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1

Model carbonitride precipitation kinetics in Ti-microalloyed HSLA-type steel

Opiela M.

Archives of Materials Science and Engineering

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2016

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Vol. 77, nr 2

78--84

EN

Purpose: The work presents the model of precipitation kinetics of M(C,N) carbonitride in microalloyed steel, containing microaddition of Ti, under conditions of isothermal holding in austenite. The model has been based on the classical theory of nucleation, proposed by Kampmann and Wagner. Design/methodology/approach: In order to analyse precipitation kinetics of Ti(C,N) carbonitride in steel, containing 0.31% C, 0.0043% of N and 0.033% Ti, after austenitizing at the temperature of 1150°C with successive isothermal holding at the temperature of 900°C for 600 s, the CarbNit_kinet computer program has been used. The following physical data have been used for calculations: solubility products of carbides and nitrides, density of carbides and nitrides, parameters of mutual interaction of elements present in austenite, parameters of crystalline structure of carbides and nitrides, energies of interfacial boundaries between the precipitation and the matrix and diffusion coefficients of elements included in carbonitrides in austenite and ferrite. Findings: The calculated results contain data concerning: distribution of particle’s radius, nucleation rate as a function of time, particle’s number within the volume unit as a function of time, chemical composition of the matrix as a function of time and the per cent volume of the particles as a function of time. For given conditions, nucleation of Ti(C,N) carbonitrides in the investigated steel starts after 1 s and is finished after approximately 10 s. Conducted analysis revealed that the coagulation process of precipitations, in which the quantity of precipitations decreases in unit volume, occurs after more than 200 s. Whereas, distinct changes in the content of Ti, C and N dissolved in austenite was observed after the time of 8 s, subsequent to which the process of increase of precipitations begins. Research limitations/implications: Presented model of kinetics enables the analysis of precipitation process of only simple M(C,N) type carbonitrides. Calculation results strongly depend on physical parameters of the model, and in particular, on energy of interfacial boundaries. Practical implications: With the use of applied model, it’s possible to evaluate the content of precipitations of carbonitrides and distribution of their size, calculated on the basis of chemical constitution of steel and parameters of the manufacturing process. Originality/value: The model enables to distinguish specific stages of the precipitation process: nucleation, growth and coagulation. Despite the simplifications, the model makes it possible to predict changes occurring in the precipitation kinetics caused by changes in chemical composition.

2

Fatigue properties of the HSLA steel in high and ultra-high cycle region

Ulewicz R., Novy F., Mazur М., Szataniak P.

Production Engineering Archives

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2014

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Vol. 4, No. 3

18--21

EN

This work presents a study of the fatigue properties in the example of Swedish steel Hardox 400. Fatigue tests were carried out in the area of high and ultra-high cycle region. From the practical point of view the durability of some components in the automotive industry and similar technical applications such as special semitrailers ranges between 108 and 1010 cycles. But, only a few experimental results beyond 107 cycles are available now. The main objective of this research was to provide independent results to the company which uses Hardox steel in the construction of semitrailers. Selected mechanical and fatigue tests were carried out with the aim to study fatigue properties of Hardox steel. Based on the obtained experimental results the fatigue properties of this still not well recognized type of steel are discussed.

3

Effect of finish-rolling conditions on properties of HSLA Steel QStE460N

Shindler I., Cizek L., Rusz S., Janosec M., Legerski M., Krupala A.

Hutnik, Wiadomości Hutnicze

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2008

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Vol. 75, nr 8

511-513

EN

The research, carried out on the basis of the laboratory rolling, led to finding that the finish-rolling conditions in the Universal rolling mill (Tfinecke żelezarny a.s.) cannot in general influence the resulting structural and mechanical properties of the rolled product very much. The decrease in the finish rolling temperature from 960 °C to 810 °C resulted in the increase of the yield stress only by 5 %, while the corresponding roll forces rose by up to 45 %. A key role in rising of mechanical properties of the investigated HSLA QStE460N steel, under particular operational conditions, plays a low cooling speed of final rolled products, which is given by the absence of the laminar cooling.

PL

Badania walcowania w warunkach laboratoryjnych, pozwoliły wykazać, że warunki końcowego walcowania na walcarce uniwersalnej (w Tfinecke żelezarny a.s.) nie wpływają znacząco na końcowe właściwości strukturalne i mechaniczne walcowanych wyrobów. Spadek temperatury końcowej walcowania z 960 °C do 810 °C spowodował wzrost granicy plastyczności jedynie o 5 %, podczas gdy odpowiadające temu naciski walców wzrosły do 45 %. Kluczową rolę w polepszeniu właściwości mechanicznych badanej stali typu HSLA gatunku QStE460N, w ściśle określonych warunkach realizacji procesu walcowania, odgrywa niska szybkość chłodzenia wyrobów gotowych, która jest warunkowana brakiem chłodzenia laminarnego.

4

Development of the microalloyed constructional steels

Adamczyk J.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 14, nr 1-2

9--20

EN

Purpose: The aim of the paper is to present the development and the technical importance of the HSLA-type microalloyed constructional steels (High Strength Low Alloy) in selected industry branches. Design/methodology/approach: A mechanism of the interaction of Nb, Ti, V and B microadditions introduced into the steel on mechanical properties of selected metallurgical products with the fine-grained structure, forming under the properly selected hot-working conditions with the of (M-Nb, Ti, V; X-N,C) interstitial phases MX-type is discussed. Findings: The requirements concerning the metallurgical process, continuous casting of steel and the necessity of adjusting the hot-working conditions to the precipitation kinetics of the dispersive MX phases particles in austenite, in the controlled rolling or thermo-mechanical treatment processes are indicated. Research limitations/implications: The continuation of investigations concerning the thermo-mechanical rolling of automotive sheets with the multiphase structure of microalloyed steels is planned. Practical implications: The indicated data, coming also from the own research, are of practical use in relation to manufacturing the metallurgical products and machine elements of high strength and crack resistance, also at low temperatures. Originality/value: The results contribute to the development of rolling and forging technologies of the microalloyed steel (HSLA) elements produced using the energy-saving thermo-mechanical treatment methods.

5

Identyfikacja składników strukturalnych w strefie wpływu ciepła w stalach o dużej wytrzymałości

Mroczka K., Zielińska - Lipiec A., Ratuszek W., Tasak E.

Hutnik, Wiadomości Hutnicze

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2004

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Vol. 71, nr 7-8

396-399

PL

W pracy dokonano identyfikacji składników strukturalnych, wysp M-A, w strefie wpływu ciepła stali o dużej wytrzymałości. Obecnie w strukturze wyspy M-A są przyczyną zmian właściwości w tym szczególnie obniżają udarność. Opracowanie metodyki ujawniania wysp M-A umożliwiło zaplanowanie badań wyjaśniających ich wpływ na mechanizm pękania materiału.

EN

This work presents identyfication methods of structural components, M-A islands, in heat affected zone high strength steels. The islands included in the structure are the reason of properties decrease, especially impact strength. Study of disclosure M-A islands method makes possible examinations, witch explain the influence M-A islands on way of cracking the material.