Shelling resistant pre-coated sand and preparation method thereof

Abstract

The invention discloses shelling resistant pre-coated sand and a preparation method thereof. The shelling resistant pre-coated sand is characterized by comprising raw sand, a bonding agent the weight of which is 1-4% that of the raw sand, a curing agent the weight of which is 1-15% that of the bonding agent, 0.1-0.5% of coupling agent and 0.1-1.0% of additive. By adding the additive, the curing speed of the curing agent to the bonding agent is increased, the hardening rate of the pre-coated sand is improved and the shelling tendency is reduced; by optimizing the content of each component, the overall strength of the pre-coated sand is improved, the gas evolution amount of the pre-coated sand is greatly reduced and the defect of core piercing is alleviated; the shelling resistant pre-coated sand has strong shell resistance, is high in strength and low in gas evolution amount, is capable of remarkably alleviating or eliminating defects such as shelling and core piercing and effectively improving qualities of the inner and outer surface of a shell core, and is suitable for production of shell core sand cores.

Description

technical field

[0001] The invention relates to the technical field of coated sand, in particular to a shell-resistant coated sand and a preparation method thereof. Background technique

[0002] Coated sand refers to the molding sand or core sand that is covered with a solid resin film on the surface of the sand grains before molding. There are two coating processes: cold method and hot method: the cold method dissolves the resin with ethanol, and adds urotropine during the sand mixing process, so that the two are coated on the surface of the sand grains, and the ethanol volatilizes to obtain coated sand; Preheat the sand to a certain temperature, add resin to melt, stir to coat the resin on the surface of the sand, add urotropine aqueous solution and lubricant, cool, crush, and sieve to obtain coated sand. Due to the advantages of high strength, low gas generation, high dimensional accuracy of production castings, smooth surface and easy storage, coated sand is widely used...

Examples

Embodiment 1

[0020] Put the raw sand composed of 70% quartz sand and 30% phase-change quartz sand according to the mass into the sand mixer, heat it to 120°C, add a coupling agent accounting for 0.1% of the binder mass, and carry out the first 5s Mix it once. Next, add a binder accounting for 1% of the mass of the original sand, and carry out the second mixing and grinding for 25 seconds. Then, add 0.1% additive and 3% curing agent accounting for the mass of the binder, and carry out the third mixing and grinding for 45s. Finally, after adding 1% lubricant to the mass of the binder and stirring evenly, the temperature was lowered to 60°C, crushed and sieved to obtain coated sand.

Embodiment 2

[0022] Put the raw sand composed of 90% quartz sand and 10% phase-change quartz sand according to the mass into the sand mixer, heat it to 130°C, add a coupling agent accounting for 0.5% of the binder mass, and carry out the first 10s Mix it once. Next, add a binder accounting for 4% of the mass of the original sand, and carry out the second mixing and grinding for 15 seconds. Then, add 1.0% additives and 15% curing agent accounting for the mass of the binder, and carry out the third mixing and grinding for 30 seconds. Finally, after adding 5% of the lubricant in the mass of the binder and stirring evenly, the temperature was lowered to 70°C, crushed and sieved to obtain coated sand.

Embodiment 3

[0024] Put the raw sand composed of 80% quartz sand and 20% phase-change quartz sand according to the mass into the sand mixer, heat it to 140°C, add a coupling agent accounting for 0.3% of the binder mass, and carry out the first 8s. Mix it once. Next, add a binder accounting for 2.5% of the mass of the original sand, and carry out the second mixing and grinding for 20 seconds. Then, add 0.6% additives and 10% curing agent accounting for the mass of the binder, and carry out the third mixing and milling for 60s. Finally, after adding 3% lubricant in the mass of the binder and stirring evenly, the temperature was lowered to 80°C, crushed and sieved to obtain coated sand.

technical field

[0001] The invention relates to the technical field of coated sand, in particular to a shell-resistant coated sand and a preparation method thereof. Background technique

[0002] Coated sand refers to the molding sand or core sand that is covered with a solid resin film on the surface of the sand grains before molding. There are two coating processes: cold method and hot method: the cold method dissolves the resin with ethanol, and adds urotropine during the sand mixing process, so that the two are coated on the surface of the sand grains, and the ethanol volatilizes to obtain coated sand; Preheat the sand to a certain temperature, add resin to melt, stir to coat the resin on the surface of the sand, add urotropine aqueous solution and lubricant, cool, crush, and sieve to obtain coated sand. Due to the advantages of high strength, low gas generation, high dimensional accuracy of production castings, smooth surface and easy storage, coated sand is widely used...

Examples

Embodiment 1

[0020] Put the raw sand composed of 70% quartz sand and 30% phase-change quartz sand according to the mass into the sand mixer, heat it to 120°C, add a coupling agent accounting for 0.1% of the binder mass, and carry out the first 5s Mix it once. Next, add a binder accounting for 1% of the mass of the original sand, and carry out the second mixing and grinding for 25 seconds. Then, add 0.1% additive and 3% curing agent accounting for the mass of the binder, and carry out the third mixing and grinding for 45s. Finally, after adding 1% lubricant to the mass of the binder and stirring evenly, the temperature was lowered to 60°C, crushed and sieved to obtain coated sand.

Embodiment 2

[0022] Put the raw sand composed of 90% quartz sand and 10% phase-change quartz sand according to the mass into the sand mixer, heat it to 130°C, add a coupling agent accounting for 0.5% of the binder mass, and carry out the first 10s Mix it once. Next, add a binder accounting for 4% of the mass of the original sand, and carry out the second mixing and grinding for 15 seconds. Then, add 1.0% additives and 15% curing agent accounting for the mass of the binder, and carry out the third mixing and grinding for 30 seconds. Finally, after adding 5% of the lubricant in the mass of the binder and stirring evenly, the temperature was lowered to 70°C, crushed and sieved to obtain coated sand.

Embodiment 3

[0024] Put the raw sand composed of 80% quartz sand and 20% phase-change quartz sand according to the mass into the sand mixer, heat it to 140°C, add a coupling agent accounting for 0.3% of the binder mass, and carry out the first 8s. Mix it once. Next, add a binder accounting for 2.5% of the mass of the original sand, and carry out the second mixing and grinding for 20 seconds. Then, add 0.6% additives and 10% curing agent accounting for the mass of the binder, and carry out the third mixing and milling for 60s. Finally, after adding 3% lubricant in the mass of the binder and stirring evenly, the temperature was lowered to 80°C, crushed and sieved to obtain coated sand.

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