Comparative Study on Austenite Decomposition and Cu Precipitation During Continuous Cooling Transformation
21
Citation
34
Reference
10
Related Paper
Citation Trend
Keywords:
Acicular ferrite
Continuous cooling transformation
Acicular
Beta ferrite
Microalloyed steel
Gleeble-3500 thermo-simulation machine was employed to determine the continuous cooling transformation(CCT) curves of 700 MPa low carbon microalloyed steel. The effects of cooling rate on phase transition behavior and microstructure were investigated. The results indicate that the CCT curves were in flat shape and the low carbon bainite structure was obtained in a large cooling rate range. The cooling rates had great effects on the form, proportion, distribution and micro-hardness of phases. The microstructure in experimental steel were changed from polygonal ferrite, acicular ferrite, granular bainite to lathe bainite with micro-hardness increasing when cooling rate became faster. When the cooling rate was between 10 ℃ ·s-1 and 30 ℃ ·s-1, the microstructure of the experimental steel was mainly compound of lathe bainite, and the M/A constituents dispersed on the grain boundaries. Futhermore, the size of lathe bainite became smaller with the cooling rate increasing. Therefore controlling the intermediate temperature transformation products using a proper cooling process could improve comprehensive mechanical property of experimental steel on the basis of analyzing of its phase transition characteristics.
Acicular ferrite
Continuous cooling transformation
Microalloyed steel
Acicular
Carbon steel
Carbon fibers
Cite
Citations (0)
Although the granular bainite and lath like bainitic ferrite are the main transformation phases after continuously cooling at low rate and fast rate of the low carbon microalloyed steel, the multi type transformation phases would appear at the different transformation temperature ranges. The acicular ferrite can be formed at higher intermediate temperature during continuously cooling. The nucleation and growth of the acicular ferrite are severely influenced by the cooling rate and undercooling temperature, and the fraction of the acicular ferrite can be controlled. The acicular ferrite and lath-like bainitic ferrite multi-phase microalloyed steel can be obtained by the control of cooling process. The acicular ferrite is benefit to improve the mechanical properties of low carbon microalloyed steel.
Acicular ferrite
Lath
Microalloyed steel
Beta ferrite
Acicular
Continuous cooling transformation
Supercooling
Cite
Citations (3)
Acicular ferrite
Continuous cooling transformation
Microalloyed steel
Isothermal process
Isothermal transformation diagram
Acicular
Carbon steel
Beta ferrite
Cite
Citations (113)
Acicular ferrite
Continuous cooling transformation
Acicular
Beta ferrite
Cite
Citations (187)
CCT curves of Nb microalloyed and Nb-Mo microalloyed X80 pipeline steels were determined.Microstructure of the steels under different processing conditions were investigated by means of optical microscope,scanning electronic microscopy and transmission electron microscopy.The results show that microstructure of the steels changes from polygonal ferrite and quasi-polygonal ferrite to acicular ferrite with increase of cooling rates and the grains are refined at the same time.Significant change of the microstructure is observed at low cooling rates,when cooling rates exceed 5℃/s,microstructure which consists of acicular ferrite and M-A islands remains unchanged,but it becomes more uniform and M-A islands are finer and more dispersed.Mo addition is able to make transformation line of acicular ferrite of CCT curves right shift and promotes formation of acicular ferrite.
Acicular ferrite
Acicular
Microalloyed steel
Continuous cooling transformation
Microstructures
Cite
Citations (0)
Study on continuous cooling transformation (CCT) behavior is an essential issue before thermo-mechanical processing for a new steel. In this study, dynamic CCT characteristics and microstructural evolution of a novel Cu-bearing pipeline steel with different Cu content (1.06%, 1.46% and 2.00%) were investigated by means of a combined method of dilatometry and metallography. The microstructure developed at a cooling rate range of 0.05 to 30°C/s consisted of pearlite, polygonal ferrite, quasi-polygonal ferrite and acicular ferrite. More Cu addition could lower the transformation temperature for austenite to ferrite and lead to an increase in the driving force for the acicular ferrite transformation, resulting in a full acicular ferrite for 2.0 Cu steel at cooling rate above 2°C/s. The precipitation behavior of Cu-rich phase during continuous cooling showed that Cu precipitation could occur in the acicular ferrite, which made a hardness peak on the hardness vs cooling rate curve of 2.0Cu steel at the cooling rate of 2°C/s. However, no Cu precipitate was detected in the acicular ferrite at higher cooling rate for 2.0 Cu steel. Higher supersaturation of Cu in austenite and a short incubation period of Cu-rich phase precipitation were assumed to allow the Cu precipitation to occur in the auto-aging after acicular ferrite transformation.
Acicular ferrite
Continuous cooling transformation
Acicular
Beta ferrite
Metallography
Cite
Citations (10)
During the development of Ti-microalloyed X70 pipeline steel,X70 dynamic CCT curve of Ti-microalloyed X70 pipeline steel at different cooling rates were measured by Gleeble-1500 thermal simulator,and corresponding transformation and microstructures were observed and analyzed.The test results showed that the volume fraction of acicular ferrite in the microstructure of Ti-microalloyed X70 pipeline steel increased obviously with the increase of cooling rate after thermo-mechanical deformation.However,the volume fraction of acicular ferrite varies scarcely when the cooling rate reaches 10 ℃/s.In order to obtain Ti-microalloyed X70 pipeline steel with excellent combined mechanical properties,which has acicular ferrite as the main ideal microstructure,the cooling rate should be controlled to about 10 ℃/s.
Acicular ferrite
Microalloyed steel
Volume fraction
Continuous cooling transformation
Acicular
Cite
Citations (0)
The different dilatometric curves of continuous cooling transformation were measured on Gleeble-1500 thermal mechanical simulator with methods of dilatometric change and differential thermal analysis. Referencing microscopic test and hardness measurement,the critical points and phase transformation points were determined,and the continuous cooling transformation curves (CCT diagram) of a low-carbon microalloyed pipeline steel were obtained. Transformation of austenite in the course of continuous cooling was investigated. The results show that adding 0.21% Mo can inhibit the formation of ferrite and pearlite,and promote the formation of acicular ferrite. Acicular ferrite can be obtained within a wider cooling rate range of 5.0-20.0 ℃ /s,which shows that the microstructure needed for engineering application can be obtained in the low-carbon Mn-Nb-Mo microalloyed pipeline steel.
Continuous cooling transformation
Acicular ferrite
Microalloyed steel
Supercooling
Acicular
Cite
Citations (0)
Acicular ferrite
Lath
Microalloyed steel
Continuous cooling transformation
Acicular
Cite
Citations (0)
The effect of molybdenum(Mo) and chromium(Cr) on the behaviour of continuous cooling transformation(CCT) of low carbon microalloyed steels containing niobium(Nb) and titanium(Ti) was investigated by using a Gleeble 3800 thermomechanical simulator and heat expansion method.The phase transformation temperature of three low carbon microalloyed steels at various cooling rates with different content of Mo and Cr was detected,the microstructure was observed by optical microscopy and scanning electron microscopy,and vickers hardness was also tested,then the dynamic continuous cooling transformation curves were determined.As a result,the transformation temperature from deformed austenite to acicular ferrite is decreased with adding Mo and Cr in the steels,and the effect of Mo is more significant than that of Cr when the cooling rate is above 1℃/s,and the formation of proeutecid ferrite and pearlite is inhabited or postponed.Mo and Cr element also can enlarge the range of cooling rate for forming acicular ferrite,and can refine the microstructure effectively.
Acicular ferrite
Continuous cooling transformation
Microalloyed steel
Acicular
Cite
Citations (0)