Quenched in oil

H=0.5

Quenched in oil

H=1.0

MATHEMATICAL MODELLING • MEASURING AND DATA EVALUATION • NEW QUENCHANTS • NEW QUENCHING TECHNOLOGIES • PREDICTION OF MICROSTRUCTURE • PREDICTION OF HARDNESS DISTRIBUTION • MODELLING OF RESIDUAL STRESSES AND DISTORTION • DATA BASES • HARDENABILITY • HIGH PRESSURE GAS QUENCHING • http://qrc.fsb.hr

university of zagreb • Faculty of Mechanical Engineering and Naval Architecture • Croatia

Quenching in liquid quenchants

Measuring and recording the quenching intensity when real workpeaces are quenched in any liquid quenchant (oils and water-based solutions).

working range: Temperature: 20 °C to 80 °C Agitation rate: 0 to 1.4 m/s

A proprietary cylindrical probe of 50 × 200 mm, assembled with three thermocouples is used for calculation of the heat transfer coefficient.

High pressure gas quenching

To simulate different parameters for high pressure gas quenching (HPGQ) in vacuum furnaces (different gases, pressures and flow velocities), a modified Jominy specimen (20 mm Dia. × 100 mm) is heated by induction and cooled in this facility under controlled conditions. Relevant heat transfer coefficients can be calculated.

This unique facility is also used for establishing hardenability curves of steels, when gas quenched under specified conditions; an investigation initiated by the German Institute for Materials Science (Stiftung Institut für Werkstofftechnik – IWT), the University of Bremen.

working range: Gases: Nitrogen, Argon, Helium Pressures: up to 20 bar Flow velocity: up to 70 m/s

Isothermal quenching in salt bath

A proprietary salt bath for investigation of isothermal quenching processes – Martempering and Austempering. By the violent downward flow of liquid salt, a very effective quenching intensity is achieved, which is enhanced by automatic addition of small quantities of water. This enables to martemper workpieces of up to 150 mm cross-sections, and austemper workpieces of up to 30 mm thickness.

working range: Temperature: 180 °C to 450 °C Agitation rate: 0 to 0.6 m/s Water addition: 0 to 2 vol %

QUENCHING FACILITIES AVAILABLE AT THE CENTRE

INVESTIGATION AND RESEARCH POSSIBILITIES OF THE CENTRE

The investigation of heat transfer data at quenching (heat flux density; heat transfer coefficient) of real axially symmetric engineering components is based on experiments with a cylindrical probe of 50 mm Dia. × 200 mm, with three thermocouples, by applying the Temperature Gradient Method. Relevant probes for other shapes (plates, rectangular bodies, rings...) are optional.

Besides our own proprietary software, other well-known software packages (Matlab, SYSWELD, COMSOL, FLUENT) are used to calculate and predict the microstructure transformation, the as-quench hardness, the stress-strain development with residual stresses and distortions. Quenching intensity and results of quenching in every case depend on: the specific characteristic of the quenchant, its temperature and its agitation rate i.e. flow velocity. Since the aforementioned facilities enable changing of all of these conditions, every mathematical model and simulation can be experimentally validated. Quenching Research Centre is primarily devoted to steels, but it deals equally with aluminium and other light metals hardened by precipitation.

Quenching research centre is offering the following services:

• Selection of the optimal quenchant and quenching conditions for real workpieces based on the relevant drawing and required properties. Planning of quenching operation within the whole manufacturing process.

• Analysis of the quenching process by heat flux density and heat transfer coefficient as well as other thermodynamic functions, based on the cooling intensity measured by the proprietary probe of 50 mm Dia. × 200 mm.

• Prediction of the hardness distribution through the whole volume of axially-symmetric workpieces of any complex shape, after quenching and after tempering, based on workpiece drawing and experimentally established heat transfer coefficient (HTC).

• Mathematical modelling of microstructure, as-quenched hardness, residual stresses and distortions, based on known HTC, with experimental validation.

• Testing of new, improved, or used quenchants under different quenching conditions, based on the method used for real workpieces.

• Based on CFD analysis in real conditions, to improve existing or design new quenching equipment.

Long-term activities of the quenching research centre

• To establish a data base of quenching intensities for different quenchants and quenching conditions in order to enable their mutual comparison.

• Further development and application of new quenching techniques: Intensive Quenching; Controllable Delayed Quenching; Gas-Nozzle Quenching (with or without transient spraying of liquid Nitrogen).

• Development of the method for hardenability measurement of gas quenched steels (continuation of the research started at IWT – Bremen)

• Individual education and possibility of working on a doctoral thesis at the postgraduate doctoral study at the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, using English language, as well as postdoctoral research – provided the applicant has sources of relevant financial support.

• Organization of specialized courses and seminars.

Quenching Research Centre is part of the Department of Materials at the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, and is supported by other laboratories for: heat treatment and surface engineering, chemical analysis, micro-structural analysis, spectroscopy, mechanical properties testing, tribology, corrosion testing.

quenching research centre is open for international collaboration with interested companies and institutions – regardless of language, culture or continent.

Contact details

QUENCHING RESEARCH CENTRE Att. to Prof. dr. sc. Tomislav Filetin University of Zagreb Faculty of Mechanical Engineering and Naval Architecture Ivana Lucica Street 5 hr–10000 ZagrebCroatia

tel +385 1 6168 320fax +385 1 6157 109e-mail tfiletin@fsb.hrweb http://qrc.fsb.hr

StaffBožidar Liščić, Ph.D Mech. Eng. fasmTomislav Filetin, Ph.D. Mech. Eng. ceoBožidar Matijević, Ph.D. Mech. Eng. Darko Landek, Ph.D. Mech. Eng. Ivan Kumić, M. Mech. Eng.

EDUCATIONAL ACTIVITIES OF THE CENTRE

TEMPERATURE GRADIENT METHOD