Tungsten Electrode Anode Current Capacity

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Solution Overview

Problem

Tungsten inert gas welding and plasma welding face limitations with tungsten electrodes used as anodes, particularly in high-current applications, due to low current-carrying capacity, risk of electrode destruction, and contamination of weld seams, especially when working with materials like aluminum and titanium, which form high-melting oxides.

Innovation Solution

The method involves influencing the energy density and arc attachment on the electrode's arc-side surface by using a material with different physical properties for the selected area and supplying a focusing gas flow to prevent electrode destruction and enhance current-carrying capacity, allowing for higher welding currents and effective cleaning of the workpiece.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the tungsten electrode is used as the anode to achieve cleaning effect and dissolve oxide layers, then the cleaning effect is improved, but the current-carrying capacity of the electrode is severely limited

Engineering Contradiction:
Improvecleaning effectVSAvoidcurrent-carrying capacity
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating a dual-material electrode structure where only a selected area (the insert) has high melting point properties, while the rest of the electrode body uses materials with better electrical and thermal conductivity. This allows the electrode to carry higher currents without requiring the entire structure to have extreme heat resistance.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining a tungsten insert (high melting point) with a copper or copper-alloy body (high electrical and thermal conductivity). This composite structure resolves the contradiction by allowing the tungsten portion to withstand arc heating and provide cleaning effect, while the copper body handles the current-carrying capacity efficiently.

Inventive Principle:
Principle #40Composite materials

2Productivity

If higher welding currents are applied to increase energy input, then the welding speed and productivity are improved, but the risk of electrode destruction and weld contamination increases

Engineering Contradiction:
Improvewelding speedVSAvoidelectrode stability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The composite electrode structure enables higher currents by distributing thermal and electrical loads appropriately. The copper body handles high current with low resistance, while the tungsten insert withstands the arc's thermal load, allowing higher welding currents without electrode destruction.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The tungsten insert acts as an intermediary between the arc and the copper body, absorbing the thermal stress and preventing direct heat transfer to the copper, which would otherwise melt at lower temperatures. This mediator role allows sustained high-current operation.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Stability of the object's composition

If the entire electrode surface is used for arc attachment, then the current distribution is improved, but the energy density becomes too high causing localized melting

Engineering Contradiction:
Improvecurrent distributionVSAvoidenergy density
Core Design Contradiction:
Stability of the object's compositionVSTemperature

Solution Approach 1:

The patent applies local quality by restricting the arc attachment to a specific insert area rather than the entire electrode surface. This creates a controlled zone of high energy density that prevents widespread heating while maintaining stable current distribution through the structured insert geometry.

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 significantly increases the current-carrying capacity of the electrode, prevents electrode destruction, and achieves efficient oxide layer dissolution, enabling high-energy input and stable welds, even in challenging materials like aluminum and titanium, with reduced risk of contamination and improved welding speed.

Implementation Method 1

The supplied shielding gas is heated by the arc or other thermal effects

Methodology Applied
Scientific EffectThermal heating: Heating

Implementation Method 2

The electrode is cooled, in particular by means of a water cooling system

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

supplying a focusing gas flow to prevent electrode destruction and enhance current-carrying capacity

Methodology Applied
Scientific EffectConvection cooling: Convection

Implementation Method 4

The arc thus generates a plasma... This cleaning effect prevents oxide inclusions in the weld

Methodology Applied
Scientific EffectPlasma: Plasma

Implementation Method 5

these high-melting-point oxides are not dissolved... electrons exiting the workpiece, or a corresponding ion bombardment, can dissolve any oxide layer

Methodology Applied
Scientific EffectOxide dissolution: Ablation

Implementation Method 6

An electric arc burns between the tungsten electrode and the workpiece. The workpiece is at least partially melted, forming the weld pool

Methodology Applied
Scientific EffectArc heating: Electric Arc

Implementation Method 7

The arc thus generates a plasma... the larger torch size makes it more difficult to access and handle

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP3169473B1Method for tungsten shielded welding
Publication Date: 2019.08.28 LINDE AG
  • EP3169473B1 patent drawingFigure 1
  • EP3169473B1 patent drawingFigure 2

AI summary

The invention relates to a method for tungsten shielded welding, in particular tungsten inert-gas shielded welding, or for plasma welding, in which method an electrode (200) and a workpiece (151) are supplied with a welding current, the electrode (200) being supplied as the anode and the workpiece (151) as the cathode. An electric arc (120) is initiated and burns between an electric-arc-side face (202) of the electrode (200) and the workpiece (151) and the energy density of the electric-arc-side face (202) of the electrode (200) and/or the build up of the electric arc (120) on the electric-arc-side face (202) of the electrode (200) are deliberately influenced.