Effect of Continuous Casting Parameters on Quality of Billets Manufactured by UMMC Steel LLC

Abstract

The analysis of the production records on casting 150õ150mm billets at UMMC Steel LLC has made it possible to define the basic factors worsening the billet quality and increasing the rejection of the rolled materials: steel casting in case the sulfur and phosphorus content exceeds 0.015 % and overheat is more than 30°Ñ. In order to minimize the formation of local nonuniformity in the billets manufactured from low carbon and medium carbon steel, open cast by CCM, it is necessary to maintain a maximum [Mn]:[S] ratio with [Mn]:[Si] ratio at the level less than 2-3, which ensures the formation of fusible deoxidation products and prevents the formation of solid conglomerates in steel. In order to reduce the formation of axial porosity it is advisable to retain the carbon content at the lower limit for the steel grade and avoid overheating of steel above the specified values. In order to minimize the consequences of the overheated steel casting it is necessary to adjust the billet casting rate in accordance with the operating procedures.

Improvement of the secondary cooling mode for continuous casting of round billets at Ural Steel JSC

“…However, within the range of whole examined party, amount of templates with exceeding of maximal ball achieves 15.5 % (by axial porosity) and 18.5 % (by internal hot cracks). It is shown that high axial porosity is caused by steel casting with increased overheating [16,19,26], while substantial development of internal hot cracks testifies on irrational procedure of secondary cooling [1-4, 6-11, 15, 18].…”

“…The temperature and speed casting parameters (see Table 2) vary in wide range, while the maximal overheating values exceed the level which is present by the technological specification: 15-30 °С for more than 10 % of melts. Casting with increased overheating values supports development of axial segregation and porosity, as well it can be the cause of forming internal and surface cracks which appear in the conditions of essential thermal stresses inside metal [5,[11][12][13][16][17][18][19][20][21][22][23][24][25][26]. Increased metal overheating in the tundish can be partly compensated by decrease of casting speed; however, it leads to reducing of continuous caster productivity and has negative reflection on a billet quality due to varying of thermal conditions of solidification.…”

“…At the same time, despite the large amount of publications devoted to this theme, the problems of quality improvement of continuously cast billet and optimization of technical and economical casting parameters can be solved in general individually in each single case. Thereby scientific and technical literature includes a lot of publications describing simulation of the heat state of a continuously cast billet [8,9,[12][13][14][15][16], as well as the results of investigations aimed on modernization of equipment and improvement of technologies for continuous casting in different production conditions: Pangang Group Chengdu Steel (China) [9], Hebei Iron & Steel Group (China) [10,17], Xingtai Steel (China) [18], Panzhihua Steel (China) [19], Zhongyuan Special Steel (China) [20], Voestalpine Stahl (Austria) [21,22], "Ural Steel" (Russia) [23][24][25], "UMMC-Steel" (Russia) [26], Mini-metallurgical plant "ISTIL" (Ukraine) [27].…”

Improvement the Round Bloom Continuous Casting Technology at JSC “Ural Steel”

“…As you know, the quality of billets is determined by the continuous casting parameters [3][4][5][6][7][8][9][10][11][12][13][14][15][16], liquid steel properties and the design of a continuous casting machine (CCM). Therefore, despite the large number of continuous steel casting studies , the study of casting technology and bloom quality in specific production conditions allows us to obtain new patterns and improve the production technology.…”

“…Bloom quality is influenced by a large number of factors. When analyzing the operation of a particular CCM, the liquid steel properties and casting parameters have a decisive influence on the billets quality [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The chemical composition of the steel and casting parameters are shown in Table 2.…”