Fork-Hanger Friction Welding With Post-Tempering

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Solution Overview

Problem

Existing methods for connecting forks to hangers on material handling vehicles require long times to achieve structurally strong joints, and friction welding processes result in excessive joint hardness and brittleness, making them unsuitable for mounting hangers to forks.

Innovation Solution

Implementing a Low Force Linear Friction Welding process followed by a post-weld tempering process to control the cooling rate and hardness of the weld joint, allowing the martensite to fully form and then tempering it to achieve a suitable microstructure for improved toughness and reduced hardness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional welding methods are used to connect forks to hangers, then structurally strong joints are achieved, but the welding time is relatively long

Engineering Contradiction:

Improvejoint strengthVSAvoidwelding time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent applies Low Force Linear Friction Welding which changes the welding parameters (force, speed, time) to achieve a different welding mechanism that is both faster and produces acceptable joint strength. The friction welding process generates heat through mechanical friction rather than conventional arc welding, enabling shorter cycle times while maintaining joint integrity

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If friction welding process is used to reduce welding time, then welding time is significantly reduced, but the joint hardness becomes excessive and the joint becomes brittle

Engineering Contradiction:

Improvewelding timeVSAvoidjoint toughness

Core Design Contradiction:

Loss of timeVSStrength

Solution Approach 1:

The patent performs preliminary action by controlling the cooling rate during the friction welding process to allow martensite to fully form, then applies a post-weld tempering process to reduce the excessive hardness and brittleness. This two-stage approach (controlled cooling followed by tempering) resolves the brittleness issue while maintaining the speed advantage of friction welding

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the thermal parameters by implementing a controlled cooling rate and subsequent tempering heat treatment. This transforms the microstructure from overly hard and brittle martensite to a tempered martensite structure that retains strength while improving toughness and ductility

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces the welding time while achieving a tempered martensite microstructure that enhances the joint's toughness and mechanical performance, allowing for secure attachment of hangers to forks in a fraction of the original time.

Implementation Method 1

Implementing a Low Force Linear Friction Welding process

Methodology Applied

Scientific EffectFriction welding: Friction Welding

Implementation Method 2

followed by a post-weld tempering process to control the cooling rate and hardness of the weld joint

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS20210156002A1Connection between forks and hangers on forks

Publication Date: 2021.05.27 CASCADE CORPORATION

AI summary

A method for welding at least one hanger to a fork. A friction welding process may be used to create a weld between the hanger and the fork, after which the heat-affected zone (HAZ) may be allowed to cool. Preferably the cooling occurs until martensite is formed, after which a post-tempering current is applied to the HAZ.