Wyniki wyszukiwania - Biblioteka Nauki

1

Affect of decarburization times of bainitic ferrite laths on the microstructure in FE-CR-C steel

100%

Ławrynowicz Z.

Journal of Polish CIMAC

|

2011

|

tom Vol. 6, no 3

127-136

EN

The purpose of the present paper is to demonstrate how a thermodynamic method can be used for solving a problem of the decarburisation of bainite laths. The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated laths of ferrite into the retained austenite. This should in principle enable to examine the partitioning of carbon from supersaturated ferrite laths into adjacent austenite and the carbon content in retained austenite using analytical method. The obtained results illustrates that the estimated times are not capable of decarburising the sheaf of ferrite included thick laths of bainitic ferrite during the period of austempering. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides.

2

Ferrite Decarburization of High Silicon Spring Steel in Three Temperature Ranges

80%

Zhao F. , Zhang C. L. , Liu Y. Z.

Archives of Metallurgy and Materials

|

2016

|

tom Vol. 61, iss. 3

1715--1722

EN

Surface decarburization of high silicon spring steel in ambient air was studied. The experimental results confirmed the decarburized mechanism under AC1 temperature, in the temperature range of AC1-AC3 and AC3-G. Under AC1 temperature, pearlite spheroidization and surface decarburization are carried out simultaneously and pearlite spheroidization is reinforced. Considering the oxidation loss depth, the “true ferrite decarburized depth” at 850 °C (AC3-G) is still smaller than that at 760°C (AC1-AC3). That is because an “incubation period” must pass away before ferrite decarburization occurs in the temperature range of AC3-G, and the ferrite decarburized rate is limited to being equal to the partial decarburized rate.

3

Affect of cementite precipitation on the extend of bainite reaction in ADI

80%

Ławrynowicz Z.

|

2013

|

tom Vol. 8, no 3

31--36

EN

Presented paper demonstrates how the precipitation of cementite from ferrite or/and austenite in ADI may influence the extend of bainite reaction. Analytical calculations and experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides. In case of this microstructure, the product of austempering reaction in ductile iron is rather bainite than “ausferrite”. The results are discussed in the context of displacive mechanism of bainite transformation.

4

Effect of cementite precipitation on the extend of bainite transformation in fe-cr-c steel

80%

Ławrynowicz Z.

Advances in Materials Science

|

2011

|

tom Vol. 11, nr 3(29)

13-19

EN

Analytical calculations and experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation. A consequence of the precipi-tation of cementite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides.

5

Influence of cementite precipitation on the extent of bainite reaction in FE-CR-SI-C steel

80%

Ławrynowicz Z.

Journal of Polish CIMAC

|

2011

|

tom Vol. 6, no 3

137-144

EN

The paper presents an investigation of the extend of bainite reaction in the case of cementite precipitation. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. Carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and A3' phase boundaries suggests the likely mechanism of bainite reaction in Fe-Cr-Si-C steel is displacive rather than diffusional. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides.

6

Decarburisation Of Ferrite Laths During Bainite Reaction In Adi

80%

Ławrynowicz Z. , Dymski S.

Journal of Polish CIMAC

|

2009

|

tom Vol. 4, no 3

65-72

EN

The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated laths of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to a larger extent and that the resulting microstructure is not an ausferrite, but is a mixture of bainitic ferrite, retained austenite and carbides. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

7

Carbon diffusion during bainite reaction in austempered ductile iron

80%

Ławrynowicz Z. , Dymski S.

Advances in Materials Science

|

2008

|

tom Vol. 8, nr 1(15)

75-87

EN

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated subunits of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransforrned austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

8

Analysis of carbon diffusion during bainite transformation in ADI

51%

Ławrynowicz Z. , Dymski S.

|

2007

|

tom Vol. 7, iss. 3

87-92

EN

The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. The analytical model estimates the decarburisation time of the sub-units of supersaturated bainitic ferrite. The purpose of the present paper is to demonstrate how a thermodynamic method can be used for solving a problem of the decarburisation of bainite subunits and carbon diffusion distances in the matrix of ADI. This should in principle enable to examine the partitioning of carbon from supersaturated ferrite plates into adjacent austenite and the carbon content in retained austenite using analytical method. The diffusion coefficient of carbon in austenite is very sensitive to the carbon concentration and this has to be taken into account in treating the large concentration gradients that develop in the austenite. The results are discussed in the context of displacive mechanism of bainite transformation. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. The necessary carbon diffusion distance in austenite also illustrates that the estimated time is not capable of decarburising the ferrite subunits during the period of austempering. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides.

9

Influence of the base metal grain size and heat input on decarburization in single pass SAW and multi pass SMAW welded joints of dissimilar ferritic steels

51%

Nimko M. O. , Skulskyi V. Y.

Journal of Achievements in Materials and Manufacturing Engineering

|

2023

|

tom Vol. 119, nr 1

14--26

EN

Purpose: This paper aims to assess a separate influence of heat input and base metal grain size on microstructural evolution in the weld adjacent zone of bainitic steels with 1.5…2.0% Cr, welded or overlayed with consumables with 9% Cr after post-weld heat treatment. Design/methodology/approach: Analysis of the width of decarburised layer on microphotographs of welded or overlayed specimens after tempering at 750°C. Specimens were made by using different welding approaches: single-pass welding, multi-pass welding and overlaying. Findings: It is shown that with an increase of the heat input energy, the width of the resulting decarbonised layer decreases linearly; the increase of the base metal grain size leads to a decrease in the layer width after tempering at 750°C. The microhardness testing showed the average hardness in the decarburised layer of 15Kh2M2FBS steel was 161 HV0.1 (minimum – 154 HV0.1), while the average hardness in the rest of the heat-affected zone was 192 HV0.1. Research limitations/implications: Future research may include comparing the creep rupture strength of the weldments made with different welding parameters or base metal grain size to assess the influence of these factors on creep rupture strength. Practical implications: Results permit to achieve minimisation of the rate of carbon diffusion in the weld-adjacent area of the heat-affected zone by means of variation of welded parameters and base metal grain size. Originality/value: An influence of high-diffusivity paths (grain boundaries) on carbon diffusion in the heat-affected zone of dissimilar weldments was confirmed experimentally; the correlation between base metal grain size/welding parameters and the rate of the diffusion during high temperature exposure was found.

10

Modelling of carbon diffusion and ferritic phase transformations in an unalloyed hypoeutectoid steel

41%

Wolff M. , Acht C. , Bochm M. , Meier S.

Archives of Mechanics

|

2007

|

tom Vol. 59, nr 4-5

435-466

EN

During the important industrial process of case hardening, phase transformations in a steel workpiece are essentially influenced by the (non-homogeneous) carbon distribution (near the surface). Moreover, the temperature course is of great importance. We develop a mathematical model of case hardening which takes diffusion of carbon in austenite, heat conduction and possible phase transformations into account. In this work, mechanical behaviour (thermo-elasticity, classical plasticity and transformation-induced plasticity) is not included in the model. As a result we obtain an initial-boundary-value problem for a coupled system of two parabolic partial and several ordinary differential equations. Finally, we present some numerical simulations.