Solidification Structure, Non-metallic Inclusions and Hot Ductility of Continuously Cast High Manganese TWIP Steel Slab

Mountain‐like surface cracks often appear on the thick plates of high‐strength low‐alloy (HSLA) steel after hot rolling, which have a serious impact on production efficiency. Herein, the formation cause of mountain‐like cracks is discussed using methods such as acid pickling and observations of microstructure and inclusions. The deformation behavior of microcracks is obtained by analyzing the rolling process of slab. The inclusions in the top of the crack are Type‐I inclusions with high elemental contents of K and P and Type‐II inclusions with high elemental contents of C. The inclusions in the sides of the crack are Al2O3. It is concluded that mountain‐like cracks are caused by surface microcracks containing Type‐I inclusions in the continuous casting slab. During rolling, the rapid deforming of side‐1 stretches the crack so that the unusual microstructure appears. The cracks extended in the rolling direction have Al2O3 inclusions. The mountain‐like crack with Type‐I inclusions in the top and Al2O3 in the sides eventually form. A single microcrack forms a single mountain‐like crack and multiple clustered microcracks form a continuous mountain‐like crack. To reduce mountain‐like cracks, reducing Type‐I inclusions to reduce surface defects of the slab is an effective means.

Section: Discussionmentioning

confidence: 99%

Formation and Deformation Mechanism of Mountain‐Like Surface Crack on the Hot‐Rolled Thick Plate of HSLA Steel

Shen

Cheng

Wang

2022

“…With the continuous improvement in productivity, more and more attention has been given to the prevention of transverse corner cracks. [6,[8][9][10] There are three brittle temperature zones from the solidification temperature of steel to 600 C. The third brittle temperature zone plays a vital role in controlling the occurrence of angular transverse cracks during continuous casting. In previous studies, it was found that strain rate and deformation temperature have a significant effect on the thermoplasticity of materials.…”

Section: Introductionmentioning

confidence: 99%

Hot Ductility and Fracture Behavior of High‐Ti Weathering Steel

Song

Gao

Xue³

et al. 2021

The hot ductility behavior of high‐Ti weathering steel is studied by high‐temperature tensile testing in the temperature range of 650–1100 ºC. The results reveal a ductility trough in high‐Ti steel in the range of 650–962, 650–925, and 700–880 °C with minimum reduction in area (RA) of 22.21%, 36.53%, and 43.25% at 800 ºC and different strain rates of 1.0 × 10−3, 5.0 × 10−3, and 1.0 × 10−2 s−1, respectively. A number of secondary cracks containing S, N, and Ti propagate along the grain boundary, and the obvious preferred orientation is found in the microstructure near the fracture at 800 °C. With the increase in strain rate, the value of RA is increased in the temperature range of 650–1050 ºC, such that the probability of crack occurrence is decreased. RA does not increase with the increase in strain rate at 1100 °C and strain rate of 1.0 × 10−2 s−1. The underlying reason is that there is not adequate time for the material to recover or recrystallize with the increase in strain rate, resulting in material softening effect that is not completely reflected.

“…[1][2][3][4] In particular, as fully austenitic high-Mn steels with 12-30 wt% Mn, transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels have attracted intense attention due to their remarkable mechanical properties, including high strength, excellent ductility, and high energy absorption capacity, and are promising candidate for the fourth-generation automotive steels. [5][6][7] Therefore, most studies of high-Mn steels have focused on their mechanical properties such as solidification structures, [8,9] nonmetallic inclusions, [10][11][12] tensile ductility [13,14] and deformation behavior, [15,16] etc., whereas studies of the smelting process have been rarely reported.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Oxidation Behavior of Mn Fumes Generated in the Vacuum Treatment of Melting Mn Steels

Chu

Bao

et al. 2020

Herein, the phase, composition, morphologies, particle size distribution, and specific surface area of Mn oxide fumes generated after the vacuum treatment of melting Mn steels with different initial Mn contents are characterized. The thermodynamic calculation results reveal that for a given temperature and pressure, Mn vapor generation increases with increasing initial Mn content in steel. Moreover, the experimental results find that the amount of the Mn oxide fumes on the vacuum chamber after vacuum processing gradually increases with increasing initial Mn content in the melt. The fumes on the crucible generated after vacuum processing are composed of mainly coral‐shaped Mn3O4 with the size of 500 nm and a small amount of spherical‐like Mn2O3 with the sizes of 50–200 nm. Meanwhile, the fumes deposited on the furnace chamber contain Mn nanoparticles with the sizes of less than 50 nm, MnO nanorods with the sizes of 50–200 nm, and Mn3O4 nanoparticles with the sizes of 50–500 nm. In addition, the main phase of the fumes deposited on the vacuum chamber gradually changes to elemental Mn with an increase in the initial Mn content. The temperature and particle size are responsible for thermodynamic stability of Mn oxides at the nanoscale.