The Study on the Precipitation Behavior of the Second Phase Particles for Fine Grain and High Strength IF Steel

2012 ◽  
Vol 217-219 ◽  
pp. 411-414
Author(s):  
Hong Mei Zhang ◽  
Li Feng Qiao ◽  
Qin Bo Liu
Keyword(s):  
Grain Boundary ◽  
High Strength ◽  
Second Phase ◽  
If Steel ◽  
Precipitation Behavior ◽  
Extraction Replica ◽  
Carbon Extraction Replica ◽  
Fine Grain ◽  
Second Phase Particles ◽  
Precipitate Composition

The new type SFG HSS (super fine grain, high strength steel sheet) has been developed by adding solid-solution strengthening elements to conventional IF steel such as Si, Mn. The precipitation behavior of the second phase particles was observed and studied by a carbon extraction replica technique used transmission electron microscopy (TEM). The shape of the small second particles is similar to spherical and ellipse, the sizes of which are 10~30nm. It is seen that the particles are dispersed on the matrix. The precipitate composition of small particles is Nb (CN) and the precipitate composition of large particles is NbC examined by energy dispersive X-ray (EDX). It is noted that the yield strength is low as well as the tensile strength is high by the PFZ which is free of precipitate called precipitated free zone on the one side of the grain boundary. The results of microstructure shows that the second phase particles pinned on grain boundary not only can inhibit the grain growth, but also the grain can be fined.

The Study on the Precipitation Behavior of the Second Phase Particles for As-Hot Rolled Dual-Phase Nb-Bearing Steel

2011 ◽  
Vol 189-193 ◽  
pp. 626-629
Author(s):  
Zhang Hong Mei ◽  
Qiao Li Feng
Keyword(s):  
Bearing Steel ◽  
Second Phase ◽  
Dual Phase ◽  
Precipitation Behavior ◽  
Extraction Replica ◽  
Carbon Extraction Replica ◽  
Heating And Cooling ◽  
Second Phase Particles ◽  
The Matrix ◽  
Hot Rolled

The precipitation behavior of the second phase particles was observed and studied by a carbon extraction replica technique used transmission electron microscopy (TEM) for Nb-bearing dual-phase steel. It is found that there are more second phase particles on the surface than that of in the center of sample. The mainly smaller particle which sizes of is below 20nm show the shape of spherical and ellipse. The sizes of larger particles are range of 20nm~40nm and the shape of them present rectangle or ellipse. The particles are dispersed on the matrix and the particle boundary is clear. The precipitate composition of particles are all Nb(C、N) examined by energy dispersive X-ray (EDX). The results of microstructure shows that the second phase particles pinned on grain boundary not only can inhibited the grain growth, but also the grain can be fined during the heating and cooling course.

The Study on the Low Yield Strength for Super Fine Grain and High Strength Bearing Nb if Steel

2011 ◽  
Vol 335-336 ◽  
pp. 615-618
Author(s):  
Hong Mei Zhang ◽  
Li Feng Qiao
Keyword(s):  
Solid Solution ◽  
Yield Strength ◽  
Grain Boundary ◽  
High Strength ◽  
If Steel ◽  
Rolled Steel ◽  
Steel Sheets ◽  
Fine Grain ◽  
Cold Rolled ◽  
R Value

The cold rolling and simulative continuous annealing experiments after rolling were carried out in the laboratory on the base of super fine grain (SFG) steel sheet. The microstructure and the second-phase particles precipitated behavior were analyzed by the technology of OM, TEM and EDX. It is found that the fined Nb(C, N) can be formed by adding micro-alloy element Nb. It is noted that the yield strength is low as well as the tensile strength is high by the PFZ which is free of precipitate called precipitated free zone on the one side of the grain boundary. Contrast to the conventional IF steel, the super fine grain steel has super fine grains and gives excellent press-formability such as low yield strength, high r-value（the plastic strain ratio）. High strength cold-rolled steel sheets (HSS) with high formability have been developed in the last decade, in which the major strengthening method was solid-solution hardening with silicon, manganese and phosphorous [1-3]. When the IF steel is strengthened with the high amount of solid-solution elements, it becomes susceptible to the secondary work embrittlement because of the lack of grain boundary strength [4-6]. In this paper, High strength cold-rolled steel sheets (HSS) with high formability have been developed for the IF steel-bases. The grain refinement and precipitation hardening are achieved by means of the fine distribution of carbide under the appropriate combination of the relatively higher carbon content near 0.0070 mass% with niobium. As the result, this type of IF-HSS has been successfully developed to reach a higher r-value as compared with the conventional IF-HSS.

Texture, Microstructure and Second-Phase Particles in a Ti+P Interstitial Free (IF) Steel

2005 ◽  
Vol 495-497 ◽  
pp. 423-428 ◽  
Author(s):  
Q.W. Jiang ◽  
E.B. Zhao ◽  
J.G. Zhang ◽  
Y. Chen ◽  
Gang Wang ◽  
...  
Keyword(s):  
Cold Rolling ◽  
High Strength ◽  
Strain Ratio ◽  
Warm Rolling ◽  
Second Phase ◽  
Rolled Sheet ◽  
Interstitial Free ◽  
If Steel ◽  
Plastic Strain Ratio ◽  
Second Phase Particles

The microstructure of Ti+P IF steel were studied after warm rolling, cold rolling and recrystallization using X-Ray, TEM and SEM. The results show that the characteristics of warm rolled sheet are the same as that of the cold rolled, but the texture displays different characteristics in the subsequent cold rolling and recrystallization because of the numerous second-phase particles. In this work, a Ti+P IF steel sheet with high strength and plastic strain ratio was obtained.

Precipitation Behavior of the Second Phase Particles in Grain Oriented Silicon Steel Slabs under Different Reheating Conditions

2014 ◽  
Vol 906 ◽  
pp. 268-274 ◽  
Author(s):  
Xian Hong Chen ◽  
Chen Yi Zhu ◽  
Li Deng ◽  
Guang Qiang Li
Keyword(s):  
Grain Boundary ◽  
Volume Density ◽  
Silicon Steel ◽  
Second Phase ◽  
Precipitation Behavior ◽  
Soaking Time ◽  
Second Phase Particles ◽  
Steel Slabs ◽  
The Common ◽  
Average Size

The grain oriented silicon steel slabs were reheated at 1323K~1623K with different soaking time in this study. The precipitation behavior of the second phase particles in the steel slabs was investigated by using SEM/EDS combined with other analytic tools. The results show that the main precipitations in samples are MnS and AlN bearing a little of CuxS, and they frequently aggregate with each other by two or three types of precipitations. The quantities of the above three types of precipitations are up to 90% in each sample. These complex precipitations change into AlN bearing a little of CuxS or single AlN after being reheated. The shapes of MnS or AlN havent the common spherical or quadrilateral characteristic outline. There are a few of spherical or irregular shape inclusions such as SiO2, Al2O3, TiO2, CaO, CaS and their complex in the samples. Part of MnS or AlN can also grow around with these particles and then dissolves after being reheated. The sizes of the particles are main in the range of 0.05~0.2μm. There are no inclusions larger than 5.0μm in size observed in the fields of view. The volume density of the precipitations 0.05~0.2μm in size extracted from the quenched samples at 1523K using non aqueous solution electroextraction are 4.04×104/mm3, 4.73×104/mm3, 3.70×104/mm3, 3.33×104/mm3, 3.10×104/mm3and 1.56×104/mm3as the corresponding reheating time is 10min, 30min, 60min, 90min, 120min and 240min at 1523K respectively. The average size of them is 0.108μm. It is more precise to statistics the volume density of the particles in the steel by electrolysis extracting method than that of using metallogrphical analysis. No obvious microstructure variation was observed in the quenched samples after annealing different time. When the reheating temperature reaches 1523K and 1623 K, the grain size grows more easily and the grain boundary gets smoothly. The grain boundary of the samples becomes clear with the increase of the annealing temperature during the same annealing time. The reheating temperature in the present slab is chosen at 1523K and the reheating time is kept for 120 min, which will insure the particles in the slab to dissolve more completely and avoid grain growth abnormally at high temperature.

Research and Empoldering of High Strength Weathering Steel S450EW

2014 ◽  
Vol 937 ◽  
pp. 125-129
Author(s):  
Jun Shan Wang ◽  
Pei Yang Shi ◽  
Cheng Jun Liu ◽  
Mao Fa Jiang
Keyword(s):  
Yield Strength ◽  
Grain Boundary ◽  
Cooling Rate ◽  
Crystal Size ◽  
High Strength ◽  
Weathering Steel ◽  
Second Phase ◽  
Second Phase Particles

According to the characteristics of high strength weathering steel, this paper designs to develop anexperimental steel S450EW with yield strength higher than 450MPa.Through the study,it has been found that with decreasing cooling rate, the organizational changed largely, while ferrite and pearlite gradually transformed to martensite and a small amount of ferrite, then finally tomartensite organization.It has also been found that the crystal size decreased, and the experimentalsteel also precipitated a rectangular second phase particles of (NbTi) CN phase and TiC, which were sparsely distributed with the size of 100 ~ 300nm and below 30nm, while some phases were distributedasa number of strips in the grain boundary which mainly are C, Fe, Cr.

Effect of Niobium on Microstructure of X80 Grade Pipe Line Steels

2013 ◽  
Vol 368-370 ◽  
pp. 720-725
Author(s):  
Dong Jie Bao ◽  
Ji Ming Zhang ◽  
Qing Lin
Keyword(s):  
Retained Austenite ◽  
Lath Martensite ◽  
High Strength ◽  
Second Phase ◽  
Extraction Replica ◽  
Large Size ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Nb Content ◽  
Pipe Line

Microstructure of high strength pipeline steels containing different Nb contents was investigated using optical microscopy and transmission electron microscopy. Second phase particles were analyzed by extraction replica method. The results show that microstructure of the low Nb steel comprises granule bainite and the low bainite with a few of martensite-austenite (M-A) constituents. However, microstructure is consisted of acicular ferrite with M-A constituents in high Nb content steel. Moreover, M-A constituent is consisted of twinning martensite, lath martensite and retained austenite. In the low Nb steel precipitates are a large of square TiN particles. Second particles of high Nb content are mainly the large size duplex type (Nb,Ti)C and small NbC precipitates.

scholarly journals Effect of Rare Earth Ce on Deep Stamping Properties of High-Strength Interstitial-Free Steel Containing Phosphorus

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1473
Author(s):  
Hao Wang ◽  
Yanping Bao ◽  
Chengyi Duan ◽  
Lu Lu ◽  
Yan Liu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Rare Earth ◽  
High Strength ◽  
Rolling Process ◽  
P Element ◽  
Second Phase ◽  
Strengthening Effect ◽  
Interstitial Free ◽  
If Steel

The influence of rare earth Ce on the deep stamping property of high-strength interstitial-free (IF) steel containing phosphorus was analyzed. After adding 120 kg ferrocerium alloy (Ce content is 10%) in the steel, the inclusion statistics and the two-dimensional morphology of the samples in the direction of 1/4 thickness of slab and each rolling process were observed and compared by scanning electron microscope (SEM). After the samples in each rolling process were treated by acid leaching, the three-dimensional morphology and components of the second phase precipitates were observed by SEM and energy dispersive spectrometer (EDS). The microstructure of the sample was observed by optical microscope, and the grain size was compared. Meanwhile, the content and strength of the favorable texture were analyzed by X-ray diffraction (XRD). Finally, the mechanical properties of the product were analyzed. The results showed that: (1) The combination of rare earth Ce with activity O and S in steel had lower Gibbs free energy, and it was easy to generate CeAlO3, Ce2O2S, and Ce2O3. The inclusions size was obviously reduced, but the number of inclusions was increased after adding rare earth. The morphology of inclusions changed from chain and strip to spherical. The size of rare earth inclusions was mostly about 2–5 μm, distributed and dispersed, and their elastic modulus was close to that of steel matrix, which was conducive to improving the structure continuity of steel. (2) The rare earth compound had a high melting point. As a heterogeneous nucleation point, the nucleation rate was increased and the solidification structure was refined. The grade of grain size of products was increased by 1.5 grades, which is helpful to improve the strength and plasticity of metal. (3) Rare earth Ce can inhibit the segregation of P element at the grain boundary and the precipitation of Fe(Nb+Ti)P phase. It can effectively increase the solid solution amount of P element in steel, improve the solid solution strengthening effect of P element in high-strength IF steel, and obtain a large proportion of {111} favorable texture, which is conducive to improving the stamping formability index r90 value.

Dependence of fracture toughness on multiscale second phase particles in high strength Al alloys

2003 ◽  
Vol 19 (7) ◽  
pp. 887-896 ◽  
Author(s):  
G. Liu ◽  
G.-J. Zhang ◽  
X.-D. Ding ◽  
J. Sun ◽  
K.-H. Chen
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Al Alloys ◽  
Second Phase ◽  
Second Phase Particles
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