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

scholarly journals Effect of High Temperature Deformation on the Hot Ductility of Nb Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 115-122 ◽  
Author(s):  
Faramarz Zarandi ◽  
Steve Yue
Keyword(s):  
Continuous Casting ◽  
High Temperatures ◽  
Microalloyed Steel ◽  
Casting Process ◽  
Temperature Deformation ◽  
Hot Ductility ◽  
Continuous Casting Process ◽  
Billet Surface ◽  
Nb Microalloyed Steel ◽  
Very High

Low hot ductility of steel at the straightening stage of the continuous casting process is a problem found in steels containing microalloying and/or certain alloying additions. The thermal schedule undergone by the billet surface in the mill has a significant effect on the hot ductility. In this work, thermomechanical processing was employed to alleviate the problem of hot ductility in the Nb-microalloyed steel. Specimens were melted in situ and subjected to the billet surface thermal schedule in order to generate a microstructure similar to that present at the straightening stage of the continuous casting process. Some deformation schedules were incorporated with the thermal schedule at very high temperatures, specifically during solidification, within the d-ferrite region, and during the d®g transformation, and the hot ductility was subsequently evaluated at the end of the thermal schedule where the straightening operation is performed. After the thermal schedule alone, the steel exhibited a very low hot ductility at the straightening stage. It was found that deformation at very high temperatures prior to the straightening stage had a considerable effect on the hot ductility, either detrimental or beneficial, depending on the region in which the deformation has been executed. The mechanisms leading to loss and improvement of hot ductility are explained in this paper.

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

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.

scholarly journals Effects of Sn and Sb on the Hot Ductility of Nb+Ti Microalloyed Steels

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1679
Author(s):  
Chunyu He ◽  
Jianguang Wang ◽  
Yulai Chen ◽  
Wei Yu ◽  
Di Tang
Keyword(s):  
Laser Scanning ◽  
Microalloyed Steel ◽  
Confocal Laser Scanning Microscope ◽  
Microalloyed Steels ◽  
Confocal Laser ◽  
Hot Ductility ◽  
High Temperature Mechanical Properties ◽  
Ductility Trough ◽  
Gleeble 3500 ◽  
Fracture Morphologies

Referencing the composition of a typical Nb+Ti microalloyed steel (Q345B), two kinds of steels, one microalloyed with Sn and Sb, and the other one only microalloyed with Sb were designed to study the effects of Sn and Sb on the hot ductility of Nb+Ti microalloyed steels. The Gleeble-3500 tester was adopted to determine the high-temperature mechanical properties of the two test steels. Fracture morphologies, microstructures and interior precipitation status were analyzed by SEM, CLSM (Confocal laser scanning microscope) and EDS, respectively. Results revealed that within the range of 950–650 °C, there existed the ductility trough for the two steels, which were mainly attributed to the precipitation of TiN and Nb (C, N). Additionally, precipitation of Sn and Sb were not observed in this research and the hot ductility was not affected by the addition of Sn and Sb, as compared with the Nb+Ti microalloyed steel. Therefore, addition of a small amount of Sn and Sb (≤0.05 wt.%) to the Nb+Ti microalloyed steel is favorable due to the improvement on corrosion resistance.

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.

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