A production method for improving the yield of small, thin-walled hydraulic castings

Abstract

This invention relates to a production method for improving the yield of small, thin-walled hydraulic castings. It primarily addresses the technical problems of existing methods for producing small, thin-walled hydraulic castings, such as the inability to eliminate cold shut defects and high scrap rates. The technical solution of this invention includes the following steps: S1, core making: A sand core is prepared using coated sand according to the shape of the inner cavity of the thin-walled hydraulic casting, and a coating is applied to the surface of the sand core; S2, molding: Molding sand is selected to prepare the required cavity according to the shape of the thin-walled hydraulic casting; the molding sand is pre-mixed clay wet molding sand, and the permeability of the molding sand is controlled to be >130; S3, melting: According to the mechanical performance requirements of the thin-walled hydraulic casting, the molten iron is melted into molten iron with the required chemical composition; S4, pouring: The molten iron is poured into the prepared cavity through the ingate of the mold, and a secondary inoculant is added during the pouring process to control the pouring temperature and speed of the final casting box; S5, sand removal: The mold after pouring is subjected to sand removal treatment, the casting is removed, the ingate is removed, and finally, sandblasting is performed.

Description

Technical Field

[0001] This invention belongs to the technical field of thin-walled casting production methods, specifically relating to a production method for improving the yield of small thin-walled hydraulic castings. Background Technology

[0002] The key indicator for controlling production costs in foundry enterprises is the casting yield rate, which is also the most important indicator for foundry enterprises. A high yield rate is of great significance to the enterprise's profits.

[0003] Small, thin-walled hydraulic castings refer to hydraulic castings weighing around 1 kg with local wall thicknesses less than 4 mm. These castings are characterized by their small weight, thin nozzle walls, and poor castability; they are highly susceptible to cold shut defects. In many cases, this defect accounts for the largest proportion of completely scrapped castings, resulting in a persistently high scrap rate. Most companies, in an attempt to prevent cold shut defects in these castings, simply increase the pouring temperature of the molten iron without a systematic production process approach, thus failing to solve this technical problem. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of existing small thin-walled hydraulic casting production methods, such as the inability to eliminate cold shut defects and high scrap rates, and to provide a production method that improves the yield of small thin-walled hydraulic castings.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A production method for improving the yield of small, thin-walled hydraulic castings includes the following steps:

[0007] S1. Core making: The required sand core is prepared by using coated sand according to the shape of the inner cavity of the thin-walled hydraulic casting, and the sand core surface is coated with paint.

[0008] S2. Molding: Select molding sand to prepare the mold with the required cavity according to the shape of the thin-walled hydraulic casting; the molding sand is clay wet molding sand mixed before molding, and the air permeability of the molding sand is controlled to be >130.

[0009] S3. Melting: Based on the mechanical property requirements of thin-walled hydraulic castings, select pig iron, scrap steel, recycled materials and alloys, and melt them into molten iron with the required chemical composition.

[0010] S4. Pouring: Molten iron is poured into the prepared cavity through the inner gate of the mold. Secondary inoculant is added during the pouring process to control the pouring temperature and pouring speed of the final box.

[0011] S5. Sand removal: After pouring, the mold is subjected to sand removal treatment, the casting is removed, the inner gate is removed, and finally sandblasting is performed.

[0012] Furthermore, the coating on the sand core brush must be used within 24 hours after drying.

[0013] Furthermore, the mold is provided with visible vent holes and concealed vent holes. The visible vent holes are directly connected to the mold cavity, while the concealed vent holes are vent holes that are not connected to the mold cavity. The minimum cross-sectional area of ​​the visible vent holes is equal to the wall thickness of the casting.

[0014] Further, the chemical composition of the molten iron by weight percentage is as follows: C: 3.6-3.7%, Si: 2.1-2.3%, Mn: 0.4-0.5%, P < 0.05%, S: 0.02%, Cu: 0.5-0.6%, Cr: 0.05%, Mo: 0.15%, V: 0.05%, Ti: 0.025%, Al: 0.03%, Sn: 0.05%, Mg: 0.035-0.055%, with the remainder being Fe.

[0015] Furthermore, the thickness of the ingate is greater than 2 / 3 of the casting wall thickness.

[0016] Furthermore, when the molten iron is poured from the induction furnace into the ladle, 75% ferrosilicon with a size of 30-40mm is added; then wire feeding and spheroidization treatment is performed, and an inoculant is added after the spheroidization treatment; the carbon content of the molten iron is controlled so that the eutectic degree of the treated molten iron is close to 1.

[0017] Furthermore, the amount of 75% ferrosilicon added is 0.4%; the primary inoculant is barium silicon inoculant, and the amount added is 0.4%.

[0018] Furthermore, the secondary inoculant is a sulfur-oxygen inoculant, and the amount added is 0.1-0.13%.

[0019] Furthermore, the final casting temperature is the temperature of the last batch of molten iron after casting is completed, and the temperature of the last batch of molten iron is >1400℃; the casting speed is 5-6 kg / s, which is controlled by the casting system.

[0020] The beneficial effects of this invention are:

[0021] This invention can completely solve and prevent cold shut defects, increasing the yield of small thin-walled hydraulic castings from 70% to 98%. Therefore, compared with the prior art, this invention has the advantages of high yield, wide application range and applicability to all hydraulic castings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the thickness of the inner gate of the present invention;

[0023] Figure 2 This is a schematic diagram of the exhaust system of the present invention;

[0024] In the diagram: 1-casting, 2-ingate, 3-visible vent, 4-concealed vent, 5-cavity. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 and Figure 2 As shown in this embodiment, a production method for improving the yield of small, thin-walled hydraulic castings includes the following steps:

[0027] S1. Core making: The required sand core is prepared by using coated sand according to the inner cavity shape of the thin-walled hydraulic casting 1, and a coating is applied to the surface of the sand core. The sand core must be used within 24 hours after the coating is dried.

[0028] S2. Molding: Select molding sand to prepare the mold for the required cavity 5 according to the shape of the thin-walled hydraulic casting 1; the molding sand is clay wet molding sand mixed before molding, and the air permeability of the molding sand is controlled to be >130; the mold is provided with open venting holes 3 and closed venting holes 4. The open venting holes 3 are directly connected to the cavity 5, and the closed venting holes 5 are venting holes that are not connected to the cavity 5. The minimum cross-sectional area of ​​the open venting holes 3 is equal to the wall thickness of the casting 1.

[0029] S3. Melting: Based on the mechanical property requirements of thin-walled hydraulic casting 1, select pig iron, scrap steel, recycled materials and alloys, and melt them into molten iron with the required chemical composition.

[0030] The chemical composition of the molten iron, by weight percentage, is as follows: C: 3.6-3.7%, Si: 2.1-2.3%, Mn: 0.4-0.5%, P < 0.05%, S: 0.02%, Cu: 0.5-0.6%, Cr: 0.05%, Mo: 0.15%, V: 0.05%, Ti: 0.025%, Al: 0.03%, Sn: 0.05%, Mg: 0.035-0.055%, with the remainder being Fe.

[0031] S4. Pouring: Molten iron is poured into the prepared cavity 5 through the inner gate 2 of the mold. Secondary inoculant is added during the pouring process to control the pouring temperature and pouring speed of the final box.

[0032] The thickness of the inner gate 2 is greater than 2 / 3 of the wall thickness of the casting 1;

[0033] When the molten iron is poured from the induction furnace into the ladle, 75% ferrosilicon with a size of 30-40mm is added; then wire feeding and spheroidizing treatment is performed, and an inoculant is added after the spheroidizing treatment; the carbon content of the molten iron is controlled so that the eutectic degree of the treated molten iron is close to 1;

[0034] The amount of 75% ferrosilicon added is 0.4%; the primary inoculant is barium silicon inoculant, and the amount added is 0.4%; the secondary in-flow inoculant is sulfur-oxygen inoculant, and the amount added is 0.1-0.13%; the amounts of the above-mentioned 75% ferrosilicon, primary inoculant and secondary in-flow inoculant are all weight percentages.

[0035] The final casting temperature is the temperature of the last batch of molten iron after casting is completed, and the temperature of the last batch of molten iron is >1400℃; the casting speed is 5-6 kg / s, which is controlled by the casting system.

[0036] S5. Sand removal: After pouring, the mold is subjected to sand removal treatment, the casting is removed, the inner gate is removed, and finally sandblasting is performed.

Claims

1. A production method for improving the yield of small, thin-walled hydraulic castings, characterized in that, Includes the following steps: S1. Core making: The required sand core is prepared by using coated sand according to the shape of the inner cavity of the thin-walled hydraulic casting, and the sand core surface is coated with paint. S2. Molding: Select molding sand to prepare the mold with the required cavity according to the shape of the thin-walled hydraulic casting; the molding sand is clay wet molding sand mixed before molding, and the air permeability of the molding sand is controlled to be >130. S3. Melting: Based on the mechanical property requirements of thin-walled hydraulic castings, select pig iron, scrap steel, recycled materials and alloys, and melt them into molten iron with the required chemical composition. S4. Pouring: Molten iron is poured into the prepared cavity through the inner gate of the mold. Secondary inoculant is added during the pouring process to control the pouring temperature and pouring speed of the final box. S5. Sand removal: After pouring, the mold is subjected to sand removal treatment, the casting is removed, the inner gate is removed, and finally sandblasting is performed. The mold is provided with visible vent holes and concealed vent holes. The visible vent holes are directly connected to the mold cavity, while the concealed vent holes are not connected to the mold cavity. The minimum cross-sectional area of ​​the visible vent holes is equal to the wall thickness of the casting. The chemical composition (by weight percentage) of the molten iron is as follows: C: 3.6-3.7%, Si: 2.1-2.3%, Mn: 0.4-0.5%, P < 0.05%, S: 0.02%, Cu: 0.5-0.6%, Cr: 0.05%, Mo: 0.15%, V: 0.05%, Ti: 0.025%, Al: 0.03%, Sn: 0.05%, Mg: 0.035-0.055%, the remainder being Fe; The final casting temperature is the temperature of the last batch of molten iron after casting is completed, and the temperature of the last batch of molten iron is >1400℃; the casting speed is 5-6 kg / s, which is controlled by the casting system.

2. The production method for improving the yield of small thin-walled hydraulic castings according to claim 1, characterized in that: The coating on the sand core brush must be used within 24 hours after it dries.

3. The production method for improving the yield of small thin-walled hydraulic castings according to claim 1, characterized in that: The thickness of the ingate is greater than 2 / 3 of the casting wall thickness.

4. A production method for improving the yield of small, thin-walled hydraulic castings according to claim 1, characterized in that: When the molten iron is poured from the induction furnace into the ladle, 75% ferrosilicon with a size of 30-40mm is added; then wire feeding and spheroidization treatment is performed, and an inoculant is added after the spheroidization treatment; the carbon content of the molten iron is controlled so that the eutectic degree of the treated molten iron is close to 1.

5. A production method for improving the yield of small, thin-walled hydraulic castings according to claim 4, characterized in that: The amount of 75% ferrosilicon added is 0.4%; the primary inoculant is barium silicon inoculant, and the amount added is 0.4%.

6. A production method for improving the yield of small, thin-walled hydraulic castings according to claim 1, characterized in that: The secondary inoculant is a sulfur-oxygen inoculant, and the amount added is 0.1-0.13%.

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