Quenching and Distortion
We introduced the IFHTSE Liquid Quenchants Database project about one year ago. The project plan is to carry out a comparative study of quenchants under strictly specified conditions and collate the resulting data for use worldwide. It is fully recognized that an exhaustive study of all quenchant types and all conditions is not practical. Therefore, a limited but achievable procedure is being followed over a two-phase project.
The project basis is that simulation of the quenching process has become a widely accessible engineering tool over the last three decades, and these computer models need heat-transfer data.
The challenge is that there is a huge range of liquid quenchants of varying provenance and grade in everyday industrial use globally: oils, polymer solutions, water, brine and salt bath. Any of these can be used in different conditions and at different temperatures, agitation rates, etc. The combination of possibilities is large.
There is, however, no generally recognized method and technique for measurement, recording and comparison of relative cooling intensities of different quenchants.
Many advances in practice and method have been made over the last few years. Therefore, it is of great benefit to existing and potential users of liquid quenchants to have a better comparative idea of these developments, especially in light of their importance (e.g., intensive quenching, delayed quenching, spray quenching, etc.).
Here is the two-phase project plan.
• Phase 1: Collect and collate experimental results from a group of investigators to build a database.
• Phase 2: Use the information from Phase 1 to improve numerical models and develop software.
As we reported earlier, Phase 1 involved extensive collaboration among a multinational group of oil suppliers and evaluators (using three types of oil, three different temperatures for each coolant and three repetitions). The outcome was that the inevitable scatter in the results reported was larger than expected. The experiments carried out during Phase 1 of the project did show, however, that acceptable agreement of the temperatures recorded in laboratories in four continents can be achieved by using the ISO 9950 method. Importantly, for improved predictability in routine industrial practice, the project is confirming that cooling-curve deviation can result from small differences in instrumentation and from insufficient precision in matching the conditions during measurements to the specifications.
Therefore, the project partners are now working on:
• Better-defined and strictly complied-with conditions to be followed during cooling-curve acquisition using the project’s “standard” oil quenchants. Three different types of oil are being analyzed at three specified temperatures. By strict application of the specified procedure and conditions (including sampling), better results with less scatter should be achieved.
• A benchmark test of the inverse heat-conduction algorithms applied by the partners will be a better indication of performance. This test includes five cooling curves generated by an FEM model of an ISO 9950 probe using five different hypothetical HTC(T) functions.
Each partner is required to generate the thermal-boundary condition functions to reconstruct the HTC(T) functions. Inverse results will be obtained from the predicted heat-transfer coefficients.
Quenching understanding and control is, of course, central to minimizing component distortion during processing. The English term “distortion engineering” was originally coined by Peter Mayr and the IWT project team in Bremen, Germany. The subject covers a lot of ground, and it has become almost a brand name for the scientific approach to the understanding and control of distortion phenomena. The term has been generally accepted for several years now. The definition agreed to between IWT and IFHTSE is this: the scientific and technological investigation of the origins and causes of geometrical inadequacy during the manufacture of engineering components, and the measures and procedures that can be taken to compensate for, or minimize, them.
IFHTSE is pleased, therefore, to see that IWT Bremen (Germany) is re-introducing its series of conferences on distortion engineering. The next event – the 5th International Conference on Distortion Engineering 2015 – is scheduled for Sept. 23-25 in Bremen. Visit www.distortion-engineering.de for more information. IH