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CN-121988694-A - Heat-resistant precoated sand and preparation method and application thereof

CN121988694ACN 121988694 ACN121988694 ACN 121988694ACN-121988694-A

Abstract

The invention belongs to the technical field of precoated sand, and discloses heat-resistant precoated sand, a preparation method and application thereof, wherein the heat-resistant precoated sand comprises 100 parts of aggregate, 0.2-0.5 part of sintering agent, 0.16-0.3 part of curing agent and 2-5 parts of phenolic resin, the sintering agent comprises an active agent and an accelerator, the active agent comprises silica micropowder, and the accelerator comprises magnesia powder. According to the invention, the silicon micropowder and the magnesia powder are used as sintering agents to wrap the aggregate, latent heat is released when the molten metal is solidified during the preparation of the castings, the temperature of the sand core is gradually increased to more than 800 ℃, the activity of the silicon micropowder in the sintering agents is released at a high temperature, the sintering of sand grains into a compact protective layer can be promoted under the fluxing action of the accelerator MgO, the contact of a high manganese steel material and the aggregate can be avoided, the sand sticking condition of the castings can be avoided, the thermal stress of the castings can be effectively released by the sintering layers, the thermal stability and thermal shock resistance of the castings can be improved, the cracking risk of the castings can be reduced, and the product yield can be improved.

Inventors

  • YIN HAIJUN
  • BAO YUCHONG
  • TANG PIN
  • LIU CHENGXIANG

Assignees

  • 南阳仁创再生资源有限公司

Dates

Publication Date
20260508
Application Date
20260304

Claims (10)

  1. 1. The heat-resistant precoated sand is characterized by comprising 100 parts of aggregate, 0.2-0.5 part of sintering agent, 0.16-0.3 part of curing agent and 2-5 parts of phenolic resin in parts by weight; the sintering agent comprises an active agent and an accelerator, wherein the active agent comprises silica micropowder, the accelerator comprises magnesia powder, and the silica micropowder comprises the magnesia powder=8-10:1 in parts by weight.
  2. 2. The heat resistant precoated sand of claim 1 wherein said fine silica powder and said magnesia powder each have a particle size of 1 to 2 μm, and said fine silica powder and said magnesia powder each have spherical particles.
  3. 3. The heat resistant precoated sand of claim 1 wherein said aggregate is at least one of sea sand, lake sand, aeolian sand.
  4. 4. The heat resistant precoated sand according to claim 1, wherein said curing agent comprises paraformaldehyde having a molecular formula of (CH 2O) n, wherein n = 60-80.
  5. 5. The heat resistant precoated sand according to claim 4, wherein the particle size of the paraformaldehyde is 300 to 500 mesh, and n=70 to 80.
  6. 6. The heat resistant precoated sand of claim 1 further comprising 5 to 10 parts of a lubricant comprising calcium stearate.
  7. 7. A method of preparing the heat resistant precoated sand of any one of claims 1 to 6, comprising the steps of: (1) Uniformly mixing the active agent and the accelerator in a mixer according to a proportion; (2) Heating aggregate to 150-160 ℃, putting the aggregate into a sand mixer, adding the sintering agent uniformly mixed in the step (1) into the sand mixer, and rotating for 60-90s to uniformly coat the sintering agent on the surface of the aggregate; (3) The temperature of the aggregate coated with the sintering agent in the step (2) is reduced to 130-145 ℃, phenolic resin is put into a sand mixer to be mixed with the aggregate coated with the sintering agent, the rotating speed is controlled to be less than or equal to 60R/min, and after the resin is completely melted, the rotating speed is increased to 60-90R/min, and the stirring time is 20-30s; (4) Adding the paraformaldehyde into a sand mixer for mixing, wherein the stirring time is 60-90s, and the rotating speed is 60-70R/min, so that the paraformaldehyde is uniformly coated on the surface of the aggregate coated with the phenolic resin in the step (3) and adsorbed by the resin; (5) Adding a lubricant, controlling the rotating speed at 30-50R/min and the mixing time at 60-90s, so that the sand grains prepared in the step (4) are rapidly dispersed into single grains, and cooling the sand grains to below 50 ℃ to obtain the finished precoated sand.
  8. 8. A method of preparing heat resistant coated sand as claimed in claim 7, further comprising the step of cooling the aggregate after coating the phenolic resin in step (3) to 95-105 ℃, wherein the cooling step comprises blasting air at the bottom of the sand mixer and simultaneously exhausting air at the top of the sand mixer so as to maintain the inside of the sand mixer in a negative pressure state, and the pressure value inside the sand mixer ranges from-8 KPa to-6 KPa.
  9. 9. The method for preparing heat-resistant precoated sand as claimed in claim 7, wherein in the step (1), the rotation speed of the mixer is 120 to 150R/min, and the mixing time is 10 to 20min; The rotating speed in the step (2) is 30-40R/min.
  10. 10. Use of the heat-resistant precoated sand as set forth in any one of claims 1 to 6 in high manganese steel castings.

Description

Heat-resistant precoated sand and preparation method and application thereof Technical Field The invention belongs to the technical field of casting material precoated sand, and particularly relates to heat-resistant precoated sand and a preparation method and application thereof. Background The core of the high manganese steel casting is that the more severely the surface of ‌ is impacted, the higher the hardness, while the core still maintains toughness ‌, which is a unique "work hardening" mechanism, which is widely used in heavy industry. The characteristic of 'external hardness and internal toughness' makes the alloy material ideal for coping with extreme wear conditions. However, the casting process of high manganese steel is very troublesome, because the manganese basic oxide MnO 2 can chemically react with SiO 2 which is made of quartz sand as a core material at high temperature to generate MnO.SiO 2 low-melting-point compounds, so that sand sticking of castings is caused. Secondly, the manganese content is high, so that the heat conductivity is low, the shrinkage rate is large (up to 2.5% -3%), cracks are easy to generate, and the casting is partially cracked and scrapped due to insufficient heat resistance of the molding material. In the prior art, special sand with low SiO 2 content, such as magnesite, chromite sand, baozzle sand, ceramic sand and the like, are adopted to manufacture materials of the mold and the core, but the materials are extremely expensive, have high cost and greatly limit the application of high manganese steel castings. Disclosure of Invention The invention provides a heat-resistant precoated sand and a preparation method and application thereof, wherein the precoated sand provided by the invention adopts silicon micropowder and magnesia powder as sintering agent coated aggregate, latent heat is released along with solidification of molten metal when a casting is manufactured, the temperature of a sand core is gradually increased to more than 800 ℃, the activity of the silicon micropowder in the sintering agent is released in a high-temperature state, sand grains are promoted to be sintered into a compact protective layer under the fluxing action of an accelerator MgO, and the contact of a high manganese steel material and the aggregate is avoided, so that the condition of sand sticking of the casting is avoided. And the sintering layer can effectively release the thermal stress of the casting, improve the thermal stability and thermal shock resistance of the casting, reduce the cracking risk of the casting and improve the yield of products. Specifically, the first object of the invention is to provide a heat-resistant precoated sand, which comprises 100 parts of aggregate, 0.2-0.5 part of sintering agent, 0.16-0.3 part of curing agent and 2-5 parts of phenolic resin in parts by weight; the sintering agent comprises an active agent and an accelerator, wherein the active agent comprises silica micropowder, the accelerator comprises magnesia powder, and the silica micropowder comprises the magnesia powder=8-10:1 in parts by weight. Further, the particle sizes of the silicon micro powder and the magnesium oxide powder are 1-2 mu m, and the silicon micro powder and the magnesium oxide powder are spherical particles Further, the aggregate is at least one of sea sand, lake sand and aeolian sand. Further, the curing agent comprises paraformaldehyde having a molecular formula (CH 2O)n, where n=60-80). Further, the particle size of the paraformaldehyde is 300-500 meshes, and n=70-80. Further, 5-10 parts of lubricant is also included, and the lubricant comprises calcium stearate. The second object of the invention is to provide a method for preparing heat-resistant precoated sand, which is characterized by comprising the following steps: (1) Uniformly mixing the active agent and the accelerator in a mixer according to a proportion; (2) Heating aggregate to 150-160 ℃, putting the aggregate into a sand mixer, adding the sintering agent uniformly mixed in the step (1) into the sand mixer, and rotating for 60-90s to uniformly coat the sintering agent on the surface of the aggregate; (3) The temperature of the aggregate coated with the sintering agent in the step (2) is reduced to 130-145 ℃, phenolic resin is put into a sand mixer to be mixed with the aggregate coated with the sintering agent, the rotating speed is controlled to be less than or equal to 60R/min, and after the resin is completely melted, the rotating speed is increased to 60-90R/min, and the stirring time is 20-30s; (4) Adding the paraformaldehyde into a sand mixer for mixing, wherein the stirring time is 60-90s, and the rotating speed is 60-70R/min, so that the paraformaldehyde is uniformly coated on the surface of the aggregate coated with the phenolic resin in the step (3) and adsorbed by the resin; (5) Adding a lubricant, controlling the rotating speed at 30-50R/min and the mixing time at 60-90s, so that the sand grain