Stainless Steel Vane Pump Casing Nitriding Process
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Solution Overview
Problem
Vane pumps with steel casings, particularly stainless steel casings, face issues of casing wear due to contact with vanes, leading to material removal and premature vane wear, as well as fluid contamination from casing material.
Innovation Solution
A method involving the hardening of stainless steel pump casings through a two-stage heating process in a furnace, initially at 1100-1500°F for 3-5 hours and subsequently at 800-1200°F for another 3-5 hours, with purging using ammonia and inert gases to reduce wear and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel casings are used in vane pumps, then the structural strength and durability are improved, but casing wear occurs due to contact with vanes leading to material removal and fluid contamination
Solution Approach 1:
The patent applies nitriding treatment to the steel casing, which fundamentally changes the surface parameters of the material. Through controlled heating in a nitrogen-containing atmosphere, nitrogen diffuses into the steel surface, forming hard nitride compounds that dramatically increase surface hardness and wear resistance while maintaining the underlying steel's toughness and strength
Solution Approach 2:
The nitriding process creates a composite structure within the casing material. The surface layer becomes a composite of steel matrix and nitrogen-containing compounds (such as Fe4N, Fe3N), forming a hardened case that combines the wear resistance of nitride compounds with the ductility and strength of the base steel
2Ease of manufacture
If conventional steel casings are used, then manufacturing simplicity is maintained, but material removal from casing wall enters fluid flow causing contamination
Solution Approach 1:
The nitriding treatment modifies the surface parameters of the casing to create a wear-resistant layer that prevents material removal. The process changes the surface composition and structure through nitrogen diffusion, forming a protective layer that eliminates the harmful effect of casing material entering the fluid flow
3Reliability
If the casing is hardened through nitriding, then wear resistance is improved, but the manufacturing process complexity increases due to multiple heating stages and gas purging
Solution Approach 1:
The nitriding process is divided into distinct stages: initial heating to austenitizing temperature, holding to allow nitrogen diffusion, and controlled cooling. This segmentation of the hardening process into manageable stages allows for precise control of the microstructure development and surface hardness while maintaining process reliability
Solution Approach 2:
The patent employs a controlled atmosphere environment during the nitriding process, using specific gas compositions (such as ammonia or nitrogen-rich atmospheres) to facilitate nitrogen diffusion into the steel surface. The inert or controlled atmosphere prevents unwanted oxidation and ensures consistent nitriding results
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 effectively reduces casing wear and material embedding in vanes, minimizing fluid contamination and extending the lifespan of vane pumps by strengthening the stainless steel casings.
Implementation Method 1
conducting a first heating of the casing in the furnace at a first temperature ranging from about 1100 to about 1500° F. for a time period ranging from about 3 to about 5 hours
Implementation Method 2
purging the furnace with ammonia
Data Source
AI summary
A method for manufacturing a hardened casing for a vane pump is disclosed. The method includes providing a vane pump casing; hardening the casing by (i) cleaning the casing with a high pressure fluid containing abrasive material, (ii) loading the casing in a furnace, (iii) purging the furnace with an inert gas followed by purging the furnace with ammonia, (iv) conducting a first heating of the casing in the furnace at a first temperature of about 1200° F. for a time period of about 4 hours, (v) conducting a second heating of the casing in the furnace at a second temperature of about 1000° F. for a time period of about 4 hours, and (vi) cooling the casing and purging the furnace with an inert gas before removing the casing.