Composition-Gradient Transition Piece for Dissimilar Metal Welding

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Solution Overview

Problem

Dissimilar metal welding in nuclear and thermal power plants faces challenges such as compound phase formation leading to corrosion and cracking, making frequent inspections and repairs necessary, and the use of transition pieces complicates the welding process due to restrictions on shape, size, and installation environments.

Innovation Solution

The method employs laser additive manufacturing to create a transition piece with an intermediate layer whose composition gradually changes between the two ends, allowing for easy adjustment of length, shape, and composition, thereby stabilizing penetration and metal composition during welding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dissimilar metal welding is performed at low current and low speed to reduce dilution, then cracking and corrosion resistance is improved, but welding productivity decreases

Engineering Contradiction:

Improvecracking and corrosion resistanceVSAvoidwelding speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

A transition piece with intermediate layers is introduced between the dissimilar metals (e.g., carbon steel and alloy steel). The transition piece has a base material layer matching one metal, intermediate layers with gradual composition changes, and a surface layer matching the other metal. This intermediary structure reduces direct contact between dissimilar metals, minimizing harmful compound phase formation and dilution effects while allowing for more efficient welding parameters.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The transition piece employs controlled composition gradients in its intermediate layers, where the alloying element concentrations change progressively from the base material side to the surface layer side. This parameter change in composition distribution allows for optimized welding characteristics at each layer, enabling higher welding speeds without excessive dilution or harmful phase formation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a transition piece with multiple composition layers is used to prevent cracking and corrosion, then welding quality is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvewelding qualityVSAvoidtransition piece structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The transition piece is designed to perform multiple functions within a single component: it provides compositional transition to prevent cracking and corrosion, serves as a mechanical connector between dissimilar metals, and offers a uniform structure that simplifies welding procedures. The intermediate layers with gradual composition changes achieve protective functionality while maintaining structural integrity and welding compatibility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If traditional transition pieces are used, then dissimilar metal welding is possible, but ease of manufacture is reduced due to restrictions on shape, size, and installation environment

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidinstallation environment adaptability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The transition piece utilizes controlled composition gradients in its intermediate layers, where alloying element concentrations change progressively from the base material side to the surface layer side. This parameter change enables continuous transition of material properties, allowing the component to be manufactured in various shapes and sizes while maintaining protective functionality against cracking and corrosion.

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 simplifies dissimilar metal welding by allowing for flexible transition piece design, reducing the likelihood of cracking and corrosion, and enabling welding in constrained environments without the need for frequent inspections.

Implementation Method 1

irradiating a laser beam while metal powder is being supplied to melt and solidify the metal powder, thereby forming an intermediate layer

Methodology Applied

Scientific EffectLaser heating and melting: Laser

Data Source

PatentUS11684976B2Method of manufacturing transition piece and transition piece

Publication Date: 2023.06.27 HITACHI GE NUCLEAR ENERGY LTD

AI summary

The invention provides a method of manufacturing a transition piece that has a high degree of freedom in adjustment of a length, a shape, or the like, can carry out a dissimilar metal welding easily, and is easy to perform, and a transition piece. The transition piece includes one end having the same composition as one material to be welded, another end having the same composition as another material to be welded, and an intermediate layer formed between the one end and the other end. The composition of the one end and the composition of the other end become the same as approaching a center. In the method of manufacturing the transition piece according to the invention, at least the intermediate layer among the one end, the other end, and the intermediate layer is formed by a additive manufacturing method.