Comparison Between Vacuum Oil Quenching Furnace and Gas Quenching Furnace & Related Problems of Oil Surface Pressure During Oil Quenching

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Shanghai Gegang Vacuum Technology Co., Ltd. is a manufacturer with many years of production, design and research and development of vacuum heat treatment. The following is the comparison between vacuum oil quenching furnace and gas quenching furnace and the problem of oil surface pressure summarized according to many years of experience.

Comparison between vacuum oil quenching furnace and gas quenching furnace:

First, the cost of gas quenching is higher than that of oil quenching for furnaces of the same specification (furnace loading capacity). The reason for the high cost is that nitrogen consumption is greater than oil, the working cycle is longer, and the material frame and components in the furnace are easier to lose under the frequent exchange of cold and heat.

Second, the conventional furnace type, under the same power, the oil furnace is wider than the gas quenching furnace, gas quenching furnace for large diameter and poor hardenability of steel suitable surface is narrow.

Third, for steel with good hardenability, gas quenching is better than oil quenching, and the deformation and surface finish are also better.Conclusion: Gas quenching furnace is suitable for high-end products or special products, while oil quenching furnace is applicable to a wider range of products and lower production cost.If it is a small heat treatment plant, it is recommended to purchase the first oil quenching furnace, and gas quenching is more suitable for subsequent purchase and decoration.
Fourth, gas quenching furnace with diffusion pump can make high value products such as high speed steel, beryllium copper, stainless steel, titanium alloy, and can be used for vacuum tempering. Oil quenching furnaces can’t do that.

Related problems of oil surface pressure during oil quenching:

First, in the process of oil quenching with the vacuum quenching furnace in the vacuum heat treatment furnace, the cooling capacity of the vacuum quenching oil decreases under the low vacuum pressure, and the quenching purpose may not be achieved for some steels.For this reason , before the use of vacuum quenching furnace quenching, it is necessary to fill the quenching chamber with high purity neutral or inert gas to create a certain pressure on the oil surface, so that the full quenching of steel can be realized and a bright surface can be obtained.The minimum surface pressure at which the same hardening hardness as at atmospheric pressure can be obtained is called the critical quenching pressure.The critical quenching pressure is related to the properties of vacuum quenching oil and the hardenability of steel.

Second, when the vacuum quenching furnace is used to quench the steel with poor hardenability, the way of inflating first and then adding oil should be selected for quenching.The oil level pressure should be above the critical quenching pressure.The general adjustment is about 5 ×104Pa, but it should not be less than 1.0×104Pa.

Third, for medium hardening steel should also be taken after the first gas into the way of quenching oil.The pressure of the oil surface can be adjusted at about 1.0×104Pa, but not lower than 5×103Pa.

Fourth, the steel with good hardenability can be quenched by inflating or not inflating. By inflating, the heating chamber of the vacuum heat treatment furnace can be filled with oil first, or the oil can be filled first.The inflatable pressure can be selected in the range of (2.5~5) ×104Pa when the inflatable pressure is used in the first way.

Fifth, in order to prevent and reduce the steam from entering and polluting the heating chamber of the vacuum quenching furnace, a higher charging pressure should be selected, and the gas used should be neutral or inert gas with high purity.After the way of inflating , you can fill the gas with low purity, and the inflating pressure can also be lower.Adoption of non-inflatable way to quench, that is, the workpiece before and after oil are not filled with neutral or inert gas.

Editing by Frank Lee

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