Gas Shield Welding Wire Composition for Hot Cracking Resistance
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Solution Overview
Problem
Welding wires for gas shield arc welding of high-Cr ferritic heat-resistant steel, such as Mod.9Cr-1Mo steel, face challenges with hot cracking, inadequate creep strength, and toughness, particularly due to high Cr content affecting solidification completion temperature and microstructure, while existing solutions do not adequately address these issues under real-world welding conditions.
Innovation Solution
A wire composition with controlled chemical components, including reduced Ni content, optimized Cr range, and balanced Mn and Ni levels to suppress hot cracking and enhance creep strength and toughness, ensuring sound weld zones and improved mechanical performance post-weld heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high Cr content (8.0-11.0%) is used to achieve high-temperature strength and corrosion resistance, then creep strength is improved, but hot cracking resistance deteriorates due to delayed solidification completion
Solution Approach 1:
The patent optimizes the Cr content range to 8.0-11.0% while simultaneously adjusting C (0.03-0.18%), Si (0.06-0.80%), Mn (0.85-2.00%), Mo (0.80-1.20%), and other alloying elements to achieve the right balance between creep strength and hot cracking resistance. This multi-parameter optimization resolves the contradiction by finding the optimal composition window.
Solution Approach 2:
The patent creates a complex multi-element alloy system combining Cr, Mo, Ni, Nb, V, and microalloying elements (Ti, B, Al) to achieve synergistic effects. The composite alloy composition provides both high-temperature strength through Cr-Mo-Nb-V carbides and improved hot cracking resistance through controlled solidification characteristics.
2Strength
If Ni and Mo content is increased to improve high-temperature strength, then creep resistance is enhanced, but hot cracking susceptibility increases
Solution Approach 1:
The patent specifies Mo content at 0.80-1.20% and Ni content at 0.03-1.00% with the constraint that (Mo + Ni) ≤ 2.10%. This parameter control balances the beneficial effect on creep strength while limiting the harmful effect on hot cracking resistance.
Solution Approach 2:
The patent introduces microalloying elements (Nb: 0.010-0.250%, V: 0.02-0.50%, Ti: ≤0.010%, B: ≤0.0010%) as intermediaries that form fine precipitates to strengthen the matrix, providing an alternative mechanism for high-temperature strength that reduces dependence on high Ni-Mo content.
3Strength
If Mn content is increased to improve toughness, then impact energy is enhanced, but hot cracking resistance deteriorates
Solution Approach 1:
The patent optimizes Mn content to 0.85-2.00% and introduces the interactive constraint (Mn + 2Ni - 10N) ≤ 3.00 to balance toughness improvement with hot cracking resistance. This parameter optimization resolves the contradiction by finding the optimal Mn level within the multi-element system.
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 proposed wire composition effectively prevents hot cracking during welding, achieves excellent creep strength and toughness after post-weld heat treatment, and produces sound weld zones, addressing the limitations of existing solutions by stabilizing carbonitrides and managing δ ferrite phase content.
Implementation Method 1
stabilizing carbonitrides and managing δ ferrite phase content
Implementation Method 2
managing δ ferrite phase content
Data Source
Figure 1
Figure 2A~2B
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AI summary
Provided is a wire for gas shield arc welding that produces sound weld zones without causing hot cracking during welding, while exhibiting excellent creep strength and toughness after PWHT. The wire for gas shield arc welding in the present invention contains C, Si, Mn, S, Cr, Mo, V, Nb, and N in respective predetermined contents, in which the content of each of Ni, P, Cu, Al, B, and O is restricted to a predetermined content, with the balance being Fe and inevitable impurities, a total of the Mn content and the Ni content is set at 0.60 to 1.15%, and a ratio of the Mn content to the S content is 87 or more.