Stainless Clad Steel Pipe Welding Without Post-Weld Repair
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Solution Overview
Problem
Existing methods for manufacturing electric-resistance-welded stainless clad steel pipes require additional welding processes, leading to decreased productivity, increased production costs, and environmental impacts, while also compromising the corrosion resistance of the weld seam due to penetration of low-alloy steel into the stainless steel cladding.
Innovation Solution
A method involving the controlled use of a shielding gas with optimized nozzle configuration and flow rates to reduce oxygen concentration around the weld area, preventing the penetration of low-alloy steel into the stainless steel seam without additional welding processes, thereby maintaining excellent weld characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of upset due to squeeze rolls is set to be larger than the thickness (t) to remove penetrators, then weld defects are reduced, but low-alloy steel penetrates into the stainless steel cladding, deteriorating corrosion resistance
Solution Approach 1:
The patent introduces a shielding gas (inert or reducing atmosphere) into the welding region to prevent oxide formation and control the chemical environment during welding. This allows for adequate upset amount to remove penetrators without compromising the stainless steel cladding's corrosion resistance, as the inert atmosphere prevents harmful chemical reactions at the weld zone.
Solution Approach 2:
The patent optimizes the amount of upset to be equal to or less than the thickness (t) of the cladding material, combined with controlling the shielding gas flow rate and composition. This parameter change resolves the contradiction by achieving adequate penetrator removal while preventing excessive steel penetration that would damage corrosion resistance.
2Reliability
If additional welding processes are used to restore cladding material after penetrator removal, then weld characteristics are improved, but productivity decreases and production costs increase
Solution Approach 1:
The patent applies shielding gas protection during the electric resistance welding process itself, preventing penetrator formation and cladding material loss in advance. This preliminary protective action eliminates the need for subsequent corrective welding operations, thereby maintaining high productivity while ensuring excellent weld characteristics.
Solution Approach 2:
The shielding gas acts as an intermediary substance that prevents harmful oxide formation and metal penetration during welding. By introducing this intermediary protective atmosphere, the patent achieves high-quality welds without requiring additional corrective welding processes, thus maintaining production efficiency.
3Reliability
If shielding gas is used to prevent oxide formation, then weld quality is improved, but device complexity increases
Solution Approach 1:
The shielding gas system serves multiple functions: it prevents oxide formation, controls the chemical environment, and protects the stainless steel cladding from contamination. This multi-functionality justifies the added device complexity by delivering comprehensive protection and significantly improved weld quality through a single integrated approach.
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 enables the production of electric-resistance-welded stainless clad steel pipes with excellent fracture characteristics and corrosion resistance without additional welding, improving productivity and reducing environmental impact.
Implementation Method 1
a shielding gas is blown over portions to be welded of an open pipe from directly above the portions to be welded in the region extending from the heating starting point to the welding point
Implementation Method 2
the opposing edges in the width direction of the steel strip are heated and melted by a high-frequency current
Data Source
Figure 1(a)~1(c)
Figure 2(a)~3(c)
Figure 4~5
AI summary
Provided are an electric-resistance-welded stainless clad steel pipe which has excellent weld characteristics, even without performing an additional welding process that is required in existing techniques after electric resistance welding, and a method of manufacturing the same. An electric-resistance-welded stainless clad steel pipe is manufactured by forming a hot-rolled steel strip of clad steel including low-carbon low-alloy steel and stainless steel into a cylindrical shape, and electric-resistance-welding the edges of the hot-rolled steel strip, characterized in that the flattening characteristic of an electric resistance weld, as-welded, satisfies the following formula: h/D<0.3 where h is the flattened height at fracture (mm) and D is the outer diameter of the pipe (mm).