The paper is devoted to the comparison of the results in the frame of solidus and liquidus temperatures obtained by thermo analytical methods with the generally used empirically based formulas and thermo dynamical Computherm software. The series of thermal analysis measurements of high temperature phase transformations of real steel grade (S34MnV) under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram Multi High Temperature Calorimeter (MHTC)) were carried out. Two thermo analytical methods were used (DSC and Direct Thermal Analysis). The different weight of samples was used (2,6 g; 23 g). The liquidus and solidus temperatures for close to equilibrium conditions during heating (DSC: 1 °C/min; 2 °C/min) and during cooling (Direct Thermal Analysis: 1 °C/min) were determined and compared. Then, the discussion on the different values obtained by experiments and empirically based calculation is realised

B. Smetana

J. Dobrovská

K. Gryc

K. Janiszewski

K. Michalek

L. Socha

M. Tkadlečková

M. Žaludová

P. Machovčák

English

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295METALURGIJA 53 (2014) 3, 295-298K. GRYC, B. SMETANA, M. TKADLEČKOVÁ, M. ŽALUDOVÁ, K. MICHALEK, L. SOCHA, J. DOBROVSKÁ, K. JANISZEWSKI, P. MACHOVČÁKDETERMINATION OF SOLIDUS AND LIQUIDUS TEMPERATURES FOR S34MnV STEEL GRADE BY THERMAL ANALYSIS AND CALCULATIONSReceived – Prispjelo: 2013-06-21Accepted – Prihvaćeno: 2013-12-28Original Scientific Paper – Izvorni znanstveni radISSN 0543-5846METABK 53(3) 295-298 (2014)UDC – UDK 669.18:621.78.083:536.5=111K. Gryc, B. Smetana, M. Tkadlečková, M. Žaludová, K. Michalek, L. Socha, J. Dobrovská, VŠB-TU Ostrava, Faculty of Metalurgy and Ma-terials Engineering, Ostrava, Czech RepublicK. Janiszewski, Silesian University of Technology, Department of Met-allurgy, Katowice, PolandP. Machovčák, Vítkovice Heavy Machinery, a.s., Ostrava, Czech Re-publicThe paper is devoted to the comparison of the results in the frame of solidus and liquidus temperatures obtained by thermo analytical methods with the generally used empirically based formulas and thermo dynamical Computherm software. The series of thermal analysis measurements of high temperature phase transformations of real steel grade (S34MnV) under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram Multi High Tem-perature Calorimeter (MHTC)) were carried out. Two thermo analytical methods were used (DSC and Direct Thermal Analysis). The different weight of samples was used (2,6 g; 23 g). The liquidus and solidus temperatures for close to equilibrium conditions during heating (DSC: 1 °C/min; 2 °C/min) and during cooling (Direct Thermal Analysis: 1 °C/min) were determined and compared. Then, the discussion on the different values obtained by experiments and empirically based calculation is realised.Key words: steel, thermal analysis, empirical formula, liquidus temperature, solidus temperatureINTRODUCTIONThe methods of study of metallurgical processes are also based on knowledge of thermodynamic properties of materials occurring in a given technology nodes. Knowledge of solidus and liquidus temperatures of the studied steels is one of the most important factors - es-pecially in dealing with the processes involved in the casting and solidification. These temperatures are criti-cal parameters for proper adjustment of models (physi-cal or numerical) or in the final stage of applied research of the real process. It is significantly affecting the final quality of the as-cast steel (billets or ingots).Therefore, this paper is devoted to discussion of find-ings obtained during the utilization of dynamic thermal analysis methods [1, 2] to identify the solidus and liquidus temperatures of selected steel grade. Generally, it is not so easy to identify the phase transformations occurring in such multicomponent systems like steels [3-5].THERMAL ANALYSIS METHODS AND STEEL SAMPLESNew Laboratory for Modelling of Processes in the Liquid and Solid Phases within the project RMSTC was formed at the Faculty of Metallurgy and Materials En-gineering at the VŠB-Technical University of Ostrava in Czech Republic.This Laboratory has also acquired new equipment for high-temperature thermal analysis – Netzsch STA 449 F3 Jupiter. The conditions for initiation of intensive research activities in the field of dynamic thermal anal-ysis methods for steel are based on years of experience of team members with the issue of laboratory studies of metallurgical processes and the ability to use other equipment of this type - Setaram MHTC.This paper discusses methods and results of thermal analysis of samples (Table 1). Two methods for dynam-ic thermal analysis were used to measure the solidus (TS) and liquidus (TL) temperatures:•  Differential Scanning Calorimetry (DSC) – Seta-ram MHTC,•  Direct Thermal Analysis - Netzsch STA 449 F3 Ju-piter.The principles of both methods are described for ex-ample in [5]. Results of previous measurements realised by our team you can find for example in [6] where the correct setting of used methodology is presented on other steel grade and also comparison of results realised by Netzsch STA 449 F3 Jupiter with next by our team used method DTA (SETARAM SETSYS 18TM) is realised.Results from thermo analytical methodsThe first method (DSC) was used to determine the TS and TL close to equilibrium by the heating of samples (1 °C/min; 2 °C/min) of studied S34MnV steel grade. 296  METALURGIJA 53 (2014) 3, 295-298K. GRYC et al.: DETERMINATION OF SOLIDUS AND LIQUIDUS TEMPERATURES FOR S34MnV STEEL GRADE...These values will be compared also with results of em-pirical formulas based calculations in the next chapter of this paper. The second thermo analytical method, Direct Ther-mal Analysis, was used to acquire data close to real con-ditions. Based on numerical simulation of 90 tons heavy forging ingot the cooling rate 1 °C/min was set during measurement.Figure 1 presents comparison of liquidus (TL) and solidus (TS) temperatures (marks) acquired for real plant conditions (cooling) with close to equilibrium tempera-tures (lines).It is evident, see Figure 1, that TL for close to equi-librium conditions (1 501 °C) is about 19 °C higher than the TL obtained for the controlled cooling conditions (1 482 °C).Further, the value of TS for close to equilibrium con-ditions (1 437 °C) is about 16 °C lower than the TS for cooling regime (1 453 °C). So, during cooling (close to real plant conditions) the two-phase region between TL and TS is narrowed from 64 to 29 °C.It is important to take into account these differences between close to equilibrium temperatures and real situ-ation for example in solidifying ingot. It should help us to better predict the real processes occurring in steel by numerical modelling and/or technology optimisation.COMPARISON OF DSC ANALYSIS RESULTS WITH CALCULATIONSAs mentioned, close to equilibrium TL and TS ac-quired by differential scanning calorimetry are suitable to compare with generally used and empirically based formulas (A-K) defined in [6]. Also, a calculation real-ised by Computherm thermo dynamical software (SW) was applied for this comparison [6].Computherm SW is able to calculate both studied temperatures. It is possible to choose two microsegre-gation models (Scheil or Lever). In the case of Lever, the Lever rule has been applied, corresponding to a complete mixing of the solute in the solid (i.e., a very Table 1  Chemical composition of S34MnV steel grade, dimensions of used samples for each methodChemical composition Sample dimensions for used methodsElement Content / wt.% Sample for method: Setaram MHTC STA 449 F3 JupiterC 0,33 – 0,39Dimensions:Mn 1,20 – 1,50Si max. 0,30P max. 0,020S max. 0,020V max. 0,1217 mm Ø5 mm Ø14 mm 20 mm Figure 1  Results of realised thermal analysis measurements for close to equilibrium temperatures and for non-equilibrium conditions – coolinggood diffusion in the solid). On the other hand, the Scheil model corresponds to a no-diffusion model for the solid phase (both models consider a complete mix-ing of an infinite diffusion in the liquid). The Back-Dif-fusion model allows for some diffusion in the solid and corresponds thus to the situation in between the Lever rule and Scheil. When the Back-Diffusion model is used, the average cooling rate (corresponding to the representative cooling rate of the casting to be mod-elled) should be specified in order to determine the amount of back diffusion. For iron and carbon steel, the Lever rule is still recommended.The Computherm Fe-rich-alloy database has defined the limitations of the chemical composition and recom-mended composition limits for them. The Lever rule was selected (without the Pb, Sn, As, Zr, Bi, Ca, Sb, B, N contents) for determining TL and/or TS in the frame of this paper.Based on above described thermo-analytical method (DSC) and empirical formulas (A-J) and Computherm 297METALURGIJA 53 (2014) 3, 295-298K. GRYC et al.: DETERMINATION OF SOLIDUS AND LIQUIDUS TEMPERATURES FOR S34MnV STEEL GRADE...SW [6] TL was summarized for studied S34MnV steel grade – Table 2. As standard for comparison with theoretical values of TL (by calculation) was used the liquidus temperature acquired by DSC experiments realised under conditions close to equilibrium. These differences are quantified in column “Deviation”. It is evident, see Table 2, that the best agreement (zero deviation) with measured TL was reached when the formula (I) was used:TL = 1 536 – K·(%C) – 8·(%Si) – 5·(%Mn) – 30·(%P) – 25·(%S) – 1,7·(%Al) – 5·(%Cu) – 1,5·(%Cr) – 4·(%Ni) – 2·(%V) – 1·(%W) – 1,7·(%Co) – 12,8·(%Zr) – 7·(%Nb) – 3·(%Ta) – 14·(%Ti) – 14·(%As) – 10·(%Sn) (1)where the K coefficient varies with respect to differ-ent contents of carbon: C ≤ 2 %;  K = 65 C ∈ (0,2; 0,5⟩  %; K = 88Vice versa, the biggest deviation (-11 °C) against measured value of TL was identified when the formula (C) was applied:TL = 1 537,7 – 100,3·(%C) + 22,1·(%C)2 – 13,55·(%Si) + 0,64·(%Si)2 – 5,82·(%Mn) – 0,3·(%Mn)2 – 4,18·(%Ni) – 0,01·(%Ni)2 – 4,2·(%Cu) – 1,59·(%Cr) + 0,007·(%Cr)2 – 3·(%Mo)  (2)Table 2  Liquidus temperatures for S34MnV steel grade determined by the formulas, Computherm and DSC experimentsTL based on TL / °C Deviation / °CA 1 499 -2B 1 495 -6C 1 490 -11D 1 492 -9E 1 499 -2F 1 496 -5G 1 504 3H 1 493 -8I 1 501 0J 1 498 -3SW 1 497 -4DSC 1 501 0In the previous presented study [6], there were com-pared formulas and SW results with experimental ones for 5 steel grades with different chemical composition. Based on this work can be stated that it is very hard to identify best fit equation or thermo dynamical SW before experimental check-up. Above mentioned best fitting formula (9) for discussed S34MnV steel grade is not au-tomatically the best one for other steel grades [6].The TL predicted by Computherm SW were gener-ally in relatively good agreement with measurements, not only for S34MnV steel grade (-4 °C).Experimentally acquired TS was compared with only one empirical formula (K) and with Computherm SW [6] – see Table 3.Table 3  Solidus temperatures for S34MnV steel grade determined by the formula, Computherm and DSC experimentsTS based on TS / °C Deviation / °CK 1 425 -12SW 1 429 -8DSC 1 437 0It is evident, see Table 3, that calculated TS differ from experimentally measured TS much more than when TL values were compared. Determination of TS not only for S34MnV steel grade is very difficult.CONCLUSIONThe comparison of the results in the frame of solidus and liquidus temperatures (S34MnV steel grade) ob-tained by thermo analytical methods with the generally used empirically based formulas and thermo dynamical Computherm SW was aim of this paper. Two thermo analytical methods were used. Direct thermal analysis experiments were realised to simulate real cooling process. Moreover, DSC method was used to determine TL and TS values for close to equilibrium conditions. Based on a comparison of above mentioned results can be stated:1.  TL and TS for close to equilibrium conditions (1 501 °C; 1 437 °C) differ from such values (1 482 °C; 1 453 °C) for simulation of solidifying of heavy forging ingot (cooling).2.  The two phase region (mushy zone) between TL and TS is narrowed radically (from 64 to 29 °C).It is important to take into account these differences between close to equilibrium temperatures and real situ-ation for example in solidifying ingot. It should help us to better predict the real processes occurring in steel by numerical modelling and/or technology optimisation.Close to equilibrium TL and TS acquired by DSC meth-od were then compared with calculations based on empiri-cally based formulas and thermo dynamical Computherm software:3.  Calculated values of TL/TS differ from experimen-tally obtained results.4.  It is very hard to identify best fit equation or ther-mo dynamical SW before experimental check-up of TL/TS.It is important to verify the theoretical values of the crucial parameters such as the liquidus and solidus tem-peratures by experimental measurements for optimising the metallurgical process.AcknowledgementsThis paper was created in the frame of projects: No. CZ.1.05/2.1.00/01.0040 “Regional Materials Sci-298  METALURGIJA 53 (2014) 3, 295-298K. GRYC et al.: DETERMINATION OF SOLIDUS AND LIQUIDUS TEMPERATURES FOR S34MnV STEEL GRADE...ence and Technology Centre” within the frame of the operation programme “Research and Development for Innovations” financed by the Structural Funds and from the state budget of the Czech Republic;TIP programme, project No. FR-TI3/243 financed by the Ministry of Industry and Trade of the Czech Re-public;No. P107/11/1566 of the Czech Science Founda-tion;SGS (student’s university project) projects: No. SP2013/64, SP2013/62.REFERENCES[1] J. Miettinen, Metallurgical and Materials Transactions B, 28B (1997), 281-297.[2] W. J. Boettinger, U. R. Kattner, Metallurgical and Mate-rials Transaction A, 33A (2002), 1779-1794.[3] D. A. Porter et al. Phase Transformations in Metals and Alloys, CRC Press, 3rd ed., Boca Raton, 2009.[4] J. C. Zhao, Methods for Phase Diagram Determination, El-sevier, Oxford, 2007.[5] P. K. Gallagher, Handbook of Thermal Analysis and Calo-rimetry: Principles and Practice, Elsevier, 2nd ed., Oxfort, 2003.[6] K. Gryc, B. Smetana, M. Žaludová et al., Metalurgija, 52 (2013) 4, 445-448.[7] K. Gryc, B. Smetana, M. Žaludová et al., Materiali in Teh-nologije, 47 (2013) 5, 99-105.Note:  The responsible translator for English language is Boris Škandera, Czech Republic

Determination of solidus and liquidus temperatures for S34MnV steel grade by thermal analysis and calculations

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The paper is devoted to the comparison of the results in the frame of solidus and liquidus temperatures obtained by
thermo analytical methods with the generally used empirically based formulas and thermo dynamical Computherm
software. The series of thermal analysis measurements of high temperature phase transformations of real steel
grade (S34MnV) under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram Multi High Temperature
Calorimeter (MHTC)) were carried out. Two thermo analytical methods were used (DSC and Direct Thermal
Analysis). The different weight of samples was used (2,6 g; 23 g). The liquidus and solidus temperatures for close to
equilibrium conditions during heating (DSC: 1 °C/min; 2 °C/min) and during cooling (Direct Thermal Analysis: 1 °C/
min) were determined and compared. Then, the discussion on the different values obtained by experiments and
empirically based calculation is realised.Web of Science53329829

Determination of solidus and liquidus temperatures for S34MnV steel grade by thermal analysis and calculations

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