Bearing Steel Wire Rod Cooling to Control Carbide Network
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Solution Overview
Problem
Existing methods for producing bearing steel wire rods fail to effectively control the formation of carbide networks, leading to increased brittleness and reduced fatigue life due to uneven cooling and rolling processes, which result in micro and quenching cracks.
Innovation Solution
A method involving controlled rolling and cooling using EDC water bath austempering, followed by slow cooling under a cover, to achieve uniform temperature and prevent excessive Fe3C precipitation, resulting in a carbide network level reduction from >3.0 to ≤2.5 in high-carbon-chromium bearing steel wire rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air cooling is used after spinning, then the wire rod can be cooled down, but a large temperature difference occurs between the midpoint and lap point, causing uneven carbide network quality
Solution Approach 1:
The patent introduces an intermediary cooling medium (water or water-glycol mixture) between the hot wire rod and ambient air to achieve uniform cooling. The cooling medium flows through channels in contact with the wire rod surface, acting as a heat transfer intermediary that distributes cooling uniformly across the entire wire rod surface, eliminating the temperature differential caused by direct air cooling.
Solution Approach 2:
The patent employs hydraulic cooling by circulating water or water-glycol mixture through channels in direct contact with the wire rod. This hydraulic cooling system uses fluid dynamics to transfer heat uniformly from the wire rod surface, ensuring consistent cooling rate across different sections (midpoint and lap point) and preventing uneven carbide network formation.
2Quantity of substance
If slow cooling is used after rolling, then the carbide network may be reduced, but micro cracks form along grain boundaries reducing service life
Solution Approach 1:
The patent changes the cooling parameters by using a controlled cooling medium (water or water-glycol) with specific flow rates and temperatures, rather than relying on ambient air cooling. The cooling rate is precisely controlled within 5-50°C/s, which suppresses carbide precipitation while avoiding the formation of micro cracks along grain boundaries, thus maintaining both reduced carbide content and high reliability.
3Ease of manufacture
If conventional rolling and cooling methods are used, then the process is simple, but serious carbide network forms reducing fatigue life
Solution Approach 1:
The patent applies preliminary action by implementing controlled cooling immediately after rolling while the steel is in the austenitic state. The cooling medium is applied right after the rolling process to suppress carbide precipitation during the critical transformation period, preventing serious carbide network formation before it can occur during subsequent slow cooling or air cooling.
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 method ensures a uniform carbide network structure, reducing brittleness and extending the fatigue life of bearing parts by maintaining a controlled cooling rate and temperature, while using an environmentally friendly cooling medium that avoids pollution and surface stress.
Implementation Method 1
on-line controlling cooling of continuous loose coils using EDC water bath austempering cooling process, controlling the cooling rate at 2.0°C/s-10°C/s
Implementation Method 2
using slow cooling under a cover, and the temperature is controlled to be 400°C-500°C when being removed out of the cover
Implementation Method 3
After slow cooling, collecting coils, and cooling in air to the room temperature
Implementation Method 4
cooling in air to the room temperature
Implementation Method 5
rapidly rolling a bar to a wire rod with a specified specification
Data Source
Figure 1~2
AI summary
The invention relates to a method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling, and the process is characterized by comprising the following steps: rapidly rolling a bar to a wire rod with a specified specification and spinning it into a loose coil, controlling the rolling temperature at 780°C-880°C; and the spinning temperature at 750°C-850°C; carrying out on-line controlling cooling of continuous loose coils using EDC water bath austempering cooling process, controlling the cooling rate at 2.0°C/s-10°C/s, and controlling the final cooling temperature within 620-630°C; after EDC water bath austempering cooling, using slow cooling under a cover, and the temperature is controlled to be 400°C-500°C when being removed out of the cover; after slow cooling, collecting coils, and cooling in air to the room temperature. EDC water bath austempering + slow cooling under a cover is used for controlling cooling of the coils, which effectively inhibits precipitation of carbide in the cooling process, so that non-equilibrium microstructure is obtained to form short-strip or hemispherical carbides, thereby finally controlling the carbide network.