Special Torch Flux-Cored Welding for Low-Hydrogen Steel Joints
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Solution Overview
Problem
The welding industry faces challenges with hydrogen embrittlement and hydrogen cracking in high tensile strength steel welding due to diffusible hydrogen, particularly with seamed flux cored wires that absorb moisture, leading to increased hydrogen content in weld metal, which is difficult to reduce effectively using existing methods.
Innovation Solution
A welding method utilizing a special torch with a suction nozzle and a seamed flux cored wire having a specific seam structure and composition, where the flux contains a slag forming agent with controlled metal oxide, fluoride, and carbonate ratios, and the torch design optimizes hydrogen removal by positioning the suction nozzle to effectively capture moisture during welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preheating and post-heating are performed to reduce diffusible hydrogen, then hydrogen embrittlement and cracking are prevented, but energy consumption and manufacturing cost increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-drying the flux material at high temperature (e.g., 1100°C to 1500°C) during manufacturing to remove hydrogen sources before the welding process. This preliminary treatment eliminates the need for energy-intensive preheating and post-heating operations during welding, as the flux is already depleted of moisture and hydrogen-containing compounds before use
Solution Approach 2:
The patent changes the chemical composition parameters of the flux by controlling the content of hydrogen-source materials (organic matters, carbonates, sulfates, chlorides) to specific ranges. By adjusting these compositional parameters and using high-temperature drying, the flux achieves low hydrogen emission characteristics without requiring additional energy input during the welding process
2Reliability
If fluoride is added to the flux to reduce diffusible hydrogen, then hydrogen cracking is prevented, but arc stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fluoride content in the flux within a specific range (0.1% to 5% by mass) and balancing it with other flux components. This optimized compositional parameter combination achieves hydrogen reduction while maintaining arc stability, resolving the contradiction between hydrogen prevention and arc stability
3Reliability
If CF4 is mixed into the shielding gas to reduce diffusible hydrogen, then hydrogen cracking is prevented, but arc stability deteriorates and safety issues arise
Solution Approach 1:
The patent extracts the hydrogen-reduction function from the shielding gas system and transfers it to the flux material itself. Instead of adding CF4 to the shielding gas, the flux is designed to inherently reduce hydrogen through controlled composition and pre-drying, eliminating the need for hazardous gas additives while maintaining arc stability
4Ease of manufacture
If seamed flux cored wire is used to reduce manufacturing cost, then production cost decreases, but moisture absorption increases leading to higher hydrogen content
Solution Approach 1:
The patent applies preliminary action by performing high-temperature drying of the flux during manufacturing to remove moisture and hydrogen sources before the wire is put into service. This preliminary treatment ensures that even seamed wires with potential moisture ingress points start with minimal hydrogen content, maintaining reliability while allowing cost-effective seamed construction
Solution Approach 2:
The patent changes the chemical composition parameters of the flux to reduce hydrogen-source materials and optimizes the drying temperature and duration parameters during manufacturing. These parameter adjustments ensure low initial hydrogen content in seamed wires, preventing moisture absorption from compromising weld 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 method significantly reduces the diffusible hydrogen content in weld metal, enabling efficient welding of high tensile strength steel and thick plates with improved weldability and reduced energy costs, while maintaining arc stability and preventing low temperature cracking.
Implementation Method 1
the special torch has a suction nozzle between a contact tip and a shield nozzle
Implementation Method 2
the hydrogen source 205 on a wire surface is vaporized and discharged from the welding wire 201
Implementation Method 3
the central portion 203 is heated by heat conduction from the heated steel outer casing 202, and the hydrogen source 205 in the flux is also vaporized and discharged
Implementation Method 4
welding current flows from the contact tip 208 to the welding wire 201, and the welding wire 201 melts by an arc 209 at the tip end of the welding wire 201
Implementation Method 5
since the welding current flows through a wire protruding portion 211 of the welding wire 201 protruded from the contact tip 208, so that resistance heating occurs and the temperature rises
Implementation Method 6
the central portion 203 is heated by heat conduction from the heated steel outer casing 202
Data Source
AI summary
Provided is a welding method using a special torch and a flux cored wire, in which the special torch has a suction nozzle between the contact tip and the shield nozzle, and the flux cored wire has a flux filled inside the steel outer casing, and a seam portion where both ends of a metal in a width direction of the steel outer casing are butted or overlapped in a longitudinal direction of the flux cored wire.