Effect of Structure Factor on High-Temperature Ductility of Pipe Steels

Abstract

Effects of various factors such as the grain size, the morphology of nonmetallic inclusions, and joint microalloying with boron and titanium on the high-temperature ductility of pipe steels are studied. Physical modeling of the conditions of cooling of the skin of a continuous-cast preform in the zone of secondary cooling in a Gleeble facility is performed. Technical recommendations are given for raising the hot ductility of steels under industrial conditions. Key words: hot ductility, continuous casting of steel, physical modeling, pipe steel. INTRODUCTIONReported data on carbon and alloy steels show that ductility drops in continuously cast metal occur in the temperature range of 750 -1050°C [1 -4]. When the crystallization is accompanied by additional impacts on the metal, for example, in the form of thermal or deformation cycles typical for the skin of solidified metal in the zone of secondary cooling in continuous casting machines, the temperature range of the ductility drop widens and deepens [5 -7]. It has been shown in [7,8] that ductility drops typical for the stage of cooling of steel in a continuous casting machine do not manifest themselves during subsequent hot rolling, and the studied pipe steels possess high ductility.The aim of the present work was to test the methods of grain refinement in the process of cooling of the skin of a slab in a continuous casting machine for raising the ductility of the continuously cast metal and to study the changes in the morphology of nonmetallic inclusions in heating for rolling and the effect of microalloying with boron and titanium on the ductility of steels.

Evolution of non-metallic inclusions during heat treatment

“…Uncontrolled non-metallic inclusions in steel may have detrimental effects on mechanical properties such as strength, toughness, and ductility [1][2][3][4][5][6]. Generally, characteristics of the inclusions are modified and optimized by refining slag, calcium treatment or rare earth treatment in molten steel to minimize their harmfulness and eliminate nozzle clogging during casting [7][8][9][10][11][12][13].…”

Improving the Quality of Parts Produced by Bending in a Die with an Elastic Element

“…The process of bending parts in a die with an elastic element was investigated. Calculation of theoretical and practical angles of the spring-back were made, as well as comparison of them in percent [23][24]. Was identified that the use of an elastic element reduces the angle of the part's spring-back.…”

Hot Axial Rotary Forging of Flanges Standard EN 1092

“…Manufacturing a finished flange according to the standard pr EN 1092-1 from a rotary forged billet with incomplete filling of the flange profile along the inner diameter is possible with an increase in the allowance in the lower part of the flange or an additional operation of cold rolling from the flange end, which can, in addition to filling the profile, improve the metal structure of the thick part of the flange [17,18,19,20,21,22].…”