Recrystallization and mechanical properties of microalloyed cold-rolled steel

Abstract

Cold-rolled microalloyed steels have proven themselves in many applications. Here microalloying fulfills different metallurgical functions that can be used to produce high-strength or very mild deep-drawing steels. This article studies the recrystallization behaviour of microalloyed steels during anneals performed in the laboratory and in the production shop. The delay in recrystallization compared with unalloyed steels can be explained by the amount and distribution of precipitated carbonitrides and also by dissolved microalloying elements. The mechanical properties of the cold-rolled, high-strength steels are determined mainly by grain refinement and, depending upon the annealing process, to a smaller extent by precipitation hardening. With complete fixation of all the interstitial atoms and, at the same time, minimization of the amount of precipitates very mild special deep-drawing steels can be made. Rekristallisation und mechanische Eigenschaften von mikrolegierten kaltgewalztenSUihlen. Mikrolegierte kaltgewalzte Stahle haben sich fur viele Anwendunqstalle oewahrt, Dabei erfullt die Mikrolegierung unterschiedliche metallphysikalische Aufgaben, die zur Herstellung hochfester oder aber auch besonders weicher Tietzlehstahle genutzt werden kbnnen. In dieser Arbeit wird das Rekristallisationsverhalten mikrolegierter Stahle in Labor-und BetriebsglLihungen untersucht. Die im Vergleich zu unlegierten Stahlen auftretende Rekristallisationsverzbgerung kann durch Ausscheidungsmenge und -verteilung der Carbonitride und auch durch gelbste Mikrolegierungselemente erklart werden. Die mechanischen Eigenschaften der kaltgewalzten, hochfesten Stahle sind vorwiegend durch Kornfeinung und, je nach GILihprozeB, in geringerem Umfang durch Aushartunq bestimmt. Bei vollstandlqer Abbindung aller interstitiellen Atome bei gleichzeitiger Minimierung der Ausscheidungsmenge lassen sich besonders weiche Sondertiefziehstan Ie herstellen.

Ultrahigh Strength Steel: Development of Mechanical Properties Through Controlled Cooling

“…Grain refinement is achieved either by fine precipitates which pin the austenite grain boundaries by micro alloys (Tanaka, 1981;Umemoto et al, 1987). Precipitation of carbides and carbonitrides both at high temperatures or during cooling and tempering helps to improve the mechanical properties for specific needs (Bleck et al, 1988). Ductility and toughness suffer in most methods of strengthening when one tries to increase strength.…”

“…Accelerated cooling results in the formation of mostly martensite phase. The combine influence of alloying elements and thermomechanical treatment allows to exploit of different mechanisms of strengthening, such as precipitation hardening, grain refinement, and transformation hardening by means of bainite and martensite transformations (Bleck et al, 1988). Although, application of thermomechanical treatment especially to high strength low alloy steel (HSLA) is known, little systematic work has been carried out with application of this technique to ultra high strength steels (UHSS) (Jahazi & Egbali, 2000).…”

Study of the kinetics of the recrystallization of cold-rolled low-carbon steel

“…[1] can be verified by checking the invariance The f (␣ ) functions can be derived on the basis of different of the y(␣ ) and z(␣ ) plots with respect to process variables, models of the reaction interface movement, and their corressuch as heating rate, that test the isokinetic hypothesis upon ponding mathematical expressions are well known. [5] From which the equation is built.…”

“…any given heat, it is necessary to establish the kinetics of While isothermal experimental analysis techniques are, the recrystallization process. [1,2,3] Thermal analysis methods in most cases, adequate for kinetics analysis, nonisothermal such as differential thermal analysis (DTA) and differential thermoanalytical techniques have several advantages. The scanning calorimetry (DSC) have been widely employed to rapidity with which nonisothermal experiments can be perdetermine the evolution of the transformed fraction with formed makes this type of experiment attractive.…”

Influence of Stresses on Precipitation

“…Indeed the kinetics of Ostwald ripening is affected if the coarsening particles are interconnected by dislocations or grain boundaries, and respective theoretical models are available [21,23]. However, during plastic straining dislocations move and attach and detach themselves to and from particles, i.e.…”