A casting process for large high temperature alloy castings with non-metallic inserts
By replacing metal subsidies with heated cores and optimizing temperature gradients and feeding angles using numerical simulations, the problem of difficult removal of metal subsidies in the casting of large high-temperature alloy parts was solved, improving production efficiency and casting quality while reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA ERZHONG GRP DEYANG HEAVY IND
- Filing Date
- 2025-04-29
- Publication Date
- 2026-07-24
Smart Images
Figure CN120480135B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-temperature alloy casting technology, and specifically to a casting process for non-metallic fittings of large high-temperature alloy castings. Background Technology
[0002] Coal-fired power generating units include cylinder and valve body castings, which are mostly made of ferritic steel with a Cr content of 9-12 wt%. The temperature parameters have reached 630℃, which is the limit of the temperature parameters of this type of iron-based material. To break through the temperature parameters of 650℃ and above, new alloy materials that are more resistant to high-temperature oxidation and corrosion need to be used, such as new nickel-based and iron-nickel-based alloy materials with Ni ≥ 20 wt%.
[0003] Currently, traditional iron-based material casting process subsidy design all adopt the method of thickening parts with metal subsidies to adjust the solidification temperature field of the casting, establish a sequential solidification feeding channel, and ensure the internal quality of the product. Then, the metal is removed by hot cutting, air gouging or machining. Manufacturing cylinder and valve body castings based on metal subsidies and using traditional iron-based materials is a mature process technology.
[0004] However, compared to traditional iron-based materials, new high-temperature alloy materials have significant advantages in high-temperature performance for ultra-supercritical units at 620℃ and above. However, the following problems exist in the manufacturing of large cylinders and valve bodies: 1. High-temperature alloys have a higher alloy content than iron-based materials, and the metal trimmings become slag after cutting, which cannot be recycled, resulting in higher manufacturing costs; 2. High-temperature alloy materials have a large coefficient of thermal expansion, making them prone to cracking. Using hot cutting to remove metal trimmings can lead to product cracking, high rework costs, and a significant risk of scrapping; 3. High-temperature alloys are austenitic materials with poor thermal conductivity, easily causing tool sticking during machining, resulting in low efficiency in removing metal trimmings through machining. Currently, there are no corresponding methods, domestic or international, to efficiently solve the problem of removing metal trimmings from high-temperature alloy castings.
[0005] In the prior art, CN114951553A, CN117816937A, CN117444182A, etc., all disclose the use of heat-generating materials to make non-metallic subsidies during the casting process to replace metal subsidies and achieve the effect of post-casting detachment. However, non-metallic subsidies are often used for casting small castings, such as pipes and fans. Whether they can be adapted to casting large castings with multiple curved surfaces and multiple heat points is still challenging. In particular, new alloy materials that are more resistant to high-temperature oxidation and corrosion are more likely to form casting defects due to casting heat points. Summary of the Invention
[0006] This invention provides a casting process for non-metallic subsidies in large high-temperature alloy castings. It not only solves the problem of difficult subsidy removal during the casting of large high-temperature alloy castings, but also avoids new casting defects caused by non-metallic subsidies replacing metallic subsidies through sequential solidification simulation, thereby improving the production efficiency of large high-temperature alloy castings and reducing production costs.
[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:
[0008] A casting process for non-metallic fittings on large high-temperature alloy castings includes the following steps:
[0009] S1: Construct a casting simulation model and determine the location of hot spots through numerical simulation;
[0010] S2: Construct a heating core model based on the characteristics of the heating material and the heating subsidy shrinkage slope of 1:5 to 8, and simultaneously construct a metal subsidy model with a shrinkage slope of 1:10;
[0011] S3: Compare the temperature gradients of the heating core model and the metal-applied model through numerical simulation; when the temperature gradient of the heating core model is greater than or equal to that of the metal-applied model and no shrinkage defects are shown, save the modular parameters of the heating core; otherwise, iteratively adjust the parameters of the heating core model until the standard is met.
[0012] S4: Fabricate the core box according to the modular parameters, fill it with heating material, and shape the heating core.
[0013] S5: Position the heating core in the hot section feeding channel in the mold, fill it with sand and dry it to obtain a sand mold, and then pour the high-temperature alloy melt.
[0014] S6: After the casting cools, the core collapses on its own, and the internal density is verified by non-destructive testing.
[0015] In one specific embodiment of the present invention, the large high-temperature alloy casting has a weight ≥5t and a wall thickness ≥100mm.
[0016] In one specific embodiment of the present invention, the large high-temperature alloy casting is a large iron-nickel-based or nickel-based cast steel casting with Ni ≥ 20wt%.
[0017] In one specific embodiment of the present invention, step S1, the numerical simulation is based on numerical simulation software to simulate the sequential solidification process.
[0018] In one specific embodiment of the present invention, in steps S2 and S4, the maximum combustion temperature of the heating material is ≥1500℃, the combustion duration is ≥50s, and the bulk density is 0.7~1.2g / cm³. 3 .
[0019] In one specific embodiment of the present invention, in steps S2 and S4, the heating core is formed by mixing and molding a heating material and a curing agent; the tensile strength after curing for 24 hours after mixing is ≥0.4MPa; in the heating material, Al2O3 powder ≥38wt% and aluminum powder ≥20wt%; preferably, an alcohol-based coating with a thickness ≥1mm is applied to the surface of the shaped heating core.
[0020] In one specific embodiment of the present invention, the curing agent is any one or more of alkali-phenolic resin, Piper resin, and water glass.
[0021] In one specific embodiment of the present invention, in step S5, the heating core is fixed in the sand mold by pre-embedding or core placement.
[0022] In one specific embodiment of the present invention, in step S5, the drying temperature is 100-200°C and the drying time is 8-20 hours.
[0023] In one specific embodiment of the present invention, in step S5, the casting temperature of the high-temperature alloy is 1450-1550°C.
[0024] The beneficial effects of this invention are: 1. This invention solves the problem that traditional metal linings are difficult to remove after casting large high-temperature alloy castings, improves production efficiency and saves manufacturing costs, and provides a new direction for casting process design;
[0025] 2. This invention reduces the consumption of high-temperature alloy raw materials by replacing metal subsidies with heating cores, reduces the need for debonding and filling processes, lowers quality risks, and enhances the core competitiveness of enterprises.
[0026] 3. This invention can be widely applied to all high-temperature alloy castings and cast steel parts, and will create greater social and economic value in future applications.
[0027] 4. The heating core of this invention can improve the casting process accuracy and reduce the actual casting difference through numerical simulation, solve the problem of insufficient adaptability of the traditional single feeding method to complex hot spots, and improve the feeding efficiency.
[0028] 5. This invention ensures that the shrinkage compensation effect of the heating core is no less than that of the metal patch by comparing temperature gradients and iteratively adjusting the heating core model, thus avoiding shrinkage porosity and shrinkage defects.
[0029] 6. The casting process of this invention uses non-metallic subsidies to replace metallic subsidies, and combines non-destructive testing to comprehensively reduce material and labor costs. Attached Figure Description
[0030] Figure 1 A three-dimensional structural schematic diagram of an iron-nickel-based high-pressure inner cylinder model provided for a specific embodiment of the present invention;
[0031] Figure 2 Temperature gradient diagram of metal subsidy provided for specific embodiments of the present invention;
[0032] Figure 3 Temperature gradient diagram of non-metallic subsidy provided for specific embodiments of the present invention;
[0033] Figure 4 A three-dimensional schematic diagram of the core box used to fabricate the heating core of the cast iron-nickel-based high-pressure inner cylinder, provided for a specific embodiment of the present invention.
[0034] Figure 5 A three-dimensional structural diagram of the heating core of a cast iron-nickel-based high-pressure inner cylinder provided for a specific embodiment of the present invention;
[0035] Figure 6 A schematic diagram of the mold structure for a cast iron-nickel-based high-pressure inner cylinder provided for a specific embodiment of the present invention.
[0036] The attached diagram lists the components represented by each number as follows:
[0037] 1. Iron-nickel based high-pressure inner cylinder model; 2. Non-metallic patch; 3. Sand box; 4. Sand mold; 5. Mold cavity; 6. Riser; 7. Heating core. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0039] Cast as attached Figure 1 Taking the iron-nickel-based high-pressure inner cylinder shown as an example, a casting process for non-metallic padding of large high-temperature alloy castings is provided, including the following steps:
[0040] S1: Construct a casting simulation model and determine the location of hot spots through numerical simulation;
[0041] Determining the location of hot spots facilitates the structural design of the heating core in subsequent steps, ensuring that the heating core can improve the temperature gradient at the hot spot location by adjusting the feeding process, thereby avoiding casting defects such as shrinkage and shrinkage cavities that are easily caused by hot spots during actual casting. Specifically, numerical simulation involves inputting the casting simulation model into numerical simulation software to simulate the sequential solidification process, thereby determining the location of hot spots. The sequential solidification process is based on the principle of sequential solidification, which involves placing risers and other process measures in thick areas of the casting where shrinkage cavities may occur, so that the parts of the casting far from the riser solidify first, then the parts close to the riser solidify, and finally the riser itself solidifies.
[0042] As attached Figure 1 As shown, after determining the hot spot location of the iron-nickel based high-pressure inner cylinder model 1, the feeding riser was also determined simultaneously. Conventional casting process designs a metal patch on the feeding channel side between the feeding riser and the hot spot location; this casting process designs a non-metallic patch 2 at the same location as the metal patch. The surface structure of the non-metallic patch 2 that fits against the side of the feeding channel should be no different from the surface structure of the metal patch after cutting.
[0043] S2: Construct a heating core model based on the characteristics of the heating material and the heating subsidy shrinkage slope of 1:5 to 8, and simultaneously construct a metal subsidy model with a shrinkage slope of 1:10;
[0044] The feeding slope refers to the inclination ratio of the cross-sectional dimensions of the feeding channel as it gradually changes along its length. For example, a feeding slope of 1:10 means that for every 10 units of length increase, the cross-sectional width or height of the feeding channel increases by 1 unit. The heating core model and the metal applicator model are designed in the numerical simulation software based on the feeding slope during the sequential solidification process. A 1:10 feeding slope is used to design the metal applicator model, and a 1:8 feeding slope is used to design the heating core model. After verifying the temperature gradient in step S3, if the heating core model does not meet the requirements, the feeding slope of the heating applicator is iteratively increased until the heating core model... The improvement in temperature gradient at hot spot locations is greater than or equal to that of the metal-subsidized model. This method allows for the rapid determination of the structural parameters of the heating core model, reducing the design cost of replacing the "metal-subsidized" model with the "heating core" and improving efficiency. Saving the structural parameters of the heating core model can also provide a basis for subsequent numerical simulations of other similar large high-temperature alloy castings. The number of heating core models corresponds to the number of metal-subsidized models. Since large high-temperature alloy castings may have multiple hot spot locations in numerical simulations, and each hot spot location can have its own feeding riser and metal subsidy designed, the heating core model needs to correspond to the metal-subsidized model.
[0045] S3: Compare the temperature gradients of the heating core model and the metal-applied model through numerical simulation; when the temperature gradient of the heating core model is greater than or equal to that of the metal-applied model and no shrinkage defects are shown, save the modular parameters of the heating core; otherwise, iteratively adjust the shrinkage slope parameters until the standard is met.
[0046] Metal-applied models are a mature process method that improves defects such as shrinkage and shrinkage cavities in large high-temperature alloy castings with multiple curved surfaces and hot spots by extending the feeding distance of the riser. In contrast, heated core models primarily extend the feeding time of the riser through heating, aiming to improve defects such as shrinkage and shrinkage cavities. However, the heating temperature, heating duration, and strength of the heated core all affect the effectiveness of extending the feeding time of the riser, easily leading to obstruction of the feeding channel due to solidification. Comparing the temperature gradients of heated core models and metal-applied models through numerical simulation can prevent solidification obstruction due to insufficient feeding time extended by the heated core model, thus improving the adaptability of heated core models and the reliability of the process.
[0047] During numerical simulation comparison, a metal applicator model and a heating core model are added to the casting simulation model respectively. The heating core model is added to the same position as the metal applicator model in the casting simulation model to eliminate the randomness caused by the different positions, reduce the error of numerical simulation comparison, and improve the accuracy.
[0048] As attached Figure 2 , 3 As shown, the temperature gradient diagram of the sequential solidification process after the addition of the metal-subsidized model is numerically simulated, and then the temperature gradient diagram of the sequential solidification process after the addition of the non-metal-subsidized model is numerically simulated. Based on the two temperature gradient diagrams, it is determined that the improvement effect of the heating core model on the temperature gradient at the hot spot position is greater than or equal to the improvement effect of the metal-subsidized model on the temperature gradient at the hot spot position, and the heating core model satisfies the sequential solidification process after its addition. In this case, the structured parameters of the heating core model are modularly saved. Otherwise, it is necessary to iteratively adjust the sloping angle parameters and redesign the heating core model. The redesigned heating core is then compared through numerical simulation until the heating core meets the requirements, and the structural parameters of the heating core are modularly saved.
[0049] The modular parameters of the heating core include, but are not limited to, the size, dimensions and material of the heating core; if there are multiple heating core models, the modular parameters of each heating core model are saved separately for subsequent actual modeling and to achieve standardization and rapid production of large high-temperature alloy castings.
[0050] During the simulation comparison, the material of the heating core was set to a newly created heating material.
[0051] S4: Fabricate the core box according to the modular parameters, fill it with heating material, and shape the heating core.
[0052] To facilitate the molding of the heating core and its removal from the core box, the core box is designed with core slots according to the size and dimensions of the heating core. After molding is completed, the heating core is demolded from the core box, the dimensions of the heating core are checked, and compared with the stored modular parameters to confirm that the dimensions of the heating core are qualified for casting.
[0053] The modular parameters of the heating core were obtained through numerical simulation of the iron-nickel based high-pressure inner cylinder model 1. A three-dimensional structural schematic diagram of the core box fabricated from it is attached. Figure 4 As shown in the attached diagram, a three-dimensional structural schematic of the heating core 7, which is prepared by filling the heating material into the core box, is also included. Figure 5 As shown.
[0054] S5: Position the heating core in the hot section feeding channel in the mold, fill it with sand and dry it to obtain a sand mold, and then pour the high-temperature alloy melt.
[0055] The heating core is positioned in the same way as the hot section feeding channel and the metal applicator to reduce positioning differences that could affect the casting quality of the casting.
[0056] See appendix Figure 5 The mold shown is filled with molding sand in the sand box 3 to form the sand mold 4 required for casting the iron-nickel-based high-pressure inner cylinder. The sand mold 4 has a cavity 5 and a riser 6. The heating core 7 obtained in step S4 is positioned at the position of the hot section feeding channel and fixed. Then the filling sand is dried to obtain the sand mold. Finally, it is poured and solidified sequentially to obtain the iron-nickel-based high-pressure inner cylinder.
[0057] S6: After the casting cools, the core collapses on its own, and the internal density is verified by non-destructive testing.
[0058] Since the casting solidifies after casting, the heating core will spontaneously disintegrate and fall off during the mold-making process. However, it is still unknown whether the heating core completely prevents defects caused by thermal knots in the casting. Non-destructive testing can detect whether there are defects such as shrinkage and shrinkage cavities inside the casting, and thus evaluate the casting effect of the heating core. Of course, the results of non-destructive testing can be used as a basis for training the heating core model, which is beneficial to the optimization of the non-metallic auxiliary casting process for large high-temperature alloy castings, and can improve the efficiency and quality of casting large high-temperature alloy castings based on non-metallic auxiliary casting.
[0059] In some instances, the large high-temperature alloy castings weigh ≥5t and have a wall thickness ≥100mm.
[0060] In some instances, the large high-temperature alloy castings are large iron-nickel-based cast steel castings with Ni ≥ 20 wt%.
[0061] In some instances, step S1, the numerical simulation, is based on numerical simulation software to simulate a sequential solidification process.
[0062] In some instances, steps S2 and S4, to ensure that the non-metallic material reduces shrinkage defects caused by thermal knots, require the heating material to have a maximum combustion temperature ≥1500℃, a combustion duration ≥50s, and a bulk density of 0.7~1.2g / cm³. 3 It should be noted that the combustion temperature and duration of the heating material will affect the feeding effect in the actual casting process of large high-temperature alloy castings. Low combustion temperature and short duration can easily lead to insufficient heating during the entire solidification process, resulting in casting defects in actual large high-temperature alloy castings due to heat spots.
[0063] In some instances, in steps S2 and S4, the heating core is formed by mixing and molding a heating material and a curing agent;
[0064] In some cases, the ratio of heating material to curing agent is determined based on the tensile strength ≥ 0.4 MPa after mixing and hardening for 24 hours, in order to ensure the strength of the prepared heating core during the casting process and avoid casting dimensional deviations.
[0065] In some instances, the heating material contains ≥38 wt% Al2O3 powder and ≥20 wt% aluminum powder; specifically, the heating material contains 38–80 wt% Al2O3 powder and 20–62 wt% aluminum powder by mass; the heating material also includes 0–42 wt% minor components that generate or do not generate heat.
[0066] In some instances, an alcohol-based coating with a thickness of ≥1 mm is applied to the surface of the heated core after molding.
[0067] In some instances, the curing agent is any one or more of alkali-phenolic resin, apigenin, and water glass.
[0068] In some instances, in step S5, the heating core is fixed in the sand mold by pre-embedding or core placement; the heating core is exposed on the surface of the sand mold cavity, and its circumferential edge needs to be fixed during or before the sand filling process to prevent its circumferential edge from contacting the poured high-temperature alloy melt, to prevent erosion from damaging the structure of the heating core, to ensure the casting dimensions, and to prevent the mixing of heating materials into the casting to form defects.
[0069] In some instances, in step S5, the drying temperature is 100–200°C, and the drying time is 8–20 hours.
[0070] In some instances, in step S5, the casting temperature of the high-temperature alloy is 1450–1550°C.
[0071] This invention uses numerical simulation to quickly and cost-effectively determine the structure of non-metallic subsidies and replace them in casting large high-temperature alloy castings. On the one hand, it overcomes the problem of difficult removal of metal subsidies; on the other hand, non-metallic subsidies can detach themselves during the casting process, improving the production efficiency of large high-temperature alloy castings and saving manufacturing costs, providing a new direction for casting process design. Furthermore, numerical simulation of the heating core can improve casting process accuracy, reduce actual casting differences, solve the problem of insufficient adaptability of traditional single feeding methods to complex hot spots, and improve feeding efficiency.
Claims
1. A casting process for non-metallic fittings on large high-temperature alloy castings, characterized in that, The large high-temperature alloy casting is a large iron-nickel-based or nickel-based cast steel casting with Ni ≥ 20wt%, weighing ≥ 5t and having a wall thickness ≥ 100mm. The casting process includes the following steps: S1: Construct a casting simulation model and determine the location of hot spots through numerical simulation; S2: Construct a heating core model based on the characteristics of the heating material and the heating subsidy shrinkage slope of 1:5 to 8, and simultaneously construct a metal subsidy model with a shrinkage slope of 1:10; S3: Compare the temperature gradients of the heating core model and the metal-applied model through numerical simulation; when the temperature gradient of the heating core model is greater than or equal to that of the metal-applied model and no shrinkage defects are shown, save the modular parameters of the heating core; otherwise, iteratively adjust the parameters of the heating core model until the standard is met. S4: Fabricate the core box according to the modular parameters, fill it with heating material, and shape the heating core. S5: Position the heating core in the hot section feeding channel in the mold, fill it with sand and dry it to obtain a sand mold, and then pour the high-temperature alloy melt. S6: After the casting cools, the core collapses on its own, and the internal density is verified by non-destructive testing.
2. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: Step S1, the numerical simulation is based on numerical simulation software to simulate the sequential solidification process.
3. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: In steps S2 and S4, the maximum combustion temperature of the heating material is ≥1500℃, the combustion duration is ≥50s, and the bulk density is 0.7~1.2g / cm³. 3 .
4. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: In steps S2 and S4, the heating core is formed by mixing and molding a heating material and a curing agent; the tensile strength after curing for 24 hours after mixing is ≥0.4MPa; in the heating material, Al2O3 powder ≥38wt% and aluminum powder ≥20wt%.
5. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 4, characterized in that: Apply an alcohol-based coating with a thickness of ≥1mm to the surface of the heated core after molding.
6. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 4, characterized in that: The curing agent is any one or more of alkali-phenolic resin, Piper resin, and water glass.
7. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: Step S5: The heating core is fixed in the sand mold by pre-embedding or core placement.
8. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: In step S5, the drying temperature is 100-200℃ and the drying time is 8-20h.
9. The casting process for non-metallic fittings of large high-temperature alloy castings according to claim 1, characterized in that: Step S5, the casting temperature of the high-temperature alloy is 1450~1550℃.