Stopper Rod Thermal Expansion Seal Using Graphitic Washer
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Solution Overview
Problem
Stopper rods for controlling molten metal flow face challenges in maintaining secure connections and gas tightness at high temperatures, leading to potential gas loss and oxidation of the metal due to expansion issues.
Innovation Solution
A stopper rod design featuring an elongated refractory body with a passageway and a carrier rod, utilizing an expandable graphitic composition between washers to compensate for thermal expansion, ensuring a secure seal and gas tightness by using a material with a lower coefficient of thermal expansion than the carrier rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cylindrical insert or sleeve is used to compensate for carrier rod expansion, then the connection security is improved, but the gas tightness deteriorates due to potential gaps and leakage paths
Solution Approach 1:
A graphitic washer is introduced as an intermediary element between the carrier rod and the cylindrical insert. This washer serves dual functions: it compensates for thermal expansion of the carrier rod and provides a gas-tight sealing surface against the insert, eliminating the gas leakage problem while maintaining connection security
Solution Approach 2:
The graphitic washer utilizes the parameter change of thermal expansion, but with a different coefficient than the carrier rod. The washer's expansion characteristics are specifically selected to match or exceed the carrier rod's expansion, ensuring continuous contact and sealing under thermal conditions
2Strength
If the carrier rod material is used for the insert, then the connection strength is improved, but the thermal expansion mismatch causes connection failure at high temperatures
Solution Approach 1:
Different parts of the assembly have different thermal expansion properties. The carrier rod uses a standard metallic material for strength, while the graphitic washer is specifically selected for its thermal expansion characteristics. This local differentiation allows each component to perform optimally under thermal conditions
Solution Approach 2:
The invention explicitly addresses thermal expansion by selecting a graphitic washer with a coefficient of thermal expansion that is no greater than that of the carrier rod. This ensures that the washer expands with the carrier rod rather than creating differential stress that would compromise the connection at high temperatures
3Ease of operation
If atmospheric air penetrates the stopper rod, then the gas tightness is compromised, but this causes oxidation of molten metal and lowers product quality
Solution Approach 1:
The graphitic washer is designed as a sacrificial sealing element that can be easily replaced. If gas tightness deteriorates over time, the washer can be quickly removed and replaced without affecting the expensive molten metal or requiring complex disassembly operations
Solution Approach 2:
The graphitic washer serves as an intermediary sealing element between the carrier rod and the cylindrical insert, creating a reliable barrier that prevents atmospheric air from penetrating into the stopper rod and contacting the molten metal
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 design effectively accommodates thermal expansion, maintaining a secure connection and preventing gas leakage, thereby enhancing the quality of the final product by preventing oxidation and ensuring consistent inert gas retention.
Implementation Method 1
by the material of the insert having a coefficient of thermal expansion no greater than that of the carrier rod, and by expansion of said expandable means, in use, being greater than that of the carrier rod
Implementation Method 2
the insert compresses a seal seated on said sealing surface
Data Source
AI summary
Stopper rod having an elongated body of refractory material, a passageway extending longitudinally in the body from an end thereof which is uppermost in use, a carrier rod having a part fixedly received in the passageway and a further part outside of the passageway for attachment to a lifting device for the stopper rod. The passageway has an enlarged part which defines a sealing surface spaced from the end of the body, an insert around the carrier rod having at least a part thereof received in the enlarged part, a retention element on the carrier rod, and an expandable element disposed between the insert and the retention element. The material of the insert has a co-efficient of thermal expansion no greater than that of the carrier rod. Expansion of the expandable element, in use, is greater than that of the carrier rod.