Tapered Insert Joining in Cast Metal Without Blow Holes

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Solution Overview

Problem

Existing methods for joining metallic members with inserts, such as press-fitting and cast-coating, rely heavily on accurate shaping and positioning, which can lead to internal defects and weakened joints due to blow holes and other issues.

Innovation Solution

A method involving semi-cooling a molten metal to a press-fitting temperature higher than the recrystallization temperature of the metal, allowing for press-fitting an insert with a taper into a hole in the metallic member, while maintaining pressure to form a strong junction, and optionally using a mold with pins to manage the insert and molten metal flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If press-fitting is used to join insert to metallic member, then joining strength is improved, but positioning accuracy and shaping accuracy must be high which increases manufacturing complexity

Engineering Contradiction:

Improvejoining strengthVSAvoidpositioning accuracy

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the temperature parameter of the metallic member, heating it to above its recrystallization temperature. This parameter change makes the material more formable and allows the insert to be pressed in without requiring high positioning accuracy, while still achieving strong joining through the thermal expansion and material flow into the insert's taper.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic behavior by heating the metallic member during the press-fitting process. The material transitions from a rigid state at room temperature to a more ductile, formable state at elevated temperature, allowing the hole to dynamically expand and conform to the insert shape, eliminating the need for precise pre-positioning.

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If cast-coating is used to join insert to metallic member, then positioning accuracy dependency is reduced, but internal defects such as blow holes are generated which weaken joining

Engineering Contradiction:

Improvepositioning accuracy dependencyVSAvoidinternal defects

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent uses temperature parameter change (heating above recrystallization temperature) to alter the material's flow characteristics. This enables the metal to flow smoothly around the insert without trapping air or forming blow holes, eliminating internal defects while maintaining low positioning accuracy requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of thermal processing (which could create defects) into a benefit by carefully controlling the heating to above recrystallization temperature. This controlled thermal state allows the metal to flow and fill voids rather than trap them, transforming what could be a defect-generating process into a defect-eliminating process.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Strength

If high positioning accuracy is required for press-fitting, then joining strength is improved, but manufacturing complexity and time increase

Engineering Contradiction:

Improvejoining strengthVSAvoidmanufacturing time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent performs preliminary heating of the metallic member before the press-fitting operation. This preliminary thermal preparation creates a formable state that allows the subsequent press-fitting to proceed quickly without requiring precise positioning adjustments, reducing overall manufacturing time while maintaining strong joining.

Inventive Principle:

Principle #10Preliminary action

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 method enables strong joining of metallic members and inserts regardless of shaping and positioning accuracy, while minimizing internal defects by concentrating pressure and fluidity around the insert, resulting in a stronger bond than traditional methods.

Implementation Method 1

semi-cooling the molten metal to a temperature (hereinafter referred to as a press-fitting temperature) which is higher than a recrystallization temperature of the second material

Methodology Applied

Scientific EffectRecrystallization:

Implementation Method 2

press-fitting the insert into the fitting hole of the cast product while pressing and extending the fitting hole with the taper in a thinning direction of the taper

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentUS11590559B2Method of manufacturing cast product and forged product with insert joined thereto

Publication Date: 2023.02.28 TOYOTA JIDOSHA KK

AI summary

An insert including a taper is covered with a molten metal. A metal molded product with the insert joined thereto is generated by semi-cooling the molten metal to a press-fitting temperature which is higher than a recrystallization temperature of the molten metal and lower than a melting point of the molten metal. A fitting hole which is filled with the insert is formed in the metal molded product. The taper is fitted into the fitting hole. An undercut is not formed in front of a tip of the taper. The insert is press-fitted into the fitting hole while pressing and extending the fitting hole with the taper in a thinning direction of the taper at a press-fitting temperature. The metal molded product is further cooled with the press-fitting maintained.