Zhangjiagang, China
Zhangjiagang, China

Time filter

Source Type

Fang F.,Nanjing Southeast University | Hu X.-J.,Nanjing Southeast University | Hu X.-J.,Jiangsu Sha Steel Group | Zhang B.-M.,Nanjing Southeast University | And 2 more authors.
Materials Science and Engineering A | Year: 2013

In this paper, extremely high strength was obtained in medium carbon steel having a carbon content of 0.35% by weight through cold drawing. Experimental results showed that the tensile strength of the steel increased by nearly three folds from the original value ~615. MPa to 1810. MPa corresponding to drawing strain of 3.0. To reveal the mechanisms that govern the strengthen increase, the microstructural evolution was analyzed during cold drawing, with respect to the change of the deformation resistance (measured by micro-hardness) of micro-constituents (i.e., primary or proeutectoid ferrite and pearlite) in the material. The proeutectoid ferrite became elongated and, at the same time, increasingly hardened while the pearlite maintained equiaxed shape after initial drawing. With the increase of the drawing strain, the pearlite was stretched parallel to drawing direction, accompanied by an increase in the 〈110〉 texture intensity and dislocation density in the ferrite phase. Under heavy drawing, a laminate structure formed, consisting of alternating pro-eutectoid ferrite and pearlite both parallel to the drawing direction. The 〈110〉 texture intensity in the ferrite phase became saturated as ε>1.2. High density dislocation zones further spread in the ferrite phase. The interlamellar spacing between ferrite and cementite phases in the pearlite decreased. Based upon these observations, mechanistic models were constructed to provide insight into the deformation and strengthening mechanisms of this steel. © 2013 Elsevier B.V.


Hu X.,Nanjing Southeast University | Hu X.,Jiangsu Sha Steel Group | Wang L.,Jiangsu Sha Steel Group | Fang F.,Nanjing Southeast University | And 3 more authors.
Journal of Materials Science | Year: 2013

The structural and mechanical factors that control the torsion fracture behavior of cold-drawn eutectoid steel wires are examined. Two types of the fracture are identified; namely, flat- and cleavage-type. Torsion cracks are found to initiate in ferrite and propagate along the ferrite/cementite interface. The shear stress distribution within the wires is affected not only by the applied torque, but also by the residual stress. The maximum shear stress occurs halfway from center to the surface, where the cracks initiated. The growth of torsion cracks is sensitive to the orientation of cementite lamellas in pearlite grains. The influence of thermal history on the occurrence of cleavage fracture is ascertained, with the assistance of atom probe. It shows that the cleavage fracture results from a decrease in dislocation mobility, caused by thermally activated diffusion of carbon atoms into ferrite. © 2013 Springer Science+Business Media New York.


Fang F.,Nanjing Southeast University | Zhao Y.,Nanjing Southeast University | Zhou L.,Nanjing Southeast University | Hu X.,Jiangsu Sha steel Group | And 2 more authors.
Materials Science and Engineering A | Year: 2014

In this paper, microstructure and mechanical properties of cold drawn pearlitic steel wires were investigated by combining SEM and XRD analysis with tensile testing. Experimental results show that the tensile strength of wires increases from 1250. MPa to 3280. MPa with increasing drawing strain of 3.2. When the strain is greater than 2.0, the rate of work hardening has increased rapidly. The original steel rods have a weak 〈110〉 texture. With the increase of the drawing strain, the orientation of 〈110〉 intensified and became dominant. The 〈110〉 texture became saturated when drawing strain reaches 2.0. In addition, for low strain (. ε=1.1) pearlite wires, the intensity of 〈110〉 texture decreased sharply after austenitization at 820. °C for 5. min. With the increase of austenitization time, the intensity of 〈110〉 texture decreased continually, and eventually no dominant texture existed. For high strain (. ε>1.6) steel wires, though the intensity of 〈110〉 texture decreased in the beginning, the 〈110〉 texture remained dominant after prolonged austenitization treatment. The observed texture inheritance can be exploited in the development of steel wires with unprecedented strength. © 2014 Elsevier B.V.


Fang F.,Nanjing Southeast University | Zhou L.,Nanjing Southeast University | Hu X.,Jiangsu Sha Steel Group | Zhou X.,Nanjing Southeast University | And 5 more authors.
Materials and Design | Year: 2015

Pearlitic steel rods with inherited texture (IT) were prepared from pre-drawing followed by austenitization treatment. Effects of inherited texture on the microstructure and mechanical properties of cold-drawn pearlitic wires were investigated. The 〈1. 1. 0〉 texture of ferrite increased with drawing strain and became saturated when strain reached about 2.0. However, wires with IT showed a higher 〈1. 1. 0〉 texture intensity. The ratio of bent over straight pearlite colonies in wires with IT were about 20% lower than that of wire without IT in drawing. Additionally, Wires with IT showed a greater work hardening rate. Tensile strength of wires without IT increased from 1260. MPa to 3010. MPa as drawing strain increased to 3.5, while wire with IT exhibited an 7% increase in tensile strength (i.e., up to 3230. MPa). Torsion angle of wires with IT were about 13% higher than that of wires without IT. Differential scanning calorimetry (DSC) analysis showed that wires with IT have higher thermal stability. © 2015 Elsevier Ltd.


Fang F.,Nanjing Southeast University | Zhao Y.,Nanjing Southeast University | Liu P.,Nanjing Southeast University | Zhou L.,Nanjing Southeast University | And 3 more authors.
Materials Science and Engineering A | Year: 2014

Nanostructural evolution of cementite lamellae in pearlitic steel wires subjected to cold drawing remains elusive, making it difficult to understand the origin of remarkable ductility in cementite. Using high-resolution transmission electron microscopy (HRTEM), the mechanisms underlying the inelastic deformation of cementite in pearlitic steel wires were examined and elucidated. Deformation of cementite in drawing should be included in two mechanisms: (1) Dislocation mechanism: deformation in low strain pearlite should rely on the movement of dislocation. Flat-crystal cementite was broken up into several different orientation cementite particles. (2) Grain rotation mechanism: the deformation mechanism should be by the rotation of cementite particles. Cementite still keeps lamellar shape, but it was divided into a multilayer structure: central nano-crystal and outermost amorphous cementite. © 2014 Elsevier B.V.


Hu X.-J.,Nanjing Southeast University | Hu X.-J.,Jiangsu Sha Steel Group | Zhang B.-M.,Nanjing Southeast University | Chen S.-H.,Jiangsu Sha Steel Group | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2013

The structure and formation process of oxidation on high carbon steel were investigated with the aid of X-ray diffraction (XRD), scanning electron microscope (SEM) and Laser Raman spectroscopy (LRS). The oxide scale formed comprised a three-layer structure, similar to that formed on pure iron and low-carbon steel. For the high carbon steel, however, the scale was essentially a two-layered because of the low proportion of hematite (Fe2 O3) formed. The scale thickness increased with the temperature and time of oxidation. The rate of scale thickening rapidly increased above 900 °C, at which the rate was particularly fast in the first 20 s of oxidation. The proportion of wüstite (Fe1-y O) increased with time and temperature of oxidation, while the magnetite (Fe3 O4) remained constant at about 2 μm. © 2013 Central Iron and Steel Research Institute.


Fang F.,Nanjing Southeast University | Hu X.-J.,Nanjing Southeast University | Hu X.-J.,Jiangsu Sha Steel Group | Chen S.-H.,Jiangsu Sha Steel Group | And 2 more authors.
Materials Science and Engineering A | Year: 2012

Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13. mm to 6.9. mm in diameter. Thermal annealing at 450 °C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780. MPa to 1940. MPa for annealing <5. min, and then decreased. Tensile strength became constant for annealing >10. min. Elongation of wires decreased for annealing <2.5. min, and then recovered slightly. It approached a constant value for annealing >5. min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5. min, and then decreased rapidly. Its value became constant when the hold time is greater than 10. min. Lamellar cementite began to spheroidize at annealing >2.5. min, starting at the boundary of pearlitic grains, and moving inward. A broad exothermic peak was found at temperatures between 380 °C and 480 °C, resulting primarily from the spheroidization of lamellar cementite, which is responsible for the degradation of torsion property of cold-drawn wires. © 2012 Elsevier B.V.


Wang X.-D.,Dalian University of Technology | Yao M.,Dalian University of Technology | Zhang L.,Control Iron and Steel Research Institute, China | Zhang X.-B.,Jiangsu Sha steel Group | Chen S.-H.,Jiangsu Sha steel Group
Journal of Iron and Steel Research International | Year: 2013

Lubrication and friction between the mould and strand are strongly influenced by mould oscillation, and play an important role in slab quality and operating safety during continuous casting processes. Investigation of mould oscillation is therefore essential for getting a better online control of the mould processes. A feasible approach for the development and optimization of mould oscillation was put forward, which combined online measurement of mould friction, design of negative oscillating parameters and evaluation for powder consumption. Three different control models including sinusoidal and non-sinusoidal oscillation for mould oscillations were developed to investigate and evaluate the effects of oscillation on mould friction and powder lubrication. For the purpose of investigating mould friction between mould and strand, online measurement was carried out on a slab continuous caster equipped with a hydraulic oscillator. Also the comparison of the mould friction in sinusoidal and non-sinusoidal mould oscillation was made for subsequent analysis. The industrial experiment result shows that the combination of inverse control model and non-sinusoidal oscillation mode will contribute to the proper powder consumption, leading to a suitable effect of friction force on strand surface, especially for high speed continuous casting. The proposed method provides reliable basis for guiding and optimizing mould oscillation among control models, sinusoidal oscillation and non-sinusoidal oscillation. © 2013 Central Iron and Steel Research Institute.


Wang H.,Jiangsu University | Zhang T.,Jiangsu University | Zhu H.,Jiangsu University | Zhu H.,Jiangsu Sha steel Group | And 3 more authors.
ISIJ International | Year: 2011

Fluorite is widely employed as fluxing agent in metallurgy flux, which inevitably leads to serious fluorine pollution. In this work, B 2O3 is used as fluxing agent of CaO-based refining flux to substitute for CaF2 so as to decrease the melting temperature and to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature, viscosity and desulfurization capacity of CaO-based refining flux were investigated. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and Al2O3. For the high basicity CaO-based refining flux (mass ratio of CaO/SiO2 is 5.0-8.75), when CaF2 is substituted with B2O3, the melting temperature can be decreased remarkably. Especially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in range of 1.1-4.0 and 5.25-8.0, respectively, the flux melting temperature is lower than 1 300°C. At the same time, the temperature range, in which the flux viscosity is low, is expanded as well as the stability of flux viscosity varying with temperature is improved obviously. These variations of flux properties are favorable for refining process. The results of experiments on sulphur partition equilibrium between metal and flux indicate that the desulfurization capacity of flux can be improved markedly when CaF2 is substituted with equal mass of B2O3. When 4 mass% B2O3 is employed as fluxing agent and the mass ratio of CaO/Al2O3 is in the range of 1.5-7.0, the final sulfur content of metal can be controlled lower than 0.004%. © 2011 ISIJ.


Nie W.,University of Science and Technology Beijing | Nie W.,Jiangsu Sha Steel Group | Shang C.,University of Science and Technology Beijing | Wu S.,University of Science and Technology Beijing | And 3 more authors.
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2012

Solute and precipitates of Nb can effectively affect stastic recrystallization and recovery of austnite in steels during hot rolling process. However, more research is concerned about the role of Nb precipitation on the strain accumulation in finish rolling process, the solute drag effect of Nb is neglected comparing with precipitates. In this paper, the stress-relaxation curves of the low C high Mn steels with different Nb content were investigated by thermal simulation test, the evolution of dislocation and its interaction with Nb solute and precipitate during recovery process of deformed autentie in a Fe-40%Ni-0.1%Nb (mass fraction) modle steel was also studied by transmission electron microscopy (TEM). Thereby, a theoretical model about recovery of deformed austenite was developed according to the slip of dislocations and the solute drag. The values calculated by the model are consistent with the experimental results and the metallurgic principles. It is shown that both solute and precipitation of Nb can slow down the recovery and enhance the strain accumulation. The Nb solute drag can increase the activation free energy of the recovery U 0 and decrease the activation length. It is believed that for Nb micro-alloyed steels with low C and high Mn, the strain accumulation during finish rolling process would be relied on the Nb solute drag effect in hot-strip mill, and both solute drag and precipitation pin effects in heavy plate mill. © right.

Loading Jiangsu Sha Steel Group collaborators
Loading Jiangsu Sha Steel Group collaborators