CVT Sheave Steel Composition for Wear and Fatigue Balance
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Solution Overview
Problem
Conventional CVT sheaves face challenges in achieving high wear resistance and bending fatigue strength, particularly under high torque applications, due to issues with machining resistance, surface roughness, and increased component costs associated with certain chemical compositions.
Innovation Solution
A steel material for CVT sheaves with specific chemical compositions, including adjusted silicon (Si), chromium (Cr), and manganese (Mn) contents, along with controlled carbon potential during carburizing, to enhance hardenability and retain austenite formation, thereby improving wear resistance and bending fatigue strength without using expensive elements like molybdenum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium steel or chromium molybdenum steel is used with carburizing and quenching to achieve high surface hardness (800 HV or more), then wear resistance is improved, but machining resistance increases and machining heat is generated causing hardness reduction
Solution Approach 1:
The patent changes the chemical composition parameters of the steel material, specifically setting Cr content to 1.80-1.90 mass%, Si content to 0.16-0.30 mass%, and Mn content to 0.70-0.90 mass%, along with controlling theFn1 parameter (7×Cr−6×Si+4×Mn) to 13.9-15.5. This optimized composition allows achieving high wear resistance with reduced machining resistance by balancing hardenability and machinability.
2Reliability
If shot peening is performed to increase surface hardness and residual compressive stress, then wear resistance and fatigue strength are improved, but surface roughness is adversely affected
Solution Approach 1:
The patent optimizes the chemical composition parameters to achieve high surface hardness (680-800 HV) and appropriate retained austenite volume fraction (13-28%) through controlled carburizing and quenching, thereby reducing or eliminating the need for shot peening and avoiding its adverse effect on surface roughness.
3Reliability
If high Cr, Si, and Mn contents are increased to achieve high surface hardness, then wear resistance is improved, but component cost increases
Solution Approach 1:
The patent optimizes the chemical composition by setting Cr content to 1.80-1.90 mass%, Si content to 0.16-0.30 mass%, and Mn content to 0.70-0.90 mass%, with theFn1 parameter controlled to 13.9-15.5. This balanced composition achieves high wear resistance while controlling material costs by avoiding excessive alloying.
4Reliability
If carburizing and quenching is performed to improve surface hardness, then wear resistance is improved, but bending fatigue strength may be reduced if hardness is reduced by machining heat
Solution Approach 1:
The patent optimizes the chemical composition to control hardenability and retained austenite formation, achieving a balance where surface hardness (680-800 HV) is sufficient for wear resistance while maintaining bending fatigue strength through appropriate retained austenite volume fraction (13-28%).
Solution Approach 2:
The patent performs carburizing and quenching to establish the desired surface hardness and retained austenite distribution before finishing operations, ensuring that the surface properties are optimized for both wear resistance and fatigue strength prior to any machining that could generate heat.
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 proposed steel material achieves high wear resistance and bending fatigue strength while maintaining manufacturability and reducing component costs, with Vickers hardness and retained austenite volume fraction optimized within specific ranges to enhance surface hardness and prevent excessive hardness reduction.
Implementation Method 1
In the process carbon (C) is caused to enter the steel and diffused therein in an austenite range equal to or higher than Ac3
Implementation Method 2
carbon (C) is caused to enter the steel and diffused therein
Implementation Method 3
the steel is quenched
Implementation Method 4
performing tempering and finishing
Data Source
AI summary
Steel materials for continuously variable transmissions sheaves, and methods for manufacturing a continuously variable transmission sheaves, are provided. In the disclosed steel materials for continuously variable transmission sheaves, the steel materials satisfy the following expressions: 13.9≤Fn1≤15.5, and 1.20≤Fn2≤4.35 (in which Fn1=7×Cr−6×Si+4×Mn; and Fn2=Al×N×104).