Wyniki wyszukiwania - BazTech

1

The Effect of Heat Treatment on Microstructure and Mechanical Properties of Cast Bainitic Steel Used for Frogs in Railway Crossovers

Parzych S.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 4

2147--2151

EN

This work deals with the effect of heat treatment on a microstructure and mechanical properties of a selected cast steel assigned as a material used for frogs in railway crossovers. Materials used nowadays in the railway industry for frogs e.g. Hadfield cast steel (GX120Mn13) or wrougth pearlitic steel (eg. R260) do not fulfil all exploitation requirements indicated in the UIC (International Union of Railways) Decision No. 1692/96 in terms of train speed that should be reached on railways. One of the possible solution is using a cast steel with bainitic or bainitic-martensitic microstructure that allows to gain high strength properties the ultimate tensile strength (UTS) of 1400 MPa, the tensile yield strength (TYS) of 900 MPa and the hardness of up to 400 BHN. The tested material is considered as an alternative to Hadfield cast steel that is currently used for railway frogs. Results of an experimental analysis of the effect of conducted heat treatment on a microstructure, the volume fraction of retained austenite and mechanical properties of bainitic steel, are shown in this paper. It was found that, the heat treatment leads to a stabilization of retained austenite in grain boundaries area of the primary austenite. Additionally, the heat treatment according to the variant #3 results with an almost 3-times higher impact toughness to that exhibited by material subjected to the other treatments.

2

The influence of heat treatment on microstructure and tribological properties of resistance butt welds made of a cast bainitic steel

Parzych S., Krawczyk J.

Archives of Metallurgy and Materials

|

2012

|

Vol. 57, iss. 1

261-264

EN

This work deals with the influence of heat treatment on microstructure and tribological properties of specimen cast assigned as a material used for frogs in railway crossovers. Materials used nowadays in the railway industry for frogs: Hadfield cast steel (GX120Mn13) and forged pearlitic steel (R260) do not fulfil strict conditions of exploitation and speed that should be reached on railway as indicated in the UIC Decision No. 1692/96. One of the possible solutions is using cast steel with bainitic or bainitic-martensitic microstructure, which allows to gain high strength properties (Rm = 1400 MPa, Rp0,2 = 900 MPa and up to 400 BHN). The test material is an alternative to railway frogs made of Hadfield cast steel. It remains problematic to determine the properties at the weld of the frog with the rail, which can also have bainitic microstructure. To ensure similar wear in both the resistance joint and the base material the resistance butt joint should have almost the same mechanical and tribological properties as the base metal. The main objective of the present work is to study the influence of heat treatment on microstructure and tribological properties of resistance welds made of bainitic cast steel used for frogs in railway crossovers.

PL

Niniejsza praca dotyczy wpływu obróbki cieplnej na mikrostrukturę i własności tribologiczne odlewu próbnego przeznaczonego jako materiałna krzyżownice kolejowe. Dotychczasowe materiały stosowane w kolejnictwie na krzyżownice: staliwo Hadfielda (GX120Mn13) oraz kuta stal perlityczna (R260) nie spełniają rygorystycznych warunków eksploatacji i prędkości osiąganych na nawierzchniach kolejowych zawartych w Decyzji UIC nr 1692/96. Jednym z rozwiązań jest zastosowanie materiałów o mikrostrukturze bainitycznej lub bainityczno-martenzytycznej, co umożliwia uzyskanie wysokich własności wytrzymałościowych (Rm =1400 MPa, Rp0,2 =900 MPa, twardości do 400 HBW). Badany materiałjest alternatywą dla krzyżownic kolejowych ze staliwa Hadfielda. Problematyczne pozostaje określenie również własności w miejscu połączenia krzyżownicy z szyną, która również może mieć mikrostrukturę bainityczną. Wykonane złącze zgrzewane powinno wykazywać jak najbliższe własności (mechaniczne, tribologiczne itp.) do materiału rodzimego gdyż wówczas zapewniają one równomierne zużywanie się zarówno w obszarze złącza jak i samego materiału rodzimego. W pracy określono wpływ obróbki cieplnej na mikrostrukturę i własności tribologiczne zgrzein wykonanych ze staliwa bainitycznego stosowanego na krzyżownice do rozjazdów kolejowych.

3

The microstructure and properties of the bainitic cast steel for scissors crossovers

Pacyna J., Bała P., Dobosz S., Kokosza A., Kąc S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2010

|

Vol. 39, nr 1

19-26

EN

Purpose: The main purpose of the hereby study was the description of microstructure and properties of the new low-carbon Mn-Cr-Mo-V-Ni bainitic cast steel developed in the AGH Laboratory of Phase Transformations for cast mono-blocks of scissors crossovers. Investigations comprise material in as-cast state and after various variants of normalization as well as normalization and high tempering. Design/methodology/approach: Analyses of microstructure, strength properties, impact toughness and crack resistance (KIc) were performed both for material in the as-cast state and after heat treatments. The influence of the initial microstructure on the investigated cast steel hardness – after the normalizing and after the normalizing and tempering – was determined. Findings: Changes in the microstructure of the cast bainitic scissors crossovers were determined and their properties described. Research limitations/implications: The investigations were performed in order to estimate a possibility of applying bainitic cast steels for production of scissors crossovers in the form of monolithic blocks. Practical implications: Application of bainitic cast steels for scissors crossovers in the form of monolithic blocks. Originality/value: Designing of the chemical composition of the bainitic cast steel (Mn-Cr-Mo-V-Ni) and its heat treatment.

4

Influence of heat treatment on microstructure and properties of bainitic cast steel used for frogs in railway crossovers

Parzych S., Tasak E.

Archives of Foundry Engineering

|

2010

|

Vol. 10, iss. 1 spec.

113--116

EN

This work deals with influence of heat treatment on microstructure and properties of sample cast assigned as a material used for frogs in railway crossover. Materials used in railway industry for frogs (manganese cast steel and forged pearlitic steel) do not fulfil strict conditions of exploitation of railway. One of the solutions is using cast steel with bainitic or bainite-martensite microstructure, what allows to gain high resistance properties (Rm = 1400 MPa, Rp0,2 = 900 MPa, hardness to 400 HBW). The cooling rates of rail type UIC60 shows that it is possible to reach the bainitic microstructure in cast of frog. The microstructure of lower banite should have an advantageous influence on cracking resistance. In order to set the parameters of heat treatment, the critical temperatures were determined by dilatometric methods determined. This heat treatment consisted of normalizing that prepared it to the farther process of resistance welding. Moreover, the CCT diagram of proposed bainitic cast steel was prepared. The exams were done that can be used to evaluate the influence of heat treatment on microstructure and properties of the sample cast.