Microstructure Evolution and Mechanical Properties of 780 MPa Hot Dip Galvanized Dual-Phase Steel

2010 ◽  
Vol 146-147 ◽  
pp. 1331-1335 ◽  
Author(s):  
Guo Bin Li ◽  
Zheng Zhi Zhao ◽  
Di Tang

The microstructure evolution of 780 MPa hot dip galvanized dual-phase (DP) steel at heating stages of the annealing process was analyzed using a Gleeble−3500 thermal/mechanical simulator. A multifunction continuous annealing simulator was employed to investigate the effect of annealing process on microstructure and mechanical properties of hot dip galvanized DP steel. The experimental results show that ferrite recovery and recrystallization, pearlite dissolution and austenite nucleation and growth take place in the annealing process of hot dip galvanized DP steel. The hardenability can be significantly improved by trace addition of vanadium. When the soaking temperature reaches 780 °C, the tensile strength and total elongation of DP steel can reach 785MPa and 15%, respectively. The microstructure of DP steel mainly consists of a mixture of ferrite and martensite.

2014 ◽  
Vol 59 (2) ◽  
pp. 821-824 ◽  
Author(s):  
M. Šebek ◽  
P. Horňak ◽  
P. Zimovčák ◽  
S. Longauer

Abstract The article deals with the influence of annealing parameters on evolution of microstructure and mechanical properties of dual phase steel. Dual phase steel was annealed in laboratory conditions according to the three chosen cycles of annealing: into intercritical region (780°C), into austenite region (920°C) and into austenite region (920°C) by subsequently cooling into intercritical region (780°C) with the hold at the temperature of 495°C. Simulation of annealing regimes by thermo-mechanical simulator Gleeble was done. The obtained microstructure consists from three phases: ferritic matrix, martensite and martensite/ bainite grains. For the microstructure identification the TEM and nanoindentation experiments were performed.


2016 ◽  
Vol 867 ◽  
pp. 45-49
Author(s):  
Ji Lin Chen ◽  
Guo Hui Zhu ◽  
Jian Zhang ◽  
Yong Gang Liu ◽  
Hong Bo Pan

A new continuous annealing process which can eliminate the "band" feature of dual phase steels has been designed. The sheets were annealed in MULTIPAS annealing simulator under variation of annealing temperature. The microstructure evolution of dual-phase steel sheets annealed at intercritical temperatures, were analyzed by optical microscopy and scanning electron microscopy. And the properties were compared with the sheets which annealed by the existing annealing process. The results show that: the "band" feature of dual-phase steel can be effectively eliminated by the optimizing continuous annealing process,and the mechanical properties are improved.


2012 ◽  
Vol 476-478 ◽  
pp. 241-247 ◽  
Author(s):  
Li Gao ◽  
Qiu Hong Song ◽  
Jun Ting Yuan

The effect of continuous annealing parameters on the microstructure and magnetic property of cold rolled dual phase steel (DP steel) are investigated. Correlations of microstructure, magnetic properties and continuous annealing parameters are revealed. The mechanism of the magnetic property varying with continuous annealing process is also discussed. The results show that recrystallization is almost completed when heating to 740°C. For the DP steel soaked in the range of 770°C-830°C and quenched in different temperature, the TEM results indicate its microstructure mainly consists of the ferrite and martensite phase. The martensite volume fraction increases gradually with increasing the soaking and quenching temperature. It is found that magnetic properties of dual phase steel are very sensitive to continuous annealing process. With rising soaking and quenching temperature, the coercivity and hysteresis loss increase obviously, whereas the maximum permeability and the remanent induction tend to decrease.


2010 ◽  
Vol 638-642 ◽  
pp. 3479-3484 ◽  
Author(s):  
Roberta O. Rocha ◽  
Tulio M.F. Melo ◽  
Dagoberto Brandao Santos

The influence of continuous annealing variables on the microstructure and mechanical properties of a C-Mn Dual Phase (DP) steel was studied. The annealing cycles were simulated using a Gleeble machine. Some specimens were quenched at different stages of the annealing cycle in order to evaluate the microstructural evolution during the annealing process. Tensile tests and microstrutural analysis were carried out. The results showed that high heating rates increased the final recrystallization temperature and as a consequence the microstructure obtained was refined. Austenite grain nucleation and growth were also influenced by the heating rates. Soaking temperature was the most influent variable on the mechanical properties, i. e., the yield strength increased and the tensile strength decreased with an increase in the soaking temperature. Microstructural analysis showed that not only martensite, but also bainite and martensite-retained autenite constituent (MA) were formed. Undissolved carbides were also detected by transmission electron microscopy.


2014 ◽  
Vol 59 (4) ◽  
pp. 1257-1261
Author(s):  
K. Miernik ◽  
S. Pytel

Abstract The paper presents results of microstructure and mechanical properties of the dual phase (DP) steel plate with 12 mm thickness produced by intercritical annealing at a two-phase region of ferrite and austenite (α + γ) and direct quenching in water. In addition the tempering treatment at temperature of 650°C was applied to investigate effect of martensite softening on mechanical properties of the tested steel. The parameters of heat treatment were designed to achieve the high strength while retaining optimum impact strength of the DP steel.


2015 ◽  
Vol 808 ◽  
pp. 28-33 ◽  
Author(s):  
Constantin Dulucheanu ◽  
Nicolai Bancescu ◽  
Traian Severin

In this article, the authors have analysed the influence of quenching temperature (TQ) on the mechanical properties of a dual-phase steel with 0.094 % C and 0.53% Mn. In order to obtain a ferrite-martensite structure, specimens of this material have been the subjected to intercritical quenching that consisted of heating at 750, 770, 790, 810 and 830 °C, maintaining for 30 minutes and cooling in water. These specimens have then been subjected to metallographic analysis and tensile test in order to determine the volume fraction of martensite (VM) in the structure, ultimate tensile strength (Rm), the 0.2% offset yield strength (Rp0.2), the total elongation (A5) and the Rp0.2/Rm ratio.


2009 ◽  
Vol 19 ◽  
pp. s563-s568 ◽  
Author(s):  
Zheng-zhi ZHAO ◽  
Guang-can JIN ◽  
Feng NIU ◽  
Di TANG ◽  
Ai-min ZHAO

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