Annealing Of Low-carbon Steel Research Articles

Effect of Cold Reduction Rate on Ferrite Recrystallization Behavior during Annealing in Low-Carbon Steel with Different Initial Microstructures

We investigate the effect of the cold reduction rate on ferrite recrystallization behavior during the annealing of low-carbon steel with different initial microstructures. Three types of hot-rolled sheet specimens are prepared: specimens P, B, and M, which consist of ferrite and pearlite, bainite, and martensite, respectively. To evaluate the effect of the cold reduction rate on ferrite recrystallization behavior, hot-rolled sheet specimens are cold-rolled at cold reduction rates of 40% and 67%. The cold-rolled sheet specimens are heated to the target temperature, and then water-quenched to room temperature. Irrespective of the initial microstructures, the ferrite recrystallization is accelerated by increasing the cold reduction rate. In addition, the dislocation densities of specimens P and B increase at the larger cold reduction rate, which accelerates ferrite recrystallization in these specimens. In the case of specimen M, the dislocation arrangement parameter remarkably decreases at the larger cold reduction rate, whereas the dislocation density hardly changes. Thus, we conclude that the accelerated ferrite recrystallization at the larger cold reduction rate for specimen M can be mainly attributed to an increase in the amount of interactions between dislocations in the specimen.

Effect of Initial Microstructures on Austenite Formation Behavior during Intercritical Annealing in Low-Carbon Steel

Effect of Initial Microstructures on Austenite Formation Behavior during Intercritical Annealing in Low-Carbon Steel

Spheroidization heat treatment and intercritical annealing of low carbon steel

Spheroidization annealing of low carbon steel and its effects on the microstructure and mechanical properties of dual phase (DP) steel were studied. It was revealed that the reduction in strength and hardness of the quenched martensitic microstructure was much more pronounced compared to the fully annealed ferritic-pearlitic banded microstructure with spheroidizing time. This was related to the confinement of spheroidized carbide particles to distinct bands in the latter, and the uniform dispersion of carbides and high-temperature tempering of martensite in the former. During intercritical annealing of the spheroidized microstructures, the tendency to obtain martensite particles as discrete islands was observed. This, in turn, resulted in an inferior strength-ductility balance compared to the DP steel obtained from the intercritical annealing of martensite, which negated the usefulness of the spheroidized microstructures as the initial microstructures for the processing of DP steels.

Effect of Initial Microstructures on Austenite Formation Behavior during Intercritical Annealing in Low-Carbon Steel

Effect of Initial Microstructures on Austenite Formation Behavior during Intercritical Annealing in Low-Carbon Steel

Microstructural Evolution During Cold Rolling and Subsequent Annealing in Low-Carbon Steel with Different Initial Microstructures

Microstructural evolution during cold rolling and subsequent annealing of low-carbon steel with different initial microstructures was investigated from the perspective of the competitive phenomenon between recrystallization of ferrite and reverse phase transformation from ferrite to austenite. Three kinds of hot-rolled sheet specimens were prepared. Specimen P consisted of ferrite and pearlite, specimen B consisted of bainite, and specimen M consisted of martensite. The progress of recovery and recrystallization of ferrite during annealing was more rapid in specimen M than that in specimens P and B. In particular, the recrystallized ferrite grains in specimen M were fine and equiaxed. The progress of ferrite-to-austenite phase transformation during intercritical annealing was more rapid in specimen M than in specimens P and B. In all specimens, the austenite nucleation sites were mainly at high-angle grain boundaries, such as those between recrystallized ferrite grains. The austenite distribution was the most uniform in specimen M. Thus, we concluded that fine equiaxed recrystallized ferrite grains were formed in specimen M, leading to a uniform distribution of austenite.

Validation and predictions of coupled finite element and cellular automata model: Influence of the degree of deformation on static recrystallization kinetics case study

Validation and further application of a coupled cellular automata – finite element model to investigate the influence of the degree of deformation on static recrystallization kinetics (SRX) during annealing of low carbon steels after cold rolling is presented within the work. Descriptions of major model components involving digital material representation finite element model as well as cellular automata approach for explicit static recrystallization simulations are presented. Obtained SRX results for various heating rates after 65% rolling reduction are validated with experimental data to assess the model’s predictive capabilities. Finally, the validated model is used to investigate the influence of inhomogeneous energy distribution, obtained in the sample after rolling to 35, 50 and 65% reductions, on static recrystallization kinetics and grain size evolution.

Effect of Starting Microstructure through Severe Plastic Deformation and Ultra-Rapid Annealing of Low-Carbon Steel

In this research, low-carbon steel sheets with two different microstructures containing carbides (as-received steel) and pearlites (austenitized steel) are subjected to severe plastic deformation (SPD), and ultra-rapid annealing (URA) is applied with the heating rate of 200 °C s−1 up to the intercritical temperature near Ac1. Microstructure of SPDed as-received steel after URA is consisted of fully refined ferrite grains surrounded by fine pearlites; but for SPDed austenitized steel, grain refinement is not observed, and microstructure is consisted of martensite and high fraction of coarse non-recrystallized ferrite. Presence of carbides for SPDed as-received steel leads to strong interaction between ferrite recrystallization and ferrite transformation to austenite, which causes to refined final microstructure after URA. However, initial pearlites in SPDed austenitized sample prevent the occurrence of strong interaction during URA. For austenitized sample, URA of SPDed steel increases the strength and ductility about 28 and 12%, respectively. Also, for as-received sample, it increases the strength about 32% but decreases the ductility about 11%.

Improvement in the spheroidizing annealing of low-carbon steel for cold upsetting

A new method has been developed for more intense spheroidization of cementite. The method employs preliminary conversion of the steel to bainite structure. Spheroidization is produced by nonisothermal holding at high temperatures, by means of an internal heat source, so as to ensure the Geveling effect. This method may be used in production lines.

Nanocrystalline steel processed by severe rolling of lath martensite

Nanocrystalline steel was developed by severe cold-rolling and subsequent annealing of low carbon steel with an original microstructure of lath martensite. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that steel with an average grain size of −20 to −300 nm can be obtained. The tensile tests revealed that the steel with grain size of −20 nm possess a strength of 2520 MPa and poor ductility at ambient temperature.

Investigation of the structural changes in Widmanst�tten ferrite during the annealing of low-carbon steel

Transformation of austenite by a shear mechanism in an intermediate range leads to the formation of structures consisting of plate and acicular ferrite. The acicular structure of Widmanstatten ferrite has not found practical application and has not been adequately studied, although the inherited effect of this structure in lowering the ductility of steel is of practical importance. The present article is devoted to a detailed analysis of this structure and its effects.

Development of {111} Texture in Intercritical Annealing of Low Carbon Steels

Effects of the volume fraction of γ phase on {111} texture development have been investigated by making use of several extra low carbon sheet steels which were intercritically annealed in alpha plus gamma two phase region. The results obtained are summarized in the following.(1) {111} texture developed with increase in volume fraction of γ phase. {111} component had two maxima; first at the γ fraction below 50% and second at the fraction above 60%.(2) The similar relation to (1) was obtained between the Lankford value and γ fraction.(3) The development of {111} annealing texture was stronger in a thinner specimen than in a thicker one, and on the surface than on the midsection.(4) During slow cooling after intercritical annealing, {111} component increased and {100} component decreased.(5) In the residual α phase, {111} texture evolved with increase in γ fraction, and had a maximum between 60 and 90% of transformed γ phase.(6) These results were reasonably understood on the basis of a new theory, proposed by the present authors, on the formation mechanism of the transformation texture.

Investigation of structure and texture development during annealing of low-carbon steel

The effect of carbon in different states of dispersion has been examined in relation to its effect on the texture formed during the annealing of cold-rolled steel sheet. Quantitative texture analyses using orientation distribution functions have been combined with detailed metallographic investigation of changes taking place during recrystallization. Calculations have also been carried out on the rate of dissolution of carbon from cementite particles for a range of relevant conditions. Dissolved carbon present before cold rolling greatly reduces the final annealed {111} texture strength and leads instead to a spread around the Goss orientation. Dissolved carbon present with manganese during annealing also reduces the final {111} intensity, tending to replace it with a number of relatively weak minor components; this is observed during conditions of slow heating, or when primary carbide particles are numerous, and seems to be associated with a significant nucleation rate of new grains during the later stages of recrystallization.MST/389

Investigation of structure and texture development during annealing of low-carbon steel

The effect of carbon in different states of dispersion has been examined in relation to its effect on the texture formed during the annealing of cold-rolled steel sheet. Quantitative texture analyses using orientation distribution functions have been combined with detailed metallographic investigation of changes taking place during recrystallization. Calculations have also been carried out on the rate of dissolution of carbon from cementite particles for a range of relevant conditions. Dissolved carbon present before cold rolling greatly reduces the final annealed {111} texture strength and leads instead to a spread around the Goss orientation. Dissolved carbon present with manganese during annealing also reduces the final {111} intensity, tending to replace it with a number of relatively weak minor components; this is observed during conditions of slow heating, or when primary carbide particles are numerous, and seems to be associated with a significant nucleation rate of new grains during the later stages of recrystallization.MST/389

Development and control of annealing textures in low-carbon steels

The development of texture and plastic anisotropy (γ-value) during the annealing of low-carbon steel is described. The effects of various industrial processing parameters are considered as well as ...

Annealing behaviour of cold rolled low carbon steels

The recovery, recrystallization, and grain growth during annealing of low-carbon steels (high purity and commercial purity) following 80% cold rolling have been investigated. The relationship between the formation of recrystallization texture and the substructure developed during deformation and recovery is examined in this paper. The elastic stored energy is orientation dependent and the sequence estimated from a Fourier analysis of X-ray line broadening is V {110} > V {100} > V {111} for commercial purity steel and V {110} > V {111} > V {100} for high purity steel. The difference in the sequences may be connected with the distribution of dislocations between the cell walls and the inside of the cells. In high purity steel the high energy components recover rapidly, the {110} and {111} components strengthen, and the {100} component weakens during primary recrystallization and grain growth. In commercial purity steel the lowest energy {111} component recovers most rapidly. The textural changes during primary recrystallization and grain growth can be explained by the orientation dependence of recovery.

Kinetic studies on surface segregation of manganese during annealing of low-carbon steel

Surface segregation of manganese, an example of a selective oxidation process, occurs at annealing temperatures when low-carbon steel is in contact with typical commercial protective atmospheres. Laboratory kinetic studies show that the enrichment process follows a parabolic rate law, that the rate constant in the low range of oxygen potential for the annealing atmosphere increases linearly with oxygen potential, and that although higher rates apply for relatively high-manganese steels than for relatively low-manganese steels, the same surface-reaction mechanism applies. A rate expression was developed that implicitly includes oxygen potential and free manganese (uncombined, in solid solution) content in the steel.

Effect of heating rate on the recrystallization texture of low-carbon steel 08 kp

1. After continuous rapid annealing of low-carbon steel 08 kp the texture that is characteristic of cold rolling is superposed on the preferred orientation that is characteristic of prolonged recrystallization annealing, the principal component being {111} 〈112〉. None of the texture components is strongly developed, while the {111} 〈112〉 component is more developed after prolonged annealing. 2. The recrystallization occurring at higher temperatures in the process of continuous rapid heat treatment of low-carbon steel 08 kp probably creates better energy-supply conditions for the centers being fromed and, consequently, increases the probability of a structure with randomly oriented crystals. Prolonged heating in a batch furnace creates favorable conditions for an oriented arrangement of the new undistorted lattice in conformity with the deformation texture. 3. The use of rapid continuous heat treatment of sheet steel makes it possible to obtain metal with less anisotropy of the properties, which is of major importance in producing materials subject to different degrees of deformation.