Stainless Steel Brake Disc Composition and EBSD Quality Control
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Solution Overview
Problem
Current brake discs for two-wheeled vehicles face challenges in achieving high heat resistance, quenching toughness, and quality control due to increased alloy elements and complex heat treatment processes, which elevate production costs and complicate structure evaluation.
Innovation Solution
A stainless steel brake disc composition and production method involving a low carbon martensitic stainless steel with controlled heating conditions and electron backscatter diffraction (EBSD) for precise structure evaluation, optimizing ferrite phase fraction and nitrogen content to balance toughness, corrosion resistance, and quenched hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If alloy elements (Nb, Mo, etc.) are added to improve heat resistance, then heat resistance is improved, but alloy cost and production cost increase
Solution Approach 1:
The invention changes the chemical composition parameters by strictly limiting alloy element contents (Nb≤0.10%, Mo≤0.10%, Ti≤0.05%, V≤0.05%, B≤0.005%) and controlling carbon content (0.030-0.080%) to achieve heat resistance without excessive alloying. This parameter optimization resolves the contradiction by finding a balance point where sufficient heat resistance is obtained with minimal alloy cost.
Solution Approach 2:
The invention applies local quality control through specific microstructural requirements (ferrite phase fraction of 1-15%, martensite account for 75% or more of quenched structure, prior austenite grain size of 8 μm or more) to achieve localized heat resistance properties where needed, rather than uniformly increasing alloy content throughout the material.
2Temperature
If quenching retention time is increased to improve heat resistance, then heat resistance is improved, but production time and energy consumption increase
Solution Approach 1:
The invention performs preliminary action by controlling the prior austenite grain size to 8 μm or more through composition design before quenching, which pre-establishes the microstructural conditions necessary for heat resistance. This allows the quenching process to proceed quickly (0.1-5 seconds retention time) without sacrificing heat resistance, as the grain structure is already optimized in advance.
Solution Approach 2:
The invention changes the quenching retention time parameter to an optimized range (0.1-5 seconds) that is significantly shorter than conventional processes, while compensating for the reduced time by controlling other parameters (heating temperature of 950-1050°C, composition ratios) to maintain heat resistance.
3Strength
If nitrogen content is increased to improve toughness and corrosion resistance, then toughness and corrosion resistance are improved, but quenching hardness may be affected
Solution Approach 1:
The invention changes the nitrogen content parameter to a specific range (0.015-0.060%) that simultaneously achieves toughness improvement and maintains quenching hardness within the required range (32-38 HRC). This precise parameter control resolves the contradiction by identifying the optimal nitrogen level that balances multiple competing requirements.
Solution Approach 2:
The invention creates a composite microstructure consisting of martensite (75% or more) with controlled ferrite phase (1-15%), where the interaction between these phases, combined with optimized nitrogen content, achieves both toughness and hardness requirements that cannot be met by a single phase or composition alone.
4Duration of action of stationary object
If prior austenite grain size is increased to improve temper softening resistance, then temper softening resistance is improved, but manufacturing precision and quality control become more difficult
Solution Approach 1:
The invention replaces direct mechanical measurement of grain size with EBSD (electron backscatter diffraction) technology to evaluate the prior austenite grain size indirectly through crystallographic orientation analysis. This substitution enables precise quality control of the 8 μm or more grain size requirement without the difficulties of direct optical measurement.
Solution Approach 2:
The invention uses EBSD as an intermediary tool to bridge the gap between the microstructural property (prior austenite grain size) and quality control requirements. The EBSD technique provides quantitative data on grain size and phase distribution, enabling precise manufacturing control of the temper softening resistance without direct observation of the grain structure.
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 solution results in a brake disc with enhanced toughness, corrosion resistance, and wear resistance, while maintaining cost efficiency and facilitating quality control through precise structural analysis.
Implementation Method 1
electron backscatter diffraction (EBSD) for precise structure evaluation
Implementation Method 2
a martensitic stainless steel sheet is used as a brake disc for a two-wheeled vehicle. Heretofore, SUS420J2 has been quenched and tempered
Implementation Method 3
heating conditions of quenching, structures, and components on toughness of a low carbon martensitic stainless steel
Data Source
AI summary
The present invention is directed to a stainless steel brake disc which is excellent in toughness, corrosion resistance, and wear resistance, and comprises, in % by mass, 0.030 to 0.080% of C, 0.05% to 1.0% of Si, 1.0 to 1.5% of Mn, 0.035% or less of P, 0.015% or less of S, 11.0 to 14.0% of Cr, 0.01 to 0.50% of Ni, 0.001 to 0.15% of V, less than 0.1% of Nb, 0.05% or less of Ti, 0.05% or less of Zr, 0.05% or less of Al, 0.015 to 0.060% of N, 0.0002% or more and 0.0050% or less of B, and 0.0080% or less of O, wherein an AT value of equation 1 is 0.055 to 0.090, equation 2 is satisfied, a ferrite phase fraction, in which an IQ value of an EBSD pattern is 4,000 or more, is 1% to 15%, a Charpy impact value is 50 J/cm2 or more, and hardness is 32 to 38 HRC.C+0.8(N−B) (1)PV=1.2Ti+0.8Zr+Nb+1.1Al+O≦0.1 (2)