Green Sand Mold Cured Layer for Hardness and Permeability
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Solution Overview
Problem
Conventional green sand molds for iron-based castings face issues with sand detachment during mold shakeout and gas defects due to insufficient hardness and permeability, leading to poor dimensional accuracy and appearance.
Innovation Solution
A green sand mold with deformable mating surfaces coated with a thermosetting resin curing material, which is heat-hardened to achieve the desired hardness and permeability, preventing sand detachment and gas defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the green sand mold parts are coated with water glass and cured with CO2 gas, then sand detachment is suppressed, but the cavity of the green sand mold is deformed due to the weight of the mold and flask
Solution Approach 1:
The patent applies a low-viscosity curing material to the green sand mold parts before combining them. This preliminary coating creates a hardened layer on the mating surfaces that provides sufficient strength to support the mold weight without causing cavity deformation, thus resolving the contradiction between needing hardness and avoiding deformation.
Solution Approach 2:
The patent changes the viscosity parameter of the curing material by selecting materials with viscosity of 1-100 mPa·S, which allows the material to penetrate deeply into the green sand structure. This parameter change enables the formation of a hardened layer that maintains both strength and dimensional stability, preventing cavity deformation while suppressing sand detachment.
2Strength
If a large amount of solidifying liquid is coated to obtain sufficient hardness, then sand detachment is suppressed, but the casting mold has extremely low gas permeability causing gas defects
Solution Approach 1:
The patent optimizes the viscosity parameter of the curing material to 1-100 mPa·S, which allows deep penetration into the green sand structure without requiring excessive amounts of material. This parameter optimization achieves sufficient hardness while maintaining gas permeability, preventing gas defects like pinholes in the casting.
Solution Approach 2:
The patent utilizes the porous structure of green sand and selects curing materials that penetrate and harden within this porous structure. The low-viscosity curing material infiltrates the sand pores and hardens in place, maintaining the porous structure's gas permeability while providing the necessary hardness to suppress sand detachment.
3Strength
If the mold parts are combined after the furan resin binder is completely cured, then hardness is sufficient, but the mating surfaces do not come into close contact resulting in gaps
Solution Approach 1:
The patent applies the curing material to the green sand mold parts before combining them, allowing the material to penetrate and begin hardening in place. This preliminary action ensures that when the parts are combined, the mating surfaces have sufficient hardness and can still achieve close contact, eliminating gaps while maintaining dimensional accuracy.
Solution Approach 2:
The patent changes the viscosity parameter of the curing material to 1-100 mPa·S, enabling deep penetration into the green sand structure before hardening. This parameter change allows the material to form a hardened layer that maintains both sufficient hardness and the deformability needed for mating surfaces to come into close contact, preventing gaps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method produces iron-based castings with excellent dimensional accuracy and appearance by ensuring sufficient hardness and permeability in the green sand mold, reducing sand detachment and gas defects like pinholes.
Implementation Method 1
a cured layer comprising a thermosetting resin as a main component being formed on the recess and mating surface of each green sand mold part
Implementation Method 2
charging green sand containing about several percentages of water, a clay, etc. into each flask 11, and then compressing it
Implementation Method 3
causing a CO 2 gas to pass through the combined green sand mold parts to cure the water glass
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
A green sand mold comprising at least one pair of green sand mold parts each comprising a recess and a mating surface, wherein a cured layer comprising a thermosetting resin as a main component is formed on the recess and mating surface of each green sand mold part, and wherein the cured layer has hardness of 40-98, a thickness of 0.5-6 mm, and gas permeability of 70-150, is produced by applying a curing material comprising the thermosetting resin as a main component and having viscosity of 1-100 mPa·S to the recess and mating surface of each green sand mold part, combining the green sand mold parts, and then heat-hardening the curing material.