Alloy 718 Ring Rolling With Circularity Correction to Inhibit AGG
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Solution Overview
Problem
Existing methods struggle to prevent abnormal grain growth (AGG) in Fe—Ni based superalloys during the production of ring-shaped materials for aircraft engine parts, particularly in the circularity correction step of closed die forging, leading to impaired fatigue properties due to coarse grains.
Innovation Solution
A production method involving a finishing ring rolling step at 900 to 980°C, followed by a circularity correcting step without reheating, using a ring expander to maintain strain and inhibit grain growth, ensuring a high circularity and fine-grained structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If circularity correction is performed to obtain high degree of circularity, then circularity is improved, but abnormal grain growth occurs causing coarse grains
Solution Approach 1:
The patent applies preliminary action by performing circularity correction at a specifically controlled temperature range (700-900°C) before the closed die forging step. This preliminary temperature control prevents abnormal grain growth during circularity correction while maintaining high circularity, solving the contradiction between shape improvement and grain size control.
Solution Approach 2:
The patent changes the temperature parameter during circularity correction to a specific range (700-900°C) that prevents abnormal grain growth. By controlling this critical parameter, the patent achieves both high circularity and fine grain structure, resolving the technical contradiction between shape quality and microstructure quality.
2Reliability
If effective strain satisfying Expression (1) is applied in first hot working, then abnormal grain growth is prevented, but it is not practical to apply this strain to entire region of ring-shaped material
Solution Approach 1:
The patent changes the temperature parameter to a specific range (700-900°C) during circularity correction, which fundamentally alters the material's response to strain. This temperature control enables effective strain to be applied practically while preventing abnormal grain growth, resolving the contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent performs circularity correction as a preliminary step before closed die forging, at a temperature that pre-establishes conditions preventing abnormal grain growth. This preliminary action makes the subsequent forging process more feasible and reliable.
3Ease of manufacture
If ring-shaped material is heated to closed die forging temperature, then forging can be performed, but grains rapidly become coarse beyond pinning of delta phase
Solution Approach 1:
The patent performs circularity correction as a preliminary step that establishes fine grain structure before the main forging operation. This preliminary grain refinement ensures that even when heated to forging temperature, the grains remain controlled and do not grow excessively.
Solution Approach 2:
The patent introduces intermediate temperature control (700-900°C) as a new parameter between initial heating and final forging. This intermediate temperature parameter enables circularity correction without causing abnormal grain growth, while still allowing subsequent forging at higher temperatures.
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 produces a ring-rolled material with high circularity and inhibited grain growth, enhancing the fatigue characteristics of turbine parts by maintaining strain and preventing recrystallization, thus improving the reliability of aircraft engine components.
Implementation Method 1
a finishing ring rolling step, as a final step of the ring rolling, of heating a material for ring rolling in a temperature range of 900 to 980° C., and expanding a diameter of the material for ring rolling and also pressing the material for ring rolling in an axial direction thereof
Implementation Method 2
a circularity correcting step of improving a circularity of a ring-rolled material that has been rolled by the finishing ring rolling step, while expanding a diameter of the ring-rolled material
Data Source
AI summary
A method for producing a ring-rolled material of an Fe—Ni based superalloy, which has a high circularity, can inhibit AGG, and can inhibit grain growth. A method for producing a ring-rolled material of an Fe—Ni based superalloy having a composition of an Alloy 718 comprises: a finishing ring rolling step of heating a ring-shaped material for ring rolling having the composition, in a temperature range of 900° C. to 980° C., and performing finishing ring rolling; and a circularity correcting step of correcting an ellipticalness of the ring-rolled material that has been rolled in the finishing ring rolling step, while expanding a diameter of the ring-rolled material by using a ring expander including a pipe-expanding cone and a pipe-expanding die, wherein the ring-rolled material that has been rolled in the finishing ring rolling step is subjected to circularity correction without being reheated or after having been heated to up to 960° C.