ERW Stainless Clad Pipe Welding for Fracture and Corrosion Resistance
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Solution Overview
Problem
Conventional methods for producing electric-resistance-welded stainless clad steel pipes or tubes face challenges in achieving excellent fracture properties and corrosion resistance without additional welding treatments, as they often require weld overlaying, which decreases productivity and increases production costs, and can coarsen crystal grains in the heat-affected zone, reducing fracture properties and corrosion resistance.
Innovation Solution
The method involves using a shielding-gas blowing nozzle with a specific structure to reduce oxygen concentration around the weld area during electric resistance welding, controlling the gas release conditions, and performing heat treatment within a predetermined temperature and cooling rate range to prevent exposure of the base metal at the inner surface and enhance both fracture properties and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the amount of upset is increased to discharge oxidized melts during welding, then the mechanical properties of the weld are improved, but the base metal enters the welded seam part of cladding metal and exposes at the inner surface, impairing corrosion resistance
Solution Approach 1:
The patent applies inert gas shielding (argon or nitrogen) during electric resistance welding to prevent oxidation of the weld zone. By creating an inert atmosphere, oxidized melts (penetrators) are prevented from forming in the first place, eliminating the need for excessive upset to discharge them. This allows the cladding metal to remain intact at the inner surface, maintaining corrosion resistance while still achieving sound welds.
Solution Approach 2:
The patent optimizes welding parameters including current density, welding speed, and upset amount to achieve complete fusion and discharge of oxidized melts without excessive base metal intrusion. By precisely controlling these parameters, the weld quality is improved while preventing base metal exposure that would compromise corrosion resistance.
2Strength
If additional welding treatments such as weld overlaying are performed to improve weld properties, then the mechanical properties are enhanced, but productivity decreases and production costs increase
Solution Approach 1:
The patent removes the need for additional weld overlaying treatments by implementing inert gas shielding during the primary electric resistance welding process. This prevents oxidized melts from forming in the first place, so no subsequent removal or overlaying operations are required. The weld achieves excellent mechanical properties directly from the initial welding process, eliminating extra production steps.
Solution Approach 2:
The patent performs oxidation prevention through inert gas shielding during the initial welding process itself, rather than addressing oxidation problems in subsequent post-weld treatments. This preliminary protective action prevents the formation of penetrators that would otherwise require additional overlaying operations to correct.
3Strength
If additional welding treatments such as weld overlaying are performed to improve weld properties, then the mechanical properties are enhanced, but the crystal grains in the heat-affected zone coarsen, reducing fracture properties and corrosion resistance
Solution Approach 1:
The patent converts the potential harm of oxidation during welding into a benefit by using inert gas shielding to prevent oxidized melts from forming. This eliminates the need for weld overlaying operations that would otherwise be required to remove penetrators and apply new cladding metal. By preventing the problem rather than correcting it, the heat-affected zone microstructure remains fine-grained with excellent mechanical and corrosion properties.
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 or tubes with excellent fracture properties and corrosion resistance without additional welding treatments, maintaining the integrity of the cladding metal's properties and reducing production costs.
Implementation Method 1
by using a shielding box to cover a pipe or tube passage region from a butted part heating starting point to a welding point, blowing shielding gas over the parts to be welded
Implementation Method 2
butt pressing and welding the transverse ends of the steel strip heated and molten by high-frequency current
Implementation Method 3
a measure is typically employed to increase the amount of upset by the squeeze rolls so that oxidized melts formed during the welding are discharged to outside the pipe or tube
Implementation Method 4
performing heat treatment within a predetermined temperature and cooling rate range to prevent exposure of the base metal at the inner surface and enhance both fracture properties and corrosion resistance
Implementation Method 5
performing heat treatment within a predetermined temperature and cooling rate range to prevent exposure of the base metal at the inner surface
Data Source
Figure 1
Figure 2A~2C
Figure 3A~4C
AI summary
An electric-resistance-welded stainless clad steel pipe or tube that is excellent in both the fracture property of the weld and the corrosion resistance of the pipe or tube inner surface as electric resistance welded without additional welding treatment such as weld overlaying after electric resistance welding is provided. An electric-resistance-welded stainless clad steel pipe or tube comprises: an outer layer of carbon steel or low-alloy steel; and an inner layer of austenitic stainless steel having a predetermined chemical composition, wherein a flatness value h/D in a 90° flattening test in accordance with JIS G 3445 is less than 0.3, and a pipe or tube inner surface has no crack in a sulfuric acid-copper sulfate corrosion test in accordance with ASTM A262-13, Practice E, where h is a flattening crack height (mm), and D is a pipe or tube outer diameter (mm).