Austenitic Alloy Thermomechanical Processing
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Solution Overview
Problem
Conventional alloys used in chemical processing and oil and gas industries suffer from limitations such as inadequate corrosion resistance and mechanical properties, leading to reduced service life and increased costs due to issues like stress corrosion cracking and intermetallic precipitate formation.
Innovation Solution
A method of thermomechanically processing austenitic alloys by forging and controlled cooling within specific temperature ranges to inhibit the precipitation of intermetallic compounds, using equations to calculate the sigma solvus temperature, cooling temperature, and critical cooling time based on the alloy composition, thereby preventing deleterious intermetallic precipitates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength non-magnetic stainless steels are used to improve mechanical properties, then yield strength and tensile strength are improved, but intermetallic precipitates form that decrease corrosion resistance
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate from austenite transformation temperature through the sigma phase formation temperature range to below it within a critical time period. This temporal parameter control prevents intermetallic precipitate formation while maintaining high strength properties, resolving the contradiction between strength and corrosion resistance
Solution Approach 2:
The patent employs preliminary action by performing thermomechanical processing (forging, rolling, or extrusion) at temperatures above the sigma solvus temperature before cooling. This preliminary high-temperature processing establishes a microstructure that, when followed by controlled cooling, prevents intermetallic formation while achieving desired mechanical properties
2Ease of manufacture
If conventional alloys are used in chemical processing facilities, then initial manufacturing cost is reduced, but service life is reduced due to corrosion and erosion
Solution Approach 1:
The patent changes the thermal processing parameters by implementing controlled cooling at specific rates through the sigma phase formation temperature range. This parameter control produces an microstructure with enhanced corrosion resistance and mechanical properties, extending service life while maintaining manufacturing feasibility
Solution Approach 2:
The patent creates a composite microstructure within the austenitic stainless steel by controlling phase transformation during cooling. The resulting microstructure combines austenite with controlled amounts of transformation products, achieving superior corrosion resistance and mechanical properties compared to conventional alloys
3Ease of manufacture
If conventional alloys are used for drill string components, then initial material cost is reduced, but component reliability is reduced due to mechanical degradation and corrosion
Solution Approach 1:
The patent applies parameter changes through controlled thermomechanical processing that manages cooling rates through critical temperature ranges. This produces a microstructure with enhanced mechanical properties (yield strength, tensile strength, fatigue strength) and corrosion resistance, making the components suitable for demanding drilling applications
Solution Approach 2:
The patent employs preliminary thermomechanical processing (forging, rolling, or extrusion) at high temperatures followed by controlled cooling. This preliminary processing establishes a microstructure that provides superior mechanical properties and corrosion resistance, enhancing component reliability for drill string applications
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 corrosion resistance and mechanical properties of the alloys, extending their service life and reducing costs by preventing intermetallic precipitate formation, thus improving their suitability for demanding applications.
Implementation Method 1
cooling a workpiece including an austenitic alloy. During the at least one of thermomechanically working and cooling the workpiece, the austenitic alloy is at temperatures in a temperature range spanning a temperature just less than a calculated sigma solvus temperature of the austenitic alloy down to a cooling temperature for a time period no greater than a critical cooling time
Implementation Method 2
at least one of thermomechanically working and cooling a workpiece including an austenitic alloy
Data Source
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AI summary
A method of processing a workpiece to inhibit precipitation of intermetallic compounds includes at least one of thermomechanically processing and cooling a workpiece including an austenitic alloy. During the at least one of thermomechanically working and cooling the workpiece, the austenitic alloy is at temperatures in a temperature range spanning a temperature just less than a calculated sigma solvus temperature of the austenitic alloy down to a cooling temperature for a time no greater than a critical cooling time.