Study on the Formation of “A” Segregation in Steel Ingot

Abstract

D irect observatiolls oJ"A" segregatioll ill 3.5t salld mould cast illgots. which were dumped at 40 alld J 20 mill after pourillg. respectively, were made to discuss theJormatioll mechanism oJ " A " segregatioll. takillg the results of temperature measuremellt illio consideratioll. Alld a simulatioll test oJ" A " segregation was also succesifully made by mealls oJ hori ::,olltal unidirectiollal solidification oJ J 4 kg illgots. " A " segregatiolls re/Jroduced ullder several cooling cOllditiolls were illvestigated Jrom the viewpoillts oJ coolillg all.d solidification rates. The results obtained arc as Jollows. (1) " A" segregation was Jound to be Jormed at Ih e solidificatioll Jrollt where the solidJraction rangedJrom 0.30 to 0.35_ The term" solidification Jrunt" refers to the inte~race between a solid-like ZOlle alld a liquid-like ZOlle in the solid-liquid region. (2) The solute-enriched interdendritic liquid metal call flow illto the strings evell when the solid Jraclioll in the neighborhood is 0.7. (3) The transition oJ "A " segregation ZOlle to " V " segregatioll ::.one is caused by a suction effect. (4) Solidification ill "A" segregatioll p roceeds outwards Jrom Ih e inside. (5) The inclillation of " A" segregation is determilled by the vector sum oJ the advancing rate oJ the solidificatioll Jrollt alld the floa tillg velocity oJ solute-enriched liquid metal. (6) The critical condition Jor the Jormat ioll ~r "A " segregatioll oJ O.7 % C steel call be exp ressed by IheJoliowillgJormula; R£~8.75. (7) The size oJ" A " segregation spots is determinedJrom the stayillg time in the solid-liquid regioll.

Effects of dilute substitutional solutes on interstitial carbon inα-Fe: Interactions and associated carbon diffusion from first-principles calculations

“…Based on the above analysis, it is easily reminiscent of the occurrence of carbon micro-segregation in high Mn steels 4,5 . Although the interactions in practice are not the same as those in our case where the Mn and carbon are dilute, we can still draw some information from our current calculations for the first step to understand the nucleation of the carbon microsegregation around Mn.…”

The Position Study of Heavy Reduction Process for Improving Centerline Segregation or Porosity With Extra‐Thickness Slabs

“…Takahashi et al proposed that the solid–liquid coexisting zone of a solidified alloy was classified into three zones of semi‐liquid region, liquid–solid‐region in which the interdendritic liquid could flow, semi‐solid region. Takahashi found the semi‐liquid region was about 0.3–0.4, while Suzuki and Miyamoto thought of the semi‐solid region was more than 0.7. However, depending on the casting format and steel grade, the suggested soft reduction position could differ significantly from case to case, e.g.…”

Simulation of macrosegregation in a 2.45-ton steel ingot using a three-phase mixed columnar-equiaxed model

“…This relative motion can arise from thermosolutal convection, shrinkage-induced feeding flow, flotation and sedimentation of free moving crystals, mechanical or electromagnetic stirring, flow induced by pore or gas bubble formation, deformation of the solid skeleton, and capillary force-induced flow [1] . A lot of experiments were done to study the macrosegregation in steel ingots [2–4] . The typical segregation pattern in a steel ingot consists of a positive segregation in the upper region, a conic negative segregation in the lower region, V-segregates along the centreline, and A-segregates in the middle radius region between the casting outer surface and the centreline [5,6] .…”

“…Researchers have been investigating the mechanism of formation of A-segregation (channel segregation) for decades, and various mechanisms have been suggested [4,16,17] . The most accepted mechanism supports that the main factor in producing A-segregation is the flow of the segregated melt within the mushy zone, which is primarily controlled by both the alloy composition and the thermal conditions prevailing during the solidification process.…”