Laser Hot Wire Welding for Corrosion-Clad Multi-Layer Joints
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Solution Overview
Problem
Welding multi-layered metal structures, such as tubes and pipes, poses challenges due to the need for balancing mechanical and chemical performance, particularly in harsh environments like offshore oil and gas transport, where traditional arc-based techniques result in compromised performance, high costs, and require highly controlled procedures.
Innovation Solution
A method involving laser hot wire welding, where a pair of multi-layered workpieces with a corrosion-resistant cladding layer and a ferrous alloy base layer are joined using a root pass weld bead with a corrosion-resistant filler wire, followed by additional weld beads using a ferrous alloy filler wire, controlling the concentration of corrosion-resistant elements to less than 50% in the subsequent weld beads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional arc-based welding techniques are used to weld multi-layered structures, then the welding process is well-established and equipment is readily available, but the weld joint performance is compromised and corrosion resistance is reduced
Solution Approach 1:
The welding process is segmented into multiple passes with different filler materials. The root pass uses corrosion-resistant alloy filler wire to join the corrosion-resistant layers, while subsequent passes use carbon steel filler wire to join the base layers. This segmentation allows each pass to be optimized for its specific function, achieving both corrosion resistance and structural integrity.
Solution Approach 2:
Different regions of the weld joint are given different material compositions tailored to their specific requirements. The root pass region receives high corrosion-resistant element concentration (at least 50% Cr equivalent) for maximum corrosion protection, while the cap and root passes are optimized for mechanical strength. This local differentiation resolves the contradiction by providing corrosion resistance where needed without compromising overall weld performance.
2Reliability
If corrosion-resistant alloy filler wire is used throughout the entire weld joint, then corrosion resistance is maximized, but the cost increases significantly
Solution Approach 1:
Corrosion-resistant alloy filler wire is used selectively only in the root pass where it is most needed for corrosion protection, while carbon steel filler wire is used in the cap and root passes. This localized application reduces the quantity of expensive corrosion-resistant material required while maintaining adequate corrosion resistance at the critical root region.
Solution Approach 2:
The chemical composition parameters of the filler wire are changed between passes. The root pass uses filler wire with at least 50% Cr equivalent and specific alloying elements, while subsequent passes use carbon steel filler wire with different composition. This parameter change optimizes both cost and performance by matching material properties to functional requirements.
3Reliability
If high concentration of corrosion-resistant elements is maintained in all weld beads, then corrosion resistance is improved, but the mechanical properties and ductility deteriorate
Solution Approach 1:
High concentration of corrosion-resistant elements (at least 50% Cr equivalent) is concentrated in the root pass weld bead where corrosion protection is most critical. The cap and root passes use carbon steel filler wire with lower alloy content, providing adequate mechanical strength and ductility. This local quality differentiation resolves the contradiction by providing high corrosion resistance where needed without compromising overall mechanical properties.
Solution Approach 2:
The weld joint is segmented into multiple passes with different material compositions. The root pass is segmented to have high corrosion-resistant element content for maximum protection, while subsequent passes are segmented to provide structural strength. This segmentation allows optimization of both corrosion resistance and mechanical properties in different regions of the weld joint.
4Reliability
If multiple passes with different filler wires are used, then both corrosion resistance and mechanical properties are optimized, but the welding procedure complexity increases
Solution Approach 1:
The welding procedure is segmented into distinct passes with specific requirements: root pass using corrosion-resistant alloy filler wire, and cap and root passes using carbon steel filler wire. Each pass has defined parameters for filler wire composition, wire diameter, and welding conditions. This structured segmentation makes the complex multi-pass procedure manageable and repeatable.
Solution Approach 2:
Specific parameter ranges are defined for each pass to guide the welding process. The root pass requires filler wire with at least 50% Cr equivalent and specific alloying elements, while subsequent passes use carbon steel filler wire with defined composition ranges. Wire diameters, welding speeds, and heat input parameters are specified for each pass, reducing procedure complexity through clear parameter specifications.
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 enhances the mechanical and corrosion-resistant properties of the weld joint, reducing costs and complexity while minimizing intermixing of chemical elements, thereby improving the reliability and performance of the weldment.
Implementation Method 1
forming one or more weld beads to join base layers over the root pass weld bead to join the base layers of the workpieces by resistively heating a second filler wire while directing a laser beam over the root pass weld bead
Implementation Method 2
forming a root pass weld bead to join the corrosion resistant layers of the workpieces using a first filler wire comprising the corrosion resistant element
Data Source
AI summary
The disclosed technology generally relates to welding, and more particularly to welding multi-layered structures. In an aspect, a method of welding multi-layered metallic workpieces comprises providing a pair of multi-layered workpieces. Each of the workpieces has a base layer and an cladding layer, where the cladding layer comprises a corrosion resistant element adapted to suppress corrosion in a ferrous alloy. The method additionally comprises forming a root pass weld bead to join cladding layers of the workpieces using a first filler wire comprising the corrosion resistant element and focusing a first laser beam on the cladding layers. The method additionally comprises forming one or more weld beads to join base layers of the workpieces by resistively heating a second filler wire and directing a second laser beam over the root pass weld bead. The method is such that a concentration of the corrosion-resistant element in the one or more weld beads is less than 50% of a concentration of the corrosion-resistant element in the root pass weld bead.