scholarly journals Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry—Assessment Based on the Instrumented Impact Test

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3922
Author(s):  
Mariusz Maslak ◽  
Michal Pazdanowski ◽  
Marek Stankiewicz ◽  
Paulina Zajdel
Keyword(s):  
Charpy Impact ◽  
Water Mist ◽  
Heating Regime ◽  
Building Structures ◽  
Initial State ◽  
Slow Cooling ◽  
Natural Fire ◽  
Development Scenarios ◽  
Steel Grades ◽  
Fire Conditions

The change in the value of the breaking energy is discussed here for selected steel grades used in building structures after subjecting the samples made of them to episodes of heating in the steady-state heating regime and then cooling in simulated fire conditions. These changes were recorded based on the instrumented Charpy impact tests, in relation to the material initial state. The S355J2+N, 1H18N9T steels and also X2CrNiMoN22-5-3 duplex steel were selected for detailed analysis. The fire conditions were modelled experimentally by heating the samples and then keeping them for a specified time at a constant temperature of: 600 °C (first series) and 800 °C (second series), respectively. Two alternative cooling variants were investigated in the experiment: slow cooling of the samples in the furnace, simulating the natural fire progress, without any external extinguishing action and cooling in water mist simulating an extinguishing action by a fire brigade. The temperature of the tested samples was set at the level of −20 °C and alternatively at the level of +20 °C. The conducted analysis is aimed at assessing the risk of sudden, catastrophic fracture of load-bearing structure made of steel degraded as a result of a fire that occurred previously with different development scenarios.

scholarly journals Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry – Assessment Based on the Instrumented Impact Test

2021 ◽  
Author(s):  
Mariusz Maslak ◽  
Michal Pazdanowski ◽  
Marek Stankiewicz ◽  
Paulina Zajdel
Keyword(s):  
Charpy Impact ◽  
Water Mist ◽  
Heating Regime ◽  
Building Structures ◽  
Initial State ◽  
Slow Cooling ◽  
Natural Fire ◽  
Development Scenarios ◽  
Steel Grades ◽  
Fire Conditions

The change in the value of the breaking energy is discussed here for selected steel grades used in building structures after subjecting the samples made of them to episodes of heating in the steady-state heating regime and then cooling in a simulated fire conditions. These changes were recorded based on the instrumented Charpy impact tests, in relation to the material initial state. The S355J2+N, 1H18N9T steels and also X2CrNiMoN22-5-3 duplex steel were selected for detailed analysis. The fire conditions were modelled experimentally by heating the samples and then keeping them for a specified time at a constant temperature of: 600°C (first series) and 800°C (second series), respectively. Two alternative cooling variants were investigated in the experiment: slow cooling of the samples in the furnace, simulating the natural fire progress, without any external extinguishing action, and cooling them in water mist simulating an extinguishing action by a fire brigade. The temperature of the tested samples was set at the level -20oC and alternatively at the level + 20oC. The conducted analysis is aimed at assessing the risk of sudden, catastrophic fracture of load-bearing structure made of steel degraded as a result of a fire previously occurred with different development scenarios.

scholarly journals Effect of Fire Temperature and Exposure Time on High-Strength Steel Bolts Microstructure and Residual Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3116
Author(s):  
Paweł Artur Król ◽  
Marcin Wachowski
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Heating Time ◽  
Heat Treatments ◽  
Initial State ◽  
Natural Fire ◽  
Xrd Phase Analysis ◽  
Steel Bolts ◽  
Cooling Methods ◽  
Fire Conditions

In this study, the influence of different fire conditions on tempered 32CrB3 steel bolts of Grade 8.8 was investigated. In this research different temperatures, heating time, and cooling methods were correlated with the microstructure, hardness, and residual strength of the bolts. Chosen parameters of heat treatments correspond to simulated natural fire conditions that may occur in public facilities. Heat treated and unheated samples cut out from a series of tested bolts were subjected to microstructural tests using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), XRD phase analysis, and the quantitative analysis of the microstructure. The results of the microstructure tests were compared with the results of strength tests, including hardness and the ultimate residual tensile strength of the material (UTS) in the initial state and after the heat treatments. Results of the investigations revealed considerable microstructural changes in the bolt material as a result of exposing it to different fire conditions and cooling methods. A conducted comparative analysis also showed a significant effect of all such factors as the temperature level of the simulated fire, its duration, and the fire-fighting method on the mechanical properties of the bolts.

Stainless Steels Sintered Form the Mixture of Prealloyed Stainless Steel and Alloying Element Powders

2011 ◽  
Vol 672 ◽  
pp. 165-170 ◽  
Author(s):  
Zbigniew Brytan ◽  
Marco Actis Grande ◽  
Mario Rosso ◽  
Róbert Bidulský ◽  
L.A. Dobrzański
Keyword(s):  
Mechanical Properties ◽  
Impact Energy ◽  
Stainless Steels ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Duplex Stainless Steels ◽  
Vacuum Furnace ◽  
Slow Cooling ◽  
Rapid Cooling ◽  
Plastic Properties

The aim of the presented paper is to describe the sintered duplex stainless steels manufactured in sinter-hardening process and their structural and mechanical properties. Duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed base powders by controlled addition of alloying elements powder. Prepared mixes were compacted at 700MPa and sintered in a vacuum furnace with argon backfilling at temperature of 1240°C for 1h. After sintering different cooling cycles were applied: rapid cooling (6°C/s) using nitrogen under pressure and slow cooling (0.1°C/s) with furnace in argon atmosphere. Produced sintered duplex stainless steels were studied by scanning and optical microscopy and EDS chemical analysis of microstructure components as well as X-ray analysis. Mechanical properties were studied through tensile and three-point bending tests and Charpy impact test. It was demonstrated that austenitic-ferritic microstructures with regular arrangement of both phases and absence of precipitates can be obtained with properly designed powder mix composition as well as sintering cycle with rapid cooling rate. Produced sintered duplex steels show good mechanical properties which depend on austenite/ferrite ratio in the microstructure and elements partitioning (Cr/Ni) between phases. The optimal mechanical properties were obtained for compositions based on ferritic 410L powder where the balanced distribution of α and γ is present and the tensile strength can reach value about 500MPa with 16% of elongation and impact energy about 120J. The precipitations of hard intermetallic σ-FeCr phase take place when sintering with slow cooling cycle what cause substantial decrease of plastic properties, including reduce of elongation to 7% and in particular decrease of impact energy to 68 J.

scholarly journals ANALYSIS OF COMPOSITE BUILDINGS UNDER FIRE CONDITIONS

2016 ◽  
Author(s):  
Shuyuan Lin ◽  
Zhaohui Huang ◽  
Mizi Fan
Keyword(s):  
Composite Structures ◽  
Three Dimensional ◽  
Membrane Action ◽  
Natural Fire ◽  
End Plate ◽  
Floor Slabs ◽  
Support Conditions ◽  
Plate Connections ◽  
The Impact ◽  
Fire Conditions

In this paper, the performances of a generic three dimensional 45m x 45m composite floor subjected to ISO834 Fire and Natural Fire are investigated. The influences of reinforcing steel mesh and vertical support conditions on the tensile membrane action of floor slabs are investigated in details. Two robust 2-node connection element models developed by the authors are used to model the behaviour of end-plate and partial end-plate connections of composite structures under fire conditions. The impact of connections on the 3D behaviour of composite floor is considered. Based on the results obtained, some design recommendations are proposed to enhance the fire safety design of composite buildings.

scholarly journals Impact Strength of Austenitic and Ferritic-Austenitic Cr-Ni Stainless Cast Steel in -40 and +20°C Temperature

2014 ◽  
Vol 59 (3) ◽  
pp. 1103-1106
Author(s):  
B. Kalandyk ◽  
R. Zapała ◽  
Ł. Boroń ◽  
M. Solecka
Keyword(s):  
Impact Strength ◽  
Volume Fraction ◽  
Cast Steel ◽  
Testing Machine ◽  
Charpy Impact ◽  
Impact Testing ◽  
Two Phase ◽  
Steel Grades ◽  
Charpy Impact Testing ◽  
The Impact

Abstract Studies described in this paper relate to common grades of cast corrosion resistant Cr-Ni steel with different matrix. The test materials were subjected to heat treatment, which consisted in the solution annealing at 1060°C followed by cooling in water. The conducted investigations, besides the microstructural characteristics of selected cast steel grades, included the evaluation of hardness, toughness (at a temperature of -40 and +20oC) and type of fracture obtained after breaking the specimens on a Charpy impact testing machine. Based on the results of the measured volume fraction of ferrite, it has been found that the content of this phase in cast austenitic steel is 1.9%, while in the two-phase ferritic-austenitic grades it ranges from 50 to 58%. It has been demonstrated that within the scope of conducted studies, the cast steel of an austenitic structure is characterised by higher impact strength than the two-phase ferritic-austenitic (F-A) grade. The changing appearance of the fractures of the specimens reflected the impact strength values obtained in the tested materials. Fractures of the cast austenitic Cr-Ni steel obtained in these studies were of a ductile character, while fractures of the cast ferritic-austenitic grade were mostly of a mixed character with the predominance of brittle phase and well visible cleavage planes.

Methodological Features of WWER RPV Metal Critical Temperature of Brittleness Prediction on the Base of the Data Scatter and the Chemical Composition

2015 ◽  
Author(s):  
Igor Orynyak ◽  
Maksym Zarazovskii ◽  
Sergii Radchenko
Keyword(s):  
Critical Temperature ◽  
Chemical Composition ◽  
Charpy Impact ◽  
Thermal Ageing ◽  
Surveillance Program ◽  
Initial State ◽  
Predictive Values ◽  
Integrity Assessment ◽  
Critical Temperature Of Brittleness ◽  
The One

For WWER-1000 reactor pressure vessel (RPV) the metal embrittlement monitoring is performed with the usage of the radiation and the temperature surveillance specimens (SS) sets. For the fracture toughness curve indexing the critical temperature of brittleness (CTB) is used, CTB is obtained by the processing of Charpy impact energy data. Modern codes that regulate WWER RPVs CTB prediction are based on the CTB shift ideology. According to this ideology the CTB is defined as the initial CTB value plus CTB shift due to the radiation, plus CTB shift due to the thermal ageing, plus certain margin. This margin includes the scatter of CTB in the initial state, scatter of CTB shift due to the radiation and scatter of CTB shift due to the thermal ageing. A tendency of modern WWER RPV integrity assessment codes to provide conservatism with: choosing the CTB in the initial state for the CTB shifts determination; choosing the CTB in the initial state for the CTB determination; taking into account the scatter of CTB in the initial state, scatter of CTB shift due to the radiation and scatter of CTB shift due to the thermal ageing, leads to huge predictive values of CTB and to formal unfulfillment of brittle fracture criterion for RPVs. This paper demonstrates that the usage of actual CTB data and their scatter (obtained directly from Charpy V-notched impact tests) instead of the shift ideology can be the one of the possible ways of adequate CTB prediction. The CTB database for welds is created on the base of the results of WWER-1000 RPV surveillance program of all Ukrainian NPPs. The article presents the results of the thermal aged Charpy V-notched SS tests. The thermal aging has been shown to be practically absent. The CTB thermal shift values, which were obtained in some laboratories, are caused by the CTB scattering in initial and thermal aged states only. According to the processing results of the irradiated SS tests data, the chromium, manganese and silicon have been found to have the greatest impact on the CTB value. The CTB dependence on the neutron fluence and chemical composition of WWER-1000 RPV beltline welds has been obtained. A new methodology of CTB curve prediction for WWER-1000 RPV welds is developed. This methodology is expected to be the basis in the modern Ukrainian normative of RPV integrity assessment since it reduces the unreasonably high conservatism inherent to the RPV project, to a more reasonable level.

Study on Oxidation Behavior of Stainless Steels in Short Time

2014 ◽  
Vol 633-634 ◽  
pp. 209-214
Author(s):  
Xia Wei Cheng ◽  
Zheng Yi Jiang ◽  
Guang Zheng Luo ◽  
Dong Bin Wei ◽  
Liang Hao
Keyword(s):  
Oxide Scale ◽  
Cross Section ◽  
Stainless Steels ◽  
Rolling Process ◽  
Water Mist ◽  
Chemical Compositions ◽  
Steel Matrix ◽  
Oxide Scales ◽  
Steel Grades ◽  
Short Time

The various chemical compositions of stainless steels can result in complication of the formation of oxide scales in hot rolling process. The time for formation of tertiary oxide scale during finishing rolling is short. In the present study, the oxidation tests with short time period were carried out on eight stainless steel grades by Gleeble 3500 thermal mechanical simulator in a simulated water mist environment. Multi-layers of oxide scale have been developed on all the steel grades during short time oxidation. Internal and intergranular oxides were formed in the steel matrix underneath the inner spinel oxide layer. The cross section of the oxide scales were examined and measured by SEM to understand the oxide scale cross section morphology and thickness.

scholarly journals Development of natural fire prevention method based on remote sensing data: case study of Krasnoyarsk region forests

2021 ◽  
Vol 27 (2) ◽  
pp. 340-354
Author(s):  
Almaz Gizatullin
Keyword(s):  
Remote Sensing ◽  
Remote Sensing Data ◽  
Fire Danger ◽  
Fire Prevention ◽  
Natural Fire ◽  
Sensing Data ◽  
Krasnoyarsk Region ◽  
Prevention Method ◽  
Fire Conditions

The stages of development of natural fire prevention method based on remote sensing data were considered. The case study is focused on Krasnoyarsk region forests. There was a rationale for selecting a study area on the basis of statistical fire data (FIRMS thermal hot spots 2016–2018) and a variety of fire conditions. The fire assessment was founded on the most informative fire factors—surface temperature, vegetation cover inhomogenuity and man-made load, which are derived by the natural-fire characteristics of the territory. These factors were evaluated by measuring parameters closed to them, respectively—radiobrightness temperature based on thermal emission, vegetation index NDVI and integral indicator of distance to settlements and roads. Materials from the Terra/Aqua, Sentinel-3, Landsat-8, Sentinel-2 satellites and Open Street Maps vector map layers were used as data sources. With use of statistical data, the relationship between above parameters and the present fire danger of Krasnoyarsk region was analyzed. Based on the results, we obtained different by forest rayon and fire season month correlation coefficients that described the contribution of individual factors to a fire danger, and threshold values of parameters for preventing fires. Then a sequence of stages of analytical and synthetic fire danger assessment as a study method was built. Validation of the method was performed in the most fire dangerous and representative in terms of fire conditions area in the south-west of the Krasnoyarsk Territory from April 1 to May 10, 2019. It showed sufficient accuracy (65 %) and reliability (58 %) of fire forecast.

scholarly journals Screen Wall Fire Resistance Investigation

2021 ◽  
Vol 6 ◽  
Author(s):  
Tatiana Eremina ◽  
Dmitry Korolchenko ◽  
V. E. Fadeev
Keyword(s):  
Fire Resistance ◽  
Functional Dependence ◽  
Heat Exposure ◽  
Experimental Studies ◽  
Engineering Problem ◽  
Thermal Engineering ◽  
Wall Structure ◽  
Building Structures ◽  
Critical Temperatures ◽  
Fire Conditions

The assessment of fire resistance for building constructions has been carried out by the solution of the heat engineering problem for heating up building structures under the conditions of non-stationary heat exposure with standard fire conditions. The finite element method is used as the solution method. Numerical simulation of heating of considered building structures under fire conditions was carried out using the Ansys Mechanical computer complex, which allows for a thermal engineering design to be calculated on the basis of its software model. The resulting functional dependence allows for determining the actual fire resistance of Pf depending on the thickness of sheets δ of the outer skin made of the basalt fire-proof material, as well as the geometric parameters of the protective screen (δ) depending on the required fire resistance from the condition of compliance with the requirements of constructive fire safety (Pf > Preq). Experimental studies to determine the fire resistance for membrane wall structures showed that an increase in temperature on its unheated surface vs. structure temperature prior to testing more than 180° С (195°С) occurs not earlier than 31 min. Upon reaching the critical temperatures on the unheated surface of the membrane wall structure independing on its thickness, the fire resistance limits REI 30-REI 120 are reached.

A Portable Field Burner to Simulate Natural Fire Conditions.

1978 ◽  
Vol 1 (2) ◽  
pp. 197 ◽  
Author(s):  
JH Leigh ◽  
BC Bautovich ◽  
MD Holgate
Keyword(s):  
Natural Fire ◽  
Fire Conditions
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