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It’s Time for Another Look at Vacuum Oil Quenching

Factors affecting the appearance of vacuum quenched workpieces

Vacuum quenching often has high requirements for appearance. There are many factors that affect the appearance of vacuum quenching workpieces, including: vacuum degree, air leakage rate, cooling medium characteristics, materials, etc.; the iron, chromium, and nickel elements in the material are related to the furnace The remaining oxygen and water vapor interact with each other to color the surface; steel containing chromium and manganese elements will make the surface rough due to evaporation at high temperatures; stainless steel and heat-resistant alloys containing aluminum and titanium are sensitive to oxygen, and the color will darken; the purity of others is not enough when cooled. Trace amounts of active impurities color the surface of the workpiece; the brightness of oil quenching is lower than that of gas quenching; tempering (especially medium and high temperature tempering) can make the brightness slightly lower.

Vacuum quenching oil

Characteristics of vacuum quenching oil: low saturated vapor pressure, low critical pressure, good chemical stability, few impurities and carbon residue, and low acid value. The characteristic indicators of ordinary vacuum quenching oil change significantly as the liquid surface pressure decreases: the characteristic temperature decreases, the characteristic time lengthens, the boiling stage appears in a lower temperature range, the cooling time in the 800-400°C range is significantly longer than that under standard atmospheric pressure, and the steel is Under air pressure, the cooling capacity of oil decreases, and the low temperature area has a higher cooling rate.

Selection of vacuum quenching oil

Vacuum oil quenching is mainly suitable for workpiece materials including Cr12, Cr12MoV, H13, W18Cr4V, etc. Vacuum quenching oil has a high cooling rate and is suitable for quenching carburized workpieces. It can make the workpieces obtain a deeper hardened layer and achieve higher Metallographic grade, suitable for large-size die steel, tool steel, and bearing steel; vacuum quenching oil is suitable for medium-sized die steel, bearing steel, and high-speed steel; suitable for small-size tool and die steel, bearing steel, and high-speed steel, and can effectively control deformation and Prevent cracking.

Vacuum quenching refers to: the quenching of workpieces is carried out in a vacuum furnace. The quenching cooling medium is mainly gas (such as inert gas), vacuum quenching oil and water; vacuum quenching is widely used in a variety of parts, such as tool and die steel, high-speed Steel, stainless steel, carburized steel, etc.; according to the different quenching and cooling methods of the vacuum furnace, the vacuum furnace can be divided into vacuum air quenching furnace and vacuum oil quenching furnace. Vacuum carburizing technology requires a faster cooling speed, so the cooling method is vacuum quenching oil. cool down. Vacuum heat treatment gas quenching method is generally suitable for: tool steel, mold steel, high-speed steel, ultra-high strength, etc. Vacuum heat treatment oil quenching is generally suitable for: mold steel, high-speed steel, alloy structural steel, bearing steel, spring steel; vacuum heat treatment water The general scope of application of quenching: solution treatment of titanium alloys in the aerospace industry, solution treatment of cymbal bronze in elastic components of instruments, solution treatment of nickel-based and cobalt-based high elastic alloys in aerospace sensors, nickel-based constant elastic alloys and other precision alloys treatment and solution treatment of stainless steel.

The difference between vacuum air quenching and oil quenching

Compared with the conventional furnace type of vacuum oil quenching, vacuum air quenching has a narrower applicable range under the same power, especially for steel materials with larger diameters and poor hardenability; the cost of gas quenching in a furnace of the same size is higher than that of oil quenching, and nitrogen is more expensive than quenching oil. The consumption is large, and the material frame and the components in the furnace are also more likely to be lost; vacuum air quenching can realize vacuum tempering of high-speed steel, cymbal bronze, stainless steel and titanium alloys; the appearance of vacuum air quenching workpieces is obviously better than that of vacuum oil quenching workpieces. The brightness of vacuum oil quenching is 20%-30% lower than that of gas quenching; the application range of vacuum air quenching furnace is not as wide as that of vacuum oil quenching furnace, and the cooling speed of vacuum oil quenching is faster under the same pressure.