Bearing Steel Cold Workability via Spheroidizing Annealing
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Solution Overview
Problem
Existing bearing steels face challenges in cold workability, leading to increased deformation resistance and reduced manufacturing efficiency, which hinders the production of high-quality bearing components and contributes to higher costs and CO2 emissions.
Innovation Solution
A bearing steel composition with specific elemental ranges (C: 0.95-1.10%, Si: 0.10-0.30%, Mn: 0.1-0.40%, Cr: 1.00-1.50%, Ni: 0.01-0.05%, Cu: 0.01-0.05%, Mo: 0-0.03%) and spheroidizing annealing conditions (average cooling rate of 8 °C/s after hot rolling, heating rate of 100-150 °C/hr, and cooling rate of 50-150 °C/hr) to optimize the microstructure and reduce deformation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spheroidizing annealing is performed to improve cold workability, then the hardness is reduced and cold workability is improved, but the spheroidizing time increases and production costs increase
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition parameters (C: 0.95-1.10%, Si: 0.10-0.30%, Mn: 0.10-0.40%, Cr: 1.00-1.50%, Ni: 0.01-0.05%, Cu: 0.01-0.05%, Mo: 0.00-0.03%) and spheroidizing annealing parameters (heating rate: 100-150°C/hr, holding temperature: 780-800°C, holding time: 1-2 hours, cooling rate: 50-150°C/hr) to achieve both reduced spheroidizing time and improved cold workability. The specific composition ranges and heat treatment parameters work together to accelerate the spheroidizing process while ensuring the cementite particles achieve the required morphology (circularity coefficient ≥ 0.80) for good cold workability.
2Strength
If high C and Cr contents are used to improve bearing steel properties, then the strength and wear resistance are improved, but eutectic carbide formation increases and diffusion annealing becomes essential
Solution Approach 1:
The patent applies parameter changes by precisely controlling the C content (0.95-1.10%) and Cr content (1.00-1.50%) within specific ranges that allow achieving high strength and wear resistance without excessive eutectic carbide formation. The balanced composition with controlled amounts of Si (0.10-0.30%), Mn (0.10-0.40%), Ni (0.01-0.05%), Cu (0.01-0.05%), and Mo (0.00-0.03%) works synergistically to maintain austenite stability and promote spheroidization during the simplified heat treatment process, eliminating the need for complex diffusion annealing while still achieving the desired bearing steel properties.
3Ease of operation
If conventional spheroidizing annealing is used to reduce hardness, then cold workability is improved, but the microstructure uniformity is insufficient and deformation resistance remains high
Solution Approach 1:
The patent applies parameter changes by optimizing the heating rate (100-150°C/hr), holding temperature (780-800°C), and holding time (1-2 hours) during spheroidizing annealing to achieve uniform microstructure with spheroidal cementite particles having a circularity coefficient of 0.80 or more. The controlled cooling rate (50-150°C/hr) further ensures uniform microstructure development. This optimized parameter combination reduces deformation resistance more effectively than conventional methods while maintaining microstructure uniformity, enabling better cold workability.
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 optimized steel exhibits improved cold workability, allowing for more efficient manufacturing of bearing components with reduced deformation resistance, extended die life, and lower CO2 emissions, while also reducing spheroidizing time and costs.
Implementation Method 1
spheroidizing annealing is carried out before cold working
Implementation Method 2
the microstructure of the steel after the spheroidizing annealing
Implementation Method 3
boundary Si, boundary Ni, boundary Cu, boundary Mo, boundary Mn, and boundary Cr included in a region (boundary region) from a boundary surface of spheroidal cementite
Data Source
AI summary
This bearing steel material satisfies a predetermined elemental composition, and is characterized by having, in the region (boundary region) from the boundary surface of spheroidal cementite to a position at 20 nm away in a base material, no greater than 0.6% (excluding 0%) of Si (boundary Si), no greater than 0.10% (excluding 0%) of Ni (boundary Ni), no greater than 0.10% (excluding 0%) of Cu (boundary Cu), no greater than 0.03% (including 0%) of Mo (boundary Mo), no greater than 0.10% (excluding 0%) of Mn (boundary Mn), and no greater than 0.9% (excluding 0%) of Cr (boundary Cr), and the circularity coefficient of the spheroidized cementite being at least 0.80. The bearing steel material exhibits favorable cold-workability during the production of a bearing component by means of cold working.