Analysis and Prevention of Dent Defects Formed during Strip Casting of Twin-Induced Plasticity Steels

Abstract

Rapid-solidification experiments were conducted for understanding dent defects formed during strip casting of twin-induced plasticity (TWIP) steels. The rapid-solidification experiments reproduced the dent defects formed on these steels, which were generally located at valleys of the shot-blasted roughness on the substrate. The rapid-solidification experiment results reveal that the number of dips, the Mn content of the steel, and the surface roughness of the substrate affect the depth and size of dents formed on the solidified-shell surfaces, while the composition of the atmosphere gases and the carbon content of the steel are not factors. The formation of dents was attributed to the entrapment of gases inside the roughness valleys of the substrate surface and their volume expansion due to the temperature of the steel melt and the latent heat. The dents could be prevented when the thermal expansion of gases was suppressed by making longitudinal grooves on the substrate surface, which allowed the entrapped gases to escape. Sound solidified shells were obtained by optimizing the width and depth of the longitudinal grooves and by controlling the shot-blasting conditions.

Effect of solidification conditions and surface pores on the microstructure and columnar-to-equiaxed transition in solidification under microgravity

“…Porosities are considered as serious and common defects formed during solidification [25], which result in a significant degradation of the mechanical properties and act as the origin of crack initiation because of stress concentration [26][27][28]. Up to now, the formation of porosity has been considered by numerous investigations, but, as a matter of fact, mostly focusing solely on the pore formation mechanism [29][30][31][32][33][34][35]. It is generally accepted that the residual gases, which are mainly hydrogen, dissolve and accumulate at the solidification front, since gas solubility is often much less in the solid than in the liquid.…”

Microstructure and Mechanical Property of Strip in Fe–23Mn–3Si–3Al TWIP Steel by Twin Roll Casting

“…Good mechanical properties can be obtained through a series of subsequent processing after twin-roll strip casting, with the tensile strength and total elongation being 655 MPa and 57.4 %, respectively. The product of tensile stress and elongation is 3.76ϫ10 4 MPa%, and the uniform elongation of the processed cast strip is about 80 % that of the conventional counterpart. Figure 9 shows the comparison of the relationships of strain hardening rate, ds/de, with true strain between the two strips.…”

“…3) Therefore, the problems occurred in conventional hot strip rolling of TWIP steels are expected to be solved by "near-net-shape" forming in twin-roll strip casting. 4) Cast strip of TWIP steel with a thickness of up to 6 mm had been successfully produced in semi-industrial scale, which showed that good edge and surface qualities could be obtained. 5) However, the detailed mechanical properties and microstructure evolution of strip cast TWIP steel have not yet been reported so far.…”

Investigating the causes and remedies for porosity defects in the casting process: A review

“…• Surface irregularities: Surface irregularities can occur due to various reasons, including mold erosion, gas porosity, or improper mold coating. This defect can affect the appearance and function of the finished product (10).…”