Submerged Arc Weld Metal Composition for High-Heat-Input Toughness
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Solution Overview
Problem
Submerged arc welding with high heat input (300 kJ/cm or more) on high-strength steel (780 MPa class) results in insufficient weld metal strength and toughness, and is prone to hot cracking, using existing materials and methods.
Innovation Solution
A submerged arc welded joint with a specific chemical composition in the weld metal, including C: 0.05-0.15%, Si: 0.2-0.9%, Mn: 0.5-1.3%, P: 0.015% or less, S: 0.015% or less, Cr: 0.10-0.45%, Mo: 0.5-2.0%, Ni: 2.5-6.0%, and controlled Ceq and α values, to achieve yield strength of 630 MPa or higher and absorbed energy of 47 J or more in Charpy impact tests at 0°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If submerged arc welding is performed with high heat input (300 kJ/cm or more) on high-strength steel, then operation efficiency is improved, but weld metal strength becomes insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the weld metal (C: 0.05-0.15%, Si: 0.20-0.90%, Mn: 0.50-1.30%, Cr: 0.10-0.45%, Mo: 0.50-2.00%, Ni: 2.50-6.00%) and calculating equivalent carbon content (Ceq) and parameter α to achieve the optimal balance between high heat input welding efficiency and weld metal strength. This compositional parameter control enables the weld metal to maintain sufficient strength even under high heat input conditions.
2Productivity
If submerged arc welding is performed with high heat input (300 kJ/cm or more) on high-strength steel, then operation efficiency is improved, but weld metal toughness becomes insufficient
Solution Approach 1:
The patent uses parameter changes by controlling specific alloying element contents (particularly Ni: 2.50-6.00%, Cr: 0.10-0.45%, Mo: 0.50-2.00%) and adjusting the relationships between these elements to achieve both high heat input welding efficiency and adequate weld metal toughness. The controlled composition ensures the weld metal achieves V-notch Charpy impact energy of 47 J or more at 0°C even with high heat input welding.
3Productivity
If submerged arc welding is performed with high heat input (300 kJ/cm or more) on high-strength steel, then operation efficiency is improved, but hot cracking occurs
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition (C: 0.05-0.15%, Si: 0.20-0.90%, Mn: 0.50-1.30%, Cr: 0.10-0.45%, Mo: 0.50-2.00%, Ni: 2.50-6.00%) and calculating the parameter α = 30[C] + 0.7[Mn] + [Ni] - ([Si] + 0.5[Cr] + 1.5[Mo]) to be within a specific range, which prevents hot cracking while maintaining high heat input welding efficiency. This compositional control optimizes the solidification characteristics and reduces cracking susceptibility.
4Productivity
If existing welding materials are used with high heat input (300 kJ/cm or more), then operation efficiency is improved, but weld quality becomes insufficient
Solution Approach 1:
The patent applies parameter changes by comprehensively controlling the chemical composition parameters (C, Si, Mn, P, S, Cr, Mo, Ni) and adjusting the relationships between these elements to achieve optimal weld quality under high heat input conditions. The controlled composition ensures yield strength of 630 MPa or more and tensile strength of 780 MPa or more, meeting high-quality requirements while maintaining high productivity.
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 solution ensures high strength and toughness of the weld metal, preventing hot cracking and achieving desired mechanical properties even at elevated heat inputs, enhancing the quality of welded joints in high-strength steel applications.
Implementation Method 1
performing submerged arc welding with a welding heat input of 300 kJ/cm or more
Implementation Method 2
welding heat input applied in any one of Patent Literature 1 to Patent Literature 4 is 50 kJ/cm or less
Implementation Method 3
the weld metal has a chemical composition containing, by mass %, C: 0.05% to 0.15%, Si: 0.2% to 0.9%, Mn: 0.5% to 1.3%, Cr: 0.10% to 0.45%, Mo: 0.5% to 2.0%, Ni: 2.5% to 6.0%
Data Source
AI summary
A submerged arc welded joint having a weld metal formed by performing submerged arc welding with a heat input of 300 kJ/cm or more. The joint has a weld metal having a specified chemical composition, specified yield strength, and specified tensile strength. The weld metal has a specified absorbed energy vE0, as measured by a V-notch Charpy impact test performed at a testing temperature of 0° C. Ceq is in a range of 0.65 to 1.00, and a is 6.0 or less, as expressed by the equations below.Ceq=[C]+0.17[Mn]+0.04[Si]+0.025[Ni]+0.2[Cr]+0.25[Mo] (1)α=30[C]+0.7[Mn]+[Ni]−([Si]+0.5[Cr]+1.5[Mo]) (2)Here, in the equation (1) and the equation (2), the expression “[element symbol]” denotes a content (mass %) of the corresponding element in the weld metal described above.