ELEMET- MOCASTRO. Effect of grain size on A 3 temperatures in C-Mn and low alloyed steels - Gleeble tests and predictions. Period

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Arttu Mäkinen
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1 1 ELEMET- MOCASTRO Effect of grain size on A 3 temperatures in C-Mn and low alloyed steels - Gleeble tests and predictions Period

2 Diaarinumero Rahoituspäätöksen numero 1114/31/ /10 Projektin koko nimi Modelling of microstructure and propertiesof materials from casting to rolling proc Raportoitava kausi Tutkimusorganisaatio Y-tunnus Oulun yliopisto, Materiaalitekniikan laboratorio FI Projektin vastuullinen johtaja Puhelinnumero Pentti Karjalainen , Sähköpostiosoite Kustannustilityksen yhteyshenkilö Puhelinnumero Sari Arolaakso Sähköpostiosoite 2. KUSTANNUSTILITYS Aikaisemmin Kustannukset Kustannus- Rahoituspääraportoidut ajalta kertymä töksen kus- Tekesin hyväksymä HSK-kerroin 50 % kustannukset yhteensä tannusarvio Tekesin hyväksymä YK-kerroin 89 % Rahapalkat teholliselta työajalta(erittely liitteenä) Henkilösivukustannukset Yleiskustannukset Matkakustannukset Aineet ja tarvikkeet Koneiden ja laitteiden hankintamenot 0 Ostetut palvelut Muut kustannukset (eriteltävä) Uniresta, kokouskulut Kustannukset yhteensä

4 4 Compositions of tested steels (in wt-%)

5 Prior austenite grain sizes (Steels C and E) T = 900 C PAGD 20 µm T = 1200 C PAGD 100 µm T = 1400 C PAGD 1000 µm 5

6 6 Dilatometry (Gleeble 3800) Austenitizing temperature 1200 C, t = 30 s Cooling rates 0.1 C/s, 0.5 C/s, and 1.5 C/s Test specimen 10 mm

7 Phase trasnformation temperatures of (reheated at 1200 C) 7 * Phase transformation temperatures for bainite are in parentheses

8 8 Phase transformation temperatures (reheated at 900 C and 1400 C) T = 900 C T = 1400 C

9 9 JMatPro simulations reheated at 1200 C Results are consistent with the dilatometry (except Steel D) Variation max. 30 C (CR = 0.1 C/s)

10 10 Measured vs. calculated A 3 at 0.1 C/s, reheated at 1200 C Minz et al.: A 3 = %C %Mn %S N Ti %Nb d -1/2-0.11CR.

11 Measured vs. calculated A 3, austenitized at 1200 C and cooled at 0.1 C/s 11 S1: Gleeble S2: JMatPro S3: Mintz et al.

12 Measured vs. calculated A 3, austenitized at 1400 C and cooled at 0.1 C/s 12 S1: Gleeble S2: JMatPro S3: Mintz et al.

13 13 Effect of GS on phase transformation temperatures According to Minz et al. the GS has a small effect on A 3 temperature in the grain size range of 100 um um. Here Steels C and D. Note the different behaviour of Steel C compared to Steels A, B, and E. In Steel D both ferrite (A 3 ) and bainite transformations.

14 14 Steel D dilatometric curve RH 1200 C, CR 0.1 C/s

15 Effect of the change of GS on the change in A 3 S1: GS 20-100 um S2: GS 100-1000 um Mintz et al.

15 15 Effect of the change of GS on the change in A 3 S1: GS um S2: GS um Mintz et al.: 17 C for from 100 to 1000 um 31 C from 20 to 100 um 48 C for from 20 to 1000 um Observed even more than 100 C

16 Conclusions 16 According to Minz et al., the austenite GS has a small effect on A 3 temperature in the grain size range of 100 µm µm. However, the present results indicate that coarse grain size can decrease A 3 -temperature notably in some steels. The shift can be over 100 C between GS of 20 and 1000 um. The results of dilatometry tests are in consistence with the results of the JMatPro simulations in the case of relatively small GS (20 µm µm). In the large GS corresponding to continuously cast steels, there is sometimes a significant difference between the dilatometric data and the austenite transformation temperatures calculated by JMatPro. Thus, understanding and maybe a new prediction model is necessary in order to model the decomposition of austenite in the continuously cast steels accurately.

17 Tasks for the period Studying the effects of the prior austenite grain size and the precipitates on A 3 -temperature in different steels. Determination of the effect of alloying elements on the phase transformation temperature using JMatPro simulation software. Gleeble tests in order to compare and verify the simulation results (IDS and JMatPro). A presentation in ICPNS 13 conference

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