Shell Mold Heat Transfer Control for Shrinkage Defects

Solution Overview

Problem

Conventional investment casting methods result in shrinkage holes due to heat expansion/cold shrinkage or different cooling rates, leading to raw material loss, reduced yield, and increased costs, as replenishing holes are necessary to avoid these defects.

Innovation Solution

A method to manufacture shell molds by adjusting the heat transfer rate to shift shrinkage holes to a predetermined location, using varying thickness and thermal conductivity materials, and employing 3D printing techniques to control the hardening direction of molten metal, thereby minimizing shrinkage defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If replenishing holes are added in the shell mold to avoid shrinkage holes, then casting quality is improved, but raw material loss rate increases and yield decreases

Engineering Contradiction:

Improvecasting qualityVSAvoidraw material loss rate

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent changes the thermal conductivity parameter of the shell mold by incorporating phase change materials with different thermal conductivities in different regions. This allows control over the solidification sequence of molten metal, directing shrinkage holes to non-critical areas without requiring replenishing holes, thereby reducing material loss while maintaining casting quality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating regions with different thermal conductivities within the shell mold. Phase change materials with higher thermal conductivity are placed in regions where rapid cooling is desired, while materials with lower thermal conductivity are used in regions where slower cooling is preferred, enabling precise control over solidification patterns and shrinkage hole locations.

Inventive Principle:

Principle #3Local quality

2Reliability

If replenishing holes are added in the shell mold to avoid shrinkage holes, then casting quality is improved, but treatment costs increase

Engineering Contradiction:

Improvecasting qualityVSAvoidtreatment costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the thermal conductivity parameter of the shell mold by incorporating phase change materials with different thermal conductivities in different regions. This allows control over the solidification sequence of molten metal, directing shrinkage holes to non-critical areas without requiring replenishing holes, thereby reducing material loss while maintaining casting quality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts the function of shrinkage hole control from the traditional approach of adding replenishing holes and instead achieves it through thermal conductivity adjustment in the mold structure itself. This eliminates the need for additional replenishing holes and their associated treatment costs.

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If the shell mold thickness is increased to control hardening direction, then shrinkage hole location is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveshrinkage hole location controlVSAvoidshell mold structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent uses composite materials consisting of phase change materials with different thermal conductivities embedded in the shell mold structure. This allows control over heat transfer and solidification patterns without significantly increasing overall mold thickness, managing complexity through material composition rather than geometric complexity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by creating regions with different thermal conductivities within the shell mold. Phase change materials with higher thermal conductivity are placed in regions where rapid cooling is desired, while materials with lower thermal conductivity are used in regions where slower cooling is preferred, enabling precise control over solidification patterns and shrinkage hole locations.

Inventive Principle:

Principle #3Local quality

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

This approach enhances casting quality by precisely controlling the location of shrinkage holes, reducing material loss and treatment costs, and improving the shell mold formation process.

Implementation Method 1

adjustment of a heat transfer rate of the shell mold... the hardening direction of the molten metal in the shell mold can be controlled to shift the shrinkage hole

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

when the molten metal hardens, a shrinkage hole is generated due to heat expansion/cold shrinkage

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

shrinkage hole is generated due to heat expansion/cold shrinkage

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS11267044B2Method for manufacturing a shell mold

Publication Date: 2022.03.08 METAL INDS RES & DEV CENT

AI summary

A method for manufacturing a mold includes providing first information regarding a location of a shrinkage hole generated during hardening of a molten metal in a shell mold. Second information regarding a change in the location of the shrinkage hole in response to adjustment of a heat transfer rate of the shell mold is obtained. The heat transfer rate of the shell mold is adjusted to shift the shrinkage hole to a predetermined location.