Dissimilar-Metal Weld Joint Buttering for Galling Resistance
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Solution Overview
Problem
Threaded joints between dissimilar metals, such as stainless steel and high-strength low alloy steel, are prone to galling and stress failures in industrial applications like oil and gas drilling, leading to frequent repairs.
Innovation Solution
A method of welding that involves buttering a joint surface on one member by preheating, welding a border layer of weld material, and heat treating, followed by forming a weld between the members with preheating and maintaining an interpass temperature of 177 degrees C. or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If threaded joints are used to connect dissimilar metals (stainless steel and high-strength low alloy steel), then the members can be easily assembled and disassembled, but the joints are prone to galling and stress failures
Solution Approach 1:
The joint is divided into multiple functional zones: a buttering layer applied to the first member, a weld layer connecting the members, and a heat-affected zone. This segmentation allows each zone to be optimized for its specific function - the buttering layer prevents galling, the weld layer provides strong connection, and the heat treatment optimizes the microstructure
Solution Approach 2:
A buttering layer of weld material is applied as an intermediary between the dissimilar metals. This intermediate layer acts as a transition zone that reduces direct contact between incompatible metal surfaces, preventing galling while allowing the final weld to create a strong bond between the stainless steel and high-strength low alloy steel members
2Strength
If welding is performed to join dissimilar metals, then joint strength is improved, but the complex multi-step process increases manufacturing complexity
Solution Approach 1:
The buttering layer is applied in advance before the final welding operation. This preliminary action prepares the joint surfaces with a protective and compatible layer, ensuring that when the final weld is applied, the dissimilar metals are properly prepared for bonding, reducing galling risk and improving weld quality
Solution Approach 2:
The welding process utilizes controlled parameter changes including preheating to specific temperatures, maintaining interpass temperatures between 177°C or less, and applying heat treatment at controlled temperatures. These parameter controls optimize the microstructure and mechanical properties of the weld and heat-affected zone while managing the complexity through standardized procedures
3Ease of manufacture
If standard welding procedures are used on dissimilar metals, then the process is simple, but the joints are susceptible to galling and stress failures
Solution Approach 1:
The buttering layer is applied in advance before the final welding operation. This preliminary action prepares the joint surfaces with a protective and compatible layer, ensuring that when the final weld is applied, the dissimilar metals are properly prepared for bonding, reducing galling risk and improving weld quality
Solution Approach 2:
The welding process utilizes controlled parameter changes including preheating to specific temperatures, maintaining interpass temperatures between 177°C or less, and applying heat treatment at controlled temperatures. These parameter controls optimize the microstructure and mechanical properties of the weld and heat-affected zone while managing the complexity through standardized procedures
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 method enhances the resistance of welded joints to galling and stress failures, improving the durability and reducing the frequency of repairs in industrial applications.
Implementation Method 1
preheating the first joint surface; preheating the border layer and preheating a second joint surface on the second member; preheating the first and second members to 75+/−5 degrees F.
Implementation Method 2
welding a border layer of weld material to the first joint surface; forming a weld between the first and second members
Implementation Method 3
heat treating the border layer and the first joint surface after welding the border layer
Implementation Method 4
maintaining an interpass temperature of 177 degrees C. or less while welding the plurality of passes
Data Source
AI summary
A welded joint includes a high-strength low alloy steel first member, a stainless steel second member, and a weld formed between the first and second members, the weld further including a border layer of weld material welded to the first member, the border layer comprising gamma and sigma microstructures and a body of weld material disposed between the border layer and the second member. The first and second members may be tubular. The body of weld material may be annular. A heat-affected zone of the first member may lack untempered martensite microstructures. The stainless steel may be a precipitation-hardened (PH) stainless steel, and the weld material of the border layer and the weld material of the body may both include a super duplex stainless steel.