Brake Rotor Stainless Steel Plate with Fine Precipitates for Hot Strength
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Solution Overview
Problem
Martensitic stainless steel sheets for brake disc rotors face challenges in hardenability, formability, temper softening resistance, and high-temperature strength, particularly at elevated temperatures, which affect their productivity and performance in automotive applications.
Innovation Solution
The development of a martensitic stainless steel sheet with controlled chemical components and hot rolling conditions to produce fine precipitates, including Cr carbonitrides and intermetallic compounds, which enhances hardenability, formability, and temper softening resistance, while maintaining high-temperature strength, through specific heat treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cast iron is used for disc rotor to achieve good thermal conductivity and low cost, then thermal management is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent uses martensitic stainless steel as a composite material that combines the benefits of corrosion resistance with improved thermal properties. The specific composition (10-20% Cr, 0.05-0.5% C, 0.01-0.1% B) creates a material that forms a protective oxide layer for corrosion protection while maintaining adequate thermal conductivity for brake disc application.
2Reliability
If stainless steel is used to improve corrosion resistance, then reliability is improved, but thermal conductivity deteriorates
Solution Approach 1:
The patent optimizes the chemical composition parameters of stainless steel, specifically controlling Cr content at 10-20%, C at 0.05-0.5%, and B at 0.01-0.1%. These parameter changes balance corrosion resistance with thermal conductivity, making the material suitable for brake discs where both properties are critical.
3Strength
If martensitic stainless steel with high hardness is used to improve strength, then strength is improved, but formability deteriorates
Solution Approach 1:
The patent incorporates boron (0.01-0.1%) during the steelmaking process to refine grain structure and control precipitate formation. This preliminary action during manufacturing enables the steel to achieve high hardness through controlled precipitation hardening while maintaining adequate formability during forming operations by controlling the timing and nature of hardening.
4Weight of moving object
If disc rotor is made thinner to reduce weight, then weight is reduced, but high-temperature strength deteriorates
Solution Approach 1:
The patent creates a precipitation-hardened martensitic stainless steel composite structure with fine precipitates distributed throughout the matrix. This composite microstructure provides exceptional high-temperature strength that enables thinner disc rotor design, reducing weight while maintaining structural integrity at braking temperatures.
5Weight of moving object
If cast iron is used and made thinner to reduce weight, then weight is reduced, but metal flow during molding deteriorates
Solution Approach 1:
The patent replaces the casting process with a metal forming process. The martensitic stainless steel is formed through rolling and controlled deformation, substituting the mechanical casting system with a forming system that provides better metal flow and eliminates casting defects while enabling thinner section production.
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 resulting steel sheet exhibits improved hardenability, formability, and high-temperature strength, reducing temper softening and pad wear, and is suitable for thin, lightweight disc rotors in both two-wheeled and four-wheeled vehicles, ensuring stable braking performance across various conditions.
Implementation Method 1
The development of a martensitic stainless steel sheet with controlled chemical components and hot rolling conditions to produce fine precipitates, including Cr carbonitrides and intermetallic compounds, which enhances hardenability, formability, and temper softening resistance
Implementation Method 2
through specific heat treatment processes
Data Source
AI summary
A martensitic stainless steel sheet for a brake disc rotor, characterized by containing predetermined components and having, in a mother phase, precipitates with a particle size of 2 μm or less and a density of 0.01 to 20 pieces/μm2. The precipitates finely present in hot rolling and hot-rolled sheet annealing improves productivity in hardening, improves temper softening resistance of the steel sheet in use as a component, inhibits cracking in hot stamping, and inhibits reduction in high-temperature strength. Accordingly, the martensitic stainless steel sheet excellent in temper softening resistance, hardenability, formability, and high-temperature strength that is applicable to the disc rotor is provided.