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CN-122007326-A - High-strength high-toughness precoated sand and preparation method thereof

CN122007326ACN 122007326 ACN122007326 ACN 122007326ACN-122007326-A

Abstract

The invention belongs to the technical field of casting materials, and discloses high-strength high-toughness precoated sand and a preparation method thereof. The precoated sand comprises, by weight, 100 parts of raw sand, 3-8 parts of a composite modified binder, 0.7-2.9 parts of a multifunctional composite additive, 0.3-0.8 parts of a curing agent and 0.1-0.3 parts of a lubricant, wherein the composite modified binder consists of thermoplastic phenolic resin, a toughening modifier and a reinforcing modifier, and the multifunctional composite additive comprises a reinforcing filler, a toughening filler and an auxiliary function filler. By introducing a flexible toughening component and an interface reinforcing component into the binder system and combining the synergistic effect of the nanoscale reinforcing filler and the thermal decomposition toughening filler, the bending strength and the impact toughness of the precoated sand are obviously improved on the premise of ensuring the gas generation amount and the collapsibility.

Inventors

  • CHENG GUANGMING
  • MA CHUANFU
  • LIU CHENGXIANG
  • Qin Liusong

Assignees

  • 南阳仁创砂业科技有限公司

Dates

Publication Date
20260512
Application Date
20260302

Claims (10)

  1. 1. The high-strength high-toughness precoated sand is characterized by comprising, by weight, 100 parts of raw sand, 3-8 parts of a composite modified binder, 0.7-2.9 parts of a multifunctional composite additive, 0.3-0.8 part of a curing agent and 0.1-0.3 part of a lubricant; the composite modified binder consists of thermoplastic phenolic resin, a toughening modifier and a reinforcing modifier, wherein the weight ratio of the thermoplastic phenolic resin to the toughening modifier to the reinforcing modifier is 100 (5-15) (2-8); the multifunctional composite additive consists of 0.3-1.1 parts of reinforcing filler, 0.25-1.0 parts of toughening filler and 0.15-0.8 parts of auxiliary functional filler.
  2. 2. The high-strength high-toughness precoated sand as claimed in claim 1, wherein the toughening modifier is a mixture of polyamide and liquid nitrile rubber, the weight ratio of the polyamide to the liquid nitrile rubber is 1 (0.8-1.2), and the reinforcing modifier is a mixture of a silane coupling agent KH560 and cardanol, and the weight ratio of the silane coupling agent KH560 to the cardanol is 1 (1.5-2.5).
  3. 3. The high-strength high-toughness precoated sand as claimed in claim 1, wherein the reinforcing filler is nano-scale graphite powder with the particle size of 50-100 nm, the toughening filler is one or more selected from alpha starch, beta starch and dextrin, and the auxiliary functional filler is one selected from molybdenum disulfide or boron nitride.
  4. 4. The high-strength high-toughness precoated sand according to claim 1, wherein the raw sand is silica sand subjected to surface coupling treatment, the grain size is 70-140 meshes, the curing agent is urotropine, and the lubricant is one or more selected from calcium stearate, zinc stearate, magnesium stearate and paraffin.
  5. 5. The high strength, high toughness precoated sand of claim 1 wherein said thermoplastic phenolic resin has a softening point of 85 to 105 ℃.
  6. 6. The high-strength high-toughness precoated sand of claim 1, wherein the acrylonitrile content of the liquid nitrile rubber is 25-35% and the number average molecular weight is 2000-5000.
  7. 7. A method for preparing the high-strength high-toughness precoated sand as claimed in claim 1, comprising the following steps: s1, heating thermoplastic phenolic resin to a molten state, sequentially adding a toughening modifier and a reinforcing modifier, and mixing to obtain a composite modified adhesive; s2, uniformly mixing the reinforced filler, the toughened filler and the auxiliary functional filler to obtain the multifunctional composite additive; S3, roasting raw sand, cooling, adding a silane coupling agent for surface modification, and grading and mixing sand grains with different particle sizes; S4, heating the raw sand treated in the step S3, mixing with the composite modified binder obtained in the step S1, and sequentially adding the multifunctional composite additive, the curing agent and the lubricant obtained in the step S2 for mixing; s5, cooling and screening the material subjected to the film coating to obtain the high-strength high-toughness film coating sand.
  8. 8. The method for preparing high-strength and high-toughness precoated sand according to claim 7, wherein in the step S1, thermoplastic phenolic resin is heated to 80-90 ℃ and kept at the temperature, a toughening modifier and a reinforcing modifier are sequentially added, stirring is carried out for 30-40min at 80-90 ℃ at the stirring rate of 150-200 r/min, and then cooling is carried out to room temperature, so that the composite modified binder is obtained.
  9. 9. The method for preparing high-strength and high-toughness precoated sand as claimed in claim 7, wherein in the step S3, raw sand is placed in a roasting furnace for roasting for 2-3 hours, cooled to 100-120 ℃, silane coupling agent KH560 accounting for 0.1-0.2% of the weight of the raw sand is added for mixing treatment for 15-20 min, and then sand grains with different grain size grades are mixed according to a weight ratio of 2:1.
  10. 10. The method for preparing high-strength and high-toughness precoated sand according to claim 7, wherein in the step S4, the pretreated raw sand is heated to 120-140 ℃, a composite modified binder is added for mixing, then the temperature of the material is adjusted to 90-110 ℃, and a curing agent and a lubricant are added and mixing is continued.

Description

High-strength high-toughness precoated sand and preparation method thereof Technical Field The invention belongs to the technical field of casting materials, and particularly relates to high-strength high-toughness precoated sand and a preparation method thereof. Background The precoated sand is a casting molding sand material which is prepared by taking raw sand as aggregate, taking thermoplastic phenolic resin as a main binder, heating, coating and adding a curing agent, and is widely applied to shell mold casting and core making processes. The precoated sand has the advantages of high molding precision, good surface quality and simple operation, and is widely applied to the production of automobile engine cylinder bodies, cylinder covers and various complex thin-wall castings. However, as the casting structure is increasingly complex and the dimensional accuracy requirements are continuously improved, higher requirements are put on the comprehensive performance of precoated sand, and especially the cooperative improvement in the aspects of strength and toughness becomes an important point of industry attention. In the prior art, precoated sand generally adopts single thermoplastic phenolic resin as a binder, and the resin has high crosslinking density and strong structural rigidity, and can provide higher normal-temperature bending strength, but has lower elongation at break and poorer impact resistance, and is easy to generate brittle fracture in the processes of carrying, core falling or filling of complex cavities. In addition, the simple increase of the resin addition amount for improving the strength can lead to the increase of the gas generation amount and the increase of the casting air hole defects, and simultaneously influence the collapsibility, so that the subsequent cleaning is not facilitated. Part of technical schemes try to improve the performance by adding rubber toughening agents or inorganic fillers, but only single performance is often improved, and the problems of insufficient interfacial compatibility, uneven system dispersion or strength reduction are easily generated, so that the synchronous improvement of the strength and the toughness is difficult to realize. Therefore, how to improve the strength, toughness and comprehensive performance of precoated sand through the synergistic effect of the structural design of the binder and various functional fillers on the premise of not remarkably increasing the resin consumption becomes a technical problem to be solved in the field. Disclosure of Invention In order to solve the defects in the background art, the invention aims to provide high-strength high-toughness precoated sand and a preparation method thereof, and the synergistic effect of interface enhancement and toughness regulation is realized by constructing a composite modified binder system consisting of thermoplastic phenolic resin, a toughening modifier and a reinforcing modifier and combining the reinforcing filler, the toughening filler and an auxiliary functional filler to form a multifunctional composite additive. On the premise of controlling the resin dosage, the flexural strength and impact toughness of the precoated sand are obviously improved, and the air release, collapsibility and fluidity are simultaneously considered, so that the preparation process is stable and is suitable for industrial application. The aim of the invention can be achieved by the following technical scheme: The high-strength high-toughness precoated sand comprises, by weight, 100 parts of raw sand, 3-8 parts of a composite modified binder, 0.7-2.9 parts of a multifunctional composite additive, 0.3-0.8 part of a curing agent and 0.1-0.3 part of a lubricant; the composite modified binder consists of thermoplastic phenolic resin, a toughening modifier and a reinforcing modifier, wherein the weight ratio of the thermoplastic phenolic resin to the toughening modifier to the reinforcing modifier is 100 (5-15) (2-8); the multifunctional composite additive consists of 0.3-1.1 parts of reinforcing filler, 0.25-1.0 parts of toughening filler and 0.15-0.8 parts of auxiliary functional filler. Further preferably, the toughening modifier is a mixture of polyamide and liquid nitrile rubber, the weight ratio of the polyamide to the liquid nitrile rubber is 1 (0.8-1.2), the reinforcing modifier is a mixture of a silane coupling agent KH560 and cardanol, and the weight ratio of the silane coupling agent KH560 to the cardanol is 1 (1.5-2.5). Further preferably, the reinforced filler is nano-scale graphite powder with the particle size of 50-100 nm, the toughened filler is selected from one or more of alpha starch, beta starch and dextrin, and the auxiliary functional filler is selected from one of molybdenum disulfide or boron nitride. Further preferably, the raw sand is silica sand subjected to surface coupling treatment, the particle size is 70-140 meshes, the curing agent is urotropine, and the lubricant is o