SYSTEM FOR PROCESS ANALYSIS AND HARDNESS PREDICTION WHEN QUENCHING AXIALLY-SYMMETRICAL WORKPIECES OF ANY SHAPE IN LIQUID QUENCHANTS

摘要

A new Temperature Gradient System has been designed for practical use when quenching real workpieces in any kind of liquid quenchants. The main hardware component of the system is a cylindrical probe of 50 mm Dia. × 200 mm assembled with three thermocouples, and the temperature data acquisition unit for automatic drawing of cooling curves. The accompanying software-package consists of three modules: The first one for calculation of the heat transfer coefficient, the second one for quenching process analysis by graphical presentation of different thermodynamic functions, and the third one for hardness distribution prediction on the axial section of axially-symmetrical workpieces of any complex shape. The hardness prediction 2-D program is based on a Finite Volume Method, by which cooling curves in every particular point of the axial workpiece section are calculated, and cooling times from 800 °C to 500 °C (t_(8/5)) determined. Using the known relation between the cooling time (t_(8/5)) and the distance from the quenched end of the Jominy specimen, for the relevant steel, the hardness can be predicted, at once, in every particular point of the axial workpiece section, which is the unique feature of this system. The system itself is designed to: record, evaluate and compare real quenching intensities during the whole quenching process, when different liquid quenchants with different conditions are used, and different quenching techniques have been applied.