Heat-resistant steel casting process optimization method and casting process

Abstract

The invention relates to the technical field of heat-resistant steel casting, in particular to a heat-resistant steel casting process optimization method and a casting process. The casting process is simulated through multi-physics field coupling simulation, and whether a hot spot area or a shrinkage porosity phenomenon exists in a lower box of a sand mold or not is judged; and improving the preliminarily determined sand mold design scheme according to the simulation result, including adding a barb riser, adjusting the size of the barb riser and setting surrounding measures at the barb riser. Through the optimization measures, the casting process capable of effectively solving the problems of shrinkage cavities and shrinkage porosity of the thick and large part of the lower box of the heat-resistant steel casting is obtained, the casting quality and the production efficiency are remarkably improved, the process yield is remarkably improved, the hot spot size is completely eliminated, and the shrinkage cavity defect occurrence rate is remarkably reduced. Meanwhile, the casting technology is simulated through the multi-physical field simulation technology, the number of times of tests is reduced, raw materials are saved, and reliable technical guarantee is provided for precision casting of high-temperature parts.

Description

Technical Field

[0001] This invention relates to the field of heat-resistant steel casting technology, specifically to a method for optimizing heat-resistant steel casting process and a casting process. Background Technology

[0002] The structure of heat-resistant steel components such as turbine housings often contains multiple isolated thick sections. When manufacturing casting molds, it is inevitable that some of these thick sections will be located within the lower mold. Because risers in traditional casting methods are mostly located in the upper mold or on the side, the thick sections in the lower mold are far from the risers. Since heat-resistant steel has a wide solidification temperature range, heat spots form in the thick sections of the lower mold during solidification. This makes it impossible for traditional riser placement methods to effectively compensate for the shrinkage of these thick sections within the lower mold, resulting in defects such as shrinkage porosity and shrinkage cavities in the casting.

[0003] Some existing technologies use a combination of chills and insulation blocks to control the cooling sequence of heat-resistant steel. By attaching chills to the thick parts, the thick parts cool first, and insulation blocks are set in the feeding channels to keep the feeding channels unobstructed, thereby improving the temperature field of the casting. This allows the molten metal to replenish the thick parts through the feeding channels when they solidify.

[0004] However, in practical applications, this method is not ideal. While chills increase the cooling rate, they affect the final microstructure of the heat-resistant steel, and the rapid cooling of chills increases the risk of hot cracking. Heat-resistant steel has a wide solidification temperature range, and the fluidity of the molten metal decreases rapidly during solidification. When thick sections are not connected to the feeding channels, the riser feeding pressure is difficult to transmit to the center of the hot spot, resulting in ineffective replenishment of molten metal and defects such as shrinkage porosity and shrinkage cavities. Summary of the Invention

[0005] To address the technical problems of shrinkage porosity and shrinkage cavities in the thicker sections of the lower mold during the casting of heat-resistant steel, this application provides an optimization method and process for heat-resistant steel casting. The optimization method includes the following steps: S11. Based on the shape of the casting, determine the placement scheme of the casting, the structure of the upper and lower molds, set the distribution and size of the risers and the casting channels connecting each riser, establish the geometric model of the sand mold, and determine the sand mold design scheme in accordance with the principle of sequential solidification. S12. Based on the sand mold design scheme, the multi-physics field coupling simulation method is used to simulate the casting process to determine whether there is a hot spot area in the lower box of the sand mold. If so, a barbed riser is set at the lower box position corresponding to the hot spot area, and the barbed riser is connected to the casting channel or the casting cavity. S13. Re-simulate the casting process according to the improved sand mold design scheme. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, adjust the size of the barb riser. If not, output the improved sand mold design scheme. S14. Re-simulate the casting process based on the improved sand mold design. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, set up heat preservation measures at the connection between the barbed riser and the casting cavity, and output this sand mold design. If not, output the improved sand mold design.

[0006] Specifically, the presence of hot spot regions is determined through the following steps: S121. Calculate the overall average temperature of all units within the casting cavity; S122. Select one unit at a time, obtain the simulated temperature of the unit, calculate the absolute difference between the simulated temperature and the average temperature of the unit, and if the absolute difference is greater than the first threshold and the simulated temperature of the unit is greater than the average temperature, then mark the unit as a hot spot unit. S123. Repeat step S122 until all units participate in the calculation; S124. When the number of hot spot units is greater than the second threshold, and at least one hot spot unit has a common node with other hot spot units, it is determined that there is a hot spot region in the lower box. The unit referred to here is a unit in the finite element model of a sand mold.

[0007] Specifically, the size of the barbed riser is adjusted through the following steps: S131. Determine whether the size of the barbed riser exceeds the allowable value. If yes, set up heat preservation measures at the connection between the barbed riser and the casting cavity, and output this sand mold design scheme. If no, obtain the volume of the hot spot area and calculate the volume ratio of the hot spot area to the thick part. S132. The size of the barbed riser is enlarged according to the volume ratio of the hot spot area to the thick part.

[0008] Specifically, the volume of the hot spot region is obtained through the following steps: calculating the total volume of all the hot spot units, which is the volume of the hot spot region.

[0009] This invention also provides a heat-resistant steel casting process, which is obtained by optimizing the above methods and includes the following steps: S21. A sand mold is made according to the sand mold design scheme. The lower box of the sand mold is equipped with a barbed riser. The barbed riser is connected to the casting cavity and the casting flow channel. Insulation measures are provided at the connection between the barbed riser and the casting cavity. S22. Prepare a sand core and apply an anti-adhesion sand coating to the outer surface of the sand core; S23. Clean the cavity of the sand mold, place the sand core in the lower box, and seal the upper and lower boxes together. S24. Cast the casting, and remove and clean it after it cools.

[0010] The technical effects and advantages of this invention are as follows: By simulating the casting process using multiphysics coupling simulation, the existence of hot spots or shrinkage porosity in the lower mold box is determined. Based on the simulation results, the initially determined sand mold design is improved, including adding barbed risers, adjusting the size of the barbed risers, and implementing surrounding measures for the barbed risers. Through these optimization measures, a casting process is obtained that effectively solves the problems of shrinkage cavities and porosity in the thicker parts of the lower mold box of heat-resistant steel castings. This significantly improves casting quality and production efficiency, significantly increases the process yield, completely eliminates hot spots, and significantly reduces the incidence of shrinkage defects. Simultaneously, simulating the casting process using multiphysics simulation technology reduces the number of experiments, saves raw materials, and provides reliable technical support for the precision casting of high-temperature components. Attached Figure Description

[0011] Figure 1 The flowchart illustrates the casting process optimization method provided by this invention.

[0012] Figure 2 This is a schematic diagram of the sand box structure in the casting process provided by the present invention.

[0013] Figure 3 The results of flaw detection are shown for parts produced by conventional casting processes in Embodiment 1 of the present invention.

[0014] Figure 4 This is a porosity probability diagram based on the simulation results of the conventional casting process in Embodiment 1 of the present invention.

[0015] Figure 5 This is a porosity probability diagram based on the simulation results of the improved casting process in Embodiment 1 of the present invention.

[0016] Figure 6 The results of flaw detection are shown for the parts produced using the improved casting process in Embodiment 1 of the present invention.

[0017] Figure 7 The results of crack detection are for parts cast using conventional casting processes in Embodiment 2 of the present invention.

[0018] Figure 8 The temperature cloud map is a simulation result of the conventional casting process in Embodiment 2 of the present invention.

[0019] Figure 9 The temperature cloud map is a simulation result of the improved casting process in Embodiment 2 of the present invention.

[0020] The attached diagram is labeled as follows: 1. Casting cavity; 2. Casting runner; 3. Top riser; 4. Barbed riser; 41. Riser insulation sleeve. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The solidification characteristics and shrinkage behavior of heat-resistant steel differ significantly from those of ordinary steel. As a high-alloy steel, heat-resistant steel has a wider solidification temperature range and a broader solid-liquid coexistence region during solidification. This wide solidification range hinders the effective flow of liquid metal for compensating shrinkage, easily leading to shrinkage porosity and shrinkage cavities. Therefore, the application of sequential solidification principles is more crucial. Furthermore, within this broad solid-liquid region, the grain skeleton forms early but has low strength, and the liquid film persists for a long time, making it prone to cracking under shrinkage stress.

[0023] This invention provides a heat-resistant steel casting process that can solve the problems of shrinkage porosity and shrinkage cavities in the thicker parts of the lower mold during the casting of heat-resistant steel parts. The process includes the following steps: S21. The sand mold is made according to the sand mold design scheme. The lower box of the sand mold is equipped with a barbed riser. The barbed riser is connected to the casting cavity and / or the casting flow channel. The inlet where the barbed riser is connected to the casting cavity is equipped with heat preservation measures. S22. Prepare sand cores and apply anti-adhesion sand coating to the outer surface of the sand cores; S23. Clean the cavity of the sand mold, place the sand core in the lower box, and seal the upper and lower boxes together. S24. Cast the casting, and remove and clean it after it cools.

[0024] The process provided by this invention involves setting up a barbed riser near the hot spot region and connecting it to a branch structure of the casting runner. On one hand, turbulent molten metal can overflow from the barbed riser, improving airflow in the molten metal and effectively reducing porosity defects. On the other hand, considering the limited volume of the lower box, the size of the barbed riser cannot be set too large, making it difficult to ensure that the barbed riser solidifies last. Therefore, an insulation sleeve or heating sleeve can be set at the position of the barbed riser, allowing the casting runner to heat the barbed riser. By heating the barbed riser, the thermal modulus of the barbed riser is increased, delaying the solidification time of the barbed riser, and compensating for shrinkage in the hot spot region. This improves the shrinkage porosity defects in the thick part of the bottom of the lower box and increases the yield.

[0025] Furthermore, sand cores are divided into reference cores and auxiliary cores. Reference cores are used for positioning the casting to ensure casting accuracy. For example, the flow channel core of a turbine housing can serve as a reference core, with its axis used to determine the accuracy of the entire assembly. Auxiliary cores are used to fill in the gaps in complex features, such as the main oil passage, cooling water jacket, and exhaust passage. Auxiliary cores can also be combined with other measures to improve process defects. For example, a chromite sand chilling core can be built in to increase the cooling rate and prevent thermal cracking, or a zircon powder coating can be sprayed on the surface of the auxiliary core to solve the problem of sand adhesion and improve surface roughness. Water-soluble core material can also be placed inside the auxiliary core to facilitate sand removal during demolding.

[0026] Considering that different parts have different structures, the casting process and sand box design scheme need to be adjusted according to the geometric characteristics and technical requirements of the parts. If the casting process and sand box design scheme are determined solely by manual experience, a large number of casting experiments are required, which is time-consuming and labor-intensive.

[0027] refer to Figure 1 This invention provides a method for optimizing the casting process of heat-resistant steel, comprising the following steps: S11. Based on the shape of the casting, determine the placement scheme of the casting, the structure of the upper and lower molds, set the distribution and size of the risers and the casting channels connecting each riser, establish the geometric model of the sand mold, and determine the sand mold design scheme in accordance with the principle of sequential solidification. S12. Based on the sand mold design scheme, use the multi-physics field coupling simulation method to simulate the casting process and determine whether there is a hot spot area in the lower box of the sand mold. If so, set a barbed riser at the lower box position corresponding to the hot spot area and connect the barbed riser to the casting channel or casting cavity. S13. Re-simulate the casting process based on the improved sand mold design scheme. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, adjust the size of the barb riser. If not, output the improved sand mold design scheme. S14. Re-simulate the casting process based on the improved sand mold design. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, set up heat preservation measures at the connection between the barbed riser and the casting cavity, and output this sand mold design. If not, output the improved sand mold design.

[0028] This method uses finite element analysis to simulate the casting process, determining the rationality of the mold structure. Through the aforementioned optimization measures, this invention successfully solves the problems of shrinkage cavities and porosity in the thicker parts of the lower mold of heat-resistant steel castings, significantly improving casting quality and production efficiency. The process yield is significantly increased, hot spot volume is completely eliminated, and the incidence of shrinkage cavities is significantly reduced. Simultaneously, multiphysics simulation technology is used to simulate the casting process, reducing the number of experiments and saving raw materials, providing reliable technical support for the precision casting of high-temperature components.

[0029] Specifically, riser dimensions are generally calculated using the modulus method. The modulus is the ratio of the volume of the solidified solid to the surface area for heat dissipation, denoted by the symbol M. The modulus is an important parameter for calculating risers, and it is usually slightly larger than the modulus of the solidified solid, typically taken as 1.1-1.2 times.

[0030] Multiphysics coupled simulation (MPS) simulates the flow pattern, temperature change, and shrinkage process of molten metal by coupling the flow field, temperature field, and stress field. Based on the finite element method (FEM), it simplifies the calculation process by dividing the complex geometric model into multiple simple-shaped elements. It establishes the equation of state for the molten metal using fundamental theories of thermodynamics and fluid mechanics, and iteratively solves the casting process using numerical analysis. This method is now widely used in casting simulation. Existing MPS casting simulation software includes ProCAST, COMSOL, MAGMASOFT, SuperCAST, and ANSYS Workbench. These simulation software programs integrate modules such as finite element mesh generation, thermal analysis, fluid analysis, stress analysis, and microstructure analysis. They can simulate the flow conditions during metal casting and analyze phenomena such as incomplete filling, cold shuts, gas entrapment, shrinkage porosity, and shrinkage cavities. The calculation results not only provide data such as the temperature and flow rate of the molten metal at each moment during the casting process, but also the probability of shrinkage porosity or shrinkage cavities in the casting (e.g., ...). Figure 4 and Figure 5 As shown in the figure, this provides a reliable basis for evaluating the casting process.

[0031] Generally, based on experience, for most projects, areas with a porosity greater than 92% in the calculation results will produce shrinkage cavities that do not meet quality requirements during actual casting. In some projects with high requirements for casting quality, the porosity requirement is much lower; in some projects, areas with a porosity greater than 80% in the simulation results will produce shrinkage cavities that fail to meet quality requirements during actual casting. Therefore, in steps S13 and S14, the criterion for determining whether shrinkage porosity has occurred can be whether the porosity of the hot spot area is greater than 92%. If so, shrinkage porosity exists.

[0032] Based on the simulation results of multiphysics coupled casting, it is possible to determine whether a hot spot region exists in the lower box, as well as the location and volume of the hot spot region. Specifically, the following steps are included: S121. Calculate the overall average temperature of the unit inside the casting cavity; S122. Select one unit at a time, obtain the simulated temperature of the unit, calculate the absolute difference between the simulated temperature and the average temperature of the unit, and if the absolute difference is greater than the first threshold and the simulated temperature of the unit is greater than the average temperature, then mark the unit as a hot spot unit. S123. Repeat step S122 until all units participate in the calculation; S124. When the number of hot spot units is greater than the second threshold, and at least one hot spot unit has a common node with other hot spot units, it is determined that there is a hot spot in the lower box.

[0033] The element referred to here is the element in the finite element model generated after the geometric model of the sand mold is meshed.

[0034] When identifying hot spot regions, the cooling rate of these regions is significantly slower compared to other regions. Therefore, while the temperature of other regions has already dropped below the solidus temperature, the temperature of the hot spot region remains much higher. Thus, determining the location of hot spot regions through temperature comparison can balance computational speed and accuracy. Simultaneously, the accuracy of mesh generation significantly impacts the results for each element, and abrupt changes in geometry can lead to large deviations between the results and the actual values ​​at the abrupt locations. Therefore, when identifying hot spot regions, it's crucial to determine if there are multiple hot spot elements. If only one or two elements exhibit unusually high temperatures, it indicates an anomaly caused by the mesh generation accuracy. The value of the second threshold depends not only on the mesh generation accuracy but also on the shape of the hot spot region. When the mesh size is small, the hot spot region should contain more elements. Conversely, when the mesh size is large, the number of elements in the hot spot region may decrease.

[0035] When determining hot spot units, the first threshold value can generally be set as the absolute difference between the solidus temperature of the heat-resistant steel and the overall average temperature. The hot spot region identification step can be performed after most areas of the casting have completed solidification. Specifically, the hot spot determination procedure can be triggered when the number of units with temperatures lower than the solidus temperature accounts for 90% of the total number of units. Since the solidification principle of heat-resistant steel is sequential solidification, risers are usually the last to solidify in order to ensure the feeding effect of the riser on the casting. Therefore, when the interior of the casting has completed solidification, some molten metal may still be present at the riser location.

[0036] After determining from the simulation results that a hot spot region exists inside the lower box, the size of the barbed riser needs to be adjusted, specifically including the following steps: S131. Determine whether the size of the barbed riser exceeds the allowable value. If so, set up insulation measures at the connection between the barbed riser and the cavity, and output the sand mold design scheme. If not, obtain the volume of the hot spot area and calculate the volume ratio of the hot spot area to the thick part. S132. The size of the barbed riser is enlarged according to the volume ratio of the hot spot area to the thick part.

[0037] For example, when the volume of the hot spot region accounts for 20% of the thick part, the size of the barbed riser can be increased by 1.2 times.

[0038] Specifically, the volume of the hot spot region can be calculated based on the total volume of all hot spot units in step S125.

[0039] The size of the barbed riser is generally limited by the size of the sand box. In addition, the size of the barbed riser is generally calculated according to the modular method and is at least 1.1-1.2 times the size of the solidified solid. Therefore, the allowable value of the barbed riser size needs to be determined according to the shape of the casting and the size of the sand box.

[0040] The modulus of solidified solids with complex shapes is often difficult to calculate accurately, which poses a challenge to determining the size of the barbed riser. Furthermore, the feeding effect of the barbed riser on the hot spot region is generally related to the fluidity of the molten metal in the feeding channel; the better the fluidity of the molten metal, the better the feeding effect on the hot spot region. Therefore, appropriately increasing the size of the barbed riser can delay the cooling of the molten metal within the riser and improve its feeding effect on the hot spot region.

[0041] Example 1 The turbine housing casting process for a certain project uses a wet sand casting production line with 8 cavities per mold. The casting forms a thick section on the bolt platform inside the lower box, where conventional casting processes would result in porosity and shrinkage. Figure 3 (As shown in the red box in the image), the maximum length of a single hole in the cut part was 1.41 mm, the maximum crack length was 2.66 mm, and the scrap rate was 45%.

[0042] The casting process is optimized through the following steps: 1) Initial process modeling: Based on the three-dimensional model of the turbine housing, the mold is initially designed, the initial riser size is calculated according to the modular method, and the chill system is arranged. Chromite chills are attached around the thick parts of the lower box. 2) Set the material parameters. The heat-resistant steel is ZG40Cr25Ni20, with a liquidus temperature of 1480℃ and a solidus temperature of 1360℃. Use multiphysics coupling simulation software to perform thermodynamic analysis, simulate the casting process, detect two hot spots, and generate a temperature gradient cloud map to mark high-risk areas.

[0043] 3) Install a barbed riser at the hot spot at the bottom of the lower chamber, and connect the barbed riser to the vertically installed feeding channel to facilitate fire intake. (Refer to...) Figure 2 .

[0044] 4) When the second simulation was performed, the hot spot in the thick part at the bottom of the lower box disappeared.

[0045] 5) Make a wet sand mold with a hardness of 85-90. Control the casting temperature at 1530±10℃. Set an insulating riser at the bottom hook riser to keep the feeding channel unobstructed.

[0046] 6) After the casting has completely cooled, the sample was cut and subjected to fluorescent flaw detection. No obvious cracks or shrinkage cavities were found.

[0047] Figure 4 The simulation results of traditional casting process are shown. The red circle in the figure indicates a hot spot area, which leads to shrinkage porosity. It can be seen that this hot spot area is located inside the lower mold, and the conventional top riser is too far from this location to effectively compensate for shrinkage. This application sets a barbed riser near this area and connects the barbed riser to the branch structure of the casting runner. On the one hand, the turbulent molten metal can overflow from the barbed riser, improving the airflow in the molten metal and effectively improving porosity defects. On the other hand, an insulation sleeve or heating sleeve can be set at the barbed riser location, allowing the casting runner to heat the barbed riser. Considering the limited volume of the lower mold, the size of the barbed riser cannot be set too large, making it difficult to ensure that the barbed riser solidifies last. By heating the barbed riser, the thermal modulus of the barbed riser is increased, delaying the solidification time of the barbed riser and compensating for shrinkage at the hot spot location.

[0048] Simulations were performed on the modified sand mold and casting process, such as... Figure 5 As shown, the original hot spot area disappeared, and the shrinkage porosity defect was improved. This was demonstrated through actual casting samples, such as... Figure 6 As shown, the sample has no shrinkage porosity or shrinkage cavity defects, and the scrap rate of parts cast by this process is reduced to 0.14%.

[0049] Example 2 The heat-resistant steel shell casting process for a certain project uses a two-cavity mold, with the lower ferrule located at the bottom of the lower mold. Conventional casting methods resulted in severe shrinkage cavities. The largest single hole in the casting had a length of 1.41 mm, and the largest crack length was 2.66 mm. Figure 7 As shown, the scrap rate for conventional processes is 35%.

[0050] The process is optimized using the method provided by this invention, and the specific steps are as follows: 1) Arrange risers and gating system in NX according to the casting CAD model, and set riser dimensions according to the modular method; 2) Solidification simulation was performed using casting simulation software based on the material parameters of the heat-resistant steel, revealing an 8.7cm gap at the bottom of the lower mold. 3 The hot spot area is located close to the shrinkage cavity and crack location (reference). Figure 8 ).

[0051] 3) Modify the position and size of the riser, and set up a fire-injection mechanism at the position of the barbed riser, then re-perform the simulation; 4) After three iterations of simulation, the hot spot volume was reduced to 0.08 cm³. 3 (refer to Figure 9 ), determine the location and size of the riser and the fire-starting measures.

[0052] 5) The pouring temperature is controlled at 1580±10℃, and the molding sand is preheated to 180℃ before pouring.

[0053] 6) After pouring, the pressure was maintained for 12 minutes, and a uniform depression appeared at the neck of the riser. The casting was removed and cut for flaw detection, and no obvious defects were found.

[0054] After the above process improvements, the scrap rate of this part was reduced to almost zero.

[0055] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the casting process of heat-resistant steel, characterized in that, Includes the following steps: S11. Based on the shape of the casting, determine the placement scheme of the casting, the structure of the upper and lower molds, set the distribution and size of the risers and the casting channels connecting each riser, establish the geometric model of the sand mold, and determine the sand mold design scheme in accordance with the principle of sequential solidification. S12. Based on the sand mold design scheme, the multi-physics field coupling simulation method is used to simulate the casting process to determine whether there is a hot spot area in the lower box of the sand mold. If so, a barbed riser is set at the lower box position corresponding to the hot spot area, and the barbed riser is connected to the casting channel or the casting cavity. S13. Re-simulate the casting process according to the improved sand mold design scheme. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, adjust the size of the barb riser. If not, output the improved sand mold design scheme. S14. Re-simulate the casting process based on the improved sand mold design. Determine whether there is shrinkage porosity in the hot spot area based on the simulation results. If so, set up heat preservation measures at the connection between the barbed riser and the casting cavity, and output this sand mold design. If not, output the improved sand mold design.

2. The method according to claim 1, characterized in that, Determine if a hot spot region exists by following these steps: S121. Calculate the overall average temperature of all units within the casting cavity; S122. Select one unit at a time, obtain the simulated temperature of the unit, calculate the absolute difference between the simulated temperature and the average temperature of the unit, and if the absolute difference is greater than the first threshold and the simulated temperature of the unit is greater than the average temperature, then mark the unit as a hot spot unit. S123. Repeat step S122 until all units participate in the calculation; S124. When the number of hot spot units is greater than the second threshold, and at least one hot spot unit has a common node with other hot spot units, it is determined that there is a hot spot region in the lower box. The unit referred to here is a unit in the finite element model of a sand mold.

3. The method according to claim 2, characterized in that, The first threshold is the absolute difference between the overall average temperature and the solid phase temperature of the heat-resistant steel.

4. The method according to claim 1, characterized in that, The insulation measure is an insulating riser or a heating riser.

5. The method according to claim 2, characterized in that, In step S13, the size of the barbed riser is adjusted through the following steps: S131. Determine whether the size of the barbed riser exceeds the allowable value. If yes, set up heat preservation measures at the connection between the barbed riser and the casting cavity, and output this sand mold design scheme. If no, obtain the volume of the hot spot area and calculate the volume ratio of the hot spot area to the thick part. S132. The size of the barbed riser is enlarged according to the volume ratio of the hot spot area to the thick part.

6. The method according to claim 5, characterized in that, The volume of the hot spot region is obtained by the following steps: calculate the total volume of all the hot spot units, which is the volume of the hot spot region.

7. A heat-resistant steel casting process, characterized in that, The process is obtained by the method according to any one of claims 1-6, and the process includes the following steps: S21. A sand mold is made according to the sand mold design scheme. The lower box of the sand mold is equipped with a barbed riser. The barbed riser is connected to the casting cavity and the casting flow channel. Insulation measures are provided at the connection between the barbed riser and the casting cavity. S22. Prepare a sand core and apply an anti-adhesion sand coating to the outer surface of the sand core; S23. Clean the cavity of the sand mold, place the sand core in the lower box, and seal the upper and lower boxes together. S24. Cast the casting, and remove and clean it after it cools.

8. The process according to claim 7, characterized in that, The sand core is divided into a reference core and an auxiliary core. The reference core is used for positioning the casting, and the auxiliary core is used for filling in complex features.

9. The process according to claim 8, characterized in that, The outer surface of the auxiliary core is coated with zircon powder.

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