bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of the Columnar Grain Growth in IF Steels during Continuous Heat Cycles
Authors: Kaluba Wlodzimierz , Kaluba T.
Published: January 2010

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.
Bending Property of Liner Laser Irradiated Thin High Carbon Steel
Authors: Kawakami Hiroshi , Faisal Ahmad , Ozaki Hitoshi , Suzuki Jippei
Published: January 2010

Effect of liner laser irradiation on bending properties of thin high carbon steel plate was investigated in this study. Laser-transformed zone included solidification structure and quenched zone by laser irradiation was observed in cross section area of specimen by double-etching. Shape of laser-transformed zone changed significantly with changing of heat input. Deformation after laser irradiation occurred by the excess of heat input. Average area ratio of laser-transformed zone for normal bending specimen without deformation was cleared at each thickness. Sensitivity for laser deformation increased with decreasing of thickness. Three points bending test was executed to obtain Flexural load-deflection curve. Bending property of thin steel plate improved by laser liner irradiation and flexural load per unit deflection increased by suitable laser irradiation condition. Absorb energy of bending test also increased by existence of laser-transformed zone.
Effect of Martensite in Initial Structure on Bainite Transformation
Authors: Kawata Hiroyuki , Hayashi Kunio , Sugiura Natsuko , Yoshinaga Naoki , Takahashi Manabu
Published: January 2010

Lath-shaped upper bainite structures play a very important role in many high-strength steels (HSSs) and ultra high-strength steels (UHSSs). Although bainite transformation is strongly affected by the initial structure, the effect of the second phase in a multi-phase structure is yet to be clearly understood. It is significant for the advancement of UHSS to study this effect. The aim of this study is to clarify the effect of martensite, which forms before bainite, in Fe-0.2C-8Ni alloy. The bainite transformation from an austenite and martensite dual-phase structure is faster than that from single-phase austenite and the nucleation of bainitic ferrite laths are accelerated around martensite. This effect of martensite on bainite kinetics is equivalent to that of polygonal ferrite when their volume fractions are almost the same. This suggests that the boundary between martensite and austenite is a prior nucleation site of bainitic ferrite. Martensite also affects the crystallographic features of bainite. The orientations of bainitic ferrite laths tend to belong to the same block with martensite adjacent. This tendency intensifies with an increase of the transformation temperature of bainite, resulting in the formation of huge blocks consisting of bainitic ferrite and martensite laths at high temperatures (693K and 723K). In contrast, at a low temperature (643K), bainitic ferrite laths belong to same packet as martensite and have several orientations. This change of crystallographic features with transformation temperature can explain with the driving force of the nucleation of bainitic ferrite.
Effects of Manganese Content and Heat Treatment Condition on Mechanical Properties and Microstructures of Fine-Grained Low Carbon TRIP-Aided Steels
Authors: Kim Sung Joon
Published: January 2010

The mechanical properties and microstructures of alternative low carbon TRIP-aided steels in which manganese contents mediate between conventional low-alloyed TRIP-aided steels and TWIP steel have been investigated. A variety of microstructures, from a single austenite phase to multiple phase mixtures, was attained according to chemical compositions as well as heat treatment schedule. By means of reverse transformation of martensite combined with controlled annealing, a remarkable grain refinement being responsible for stabilization of austenite could be achieved. In case of the duplex (+ ) microstructures in 6Mn and 7Mn alloys, large amount of retained austenite more than 30 % contributed to substantial improvement of ductility compared to the conventional TRIP-aided steels having similar tensile strength level. In nearly single austenitic 13Mn alloy, the annealed sheet steel exhibited high tensile strength of 1.3 GPa with sufficient ductility due to the stain induced martensite transformation of fine grained austenite.
The Effect of Cooling Rate on the Damage Micromechanisms of DP Steels
Authors: León-García Orlando , Petrov Roumen H. , Kestens Leo A.I.
Published: January 2010

The microstructural failure mechanisms of two DP steel sheets cooled with different cooling rates during their heat treatment are compared in the present study. The as-cold rolled DP steel sheets were annealed at intercritical temperature and cooled down with rates of 45°C/s (quenching) and 2 °C/s (slow cooling). Uniaxial tensile tests were carried out on samples from both sheets and the microstructure of undeformed samples and the broken tensile specimens was evaluated by optical microscopy, scanning electron microscopy and electron back-scatter diffraction technique. Although the grain size did not show significant differences, the amount and size of the constituents, e.g. martensite and bainite, differ between both alloys. Concerning the mechanical properties, the quenched material showed superior strength and ductility besides a less localized deformation at higher strains. The area fraction of voids in the broken specimens was low for both steels. In the slow cooled samples the nucleation of shear bands was on the large voids and cracks were observed along these shears bands. It was concluded that the detrimental effect of void nucleation on both steels is not only attributed to their null-carry capacity but more to the stress concentration close to the voids which gives rise to strain localization in the form of shear bands.
Effect of Coiling Temperature on Microstructure and Mechanical Properties of a Nb-V Microalloyed Steel
Authors: Olasolo M. , Uranga Pello , Rodriguez-Ibabe J.M. , López Beatriz
Published: January 2010

The effect of coiling temperature on the microstructure and mechanical properties of a Nb-V microalloyed steel was investigated. Controlled rolling followed by accelerated cooling and coiling was simulated by means of both, uniaxial compression, using a quenching and deformation dilatometer, and torsion. Specimens were reheated at 1250º for 5-10 min, then deformed at 1150°C, =0.3, and subsequently at 900°C, =0.4, followed by rapid cooling to a temperature between 450 and 700°C where coiling was simulated by holding the specimen for one hour at the selected temperature followed by a slow cooling to room temperature. Mechanical characterization was performed by means of hardness measurements and tensile tests, using tubular specimens machined from the torsion samples. It was found that decreasing the coiling temperature the ferrite-pearlite microstructure changed to ferrite-bainite, with a hardness peak reached for coiling at 600°C-650°C.
A Study of the Carbides in High-Speed Steel Rolls
Authors: Luan Yi Kun , Song Nan Nan , Kang Xiu Hong , Li Dian Zhong
Published: January 2010

Carbides in HSS roll were studied systematically. The results showed that there were two kinds of carbides in HSS roll, 1st and 2nd carbides. 1st eutectic carbides included the chrysanthemum-like MC mainly consisting of V and the plate-like M2C rich in Mo. 2nd carbides were complex carbides, concentrating Fe, Cr, Mo and V elements. The morphology, distribution and alloy concentration of the 1st eutectic carbides were studied using OM, SEM and EDS. During heat treatment, evolution of the 1st eutectic carbides was analyzed. It was found that the MC carbides had no change in morphology, components and distribution, while the M2C carbides decomposed to M6C and MC.
In order to improve the properties of HSS, a method of increasing solidification rate was defined to refine the eutectic carbides. After refinement, the eutectic carbides distributed both along the grain boundaries and inside the grains.
Microstructure and Mechanical Properties of Low Carbon Al-Killed Steels after Ultra-Rapid Annealing Cycles
Authors: Massardier-Jourdan Véronique , Ngansop A. , Fabrègue Damien , Merlin Jacques
Published: January 2010

Ultra rapid annealing cycles were conducted on two low carbon Al-killed steel sheets differing mainly by their coiling temperatures (600°C or 700°C). For the lowest coiling temperature, the mean grain size of the steel was found to gradually decrease with an increase of the annealing temperature from 700°C to 920°C. A more complex grain size evolution was detected in the case of the steel coiled at high temperature. This led us to the conclusion that the size and the distribution of the iron carbides present before annealing, which is mainly governed by the coiling temperature, plays a very important role on the mechanisms involved in the grain refinement of extra-mild steels during ultra-rapid annealing cycles.
Effect of Mg Addition on the Mechanical Properties of Rapidly Solidified Al-Mn Alloys at Elevated Temperatures
Authors: Sugamata Makoto , Tomioka Akio , Kubota Yousuke
Published: January 2010

With an aim of clarifying the strength of rapidly solidified P/M materials strengthened by solid solution of Mg and dispersion of transition metal compounds at elevated temperature, Al-2mass%Mn, Al-4mass%Mn and Al-6mass%Mn alloys with varied Mg additions of 0, 1 and 3 mass% were prepared by rapid solidification techniques. Rapidly solidified (RS) flakes were produced by remelting alloy ingots in a graphite crucible, atomizing the alloy melt and subsequent splat-quenching on a rotating water-cooled copper roll under argon atmosphere.　The RS flakes were consolidated to the P/M materials by hot extrusion after vacuum degassing. Cast ingots of these alloys were also hot-extruded under the same conditions to the I/M as reference materials. Metallographic structures and constituent phases were studied for the P/M and I/M materials by optical microscope and X-ray diffraction. Mechanical properties of as-extruded and annealed P/M materials and as-extruded I/M materials were examined by tensile test at room and elevated temperatures under various strain rates.
Uniform dispersion of fine intermetallic compounds (Al6Mn) was observed in all the as-extruded P/M materials. Added Mg was present as the solute in I/M and P/M materials alloy even after annealing. The P/M materials containing Mg exhibited higher hardness and strength at room temperature, than those without Mg. It was considered that both solid solution of Mg and dispersion of intermetallic compounds were contributing the hardness and strength increase in the rapidly solidified Al-Mn-Mg alloys. Tensile strength increases with increasing amount of Mg in I/M materials at all testing temperatures. However, strength of as-extruded P/M materials decreases with addition of Mg at 573K and 673K. Thus the positive effects of Mg additions on tensile strength of as-extruded P/M materials disappeared at higher testing temperature. Tensile strength of annealed P/M materials in which dislocation density decreased and compound particle coarsened increased with addition of Mg at elevated temperatures.
Alloying Effects on Reverse Transformation to Austenite from Pearlite or Tempered Martensite Structures
Authors: Miyamoto Goro , Li Zhao Dong , Usuki Hirokazu , Furuhara Tadashi
Published: January 2010

Reverse transformation has been frequently used to refine austenite grain size for refining ferrite, pearlite and martensite structures. However, kinetics and microstructure change during reverse transformation to austenite has not been examined systematically compared with the austenite decomposition reaction. Therefore, alloying effects of 1mass% Mn, Si and Cr on reverse transformation kinetics from pearlite and tempered martensite structures in Fe-0.6mass%C alloys were investigated in this study. Vickers hardness of all the specimens increases with increasing holding time at 1073K because reversely-formed austenite transforms to martensite by quenching. In the reverse transformation from pearlite structure, the kinetics of reverse transformation is hardly changed by the Mn addition while Si and Cr additions delay it. Kinetics of reverse transformation from tempered martensite structure becomes slower than from the pearlite structure in all the alloys. In particular, retarding effect by the Cr addition is most significant among those elements.
Microstructure and Toughness of 1000 MPa High Strength Weld Metal
Authors: Du Wan Sheng , Peng Yun , Xiao Hong Jun , He Chang Hong , Tian Zhi Ling
Published: January 2010

Welding of 1000 MPa high strength alloy steel is difficult because of its welding cold cracking sensitivity and the difficulty in maintaining high joint toughness. In this paper the effects of alloy elements on welding cracking tendency are analyzed, and measures to prevent cold crack are proposed. Welding wires with high strength was deposited into weld metal and welded into joint. Tensile test, micro-hardness test and Charpy impact test were used to evaluate the strength and toughness of weld metal and heat affected zone. Optical microscope, transmission electron microscope and scanning electron microscope were used to analyze the microstructure. It is shown that the weld metal mainly consists of lath martensite, lath bainite, and residual austenite which exists between the laths. The strength of weld metal increases in a small degree with increasing carbon equivalent and its toughness and ductility are not related to carbon equivalent. The toughness and ductility are much sensitive to nonmetallic inclusions. The welded joint has tensile strength of higher than 1000 MPa when welded at heat input of 11 kJ/cm and 15 kJ/cm and the mechanical properties are little influenced by the amount of heat input in this range. The whole welded joint has good comprehensive properties.
OIM Analysis of Microstructure and Texture of a TRIP Assisted Steel after Static and Dynamic Deformation
Authors: Petrov Roumen H. , Bouquerel Jérémie , Verbeken Kim , Kestens Leo A.I. , Verleysen Patricia , Houbaert Yvan
Published: January 2010

TRIP-assisted steel with a composition of 0.2%C, 1.6%Mn, 1.5%Al was studied in the undeformed state, after the application of 10 and 30 % static tensile strain parallel to rolling the direction of the sheet and after dynamic (Hopkinson) fracture test. Detailed examination of the microstructure and microtexture by means of electron backscattered diffraction (EBSD) was carried out in order to quantify the microstructural constituents and to study the strain distribution. The microtexture evolution and the distribution of the specific texture components between the BCC and FCC phases were studied as a function of the external strain and the strain mode-static or dynamic. The strain localization and strain distribution between the structural constituents were quantified based on local misorientation maps. The full constraint Taylor model was used to predict the texture changes in the material and the results were compared to the experimental findings.
Comparing the local misorientation data it was found that at low strains the ferrite accommodates approximately 10 times more deformation than the retained austenite. The strain localizes initially on the BCC-FCC phase boundaries and is then spread in the BCC constituents (ferrite and bainite) creating a deformation skeleton in the BCC phase.
It was found that the observed texture changes in the measured retained austenite texture after deformation do not correspond exactly to the model prediction. The austenite texture components which were predicted by the Taylor model were not found in the measured austenite texture after deformation which means that they are first transformed to martensite, which is considered as an indication for the selective transformation of austenite under strain.
Effects of Electromagnetic Purification on Properties of Al-RE Rod for Electrical Purpose
Authors: Sun Bao De , Shu Da , Wang Jun
Published: January 2010

An electromagnetic purification system was installed to process molten aluminum in an Al-RE rod continuous casting and hot rolling line. The variation of inclusion concentration in rod samples with and without electromagnetic purification was detected via quantitative metallography. The tensile strength and electrical resistivity of as-rolled rods as well as subsequently cold drawn wires were also tested. Results show that a 61% additional improvement of removal efficiency was achieved by electromagnetic purification other than ceramic foam filtration. The inclusion concentration in the rods has negligible impact on electrical resistivity of samples and the deformation restricts the fluctuation of electrical properties apparently. The UTS of drawn wires with electromagnetic purification improves by 3%-5% as compared with those with filtration only, while the variation of inclusion concentrations has little influence on the UTS of as-rolled rods. A negative linear relationship between the logarithm of UTS and the logarithm of inclusion area fraction for cold-drawn samples is also obtained.
Mechanical Properties of a Medium Carbon Low Alloy Steel Processed by Two Step Austempering Process
Authors: Putatunda Susil K. , Deokar Abhijit , Bingi Gowtham
Published: January 2010

A new bainitic steel with a combination of exceptionally high yield strength and fracture toughness has been developed. This steel has been synthesized by austempering a medium carbon low alloy steel by a novel two-step austempering process. The influence of this two-step austempering on the microstructure and the mechanical properties of this new steel have been examined.
Influence of V and N on Transformation Behavior and Mechanical Properties of Medium Carbon Forging Steels
Authors: Radović Nenad , Koprivica Ankica , Glišić Dragomir , Fadel Abdunnaser , Drobnjak Djordje
Published: January 2010

The influence of vanadium and nitrogen on microstructure and mechanical properties of medium-carbon steels has been studied by means of metallography and mechanical testing. Vanadium addition to the low nitrogen steel suppresses the formation of ferrite-pearlite following the low reheating temperatures and microstructure consists of bainitic sheaves. Increasing nitrogen at the same vanadium level promotes the acicular ferrite formation. For high reheating temperatures, dominantly acicular ferrite structure in both the low nitrogen and the high nitrogen vanadium steels is obtained. The results suggest that vanadium in solid solution promotes the formation of bainite, whereas the effect of nitrogen is related to the precipitation of VN particles in austenite with high potency for intragranular nucleation of acicular ferrite and to the precipitation of V(C,N) particles in ferrite with high potency for precipitation strengthening. Addition of both vanadium and nitrogen considerably increases the strength level, while CVN20 impact energy increases on changing the microstructure from bainitic ferrite to the fine ferrite-pearlite and acicular ferrite.
The Complexity of the Microstructural Changes during the Partitioning Step of the Quenching and Partitioning Process in Low Carbon Steels
Authors: Santofimia Maria Jesus , Zhao Lie , Takahama Yoshiki , Sietsma Jilt
Published: January 2010

The quenching and partitioning (Q&P) process is a novel heat treatment for the development of advanced high strength steels that is raising an elevated interest by steel makers and steel researchers around the world. The reason is that reported results on mechanical properties, showing promising levels of forming and strength, are proving this new type of steel as a serious competitor of TRIP, DP and martensitic steels. The Q&P heat treatment consists of an initial partial or full austenitisation, followed by a quench to form a controlled amount of martensite and an isothermal treatment to partition the carbon from the martensite to the austenite. Although the path of the heat treatment is simple, the investigations have shown that the evolution of the microstructure during the application of the Q&P process is rather complicated. Processes occurring during the partitioning step, such as the migration of the interfaces, the carbon accumulation near the austenite interfaces and the carbon diffusion through ferrite, have strong effects on the resulting microstructure. In this work, the most important microstructural changes found during the application and simulation of the partitioning step of the Q&P process are analysed and discussed. Procedures to control the microstructure development in the application of the Q&P process are proposed.
Friction Stir Processing (FSP) of Cast Metals: Microstructure – Property Relationships in NiAl Bronze and AA5083
Authors: McNelley Terry R. , Swaminathan Srinivasan , Sarath Menon E. , Su J.Q.
Published: January 2010

Parameters for multi-pass FSP include the pattern of tool traverse and step-over distance between successive passes. Multi-pass FSP was conducted on as-cast NiAl bronze and as-cast AA5083 in order to modify stir zone (SZ) microstructures and mechanical properties. Highly refined and homogeneous SZ microstructures may be produced by FSP. Refined and equiaxed grain structures reflect recrystallization during FSP; mechanisms leading to homogenization by redistribution of microstructure constituents remain to be determined. Refined microstructures exhibit enhanced ambient-temperature properties and superplasticity at elevated temperatures.
The High Nb Content Microalloying Approach for Developing High Performance Structural Steel
Authors: Li Xiu Cheng , Shang Cheng Jia , Xia Dian Xiu , He Xin Lai
Published: January 2010

Two kinds of ULCB steel were designed with different Nb content. The yield strength of the steel which was made by adding 0.09%Nb, TMCP (Thermo Mechanical Controlling Processing) and tempering can achieve more than 900MPa. As compared with 0.05%Nb steel, adding 0.09%Nb can refine the austenite grain significantly. Through the analysis by TEM and EDX, a large amount of Nb precipitation particles can be observed in the steel with 0.09% Nb tempered at 650°C for 1h and these particles are generally small than 20nm.
The Formation of Multiphase Microstructures in Low-Alloy Steel
Authors: Sietsma Jilt
Published: January 2010

Although relatively simple in its chemical composition, low-alloy steel can form in a wide variety of microstructures, which directly implies that the (mechanical) properties of the material can vary strongly. Mankind has been using this to his advantage for ages, but the requirements for modern production and use of the material necessitate an ever better insight in the formation of these microstructures. Newly developed steel grades like DP-steel (Dual-Phase) or TRIP-steel (Transformation-Induced Plasticity) consist of several of the well-known phases ferrite, bainite, martensite, austenite, which need to be carefully balanced in their amount, composition and morphology to attain the desired material properties. An overview is given of the basic principles of microstructure formation in low-alloy steel, and the implications for several types of multiphase steel microstructures, in relation to the mechanical properties, are discussed.
Evaluation of Hydrogen Embrittlement for High Strength Steel Sheets
Authors: Toji Yuki , Takagi Shusaku , Yoshino M. , Hasegawa Koh , Tanaka Yasushi
Published: January 2010

Steel sheets for automobiles are usually formed into various parts by cold working. Therefore, plastic strain introduced by the cold working must be considered as a factor affecting the hydrogen embrittlement in addition to the applied stress and the content of diffusible hydrogen entered into steels, which are considered as factors in the studies of high strength steel bolts. However, there are few detailed reports investigating the influence of these factors on hydrogen embrittlement of steel sheets quantitatively. In this study, the influence of plastic strain, as well as stress and diffusible hydrogen content, on hydrogen embrittlement of steel sheet was quantitatively studied to evaluate the hydrogen embrittlement susceptibility of steel sheet by using an 1180 MPa grade cold rolled dual phase steel sheet. Plastic strain was introduced by U-shape bending, and stress was applied by tightening the bent specimen with a bolt. Then, hydrogen was introduced by dipping in hydrochloric acid, and the time to fracture and the content of diffusible hydrogen entered into steel during dipping were investigated. The fracture was promoted by severe deformation near the bending limit, and it seemed to be caused by the presence of micro cracks and/or micro voids. The hydrogen cracking conditions region of the steel sheet were mapped in the three-dimensional space with the axes of applied strain, applied stress and diffusible hydrogen content. It was considered that the evaluation of the risk of delayed fracture of automotive parts made of the steel sheet under service environment was possible by a comparison of the 3D map and the service conditions of the parts.
Formability of Ultrafine Grained Steel
Authors: Torizuka S. , Muramatsu Eijiro
Published: January 2010

Ultrafine grain refinement to 1 m deteriorates the uniform elongation in the tensile tests of steels. Such loss of ductility has been argued to be an inherent feature of the ultrafine-grained steels. While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. Ultrafine grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling and evaluated for their stress-strain behavior along with the reduction in area. It was found that the reduction in area- tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to bainitic steels for all materials tested in the present study. Formability of ultrafine grained steel is examined by applying to make a micro screw. Good formability was verified by this process.
Development of 780MPa Grade Steel Plate by Microstructural Control Containing M-A through the On-Line Heating Process
Authors: Ueda Keiji , Suzuki Shinichi , Mitao Shinji , Shikanai Nobuo , Ito Takayuki
Published: January 2010

High strength steel plates with 780MPa in tensile strength, suitable for building construction use, have been developed. The steel plates provide excellent combination of high strength, toughness, deformability and weldability. The key technology to obtain the excellent combination in mechanical properties of the steel is the microstructural control of M-A (martensite-austenite constituent) and the bainitic ferrite dual-phase structure, through the on-line heat treatment immediately after the accelerated cooling in Thermo-mechanical control process (TMCP). The developed steel plates have microstructure of fine M-A dispersed in the bainitic ferrite matrix. Basic metallurgical research revealed that the transformation behavior and microstructural morphologies were varied with the cooling stop temperature before the on-line heating, and the on-line heating temperature itself.
Trial production of the developed 780MPa grade steel plates was also carried out with the plate mill. The obtained plates showed the satisfactory combination of high strength, low yield ratio, toughness.
Formability and Correlation between Formability Indices of Al-0.9Mg-1.0Si-0.7Cu-0.6Mn Alloy for Automotive Body Sheets
Authors: Tian Ni , Zhao Gang , Zuo Liang , Liu Chun Ming
Published: January 2010

The texture, the formability and the correlation between formability indices of Al-0.9Mg-
1.0Si-0.7Cu-0.6Mn alloy for automotive body sheets subjected to solid solution, T4, annealing treatment and artificial aging at 443k for different time were investigated by orientation distribution functions(ODF) analysis, tensile and cupping test, FLD measurement and regression analysis method. The results showed that the textures of cold rolled alloy sheets consist mainly of copper and brass orientations, which are transformed into the texture mainly containing {001}<310> orientation after recrystallization, and aging treatment has little influence on the recrystallization texture. The formability of alloy sheets subjected to solid solution, T4 and annealing treatment is similar, however, the formability was observably deteriorated after aging at 443k. The correlation between uniform elongation δu and FLD0 is the most remarkable in all the given formability indices, the correlation between strain-hardening exponent n and the FLD0 take second place, while there is no correlation between plastic strain ratio r and FLD0. The correlation between reduction of area ψ and cupping value IE is distinct, while ψ and IE have little correlation with FLD0.
Effect of Hot and Cold Rolling on Grain Size and Texture in Fe-Si Strips with Si-Content Larger than 2 wt%
Authors: Gomes Edgar , Schneider Jürgen , Verbeken Kim , Hermann Harti , Houbaert Yvan
Published: January 2010

The crystallographic texture and grain size have a strong influence on the magnetic properties of FeSi alloys. These microstructural parameters are determined by the thermo-mechanical processing of the material. Here, some recent results on FeSi-alloys with variable Si-content and without phase transformation are presented. Hot rolling conditions were varied in broad interval of parameters and afterwards, the samples were cold rolled and annealed. After the different processing steps, the samples were characterized by optical microscopy, X-ray diffraction and Electron BackScatter Diffraction (EBSD) in order to evaluate the texture, grain size and the homogeneity of the structure through the thickness. This allowed to study the evolution of the intensity of the favourable magnetic texture components during processing.
Control of the Austenite Recrystallization in Niobium Microalloyed Steels
Authors: Vervynckt Stephanie , Verbeken Kim , Thibaux Philippe , Liebeherr Martin , Houbaert Yvan
Published: January 2010

The use of heavy gauge steel sheets for structural applications very often requires a combination of high yield strength and adequate toughness. The most cost effective way to realize a high yield strength and a high ductility in a low alloyed steel is grain refinement. In industrial practice, this refinement is realized by controlled processing. This process consists of controlling the slab reheating temperature, applying a large amount of hot deformation below the non-recrystallization temperature (Tnr) and accelerated cooling. A better knowledge of Tnr could optimize the process and the best mechanical properties could be reached against the lowest cost. Tnr can be raised by the addition of microalloying elements such as Nb. Nb can retard the static recrystallization of austenite at low temperatures either by solute drag or by precipitation pinning. In this study, the recrystallization behavior of five Nb-microalloyed model alloys with various Nb contents, was evaluated by double hit compression tests. Further, the precipitation state of the materials was investigated experimentally by Inductively Couples Mass Spectroscopy and X-ray Diffraction. The construction of recrystallization-time-temperature diagrams and precipitation-time-temperature diagrams showed that both mechanisms, i.e. recrystallization and precipitation, strongly influence each other.
Static and Impact-Dynamic Characterization of Multiphase TRIP Steels
Authors: Van Slycken Joost , Bouquerel Jérémie , Verleysen Patricia , Verbeken Kim , Degrieck Joris , Houbaert Yvan
Published: January 2010

In this study, results are presented of an extensive experimental program to investigate the strain rate dependent mechanical properties of various Transformation Induced Plasticity (TRIP) steel grades. A split Hopkinson tensile bar setup was used for the high strain rate experiments and microstructural observation techniques such as LOM, SEM and EBSD revealed the mechanisms governing the observed behavior. With elevated testing temperatures and interrupted tensile experiments the material behavior and the austenite to martensite transformation is investigated. In dynamic conditions, the strain rate has limited influence on the material properties. Yet an important increase is noticed when comparing static to dynamic conditions. The differences in strength, elongation and energy absorption levels observed between the investigated materials can be attributed to their chemical composition. Adiabatic heating during high strain rate deformation tends to slow down the strain induced martensitic deformation. The elongation of the ferritic and austenite constituents is found to be strain rate dependent and the strain induced martensitic transformation occurs gradually in the material.
Discontinuous Precipitation in a High-Nitrogen Austenitic Steel
Authors: Rovatti Ludovica , Montanari Roberto , Ucciardello Nadia , Mezzi Alessio , Kaciulis Saulius , Carosi Andrea
Published: January 2010

The discontinuous precipitation of a high-nitrogen (0.8 wt%) austenitic steel has been investigated after successive steps of heat treatment at two different temperatures (800 and 850 °C). After each step of heating the material has been examined by X-ray diffraction (XRD), optical microscopy (OM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and microhardness tests. The precipitation of Cr2N induces the formation of a secondary austenitic phase, leads to the redistribution of N between transformed and untransformed zones and to local variations of mechanical properties.
20 Years of Experience in Thin Slab Casting and Rolling State of the Art and Future Developments
Authors: Klinkenberg Christian , Bilgen C. , Boecher T. , Schlüter J.
Published: January 2010

Industrial thin slab casting and direct rolling processing started in 1989 with the world’s first CSP® plant at Crawfordsville (USA). Since this time CSP® and competing thin slab casting and direct rolling concepts have been developed to a standard process for hot strip production.
Typical features of the CSP® process are the homogeneous structural and mechanical properties all along the strip. Direct hot rolling of thin slabs may be followed by a well defined cooling pattern to produce fine-grained HSLA steel or multiphase hot strip on the runout table. The product range covers low carbon as well as medium and high carbon steel grades comprising IF-, HSLA-, API-, electrical- and multiphase steel grades.
CSP® processed thin hot strip is used for non-exposed parts and may substitute cold rolled strip. Hot strip from thin slab can be easily further processed to cold rolled and/or surface treated strip. Today process and material developments e.g. go for energy saving, rise in productivity, advanced surface requirements, HSLA and multiphase steel grades combining higher strength and ductility as well as multiphase steel grades for hot dip galvanizing.
Near-Net-Shape Casting of Steel - The Belt Casting Technology
Authors: Wans Jochen , Bausch J. , Hecken J. , Schlüter J.
Published: January 2010

The production of value added products made of high-alloyed Mn-, Al-, Si-steel grades is coupled to the casting technology. Conventional casting technologies will not fulfill the requirements concerning interaction between steel and casting flux as well as guiding as cast material without stress. Mechanical engineers are invited for further developments in the field of near-net-shape casting technologies to meet above mentioned demands.
The Belt Casting Technology seems to be the answer but has to document the potential for an industrial standard process. The main process characteristics of the casting machine are high casting speed, moving mould consisting of a conveyor belt and side dams, complete inertisation and horizontal material flow. The process is already common at the nonferrous metal industry. A labo-ratory caster for steel is located at Clausthal University of Technology.
Proper Design and Fabrication of Socket Welds for Use in Sour Service
Authors: Caligiuri Robert D. , Eiselstein Lawrence E. , Eastep L.N.
Published: January 2010

Socket welds are commonly used to assemble small-bore carbon steel process piping systems because they can be fabricated fairly quickly and are somewhat tolerant of field fit-up issues. In the most simplistic terms, these welds are made by inserting the pipe into a socket and then seal welding using gas tungsten arc welding around the gap between the outside pipe wall and the end of the fitting. This leaves a notch in the root of the seal weld that is open to the process fluid. This notch can act both as a stress riser and a crevice capable of concentrating chemical species. In many process applications, these socket weld notches do not cause any in-service problems. However, in the case of sour service, these notches can become problematic because of the potential for sulphide stress corrosion cracking (SSCC). For SSCC to occur, the right combination of stress, environment, and material susceptibility must be present. Therefore, for socket welds to be used in sour service without the risk of failure, these parameters need to be controlled by proper design and fabrication of the welded joint. Since a crevice is created as a natural by-product of a socket weld geometry, where the SSCC environment will be present, the parameter most readily controlled to minimize susceptibility to SSCC is the microstructure and residual stress of the weld filler metal. As will be shown, this resistance to SSCC can be accomplished by designing a welding procedure specification to include the combination of both a second pass seal weld and by post-weld heat treatment (PWHT). It will also be shown that a complete second pass is crucial to proper tempering and refining the microstructure of the root pass. Without this microstructural tempering and refining by the second pass, the root pass can still undergo SSCC even with subsequent application of PWHT. Examples of SSCC initiating from crack-like weld root defects caused by poor welding techniques and propagating into single-pass socket welds that had been subjected to PWHT will be presented.
Weld Pool Shaping and Microstructural Control Using Novel Computer Generated Holographic Optic Laser Welding of Steel and Stainless Steel
Authors: Higginson Rebecca L. , Gibson M. , Kell J. , Tyrer J.
Published: January 2010

This work considers the use of Holographic Optical Elements (HOEs) to shape the weld beam and control the microstructure of the weld bead. The beam profiles investigated are a standard Gaussian and an Offset Rugby Post produced by a HOE. Autogenous welds have been produced on plain carbon steel with the introduction of a nickel alloy filler powder, using different energy densities. Cross sections of the welds have been analysed in terms of the weld profile, weld pool shape, HAZ and the extent of the deposit/substrate mixing. Electron BackScatter Diffraction (EBSD) coupled with Energy Dispersive X-ray Spectroscopy (EDS) has been used to study the microstructures developed. The results have shown that by utilising HOE’s the weld pool shape can be modified so that a squarer profile can be obtained. The grain structure within the weld pool can be controlled such that a finer more equiaxed grain structure can be developed when compared with the coarse columnar grains seen with a Gaussian beam with a marked difference in the microstructures in the HAZ.
Consideration on the Toughness Requirement to the Austenitic Weld Metal in the LNG Storage Tanks Subjected to a Partial Height Hydro Test
Authors: Kawabata Tomoya , Konda Noboru , Arimochi Kazushige , Hirose Hitoshi , Muramoto Seiichi , Hirai Syuuichi
Published: January 2010

PD7777 published by British Standard Institute in 2000 proposes an additional fracture requirement to the main steel components of the low temperatures storage tank where a partial height hydrostatic test is allowed instead of the full height hydrostatic test required in BS 7777. In the PD7777 a high level (75J) of fracture toughness is required for the austenitic weld metal in 9%Ni steel plate to prevent the re-initiation of ductile fracture from the arrested brittle crack in the weld. This is to report a study that the J-Cv correlation of austenitic weld metal is determined by the experimental data obtained from the actual weld joints in 9%Ni steel plate in order to assess a rational toughness requirement to the austenitic weld metal employed in the 9% Ni made LNG storage tanks. From this study it is concluded that fracture toughness of 75J is too conservative and 50J is adequate. Further some FEM analyses were performed to verify the validity of the weld surrounded by the large amount of heterogeneous base metal in the yield strength distribution.
Mictrostructure and Mechanical Property Development in the Heat Affected Zone of Ultrafine Grained HSLA Steel
Authors: Modenesi Paulo José , Fajardo Rodrigo Ferreira , Santos Dagoberto Brandão
Published: January 2010

The ferrite grain refinement is a powerful mechanism to improve mechanical properties of low carbon steels providing steels with high strength and toughness at low temperatures and good weldability characteristics. The grain size refining is the only mechanism capable of to increase both mechanical strength and toughness. By refining the grain size of low carbon steel from 5 μm to 1 μm, its yield strength can be theoretically increased from 450 MPa to 650 MPa. In this way refining of ferritic grain is a very attractive processing route. This work aimed to investigate the characteristics of the heat affected zone of a microalloyed low carbon-manganese (0.11% C, 1.41% Mn, 0.028%Nb, and 0.012%Ti) steel with ultra-fine ferrite grain structure produced through quenching, warm rolling, followed by sub and intercritical annealing in laboratory. Four intercritical annealing treatments were performed after the same warm rolling processing to obtain different grain sizes with residual work hardening of the base metals. Specimens were TIG welded with 4 different levels of heat input. Cooling conditions during tests were recorded and used to evaluated the microstructure of the heat affected zones and their hardness. Cooling times between 800 and 500°C from 0.6 to 17 s were obtained. Martensite was observed in the heat affected zones for low-heat-input welding conditions. No softened zone was found in the heat affected zone in any of the performed tests.
In Situ Observation of Solidification Behavior during Welding
Authors: Komizo Yuichi , Terasaki Hidenori
Published: January 2010

Time-resolved X-Ray Diffraction (TRXRD) experments were carried out to identify the phase transformation during welding in-situ. For the martensitic steel weld with different chemical compositions, the solidification behavior was directly analyzed in the time-resolution of 0.01 seconds. The halo pattern from the weld pool gives basis to observe the phase transformation during solidification process of weld. Furthermore, the latest development of TRXRD system was outlined. The importance of detector area was discussed and brand-new TRXRD system in real and reciprocal lattice space was presented.
Characteristics of Laser Welded Joints of HDT580X Steel
Authors: Weglowski Marek S. , Stano Sebastian , Krasnowski Krzysztof , Łomozik Miroslaw , Kwiecinski Krzysztof , Jachym Robert
Published: January 2010

In the present study, the characteristics of Nd:YAG laser welded joints of 600 MPa DP steel (HDT580X), 2.4 mm in thickness, in respect of hardness, microstructures and mechanical properties were investigated. The test joints have been welded under a shielding gas on the stand for robotic Nd:YAG laser welding at the beam power of 1.5 kW and 2.0 kW. Three combinations of welding parameters were used: 2.0 kW - 2.1 m/min, 2.0 kW - 1.5 m/min and 1.5 kW - 1.2 m/min. Detailed examinations were performed on the joint welded at the highest speed. The microstructure was examined by the optical-, scanning- and transmission electron microscope. The heat affected zone (HAZ) was composed of ferrite, bainite and lath martensite, the weld contained lath martensite. The maximum hardness in the HAZ did not exceed 343 HV. The tensile strength of the welded joint was at the same level as that of the base material. The results of fatigue tests and residual stress measurement of laser welded DP steel joints are also presented. The fatigue strength of the welded joint is lower than that of the base material. The fatigue class FAT was determined, which is equal to 284 MPa - for the base material and 150 MPa – for the welded joint. By means of the modified hole drilling method the following residual stresses were measured: σmax = 573 MPa and σmin= -126 MPa.
Effect of Boron Carbide Addition on Wear Behaviour of Cobalt Based Hardfacings by Plasma Transferred Arc Process
Authors: Achar D.R.G. , Muthuswamy Kamaraj , Ganesh Bavisetty C. S.
Published: January 2010

Cobalt based alloy with the addition of 5 and 10 wt% boron carbide have been deposited by PTA process on stainless substrates effectively. The dry sliding wear performances of the coated alloys have been studied at room as well as at elevated temperatures. Addition of boron carbide to satellite 6 resulted in refinement of grains and formation of complex carbides and borides, which has lead to increase in hardness and wear resistance of the hardfaced layers. Superior wear resistance has been found to be at the composition of Stellite 6 with 5 wt% addition of boron carbide.
Friction Welding Structures of Carburized Steels
Authors: Mitelea Ion , Crăciunescu Corneliu Marius
Published: January 2010

Friction welding is one of the most reliable joining techniques for various materials due to a high reproducibility, lack of ecological treats and a relatively narrow thermomecanical affected zone. It offers multiple applicative opportunities in various fields – from automotive and manufacturing industries as well as for special destinations – leading to incontestable technical and economical advantages. However, the friction welding of materials with compositional and/or structural gradients is a critical problem due to the high probability of cracks occurrence, the formation of intermetallic phases that increase the brittleness and a high gradient for residual stresses.
The paper refers to the particularities of graded welds through which the rotational energy will be transformed by friction into heat in the surface layer with a certain structural morphology, as well as in the core with different characteristics. Experiments have been performed in order to assess the process parameters which provide the optimal friction energy for an adequate plastifiation of the materials. Macro and optical micrographic investigations corroborated with electron microscopy and hardness measurements provide information concerning the hardening of the thermomecanically affected zone and the formation of seam as result of expulsion of the carburized layer.