Application of a chamfer slab technology to reduce internal cracks of continuous casting bloom during soft reduction process

Abstract

The stress concentrations over the brittle temperature range (BTR) in the bloom continuous casting are the main reason of internal cracks. In order to analyze the stress distribution in the BTR of the blooms during soft reduction stage, a three-dimensional thermo-mechanical finite-element model with different corner structures (i.e. chamfer angle and chamfer length) was established. The relationship between corner structures, maximum tensile stress, as well as shear stress is analyzed, and the influence of corner structure of bloom on the internal cracks is studied. The results show that the tensile stress and the shear stress decreased gradually by properly adjusting the chamfer angle and the chamfer length of the bloom. Compared with the use of the right-angle bloom casting, the application of chamfer bloom casting is able to reduce the stress concentration over the BTR, therefore reduces the internal cracks. In addition, as a side benefit, the chamfer bloom casting can save energy required in deforming the bloom during the soft reduction process.

Influence of differential reduction rate in adjacent roll reduction zone on internal cracks of high carbon bloom induced by mechanical soft reduction

“…Friction factor between reduction rolls and as-cast bloom was set as 0.3, automatic time step of the minimum and maximum time step was set as 0.01 s and 1 s respectively. The temperature distribution of as-cast bloom has been calculated firstly, which can be found in the present authors' previous work and introduced in detail elsewhere, [5][6][7]11,15,16 then the temperature field was transferred to the 3D thermal-mechanical model as the initial temperature field.…”

“…However, internal cracks are always observed between the surface and the centerline of as-cast bloom in many industrial trials induced by soft reduction technologies. [3][4][5][6][7][8][9][10][11] The reduction amount, rate and zone are the key parameters to determine the application results of MSR. The total reduction amount can be calculated by multiplying the reduction rate with reduction zone, this research work is focused on the determination of the reduction rate, as it allows the evaluation of the actual reduction amount in a specific reduction zone.…”

“…However, the deformation is transmitted from the as-cast bloom surface to center zone of incomplete solidification area, internal cracks are easily formed, especially for the large-section size bloom. With regarding to study on alleviation of internal cracks induced by MSR, the former researchers [6][7][8][9][10][11][12] numerically and experimentally studied the improvement of center segregation and central porosity closure behavior induced by MSR, and seldom 1 Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing, China 2 Xingtai Iron and Steel Corp., Ltd., Hebei, China learned it from the internal crack perspective. Won et al 14 proposed a mathematical model for evaluating the relationship between internal cracks, strength and ductility of steel materials in the high temperature region.…”

Controlling centre segregation and shrinkage cavities without internal crack in as-cast bloom of steel GCr15 induced by soft reduction technologies

“…In order to improve the calculation efficiency of the coupled model, only heat transfer was calculated before the bloom arrived at the withdraw and straightener unit 1#. The temperature distribution of as-cast bloom when it is in the soft reduction region has been transferred to the reduction model as the initial temperature fields, which was introduced in detail elsewhere [4][5][6]13]. Figure 1 shows the three-dimensional mechanical model, reduction rollers and bloom are assumed to be discrete rigid and deformable body, respectively.…”

“…Mechanical soft reduction (MSR) technology is an effective method to alleviate centre segregation and shrinkage cavities in the continuous casting process [3][4][5][6]. In addition, a considerable scientific research has undertaken to investigate those MSR technologies in many industrial trials, and the results have been proved to be efficient to reduce the bloom centre segregation as well as shrinkage cavities in the continuous casting process [7][8][9]; however, internal cracks occur easily for these above-mentioned reduction technologies, which have the most adverse effect on mechanical properties of final products [10].…”