材料加工外文翻译---影响温轧if钢剪切带形的纹理发展(编辑修改稿)

材料加工外文翻译---影响温轧if钢剪切带形的纹理发展(编辑修改稿)内容摘要：

quite as obvious. It is, therefore, the purpose of this brief review to single out the mechanisms that influence the above properties and to explain how their operation (or suppression) can lead to improvements in rvalue and formability. 2. Background It has been known for some time [2] that ferrite deformed just below the Ar3 and Ar1 temperatures is actually softer than austenite deformed above the Ar3 temperature. Thus, the deformation of ferrite at temperatures down to about 700176。 C, in plain C steels, and 600176。 C, in IF steels, does not involve increases in rolling load above the design limit for the mill in question. While both plain C and IF steels can be readily warm rolled, only the latter materials permit the attainment of high rvalues, as indicated in Table 2. The high rvalues in turn require the presence of desirable texture ponents after annealing, such as the {1 1 1} rolling plane fibre and the {5 5 4} 2 2 5 [3]. Recent experiments [4, 5, 6 and 7] have led to some increase in the understanding of just how these desirable texture ponents are formed (in the IF steels) and of why they are absent (in LC steels). The experiments indicate that the important factor is the presence (in LC steels) or absence (in IF steels) of carbon in solution at warm rolling temperatures. The carbon in solution appears to cause dynamic strain ageing (DSA) in the rolling temperature range, which is then responsible for the unusually high strain rate sensitivities that characterize LC steel under warm rolling conditions. The high rate sensitivities in turn suppress the formation of shear bands in the ferrite. The presence of these microstructural features in warmrolled IF steels has been directly linked to the nucleation of the desirable {1 1 1} fibre on subsequent annealing. Conversely, their absence in warmrolled LC steels has been associated with the poor textures that are developed after warm rolling [6]. As this sequence of events is a fairly plex one, the results obtained in this series of investigations will now be summarized and discussed. . Experimental materials 13 In order to investigate the effects described above, three steels were examined, with the positions displayed in Table 3. The IF grade contained 50 ppm C and % Mn and was stabilized with % Ti. Two LC steels were studied, with 140 and 160 ppm C. A typical Mn concentration of % was present in the former, while the second was a very low Mn variant, with only %. The principal difference between the LC grades was that the low Mn variant was Alkilled. Table 3. Steel positions (wt.%) Fullsize table (1K) . Rolling schedules The steels were initially hot rolled down to a thickness of 11 mm and then air cooled. From these samples, taperedend specimens were prepared for laboratory warm rolling. The two LC grades were reheated to 740176。 C and then cooled to the rolling temperature in thermal insulation at about 7176。 C/min. The IF specimens were reheated to 800176。 C prior to rolling. The use of the tapered specimens meant that singlepass rolling could be employed. This led to a simulation of strip rolling (with regard to the shortness of the interpass times) that was considered to be more accurate than the alternative of reversing the pilot mill, which is more suitable for plate mill simulations. Further details of the experimental rolling procedures are provided in Refs. [4, 5 and 6]. . Metallographic results The occurrence of shear banding in the LC material at 700176。 C is depicted in Fig. 1a. (Similar results were obtained in the low Mn variant.) Only a few banded grains can be seen, and the bands themselves are quite thin and short, indicating that flow along them was retarded. These “stunted” bands were unique to the LC samples rolled at temperatures above 550176。 C. Fullsize image (15K) Fig. 1. Examples of ingrain shear bands in material warm rolled at 700176。 C to a reduction of 65% [5]: (a) LC steel。 (b) IF steel. The above behaviour contrasted sharply with that of the IF material. Here the nature of the bands was unaffected by the rolling temperature, so that the example of banding illustrated in Fig. 1b for 700176。 C is typical of all rolling temperatures. In this micrograph, the shear taking place along individual bands is made evident by the grain boundary displacements. The fraction of grains containing shear bands was determined 14 by a point counting technique [5]. The resulting data are presented in Fig. 2, from which it can be seen that the intensity of the banding, like its nature, was unaffected by the rolling temperature in the IF material. In the LC grades, however, the intensity of the banding was highly temperaturesensitive, droppingoff sharply when rolling was carried out above 400176。 C. Thus, at temperatures above 450176。 C, the IF steel contained more shear bands than the LC grades, while below 450176。 C, this relationship was reversed. Fullsize image (5K) Fig. 2. Influence of rolling temperature on ingrain shear band frequency [5]. . Texture . Rolling textures The deformation textures determined in the investigation described above are illustrated in the form of orientation distribution functions (ODFs) in Ref. [5]. (This type of presentation is described and explained in more detail in the above reference.) All of the textures were typical of ferrite rolling, in that they were characterized by a partial rolling direction (RD) fibre (containing grains with their 1 1 0 axes parallel to the RD) as well as a plete normal direction (ND) fibre (with grains having a 1 1 1direction parallel to the ND). Although the rolling textures were qualitatively similar, the higher intensities (or maxima) evident in the 700176。 C texture determined in the LC steel are significant and these will be taken up later in Section 3. By contrast, the。