot mold accounts for 20%-30% of the total height of the ingot mold 2, the middle part of the ingot mold accounts for 55%-65% of the total height of the ingot mold 2, and the lower part of the ingot mold accounts for 10%-15% of the total height of the ingot mold 2.

[0028] The hydraulic roll 3 is made of tungsten carbide hard alloy, with a roll diameter range of 120-200mm and a roll length of 200-400mm. The roll surface is precision ground with a roughness Ra≤0.4μm to avoid scratching the billet surface.

[0029] A dynamic roll gap compensation solidification process for ultra-thick die casting ingots, comprising four stages, wherein the shell thickness in each stage is the average shell thickness of the corresponding height region of the ingot mold: The first stage is 1-3 hours after casting (early solidification stage). The average shell thickness in the corresponding area is 50-100mm. Only the upper hydraulic roller 3 of the ingot mold is activated, using a low-pressure, small-stroke mode. The working pressure is adjusted to 15-20MPa, and the roller gap is adjusted every 2-3 minutes. The total adjustment stroke of the roller gap is 5-15mm to suppress the bulging deformation of the shell in the early solidification stage. The second stage is 3-8 hours after casting (mid-solidification). When the average shell thickness in the corresponding area reaches 100-250mm, the hydraulic rollers in the middle and upper parts of the ingot mold are activated to work together. The working pressure of the upper and middle rollers of the ingot mold is adjusted to 25-35MPa. The roller gap adjustment frequency is 1-2 times / minute, and the total cumulative adjustment stroke of the roller gap is 15-30mm to compensate for the uneven deformation of the shell caused by the temperature gradient. The third stage is 8-16 hours after casting (late solidification stage). The average shell thickness in the corresponding area is ≥250mm, and a liquid phase zone still exists in the core of the ingot. All hydraulic rollers are started and a high-pressure precision mode is adopted. The working pressure of all hydraulic rollers is adjusted to 35-45MPa, the roller gap adjustment frequency is 0.5-1 times / minute, and the total cumulative adjustment stroke of the roller gap is 30-45mm. The roller gap is dynamically adjusted according to the shell shrinkage rate to control the straightening strain of the ingot below 0.8%. The fourth stage is 16-24 hours after casting (final solidification stage). The ingot core is completely solidified. The working pressure of all rolls is gradually reduced to 5-10 MPa, while keeping the roll gap position unchanged, until the overall temperature of the ingot drops below 800℃ to avoid secondary stress during the ingot cooling process.

[0030] The present invention will be described in detail below through six specific embodiments. These embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope of protection.

[0031] Example 1: Q235 carbon steel ultra-thick ingot (thickness 450mm); The ingot dimensions are 450mm × 1200mm × 3000mm, with a total ingot mold height of 3000mm, made of H13 material. The hydraulic roll assembly consists of four layers, with four hydraulic rolls evenly arranged around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 600mm high (accounting for 20% of the total height) with a hydraulic roll spacing of 300mm; the middle part of the ingot mold is 1950mm high (accounting for 65% of the total height) with a hydraulic roll spacing of 250mm; and the lower part of the ingot mold is 450mm high (accounting for 15% of the total height) with a hydraulic roll spacing of 200mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 120mm, a roll length of 200mm, and a roll surface roughness Ra≤0.4μm.

[0032] The casting temperature is 1520-1550℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 16MPa, a total cumulative adjustment stroke of 8mm for the roller gap, and an adjustment frequency of once every 3 minutes; Second stage (3-8 hours after casting): The middle rollers of the ingot mold are activated to work in tandem, with a working pressure of 26MPa for the upper middle rollers, a total cumulative adjustment stroke of 18mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (8-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 36MPa for all rollers, a total cumulative adjustment stroke of 32mm for the roller gap, and an adjustment frequency of once every 2 minutes; Fourth stage (16-20 hours after casting): The working pressure of the rollers is gradually reduced to 6MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain was 0.62%, the hot crack rate was 0.28%, the central porosity grade was 1, and the compositional segregation grade was 1.0, which fully meets the usage requirements of heavy machinery frames.

[0033] Example 2: 42CrMo alloy steel ultra-thick ingot (thickness 600mm); The ingot dimensions are 600mm × 1500mm × 2800mm, with a total ingot mold height of 2800mm, made of 3Cr2W8V material. The hydraulic roll assembly consists of 5 layers, with 6 hydraulic rolls evenly arranged around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 700mm high (accounting for 25% of the total height) with a hydraulic roll spacing of 280mm; the middle part of the ingot mold is 1680mm high (accounting for 60% of the total height) with a hydraulic roll spacing of 240mm; and the lower part of the ingot mold is 420mm high (accounting for 15% of the total height) with a hydraulic roll spacing of 190mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 150mm, a roll length of 250mm, and a roll surface roughness Ra≤0.4μm.

[0034] The casting temperature is 1540-1570℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 18MPa, a cumulative total adjustment stroke of 10mm for the roller gap, and an adjustment frequency of once every 2.5 minutes; Second stage (3-8 hours after casting): The middle rollers of the ingot mold are activated to work together, with the upper middle rollers working at a pressure of 30MPa, a cumulative total adjustment stroke of 22mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (8-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 40MPa for all rollers, a cumulative total adjustment stroke of 38mm for the roller gap, and an adjustment frequency of once every 1.5 minutes; Fourth stage (16-24 hours after casting): The working pressure of the rollers is gradually reduced to 9MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain was 0.71%, the hot crack rate was 0.35%, the tensile strength reached 980MPa, the yield strength was 850MPa, the central porosity grade was 0.8, and the compositional segregation grade was 0.8, which fully meets the performance requirements of wind turbine main shafts.

[0035] Example 3: 304 stainless steel ultra-thick ingot (750mm thick); The ingot dimensions are 750mm × 1800mm × 2500mm, with a total ingot mold height of 2500mm, made of H13 material. The hydraulic roll assembly consists of 6 layers, with 6 hydraulic rolls evenly arranged around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 625mm high (accounting for 25% of the total height) with a hydraulic roll spacing of 260mm; the middle part of the ingot mold is 1500mm high (accounting for 60% of the total height) with a hydraulic roll spacing of 230mm; and the lower part of the ingot mold is 375mm high (accounting for 15% of the total height) with a hydraulic roll spacing of 180mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 160mm, a roll length of 300mm, and a roll surface roughness Ra≤0.4μm.

[0036] The casting temperature is 1530-1560℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 20MPa, a total adjustment stroke of 12mm for the roller gap, and an adjustment frequency of once every 2 minutes; Second stage (3-8 hours after casting): The middle rollers of the ingot mold are activated to work together, with a working pressure of 32MPa for the upper middle rollers, a total adjustment stroke of 25mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (8-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 42MPa for all rollers, a total adjustment stroke of 40mm for the roller gap, and an adjustment frequency of once every 1 minute; Fourth stage (16-24 hours after casting): The working pressure of the rollers is gradually reduced to 8MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain was 0.75%, the hot crack rate was 0.38%, the central porosity grade was 0.9, the compositional segregation grade was 1.0, and the average corrosion rate in the corrosion resistance test was ≤0.012mm / a, which fully meets the usage standards for marine engineering equipment.

[0037] Example 4: 12Cr1MoV heat-resistant steel ultra-thick ingot (thickness 900mm); The ingot dimensions are 900mm × 2000mm × 2200mm, with a total ingot mold height of 2200mm, made of 3Cr2W8V material. The hydraulic roll assembly consists of 6 layers, with 8 hydraulic rolls evenly distributed around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 660mm high (30% of the total height) with a hydraulic roll spacing of 250mm; the middle part is 1210mm high (55% of the total height) with a hydraulic roll spacing of 220mm; and the lower part is 330mm high (15% of the total height) with a hydraulic roll spacing of 180mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 200mm, a roll length of 400mm, and a roll surface roughness Ra≤0.4μm.

[0038] The casting temperature is 1550-1580℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 20MPa, a cumulative total adjustment stroke of 15mm for the roller gap, and an adjustment frequency of once every 2 minutes; Second stage (3-8 hours after casting): The middle rollers of the ingot mold are activated to work in coordination, with the upper middle rollers working at a pressure of 35MPa, a cumulative total adjustment stroke of 30mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (8-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 45MPa for all rollers, a cumulative total adjustment stroke of 45mm for the roller gap, and an adjustment frequency of once every 1 minute; Fourth stage (16-24 hours after casting): The working pressure of the rollers is gradually reduced to 10MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain was 0.78%, the hot crack rate was 0.39%, the central porosity grade was 1.0, the compositional segregation grade was 1.0, and the high-temperature creep strength reached 180MPa under 550℃ and 1000h conditions, which fully meets the technical requirements of nuclear power equipment shells.

[0039] Example 5: Q345B low-alloy high-strength steel ultra-thick ingot (thickness 500mm); The ingot dimensions are 500mm × 1400mm × 2900mm, with a total ingot mold height of 2900mm, made of H13 material. The hydraulic roll assembly consists of four layers, with five hydraulic rolls evenly arranged around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 580mm high (accounting for 20% of the total height) with a hydraulic roll spacing of 290mm; the middle part of the ingot mold is 1885mm high (accounting for 65% of the total height) with a hydraulic roll spacing of 260mm; and the lower part of the ingot mold is 435mm high (accounting for 15% of the total height) with a hydraulic roll spacing of 200mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 140mm, a roll body length of 220mm, and a roll surface roughness Ra≤0.4μm.

[0040] The casting temperature is 1510-1540℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 18MPa, a cumulative total adjustment stroke of 9mm for the roller gap, and an adjustment frequency of once every 3 minutes; Second stage (3-7 hours after casting): The middle rollers of the ingot mold are activated to work in tandem, with the upper middle rollers working at a pressure of 28MPa, a cumulative total adjustment stroke of 20mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (7-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 38MPa for all rollers, a cumulative total adjustment stroke of 35mm for the roller gap, and an adjustment frequency of once every 1.5 minutes; Fourth stage (16-19 hours after casting): The working pressure of the rollers is gradually reduced to 6MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain is 0.65%, the hot crack rate is 0.30%, the central porosity grade is 0.8, the compositional segregation grade is 0.8, and the V-notch impact energy reaches 62J at -20℃, which is fully applicable to the production requirements of engineering machinery structural parts.

[0041] Example 6: 20CrMnTi gear steel ultra-thick ingot (thickness 550mm); The ingot dimensions are 550mm × 1600mm × 2700mm, with a total ingot mold height of 2700mm, made of 3Cr2W8V material. The hydraulic roll assembly consists of 5 layers, with 5 hydraulic rolls evenly arranged around the circumference of the ingot mold in each layer. The upper part of the ingot mold is 675mm high (accounting for 25% of the total height) with a hydraulic roll spacing of 270mm; the middle part of the ingot mold is 1620mm high (accounting for 60% of the total height) with a hydraulic roll spacing of 240mm; and the lower part of the ingot mold is 405mm high (accounting for 15% of the total height) with a hydraulic roll spacing of 200mm. The hydraulic rolls are made of tungsten carbide hard alloy, with a roll diameter of 150mm, a roll length of 260mm, and a roll surface roughness Ra≤0.4μm.

[0042] The casting temperature is 1530-1560℃, and the solidification process parameters are as follows: First stage (1-3 hours after casting): Only the upper hydraulic rollers of the ingot mold are activated, with a working pressure of 19MPa, a total adjustment stroke of 12mm for the roller gap, and an adjustment frequency of once every 2 minutes; Second stage (3-8.5 hours after casting): The middle rollers of the ingot mold are activated to work together, with a working pressure of 30MPa for the upper middle rollers, a total adjustment stroke of 22mm for the roller gap, and an adjustment frequency of once every 1 minute; Third stage (8.5-16 hours after casting): All hydraulic rollers are activated, with a working pressure of 40MPa for all rollers, a total adjustment stroke of 36mm for the roller gap, and an adjustment frequency of once every 1 minute; Fourth stage (16-23 hours after casting): The working pressure of the rollers is gradually reduced to 7MPa, maintaining the roller gap position until the ingot temperature drops below 800℃. The final ingot straightening strain is 0.68%, the hot crack rate is 0.32%, the central porosity grade is 0.9, the compositional segregation grade is 0.9, and the tooth surface hardness after gear machining reaches HRC58-62, which fully meets the requirements for use in heavy-duty vehicle gearbox gears.

[0043] The above embodiments demonstrate that the dynamic roll gap compensation solidification technology of the present invention can play a stable role in the production of ultra-thick ingots of different thicknesses and materials. Through flexible adjustment of process parameters, it can achieve precise control of solidification defects and is fully compatible with existing mold casting production lines, thus possessing significant industrial application value and promotion prospects.

[0044] This invention addresses core issues such as uneven solidification and bulging / cracking in ultra-thick ingots by regulating the deformation of the billet shell during solidification through a dynamic roll gap compensation mechanism. It can be widely applied in fields with stringent requirements for internal ingot quality and dimensional accuracy, such as heavy machinery, nuclear power equipment, and marine engineering. Specifically: For ultra-thick ingots (≥450mm), a dynamic roll gap compensation mechanism is introduced directly during the ingot casting stage to suppress bulging deformation of the billet shell at its source. Hydraulic roll assemblies are layered along the height of the ingot mold, and the roll spacing, working pressure, and adjustment frequency are differentiated according to the changes in billet shell strength in the early, middle, and late stages of solidification. Combined with a structural design that adapts the arc-shaped grooves on the roll surface to the curvature of the ingot's outer wall, uniform stress on the billet shell is achieved, avoiding localized stress concentration. Based on the real-time changes in the thickness and strength of the billet shell during the solidification process of ultra-thick ingots, the pressure, stroke, and adjustment frequency of the hydraulic rolls are flexibly adjusted: low pressure and short stroke in the early stage of solidification suppress bulging; medium pressure in the middle stage adapts to deformation; high pressure in the later stage precisely compensates for shrinkage; and pressure is reduced in the final stage to maintain shape and avoid secondary stress.

[0045] 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.

[0046] 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.

[0047] 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 dynamic roll gap compensation solidification device for ultra-thick die casting ingots, characterized in that, It includes a spindle mold, a support frame, and a hydraulic roll assembly. The hydraulic roll assembly is mounted around the spindle mold via the support frame. The hydraulic roll assembly is arranged in layers along the height direction of the spindle mold, and the hydraulic rolls in the same layer are evenly distributed along the circumference of the spindle mold.

2. The dynamic roll gap compensation solidification device for ultra-thick die casting ingots according to claim 1, characterized in that, The ingot mold is made of heat-resistant alloy steel, with an inner cavity thickness ranging from 450 to 900 mm and a height ranging from 1200 to 3000 mm. The inner wall of the ingot mold is coated with a silicon nitride-based heat-insulating coating with a thickness of 20 to 50 μm.

3. The dynamic roll gap compensation solidification device for ultra-thick die casting ingots according to claim 1, characterized in that, The vertical spacing between two adjacent hydraulic rolls is 180-300mm. Each hydraulic roll is equipped with an independent hydraulic drive unit. The working pressure range of the hydraulic system of the hydraulic drive unit is 15-45MPa. The roll gap adjustment stroke of the hydraulic roll is 0-45mm.

4. A dynamic roll gap compensation solidification device for ultra-thick die casting ingots according to claim 1 or 3, characterized in that, The longitudinal spacing of the hydraulic rollers at the top of the ingot die is 250-300mm; the longitudinal spacing of the hydraulic rollers in the middle of the ingot die is 200-250mm; and the longitudinal spacing of the hydraulic rollers at the bottom of the ingot die is 180-200mm.

5. A dynamic roll gap compensation solidification device for ultra-thick die casting ingots according to claim 4, characterized in that, The upper part of the ingot mold accounts for 20%-30% of the total height of the ingot mold, the middle part of the ingot mold accounts for 55%-65% of the total height of the ingot mold, and the lower part of the ingot mold accounts for 10%-15% of the total height of the ingot mold.

6. The dynamic roll gap compensation solidification device for ultra-thick die casting ingots according to claim 1, characterized in that, The hydraulic roll body is made of tungsten carbide hard alloy, with a roll diameter range of 120-200mm, a roll body length of 200-400mm, and a roll surface roughness Ra≤0.4μm.

7. A dynamic roll gap compensation solidification process for ultra-thick die casting ingots, characterized in that, The dynamic roll gap compensation solidification device for ultra-thick die casting ingots as described in any one of claims 1-6 is used to achieve this. The dynamic roll gap compensation solidification process is divided into four stages, and the shell thickness of each stage is the average shell thickness of the corresponding height region of the ingot mold. The first stage is 1-3 hours after casting, when the average shell thickness of the corresponding area is 50-100mm. Only the upper hydraulic rollers of the ingot mold are activated, and the working pressure is adjusted to 15-20MPa. The roller gap is adjusted every 2-3 minutes, and the total adjustment stroke of the roller gap is 5-15mm. The second stage is 3-8 hours after casting, when the average shell thickness in the corresponding area reaches 100-250mm. The hydraulic rollers in the middle and upper parts of the ingot mold are started to work together. The working pressure of the upper and middle rollers of the ingot mold is adjusted to 25-35MPa, the roller gap adjustment frequency is 1-2 times / minute, and the total cumulative adjustment stroke of the roller gap is 15-30mm. The third stage is 8-16 hours after casting, when the average shell thickness of the corresponding area is ≥250mm. All hydraulic rolls are started, and the working pressure of all hydraulic rolls is adjusted to 35-45MPa. The roll gap adjustment frequency is 0.5-1 times / minute, and the total cumulative adjustment stroke of the roll gap is 30-45mm. The fourth stage is 16-24 hours after casting, when the ingot core is completely solidified. The working pressure of all rolls is gradually reduced to 5-10 MPa, while keeping the roll gap position unchanged, until the overall temperature of the ingot drops below 800℃.

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