Cryogenic Treatment - 9 Key Measures to Prevent Quenching Oil Degradation and Aging 

Cryogenic Treatment - 9 Key Measures to Prevent Quenching Oil Degradation and Aging

The cooling characteristics of quenching oil directly impact heat treatment quality. Quenching oils operate under far harsher conditions than mechanical oils, and their physicochemical properties, cooling performance, and brightness can deteriorate over extended use. Proper maintenance, care, and management are crucial to prolonging the service life of quenching oils.

The following measures can be taken to slow down the degradation and aging of quenching oil:

1. Preventing External Contamination

Carbon Black Control:
Carbon black from heat treatment furnaces can enter the oil tank with workpieces, acting as a potent adsorbent for oil additives and accelerating their depletion. To mitigate this:
Continuous Gas Carburizing Furnaces/Multi-Purpose Furnaces: Burn off carbon black monthly and regularly clean the furnace interior.
Pit Gas Carburizing Furnaces: Shut down monthly to remove accumulated carbon black, minimizing contamination of the quenching oil.
Cooling System Leakage Check:
Inspect cooling systems (e.g., heat exchangers) for water leaks every six months.
Regular Filtration:
Periodically filter the quenching oil to remove contaminants and foreign particles.
2. Quenching Oil Tank Requirements

New Oil Tanks:
Coat both internal and external surfaces with rust-preventative paint before filling with new oil. Thoroughly clean the tank, cooling system, and reservoir to prevent contamination.
Replacing Oil in Existing Tanks:
Thoroughly clean the tank to remove residual water, sludge, and oil residues. Clean the tank walls, frames, and heaters below the oil level to prevent contamination of the new oil, which could impair its brightness and cooling properties.
Periodic Tank Cleaning:
Drain the tank regularly and remove accumulated water, scale, and sludge from the bottom.
3. Operating Temperature Control

Adhere to the manufacturer's recommended temperature range.
Excessive Temperature:
While higher temperatures reduce workpiece distortion due to smaller temperature differentials, they accelerate oil oxidation, aging, and cooling capacity decline.
Excessively Low Temperature:
Lower temperatures increase oil viscosity, reduce flowability, and diminish cooling capacity, potentially compromising quenching quality, despite slower oxidation and aging.
4. Cooling and Agitation

Implement a circulation cooling system to maintain oil temperature within the specified range.
Utilize agitation systems within the oil tank during quenching to prevent localized overheating, ensure uniform oil temperature, slow down oil degradation, extend oil life, and minimize workpiece distortion.
5. Oil Capacity Management

The rate of oil degradation increases with the total mass of workpieces quenched within a given timeframe. Maintain a reasonable ratio between oil capacity and workpiece volume.
Recommended Oil Capacity Ratios:
Direct Replacement Cooling: 3-7 times the workpiece weight.
Serpentine Coil Cooling: 7-12 times the workpiece weight.
Natural Cooling: 12-15 times the workpiece weight, with a minimum 5-12 hour interval between quenching cycles.
6. Heat Treatment Process Optimization

Bright Quenching Oil/Rapid Bright Quenching Oil:
In a controlled atmosphere, the service life is typically 1-2 years.
In a poor atmosphere, brightness and cooling performance can significantly deteriorate within six months, necessitating adjustments.
Rapid bright quenching oil degradation is generally more severe than bright quenching oil.
Additive Depletion:
Under normal atmospheric conditions, additive loss is primarily due to burning, decomposition, and workpiece carry-out.
Process adjustments must prioritize maintaining a良好的炉气气氛 (good furnace atmosphere) to preserve oil performance.