scholarly journals Effect of Magnesium Treatment on the Hot Ductility of Ti-Bearing Peritectic Steel

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1282
Author(s):  
Tianpeng Qu ◽  
Deyong Wang ◽  
Huihua Wang ◽  
Dong Hou ◽  
Jun Tian
Keyword(s):  
Continuous Casting ◽  
Local Stress ◽  
Solidification Structure ◽  
Hot Ductility ◽  
Peritectic Transformation ◽  
Peritectic Steel ◽  
Surface Cracking ◽  
Average Grain Size ◽  
Corner Cracks ◽  
Magnesium Treatment

Surface cracking is a major defect in the production of continuous casting slabs of peritectic steel. The difference in crystal structure between δ phase (before peritectic transformation of steel) and γ phase (after peritectic transformation) results in volume contraction, which leads to uneven cooling of mold and thus forming slab shells with different thicknesses. Then, coupled with the concentration of local stress, surface cracking occurs on slabs. In this paper, the effect of magnesium treatment on the hot ductility of Ti-bearing peritectic steel was studied, and the characteristics of solidification structure and TiN particles were analyzed. Magnesium treatment for Ti-bearing peritectic steel could significantly improve the hot ductility of continuous casting slabs by refining the original austenite structure. After the magnesium treatment, the average grain size of the original austenite of peritectic steel decreased by about 18.7%, and the size of Mg-rich TiN particles decreased by about 41%. In addition, the minimum reduction of area at the third brittle zone after the magnesium treatment was higher than 60%, and the fracture appearance changed from intergranular fracture to ductile fracture after the treatment. The contents of Mg, Ti, O, and N in peritectic steel and the cooling conditions were adjusted reasonably to promote the formation of highly dispersed Mg-rich TiN particles with a sufficient number density and a proper size in the initial solidification stage of peritectic steel, so as to induce the high-temperature δ-ferrite nucleation. Based on the fine δ structure formed by peritectic transformation, through the use of structure heredity and the pinning effect of secondary-precipitated nano TiN particles on the austenite grain boundary, a fine and dense original austenite structure could be obtained to improve the hot ductility of peritectic steel. Industrial tests showed that through the magnesium treatment, the surface cracks of Ti-bearing peritectic steel were effectively restrained, and the corner cracks of slabs were basically eliminated.

Deformation and Structure Difference of Steel Droplets during Initial Solidification

2017 ◽  
Vol 36 (4) ◽  
pp. 347-357 ◽  
Author(s):  
Yang Li ◽  
Jing Wang ◽  
Jiaquan Zhang ◽  
Changgui Cheng ◽  
Zhi Zeng
Keyword(s):  
Carbon Steel ◽  
Continuous Casting ◽  
High Carbon Steel ◽  
Low Carbon Steel ◽  
Carbon Steels ◽  
Solidification Structure ◽  
Low Carbon ◽  
High Carbon ◽  
Peritectic Steel ◽  
Initial Solidification

AbstractThe surface quality of slabs is closely related with the initial solidification at very first seconds of molten steel near meniscus in mold during continuous casting. The solidification, structure, and free deformation for given steels have been investigated in droplet experiments by aid of Laser Scanning Confocal Microscope. It is observed that the appearances of solidified shells for high carbon steels and some hyper-peritectic steels with high carbon content show lamellar, while that for other steels show spherical. Convex is formed along the chilling direction for most steels, besides some occasions that concave is formed for high carbon steel at times. The deformation degree decreases gradually in order of hypo-peritectic steel, ultra-low carbon steel, hyper-peritectic steel, low carbon steel, and high carbon steel, which is consistent with the solidification shrinkage in macroscope during continuous casting. Additionally, the microstructure of solidified shell of hypo-peritectic steel is bainite, while that of hyper-peritectic steel is martensite.

Formation and Control of Transverse Corner Cracks in the Continuous Casting Slab of a Microalloyed Steel

2021 ◽  
pp. 2000649
Author(s):  
Yadong Wang ◽  
Qiang Ren ◽  
Lifeng Zhang ◽  
Xiaogang Yang ◽  
Wen Yang ◽  
...  
Keyword(s):  
Continuous Casting ◽  
Microalloyed Steel ◽  
Continuous Casting Slab ◽  
Corner Cracks ◽  
And Control

Impact of Surface Structure Control Cooling During Continuous Casting on Hot Ductility of Microalloyed Steel

2015 ◽  
Vol 87 (7) ◽  
pp. 871-879 ◽  
Author(s):  
Martin Lückl ◽  
Ozan Caliskanoglu ◽  
Sergiu Ilie ◽  
Jakob Six ◽  
Ernst Kozeschnik
Keyword(s):  
Continuous Casting ◽  
Surface Structure ◽  
Microalloyed Steel ◽  
Hot Ductility ◽  
Structure Control

Characteristics of Hot Ductility and Fracture in Micro-Alloyed Q345B Structural Steel

2011 ◽  
Vol 194-196 ◽  
pp. 150-156 ◽  
Author(s):  
Fang Dong ◽  
Cheng Su ◽  
Yuan Yuan Bai
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Continuous Casting ◽  
Structural Steel ◽  
Void Nucleation ◽  
Hot Ductility ◽  
Strain Rates ◽  
Casting Condition ◽  
Temperature Range ◽  
Scanning Electron

Hot-ductility tests of the microalloyed Q345B structural steel were performed in a tensile machine of Gleeble-1500D at different strain rates of 1.5•10-3/s 、2.5•10-3/s and 2•10-2/s and at temperature range from 1300°C to 700°C(Δ T=100°C ), which are close to the continuous casting condition of steel. Fracture surfaces were examined using a scanning electron microscope; it was found that the hot decrease as strain rate decrease, because the void growth mechanism predominates over void nucleation, giving time for nucleation cracks to grow. The minimum ductility was found at about 800°C for the strain rates of 1.5•10-3/s and 2.5•10-3/s, and the fracture was intergranular. The steel has good plasticity in temperature range from 1200°C to 900°C which is suitable for straighten operation.

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