Evolution of A-Type Macrosegregation in Large Size Steel Ingot After Multistep Forging and Heat Treatment

Loucif, Abdelhalim; Fredj, Emna Ben; Harris, Nathan; Shahriari, D.; Jahazi, Mohammad; Lapierre-Boire, Louis-Philippe

doi:10.1007/s11663-018-1255-2

Cited by 19 publications

(16 citation statements)

References 16 publications

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“…Among them, macrosegregation, defined as chemical heterogeneity on the scale of the entire ingot, is one of the most important, particularly in high alloyed steels. Such compositional variation over large distances results in local changes in mechanical properties, which may lead to reduced ingot quality and sometimes even to ingot rejection [1,2]. While the severity of macrosegregation could be significantly reduced in small to medium size ingots through subsequent homogenization and forging operations; the situation is more complex when it comes to large size ingots.…”

Section: Introductionmentioning

confidence: 99%

On the Effect of Filling Rate on Positive Macrosegregation Patterns in Large Size Cast Steel Ingots

et al. 2018

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The effect of filling velocity on positive macrosegregation in large size steel ingots was studied. Macrosegregation and macro/microstructures were characterized on the hot-tops and a portion of the upper section of two ingots. The measurements revealed that segregation features in the two ingots varied as a function of the alloying elements, and that the severity of positive macrosegregation in the casting body was reduced when the filling rate was increased. It was also found that at the higher filling rate, grain morphologies in the first solidified zones of the ingot changed from columnar to equiaxe, and secondary dendrite arm spacing (SDAS) became slightly smaller in the intermediate and final solidified zones. The experimental findings were analyzed in the framework of diffusion and convection-controlled solidification, as well as liquid metal flow theories. The solute dependence of segregation features was related to the difference in the solid-liquid partition coefficient and diffusion capability of each element in the liquid iron. Calculation of Reynolds numbers (Re) during the filling process, for both ingots, showed that higher filling velocity caused more instable movement of the liquid metal in the initial solidification stage, resulting in the modification of grain morphology, as well as accelerated solidification rate.

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Section: Introductionmentioning

confidence: 99%

On the Effect of Filling Rate on Positive Macrosegregation Patterns in Large Size Cast Steel Ingots

et al. 2018

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“…In recent years, with the growing industrial demand for ever larger parts, the forged blocks have significantly increased in size. Therefore, during the quench process, significant temperature gradients are produced that result in a variety of microstructures, such as martensite, bainite and retained austenite through the thickness of the large-size block [ 4 , 5 ]. The hard martensitic phase is generally located near the surface region with the proportions of bainite and retained austenite increasing with the thickness [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

Retained Austenite Decomposition and Carbide Precipitation during Isothermal Tempering of a Medium-Carbon Low-Alloy Bainitic Steel

2018

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The effect of isothermal tempering on retained austenite decomposition and carbide precipitation were investigated in a medium-carbon low-alloy bainitic steel. High-resolution dilatometry was used to perform isothermal tempering at 350 °C, 550 °C and 600 °C for different holding times up to 16 h. The decomposition of retained austenite, morphology and composition of carbides were investigated by analyzing the dilatometric curves and were confirmed through scanning and transmission electron microscopy observations. The decomposition behavior of retained austenite varied significantly as a function of the tempering temperature with a full decomposition observed at 600 °C. It was also found that by increasing the tempering temperature from 550 °C to 600 °C, carbides precipitate approximately twice as fast, and evolve from M3C type to Cr7C3 and Cr23C6 after 16 h of tempering at 600 °C.

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“…It is difficult to eliminate during heating and rolling [4,5]. Many studies [6][7][8][9][10][11][12][13][14][15][16] suggested that centerline segregation decreases the mechanical performance of final products, such as: Low temperature toughness, weldability, and resistance to sour gas worsen; delamination fracture and band structure increase. References [17][18][19][20] suggested that control of centerline segregation in continuously cast slab can effectively improve low temperature toughness and elongation of pipeline steel.…”

Section: Introductionmentioning

confidence: 99%

Controlling Variability in Mechanical Properties of Plates by Reducing Centerline Segregation to Meet Strain-Based Design of Pipeline Steel

Guo

Liu

Wang

et al. 2019

Metals

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Low variability in mechanical properties is required for pipeline project designs to meet a strain-based design, which is used in regions of large ground movements. The objective of this study is to elucidate the influence of centerline segregation in continuously cast slab on variability in the mechanical property of pipeline steel, and controlling centerline segregation can meet the requirements of a strain-based design. Mannesmann rating method was used to evaluate the degree of segregation of two slabs and its effect on variability in mechanical properties of corresponding plates. Microstructural characterization indicated that bainite/martensite was formed in a segregated area where the content of C and Mn enriched. The mechanical property results indicated that controlling the degree of centerline segregation can reduce tensile strength variability and improve ductile-brittle transition temperature (DBTT).

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Evolution of A-Type Macrosegregation in Large Size Steel Ingot After Multistep Forging and Heat Treatment

Cited by 19 publications

References 16 publications

On the Effect of Filling Rate on Positive Macrosegregation Patterns in Large Size Cast Steel Ingots

On the Effect of Filling Rate on Positive Macrosegregation Patterns in Large Size Cast Steel Ingots

Retained Austenite Decomposition and Carbide Precipitation during Isothermal Tempering of a Medium-Carbon Low-Alloy Bainitic Steel

Controlling Variability in Mechanical Properties of Plates by Reducing Centerline Segregation to Meet Strain-Based Design of Pipeline Steel

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