Ferritic Stainless Steel Sintering with Ti and Nb Additions
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Solution Overview
Problem
Ferritic stainless steel sintering processes often result in a thin dense layer on the surface, which is easily lost during polishing, leading to inadequate mirror finish performance and corrosion resistance due to uneven sintering progress between the surface and interior.
Innovation Solution
A sintering metal powder composition containing C and Nb, with specific content ranges, is used to slow down the sintering rate and inhibit gas retention, resulting in a thicker dense layer with improved mirror finish and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ferritic stainless steel powder is sintered using conventional methods, then sintering speed is fast due to high diffusion rate, but the dense layer becomes thin and pores are generated inside
Solution Approach 1:
The patent changes the chemical composition parameters of the ferritic stainless steel powder by adding specific amounts of Ti (0.01-1.00 mass%) and Nb (0.01-1.00 mass%). These compositional changes modify the sintering behavior to reduce the diffusion rate, allowing sufficient time for gas escape while maintaining surface densification, thereby forming an adequate dense layer thickness without sacrificing overall sintering efficiency
Solution Approach 2:
The patent introduces Ti and Nb elements as intermediary substances that mediate the sintering process. These elements act as diffusion barriers and grain growth inhibitors, controlling the sintering rate to prevent premature surface densification while allowing internal pores to be eliminated. The Ti and Nb serve as mediators between the conflicting requirements of fast sintering and adequate dense layer formation
2Manufacturing precision
If the surface layer is sintered first due to high diffusion rate, then surface densification is achieved, but pores are confined inside and mirror finish performance deteriorates
Solution Approach 1:
By modifying the chemical composition with Ti and Nb additions, the patent changes the sintering kinetics to achieve more uniform densification throughout the material. This prevents the formation of a thin dense layer that would be removed during polishing, ensuring that the final polished surface maintains both aesthetic quality and corrosion resistance
Solution Approach 2:
The patent applies prior cushioning by pre-forming a sufficiently thick dense layer through controlled sintering with Ti and Nb additions. This dense layer acts as a cushion or reserve that withstands the material removal during polishing without exposing internal pores, thereby preserving mirror finish performance and corrosion resistance even after surface finishing operations
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 approach ensures a sintered metal body with a thick dense layer that maintains mirror finish performance and corrosion resistance, even after polishing, while maintaining the nickel-free characteristic of ferritic stainless steel.
Implementation Method 1
the ferritic stainless steel is characterized by a relatively low crystal structure filling rate, resulting in a high diffusion rate and good densification
Data Source
AI summary
A sintering metal powder to be used in sintering contains: a composition of ferritic stainless steel; C having a content of 0.05 mass % or more and 1.00 mass % or less; Nb having a content of 0.05 mass % or more and 1.50 mass % or less; and impurities. In addition, C/Nb may be 0.10 or more and 1.80 or less, where C/Nb is a ratio of the content of C to the content of Nb.