Back Purging for Convex Weld Root Control in Out-of-Position Welding

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Solution Overview

Problem

Existing welding systems face challenges in achieving consistent root pass welds, particularly in out-of-position welding, where gravity and ambient environment affect the shape and structure of the weld deposit, leading to undesirable concave root surfaces.

Innovation Solution

A back purging system is implemented, using a sealing portion to create a purge region with a shielding gas, such as argon or nitrogen, which displaces the ambient environment and controls the root surface of the weld deposit to form a convex root surface with positive penetration, even in vertical or overhead positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If welding is performed in out-of-position (vertical or overhead), then welding versatility is improved, but weld root surface quality deteriorates due to gravity and ambient environment causing concave root surfaces

Engineering Contradiction:

Improvewelding position capabilityVSAvoidroot surface quality

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent introduces a back purging system that supplies inert shielding gas (argon or nitrogen) to the back side of the workpiece, creating an inert atmosphere in the purge region. This prevents ambient air from contacting the weld deposit and affects surface tension to promote convex root surface formation, thereby maintaining root surface quality while enabling out-of-position welding

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The system performs preliminary action by establishing the inert gas environment in the purge region before the weld deposit is formed. The shielding gas is supplied ahead of time to displace ambient air and create favorable conditions for convex root surface formation, preventing harmful effects before they occur

Inventive Principle:

Principle #10Preliminary action

2Productivity

If welding speed and heat input are increased, then productivity is improved, but weld root surface quality deteriorates with greater formation of undesirable compounds and geometries

Engineering Contradiction:

Improvewelding speedVSAvoidroot surface quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The back purging system creates a controlled inert atmosphere that allows higher welding speeds and heat input without compromising root surface quality. The shielding gas prevents oxidation and controls surface tension, enabling faster welding while maintaining convex root surface geometry

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Manufacturing precision

If back purging system is implemented, then root surface quality is improved with convex root surface formation, but device complexity increases

Engineering Contradiction:

Improveroot surface qualityVSAvoidsystem complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The back purging system is implemented as a separate, modular subsystem with distinct components (sealing portion, gas supply, valving) that can be independently configured and controlled. This segmentation allows the complex function of creating convex root surfaces to be achieved through coordinated simple components

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inert shielding gas acts as an intermediary between the ambient environment and the weld deposit. It mediates the interaction by displacing harmful ambient air and controlling surface tension, thereby achieving improved root surface quality without requiring direct mechanical intervention

Inventive Principle:

Principle #24Intermediary (Mediator)

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 shielding gas effectively reduces the formation of less desirable compounds and geometries, ensuring a consistent convex root surface with improved weld quality and penetration, enabling faster welding speeds and higher heat input during root pass welding.

Implementation Method 1

The shielding gas displaces an ambient environment within the purge region

Methodology Applied

Scientific EffectGas displacement:

Implementation Method 2

the shielding gas is configured to control the back weld root surface of the weld deposit formed along the section of the joint to have a convex root surface with a positive root penetration

Methodology Applied

Scientific EffectGas pressure control:

Data Source

PatentUS11097367B2System and method for reducing weld root concavity

Publication Date: 2021.08.24 ILLINOIS TOOL WORKS INC

AI summary

A method of controlling a back weld root surface includes arranging a sealing portion along the back weld root surface of a workpiece to form a purge region adjacent to a section of a joint, supplying a shielding gas within the purge region at a first flow rate, and applying a weld deposit across a front surface of the section of the joint. The shielding gas displaces an ambient environment within the purge region, and the back weld root surface of the weld deposit includes a positive root penetration relative to the back weld root surface based at least in part on the shielding gas within the purge region.