V-process and casting of large size thin shell castings

Abstract

The application belongs to the technical field of casting, and provides a V-process casting process for large-size thin-shell castings and the castings, which comprises the following steps: preparing a sand box mold; smelting molten iron and heating it to above 1500 DEG C, the component content of the molten iron including 3.5-3.8 wt% C, 2.2-2.6 wt% Si, 0.5-0.8 wt% Mn, <0.10 wt% S, 0.08-0.12 wt% P, 0.15-0.25 wt% RE, and the balance being Fe; controlling the pouring temperature to be 1390-1410 DEG C, pouring the molten iron into the sand box mold, and demolding after setting to obtain the large-size thin-shell castings. The V-process casting process for large-size thin-shell castings provided by the application can effectively overcome the defects such as cold shut, crack and lack of meat that are prone to occur in the castings, and through optimization of the process, the impact toughness of the castings can be further improved, and the brittle defects of the castings can be improved.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, and particularly relates to the V-process casting process and castings for large-sized thin-shell castings. Background Technology

[0002] V-process casting, also known as vacuum-sealed molding casting, is a sand casting process that uses vacuum negative pressure adsorption to form the mold. Its core principle is: a plastic film seals the sand box, and a vacuum pump extracts air from the sand box to create negative pressure, causing the dry sand to compact under this pressure. After pouring and cooling, the negative pressure is released, the molding sand disintegrates, and the casting can be removed. The plastic film is first heated and softened before being applied to the mold; this process is called coating. During coating, the mold is evacuated through a vacuum pipe, allowing the plastic film to adhere to the mold surface. In conventional coating processes, a vacuum pipe is typically installed on the outside of the mold to evacuate the inner cavity. When producing large, thin-shell castings, due to the presence of deep cavities in certain areas, the film's elongation and vacuum level limit prevent proper adhesion to the mold in some areas, affecting the product's shape. By improving the mold structure and installing dedicated vacuum pipes in the deep cavities of the mold according to the product structure, the film can be ensured to adhere well to the mold during coating.

[0003] Furthermore, in metal castings, thin-shell castings belong to the category of complex thin-walled shell castings. Especially when the size of the casting is too large, improper casting processes can severely restrict the performance of the casting. Large-sized thin-shell castings are characterized by overall dimensions reaching the meter level, but most of the structure is thin-shell, with the thinnest parts ranging from a few millimeters to tens of millimeters. For such large-sized thin-shell castings, increasing the smelting and casting temperatures, or increasing the number of gating systems, is insufficient to overcome defects such as cold shuts, cracks, and missing material after casting. Summary of the Invention

[0004] To address the aforementioned technical problems, this application proposes a V-process casting process and castings for large-sized thin-shell castings. The method described in this application is not limited to casting. Figure 1 The large-sized thin-shell castings shown can also be extended to castings with similar structural features. These castings are characterized by their large size, at least in the meter range, with the main body being a thin shell, and the thinnest part being a few millimeters to a dozen millimeters.

[0005] The specific technical solution is as follows:

[0006] The V-process casting process for large-sized thin-shell castings includes the following steps:

[0007] Prepare the sand box mold;

[0008] The molten iron is heated to above 1500℃, and the composition of the molten iron includes 3.5~3.8wt% C, 2.2~2.6wt% Si, 0.5~0.8wt% Mn, <0.10wt% S, 0.08~0.12wt% P, 0.15~0.25wt% RE, and the balance is Fe;

[0009] The casting temperature is controlled at 1390~1410 ℃. Molten iron is poured into a sand mold and demolded after shaping to obtain large-sized thin-shell castings.

[0010] Generally, ordinary gray cast iron does not contain refining agents (REs), and its basic components are usually carbon, silicon, manganese, phosphorus, sulfur, and iron. However, in some high-performance special gray cast irons, REs are added to refine the austenite dendrites and graphite structure to improve strength. In this application, the addition of REs also aims to mitigate the negative impact of increased phosphorus content.

[0011] As a preferred method, after the molten iron is heated to 1500 ℃, it is held at that temperature for more than 15 minutes before being transferred to the ladle.

[0012] As an alternative, before pouring molten iron into the sand mold, the sand mold is vibrated for more than 90 seconds after sand is added to improve the compactness of the sand mold; the vibration time is generally set to 100~120 seconds.

[0013] As a preferred option, the cavity of the sand mold is filled with gas at a temperature below 0°C before the molten iron is poured into the sand mold.

[0014] As a preferred option, the gas temperature is -5~0 ℃, and the filling time is not less than 10 min.

[0015] As a preferred option, the moisture content of the molding sand in the sand box is 0.5~0.8%.

[0016] In addition, this application also provides a type of thin-shell casting, which is manufactured using the V-process casting technology for large-size thin-shell castings.

[0017] The beneficial effects of this invention are as follows:

[0018] The V-process casting process for large-size thin-shell castings provided in this application can effectively overcome defects such as cold shuts, cracks, and missing material that are prone to occur in castings. Furthermore, by optimizing the process, it can further improve the impact toughness of castings and mitigate brittle defects. Attached Figure Description

[0019] Figures 1-3 This is a schematic diagram of the structure of a large-sized thin-shell casting produced by the method of the present invention. Detailed Implementation

[0020] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, those skilled in the art will understand that the invention can be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and appended claims, the word "comprising" should be interpreted in an open-ended, inclusive sense, i.e., as "including but not limited to".

[0021] In the following examples and comparative examples, the rare earth element is neodymium.

[0022] Example 1

[0023] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0024] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0025] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.5wt% C, 2.5wt% Si, 0.5wt% Mn, 0.03wt% S, 0.08wt% P, 0.2wt% RE, and the balance is Fe.

[0026] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0027] Example 2

[0028] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0029] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0030] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.4wt% Si, 0.7wt% Mn, 0.04wt% S, 0.09wt% P, 0.2wt% RE, and the balance is Fe.

[0031] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0032] Example 3

[0033] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0034] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0035] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.5wt% Si, 0.6wt% Mn, 0.04wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0036] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0037] Example 4

[0038] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0039] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0040] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.7wt% C, 2.3wt% Si, 0.5wt% Mn, 0.03wt% S, 0.11wt% P, 0.25wt% RE, and the balance is Fe.

[0041] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0042] Example 5

[0043] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0044] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0045] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.6wt% Si, 0.8wt% Mn, 0.05wt% S, 0.12wt% P, 0.25wt% RE, and the balance is Fe.

[0046] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0047] Comparative Example 1

[0048] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0049] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0050] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.5wt% Si, 0.7wt% Mn, 0.03wt% S, 0.07wt% P, 0.18wt% RE, and the balance is Fe.

[0051] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0052] Comparative Example 2

[0053] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0054] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0055] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.5wt% Si, 0.5wt% Mn, 0.04wt% S, 0.13wt% P, 0.25wt% RE, and the balance is Fe.

[0056] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0057] Comparative Example 3

[0058] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0059] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0060] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.7wt% C, 2.5wt% Si, 0.5wt% Mn, 0.04wt% S, 0.1wt% P, and the balance is Fe.

[0061] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0062] Comparative Example 4

[0063] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0064] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0065] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.4wt% Si, 0.6wt% Mn, 0.04wt% S, 0.1wt% P, 0.1wt% RE, and the balance is Fe.

[0066] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0067] Comparative Example 5

[0068] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0069] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0070] S2. Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.4wt% Si, 0.8wt% Mn, 0.06wt% S, 0.1wt% P, 0.15wt% RE, and the balance is Fe.

[0071] S3. Casting: Transfer the molten iron into a ladle and keep the temperature of the molten iron in the ladle at 1390~1410 ℃. Pour the molten iron into a sand mold. After shaping, demold to obtain a large-sized thin-shell casting.

[0072] It should be noted that in the above Examples 1-5 and Comparative Examples 1-5, the composition of the molten iron is 3.5-3.8 wt% C, 2.2-2.6 wt% Si, 0.5-0.8 wt% Mn, and <0.10 wt% S, which is a commonly used ratio setting in the art. In the specific examples or comparative examples, the content variation within the range has almost no effect on the quality of the casting.

[0073] Preparation Example 1

[0074] The casting processes of Examples 1-5 and Comparative Examples 1-5 were used to manufacture... Figure 1 The casting products shown are labeled as 1# to 5# for Examples 1 to 5, and 6# to 10# for Comparative Examples 1 to 5. The products are characterized by large size and thin shell. The dimensions of the castings are 1750×1550×450mm. The castings are thin shell castings with a minimum thickness of 10mm.

[0075] Quality defects of castings 1# to 10# were inspected separately. The quality defects included cold shuts, cracks, and missing parts. The impact toughness of the castings was tested using GB / T229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The results are shown in Table 1.

[0076] cold shut crack meat shortage Impact toughness / J 1# none none none 4.75 2# none none none 4.62 3# none none none 4.58 4# none none none 4.44 5# none none none 4.31 6# have have have 5.64 7# none none none 3.59 8# none none none 3.42 9# none none none 3.73 10# none none none 4.17

[0077] Table 1

[0078] Based on Table 1 and comparing castings #1 to #7, it was found that appropriately increasing the phosphorus (P) content in the molten iron, along with the addition of a certain amount of rare earth elements, can stably eliminate cold shuts, cracks, and incomplete filling defects in the thin-walled areas of the castings, and the P content should be controlled to be no less than 0.08%. However, if the P content in the molten iron exceeds 0.12%, the impact toughness will decrease significantly due to phosphorus eutectic, falling below 4J, thus increasing the brittleness of the castings. Therefore, the optimal P content in the molten iron should be set between 0.08% and 0.12%.

[0079] Comparing castings #8 to #10 with casting #3, when the P content in the molten iron is controlled within the preferred range, the content of rare earth elements will affect the performance of the castings. In particular, when the content of rare earth elements is less than 0.15%, the impact toughness of the castings will be less than 4J, which will increase the brittleness of the castings. Therefore, when the P content in the molten iron is preferably 0.08 to 0.12%, the content of rare earth elements is preferably above 0.15%.

[0080] Example 6

[0081] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0082] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0083] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.7wt% C, 2.5wt% Si, 0.7wt% Mn, 0.05wt% S, 0.1wt% P, 0.24wt% RE, and the balance is Fe.

[0084] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 5 minutes, then transferred to a ladle and the temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into a sand mold and demolded after shaping to obtain a large-sized thin-shell casting.

[0085] Example 7

[0086] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0087] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0088] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.5wt% C, 2.3wt% Si, 0.8wt% Mn, 0.04wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0089] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 10 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into a sand mold. After shaping, it is demolded to obtain a large-sized thin-shell casting.

[0090] Example 8

[0091] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0092] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0093] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.7wt% C, 2.5wt% Si, 0.6wt% Mn, 0.06wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0094] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into a sand mold. After shaping, it is demolded to obtain a large-sized thin-shell casting.

[0095] Example 9

[0096] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0097] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0098] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.4wt% Si, 0.8wt% Mn, 0.03wt% S, 0.1wt% P, 0.23wt% RE, and the balance is Fe.

[0099] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 20 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into a sand mold. After shaping, it is demolded to obtain a large-sized thin-shell casting.

[0100] Preparation Example 2

[0101] The casting processes described in Examples 6-9 were used to manufacture the products. Figure 1 The castings shown are labeled as 11# to 14#, and the quality defects of castings 11# to 14# are inspected. The quality defects include cold shuts, cracks, and missing parts. The impact toughness of the castings is tested using GB / T229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The results are shown in Table 2.

[0102] cold shut crack meat shortage Impact toughness / J 11# none none none 4.62 12# none none none 4.65 13# none none none 4.79 14# none none none 4.91

[0103] Table 2

[0104] Based on Table 2, comparing castings 11#~14# with casting 3#, it is found that melting the raw materials into molten iron and heating it, followed by heat treatment of the molten iron for a period of time, is more conducive to improving the impact toughness of the castings and reducing brittle defects in the castings. This effect is even more obvious when the heat treatment time exceeds 15 minutes.

[0105] Example 10

[0106] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0107] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0108] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.4wt% Si, 0.8wt% Mn, 0.04wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0109] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -1 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.5%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0110] Example 11

[0111] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0112] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0113] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.5wt% Si, 0.5wt% Mn, 0.03wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0114] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -2 ℃ and kept for 15 min. The moisture content of the molding sand in the sand mold is 0.6%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0115] Example 12

[0116] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0117] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0118] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.3wt% Si, 0.7wt% Mn, 0.05wt% S, 0.1wt% P, 0.24wt% RE, and the balance is Fe.

[0119] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -3 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.7%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0120] Example 13

[0121] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0122] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0123] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.7wt% C, 2.5wt% Si, 0.8wt% Mn, 0.06wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0124] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -3 ℃ and kept for 15 min. The moisture content of the molding sand in the sand mold is 0.8%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0125] Comparative Example 6

[0126] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0127] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0128] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.5wt% C, 2.5wt% Si, 0.7wt% Mn, 0.04wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0129] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -2 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.4%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0130] Comparative Example 7

[0131] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0132] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0133] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.4wt% Si, 0.6wt% Mn, 0.03wt% S, 0.1wt% P, 0.24wt% RE, and the balance is Fe.

[0134] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -2 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.9%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0135] Comparative Example 8

[0136] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0137] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0138] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.3wt% Si, 0.5wt% Mn, 0.05wt% S, 0.1wt% P, 0.23wt% RE, and the balance is Fe.

[0139] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -2 ℃ and kept for 5 min. The moisture content of the molding sand in the sand mold is 0.7%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0140] Comparative Example 9

[0141] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0142] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0143] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.5wt% C, 2.5wt% Si, 0.7wt% Mn, 0.04wt% S, 0.1wt% P, 0.25wt% RE, and the balance is Fe.

[0144] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas below 0 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.7%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0145] Comparative Example 10

[0146] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0147] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0148] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.6wt% C, 2.5wt% Si, 0.5wt% Mn, 0.04wt% S, 0.1wt% P, 0.24wt% RE, and the balance is Fe.

[0149] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -6 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.7%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0150] Comparative Example 11

[0151] This embodiment provides a V-process casting process for large-size thin-shell castings, which includes the following steps:

[0152] S1. Material preparation: Weigh various raw materials according to the proportions. The raw materials include scrap steel, recycled materials, ferrosulfide alloy, ferromanganese alloy, ferrochrome alloy and ferrosilicon alloy.

[0153] S2, Smelting: The raw materials prepared in S1 are placed into an induction furnace and heated to 1500 ℃, so that the raw materials in the induction furnace melt to form molten iron. The composition of the molten iron is 3.8wt% C, 2.3wt% Si, 0.7wt% Mn, 0.04wt% S, 0.03wt% P, 0.2wt% RE, and the balance is Fe.

[0154] S3. Casting: The molten iron in the induction furnace is kept at 1500 ℃ for 15 min and then transferred to a ladle. The temperature of the molten iron in the ladle is kept at 1390~1410 ℃. The molten iron is then poured into the sand mold. Before pouring the molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below -2 ℃ and kept for 10 min. The moisture content of the molding sand in the sand mold is 0.7%. After shaping, the large-sized thin-shell casting is obtained by demolding.

[0155] Preparation Example 3

[0156] The casting processes of Examples 10-13 and Comparative Examples 6-11 were used to manufacture... Figure 1 The casting products shown are labeled as 15#~18# for Examples 10~13 and 19#~24# for Comparative Examples 6~11. The quality defects of castings 15#~24# were inspected. The quality defects included cold shuts, cracks, and missing parts. The impact toughness of the castings was tested using GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The results are shown in Table 3.

[0157] cold shut crack meat shortage Impact toughness / J 15# none none none 5.11 16# none none none 5.15 17# none none none 5.24 18# none none none 5.21 19# none none none 5.09 20# none none none 5.17 21# none none none 4.88 22# none none none 4.96 23# have have none 5.05 24# have have have 6.13

[0158] Table 3

[0159] Referring to Table 3, comparing castings 15#~18# with castings 11#~14#, maintaining the moisture content of the molding sand in the sand mold within a certain range and filling the mold cavity with gas below 0℃ for a period of time further improves the impact toughness of the castings, with all exceeding 5J. However, for castings 19# and 20#, because the moisture content of the molding sand in the sand mold exceeded the range of 0.5~0.8%, although no defects such as cold shuts, cracks, or missing parts appeared, and the impact toughness was improved, defects exceeding the threshold appeared at the thin-walled sections of the castings. Deformation occurred; however, the short gas filling time in the sand mold cavity for casting #21 resulted in the impact toughness not reaching the ideal 5J; the excessively high gas temperature used in casting #21 also contributed to the impact toughness not reaching the ideal 5J; the excessively low gas temperature used in casting #23 led to the recurrence of cold shuts, cracks, and incomplete filling defects; and while the P content in the molten iron of casting #24 was significantly lower than the preferred range, and the impact toughness was significantly higher than other embodiments and comparative examples, the defects of cold shuts, cracks, and incomplete filling were not eliminated. Therefore, the preferred process conditions of this application are: while maintaining the P content in the molten iron within the preferred range, using gas at -5~0 ℃ to fill the sand mold cavity for a filling time of not less than 10 min, and maintaining the moisture content of the molding sand in the sand box at 0.5~0.8%, which can further improve the impact toughness of the casting and help reduce brittle defects in the casting.

[0160] The V-process casting technology for large-size thin-shell castings of the present invention can also be used for casting... Figure 2 and Figure 3 The thin-shell type casting product shown.

[0161] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A V-process casting technology for large-size thin-shell castings, characterized in that, Includes the following steps: Prepare the sand box mold; The molten iron is heated to above 1500℃, and the composition of the molten iron includes 3.5~3.8wt% C, 2.2~2.6wt% Si, 0.5~0.8wt% Mn, <0.10wt% S, 0.08~0.12wt% P, 0.15~0.25wt% RE, and the balance is Fe; The casting temperature is controlled at 1390~1410 ℃. Molten iron is poured into a sand mold and demolded after shaping to obtain large-sized thin-shell castings.

2. The V-process casting process for large-size thin-shell castings according to claim 1, characterized in that, After the molten iron is heated to 1500 ℃, it is kept at that temperature for more than 15 minutes before being transferred to the ladle.

3. The V-process casting process for large-size thin-shell castings according to claim 1, characterized in that, Before pouring molten iron into the sand mold, the cavity of the sand mold is filled with gas at a temperature below 0°C.

4. The V-process casting process for large-size thin-shell castings according to claim 3, characterized in that, The gas temperature is -5~0 ℃, and the filling time is not less than 10 min.

5. The V-process casting process for large-size thin-shell castings according to claim 4, characterized in that, The moisture content of the molding sand in the sand box is 0.5~0.8%.

6. Thin-shell castings, characterized in that, It is produced using the V-process casting technology for large-size thin-shell castings according to any one of claims 1 to 5.

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