In this study experiments were carried out on the kinetics of transformation of high-carbon low-a... more In this study experiments were carried out on the kinetics of transformation of high-carbon low-alloyed austenite with carbon mass percentage of 1,2% and manganese mass percentage of 3% in the temperature range from 200 to 300 °C. It was found, that at 200°C austenite transformation starts after 5 . 10 5 s; after 5 . 10 6 s the content of the α-phase reaches a level of 94%. A further increase in processing temperature results in shorter incubation periods but significantly lower completeness of transformation. A modification of the chemical composition of the austenite phase also results in higher transformation speed. So for a composition of austenite with 1,2 %С, 3 %Mn and 2 %Si heat treatment at 250-270°C allowed to obtain hardness levels of 400HV as fast as after 1 day. It could be observed a difference in fine structure of bainite resulting from transformation of austenite without silicon and austenite with silicon mass percentage of 2%. Silicon favours the formation of long an...
A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenchi... more A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenching from 900 and 1000 °C, resulting in microstructures containing 60 and 94% of retained austenite, respectively. Subsequent abrasive wear tests of quenched samples were performed using two-body abrasion and three-body abrasion testing machines. Investigations on worn surface and subsurface were carried out using SEM, XRD, and microhardness measurement. It was found that the highest microhardness of worn surface (about 1400 HV0.05) was achieved on samples quenched from 900 °C after three-body abrasion. Microhardness of samples after two-body abrasion was noticeably smaller. with a maximum of about 1200 HV0.05. This difference correlates with microstructure investigations along with XRD results. Three-body abrasion has produced a significantly deeper deformed layer; corresponding diffractograms show bigger values of the full width at half maximum parameter (FWHM) for both α and γ alone sta...
This article aims to discusses machine learning modelling using a dataset provided by the LANL (L... more This article aims to discusses machine learning modelling using a dataset provided by the LANL (Los Alamos National Laboratory) earthquake prediction competition hosted by Kaggle. The data were obtained from a laboratory stick-slip friction experiment that mimics real earthquakes. Digitized acoustic signals were recorded against time to failure of a granular layer compressed between steel plates. In this work, machine learning was employed to develop models that could predict earthquakes. The aim is to highlight the importance and potential applicability of machine learning in seismology The XGBoost algorithm was used for modelling combined with 6-fold cross-validation and the mean absolute error (MAE) metric for model quality estimation. The backward feature elimination technique was used followed by the forward feature construction approach to find the best combination of features. The advantage of this feature engineering method is that it enables the best subset to be found from...
The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carb... more The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carbon wear resistant steel without losing the structure that is previously obtained by heat treatment. 120Mn3Si2 steel was chosen for experiments due to its good resistance to mechanical wear. The fast cooling of welding joints in water was carried out right after welding. The major conclusion is that the soft austenitic layer appears in the vicinity of the fusion line as a result of the fast cooling of the welding joint. The microstructure of the heat affected zone of quenched 120Mn3Si2 steel after welding with rapid cooling in water consists of several subzones. The first one is a purely austenitic subzone, followed by austenite + martensite microstructure, and finally, an almost fully martensitic subzone. The rest of the heat affected zone is tempered material that is heated during welding below A1 critical temperature. ISO 4136 tensile tests were carried out for the welded joints of 120...
In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and... more In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and heat affected zone (HAZ) of high-carbon low alloyed steel have been studied. The main idea was that despite of high carbon content (1.2%) it is necessary to achieve quenching in HAZ. Due to proper chemical composition of welded steel martensite start temperature Ms is about 20 oC, therefore austenitic structure of quenched metal is preserved after rapid cooling. Exposition of HAZ to excessive heat during welding cycle leads to local precipitation of carbides from austenite and thus raising of Ms. In this case some amount of martensite was present in structure after cooling along with austenite and carbides. Microstructure, microhardness and chemical composition of remelted electrode metal, fusion zone and HAZ were studied by means of optical microscopy, SEM, EDX and microhardness testing.
In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and... more In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and heat affected zone (HAZ) of high-carbon low alloyed steel have been studied. The main idea was that despite of high carbon content (1.2%) it is necessary to achieve quenching in HAZ. Due to proper chemical composition of welded steel martensite start temperature Ms is about 20 oC, therefore austenitic structure of quenched metal is preserved after rapid cooling. Exposition of HAZ to excessive heat during welding cycle leads to local precipitation of carbides from austenite and thus raising of Ms. In this case some amount of martensite was present in structure after cooling along with austenite and carbides. Microstructure, microhardness and chemical composition of remelted electrode metal, fusion zone and HAZ were studied by means of optical microscopy, SEM, EDX and microhardness testing.
Представлены результаты исследований износостойкости сталей и чугунов при абразивном изнашивании ... more Представлены результаты исследований износостойкости сталей и чугунов при абразивном изнашивании в широком диапазоне условий трения. Показано, что высокая износостойкость может быть достигнута не только за счет повышения объемной доли карбидных фаз в структуре сплавов, но и благодаря получению матрицы высокоуглеродистого нестабильного аустенита. Исследовано влияние широкого спектра параметров трибосистемы на износостойкость нелегированных и легированных железоуглеродистых сплавов в различном структурном состоянии.
A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial s... more A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial steel and a new 120Mn3 steel was performed. It could be demonstrated, that wear resistance of the proposed 120Mn3 steel is 2 to 5 times higher than that of the commercial steel. This improvement results from formation of martensite at the contact surface induced by plastical deformation during contact of abrasive particles for the case that the steel has been thermically treated to be in metastable austenite structure state by quenching from high temperatures. After wear testing the hardness of the contact surface increased up to 1200-1250 HV. Usage of the proposed material in bulk or as surface welded or surface heat treated layers in different machine parts working under abrasive
Frictional heating is analyzed to check the wear resistance of major structural components of und... more Frictional heating is analyzed to check the wear resistance of major structural components of undoped ferricarbonic alloys during abrasive wear. It is established that the wear resistance of austenite drops twofold once the temperature leaps to 130°C. The wear resistance of other structural components (ferrite, perlite, and martensite) diminishes in heating less intensively, but the wear resistance of unstable austenite is at the maximum level at any temperature within the studied range (up to 290°C).
This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white ... more This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.
The compositions of wear-resistant steels used as the material for grinding media are validated i... more The compositions of wear-resistant steels used as the material for grinding media are validated in order to obtain the optimal relation between the wear resistance and cost. Mathematical experiment planning reveals that low-alloyed hypereutectiod steels with the austenite-martensite structure without secondary carbides and eutectoid steels with the tempered martensite structure are the most promising for impact-abrasivecorrosive wear conditions.
Laboratory tests of iron-based alloys for abrasive wear show that the best wear resistance of the... more Laboratory tests of iron-based alloys for abrasive wear show that the best wear resistance of the alloys with both the martensite and austenite metallic matrix is achieved in the iron-carbon system. The greater the content of alloying elements in the austenite, the more pronounced is the reduction of its wear resistance due to alloying. It is revealed that the content of the alloying elements in the wear-resistant alloys for grinding media must be as low as possible, but yet sufficient to ensure the required manufacturability of articles.
In this study experiments were carried out on the kinetics of transformation of high-carbon low-a... more In this study experiments were carried out on the kinetics of transformation of high-carbon low-alloyed austenite with carbon mass percentage of 1,2% and manganese mass percentage of 3% in the temperature range from 200 to 300 °C. It was found, that at 200°C austenite transformation starts after 5 . 10 5 s; after 5 . 10 6 s the content of the α-phase reaches a level of 94%. A further increase in processing temperature results in shorter incubation periods but significantly lower completeness of transformation. A modification of the chemical composition of the austenite phase also results in higher transformation speed. So for a composition of austenite with 1,2 %С, 3 %Mn and 2 %Si heat treatment at 250-270°C allowed to obtain hardness levels of 400HV as fast as after 1 day. It could be observed a difference in fine structure of bainite resulting from transformation of austenite without silicon and austenite with silicon mass percentage of 2%. Silicon favours the formation of long an...
A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenchi... more A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenching from 900 and 1000 °C, resulting in microstructures containing 60 and 94% of retained austenite, respectively. Subsequent abrasive wear tests of quenched samples were performed using two-body abrasion and three-body abrasion testing machines. Investigations on worn surface and subsurface were carried out using SEM, XRD, and microhardness measurement. It was found that the highest microhardness of worn surface (about 1400 HV0.05) was achieved on samples quenched from 900 °C after three-body abrasion. Microhardness of samples after two-body abrasion was noticeably smaller. with a maximum of about 1200 HV0.05. This difference correlates with microstructure investigations along with XRD results. Three-body abrasion has produced a significantly deeper deformed layer; corresponding diffractograms show bigger values of the full width at half maximum parameter (FWHM) for both α and γ alone sta...
This article aims to discusses machine learning modelling using a dataset provided by the LANL (L... more This article aims to discusses machine learning modelling using a dataset provided by the LANL (Los Alamos National Laboratory) earthquake prediction competition hosted by Kaggle. The data were obtained from a laboratory stick-slip friction experiment that mimics real earthquakes. Digitized acoustic signals were recorded against time to failure of a granular layer compressed between steel plates. In this work, machine learning was employed to develop models that could predict earthquakes. The aim is to highlight the importance and potential applicability of machine learning in seismology The XGBoost algorithm was used for modelling combined with 6-fold cross-validation and the mean absolute error (MAE) metric for model quality estimation. The backward feature elimination technique was used followed by the forward feature construction approach to find the best combination of features. The advantage of this feature engineering method is that it enables the best subset to be found from...
The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carb... more The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carbon wear resistant steel without losing the structure that is previously obtained by heat treatment. 120Mn3Si2 steel was chosen for experiments due to its good resistance to mechanical wear. The fast cooling of welding joints in water was carried out right after welding. The major conclusion is that the soft austenitic layer appears in the vicinity of the fusion line as a result of the fast cooling of the welding joint. The microstructure of the heat affected zone of quenched 120Mn3Si2 steel after welding with rapid cooling in water consists of several subzones. The first one is a purely austenitic subzone, followed by austenite + martensite microstructure, and finally, an almost fully martensitic subzone. The rest of the heat affected zone is tempered material that is heated during welding below A1 critical temperature. ISO 4136 tensile tests were carried out for the welded joints of 120...
In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and... more In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and heat affected zone (HAZ) of high-carbon low alloyed steel have been studied. The main idea was that despite of high carbon content (1.2%) it is necessary to achieve quenching in HAZ. Due to proper chemical composition of welded steel martensite start temperature Ms is about 20 oC, therefore austenitic structure of quenched metal is preserved after rapid cooling. Exposition of HAZ to excessive heat during welding cycle leads to local precipitation of carbides from austenite and thus raising of Ms. In this case some amount of martensite was present in structure after cooling along with austenite and carbides. Microstructure, microhardness and chemical composition of remelted electrode metal, fusion zone and HAZ were studied by means of optical microscopy, SEM, EDX and microhardness testing.
In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and... more In this paper the effect of rapid cooling during arc welding on the structure of fusion layer and heat affected zone (HAZ) of high-carbon low alloyed steel have been studied. The main idea was that despite of high carbon content (1.2%) it is necessary to achieve quenching in HAZ. Due to proper chemical composition of welded steel martensite start temperature Ms is about 20 oC, therefore austenitic structure of quenched metal is preserved after rapid cooling. Exposition of HAZ to excessive heat during welding cycle leads to local precipitation of carbides from austenite and thus raising of Ms. In this case some amount of martensite was present in structure after cooling along with austenite and carbides. Microstructure, microhardness and chemical composition of remelted electrode metal, fusion zone and HAZ were studied by means of optical microscopy, SEM, EDX and microhardness testing.
Представлены результаты исследований износостойкости сталей и чугунов при абразивном изнашивании ... more Представлены результаты исследований износостойкости сталей и чугунов при абразивном изнашивании в широком диапазоне условий трения. Показано, что высокая износостойкость может быть достигнута не только за счет повышения объемной доли карбидных фаз в структуре сплавов, но и благодаря получению матрицы высокоуглеродистого нестабильного аустенита. Исследовано влияние широкого спектра параметров трибосистемы на износостойкость нелегированных и легированных железоуглеродистых сплавов в различном структурном состоянии.
A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial s... more A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial steel and a new 120Mn3 steel was performed. It could be demonstrated, that wear resistance of the proposed 120Mn3 steel is 2 to 5 times higher than that of the commercial steel. This improvement results from formation of martensite at the contact surface induced by plastical deformation during contact of abrasive particles for the case that the steel has been thermically treated to be in metastable austenite structure state by quenching from high temperatures. After wear testing the hardness of the contact surface increased up to 1200-1250 HV. Usage of the proposed material in bulk or as surface welded or surface heat treated layers in different machine parts working under abrasive
Frictional heating is analyzed to check the wear resistance of major structural components of und... more Frictional heating is analyzed to check the wear resistance of major structural components of undoped ferricarbonic alloys during abrasive wear. It is established that the wear resistance of austenite drops twofold once the temperature leaps to 130°C. The wear resistance of other structural components (ferrite, perlite, and martensite) diminishes in heating less intensively, but the wear resistance of unstable austenite is at the maximum level at any temperature within the studied range (up to 290°C).
This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white ... more This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.
The compositions of wear-resistant steels used as the material for grinding media are validated i... more The compositions of wear-resistant steels used as the material for grinding media are validated in order to obtain the optimal relation between the wear resistance and cost. Mathematical experiment planning reveals that low-alloyed hypereutectiod steels with the austenite-martensite structure without secondary carbides and eutectoid steels with the tempered martensite structure are the most promising for impact-abrasivecorrosive wear conditions.
Laboratory tests of iron-based alloys for abrasive wear show that the best wear resistance of the... more Laboratory tests of iron-based alloys for abrasive wear show that the best wear resistance of the alloys with both the martensite and austenite metallic matrix is achieved in the iron-carbon system. The greater the content of alloying elements in the austenite, the more pronounced is the reduction of its wear resistance due to alloying. It is revealed that the content of the alloying elements in the wear-resistant alloys for grinding media must be as low as possible, but yet sufficient to ensure the required manufacturability of articles.
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