Effects of Cooling Rate on Microstructure and Properties of Nb-Ti Micro-Alloyed Steel

2013 ◽  
Vol 341-342 ◽  
pp. 208-212
Author(s):  
Xin Li ◽  
Jie Zhao ◽  
Xun Yang ◽  
Jun Cheng Bao ◽  
Bao Qun Ning
Keyword(s):  
Mechanical Property ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Hot Rolling ◽  
High Strength Steel ◽  
High Strength ◽  
Alloyed Steel ◽  
Continuous Cooling Transformation ◽  
Micro Alloyed Steel ◽  
P Colonies

Continuous cooling transformation (CCT) curves of deformed austenite (A) of Nb-Ti microalloying high strength steel were measured using Gleeble-3800 thermo-mechanical simulator, and corresponding transformation and structure were analyzed, and the effects of cooling rate on the tested steels mechanical property were studied. The resultes showed that the Ar3transformation point decreased with increasing cooling rate after hot-rolling. The morphology of ferrite (F) grains changed from polygonal to lath, and the pearlite (P) colonies became more fine with increasing cooling rate. The quantity of ferrite and pearlite decreased, and the quantity of bainite (B) and martensite (M) increased. Then the hardness of Nb-Ti micro-alloyed steel is increased along with the increasing cooling rate, which may owing to the reasons that the hardness of ferrite and pearlite is far smaller than that of bainite and martensite, and the grain refinement causes the hardness increasing.

The Microstructure and Formability Study on DP Steel of Lightweight Automobile

2011 ◽  
Vol 704-705 ◽  
pp. 1465-1472
Author(s):  
Jin Wu ◽  
Da Sen Bi ◽  
Liang Chu ◽  
Jian Zhang ◽  
Yun Tao Li
Keyword(s):  
Mechanical Property ◽  
Work Hardening ◽  
High Strength Steel ◽  
High Strength ◽  
Mathematic Model ◽  
Theoretical Research ◽  
Forming Limit ◽  
Strain Hardening Exponent ◽  
Dp Steel ◽  
Better Than

Dual phase (DP) steel is a high strength steel for auto-panel. In this paper, mechanical property, forming ability, baked-hardening and work hardening properties of high strength steel DP450 are studied by experiments, and compared with those of steel MS6000.And theoretical research on predicting the forming limit of steel DP450 by the NADDRG model. The established mathematic model for relativity is of practical usefulness. Experimental results reveal that the yield strength of steel DP450 is about 7.2% lower than the MS6000,and the break strength increases by 18.9%,while the elongation increases by 19%.The strain hardening exponent of steel DP450 are superior to those of MS6000.The results show that mechanical property of high strength steel DP450 is better than that of MS6000,while forming ability of DP450 is not lower than that of MS6000.And baked-hardening and work hardening properties of steel DP450 are better than those of MS6000.The steel sheet DP450 owned a good forming ability.

Precipitation and Mechanical Property of V‐Alloyed Steel: Role of Cooling Rate

2019 ◽  
Vol 91 (2) ◽  
pp. 1900444
Author(s):  
Zhang Huang ◽  
Hao Yu ◽  
Chenghao Song ◽  
Shuying Li ◽  
Xiaoni Duan ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Cooling Rate ◽  
Alloyed Steel

3D FEM Simulation of the Effect of Cooling Rate on SDAS and Macrosegregation of a High Strength Steel

2018 ◽  
Vol 941 ◽  
pp. 2360-2364 ◽  
Author(s):  
Gary Brionne ◽  
Abdelhalim Loucif ◽  
Chun Ping Zhang ◽  
Louis Philippe Lapierre-Boire ◽  
Mohammad Jahazi
Keyword(s):  
Boundary Conditions ◽  
Mushy Zone ◽  
Cooling Rate ◽  
High Strength Steel ◽  
Fem Simulation ◽  
High Strength ◽  
3D Fem ◽  
Cooling Rates ◽  
Positive Segregation ◽  
The Difference

Secondary dendrite arm spacing (SDAS) is a macrosegregation parameter directly linked to content of macrosegregation through cooling rates. The aim of this paper is to highlight the effect of cooling rate on the SDAS and macrosegregation patterns in a high strength steel. For this purpose, directionnal solidification in a cylinder was modeled with a plane-front solidification. Two cylinders were modeled with different boundary conditions (Tsurface = 1000°C and 1200°C). Using the FEM software Thercast, 3D macrosegregation maps were generated with thermomechanic algorithm taking into account metal shrinkage. Using Won’s equation, the influence of cooling rates in the mushy zone on SDAS was determined. The results indicated that a 72% lower difference in the area of negative macrosegregation zone (macrosegregation ratio (rseg) < -0.016%) for lower cooling rate (Ts = 1200°C). The difference of the area for positive segregation was 85% lower for higher cooling rates.

Investigation of the High Strength Steel Al-Si Coating during Hot Stamping Operations

2009 ◽  
Vol 410-411 ◽  
pp. 289-296 ◽  
Author(s):  
Francesca Borsetto ◽  
Andrea Ghiotti ◽  
Stefania Bruschi
Keyword(s):  
Surface Roughness ◽  
Cooling Rate ◽  
High Strength Steel ◽  
Room Temperature ◽  
Heating Temperature ◽  
Hot Stamping ◽  
High Strength ◽  
Tribological Behaviour ◽  
Metal Sheets ◽  
Coating Characteristics

To improve the low formability that HSS sheets exhibit at room temperature, innovative forming technologies like the hot stamping process are currently applied. In order to avoid scaling and decarburization during the heating step, metal sheets coated with a specially developed Al-Si coating are utilized. In the present work the coating characteristics in terms of morphology, surface roughness and tribological behaviour are investigated as function of heating temperature, holding time and cooling rate that are typical of hot stamping processes.

The Role of Niobium in Lightweight Vehicle Construction

2007 ◽  
Vol 537-538 ◽  
pp. 679-686 ◽  
Author(s):  
Hardy Mohrbacher ◽  
Christian Klinkenberg
Keyword(s):  
Grain Refinement ◽  
High Strength Steel ◽  
Mechanical Performance ◽  
High Strength Steels ◽  
High Strength ◽  
Interstitial Free ◽  
Niobium Microalloying ◽  
Hsla Steels ◽  
Steel Grades ◽  
Different Characteristics

Modern vehicle bodies make intensive use of high strength steel grades to improve the weight and the mechanical performance simultaneously. A broad range of medium and extra high strength steel grades is available. These steel grades have different characteristics concerning strength, formability and weldability. For many steel grades microalloying by niobium is the key to achieve their characteristic property profile. In HSLA steels niobium enhances the strength primarily by grain refinement. In interstitial free high strength steels niobium serves as a stabilizing element and also assists in obtaining the bake hardening effect. Some modern multiphase steels rely on niobium to achieve additional strength via grain refinement and precipitation hardening. Microstructural control provides a way to further optimize properties relevant to automotive processing such as cutting, forming and welding. The relevance of niobium microalloying in that respect will be outlined.

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