Abstract:A full-scale finite-element stress model of a slab and its mould was developed to analyse the nonuniform slab shrinkage of special steel in a vertical caster during slab continuous casting. The stress model was based on the heat transfer model which was validated by comparing the calculated temperature with the measured ones. According to the shrinkage calculation, the single linear taper is not suitable for the continuous casting of this special steel, and the narrow face taper need to be calculated and optim… Show more
“…The peritectic transformation during solidification is accompanied by a change in the crystal structure from a body-centred cubic δ -ferrite to a face-centred cubic γ -austenite. Lattice density increases from 68 to 74%, resulting in a large volume shrinkage, which is the root cause of the high crack-formation tendency of the peritectic steel [26-28]. Based on the above description, the volume shrinkage during the peritectic transformation was calculated by quantifying the change in the area ratio of primary δ -ferrite phase at different distances from the S/L interface, as expressed by Equation (3): where Vs is the volume shrinkage and ΔΩ δ is the change in the area ratio of the δ -ferrite phase.…”
Directional solidification experiments were carried out on peritectic steels to investigate the microstructure and volume shrinkage. A δ-dendritic structure developed intermittently and was enclosed by γ-austenite at growth rates of 15, 50, and 80 μm s−1. The primary dendritic spacing narrowed and the average spacing of dendrites decreased as the growth velocity increased. The functional relationship between the secondary dendrite arm spacing and cooling rates was established by statistical analysis. The influence of cooling rate on crack formation was analysed as a function of volume shrinkage. Reducing the cooling rate of the solidification delayed a massive type of peritectic transformation away from the ZST–ZDT brittle zone, thus reducing the probability of crack formation.
“…The peritectic transformation during solidification is accompanied by a change in the crystal structure from a body-centred cubic δ -ferrite to a face-centred cubic γ -austenite. Lattice density increases from 68 to 74%, resulting in a large volume shrinkage, which is the root cause of the high crack-formation tendency of the peritectic steel [26-28]. Based on the above description, the volume shrinkage during the peritectic transformation was calculated by quantifying the change in the area ratio of primary δ -ferrite phase at different distances from the S/L interface, as expressed by Equation (3): where Vs is the volume shrinkage and ΔΩ δ is the change in the area ratio of the δ -ferrite phase.…”
Directional solidification experiments were carried out on peritectic steels to investigate the microstructure and volume shrinkage. A δ-dendritic structure developed intermittently and was enclosed by γ-austenite at growth rates of 15, 50, and 80 μm s−1. The primary dendritic spacing narrowed and the average spacing of dendrites decreased as the growth velocity increased. The functional relationship between the secondary dendrite arm spacing and cooling rates was established by statistical analysis. The influence of cooling rate on crack formation was analysed as a function of volume shrinkage. Reducing the cooling rate of the solidification delayed a massive type of peritectic transformation away from the ZST–ZDT brittle zone, thus reducing the probability of crack formation.
“…(2) The measured temperature was used to obtain the heat flux between the mould and slab via an inverse algorithm [14]. The heat flux is shown in Figure 3.…”
Section: Boundary Conditionsmentioning
confidence: 99%
“…Here, λ w , D, u w , μ w , C w , and ρ w are the thermal conductivity, the hydraulic diameter, the speed viscosity, the heat capacity, and the density of water. (2) The measured temperature was used to obtain the heat flux between the mould and slab via an inverse algorithm [14]. The heat flux is shown in Figure 3. Figure 3. Distribution of heat flux.…”
Section: Full-scale Thermo-mechanical Model Inverse Algorithmmentioning
The corner crack is an important issue during special steel continuous casting. To comprehensively investigate the heat transfer, stress, and shrinkage behaviours of slab corner, a full-scale thermomechanical model of a slab and its mould was developed, the inverse algorithm was applied to the model. The model was validated by comparing the calculated data with the measured data in the plant trials. The results showed that the thermo-mechanical behaviours of the slab corner showed a similar tendency but were not the same, which reflected the necessity of building a fullscale model. There exists 'hot spots' at the slab off-corner region, and its position moved away from the corner along the casting direction, which affects the temperature and stress distributions. The maximum stress value reached approximately 16 MPa at the mould exit. The model provides an in-depth understanding of slab corner during special steel continuous casting.
“…It is well known that hypo-peritectic steels are more sensitive to deep oscillations, surface shape variations, cracks, and even breakouts than low or high-carbon counterparts during continuous casting, especially at high casting speeds [ 1 , 2 , 3 , 4 , 5 ]. The surface quality problems are strongly related to the complicated peritectic transition process, which leads to nonuniform volume contraction of hypo-peritectic steels during the initial solidifying stage in the mold [ 4 , 5 , 6 , 7 , 8 ].…”
The contraction of peritectic steels in the initial solidification has an important influence on the formation of surface defects of continuously cast slabs. In order to understand the contraction behavior of the initial solidification of steels in the mold, the solidification process and surface roughness in a commercial hypo-peritectic and several non-peritectic steels were investigated using Confocal Scanning Laser Microscope (CSLM). The massive transformation of delta-Fe (δ) to austenite (γ) was documented in the hypo-peritectic steel, which caused surface wrinkles and greatly increases the surface roughness of samples in the experiments. Surface roughness (Ra(δ→γ)) was calculated to evaluate the contraction level of the hypo-peritectic steel due to δ–γ transformation. The result shows that the surface roughness method can facilitate the estimation of the contraction level of peritectic transformation over a wide range of cooling rates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
