A casting process for ductile iron wheel hubs

Abstract

This invention provides a casting process for ductile iron wheel hubs, relating to the field of wheel hub casting technology. The process includes steps such as mold material preparation, gating system design, melting and pouring, shrinkage stage, cooling, and demolding. During mold preparation, a specific release agent is evenly applied. The gating system is designed with 10 evenly distributed inlets. The dimensions, shapes, and layouts of the sprue, runner, and ingate are rationally designed. Temperature and composition are strictly controlled during melting. During the shrinkage stage, precise shrinkage compensation is performed in both liquid and solid states. Cooling speed is controlled. Demolding is achieved using a hydraulic ejector. The 10 inlets of the gating system ensure uniform wheel hub temperature for balanced solidification. Liquid shrinkage is compensated by the sprue, while solid shrinkage is self-compensated by graphitization expansion, resulting in a dense wheel hub without shrinkage porosity. This reduces defects caused by uneven temperature, significantly improves product quality and reliability, and has promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of wheel hub casting technology, and more specifically, relates to a casting process for ductile iron wheel hubs. Background Technology

[0002] Ductile iron is a high-strength cast iron material with comprehensive properties close to those of steel. Based on its excellent properties, it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness and wear resistance. Ductile iron has rapidly developed into a widely used cast iron material, second only to gray cast iron.

[0003] In the casting process of ductile iron wheel hubs, the previous gating system design was not reasonable enough, and the distribution of the inlet was uneven. This resulted in a large temperature difference between different parts of the wheel hub when the molten iron was poured into the mold, making it difficult to achieve uniform solidification. This uneven temperature situation is prone to casting defects, such as uneven structure, shrinkage cavities, and shrinkage porosity, which seriously affect the quality and performance of the wheel hub.

[0004] In the treatment of shrinkage during the casting of ductile iron wheel hubs, traditional processes have poor feeding effects in the sprue during the liquid solidification shrinkage stage, failing to fill the gaps generated by liquid shrinkage in a timely and effective manner, thus affecting the density of the wheel hub. In the solid shrinkage stage, due to insufficient utilization of the graphitization expansion caused by graphite precipitation, effective self-feeding cannot be achieved, leading to defects such as shrinkage porosity inside the wheel hub, reducing the mechanical properties and service life of the wheel hub.

[0005] Therefore, in view of this, we have studied and improved the existing structure and its shortcomings, and provided a casting process for ductile iron wheel hubs in order to achieve a more practical purpose. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a casting process for ductile iron wheel hubs. This process solves the problem that previous gating systems were poorly designed, with uneven inlet distribution, resulting in significant temperature differences between different parts of the wheel hub when molten iron is injected into the mold, making it difficult to achieve uniform solidification. This uneven temperature can easily lead to casting defects such as uneven microstructure, shrinkage cavities, and porosity, seriously affecting the quality and performance of the wheel hub.

[0007] A casting process for ductile iron wheel hubs includes the following steps:

[0008] S1: Mold material preparation: Prepare the corresponding mold, check the mold size, visually check the flatness and smoothness of the mold surface, and evenly apply high-quality mold release agent inside the mold. The mold release agent is graphite powder. Use an electronic platform scale to weigh and proportion the raw materials.

[0009] S2: Gating system design: Set 10 evenly distributed sprues on the mold, and rationally design the size, shape and layout of the sprue, runner and ingate;

[0010] S3: Smelting and casting: The raw materials prepared according to the proportion are put into the medium frequency induction melting furnace for smelting. Then, the molten iron is slowly and steadily poured into the mold at a speed of 0.5-1.0m / s through 10 pre-designed and evenly distributed water inlets.

[0011] S4: Shrinkage stage: In the initial shrinkage stage when molten iron changes from liquid to solid (about 5 to 10 minutes after pouring), the remaining molten iron in the sprue is used to feed the hub. When it enters the solid shrinkage stage (about 10 to 30 minutes after pouring), it relies on the graphitization expansion caused by the precipitation of graphite in the ductile iron to feed itself.

[0012] S5: Cooling and Demolding: Allow the wheel hub to cool in the mold. Once the wheel hub has cooled to room temperature (approximately 20-30°C), remove it from the mold using a demolding device.

[0013] Preferably, during the preparation of mold material in S1, the release agent is applied using a spray gun, with a thickness between 0.05 and 0.1 mm. After application, the release agent is allowed to stand in the mold for 0.5 hours.

[0014] Preferably, the graphite powder is composed of 15% to 30% graphite powder, 60% to 80% water, and 2% to 5% binder.

[0015] Preferably, during the S3 smelting process, a stirring device and a spectrometer are used to continuously stir and detect the composition, with the detection performed every 15 to 30 minutes to adjust the chemical composition of the molten iron.

[0016] Preferably, during the initial contraction phase of S4, multiple temperature measuring points are arranged at different parts of the wheel hub using thermocouples, and the temperature change is recorded every 1 to 2 minutes.

[0017] Preferably, the melting temperature in the melting furnace is between 1450-1550℃, the heating time is about 1-2 hours, and the holding time is about 0.5-1 hour.

[0018] Preferably, during the S5 cooling process, water is sprayed outside the mold to evaporate and absorb heat, thereby accelerating the cooling process.

[0019] Preferably, the cooling rate is controlled between 50-100°C / hour during the cooling process.

[0020] Preferably, the demolding process should use a hydraulic ejector with an ejection force of 10-50 tons and an ejection speed of 5-20 mm / s.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention uses a carefully designed gating system with 10 evenly distributed inlets to disperse the injection of molten iron, ensuring uniform temperature across all parts of the wheel hub and achieving balanced solidification. This design greatly reduces casting defects caused by uneven temperature, such as local shrinkage cavities and cracks. During the liquid solidification shrinkage stage of the wheel hub, effective feeding is achieved through the sprue. In the solid shrinkage stage, the graphitization expansion generated by graphite precipitation is fully utilized for self-feeding. This comprehensive and precise shrinkage control strategy results in a dense wheel hub without shrinkage porosity, significantly improving the quality and reliability of the product.

[0023] This invention successfully obtains a dense, shrinkage-free wheel hub casting, which significantly improves the mechanical properties of the wheel hub, enabling it to withstand greater loads and complex working conditions, and extending the service life of the wheel hub.

[0024] This invention optimizes process stability, reduces scrap rate caused by uneven shrinkage, improves the stability and repeatability of the production process, and reduces the risk of quality fluctuations.

[0025] This invention enables the production yield of ductile iron wheel hubs to reach 95%, significantly improving the utilization rate of raw materials and reducing material waste;

[0026] This invention reduces the use of riser materials and related processing and handling costs, while improving production efficiency and reducing the overall cost per unit product.

[0027] This invention reduces costs while ensuring product quality, making the produced ductile iron wheels more price-competitive in the market and helping to enhance the company's market competitiveness. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0029] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0030] like Figure 1As shown, this invention provides a high-performance ductile iron wheel hub casting process, effectively solving the problem that in the casting process of ductile iron wheel hubs, the previous gating system design was not reasonable enough, and the distribution of the inlet was uneven, resulting in large temperature differences in different parts of the wheel hub when molten iron was poured into the mold, making it difficult to achieve uniform solidification. This uneven temperature situation is prone to casting defects, such as uneven structure, shrinkage cavities, and porosity, which seriously affect the quality and performance of the wheel hub. The following will introduce the implementation process and effect of this process in detail through several specific embodiments, and compare and analyze them with data and tables.

[0031] Experimental materials and equipment:

[0032] Experimental materials:

[0033] High-quality ductile iron raw materials;

[0034] Graphite powder;

[0035] Experimental equipment:

[0036] Electronic platform scale:

[0037] spray gun:

[0038] Medium frequency induction melting furnace;

[0039] Casting molds;

[0040] Stirring device and spectrometer;

[0041] Thermocouple;

[0042] Hydraulic press ejector.

[0043] Example 1

[0044] Mold preparation: Select casting molds of specific specifications and structures, carefully check the integrity and dimensional accuracy of the molds, ensure that the mold surface is smooth and flawless, use an electronic scale to accurately weigh an appropriate amount of release agent, and use a spray gun to evenly coat the mold with a coating thickness of 0.05mm.

[0045] Melting: The ductile iron raw materials prepared according to the proportion are placed into a medium frequency induction melting furnace for melting. The melting temperature is 1500℃, the heating time is about 1.5 hours, and the holding time is about 0.8 hours. During the melting process, a stirring device is used to continuously stir the mixture at a stirring speed of 25 revolutions per minute.

[0046] Pouring: Through a carefully designed pouring system, the molten iron is poured steadily into the mold at a speed of 0.8 m / s until it is full.

[0047] Shrinkage control: In the initial shrinkage stage when molten iron changes from liquid to solid, the remaining molten iron in the sprue is used to compensate for the shrinkage of the hub; in the solid shrinkage stage, the graphitization expansion generated by the precipitation of graphite in ductile iron is used for self-compensation. During this process, multiple temperature measuring points are set up at different parts of the hub using thermocouples, and the temperature change is recorded every 1.5 minutes.

[0048] Cooling: Water is sprayed on the outside of the mold to evaporate and absorb heat, which accelerates the cooling rate and controls the cooling rate at 80℃ / hour.

[0049] Demolding: After the wheel hub cools to room temperature (about 25°C), use a hydraulic ejection device to demold. The ejection force is 30 tons and the ejection speed is 15 mm / s.

[0050] Example 2

[0051] Mold preparation: Select casting molds of specific specifications and structures, carefully check the integrity and dimensional accuracy of the molds, ensure that the mold surface is smooth and flawless, use an electronic scale to accurately weigh an appropriate amount of release agent, and use a spray gun to evenly coat the mold with a coating thickness of 0.08mm.

[0052] Melting: The ductile iron raw materials prepared according to the proportion are placed into a medium frequency induction melting furnace for melting. The melting temperature is 1550℃, the heating time is about 2 hours, and the holding time is about 1 hour. During the melting process, a stirring device is used to continuously stir at a stirring speed of 35 revolutions per minute.

[0053] Pouring: Through a carefully designed pouring system, the molten iron is poured steadily into the mold at a speed of 1.0 m / s until it is full.

[0054] Shrinkage control: In the initial shrinkage stage when molten iron changes from liquid to solid, the remaining molten iron in the sprue is used to compensate for the shrinkage of the hub; in the solid shrinkage stage, the graphitization expansion generated by the precipitation of graphite in ductile iron is used for self-compensation. During this process, multiple temperature measuring points are set up at different parts of the hub using thermocouples, and the temperature change is recorded every 2 minutes.

[0055] Cooling: Water is sprayed on the outside of the mold to evaporate and absorb heat, which accelerates the cooling rate and controls the cooling rate at 90℃ / hour.

[0056] Demolding: After the wheel hub cools to room temperature (about 25°C), use a hydraulic ejection device to demold. The ejection force is 40 tons and the ejection speed is 18 mm / s.

[0057] Example 3

[0058] Mold preparation: Select casting molds of specific specifications and structures, carefully check the integrity and dimensional accuracy of the molds, ensure that the mold surface is smooth and flawless, use an electronic scale to accurately weigh an appropriate amount of release agent, and use a spray gun to evenly coat the mold with a coating thickness of 0.1mm.

[0059] Melting: The ductile iron raw materials prepared according to the proportion are placed into a medium frequency induction melting furnace for melting. The melting temperature is 1450℃, the heating time is about 1 hour, and the holding time is about 0.6 hours. During the melting process, a stirring device is used to continuously stir the mixture at a stirring speed of 40 revolutions per minute.

[0060] Pouring: Through a carefully designed pouring system, the molten iron is poured steadily into the mold at a speed of 0.05 m / s until it is full.

[0061] Shrinkage control: In the initial shrinkage stage when molten iron changes from liquid to solid, the remaining molten iron in the sprue is used to compensate for the shrinkage of the hub; in the solid shrinkage stage, the graphitization expansion generated by the precipitation of graphite in ductile iron is used for self-compensation. During this process, multiple temperature measuring points are set up at different parts of the hub using thermocouples, and the temperature change is recorded once every 1 minute.

[0062] Cooling: Water is sprayed on the outside of the mold to evaporate and absorb heat, which accelerates the cooling rate and controls the cooling rate at 100℃ / hour.

[0063] Demolding: After the wheel hub cools to room temperature (about 25°C), use a hydraulic ejection device to demold it. The ejection force is 50 tons and the ejection speed is 20 mm / s.

[0064]

[0065] Analysis of the performance data of ductile iron wheel hubs in the above three embodiments leads to the following conclusions:

[0066] In terms of tensile strength, Example 2 performed best, reaching 700 MPa. This is likely due to its higher melting temperature (1550°C), longer heating time (2 hours), and longer holding time (1 hour), which resulted in a more uniform composition and denser microstructure of the molten iron, thereby improving the tensile strength of the material.

[0067] In terms of density, Example 2 also leads with 98.5%. The longer melting and holding times help to remove gases and impurities, while the more complete graphitization process also improves the density of the material.

[0068] In terms of dimensional accuracy, Example 2 also performs well, with ±0.15mm. This may be due to its optimized process parameters, such as pouring speed, cooling speed and demolding parameters, which allow for better control of shrinkage and deformation of the wheel hub during the molding process.

[0069] In summary, the process parameter combination of Example 2 achieved good results in terms of tensile strength, density, and dimensional accuracy. However, different application scenarios may have different requirements for these properties. For example, for some applications with high requirements for tensile strength, the process of Example 2 may be more suitable; while for situations where cost is more sensitive or dimensional accuracy requirements are not particularly strict, the processes of Example 1 or 3 may be more advantageous.

[0070] In actual production, the process parameters can be further optimized and adjusted according to specific product requirements and production conditions to achieve the best balance between performance and cost. At the same time, the process can be further studied and improved to enhance the overall quality and performance of ductile iron wheels and meet the ever-evolving market demands.

[0071] The proposed ductile iron wheel hub casting process is based on in-depth research and practical experience in the casting field. Through specific operations and data presentation of multiple embodiments, the significant effect of this process in improving the quality of ductile iron wheel hubs is clearly demonstrated.

[0072] In the mold preparation stage, we carefully select suitable casting molds and meticulously check their integrity and dimensional accuracy to ensure that the mold surface is smooth and flawless, which provides a good foundation for the subsequent casting process. In the process of applying the release agent, we strictly control the coating thickness to ensure smooth demolding and reduce the impact on the surface quality of the wheel hub.

[0073] The temperature control, heating time, and holding time settings during the smelting process directly affect the quality and compositional uniformity of the molten iron. The continuous operation of the stirring device further promotes the uniform mixing of the molten iron, ensuring the production of high-quality castings.

[0074] Precise control of the pouring speed ensures that the molten iron can fill the mold smoothly and evenly, reducing the generation of defects such as porosity and slag inclusions. The shrinkage compensation measures during the shrinkage stage effectively prevent problems such as shrinkage cavities and porosity, and improve the compactness of the wheel hub.

[0075] During the cooling process, the cooling rate is reasonably controlled to optimize the structure and performance of the wheel hub. During the demolding process, the precise operation of the hydraulic ejection device ensures that the wheel hub can be removed from the mold completely and smoothly without damage.

[0076] Data comparison and analysis of different embodiments show that although there are differences in the specific process parameter selection, they all achieve good casting results within the range set by this process. The changes in parameters such as melting temperature, holding time, pouring speed, and cooling speed reflect the characteristics and requirements of wheel hubs of different specifications and requirements in the casting process. However, no matter how the parameters are adjusted, the goal of improving the quality and performance of the wheel hub is ultimately achieved.

[0077] The evaluation of the casting effect was carried out from multiple aspects such as tensile strength, density and dimensional accuracy, taking into account the mechanical properties and manufacturing precision of the wheel hub. Through professional testing equipment and methods, the wheel hub in the embodiment showed excellent performance in all performance indicators, proving the reliability and effectiveness of this casting process.

[0078] The successful application of this process provides an efficient and reliable method for manufacturing ductile iron wheel hubs. In actual production, technicians can flexibly adjust the process parameters according to specific production needs and conditions to achieve the best casting effect. At the same time, this also provides a useful reference for the technological development and innovation in related fields.

[0079] In the future, with the continuous advancement of materials science and manufacturing technology, there is still room for further optimization and improvement in the casting process of ductile iron wheels. For example, developing new release agents and coatings to improve the service life of molds and the surface quality of castings; exploring more precise temperature control and monitoring technologies to optimize the melting and solidification process of molten iron; and combining numerical simulation and modeling technologies to predict and optimize casting process parameters in advance, thereby reducing the number of experiments and costs.

[0080] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A casting process for ductile iron wheel hubs, characterized in that: Includes the following steps: S1: Mold material preparation: Prepare the corresponding mold, check the mold size, visually check the flatness and smoothness of the mold surface, and evenly apply the release agent inside the mold. The release agent is graphite powder. Use an electronic platform scale to weigh and proportion the raw materials. S2: Gating system design: Set 10 evenly distributed sprues on the mold, and rationally design the size, shape and layout of the sprue, runner and ingate; S3: Smelting and casting: The raw materials prepared according to the proportion are put into the medium frequency induction melting furnace for smelting. Then, the molten iron is slowly and steadily poured into the mold at a speed of 0.5-1.0m / s through 10 pre-designed and evenly distributed water inlets. S4: Shrinkage stage: In the initial shrinkage stage when molten iron changes from liquid to solid, the remaining molten iron in the sprue is used to feed the hub. When it enters the solid shrinkage stage, it relies on the graphitization expansion generated by the precipitation of graphite in the ductile iron for self-feeding. S5: Cooling and Demolding: Allow the wheel hub to cool in the mold. Once the wheel hub has cooled to room temperature, use a demolding device to remove it from the mold. The melting temperature in the furnace is between 1450-1550℃, the heating time is 1-2 hours, and the holding time is 0.5-1 hour. The cooling rate is controlled between 50-100℃ / hour during the cooling process.

2. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: During the preparation of mold material for S1, the release agent is applied using a spray gun, with a thickness between 0.05 and 0.1 mm. After application, the release agent is allowed to stand in the mold for 0.5 hours.

3. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: The graphite powder is composed of 15%–30% graphite powder, 60%–80% water, and 2%–5% binder.

4. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: During the S3 smelting process, a stirring device and a spectrometer are used to continuously stir and detect the composition, with the detection performed every 15 to 30 minutes to adjust the chemical composition of the molten iron.

5. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: During the initial contraction phase of S4, multiple temperature measuring points were set up at different parts of the wheel hub using thermocouples, and the temperature change was recorded every 1 to 2 minutes.

6. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: During the S5 cooling process, water is sprayed outside the mold to evaporate heat and accelerate the cooling process.

7. The casting process for ductile iron wheel hubs as described in claim 1, characterized in that: The demolding process should use a hydraulic ejector with an ejection force of 10-50 tons and an ejection speed of 5-20 mm / s.

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