Óleo de têmpera para tratamento térmico: princípios e métodos de seleção

Quenching oil for heat treatment: principles and selection methods

1. Heat treatment cooling curve

The heat treatment process typically consists of three stages: heating, holding, and cooling.

Heating is performed to transform pearlite into austenite, and the retention step is used to ensure complete austenitization.

The cooling method depends on the process, mainly controlling the cooling rate, which results in pearlite, bainite, martensite or mixed structures depending on the cooling rate.

Typically, martensite is produced during quenching, and tempered martensite (at low temperatures), troostite (at medium temperatures) and sorbite (at high temperatures) are produced based on different tempering temperatures after quenching.

The isothermal transformation curve of eutectoid steel is shown in Figure 1, which essentially reflects the inoculation time, the transformation completion time and the transformation products required for the transformation of eutectoid steel at different temperatures.

According to actual production conditions and the company's quality policy, the most suitable quenching oil should be selected through a comprehensive comparison that takes into account not only refrigeration performance requirements but also other technical indicators.

The selection process should consider the stability and oxidation resistance of the quenching oil, its repeatability and reproducibility of cooling performance, brightness, safety and cost.

The technical requirements for quenching oil as described in QB/T0001-2007, JB/T7951 and SH/T0220 must be met in terms of kinematic viscosity, flash point, ignition point, humidity, pour point, corrosion, brightness, saturated vapor pressure (for vacuum quenching oil), thermal oxidation stability, cooling performance, maximum cooling speed and cooling time during heat treatment.

6. Conclusion

The principle and method for selecting quenching oil have been introduced above.

The cooling performance of quenching oil is influenced by many factors, including base oil and additives, and covers a wide range.

Quenching is a crucial step in the heat treatment process and must be chosen very carefully.

After analyzing and comparing several options, a preliminary recommendation for quenching oil can be made. This recommendation must then be verified through testing, as well as consideration of its industry performance, market feedback and technical requirements, safety, quality, cost and other factors. Finally, the selection of quenching oil can be determined.

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