Impeller Weld Restraining Fixture for Titanium Warpage Control
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Solution Overview
Problem
Turbine engine impellers made from strong, lightweight titanium alloys are prone to warping during conventional welding repairs due to high temperatures, leading to inefficient and costly scrap rates, especially when complex shapes and expensive materials are involved.
Innovation Solution
A weld restraining fixture comprising a base plate and top ring, fabricated from nickel alloys, securely holds the impeller in place using tangs and bolts, preventing excessive warping during welding and heat treatment processes, and is compatible with automated welding systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional welding techniques are used to repair impellers, then welding repairs can be performed, but the impeller is subjected to high temperatures causing warpage
Solution Approach 1:
The patent applies preliminary action by pre-attaching restraining tangs to the impeller blades before the welding process. These tangs are positioned to contact the welding fixture, creating a constraint system that will prevent warpage during the subsequent welding and heat treatment operations. The tangs are prepared in advance to engage with the fixture's restraining surfaces.
Solution Approach 2:
The welding fixture serves as an intermediary between the impeller and the welding process. The fixture, with its restraining tangs and contact surfaces, mediates the thermal and mechanical stresses during welding by providing a stable reference framework. This intermediary structure absorbs and distributes the thermal expansion and contraction forces, preventing direct warpage of the impeller geometry.
2Ease of manufacture
If high temperatures are applied during welding and heat treatment, then welding repairs can be completed, but excessive warping of impeller shape occurs
Solution Approach 1:
The patent applies parameter changes by modifying the thermal process parameters through the restraining fixture. The fixture's rigid structure and thermal mass help control the temperature distribution and cooling rate during welding and heat treatment. By changing the thermal parameters (temperature distribution, cooling rate) through the fixture's presence, the warpage is minimized while still allowing the welding process to complete.
Solution Approach 2:
The restraining tangs and fixture structure provide a counteracting force against the thermal warping forces. As the impeller material expands and contracts during heating and cooling, the fixture's rigid tangs provide an opposing mechanical constraint that counterweights the warpage tendency, maintaining the impeller's geometric integrity throughout the thermal process.
3Productivity
If automated welding systems are used for efficiency, then productivity increases, but the protective apparatus must not compromise system efficiency
Solution Approach 1:
The welding fixture is segmented into separate, modular components including the base fixture body and detachable restraining tangs. This segmentation allows each component to be independently manufactured and positioned, simplifying the overall design while maintaining functionality. The modular tangs can be attached to specific blades as needed, reducing the complexity of the complete fixture system while preserving automated welding compatibility.
Solution Approach 2:
The fixture design incorporates self-alignment features where the restraining tangs automatically position themselves relative to the impeller blades during loading. The tangs are designed to engage with the fixture's restraining surfaces through simple geometric relationships, eliminating the need for complex adjustment mechanisms. This self-service positioning maintains productivity by reducing setup time and complexity.
Data Source
AI summary
The present invention provides an apparatus for use in automated welding repairs, particularly those repairs intended for impellers and similar structures. In one embodiment, the invention provides an impeller weld restraining fixture. The fixture includes a base plate and top ring. An impeller may be sandwiched between the base plate and the ring mount. Tangs located on the top ring may be fitted to rest in the valley faces between airfoils on an impeller. Bolting the top ring to the base plate, with the impeller firmly secured therebetween, restrains the impeller so as to minimize warpage during welding repairs and heat treatments.