Effect of higher heating rate during continuous annealing on microstructure and mechanical properties of cold-rolled 590 MPa dual-phase steel

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.

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Effect of Intercritical Annealing Temperature on Development of Cold Rolled Dual Phase Steel from Q345 Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.313-314.693 ◽

2013 ◽

Vol 313-314 ◽

pp. 693-696

Author(s):

Ji Yuan Liu ◽

Fu Xian Zhu ◽

Shi Cheng Ma

Keyword(s):

Dual Phase Steel ◽

Annealing Temperature ◽

Simulation Experiment ◽

Intercritical Annealing ◽

Continuous Annealing ◽

Dual Phase ◽

Automotive Applications ◽

Treatment Procedure ◽

Annealing Temperatures ◽

Cold Rolled

Cold rolled dual phase steel was developed from Q345 steel by heat treatment procedure for automotive applications. The ultimate tensile strength was improved about 100MPa higher than the traditional cold-rolled Q345 steel in the continuous annealing simulation experiment. The microstructure presented varied characteristics in different intercritical annealing temperatures; mechanical properties were changed correspondingly as well. The chief discussions are focus on the recrystallization, hardenability of austenite and martensite transformation in the experiment.

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Influence of Continuous Annealing Conditions on the Microstructure and Mechanical Properties of a C-Mn Dual Phase Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.3479 ◽

2010 ◽

Vol 638-642 ◽

pp. 3479-3484 ◽

Cited By ~ 1

Author(s):

Roberta O. Rocha ◽

Tulio M.F. Melo ◽

Dagoberto Brandao Santos

Keyword(s):

Mechanical Properties ◽

Microstructural Analysis ◽

Tensile Tests ◽

Recrystallization Temperature ◽

Continuous Annealing ◽

Dual Phase ◽

Heating Rates ◽

Microstructure And Mechanical Properties ◽

Annealing Cycle ◽

Soaking Temperature

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.

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