Effect of Dendritic Morphology and Central Segregation of Billet Castings on the Microstructure and Mechanical Property of Hot-Rolled Wire Rods

Abstract

Microscopic dendritic morphology and central macrosegregation in continuously cast high carbon steel billets with a cross section 150 Â 150 mm 2 are investigated to elucidate their effect on the microstructure and mechanical property of the following hot-rolled wire rods, whose diameters are 10 and 6.5 mm, respectively. Experimental observations and numerical simulations for the steel billets under different casting conditions are carried out. It is found that the secondary dendrite arm spacing (SDAS) in the billets increases with the increase of superheat temperature, while decreases with the increasing specific water flow. Smaller SDAS in the billet center leads to lower segregation index of carbon (r C ) and manganese (r Mn ) due to the low permeability in the final solidification stage. The measured r Mn and r C in billets are in an approximately linear relationship. In addition, for the same rolling and cooling process, the severer carbon segregation in the center of the billets is, the lower the sorbite rate of the rods and the worse stability in the mechanical property of the rods. The tensile strength of wire rods can be improved by adjusting the casting parameters to decrease the SDAS and reduce the central carbon segregation of the billets.

Effect of Single Power Two Circuits Electroslag Remelting Process on the Ingot Solidification Quality

“…According to the previous research, the shorter SDAS can result in a lower segregation. Reducing the remelting rate is an effective method to reduce SDAS and segregation during the ESR process.…”

Method of Verification of Carbon Segregation Ratio Determined with Experimental Methods

“…Depending on the steel chemical composition and casting conditions, the share of individual crystal zones varies. In extreme cases, a defective structure can be formed [9]. One of the most frequent defects that may occur when casting long strands is an axial porosity.…”

“…Note that this error is very likely to occur in the area that is the most interesting when investigating the segregation effect. Because of the observed inconvenience, many researchers prefer to take so-called "drill samples" and determine the chemical composition with a LECO analyser [9]. However, this method also has some deficiencies, as the sampling method itself causes averaging of the obtained result, and understating the value of the local carbon content may lead to incorrect conclusions (e.g., the assessment of cementite formation probability).…”

“…Today, it is difficult to expect an answer on the basis of a theoretical model only, and, therefore, experimental tests are still very relevant, both on a laboratory scale and an industrial scale. The published information [4][5][6][7][8][9] concerning the positive influence of electromagnetic stirrers on the reduction of carbon segregation in the continuous steel casting process shows that the mentioned direction of actions is very promising.…”

DETERMINATION OF THE VALUES OF MICROSTRUCTURAL AND MECHANICAL PARAMETERS OF A PEARLITIC 0.7%C-0.60/0.70%Mn STEEL WIRE ROD ENABLING TO ACHIEVE HIGH ABILITY TO DRAWING WITH THE USE OF LARGE CROSS SECTION REDUCTION

“…Inhomogeneities in the distribution of elements in the wire rod volume arise as a result of inheritance of interdendritic segregation and central segregation resulting from solidification of steel during continuous casting. If specific casting parameters are not used to minimise micro-and macro-segregation of elements (low liquid steel overheating, effective electromagnetic stirring, and distribution of spray cooling intensity adjusted to the steel grade and ingot cross-section), this clearly affects the possibility of obtaining homogeneous wire rod properties, both on the cross section and along the length [17].…”