Resin sand casting surface anti-sulfur penetration coating and coating method

Abstract

The present invention discloses an anti-sulfur penetration coating for the surface of resin sand castings and a coating method, including coating A and coating B; the components of coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 17%, additive 1.01%, first nodulizer 2.5% - 3%, and the balance is ethanol; the first nodulizer is a 3-8 nodulizer; the components of coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 16%, additive 1.01%, second nodulizer 5%, and the balance is ethanol; the second nodulizer is a coated nodulizer, which is formed by immersing the first nodulizer in a molten salt bath, physically adsorbing on the surface of the first nodulizer, and cooling and solidifying to form a coating layer with a thickness of 10 - 50 μm. The present invention adopts a double-layer structure of coating A and coating B, which not only has high compressive strength, but also has good sulfur-containing gas neutralization effect and supplementary nodulizing effect, further reducing the defective rate of products.

Description

Technical Field

[0001] The present invention belongs to the technical field of foundry coatings, and particularly relates to an anti-sulfur penetration coating for the surface of resin sand castings and a coating method. Background Art

[0002] The technological principle of resin sand mold process is as follows: furan resin and curing agent are added to the molding sand and stirred evenly. The resin and the curing agent react to harden the sand mold to meet the strength requirements for pouring molten iron. The curing agent must be an acidic liquid. The most economical and useful curing agent is sulfonic acid curing agent, and sulfur is contained in sulfonic acid. After high-temperature molten iron is poured into the sand mold, under the action of high temperature, sulfur (sulfur brought in by the curing agent) in the molding sand forms SO2 and enters the molten iron in the surface layer of the cavity. SO2 reacts with magnesium (Mg) in the molten iron, and the reaction is Mg + SO2 = MgO + MgS. As a result of the reaction, the effective content of magnesium element in the molten iron of the casting surface layer is insufficient, which is not enough to spheroidize graphite, resulting in the formation of a flake graphite reaction layer on the surface of the nodular iron, causing nodularization decay on the surface layer of the casting, and even turning into gray cast iron, as shown in Figure 1 Attachments Figure 2 described.

[0003] Although the resin sand molding process is simple, convenient and has a low cost, it has defects of sulfur penetration or reaction layer that are difficult to overcome. Especially when using furan resin sand to produce nodular iron castings, sulfur penetration defects will occur on the lower surface of nodular iron castings with thick and large wall thickness or large hot spots, that is, sulfur in the sand mold diffuses into the surface layer of the casting, causing nodularization decay of 1-5 mm on the surface layer of the nodular iron casting, and even turning into flake graphite of gray cast iron, also known as the reaction layer or sulfur penetration defect. This structure will affect the performance of the casting. Under the action of fatigue load, the casting will fracture from the defective area, resulting in the failure of the casting.

[0004] The Chinese invention with the application number 202010990336.2 and the name of "a coating for completely eliminating the surface reaction layer defects of nodular iron castings" discloses a coating, which mainly adds a nodulizer on the basis of a conventional anti-sulfur penetration coating, so as to neutralize, absorb and shield sulfur elements and sulfur-containing gases diffused into the molten iron in the resin sand mold, and at the same time has good nodulizing effect on the molten iron, so as to eliminate the surface reaction layer defects of nodular iron castings produced by resin sand. Its principle mainly includes a sulfur element neutralization mechanism and a nodulizing element replenishment mechanism. Among them, the sulfur element neutralization mechanism is a chemical adsorption reaction. Active elements (Mg, rare earth) in the nodulizer react with sulfur-containing gases such as H2S and SO2 released by the decomposition of resin sand to form stable sulfides (such as MgS, Ce2S3), preventing sulfur from diffusing into the molten iron. The reaction formulas are Mg + H2S → MgS + H2↑; 2Ce + 3SO2 → Ce2S3 + 3O2; at the same time, the nodulizer forms a dense barrier in the coating to inhibit the migration of sulfur from the sand mold to the molten iron interface and reduce the interfacial sulfur concentration gradient; the nodulizing element replenishment mechanism is that Mg in the nodulizer is released at high temperature to replenish the residual Mg consumed by sulfur and restore the formation ability of nodulizing cores.

[0005] However, the amount of spheroidizing agent added to the conventional anti-sulfur coating is a difficult problem to balance. If the amount of spheroidizing agent added is small, the sulfur invading the molten iron cannot be fully neutralized, and the residual sulfur will still preferentially consume the magnesium element in the molten iron, resulting in insufficient spheroidizing elements (Mg) on the surface layer and forming a flake graphite layer; if the amount of spheroidizing agent added is large, the decomposition products of the resin in the conventional anti-sulfur coating at high temperature will react violently with the excessive Mg to generate excessive brittle compounds such as MgO, SiC or magnesium silicate (MgSiO3), thus affecting the structural strength of the coating. In summary, no matter how much spheroidizing agent is added to the conventional anti-sulfur coating, it will cause a certain defective rate of the cast iron products. How to reduce this defective rate is an urgent problem to be solved. Summary of the Invention

[0006] In view of the problems in the prior art, the present invention proposes the following technical solutions:

[0007] The anti-sulfur coating for the surface of resin sand castings includes coating A and coating B;

[0008] The components of coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 17%, auxiliary agent 1.01%, first spheroidizing agent 2.5% - 3%, and the rest is ethanol; the first spheroidizing agent is a 3 - 8 spheroidizing agent, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0009] The components of coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 16%, auxiliary agent 1.01%, second spheroidizing agent 5%, and the rest is ethanol; the second spheroidizing agent is a coated spheroidizing agent, which is formed by immersing the first spheroidizing agent in a molten salt bath and forming a 10 - 50 μm coating layer on the surface of the first spheroidizing agent through physical adsorption and then cooling and solidifying;

[0010] The components of the auxiliary agent and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0011] As a preference of the above technical solution, the molten salt bath uses a NaCl - KCl mixed salt, and the eutectic melting point temperature required for melting is 650 - 700 °C.

[0012] Preferably, after the first spheroidizing agent is immersed in the molten salt bath and cooled and solidified to form a coating layer with a thickness of 10 - 50 μm, the second spheroidizing agent particles and crushed salt slag are separated by mechanical crushing in combination with vibration screening.

[0013] Preferably, the particle size of the first spheroidizing agent is 235 mesh.

[0014] Preferably, after the coating A and the coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, such that the Baume degree of the coating A is 35 - 40 and the Baume degree of the coating B is 39 - 45.

[0015] Preferably, the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of the sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0016] A coating method, which is applied to the surface sulfur-proof coating of the resin sand casting described above, and the coating method includes the following steps:

[0017] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0018] S2. Coating of the coating B: Coat the coating B on the inner cavity surface of the sand mold, and ignite for drying;

[0019] S3. Coating of the coating A: On the basis of S2, further coat the coating A on the inner cavity surface of the sand mold, and ignite for drying; to form a double-layer structure of coating B + coating A.

[0020] Preferably, the coating thickness of the coating A is 0.2 - 0.4 mm, and the coating thickness of the coating B is 0.3 - 0.4 mm.

[0021] Preferably, the set drying temperature of the coating B and the coating A is 140 - 160 °C, and the set drying time is 25 - 35 minutes.

[0022] The beneficial effects of the present invention are:

[0023] The coating and coating method of the present invention adopt a double-layer structure, which includes coating A and coating B; Coating A is coated between coating B and the casting, and the molten iron first contacts coating A. Since the content of the spheroidizing agent in coating A is relatively low, the overall structural strength of the coating can be ensured. At the same time, Mg in the spheroidizing agent in coating A is released at high temperature to supplement the residual Mg consumed by sulfur on the surface of the molten iron and restore the ability to form spheroidizing cores; Coating B is coated between coating A and the sand mold. Coating A that the molten iron first contacts forms a dense barrier layer, and the spheroidizing agent in coating B is processed into a coated spheroidizing agent. The coating layer relatively blocks the spheroidizing agent from the coating binder. When pouring molten iron, it avoids the violent boiling reaction of the active element Mg in the spheroidizing agent to generate excessive brittle compounds, thus maintaining the compressive strength of the coating; The coating layer gradually melts during the pouring of molten iron and gradually releases the active elements in the spheroidizing agent. The active elements react with the sulfur-containing gas released by the decomposition of the resin sand to generate stable sulfides, preventing sulfur from diffusing into the molten iron. Therefore, the coating of the present invention not only has high compressive strength, but also has good sulfur-containing gas neutralization effect and spheroidizing supplement effect, further reducing the defective rate of products. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 、 Figure 2 FIG. shows the graph of spheroidization decay of the surface layer of resin sand castings. DETAILED DESCRIPTION OF THE INVENTION

[0025] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0026] The sulfur-proof coating on the surface of resin sand castings includes coating A and coating B;

[0027] The composition of coating A and the mass percentage of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, auxiliary agent 1.01%, first spheroidizing agent 2.5% - 3%, and the rest is ethanol; The first spheroidizing agent is a 3 - 8 spheroidizing agent, and its composition is: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0028] The components of Coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, additive 1.01%, second spheroidizing agent 5%, and the rest is ethanol; the second spheroidizing agent is a coated spheroidizing agent, which is formed by immersing the first spheroidizing agent in a molten salt bath, physically adsorbing on the surface of the first spheroidizing agent, and cooling and solidifying to form a coating layer with a thickness of 10 - 50 μm;

[0029] The components of the additive and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0030] In the present invention, zircon powder, as the main refractory filler, has good high-temperature resistance and sulfur-proof performance; the binder uses phenolic resin to provide the bonding strength of the coating, and at the same time improves the crack resistance and high-temperature stability of the coating; vegetable gum is used as an auxiliary binder to enhance the thixotropy and suspension of the coating; modified clay improves the suspension and thixotropy of the coating to prevent the precipitation of refractory fillers; the sulfur-proof agent is composed of a strong oxidant and a metal oxide, which are respectively used to form sintering elements, react with sulfur, and have both sintering and reaction functions, effectively preventing the penetration of sulfur; the dispersant is used to improve the dispersibility of the coating and prevent particle aggregation; the surfactant is used to enhance the wettability and permeability of the coating; the thickener is used to adjust the viscosity of the coating and improve the drapability; the defoamer is used to prevent the generation of bubbles during the stirring and use of the coating; the preservative is used to extend the service life of the coating and prevent deterioration. Example 1

[0031] This example provides a sulfur-proof coating for the surface of resin sand castings, including Coating A and Coating B;

[0032] The components of Coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, additive 1.01%, first spheroidizing agent 2.5%, and the rest is ethanol; the first spheroidizing agent is a 3 - 8 spheroidizing agent, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0033] The components of Coating B and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, additive 1.01%, second spheroidizing agent 5%, and the rest is ethanol; among them, the second spheroidizing agent is a coated spheroidizing agent, which is formed by immersing the first spheroidizing agent in a molten salt bath of NaCl-KCl mixed salt, physically adsorbing on the surface of the first spheroidizing agent, and cooling and solidifying to form a coating layer with a thickness of 10-50 μm.

[0034] The components of the additive and their mass percentages are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, and preservative 19.8%.

[0035] Among them, the particle size of the first spheroidizing agent is 235 mesh; after Coating A and Coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of Coating A is 38 and the Baume degree of Coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0036] A method for coating the surface of resin sand castings with a sulfur-proof coating includes the following steps:

[0037] S1. Preparation of the coating: Prepare the coating according to the components of the coating and their mass percentages and stir evenly.

[0038] S2. Coating of Coating B: Coat Coating B on the inner cavity surface of the sand mold and ignite for drying.

[0039] S3. Coating of Coating A: On the basis of S2, further coat Coating A on the inner cavity surface of the sand mold and ignite for drying; a double-layer structure of Coating B + Coating A is formed.

[0040] Among them, the coating thickness of Coating A is 0.3 mm, and the coating thickness of Coating B is 0.35 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example 2

[0041] This example provides a sulfur-proof coating for the surface of resin sand castings, including Coating A and Coating B;

[0042] The components of Coating A and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, additives 1.01%, first nodulizer 3%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0043] The components of Coating B and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, additives 1.01%, second nodulizer 5%, and the rest is ethanol; the second nodulizer is a coated nodulizer, which is formed by immersing the first nodulizer in a molten salt bath of a NaCl-KCl mixed salt, physically adsorbing on the surface of the first nodulizer, and cooling and solidifying to form a coating layer of 10-50 μm;

[0044] The components of the additives and their mass percentages are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0045] Among them, the particle size of the first nodulizer is 235 mesh; after Coating A and Coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of Coating A is 38 and the Baume degree of Coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0046] The coating method of the sulfur-proof coating on the surface of resin sand castings includes the following steps:

[0047] S1. Preparation of the coating: Prepare the coating according to the coating components and their mass percentages and stir evenly;

[0048] S2. Coating of Coating B: Coat Coating B on the inner cavity surface of the sand mold and ignite for drying;

[0049] S3. Coating of Coating A: On the basis of S2, further coat Coating A on the inner cavity surface of the sand mold and ignite for drying; to form a double-layer structure of Coating B + Coating A.

[0050] Among them, the coating thickness of Coating A is 0.3 mm, and the coating thickness of Coating B is 0.35 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example 3

[0051] This example provides an anti-sulfur leakage coating for the surface of resin sand castings, including Coating A and Coating B;

[0052] The components of Coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 17%, auxiliary agent 1.01%, first nodulizer 3.4%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0053] The components of Coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 16%, auxiliary agent 1.01%, second nodulizer 5%, and the rest is ethanol; among them, the second nodulizer is a coated nodulizer, which is formed by immersing the first nodulizer in a molten salt bath of NaCl-KCl mixed salt, and through physical adsorption on the surface of the first nodulizer, cooling and solidifying to form a coating layer of 10-50 μm;

[0054] The components of the auxiliary agent and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0055] Among them, the particle size of the first nodulizer is 235 mesh; after Coating A and Coating B are stirred evenly, the Baume density of the coating solution is measured with a Baume hydrometer, so that the Baume density of Coating A is 38 and the Baume density of Coating B is 40; the anti-sulfur agent includes anti-sulfur agent FS-1, anti-sulfur agent FS-2, and anti-sulfur agent FS-3, and the mass percentages of anti-sulfur agent FS-1, anti-sulfur agent FS-2, and anti-sulfur agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0056] The coating method of the anti-sulfur leakage coating for the surface of resin sand castings includes the following steps:

[0057] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0058] S2. Coating with Coating B: Coat Coating B on the inner cavity surface of the sand mold and ignite for drying.

[0059] S3. Coating with Coating A: On the basis of S2, further coat Coating A on the inner cavity surface of the sand mold and ignite for drying; a double-layer structure of Coating B + Coating A is formed.

[0060] Among them, the coating thickness of Coating A is 0.3 mm, and the coating thickness of Coating B is 0.35 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example 4

[0061] This example provides an anti-sulfur leakage coating for the surface of resin sand castings, including Coating A and Coating B;

[0062] The components of Coating A and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 17%, auxiliary agent 1.01%, first nodulizer 3%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0063] The components of Coating B and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 16%, auxiliary agent 1.01%, second nodulizer 4.5%, and the rest is ethanol; among them, the second nodulizer is an encapsulated nodulizer, which is formed by immersing the first nodulizer in a molten salt bath of NaCl-KCl mixed salt, physically adsorbing on the surface of the first nodulizer, and cooling and solidifying to form a coating layer of 10-50 μm;

[0064] The components of the auxiliary agent and their mass percentages are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0065] Among them, the particle size of the first nodulizer is 235 mesh; after Coating A and Coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of Coating A is 38 and the Baume degree of Coating B is 40; the anti-sulfur agent includes anti-sulfur agent FS-1, anti-sulfur agent FS-2, and anti-sulfur agent FS-3, and the mass percentages of anti-sulfur agent FS-1, anti-sulfur agent FS-2, and anti-sulfur agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0066] Coating method for anti-sulfur penetration on the surface of resin sand castings, comprising the following steps:

[0067] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0068] S2. Coating of coating B: Coat coating B on the inner cavity surface of the sand mold, and ignite for drying;

[0069] S3. Coating of coating A: On the basis of S2, further coat coating A on the inner cavity surface of the sand mold, and ignite for drying; to form a double-layer structure of coating B + coating A.

[0070] Among them, the coating thickness of coating A is 0.3 mm, and the coating thickness of coating B is 0.35 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example 5

[0071] This example provides an anti-sulfur penetration coating on the surface of resin sand castings, including coating A and coating B;

[0072] The components of coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 17%, auxiliary agent 1.01%, first nodulizer 3%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0073] The components of coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfur agent 16%, auxiliary agent 1.01%, second nodulizer 5.6%, and the rest is ethanol; among them, the second nodulizer is a wrapped nodulizer, which is obtained by immersing the first nodulizer in a molten salt bath of NaCl-KCl mixed salt, and through physical adsorption on the surface of the first nodulizer, cooling and solidifying to form a coating layer of 10-50 μm;

[0074] The components of the auxiliary agent and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0075] Among them, the particle size of the first nodulizer is 235 mesh; after coating A and coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of coating A is 38 and the Baume degree of coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2 and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0076] A method for coating a surface anti-sulfur coating on a resin sand casting, comprising the following steps:

[0077] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0078] S2. Coating of coating B: Coat coating B on the inner cavity surface of the sand mold and ignite for drying;

[0079] S3. Coating of coating A: On the basis of S2, further coat coating A on the inner cavity surface of the sand mold and ignite for drying; a double-layer structure of coating B + coating A is formed.

[0080] Among them, the coating thickness of coating A is 0.3 mm, and the coating thickness of coating B is 0.35 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example Six

[0081] This example provides a surface anti-sulfur coating for resin sand castings, including coating A and coating B;

[0082] The components of coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, auxiliary agent 1.01%, first nodulizer 3%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0083] The components of coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, auxiliary agent 1.01%, second nodulizer 5%, and the rest is ethanol; among them, the second nodulizer is a wrapped nodulizer, which is formed by immersing the first nodulizer in a molten salt bath of NaCl-KCl mixed salt, physically adsorbing on the surface of the first nodulizer, and cooling and solidifying to form a 10-50 μm coating layer;

[0084] The auxiliary components and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0085] Among them, the particle size of the first nodulizer is 235 mesh; after coating A and coating B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of coating A is 38 and the Baume degree of coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2 and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2 and sulfur-proof agent FS-3 are 29.4%, 58.8% and 11.8% respectively.

[0086] The coating method of the sulfur-proof coating on the surface of resin sand castings includes the following steps:

[0087] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0088] S2. Coating of coating B: Coat coating B on the inner cavity surface of the sand mold and ignite for drying;

[0089] S3. Coating of coating A: On the basis of S2, further coat coating A on the inner cavity surface of the sand mold and ignite for drying; a double-layer structure of coating B + coating A is formed.

[0090] Among them, the coating thickness of coating A is 0.28 mm, and the coating thickness of coating B is 0.38 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes. Example VII

[0091] This example provides a sulfur-proof coating on the surface of resin sand castings, including coating A and coating B;

[0092] The components of coating A and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, auxiliary agent 1.01%, first nodulizer 3%, and the rest is ethanol; the first nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0093] The components of Coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, additive 1.01%, second spheroidizing agent 5%, and the rest is ethanol; among them, the second spheroidizing agent is a coated spheroidizing agent, which is formed by immersing the first spheroidizing agent in a molten salt bath of a NaCl-KCl mixed salt, physically adsorbing on the surface of the first spheroidizing agent, and cooling and solidifying to form a coating layer with a thickness of 10-50 μm.

[0094] The components of the additive and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0095] Among them, the particle size of the first spheroidizing agent is 235 mesh; after Coatings A and B are stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of Coating A is 38 and the Baume degree of Coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0096] A method for coating the surface of a resin sand casting with a sulfur-proof coating includes the following steps:

[0097] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly.

[0098] S2. Coating of Coating B: Coat Coating B on the inner cavity surface of the sand mold, and ignite and dry it.

[0099] S3. Coating of Coating A: On the basis of S2, further coat Coating A on the inner cavity surface of the sand mold, and ignite and dry it; a double-layer structure of Coating B + Coating A is formed.

[0100] Among them, the coating thickness of Coating A is 0.33 mm, and the coating thickness of Coating B is 0.33 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes.

[0101] Comparative Example 1

[0102] This comparative example provides a sulfur-proof coating for the surface of a resin sand casting, including Coating A.

[0103] The components of Coating A and their mass percentages are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 17%, additives 1.01%, primary nodulizer 3%, and the rest is ethanol; the primary nodulizer is a 3-8 nodulizer, and its components are: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0104] The components of the additives and their mass percentages are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0105] Among them, the particle size of the primary nodulizer is 235 mesh; after Coating A is stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer, so that the Baume degree of Coating A is 38 and the Baume degree of Coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0106] The coating method of the sulfur-proof coating on the surface of resin sand castings includes the following steps:

[0107] S1. Preparation of the coating: Prepare the coating according to the coating components and their mass percentages and stir evenly;

[0108] S2. First coating: Coat Coating A on the inner cavity surface of the sand mold and ignite for drying;

[0109] S3. Second coating: On the basis of S2, further coat Coating A on the inner cavity surface of the sand mold and ignite for drying; to form a double-layer structure.

[0110] Among them, the coating thickness of Coating A is 0.7 mm; the set drying temperature is 150 °C and the set drying time is 30 minutes.

[0111] Comparative Example 2

[0112] This comparative example provides a sulfur-proof coating on the surface of resin sand castings, including Coating B;

[0113] The components of Coating B and the mass percentages of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, sulfur-proof agent 16%, auxiliary agent 1.01%, second spheroidizing agent 5%, and the balance is ethanol; among them, the second spheroidizing agent is a coated spheroidizing agent, which is formed by immersing the first spheroidizing agent in a molten salt bath of a NaCl-KCl mixed salt, physically adsorbing on the surface of the first spheroidizing agent, and cooling and solidifying to form a coating layer with a thickness of 10-50 μm;

[0114] The first spheroidizing agent is a 3-8 spheroidizing agent, and its components are as follows: 7.0% ≤ Mg (wt%) < 9.0%, 2.5% ≤ RE (wt%) < 4.0%, 35.0% ≤ Si (wt%) < 44.0%, 2.0% ≤ Ca (wt%) ≤ 3.5%, 0.5% ≤ Ti (wt%) ≤ 1.0%, 4.0% ≤ Mn (wt%) ≤ 5.0%, Al (wt%) ≤ 1.0%, and the balance is Fe;

[0115] The components of the auxiliary agent and the mass percentages of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

[0116] Among them, the particle size of the first spheroidizing agent is 235 mesh; after Coating B is stirred evenly, the Baume degree of the coating solution is measured with a Baume hydrometer so that the Baume degree of Coating B is 40; the sulfur-proof agent includes sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3, and the mass percentages of sulfur-proof agent FS-1, sulfur-proof agent FS-2, and sulfur-proof agent FS-3 are 29.4%, 58.8%, and 11.8% respectively.

[0117] A method for coating a resin sand casting surface with a sulfur-proof coating includes the following steps:

[0118] S1. Preparation of the coating: Prepare the coating according to the coating components and the mass percentages of each component, and stir evenly;

[0119] S2. First coating: Coat Coating B on the inner cavity surface of the sand mold, and ignite and dry it;

[0120] S3. Second coating: On the basis of S2, further coat Coating B on the inner cavity surface of the sand mold, and ignite and dry it; a double-layer structure is formed.

[0121] Among them, the coating thickness of Coating B is 0.7 mm; the set drying temperature is 150 °C, and the set drying time is 30 minutes.

[0122] The thickness of the flake graphite layer on the surface of ductile iron in Examples 1 to 7, Comparative Example 1, and Comparative Example 2 was detected, and the coating properties of each example and comparative example were monitored, and the following table was obtained:

[0123]

[0124] As can be seen from the above table: In the present invention, the double-layer coating of Coating A + Coating B can not only obtain a reaction layer with high compressive strength and good nodulizing effect supplementation, eliminate the thickness of flake graphite in ductile iron, but also have a lower defective rate compared with a single double-layer coating; and as can be seen from the above table, the effect of Example 2 is the best, eliminating the thickness of flake graphite in the casting, and having high compressive strength and low defective rate.

[0125] In the present invention, Coating A is coated between Coating B and the casting. When pouring molten iron, it first contacts Coating A. Since the content of nodulizer in Coating A is relatively low, it can ensure the overall structural strength of the coating. At the same time, Mg in the nodulizer in Coating A is released at high temperature to supplement the residual Mg consumed by sulfur on the surface of the molten iron and restore the formation ability of nodulizing cores; Coating B is coated between Coating A and the sand mold. Coating A that the molten iron first contacts forms a dense barrier layer. Moreover, the nodulizer in Coating B is processed into a coated nodulizer, and the coating layer slows down the premature reaction of the nodulizer with the coating binder, avoiding the generation of excessive brittle compounds and maintaining the compressive strength of the coating. At the same time, the coating layer gradually melts during the pouring of molten iron, gradually releasing the active elements in the nodulizer, avoiding the violent boiling reaction of Mg in the active elements. The active elements react with the sulfur-containing gas released by the decomposition of the resin sand to form stable sulfides, preventing sulfur from diffusing into the molten iron. Therefore, the coating of the present invention not only has high compressive strength, but also has good sulfur-containing gas neutralization effect and nodulizing effect supplementation, further reducing the defective rate of the product.

[0126] In the present invention, the binder and thickener provided in the coating can strengthen the joint of Coating A and Coating B and ensure the structural function stability of the joint.

[0127] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. Anti-sulfur coating on the surface of resin sand casting, characterized in that: The anti-sulfur coating comprises coating A and coating B; coating A is applied between coating B and the casting, and coating B is applied between coating A and the sand mold; The coating A component and the mass percentage of each component are as follows: zircon powder 53%, phenolic resin 1.6%, vegetable gum 0.2%, modified clay 1%, anti-sulfurization agent 17%, auxiliary agent 1.01%, first spheroidizer 2.5%~3%, and the rest is ethanol; the first spheroidizer is 3-8 spheroidizer, and its composition is: 7.0%≤Mg (wt%) <9.0%, 2.5%≤RE (wt%) <4.0%, 35.0%≤Si (wt%) <44.0%, 2.0%≤Ca (wt%) ≤3.5%, 0.5%≤Ti (wt%) ≤1.0%, 4.0%≤Mn (wt%) ≤5.0%, Al (wt%) ≤1.0%, and the balance is Fe; The coating B component and the mass percentage of each component are as follows: 53% zircon powder, 1.6% phenolic resin, 0.2% vegetable gum, 1% modified clay, 16% anti-sulfurization agent, 1.01% auxiliary agent, 5% second spheroidizer, and the rest is ethanol; the second spheroidizer is an encapsulated spheroidizer, which is obtained by immersing the first spheroidizer in a molten salt bath, physically adsorbing on the surface of the first spheroidizer, and cooling and solidifying to form a 10-50 μm coating layer; The auxiliary agent components and the mass percentage of each component are as follows: dispersant 9.9%, surfactant 3%, thickener 29.7%, penetrant 29.7%, defoamer 7.9%, preservative 19.8%.

2. The anti-sulfurization coating on the surface of resin sand casting according to claim 1, characterized in that: The molten salt bath adopts NaCl-KCl mixed salt, and the eutectic melting point temperature required for heating for the melting is 650-700°C.

3. The anti-sulfurization coating on the surface of resin sand casting according to claim 2, characterized in that: After the first spheroidizer is immersed in a molten salt bath and cooled and solidified to form a 10-50 μm coating layer, the second spheroidizer particles and the crushed salt slag are separated by mechanical crushing and vibration screening.

4. The anti-sulfurization coating on the surface of resin sand casting according to claim 2, characterized in that: The particle size of the first spheroidizing agent is 235 meshes.

5. The anti-sulfurization coating on the surface of resin sand casting according to claim 2, characterized in that: After the coating A and coating B are stirred evenly, the Baume degree of the coating solution is measured using a Baume specific gravity meter, so that the Baume degree of coating A is 35-40 and the Baume degree of coating B is 39-45.

6. The anti-sulfurization coating on the surface of resin sand casting according to claim 2, characterized in that: The anti-sulfurization agent includes anti-sulfurization agent FS-1, anti-sulfurization agent FS-2 and anti-sulfurization agent FS-3, and the mass percentages of the anti-sulfurization agent FS-1, anti-sulfurization agent FS-2 and anti-sulfurization agent FS-3 are 29.4%, 58.8% and 11.8% respectively.

7. A coating method, characterized in that: The coating method is applied to the anti-sulfurization coating on the surface of the resin sand casting according to any one of claims 1 to 6, and the coating method comprises the following steps: S1. Preparation of coating: prepare the coating according to the coating composition and the mass percentage of each component, and stir evenly; S2, coating of coating B: coating coating B on the inner surface of the sand mold, igniting and drying; S3. Coating of coating A: Based on S2, coating A is further coated on the inner surface of the sand mold, and ignited and dried to form a double-layer structure of coating B + coating A.

8. A coating method according to claim 7, characterized in that: The coating thickness of the coating A is 0.2-0.4 mm, and the coating thickness of the coating B is 0.3-0.4 mm.

9. A coating method according to claim 7, characterized in that: The drying setting temperature of the coating B and the coating A is 140-160° C., and the drying setting time is 25-35 minutes.

Images