Observation and Analysis of the Microstructures of IGF Refined Low Carbon Microalloyed Non-Tempered Steel

2012 ◽  
Vol 602-604 ◽  
pp. 323-328
Author(s):  
Shu Hua Wang ◽  
Hai Ou Jing ◽  
Le Jin ◽  
Yan Xue
Keyword(s):  
Fine Particles ◽  
Hot Forging ◽  
Steel Structures ◽  
High Strength ◽  
Air Cooling ◽  
Low Carbon ◽  
Carbon Microalloyed ◽  
The Impact ◽  
Tempered Steel ◽  
Strength And Toughness

The IGF refined microalloyed non-tempered steel with high strength and toughness is developed, by adding trace elements such as vanadium and titanium and using aluminum as the deoxidizing elements. The combination of these elements and elements C and N in the steel leads to the precipitation of a great deal of fine and scattered alloy carbides and nitrides. These fine particles provide ideal precipitation positions for IGF’s nucleation. The results show that a lot of IGF appears in the developed steel after hot-forging and air cooling, which effectively divides up the austenite grains and refines the steel structures. The strength and toughness of the steel is increased. The tensile strength reaches 1150Mpa and the impact toughness is between 61.35-65.37J/cm2.

Charpy Impact Properties of Grain Boundary Allotriomorphic Ferrite and Granular Bainite Duplex Microstructure

2014 ◽  
Vol 1004-1005 ◽  
pp. 1236-1244 ◽  
Author(s):  
Ping Luo ◽  
Gu Hui Gao ◽  
Xiao Lu Gui ◽  
Bai Feng An ◽  
Zhun Li Tan ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Grain Boundary ◽  
Crack Path ◽  
High Strength ◽  
Propagation Path ◽  
Granular Bainite ◽  
Air Cooling ◽  
Low Carbon ◽  
Allotriomorphic Ferrite ◽  
The Impact

A new type of high strength and low cost bainitic steel with ultra-low carbon content and high Si content has been developed on the basis of Mn-series air-cooling bainitic steels. The tensile properties of YS>690MPa and the impact toughness of AKV>60J at-40°C were obtained by controlling the processing parameters. This was attributed to the formation of the grain boundary allotriomorphic ferrite (FGBA) and the granular bainite (GB) with different shape of M/A islands. The high strength due to the inter-lath lamellar M/A islands or retained austenite companying with high dislocated bainitic ferrite laths of average 300nm width. The effect of microstructure on the impact crack initiation and propagation was studied. The results showed that crack initiation occurred in two different types of sites: at interphase boundaries of bainite ferrite (BF) and M/A islands, at grain boundaries. The FGBA and bainite ferrite (BF) both had blunting effect on microcrack tip to reduce the crack propagation path. Because of the presence of FGBA, the unit crack path was short, at less than 5μm. The blunting effect of BF could be enhanced by the M/A islands, which force the cracks change the propagation path and reduce the unit crack path to less than the size of bainite packets. The mechanism of low temperature microcrack origin of the ultra-low carbon bainitic (ULCB) steel with the microstructure of the FGBA and GB was also discussed.

Development of Low Carbon Microalloyed Ultra High Strength Steels

2005 ◽  
Vol 500-501 ◽  
pp. 551-558 ◽  
Author(s):  
A. Ghosh ◽  
Brajendra Mishra ◽  
Subrata Chatterjee
Keyword(s):  
Room Temperature ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Hsla Steels ◽  
Finish Rolling ◽  
Ultra High Strength Steels ◽  
Rolling Temperatures ◽  
Carbon Microalloyed ◽  
Carbon Concentrations

In the present study HSLA steels of varying carbon concentrations, alloyed with Mn, Ni, Cr, Mo, Cu and micro-alloyed with Nb and Ti were subjected to different finish rolling temperatures from 850oC to 750oC in steps of 50oC. The microstructure of the steel predominantly shows martensite. Fine twins, strain induced precipitates in the martensite lath along with e-Cu precipitates are observed in the microstructure. With an increase in carbon content the strength value increases from 1200MPa UTS to 1700MPa UTS with a negligible reduction in elongation. Impact toughness values of 20-26 joules at room temperature and −40oC were obtained in sub-size samples.

Development of Low Carbon Microalloyed Bainitic Steels for Structural Plate Applications

2005 ◽  
Vol 500-501 ◽  
pp. 573-580 ◽  
Author(s):  
D. Ormston ◽  
Volker Schwinn ◽  
Klaus Hulka
Keyword(s):  
High Strength ◽  
Carbon Steels ◽  
Chemical Compositions ◽  
Low Carbon ◽  
Controlled Processes ◽  
Bainitic Steels ◽  
Steel Grades ◽  
Carbon Microalloyed ◽  
Hot Rolled ◽  
Plate Steels

Steels with bainitic microstructures show the capacity to fulfil the requirements of high strength and low temperature toughness necessary for plate steels in specialised industrial constructions. The introduction of steels with higher strength allows for weight reductions of steel constructions. This paper investigates the development of hot rolled structural plate steels through laboratory hot rolling simulations of thermo-mechanically controlled processes (TMCP). Specific alloying and microalloying along with an optimised TMCP process has allowed high tensile properties to be achieved in combination with high levels of toughness. Tensile strengths of up to 900 MPa have been achieved with Charpy V-notch toughness greater than 200J at –40°C. Elements such as molybdenum, niobium and boron have been added to low carbon steels to promote the formation of fully bainitic microstructures with much lightened chemical compositions. The presented concepts allow the production of steel grades above S500 up to S690.

scholarly journals Microstructure and mechanical characteristics of hot forged lateritic steels

2018 ◽  
Vol 204 ◽  
pp. 05007 ◽  
Author(s):  
Satrio Herbirowo ◽  
Luqmanul Hakim ◽  
Bintang Adjiantoro
Keyword(s):  
Raw Materials ◽  
Hot Forging ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Cast Steels ◽  
Preheating Temperature ◽  
Chemical Composition Of Steel ◽  
Forging Force ◽  
The Impact ◽  
Hot Forging Process

The current development of steel industry has constraints on the availability of raw materials, so we have developed local raw materials that are lateritic steels as a high potential for alternative manufacturing of steel. This research was conducted to understand the characteristics of lateritic steel through hot forging process by the mechanical and microstructure behaviour. The research methodology was chained by variety of preheating temperature of 800; 1000; 1200 °C and forging force from 0 until 1000 kilonewton. In case of hot forging values was obtained the impact and hardness properties also microstructure that compared with as-cast steels. The results of impact strength increased by 81.83% at the temperature of 1200 °C and the hardness increased by 4.99% at 1000 °C, for the microstructure analysis was produced the ferrite and pearlite phases with the fine grains. The chemical composition of steel is classified in low carbon steel included in lateritic steel it contains low alloy 1.78 Ni and 0.553 Cr %wt.

scholarly journals Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 747 ◽  
Author(s):  
Farnoosh Forouzan ◽  
M. Guitar ◽  
Esa Vuorinen ◽  
Frank Mücklich
Keyword(s):  
Grain Size ◽  
Carbon Steel ◽  
Weld Zone ◽  
Low Carbon Steel ◽  
High Strength ◽  
Precipitate Size ◽  
Low Carbon ◽  
Quenching And Partitioning ◽  
High Level ◽  
The Impact

To improve the weld zone properties of Advanced High Strength Steel (AHSS), quenching and partitioning (Q&P) has been used immediately after laser welding of a low-carbon steel. However, the mechanical properties can be affected for several reasons: (i) The carbon content and amount of retained austenite, bainite, and fresh martensite; (ii) Precipitate size and distribution; (iii) Grain size. In this work, carbon movements during the partitioning stage and prediction of Ti (C, N), and MoC precipitation at different partitioning temperatures have been simulated by using Thermocalc, Dictra, and TC-PRISMA. Verification and comparison of the experimental results were performed by optical microscopy, X-ray diffraction (XRD), Scanning Electron Microscop (SEM), and Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Scanning Diffraction (EBSD) analysis were used to investigate the effect of martensitic/bainitic packet size. Results show that the increase in the number density of small precipitates in the sample partitioned at 640 °C compensates for the increase in crystallographic packets size. The strength and ductility values are kept at a high level, but the impact toughness will decrease considerably.

scholarly journals Modified Manganese Phosphate Conversion Coating on Low-Carbon Steel

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1416
Author(s):  
Jakub Duszczyk ◽  
Katarzyna Siuzdak ◽  
Tomasz Klimczuk ◽  
Judyta Strychalska-Nowak ◽  
Adriana Zaleska-Medynska
Keyword(s):  
Low Carbon Steel ◽  
Microscopic Analysis ◽  
Metal Cations ◽  
Steel Structures ◽  
Xrd Analysis ◽  
Low Carbon ◽  
Destructive Effect ◽  
Electrochemical Tests ◽  
Manganese Phosphate ◽  
The Impact

Conversion coatings are one of the primary types of galvanic coatings used to protect steel structures against corrosion. They are created through chemical reactions between the metal surface and the environment of the phosphating. This paper investigates the impact that the addition of new metal cations to the phosphating reaction environment has on the quality of the final coating. So far, standard phosphate coatings have contained only one primary element, such as zinc in the case of zinc coatings, or two elements, such as manganese and iron in the case of manganese coatings. The structural properties have been determined using a scanning electron microscope (SEM), X-ray diffraction (XRD), and electrochemical tests. New manganese coatings were produced through a reaction between the modified phosphating bath and the metal (Ba, Zn, Cd, Mo, Cu, Ce, Sr, and Ca). This change was noticeable in the structure of the produced manganese phosphate crystallites. A destructive effect of molybdenum and chromium was demonstrated. Microscopic analysis, XRD analysis and electrochemical tests suggest that the addition of new metal cations to the phosphating bath affects the corrosion resistance of the modified coating.

Metallurgical Design of High Strength/High Toughness Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2084-2089
Author(s):  
Andrea di Schino ◽  
Mauro Guagnelli
Keyword(s):  
Impact Toughness ◽  
Yield Strength ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Steels ◽  
Main Concern ◽  
Microstructural Parameters ◽  
Fine Microstructure ◽  
The Impact ◽  
Strength And Toughness

The proper balance between yield strength, YS, and ductile to brittle transition temperature, DBTT, has been the main concern during development of high strength engineering steels and the effect of microstructure on impact toughness has attracted a great attention during the last decades. In this paper a review concerning the relationship between strength and toughness in steels will be presented and the effect of different microstructural parameters will be discussed, aiming toimprovesuch properties in designingnewhigh strength steels. Complex microstructures, obtained by quenching and tempering (Q&T) and thermo-mechanical (TM) processing are considered. The steels are low/medium carbon steels (C=0.04%-0.40%) with yield strength in the range YS=500-1000 MPa. Results show that the strength and the impact toughness behaviour are controlled by different microstructural parameters and not, as in the case of polygonal ferritic steels, by the same structural unit (the grain size) and that a “fine” microstructure is required in order to achieve high levels of both strength and toughness. The metallurgical design of high strength steels with toughness requirements is discussed using the same approach for both Q&T and TMCP processes.

scholarly journals Features of the formation of structure and mechanical properties in rolled products of various thicknesses from low-carbon microalloyed steel produced by casting and rolling complex

2021 ◽  
Vol 64 (9) ◽  
pp. 669-678
Author(s):  
V. V. Naumenko ◽  
K. S. Smetanin ◽  
А. V. Muntin ◽  
O. А. Baranova ◽  
S. V. Kovtunov
Keyword(s):  
Grain Size ◽  
Stress Concentrator ◽  
Microalloyed Steel ◽  
Rolling Direction ◽  
Large Angle ◽  
Low Carbon ◽  
Rolled Metal ◽  
Average Grain Size ◽  
Carbon Microalloyed ◽  
The Impact

The article considers results of the study of microstructure parameters effect on the impact strength in temperature range from 0 to –80  °C in 20  °C increments of Charpy samples with a sharp stress concentrator and Mesnager test pieces with a circular stress concentrator from rolled coils of low-carbon microalloyed steel with various thicknesses. The used roll products were produced in conditions of JSC “Vyksa Metallurgical Plant”. The tests were performed using optical and scanning electron microscopy. It is shown that with the same chemical composition and thermomechanical treatment modes, the metal of smaller thickness (6, 8 mm) is characterized by higher strength properties (on average, by 10 MPa for temporary resistance, by 30 MPa for yield strength) and a margin for viscous properties at negative temperatures at close values of grain score and average grain size corresponding to 10 – 11 numbers according to the State standard GOST 5639. The metal with a thickness of 12 mm has the lowest level of cold resistance, and the temperature of brittle transition is minus 50 °C. Structure of rolled products of various thicknesses has a variation in grain size. Rolled metal of smaller thicknesses have a smaller grains corresponding to number 14, rolled metal of larger thicknesses has a larger grains corresponding to number 8. By conducting electron microscopic studies using the backscattered electron method, it was found that a greater number of large-angle boundaries, which are barriers for brittle cracks propagation, are observed in the 6, 8 mm thick rolled products. The constructed orientation maps of the microstructure showed the presence of pronounced deformation texture corresponding to the orientations <110>||RD (rolling direction) and (<113>...<112>)||RD for rolled products with a thickness of 6 mm.

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