Flux-Cored Wire for High-Strength Steel Welding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High strength steels with 780 MPa or more tensile strength pose challenges in welding due to increased susceptibility to weld cracking and reduced low-temperature toughness, requiring preheating that hinders construction efficiency and cost reduction.
Innovation Solution
A flux-cored wire composition optimized with CaF2, BaF2, SrF2, MgF2, and LiF, along with Ti, Si, and Mn, which reduces diffusible hydrogen and enhances low-temperature toughness, allowing for reduced or omitted preheating during welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preheating is applied to suppress weld cracking in high strength steel, then cold crack resistance is improved, but welding efficiency deteriorates and construction period cannot be shortened
Solution Approach 1:
The invention changes the chemical composition parameters of the flux-cored wire, specifically optimizing the content of V (0.01-0.08%), Ti (0.03-0.10%), and Al (0.015-0.060%), to alter the welding process characteristics. This enables the wire to produce low-hydrogen weld metal that resists cold cracking without requiring preheating, thus resolving the contradiction between crack resistance and welding efficiency
Solution Approach 2:
The flux-cored wire acts as an intermediary that introduces specific alloying elements (V, Ti, Al) into the weld zone. These elements serve as mediators that occlude hydrogen and refine the weld metal structure, providing cold crack resistance without the need for preheating, thereby maintaining high welding efficiency
2Strength
If higher strength steel is used to reduce material cost and weight, then construction cost is reduced, but weld cracking susceptibility increases
Solution Approach 1:
The flux-cored wire serves as an intermediary material that compensates for the increased cracking susceptibility of high strength steel. By introducing V, Ti, and Al into the weld metal, the wire creates a protective effect that occludes hydrogen and refines the microstructure, enabling reliable welding of 780 MPa-class steel without preheating
Solution Approach 2:
The invention creates a composite welding system combining the high strength steel base metal with a specially formulated flux-cored wire containing multiple alloying elements. This composite approach allows the weld metal to have properties that compensate for the base metal's cracking susceptibility, achieving both high strength and low cracking tendency
3Strength
If fluoride is added to flux to improve low-temperature toughness, then toughness is improved, but the effect on cold crack resistance is insufficient
Solution Approach 1:
The invention creates a composite flux composition that combines fluoride (for toughness) with V, Ti, and Al (for hydrogen occlusion and microstructure refinement). This composite approach achieves both low-temperature toughness and cold crack resistance, overcoming the limitation of fluoride alone
Solution Approach 2:
The invention merges multiple functional elements (fluoride for toughness, V for hydrogen occlusion, Ti for microstructure refinement, Al for deoxidation) into a single flux-cored wire system. This combination achieves synergistic effects that simultaneously improve both toughness and cold crack resistance
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 flux-cored wire achieves high strength and toughness welds with reduced hydrogen levels, enabling efficient welding of high strength steels without preheating, thus enhancing construction efficiency and cost-effectiveness.
Implementation Method 1
the fluoride rises basicity of molten pool to reduce an amount of oxygen in the weld metal, and thus, high low-temperature toughness can be obtained
Implementation Method 2
an amount of V is further optimized and diffusible hydrogen is occluded in V to improve cold crack resistance
Data Source
AI summary
In a flux-cored wire according to the present invention, CaF2 and the like are included and a total amount thereof α is 3.3 to 6.0% in terms of mass % with respect to a total mass, Ti oxide and the like are included and a total amount thereof β is 0.4 to 1.2% in terms of mass % with respect to the total mass, CaCO3 and the like are included and a total amount thereof is 0.1 to 0.5% in terms of mass % with respect to the total mass, and an amount of an iron powder in the flux is less than 10% in terms of mass % with respect to the total mass.