A casting method of a large-sized ductile iron movable mold plate

Abstract

The application introduces a casting method of large nodular cast iron movable mold plate. The application adopts segmented lost foam combination method to produce large nodular cast iron movable mold plate, greatly reduces the number of outer mold and core box, avoids the adverse effects caused by the use of core support during core assembly, reduces the molding difficulty, and reduces the dimensional error formed by manual modeling; the side and bottom of the lost foam sample are provided with a reinforcing wooden mold, and a plurality of round steels are inserted into the lost foam sample, so as to increase the strength of the lost foam sample from two aspects, the method is reasonable in design, high in casting precision, and can overcome the defects of insufficient strength of the lost foam in traditional casting of large nodular cast iron and extrusion deformation; the base iron liquid of the casting is combined with spheroidization and multi-stage inoculation, the production process is reasonably arranged, the spheroidization inoculation time is shortened, and the labor intensity is reduced; in cooperation with the alloy component adjustment of the spheroidization line, the long-acting and high-efficiency inoculation effect is achieved, and the performance and internal quality requirements of the casting are ensured.

Description

Technical Field

[0001] This invention relates to the field of casting technology, and in particular to a casting method for a large ductile iron moving mold. Background Technology

[0002] As a major component of the die-casting machine's mold-closing mechanism, the moving mold plate is a key part that ensures the reliable opening and closing of the mold and affects the precision of plastic products. It plays an extremely important role in whether production can proceed smoothly and the quality of the castings. The moving mold plate weighs more than 100 tons, and many areas require ultrasonic and magnetic particle testing. Its internal quality and dimensional requirements are strict.

[0003] Traditional casting methods for large ductile iron mainly involve core assembly and model making, resulting in numerous production steps. Coupled with the complex structure of the castings, manufacturing costs are extremely high. Traditional methods also make it difficult to guarantee casting quality and are labor-intensive. Welding repairs are generally not permitted for large ductile iron castings, and localized quality problems can lead to the final scrapping of the casting. Lost foam casting, due to its low strength, is easily deformed under heavy pressure. In traditional sand casting, lost foam casting is mostly used for small and medium-sized cast iron parts. In the manufacturing of large cast iron parts, due to the larger dimensions, thicker walls, and more complex structures, the lost foam is more prone to deformation under pressure, leading to dimensional problems. Furthermore, box collapse and sand falling can cause internal quality issues. Therefore, lost foam casting is generally not used in the production of large cast iron parts. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a casting method for large ductile iron moving molds, which overcomes the disadvantage of extrusion deformation in the traditional casting of large ductile iron and ensures the quality of castings.

[0005] The technical solution adopted in this invention is: A casting method for a large ductile iron moving mold, the specific steps of which are as follows: S1: Lost foam model making: Based on the outline dimensions of the moving template, the position of the gating system, and the direction of demolding, the model is segmented and designed. Lost foam samples are made according to the segments. Reinforcing wooden molds are made for the bottom and side pressure points of the lost foam samples. Several round steel bars are inserted into the interior of each sample to increase the strength of the lost foam samples. The sand mold is divided into boxes according to the segments of the lost foam. S2: Molding: A single integral iron platform is set at the bottom of the pit as the base box, and the reference surface of the base box is calibrated by a level. The lost foam model is placed on it, and the outline dimensions of the moving template casting are drawn on the platform along the outer contour. The lost foam is lifted and placed into the sand box. Chills and guide core heads are set according to process requirements. After sand flow, the box is turned over to become the lower box. The lost foam is assembled and shaped according to the sections of the moving template. During the molding process, chills, cores and gating systems are placed in the corresponding positions according to process requirements. The plane of the lower box is the reference surface for the assembly of the lost foam sections and the formation of each main part of the casting. Finally, the movable blocks, gating system and risers are placed in the corresponding positions in the upper box. S3: Core setting and mold assembly: After the molding sand has cured, remove the lost foam sample model, clean the debris in the cavity and check the cavity, set the core and assemble the mold; after assembling the mold, fully bake the cavity and use tools to check the cavity again to ensure that there is no debris in the cavity; S4: Spheroidizing Treatment: The molten iron of the moving mold casting is melted in a medium-frequency induction furnace and adjusted to the required chemical composition. In-flow inoculation is then performed. The molten iron is poured into a preheated ladle, slag is removed, and the temperature is lowered to 1350–1400℃ before being transported to the spheroidizing station for wire feeding spheroidizing and inoculation. The spheroidizing and inoculation lines are fed in through the top of the spheroidizing station. The alloy powder composition and weight percentage of the spheroidizing line are as follows: Rare Earth Elements (RE): 1.5-2.3%, Mg: 22-24%, Si: 40-46%, Ca: 2.0-3.0%, Ba: 2.0-4.0%, MgO≤2.0%, Sb: 0.9-1.5%, with the balance being Fe. The alloy powder is packaged in steel pipes with a wall thickness <0.32mm. The wire feeding ratio of the spheroidizing and inoculation lines is 1:(0.6-1.1). S5: Casting: After spheroidization is completed, slag is quickly removed and temperature is measured. After the molten iron is inoculated in the pouring box, it is poured into the mold cavity. The time from the end of spheroidization to the end of casting should not exceed 30 minutes. After casting, riser covering agent is added to the riser. S6: Heat preservation: The casting is kept in the sand mold at a temperature below 150℃, then the sand is removed and the casting is cleaned.

[0006] Specifically, the rare earth element RE in S4 includes 60% by weight of light rare earth and 40% by weight of yttrium-based heavy rare earth.

[0007] Due to the adoption of the technical solution described above, the present invention has the following advantages: This invention employs a segmented lost foam casting method to produce large ductile iron moving molds, significantly reducing the number of outer molds and core boxes. This avoids the adverse effects of using core supports during core assembly on the casting, reduces molding difficulty, and minimizes dimensional errors caused by manual molding. Reinforcing wooden molds are installed on the compressed sides and bottom of the lost foam sample, and several round steel bars are inserted inside the lost foam sample, increasing its strength from two aspects. The method is rationally designed and has high casting precision, overcoming the shortcomings of insufficient strength and deformation under pressure in traditional casting of large ductile iron. The molten iron matrix of the casting undergoes a combination of spheroidizing inoculation and multi-stage inoculation, with a rationally arranged production process, shortening the spheroidizing inoculation time and reducing labor intensity. Combined with the alloy composition adjustment of the spheroidizing line, a long-term and efficient inoculation effect is achieved, ensuring the performance and internal quality requirements of the casting. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the segmented dynamic template sample of the present invention. Detailed Implementation

[0009] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments. However, this should not be construed as limiting the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0010] Combined with appendix Figure 1 The casting method for a large ductile iron moving mold shown herein includes the following specific steps: S1: Lost foam model making: The lost foam is segmented according to the outline dimensions of the moving template, the position of the gating system and the direction of demolding. Lost foam samples are made according to the segments. Reinforcing wooden molds are made at the bottom and side pressure positions of the lost foam samples. Several round steel bars are inserted into the interior of each sample to increase the strength of the lost foam sample. The sand mold is divided into upper box, middle box 1, middle box 2 and lower box according to the lost foam segmentation. The main body of the lost foam sample is located in middle box 1 and middle box 2.

[0011] S2: Molding: A single integral iron platform is set at the bottom of the pit as the bottom box, and the reference surface of the bottom box is calibrated by a level. The lost foam model is placed on it, and the outline dimensions of the moving template casting are drawn on the platform along the outer contour. The lost foam is lifted and placed into the sand box. Chills and guide core heads are set according to process requirements. After sand pouring, the box is turned over to become the lower box. The lost foam segment models corresponding to the middle 2 boxes are placed on the lower box. Chills, cores and gating system are placed according to process requirements, and sand pouring is performed. After the sand mold is solidified, the middle 1 box is shaped in the same way as above. The plane of the lower box is the reference surface for the assembly of the lost foam segments and the formation of each main part of the casting. Finally, the movable blocks, gating system and risers are placed in the corresponding positions in the upper box.

[0012] S3: Core setting and mold assembly: After all the molding sand has cured, remove the lost foam sample model, clean the debris in the cavity, check the cavity, set the core, and assemble the mold. After assembling the mold, fully bake the cavity and use tools to check the cavity again to ensure that there is no debris in the cavity.

[0013] S4: Spheroidizing treatment: The molten iron of the moving mold casting is melted in a medium-frequency induction furnace and adjusted to the required chemical composition. In-flow inoculation is then carried out. The molten iron is poured into a preheated ladle, slag is removed, and the temperature is lowered to 1350-1400℃. It is then transported to the spheroidizing station for wire feeding spheroidizing and wire feeding inoculation. The spheroidizing line and the inoculation line are fed in through the top of the spheroidizing station. The alloy powder composition and weight percentage of the spheroidizing line are as follows: rare earth elements RE: 1.5-2.3%, Mg: 22-24%, Si: 40-46%, Ca: 2.0-3.0%, Ba: 2.0-4.0%, MgO≤2.0%, Sb: 0.9-1.5%, with the balance being Fe. RE includes 60% light rare earth and 40% yttrium-based heavy rare earth. The alloy powder is packaged in steel pipes with a wall thickness of <0.32mm. The wire feeding ratio of the spheroidizing line and the inoculation line is 1:(0.6-1.1).

[0014] S5: Casting: After spheroidization is completed, slag is quickly removed and temperature is measured. After the molten iron is inoculated in the gating box, it is poured into the mold cavity. The time from the end of spheroidization to the end of casting should not exceed 30 minutes. After casting, riser covering agent is added to the riser.

[0015] S6: The casting is kept in the sand mold at a temperature below 150℃, then the sand is removed and the casting is cleaned.

[0016] Preferably, the rare earth element RE in S4 comprises 60% by weight of light rare earth and 40% by weight of yttrium-based heavy rare earth.

[0017] The parts of this invention not described in detail are prior art.

[0018] The embodiments selected herein for the purpose of disclosing the inventive objectives are currently considered suitable; however, it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of this concept and invention.

Claims

1. A casting method for a large ductile iron moving mold, characterized in that, The specific steps are as follows: S1: Lost foam model making: Based on the outline dimensions of the moving template, the position of the gating system, and the direction of demolding, the lost foam is segmented and designed. Lost foam samples are made according to the segments. Reinforcing wooden molds are made for the bottom and side pressure points of the lost foam samples. Several round steel bars are inserted into the interior of each sample to increase the strength of the lost foam samples. The sand mold is divided into upper box, middle box 1, middle box 2, and lower box according to the lost foam segments. The main body of the lost foam sample is located in middle box 1 and middle box 2. S2: Molding: A single integral iron platform is set at the bottom of the pit as the bottom box, and the reference surface of the bottom box is calibrated by a level. The lost foam model is placed on it, and the outline dimensions of the moving template casting are drawn on the platform along the outer contour. The lost foam is lifted and placed into the sand box. Chills and guide pillar cores are set according to process requirements. After sand pouring, the box is turned over to become the lower box. The lost foam segment models corresponding to the middle 2 boxes are placed on the lower box. Chills, cores and gating system are placed according to process requirements, and sand pouring is performed. After the sand mold solidifies, the middle 1 box is shaped in the same way as above. The plane of the lower box is the reference surface for the assembly of the lost foam segments and the formation of each main part of the casting. Finally, the movable blocks, gating system and risers are placed in the corresponding positions in the upper box. S3: Core setting and mold assembly: After the molding sand has cured, remove the lost foam sample model, clean the debris in the cavity and check the cavity, set the core and assemble the mold; after assembling the mold, fully bake the cavity and use tools to check the cavity again to ensure that there is no debris in the cavity; S4: Spheroidizing Treatment: The molten iron base of the moving mold casting is melted in a medium-frequency induction furnace and adjusted to the required chemical composition. In-flow inoculation is then performed. The molten iron is poured into a preheated ladle, slag is removed, and the temperature is lowered to 1350–1400℃ before being transported to the spheroidizing station for wire feeding spheroidizing and inoculation. The spheroidizing and inoculation lines are fed in through the top of the spheroidizing station. The alloy powder composition and weight percentage of the spheroidizing lines are: Rare Earth Elements (RE): 1.5-2.3%, Mg: 22-24%, Si: 40-46%, Ca: 2.0-3.0%, Ba: 2.0-4.0%, MgO≤2.0%, Sb: 0.9-1.5%, balance Fe; rare earth elements RE include 60% light rare earth and 40% yttrium-based heavy rare earth by weight; alloy powder is packaged in steel conduits with a wall thickness <0.32mm; the feeding ratio of spheroidizing wire and inoculating wire is 1:(0.6-1.1); S5: Casting: After spheroidization is completed, slag is quickly removed and temperature is measured. After the molten iron is inoculated in the pouring box, it is poured into the mold cavity. The time from the end of spheroidization to the end of casting should not exceed 30 minutes. After casting, riser covering agent is added to the riser. S6: Heat preservation: The casting is kept in the sand mold at a temperature below 150℃, then the sand is removed and the casting is cleaned.

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