Weld Cladding Cryogenic Cooling Dilution Control
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Solution Overview
Problem
Weld cladding using stainless steel and high Nickel alloys often results in high iron content, which significantly reduces the pitting corrosion resistance, exceeding the industry's maximum allowed dilution level of 36%, leading to reduced corrosion resistance in harsh environments.
Innovation Solution
A method of weld cladding that involves simultaneously depositing weld metal on a substrate while applying cryogenic carbon dioxide coolant to the reverse side to minimize mixing and dilution, using a coolant head with nozzles positioned to impinge the coolant on the substrate ahead of and behind the welding torch, effectively managing heat input and reducing iron dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If weld cladding is performed using stainless steel and high Nickel alloys, then the corrosion resistance of the substrate is improved, but the iron content in the weld increases, reducing pitting corrosion resistance
Solution Approach 1:
The substrate surface is pre-cooled with cryogenic coolant before welding begins. This preliminary cooling action reduces the substrate temperature, which minimizes the mixing between weld metal and base metal, thereby controlling iron dilution to below 36% and maintaining pitting corrosion resistance while still achieving the desired corrosion resistance improvement
Solution Approach 2:
The invention changes the thermal parameter of the substrate by applying cryogenic cooling (temperature below -50°C). This parameter change affects the weld metal solidification rate and mixing characteristics, enabling control of iron content in the final weld cladding to maintain both corrosion resistance and pitting resistance
2Productivity
If high heat input is used during weld cladding, then the welding process is faster and more productive, but the mixing of weld metal with substrate metal increases, reducing corrosion resistance
Solution Approach 1:
The substrate is pre-cooled before welding to establish a thermal gradient that promotes rapid solidification of weld metal. This preliminary action allows higher welding speeds to be used without increasing dilution, as the cold substrate rapidly solidifies the weld metal before it can mix extensively with the base metal
Solution Approach 2:
Cooling is applied continuously throughout the welding process, not just before or after. This continuous cooling maintains the thermal gradient necessary for rapid solidification throughout the entire weld deposition, ensuring consistent low dilution levels even at high productivity rates
3Manufacturing precision
If the substrate is cooled during welding, then the dilution of weld metal is reduced, but the welding process may be disrupted
Solution Approach 1:
Cooling is applied locally to the substrate surface through targeted coolant delivery at the weld zone, rather than cooling the entire workpiece. This localized approach reduces dilution at the weld interface while minimizing thermal gradients in the bulk material that could cause distortion or welding process disruption
Solution Approach 2:
A coolant delivery system acts as an intermediary between the welding process and the substrate. The coolant system mediates the thermal interaction by controlling the rate and distribution of heat extraction, allowing dilution control without directly interfering with the welding arc or molten pool stability
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 significantly improves the corrosion resistance of weld cladding, extending the life of components in harsh environments, reducing deformation, and lowering manufacturing costs by maintaining low iron dilution levels, thus enhancing productivity in applications like nuclear and offshore industries.
Implementation Method 1
applying a coolant to the second surface of the substrate
Implementation Method 2
The expansion of the coolant may advantageously result in a change of state of the coolant from liquid to solid. Preferably, expansion through the nozzle transforms liquid carbon dioxide to solid snow carbon dioxide. Solid snow carbon dioxide advantageously has been found to provide the highest heat transfer characteristics due to the heat of sublimation
Data Source
AI summary
A method of weld cladding comprises: a) providing a welding torch (8) on a first side (4) of a substrate (2); b) providing a coolant head (1) on an opposing side (6) of a substrate (2); and c) simultaneously depositing a weld on the first side (4) while applying a cryogenic coolant (50) to the opposing side (6) of the substrate (2). The substrate (2) may be a pipe with the welding torch (8) disposed outside the pipe (2) and the coolant head (10) inside.