Study of the Columnar Grain Growth in IF Steels during Continuous Heat Cycles

2010 ◽  
Vol 638-642 ◽  
pp. 3284-3290
Author(s):  
Wlodzimierz Kaluba ◽  
T. Kaluba
Keyword(s):  
Temperature Gradient ◽  
Phase Transformations ◽  
Continuous Heating ◽  
Air Cooling ◽  
Cooling Period ◽  
Heating And Cooling ◽  
Columnar Grains ◽  
Interface Displacement ◽  
Geometrical Form ◽  
Columnar Grain

The growth of columnar grains in fully recristallized IF steel during rapid heat cycles was examined experimentally. The heat cycles consisted of continuous heating with a rate up to 1500°C/s followed by water or air cooling. The employed heating method, as well as the geometrical form of the samples, enabled to obtain the temperature gradients up to 2000°C cm-1. Moreover, temperature measurements and recordings with the aid of ultra-rapid infrared pyrometry made it possible to determine the characteristic temperatures of phase transformations taking place during heating and cooling periods. The main key parameters of the columnar growth, including temperature gradient and the displacement rate of isotherms corresponding to ferrite-austenite and austenite-ferrite phase transformations could also be examined. The results show that the growth of columnar grains already starts at the heating stage at the ferrite/austenite interface moving against the temperature gradient. During the air cooling period, the growth is taking place according to the temperature gradient, together with the austenite/ferrite interface displacement. It was suggested that columnar-like morphology development occurs according to a selective growth mechanism.

The Observation of Austenite to Ferrite Martensitic Transformation in an Fe-Mn-Al Austenitic Steel after Cooling from High Temperature

2016 ◽  
Vol 879 ◽  
pp. 335-338 ◽  
Author(s):  
Wei Chun Cheng ◽  
Kun Hsien Lee ◽  
Shu Mao Lin ◽  
Shao Yu Chien
Keyword(s):  
Martensitic Transformation ◽  
Phase Transformations ◽  
Austenitic Steel ◽  
Lath Martensite ◽  
Equilibrium Phase ◽  
Stable Phase ◽  
Air Cooling ◽  
Trip Steels ◽  
Heating And Cooling ◽  
Austenite Grains

Fe-Mn-Al steels with low density have the potential to substitute for TRIP (transformation induced plasticity) steels. For the development of Fe-Mn-Al TRIP steels, phase transformations play an important role. Our methods of studying the phase transformations of the Fe-16.7 Mn-3.4 Al (wt%) austenitic steel include heating and cooling. We have studied the martensitic transformation of the ternary Fe-Mn-Al steel. Single austenite phase is the equilibrium phase at 1373 K, and dual phases of ferrite and austenite are stable at low temperatures. It is noteworthy that lath martensite forms in the prior austenite grains after cooling from 1373 K via quenching, air-cooling, and/or furnace-cooling. The crystal structure of the martensite belongs to body-centered cubic. The formation mechanism of the ferritic martensite is different from the traditional martensite in steels. Ferrite is the stable phase at low temperature.

scholarly journals Optimum Thickness of Thermal Insulation with Both Economic and Ecological Costs of Heating and Cooling

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3835
Author(s):  
Robert Dylewski ◽  
Janusz Adamczyk
Keyword(s):  
Thermal Insulation ◽  
Construction Materials ◽  
Optimum Thickness ◽  
Degree Days ◽  
Transfer Coefficients ◽  
Cooling Period ◽  
Heating And Cooling ◽  
Optimum Heat ◽  
Materials Used ◽  
Building Walls

The energy efficiency of the construction sector should be determined by the cleanliness of the environment and, thus, the health of society. The scientific aim of this article was to develop a methodology for determining the optimum thickness of thermal insulation, taking into account both economic and ecological aspects and considering both heating and cooling costs. The method takes into account the number of degree days of the heating period, as well as the number of degree days of the cooling period. Variants in terms of different types of thermal insulation, various types of construction materials for building walls, climatic zones and heat sources, were taken into consideration. In order to find the optimum thicknesses of thermal insulation, both in economic and ecological terms, a metacriterion was used. The optimum thicknesses of thermal insulation with the use of the metacriterion were obtained in the range of 0.11–0.55 m. It was observed that the values of the optimum heat transfer coefficients for economic and ecological reasons do not depend on the type of construction materials used for vertical walls. The type of applied heat source is of the greatest importance for the size of the economic and ecological benefits. The proposed mathematical model for determining the optimum thickness of thermal insulation with the use of a metacriterion is a kind of generalization of earlier models from the literature.

scholarly journals Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xiangjun Xu ◽  
Rui Hu ◽  
Junpin Lin ◽  
Jian Guo
Keyword(s):  
Mushy Zone ◽  
Solidification Rate ◽  
Solidus Temperature ◽  
Melting Zone ◽  
Optical Microscope ◽  
Directionally Solidified ◽  
Good Oxidation Resistance ◽  
Columnar Grains ◽  
Columnar Grain ◽  
Evolution Of Microstructure

High Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solidified (DS) Ti-45Al-8Nb (in atomic percent) alloy prepared at withdrawing rates of 30 μm/s and 200 μm/s and a temperature gradient of 4200 K/m were observed by optical microscope and electronic probe microanalyzer. The microsegregations were characterized by wave dispersive spectroscopy. The results show that the DS ingots include the no melting zone, directionally solidified zone with columnar grains, mushy zone, and quenched liquid zone. The primary dendritic arm spacings are 353 μm and 144 μm, respectively, for the two ingots. But the solidified microstructures of the ingots are large lamellar colonies, which contain a few B2 patches and γ bands induced by microsegregation. From dendritic zone to columnar zone, the volume fractions of B2 patches and γ bands decrease. The segregation extents of Al and Nb decrease with the increase of solidification rate. There exists an obvious back diffusion process of Al during solidification and cooling after solidification. According to evolution of Al concentration profiles from mushy zone to columnar grain zone, interdiffusion coefficient for Al in β-Ti at near solidus temperature is semiquantitatively calculated, and the value is (6 – 11) × 10−11 m2/s.

scholarly journals Analysis of the Impact of the Construction of a Trombe Wall on the Thermal Comfort in a Building Located in Wrocław, Poland

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 761 ◽  
Author(s):  
Jagoda Błotny ◽  
Magdalena Nemś
Keyword(s):  
Temperature Increase ◽  
Cooling System ◽  
Renewable Energy Sources ◽  
Heating System ◽  
Wall Material ◽  
Ansys Fluent ◽  
Cooling Period ◽  
Heating And Cooling ◽  
Trombe Wall ◽  
The Impact

Changes in climate, which in recent years have become more and more visible all over the world, have forced scientists to think about technologies that use renewable energy sources. This paper proposes a passive solar heating and cooling system, which is a Trombe wall located on the southern facade of a room measuring 4.2 m × 5.2 m × 2.6 m in Wrocław, Poland. The studies were carried out by conducting a series of numerical simulations in the Ansys Fluent 16.0 environment in order to examine the temperature distribution and air circulation in the room for two representative days during the heating and cooling period, i.e., 16 January and 15 August (for a Typical Meteorological Year). A temperature increase of 1.11 °C and a temperature decrease in the morning and afternoon hours of 2.27 °C was obtained. Two options for optimizing the passive heating system were also considered. The first involved the use of triple glazing filled with argon in order to reduce heat losses to the environment, and for this solution, a temperature level that was higher by 8.50 °C next to the storage layer and an increase in the average room temperature by 1.52 °C were achieved. In turn, the second solution involved changing the wall material from concrete to brick, which resulted in a temperature increase of 0.40 °C next to the storage layer.

Grrain Orientations and their Influence on Precipitation in Hot Compressed Columnar Grains in Electrical Steel

2011 ◽  
Vol 702-703 ◽  
pp. 738-741
Author(s):  
H. Qian ◽  
Ping Yang ◽  
G.H. Zheng ◽  
Wei Min Mao
Keyword(s):  
Hot Deformation ◽  
Grain Orientation ◽  
Electrical Steel ◽  
Compression Axis ◽  
Electrical Steels ◽  
Grain Orientations ◽  
Columnar Grains ◽  
Columnar Grain ◽  
The Relationship ◽  
Sample Axis

To identify the relationship between grain orientation and precipitation of MnS/AlN particles during hot deformation, cylinder samples containing columnar grains in electrical steels were prepared with different angles between columnar grain axis and sample axis. They were heated at 1360°C and compressed at 1100°C for 50%. Grain orientations and the precipitation states are determined using XRD, EBSD, EDS and SEM. Results indicate a general behavior of less precipitates in <100> and more precipitates in <111> grains. In addition, more precipitates were observed in samples with grain boundaries perpendicular to compression axis.

Numerical Investigation of the Influence of Microstructure on the Residual Stress Distribution and Distortion in DP600 Welds

2011 ◽  
Vol 681 ◽  
pp. 79-84 ◽  
Author(s):  
A.M.Akbari Pazooki ◽  
M.J.M. Hermans ◽  
I.M. Richardson
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Dual Phase Steel ◽  
Ferrite Matrix ◽  
Volume Changes ◽  
Heating And Cooling ◽  
Distortion Level ◽  
Martensitic Phase Transformations ◽  
Cct Diagrams

Dual phase steel consists of martensite embedded in a ferrite matrix. The material experiences high heating and cooling rates during welding, which alter the microstructure significantly. In this work the effects of solid state phase transformations on the prediction of residual stresses and distortion during welding of DP600 steel is investigated. Phase fractions have been calculated implicitly using continuous cooling time (CCT) diagrams. The results of the model are compared with experimental measurements for bead-on-plate welds made on DP600 sheets. It is found that the volume changes and the increase of the strength due to the martensitic transformation have both a significant effect on the residual stress and distortion level although in opposite directions. Martensitic phase transformations in DP600 steel tend to reduce tensile residual stresses in the weld metal.

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