Rolling Bearing Alloy Composition for High-Speed Burning Resistance
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Solution Overview
Problem
Conventional rolling bearings for machine tools experience high burning resistance issues due to metal contact on the rolling contact surface, leading to wear, adhesion, and vibration, especially under high PV values and Dmn values, which result in reduced machining accuracy and increased temperature.
Innovation Solution
A rolling bearing design featuring alloy steel rolling elements with specific silicon and manganese content, thermal treatment, and nitride formation to enhance quenching properties and martensite, along with controlled retained austenite amounts, to improve wear and indentation resistance, and a lubrication system with low kinematic viscosity to prevent metal contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-viscosity lubricating oil is used to decrease torque and heat generation, then energy loss is reduced, but metal contact occurs more frequently leading to wear and burning
Solution Approach 1:
The invention changes the chemical composition parameters of the steel material by specifying precise ranges of alloying elements (Si: 0.5-2.0%, Mn: 0.5-2.0%, Cr: 1.0-2.0%, Mo: 0.1-0.5%, B: 0.005-0.05%) to achieve the desired balance between low viscosity operation and burning resistance
Solution Approach 2:
The invention creates a composite microstructure consisting of martensite as the primary phase with dispersed carbide precipitates, combining the high strength and hardness of martensite with the wear resistance provided by carbide particles
2Productivity
If high-speed rotation is achieved with Dmn value of 800,000 or more, then productivity is improved, but metal contact and surface roughness deterioration increase
Solution Approach 1:
The invention optimizes the chemical composition parameters to control the microstructure formation during cooling, achieving a martensitic structure with fine carbide distribution that maintains surface integrity at high rotation speeds
Solution Approach 2:
The invention performs preliminary alloying during the steelmaking process to ensure uniform distribution of alloying elements before rolling, which prevents surface defects and roughness during high-speed operation
3Strength
If retained austenite amount is increased to improve shock resistance, then durability under impact load is enhanced, but burning resistance decreases
Solution Approach 1:
The invention precisely controls the retained austenite content by adjusting the chemical composition (particularly C: 0.3-1.2%, Si: 0.5-2.0%, Mn: 0.5-2.0%) and cooling conditions to maintain austenite at 30% or less, achieving the optimal balance between shock resistance and burning resistance
Solution Approach 2:
The invention applies partial martensitic transformation rather than complete transformation, retaining a controlled amount of austenite (30% or less) to provide shock absorption while preventing excessive softening that would lead to burning
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 improved rolling bearing exhibits enhanced burning resistance, reduced surface roughness deterioration, and increased life, maintaining machining performance even under high-speed and high-pressure conditions.
Implementation Method 1
a rolling bearing which is lubricated with lubricating oil whose kinematic viscosity at 40°C is 1 to 5×10 -5
Implementation Method 2
a nitride precipitate containing 5% or more Si by weight is had on a surface layer part of a rolling surface
Data Source
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AI summary
The quantity of residual austenite (γRAB) in a surface layer part of an inner ring (1) and of an outer ring (2) exceeds 0 vol.%. A ball (rolling element) (3) is obtained by processing a raw material comprising a steel alloy which contains 0.3-2.2 mass % of Si and 0.3 mass % to not more than 2.0 mass % of Mn and in which the Si/Mn mass ratio is not higher than 5, and then carrying out heat treatment, including carbonitriding or nitriding. Si·Mn-based nitrides comprising nitrides of silicon (Si) and nitrides of manganese (Mn) are present on the rolling surface of the ball (3) at an areal ratio of 1.0-20.0%. The content of N in the surface part of the ball (3) is 0.2 mass % to not more than 2.0 mass %, and the quantity of residual austenite (γRC) is higher than 0 vol.% and not higher than 50 vol.% and satisfies formula (1). γRAB-15 ≤ γRC ≤ γRAB+15 (1)