A special coating for cast iron lost foam casting and a preparation method thereof

Abstract

The application discloses a special lost foam casting coating for cast iron and a preparation method thereof. The lost foam casting coating is prepared from the following raw materials: water, refractory material, binder and additive. The refractory material is prepared from the following raw materials: 40-70 mesh quartz sand, 200 mesh quartz powder, 70-140 mesh kyanite and graphite powder. The binder is prepared from the following raw materials: silica sol, white emulsion, phenolic resin and calcium bentonite. The additive is prepared from the following raw materials: potassium permanganate, isopropyl alcohol, polyacrylamide and sodium carboxymethyl cellulose. The lost foam casting coating prepared by the above-mentioned formula has the following advantages: good coating air permeability, good strength, good wetting and adhesion, fast drying speed, small gas evolution and the like, and breaks the related technical barriers of foreign countries, so that the domestic lost foam coating realizes the purposes of low price and excellent performance, and the one-time pouring qualified rate of castings reaches more than 98%.

Description

Technical Field

[0001] This invention belongs to the field of lost foam casting technology, and in particular relates to a lost foam casting coating for cast iron and its preparation method. Background Technology

[0002] Currently, in the application of lost foam casting technology both domestically and internationally, the coatings used for gray cast iron and ductile iron are largely incompatible. Ductile iron, due to its higher carbon content after the white foam atomization, requires a different coating than gray cast iron, and the quality of various coatings varies considerably. Domestically, the price ranges from 3000-4000 RMB per ton, while imported coatings cost 6000-8000 RMB per ton, making them quite expensive. There is currently no domestically produced lost foam coating specifically for cast iron that is inexpensive, high-performance, and environmentally friendly. Since the coating is a key factor determining the first-time casting success rate, imported coatings can achieve a first-time casting success rate of over 95%, but they are extremely expensive. Even the best domestically produced coatings only achieve a success rate of 80%-85%, which increases production costs and reduces profit margins for lost foam casting manufacturers. Therefore, breaking through foreign technological barriers and developing a low-cost, high-performance, versatile, and environmentally friendly lost foam coating specifically for cast iron is crucial for promoting the development of the domestic lost foam casting industry. Summary of the Invention

[0003] The purpose of this invention is to provide a special lost foam casting coating for cast iron and its preparation method in order to solve the above-mentioned problems. This invention breaks through the relevant technical barriers abroad, enabling domestic lost foam coatings to achieve low price and excellent performance, and achieving a first-time casting qualification rate of over 98%. The price of each ton of coating is RMB 1,800-2,000, which strongly promotes the development of the domestic lost foam casting industry.

[0004] The present invention achieves the above objectives through the following technical solutions: A lost foam casting coating specifically for cast iron is prepared from the following raw materials: water, refractory materials, binder and additives; The refractory material is prepared from the following raw materials: 40-70 mesh quartz sand, 200 mesh quartz powder, 70-140 mesh kyanite, and graphite powder; The adhesive is prepared from the following raw materials: silica sol, white glue, phenolic resin and calcium bentonite; The additive is prepared from the following raw materials: potassium permanganate, isopropanol, polyacrylamide, and sodium carboxymethyl cellulose.

[0005] One of the lost foam casting coatings for cast iron is prepared from the following raw materials by weight: 30-50 parts water, 8-12 parts 40-70 mesh quartz sand, 2-6 parts 200 mesh quartz powder, 26-30 parts 70-140 mesh kyanite, 1-3 parts graphite powder, 1-5 parts silica sol, 3-7 parts white latex, 1-3 parts phenolic resin, 1-5 parts calcium bentonite, 0.2-0.8 parts isopropanol, 0.3-0.7 parts polyacrylamide, 0.5-1.5 parts sodium carboxymethyl cellulose, and 0.0025-0.0075 parts potassium permanganate.

[0006] As the preferred embodiment, it is prepared from the following raw materials by weight: 40 parts water, 10 parts 40-70 mesh quartz sand, 4 parts 200 mesh quartz powder, 28 parts 70-140 mesh kyanite, 2 parts graphite powder, 3 parts silica sol, 5 parts white latex, 2 parts phenolic resin, 3 parts calcium bentonite, 0.5 parts isopropanol, 0.5 parts polyacrylamide, 1 part sodium carboxymethyl cellulose, and 0.005 parts potassium permanganate.

[0007] One embodiment of the invention is prepared from the following raw materials by weight: 30 parts water, 8 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 1 part graphite powder, 1 part silica sol, 3 parts white latex, 1 part phenolic resin, 1 part calcium bentonite, 0.2 parts isopropanol, 0.3 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

[0008] One embodiment of the invention is prepared from the following raw materials by weight: 50 parts water, 12 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 3 parts graphite powder, 5 parts silica sol, 7 parts white latex, 3 parts phenolic resin, 5 parts calcium bentonite, 0.8 parts isopropanol, 0.7 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.

[0009] One embodiment of the invention is prepared from the following raw materials by weight: 30 parts water, 12 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 1 part graphite powder, 5 parts silica sol, 3 parts white latex, 3 parts phenolic resin, 1 part calcium bentonite, 0.8 parts isopropanol, 0.3 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

[0010] One embodiment is prepared from the following raw materials by weight: 50 parts water, 8 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 3 parts graphite powder, 1 part silica sol, 7 parts white latex, 1 part phenolic resin, 5 parts calcium bentonite, 0.2 parts isopropanol, 0.7 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.

[0011] This invention also provides a method for preparing a lost foam casting coating for cast iron, comprising the following steps: Step 1: Add water to the blender; Step 2: Add silica sol, white glue, phenolic resin, calcium bentonite, isopropanol, polyacrylamide, sodium carboxymethyl cellulose, and potassium permanganate in sequence, and stir for 2 hours; Step 3: Based on Step 2, add 40-70 mesh quartz sand, 200 mesh quartz powder, and 70-140 mesh kyanite in sequence, and stir for 4 hours.

[0012] The advantages of this invention are as follows: This coating has the following characteristics: 1. The coating has good air permeability. During pattern casting, the gas and liquid generated can be easily extracted from the gaps in the coating by a vacuum pump into the molding sand, resulting in a clean casting.

[0013] 2. Good strength, with both room temperature and high temperature strength. The coating at room temperature is convenient for applying the coating to the white mold and has a certain strength during handling before and after drying; the coating layer must have high refractoriness and a low coefficient of thermal expansion, otherwise, due to the scouring and erosion of the molten metal during the pouring process, the poorly adhered coating layer can easily be washed away and rolled into the casting, causing defects such as sand adhesion and slag inclusion.

[0014] 3. Excellent wettability and adhesion. White mold (EPS STMMA) is a non-polar material with low surface tension, making it difficult for water-based coatings to wet or penetrate. Therefore, a small amount of surfactant and a suitable binder need to be added to the coating. The binder must have good adhesion to the white mold to ensure a refractory coating of a certain thickness on its surface after application. Conversely, poor coating adhesion can result in insufficient or uneven coating thickness, or even discontinuous coating, making it difficult to obtain high-quality castings.

[0015] 4. Fast drying speed. The coating should dry quickly at low temperatures (<60℃) to prevent cracking and form a strong fire-resistant coating. If the drying speed is slow, it will not only affect production efficiency, but the coating may also peel off or lift from the white mold surface because it will not dry and cure for a long time.

[0016] 5. Low gas generation. Once the coating is dried, it must not generate other gases when it comes into contact with the poured high-temperature alloy liquid in the sand mold. Otherwise, the gas generated in the coating will easily cause the coating to collapse and fall off, and the generated gas will also seriously affect the fluid filling stability and filling quality.

[0017] 6. Good flowability and coating properties. The coating of white mold is relatively thick, which requires the coating to have a high yield value and plastic deformation capacity. It is necessary to strictly control the flowability of the coating to improve its coating properties.

[0018] 7. Easy to peel off, with sintering peeling properties. Under the ratio of single-stage and multi-stage refractory materials, combined with the properties of molten metal, low-melting-point alkaline or acidic oxides are added to give it good sintering and peeling properties, which is beneficial for sand removal.

[0019] Breaking through relevant foreign technical barriers, domestically produced lost foam casting coatings can achieve low prices and excellent performance, enabling a first-time casting qualification rate of over 98%, with each ton of coating priced at 1800-2000 yuan, thus powerfully promoting the development of the domestic lost foam casting industry. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0021] Example 1 A lost foam casting coating for cast iron is prepared from the following raw materials by weight: 40 parts water, 10 parts 40-70 mesh quartz sand, 4 parts 200 mesh quartz powder, 28 parts 70-140 mesh kyanite, 2 parts graphite powder, 3 parts silica sol, 5 parts white latex, 2 parts phenolic resin, 3 parts calcium bentonite, 0.5 parts isopropanol, 0.5 parts polyacrylamide, 1 part sodium carboxymethyl cellulose, and 0.005 parts potassium permanganate.

[0022] Example 2 A lost foam casting coating for cast iron is prepared from the following raw materials by weight: 30 parts water, 8 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 1 part graphite powder, 1 part silica sol, 3 parts white latex, 1 part phenolic resin, 1 part calcium bentonite, 0.2 parts isopropanol, 0.3 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

[0023] Example 3 A lost foam casting coating for cast iron is prepared from the following raw materials by weight: 50 parts water, 12 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 3 parts graphite powder, 5 parts silica sol, 7 parts white latex, 3 parts phenolic resin, 5 parts calcium bentonite, 0.8 parts isopropanol, 0.7 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.

[0024] Example 4 A lost foam casting coating for cast iron is prepared from the following raw materials by weight: 30 parts water, 12 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 1 part graphite powder, 5 parts silica sol, 3 parts white latex, 3 parts phenolic resin, 1 part calcium bentonite, 0.8 parts isopropanol, 0.3 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

[0025] Example 5 A lost foam casting coating for cast iron is prepared from the following raw materials by weight: 50 parts water, 8 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 3 parts graphite powder, 1 part silica sol, 7 parts white latex, 1 part phenolic resin, 5 parts calcium bentonite, 0.2 parts isopropanol, 0.7 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.

[0026] This invention also provides a method for preparing a lost foam casting coating for cast iron, comprising the following steps: Step 1: Add water to the blender; Step 2: Add silica sol, white glue, phenolic resin, calcium bentonite, isopropanol, polyacrylamide, sodium carboxymethyl cellulose, and potassium permanganate in sequence, and stir for 2 hours; Step 3: Based on Step 2, add 40-70 mesh quartz sand, 200 mesh quartz powder, and 70-140 mesh kyanite in sequence, and stir for 4 hours.

[0027] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A lost foam casting coating specifically for cast iron, characterized in that: It is prepared from the following raw materials by weight: 30-50 parts water, 8-12 parts 40-70 mesh quartz sand, 2-6 parts 200 mesh quartz powder, 26-30 parts 70-140 mesh kyanite, 1-3 parts graphite powder, 1-5 parts silica sol, 3-7 parts white latex, 1-3 parts phenolic resin, 1-5 parts calcium bentonite, 0.2-0.8 parts isopropanol, 0.3-0.7 parts polyacrylamide, 0.5-1.5 parts sodium carboxymethyl cellulose, and 0.0025-0.0075 parts potassium permanganate.

2. The lost foam casting coating for cast iron according to claim 1, characterized in that: It is prepared from the following raw materials by weight: 40 parts water, 10 parts 40-70 mesh quartz sand, 4 parts 200 mesh quartz powder, 28 parts 70-140 mesh kyanite, 2 parts graphite powder, 3 parts silica sol, 5 parts white latex, 2 parts phenolic resin, 3 parts calcium bentonite, 0.5 parts isopropanol, 0.5 parts polyacrylamide, 1 part sodium carboxymethyl cellulose, and 0.005 parts potassium permanganate.

3. The lost foam casting coating for cast iron according to claim 1, characterized in that: It is prepared from the following raw materials by weight: 30 parts water, 8 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 1 part graphite powder, 1 part silica sol, 3 parts white latex, 1 part phenolic resin, 1 part calcium bentonite, 0.2 parts isopropanol, 0.3 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

4. The lost foam casting coating for cast iron according to claim 1, characterized in that: It is prepared from the following raw materials by weight: 50 parts water, 12 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 3 parts graphite powder, 5 parts silica sol, 7 parts white latex, 3 parts phenolic resin, 5 parts calcium bentonite, 0.8 parts isopropanol, 0.7 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.

5. The lost foam casting coating for cast iron according to claim 1, characterized in that: It is prepared from the following raw materials by weight: 30 parts water, 12 parts 40-70 mesh quartz sand, 2 parts 200 mesh quartz powder, 30 parts 70-140 mesh kyanite, 1 part graphite powder, 5 parts silica sol, 3 parts white latex, 3 parts phenolic resin, 1 part calcium bentonite, 0.8 parts isopropanol, 0.3 parts polyacrylamide, 1.5 parts sodium carboxymethyl cellulose, and 0.0025 parts potassium permanganate.

6. The lost foam casting coating for cast iron according to claim 1, characterized in that: It is prepared from the following raw materials by weight: 50 parts water, 8 parts 40-70 mesh quartz sand, 6 parts 200 mesh quartz powder, 26 parts 70-140 mesh kyanite, 3 parts graphite powder, 1 part silica sol, 7 parts white latex, 1 part phenolic resin, 5 parts calcium bentonite, 0.2 parts isopropanol, 0.7 parts polyacrylamide, 0.5 parts sodium carboxymethyl cellulose, and 0.0075 parts potassium permanganate.