High Al Ferritic Steel Sensor Substrate Adhesion
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Solution Overview
Problem
Existing metal base materials for mechanical quantity sensors, such as stainless steel, suffer from insufficient glass adhesiveness and high temperature oxidation resistance, limiting their practical use in harsh environments due to mismatched linear expansion coefficients with crystallized glass layers.
Innovation Solution
A high aluminiferous ferritic stainless steel sheet with specific compositions of Cr, Al, Nb, V, Ti, and Zr is developed, which has a controlled linear expansion coefficient matching that of crystallized glass, enhancing adhesiveness and oxidation resistance when sintered with a glass layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stainless steel is used as a metal base material for mechanical quantity sensors, then the sensor can be manufactured with standard materials, but the glass adhesiveness and high temperature oxidation resistance are insufficient due to mismatched linear expansion coefficients with crystallized glass layers
Solution Approach 1:
The invention changes the physical and chemical parameters of the stainless steel by precisely controlling the composition ranges of Cr (12-30%), Al (2.5-8%), Nb (0.05-0.5%), C (0.025% or less), and N (0.025% or less). This composition control adjusts the linear expansion coefficient to match that of crystallized glass, thereby improving glass adhesiveness and oxidation resistance without sacrificing material compatibility
Solution Approach 2:
The invention creates a composite material system by combining stainless steel with specific alloying elements (Cr, Al, Nb, C, N) to form a high aluminiferous ferritic stainless steel. This composite composition achieves synergistic effects where Cr provides oxidation resistance, Al controls linear expansion, and Nb refines grain structure, collectively resolving the contradiction between glass adhesiveness and material compatibility
2Reliability
If the linear expansion coefficient of stainless steel is reduced to match crystallized glass, then glass adhesiveness improves, but high temperature oxidation resistance may deteriorate
Solution Approach 1:
The invention simultaneously optimizes multiple composition parameters: Cr content (12-30%) for oxidation resistance, Al content (2.5-8%) for linear expansion control, and Nb content (0.05-0.5%) for grain refinement. This multi-parameter optimization ensures that both glass adhesiveness and oxidation resistance are improved without trade-offs
Solution Approach 2:
The high aluminiferous ferritic stainless steel forms a composite microstructure where Cr-rich oxides provide oxidation protection while Al-modified phases control thermal expansion. The synergistic interaction between these alloying elements creates a material that simultaneously achieves both glass adhesiveness and oxidation resistance
3Object-affected harmful factors
If high chromium content stainless steel is used to improve oxidation resistance, then oxidation resistance improves, but linear expansion coefficient mismatch with glass increases
Solution Approach 1:
The invention balances Cr content (12-30%) with Al content (2.5-8%) to achieve both oxidation resistance and linear expansion control. The Al element specifically targets the linear expansion coefficient to match glass, while Cr maintains oxidation resistance, resolving the contradiction between these two properties
Solution Approach 2:
The Al element acts as an intermediary that mediates between the high Cr content (for oxidation resistance) and the linear expansion coefficient matching requirement. By introducing Al, the invention decouples the relationship between oxidation resistance and linear expansion, allowing both Cr and Al to work synergistically to achieve their respective functions independently
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 high aluminiferous ferritic stainless steel sheet provides excellent glass adhesiveness and high temperature oxidation resistance, ensuring reliable operation of sensor substrates even at elevated temperatures, thereby improving the functionality of mechanical quantity sensors.
Implementation Method 1
each of the component elements interdiffuses between the metal base material and the crystallized glass layer and also between the crystallized glass layer and a resistive element, and thus the adhesiveness between them is very strong
Implementation Method 2
an insulating glass layer and the layers of a resistive element and electrodes are solidified by baking
Implementation Method 3
the average linear expansion coefficient of said stainless steel is 13.5 to 15.5×10−6/° C. in the temperature range from 20° C. to 900° C.
Data Source
AI summary
The present invention provides a stainless steel as a metal base material for a weight sensor substrate of an automobile airbag. The stainless steel sheet contains a high aluminiferous ferritic stainless steel containing, in mass,Al of 2.5 to 8%,C: 0.025% or less,N: 0.025% or less,the sum of C and N being 0.030% or less, andNb: 0.05 to 0.5%,with the balance Fe and unavoidable impurities. Said stainless steel sheet may further contain, in mass, one or more ofV: 0.05 to 0.4%,Ti: 0.02 to 0.2%, andZr: 0.02 to 0.2%.The present invention controls the difference in the average linear expansion coefficient between said stainless steel sheet and crystallized glass for said weight sensor to less than 10% in the temperature range from 20° C. to 900° C. and thus to improve the adhesiveness of said stainless steel sheet with said crystallized glass.