27. – 29.11.2012, Jihlava, Česká republika QTSTEEL – SOFTWARE FOR COMPUTER SIMULATION OF HEAT TREATMENT RESPONSE OF CARBON AND ALLOY STEELS Pavel Šimeček a , Ron Scott b a ITA Ltd., Martinská 6,709 00 Ostrava, Czech Republic, [email protected]b METALTECH Ltd., Consett, DH8 9HU, United Kingdom, [email protected]ABSTRACT This paper introduces the functionality of a new version of the software QTSteel 3.2, the development of which was completed in October 2012. The new version has many improvements both in the computation of cooling curves as well as in the field of metallurgy. The 2D FEM temperature module has been extended to non-symmetrical cooling of cylinders and rings. The temperature of the air during cooling of the inner side of the tube can be dependent on the actual temperature of the inner surface. When a part is cooled in a quenchant the temperature calculation can take into account the temperature of the cooling media. A new feature available in the software is the thermal balance calculation, which ensures the time dependence of heating power and energy during the cooling process. The metallurgical modules for predicting CCT diagrams were tuned in order to be more representative of industrial heat treatment procedures especially for chromium, nickel and molybdenum alloyed steels. Within the development of the new version, modules for calculating as quenched hardness and for the prediction of as tempered mechanical properties were also tuned. Predicted values have been compared with measured data, both from process measurements and available literature. The results of some of this comparative work have been presented in the paper. 1. QTSTEEL – INTRODUCTION QTSteel software has been developed to predict the heat treatment response of through hardened, carbon and alloy steels in terms of microstructure and mechanical properties. The software covers the heat treatment simulations of carbon and alloy engineering steels with carbon from 0.06 % to 0.6 % and with the total sum of alloying additions up to 10 %. It is designed to assist mechanical engineers, metallurgists and designers who need to know what mechanical properties can be achieved by various combinations of section size, steel composition and heat treatment procedures. The software allows the selection of appropriate steel and the optimization of the heat treatment for new and existing components. It can therefore play an important part in the economic analysis of manufacture routes and the selection of the lowest cost steel. The first version of the QTSteel was released in 1995 then still under the brand Metallurgist. These first DOS versions were developed primarily to allow the prediction of the mechanical properties of hot rolled steel products such as wire rods, bars, plates and strips. Later the software was rewritten for the Windows OS and its capabilities were extended to general heat treatment processes. Since 1999 after the addition of the FEM temperature module the
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27. – 29.11.2012, Jihlava, Česká republika
QTSTEEL – SOFTWARE FOR COMPUTER SIMULATION OF HEAT TREATMENT RESPONSE OF CARBON AND ALLOY STEELS Pavel Šimečeka, Ron Scottb aITA Ltd., Martinská 6,709 00 Ostrava, Czech Republic, [email protected] bMETALTECH Ltd., Consett, DH8 9HU, United Kingdom, [email protected] ABSTRACT This paper introduces the functionality of a new version of the software QTSteel 3.2, the development of which was completed in October 2012. The new version has many improvements both in the computation of cooling curves as well as in the field of metallurgy. The 2D FEM temperature module has been extended to non-symmetrical cooling of cylinders and rings. The temperature of the air during cooling of the inner side of the tube can be dependent on the actual temperature of the inner surface. When a part is cooled in a quenchant the temperature calculation can take into account the temperature of the cooling media. A new feature available in the software is the thermal balance calculation, which ensures the time dependence of heating power and energy during the cooling process. The metallurgical modules for predicting CCT diagrams were tuned in order to be more representative of industrial heat treatment procedures especially for chromium, nickel and molybdenum alloyed steels. Within the development of the new version, modules for calculating as quenched hardness and for the prediction of as tempered mechanical properties were also tuned. Predicted values have been compared with measured data, both from process measurements and available literature. The results of some of this comparative work have been presented in the paper. 1. QTSTEEL – INTRODUCTION QTSteel software has been developed to predict the heat treatment response of through hardened, carbon and alloy steels in terms of microstructure and mechanical properties. The software covers the heat treatment simulations of carbon and alloy engineering steels with carbon from 0.06 % to 0.6 % and with the total sum of alloying additions up to 10 %. It is designed to assist mechanical engineers, metallurgists and designers who need to know what mechanical properties can be achieved by various combinations of section size, steel composition and heat treatment procedures. The software allows the selection of appropriate steel and the optimization of the heat treatment for new and existing components. It can therefore play an important part in the economic analysis of manufacture routes and the selection of the lowest cost steel.
The first version of the QTSteel was released in 1995 then still under the brand Metallurgist. These first DOS versions were developed primarily to allow the prediction of the mechanical properties of hot rolled steel products such as wire rods, bars, plates and strips. Later the software was rewritten for the Windows OS and its capabilities were extended to general heat treatment processes. Since 1999 after the addition of the FEM temperature module the
27. – 29.11.2012, Jihlava, Česká republika
software was renamed TTSteel. The latest stage in the evolution of the QTSteel development started in 2009 and with support from Metaltech Ltd. The software then acquired its current name and obtained highly qualified metallurgical support based on their long term experience in the heat treatment of steels. 2. QTSTEEL - BASIC FUNCTIONALITY QTSteel has a dynamic and user friendly interface. All the basic functions of the QTSteel can be accessed in the main window. These key areas guide the user to specify inputs (chemical composition, etc), which when combined with the temperature curves, will allow the software to make metallurgical predictions and to post-process the results. 2.1 Specification of steel properties The first step is to specify the chemical composition of the heat treated steel along with other properties such as the initial austenite grain size, the austenitizing temperature and the soak time. Using this information the corresponding CCT diagram is calculated and utilized for the metallurgical processing. An additional important facility is the ability to make modifications to the predicted CCT diagram. This allows a user defined CCT diagram to be used, if the users has a specific CCT associated and validated for the steel being simulated.
2.2 FEM temperature calculations and specification of cooling curves QTSteel contains a 2D FEM module that enables the calculation of temperatures for special plane and axi-symmetric bodies (rectangular and rounded bars, tubes, cylinders and rings)
Fig.1. Specification of steel properties with an example of a predicted CCT diagram
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with the cooling conditions changing in time and in position on the surface of the selected body. Specialist knowledge of FEM is not required, as QTSteel has been programmed to fully automate the FEM preprocessing. The temperature calculations will only take a few moments.
The cooling process consists of a time sequence of cooling conditions. Each cooling condition is specified by duration (in seconds), a number of time steps and by the type of cooling media. QTSteel has a built-in database containing the heat transfer coefficients for basic types of cooling media (water, oils, polymers etc). If the heat transfer coefficients are known for a particular facility or quenchant these can be added to the database.
There are two options available to specify the cooling curves: • The cooling curves are computed by the FEM temperature module in specified points of
cross-section on the component. • The cooling curves are entered manually by keyboard
The cooling curve typically displays the process of the primary quenching but it can also accommodate reheating sequences. It incorporates the model of self-tempering: that is a characteristic during the heat treatment of large sections. Conventional tempering after quenching can be added by the linking of the cooling curve with specific tempering parameters such as the time and temperature or selected more a complex tempering regime.
Fig.2. Specification of the cooling process for heat treatment of a tube with running 2D FEM temperature module shown in separate window
27. – 29.11.2012, Jihlava, Česká republika
2.3 The prediction of steel properties after heat treatment QTSteel has the capability to predict the CCT diagram of a specified steel, the microstructure and final mechanical properties (hardness, yield stress and ultimate tensile strength) after quenching and tempering process.
Fig.4. Specification of single cooling curves
Fig.3. Specification of cooling conditions
27. – 29.11.2012, Jihlava, Česká republika
There are two types of metallurgical predictions available in the QTSteel: • Metallurgical predictions for one selected single cooling curve, • Metallurgical predictions across a complete 2D-body or in specified dimension below
surface.
The full process of the metallurgical calculation from the initiating the cooling curve can be accomplished within a few seconds.
2.4 New functionality available in the QTSteel 3.2 The latest version of QTSteel (version 3.2) was released in October 2012. Along with retuning the metallurgical module the new version offers the following updated functionality: • Non-symmetrical cooling of cylinders and rings, • Enhanced models of the heat transfer due to the free and forced convection were
implemented, • FEM meshes of all the 2D bodies are finer to refine calculation of temperatures, • The cooling medium temperature can be specified as dependent on the surface
temperature or it can be time dependent where the medium is heated or cooled with consideration given to the heat energy transferred through surface of the body,
• Reporting in HTML and PDF file formats, • The thermal balance of the heat treatment process is displayed.
Fig.5. Metallurgical prediction for the cooling curve 33.5mm below surface of a rounded bar
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Fig.7. New design of the thermal balance window with predicted time dependence of cooling media temperature
Fig.6. Metallurgical prediction for non-symmetrically cooled cylinder (Jominy test)
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3. QTSTEEL – SPECIAL EXTENSIONS If the geometry of a steel section is complex then tailor made extensions can be developed to accommodate these section sizes. An example would be the THCool software which was built to illustrate the heat treatment of special profiles which include rail tracks and mining reinforcement sections.
4. QTSTEEL - VERIFICATION EXAMPLES 4.1 Heat treatment of bars To verify QT Steel 23 bars AISI 4130 of varying diameters (from 80 - 380mm) where water quenched and tempered at 650 – 700 °C (hold time of 60 – 680 min) is shown below.
C MN SI CR NI MO CU 0,32 0,57 0,27 1,03 0,15 0,2 0,14
90
95
100
105
110
115
90 95 100 105 110 115
UTS pred
icted
UTS measured
65
70
75
80
85
90
95
65 70 75 80 85 90 95
YS predicted
YS measured
Fig.9. Comparison of measured and predicted yield stress and ultimate tensile strength
Fig.8. THCool - special QTSteel extension for heat treatment of special profiles
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4.2 Heat Treatment of tubes Two hot rolled seamless tubes where also used to verify the heat treatment calculations with the software:
5. QTSTEEL - CONCLUSION The latest version of QTSteel software has demonstrated that this off-line metallurgical software represents an important metallurgical simulation tool for technologists and engineers dealing with heat treatment technologies.
QTSteel software can also be used for educational purposes at technical universities; this fact is confirmed by the number of licenses sold. To date more than 30 licenses have been sold within industry worldwide and 25 licenses to technical universities within Europe.
As part of the continuous development of the QTSteel we have always kept in close contact with our existing customers, asking for regular feedback when convenient. We are extremely pleased to report that we have always had extremely positive feedback about QT Steel and its capabilities.
In case you need more detailed information contact us, please, at www.ita-tech.cz or www.msl-ltd.com. ----------------------------------------------------------------------------------------------------------------- This paper was supported from budget of the Technology Agency of the Czech Republic within the programme ALFA - project TA01010838.
Tab.2. Verification for heat treated tube 244.5/10mm normalized and quenched by water spray and tempered 60min at 520 °C.
Tab.1. Verification for heat treated tubes 292/34mm normalized and quenched by water spray and tempered 30min at 680°C.
