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Thermodynamic Analysis of Precipitation Process of MX-type Phases in High Strength Low Alloy Steels

Opiela Marek

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 2

90--100

EN

The paper presents the results of thermodynamic analysis of precipitation process of MX-type interstitial phases in austenite. The subject of the investigation were two newly developed high strength low alloy microalloyed steels with similar concentration of C and N and with diversified amount of Nb, Ti and V microadditions. Thermodynamic analysis of the state of phase equilibrium of structural constituents, taking into consideration the austenite of investigated microalloyed steels, was mainly focused on analytic calculations of chemical composition of austenite and the content and chemical composition of potential MX-type interstitial phases (M – metal, X – metalloid) as a function of heating or cooling temperature. The analysis of precipitation process of complex carbonitrides in austenite under thermodynamic equilibrium conditions has allowed to define stoichiometric compositions of carbonitrides as a function of temperature along with determination of their volume portion. This study was based on the model proposed by Hillert and Staffanson, which was subsequently developed by Adrian. The results of performed investigation can be used to develop the appropriate parameters of thermomechanical treatment of metallurgical products from the tested HSLA-type steels.

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Elaboration of forging conditions on the basis of the precipitation analysis of MX-type phases in microalloyed steels

Opiela M., Grajcar A.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 4

427--435

EN

The paper presents analysis of the precipitation of MX-type (M—microalloying element, X—interstitial element) phases in austenite of constructional steels microalloyed with Nb, Ti, V and B, assigned for production of forged elements with the use of thermo-mechanical treatment. The calculations were conducted basing on the dependence of solubility product of MX-type phases in austenite as a function of temperature. The analysis was done on the basis of a simplified thermodynamic model for equilibrium conditions, assuming that individual MX-type phases are soluble in austenite. The solubility of TiN, TiC and NbC as a function of temperature as well as the simplified temperature sequence of precipitation of these phases have been determined. The effect of austenitizing temperature in a range from 900 to 1200 °C on grain size of prior austenite was investigated to verify the analysis. A grain growth corresponds well with a course of a precipitation process, though the limitation of the current model arising from a lack of consideration of complex carbonitrides and the kinetics of a precipitation process should be taken into account. The studies provide the basis for proper design of manufacturing process of thermo-mechanical treatment for high strength forged elements of microalloyed steels.

3

Analysis of the kinetics of precipitation of MX-type interstitial phases in microalloyed steels

Opiela M.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 47, nr 1

7--18

EN

Purpose: The paper presents analysis of the kinetics of precipitation of MX-type (M - metal, X - metalloid) interstitial phases in austenite of constructional steels microalloyed with Nb, Ti, V and B, assigned for production of forged machine elements with the use of thermo-mechanical treatment. Design/methodology/approach: The analysis was conducted basing on the dependence of solubility of MX-type phases in austenite as a function of temperature. The research of influence of austenitizing temperature in a temperature range from 900 to 1200°C on grain size of primary austenite has been used to verify the analysis. Findings: The kinetics of TiN, TiC and NbC precipitation as well as the temperature sequence of precipitation of these phases have been determined. The investigation of influence of austenitizing temperature on the grain size of primary austenite confirmed correctness of the analysis. Research limitations/implications: The analysis was done basing on the thermodynamic model proposed by Adrian, assuming that only individual, single MX phases are soluble in austenite. Practical implications: The studies provide the basis for proper design of manufacturing process of thermomechanical treatment of high strength forged machine parts obtained from microalloyed steels. Originality/value: The kinetics of precipitation of interstitial phases in newly elaborated microalloyed steels has been compiled.

4

Opracowanie warunków kucia na podstawie analizy kinetyki wydzielania się w austenicie faz międzywęzłowych typu MX

Opiela M.

Hutnik, Wiadomości Hutnicze

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2011

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Vol. 78, nr 8

646--649

PL

W pracy przeprowadzono analizę kinetyki wydzielania się w austenicie faz międzywęzłowych typu MX w nowo opracowanej stali mikrostopowej przeznaczonej do wytwarzania kutych elementów maszyn metodą obróbki cieplno-plastycznej. Weryfikację przeprowadzonej analizy stanowiły badania wpływu temperatury austenityzowania w zakresie od 900 do 1200 oC na wielkość ziaren austenitu pierwotnego. Na podstawie przeprowadzonej analizy opracowano temperaturowe warunki kucia badanej stali.

EN

In this work, the analysis of releasing kinetics of MX-type interstitial phases in the austenite in newly worked out microalloy steel, was made. The investigated steel is assigned for production of forged parts of machines by thermo-mechanical treatment. As a verification of the analysis, the effect of austenitizing temperature, at the range of 900÷1200 °C, on the grain size of primary austenite was investigated. The temperature conditions of forging process of investigated steel were determined on the basis of the carried out analysis.