Papers by Keyword: Batch Annealing

Abstract: The variation of microstructure of Ti-IF steel of extra deep drawing grade, which having a 83%cold-rolled deformation under simulated batch annealing process at temperature ranging from 480°C to 750°C, was studied by using optical microscopy, X-ray diffraction (XRD) and metallographic micro-hardness tester. The evolution of texture during the recrystallization process was analyzed by Orientation Density Function (ODF). The results show that, the recrystallization temperature of experimental steel is 620-630°C, and the recrystallization process can be accomplished within 1h at660°C. Four major textures after cold rolling are observed as follows,{001}<110>, {111}<110>, {111}<112> and {112}<110>, respectively. At the early stage of recrystallization annealing, texture evolves from {111} toγ-{111}, which is quite beneficial to achieve high deep drawing performance,the texture {001}<110> and {112}<110> change marginally. as the annealing temperature rises up to 720°C, texture {001}<110> and {112}<110> change into fiber textureγ-{111}. After annealing,{111}<112> and {111}<110> textures become the two main types.

Abstract: Microstructure and microtexture evolution during batch annealing of warm-rolled Ti-IF steel sheets were investigated in this paper. It was founded that α fiber texture and the relatively weak γ fiber texture were formed in warm-rolled and air-cooled Ti-IF steel sheets. In the early stage of recrystallization, the {111} recrystallization texture was formed from the deformed {111} grains in warm-rolled Ti-IF steels. In the later stage of recrystallization, the α fiber texture was consumed and the γ fiber texture in recrystallized grains was further developed. The main recrystallization texture characteristics of warm-rolled Ti-IF steel sheets had been decided in the early stages of recrystallization, and the oriented nucleation mechanism played a leading role in the formation of recrystallization texture in warm-rolled Ti-IF steel sheets.

Abstract: Based on the experimental materials of hot rolled Ti+Nb-IF steels and Ti-IF steels produced in the industry, the effects of cold reduction ratios on its microstructures, mechanical properties and textures were investigated. The results show that experimental samples with different cold reduction ratios have been finished recrystallization by batch annealing at 720°C and soaking with 5h. As the cold reduction ratio increases, the grains will be refined and uniform, and the textures trends to be {111} texture. The {223}<110>, {111}, and {114}<110> textures appeared after cold rolling are inherited followed by annealing, whose intensities would be higher as the cold rolling ratio increased. And the textures will transform to the {223}<110>, {111}<110> and {114}<110> textures. With the increasing cold reduction ratio, the values of the yield strength R_p0.2 and tension strength R_m increase, but the R_p0.2 is almost about 100MPa. However, the strain hardening index n₉₀ gradually decreases. The plastic strain ratio r₉₀ which reaches the maximum with cold reduction ratio of 70% increases firstly and then decreases. Thus, the optimal cold reduction ratio of 70% to 80% is determined, which can obtain good deep drawing performances.

Abstract: Effects of steel composition and coiling temperature on textures of a series of high strength IF steels were studied. An intermediate coiling temperature (6200C), instead of a high coiling temperature (7100C), was found most beneficial for the steels containing moderate to high phosphorus content. On the other hand, high coiling temperature was found beneficial for the steels containing low amount of phosphorus.

Abstract: Hot rolled high plastic stain ratio structural steel sheets was used to study the effect of cold reduction ratio and annealing process on the microstructures and mechanical properties. The results showed that the structural steel sheets was recrystallize finished after cold rolling follow different cold reduction ratio and batch annealing(annealing temperature 670°C and soaking time 5h) under experimental condition. When the cold reduction ratio was increased, the yield strength and tension strength increase, the elongation reduced followed different heating speed. The plastic strain ratio r value reached the maximum with cold reduction ratio of 50%, when the cold reduction ratio was increased, the r value was gradually reduced, However, the strain hardening exponent n value was gradually reduced. In the end, that suggested the optimal cold reduction ratio is 40% to 50%, and heating speed is 20°C/h, consequently that obtained good match of mechanical properties and punching property.

Abstract: A discrete event simulation approach based on heuristics is presented to emulate the production process of the bell-type batch annealing in this paper. For optimizing the scheduling objective of minimizing the resource free ratio, an improved Differential Evolution algorithm is proposed, which solves a class of discrete problem, and whose crossover probability is adaptively assigned in order to improve the search ability not only on local but also on global. The experiments using practical production data demonstrate that the proposed method has a great effectiveness, and increases the production efficiency of the bell-type annealing shop.

Abstract: The development of TRansformation Induced Plasicity (TRIP) steels has seen much activity in recent years, due to the promise of very high formability combined with high strength. The accepted method for production of as-hot-rolled TRIP steel employs multistage runout table cooling and coiling in the bainitic transformation temperature regime. As an alternative to confronting the production difficulties the accepted strategy presents, a program was begun to evaluate the potential of 0.1C-6.0Mn steels processed in a more conventional manner. Three laboratory heats were melted to consider the effect of manganese content on processing and properties. The steels were found to be fully hardenable with conventional hot-strip mill processing and subsequent batch annealing simulations produced significant retained austenite levels. The combination of the prior martensitic microstructure in the as-hot-rolled condition, and austenite created during annealing, resulted in remarkable combinations of strength and ductility. In the as-hot-rolled condition, tensile strengths exceeding 1400 MPa were observed, with total elongations of approximately 10 percent. Optimum properties were found when samples were annealed at approximately 650°C. While this treatment reduced the tensile strength to 800-1000 MPa, the total elongation increased to between 30 percent and 40 percent. UTS*TE products exceeding 30,000 MPa-% were observed, making these materials attractive for high strength, high ductility applications.

Abstract: The effect of heating rate and annealing time on the microstructure and texture of a commercial 0.04 %C steel, cold rolled up to 80 %, is studied. Samples have been isothermally annealed at various heating rates (12 °C/h, 20 °C/h, 40 °C/h and 650 °C/min) and then soaked at 700 °C for 15 hours. The microstructural evolution of the samples during the heating process and hold period has been followed by optical microscopy, scanning and transmission electron microscopy. The electron back-scattered diffraction technique is used to reveal the texture of the samples. Tensile tests and hardness measurements are correlated with the microstructural features. Results show that (a) recrystallization occurs between 600 and 650 °C; (b) a “pancake” structure develops during recrystallization at low heating rates without appreciable grain growth; (c) samples heated at 650 °C/min exhibit an equiaxed grain structure and significant grain growth; (d) only at low heating rates the material develops a strong {111} recrystallization texture, in ccordance with the high plastic anisotropy found by mechanical testing.

Abstract: In order to optimize the batch annealing cycles and increase the productivity of this process, the impact of the chemical composition and the processing parameters on the recrystallisation and grain growth kinetics were investigated on different Ti IF steels. A simple model based on an Avrami formulation has been developed for the prediction of the recrystallisation kinetics.