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1.
AbstractThis paper analyses the effect of carbon and nitrogen content on the austenite microstructural homogeneity before transformation in the thin slab direct rolling of Nb and Nb–V microalloyed steels. The study was made with the help of a microstructural hot working model adapted to the metallurgical peculiarities associated with thin slab direct rolling. The results show that an increase in carbon content from 0·04 to 0·09% in 0·05%Nb microalloyed steels requires a significant increase in the initial rolling temperature in order to avoid the presence of isolated as cast austenite grains prior to transformation. Similarly, an increase in nitrogen content from 30 to 120 ppm does not imply changes as drastic as in the case of carbon. In both situations the changes required in the rolling temperature can be explained by the interaction between post-dynamic softening mechanisms and strain induced precipitation kinetics. In this context, the incidence of different final gauge thicknesses on microstructural homogeneity is evaluated. 相似文献
2.
《Materials Science & Technology》2013,29(4):404-409
AbstractThis paper is dedicated to the memory of Professor Sir Robert Honeycombe, who examined the first author's PhD thesis on this subject in 1972. The paper reviews some of the very large improvements in the understanding of the formation of textures and microstructures in drawing quality steels in both their deformed and recrystallised states made since the 1970s, focusing in particular on deformation bending in interstitial free steels. 相似文献
3.
《Advanced Robotics》2013,27(8):931-960
Two problems associated with the local rotatability of two types of fully parallel linearly actuated platform manipulators are investigated in this paper. The first problem is to find the physically allowable region that the movable platform can be freely rolled about any given direction at any specified position. The second problem is to evaluate the maximum angle that the movable platform can be tilted about any given position and orientation. The kinematic constraints involved in these problems are the stroke limitation of the linear actuators, the motion constraints of the passive spherical and universal joints, and the interference condition between the supporting limbs. A unified and computationally efficient approach for solving these problems which takes into account all of the kinematic constraints is developed. 相似文献
4.
《Materials Science & Technology》2013,29(11):1313-1320
AbstractGrain refinement has been achieved through large strain rolling (LSR) in Mg AZ31 alloy. The evolution of microstructure and texture has been found to be dependent on the amount of reduction. After the critical amount of reduction, grain refinement proceeds through continuous dynamic recrystallisation (CDRX). 相似文献
5.
《Materials Science & Technology》2013,29(8):955-960
AbstractIn wrought aluminium alloys, the fragmentation of coarse, iron bearing intermetallic particles by hot rolling is an important development in industrial processing. Here a model 3000 series alloy is used to show that fragmentation can occur prior to hot rolling, during the homogenisation heat treatment. Some fragmented particles display a curved morphology of break-up that results from matrix wetting of two phase (or 'duplex') interfaces in Al6(Fe,Mn) particles partially transformed to an α-Al–(Fe,Mn)–Si phase. In contrast, samples rapidly heated to temperature in a fluidised bath show an angular break-up indicative of tensile stresses induced by thermal expansion mismatch between the intermetallic particles and aluminium matrix. Although this break-up should not be industrially significant, the transformation induced break-up by wetting may be. More generally, internal boundaries resulting from the transformation to α-Al–(Fe,Mn)–Si phase may be mechanically weak fracture initiation points during hot rolling. 相似文献
6.
《钢铁冶炼》2013,40(4):332-342
AbstractThermomechanical treatment (TMT) is the simultaneous use of work hardening, and grain refinement along with solid solution and precipitation strengthening. In this investigation, four alloys, with a base composition of 0·28%C, 1·0%Mn, 4·2%Cr, 1·0%Mo, 0·34%V, were prepared by electroslag refining (ESR) and by addition of small amounts of Ti and Nb and by increasing Cr and V to 4·8 and 0·48% respectively. In two of the alloys a yield strength in excess of 1550 MPa was obtained in the as cast quenched and tempered condition. Attempts were made to further increase the yield strength by thermomechanical treatment. The process parameters for thermomechanical treatment were optimised by adopting procedures such as calculation of stability of precipitates, hot compression test, determination of cooling rates in different coolants, and modelling of TTT and CCT diagrams. The process involved prerolling of the ESR ingot to a bar at 1200°C, followed by hot rolling in two passes starting from 950°C and finishing at 850°C with equal deformation of 25% in each pass to convert the bar into plates. These were immediately cooled in one of the cooling media: air, polymer–water solution (1 : 1·5) and oil. Yield strength in excess of 1750 MPa was obtained in oil cooled specimens of the alloy with titanium addition and that where Cr and V were increased. The niobium added specimen gave strengths, similar to that obtained for the base alloy, in spite of the fact that the as cast alloy had shown very high strengths, presumably because of the high soaking temperatures and grain growth. Air cooling gave the lowest strengths and oil cooling the highest. 相似文献
7.
《塑料、橡胶和复合材料》2013,42(2):83-90
AbstractThe purpose of the present research was to study the effect of different belt angles on the steady state rolling behaviour of a steel belted radial tyre with slip angle. To achieve this goal, a finite element model has been developed using ABAQUS computer software. The simulation started with an axisymmetric model to analyse the tyre under inflation pressure. Then a full 3D model was generated to model the tyre under static vertical load. Having obtained the tyre configuration under contact load, a steady state rolling analysis was conducted using a mixed Lagrangian/Eulerian technique. The final stage of the modelling was the inclusion of the slip angle in the model. Each set of simulations was repeated for three belt angles and the effect of the belt angle variation on the tyre structural variables, including contact pressure and area, lateral force, interlayer shear stress and total strain energy was examined. In addition, the computed value of the number of revolutions per kilometre was compared with experimentally reported data which confirms the accuracy of the present model. 相似文献
8.
《钢铁冶炼》2013,40(4):295-299
AbstractAn overview is given of roll developments and experience in the context of hot mills and flat rolled products. After 30 years of slow change, there are now strong productivity and quality incentives driving developments in roll technology. International developments are noted, in particular the acceptance that high speed steel (HSS) rolls must be used to meet current surface finish requirements. The most significant need at present is for an improvement of late stand work rolls. 相似文献
9.
《钢铁冶炼》2013,40(5):444-448
AbstractA kinematic analytical approach has been developed to predict the roll force, rolling torque and forward slip in thin hot strip continuous rolling under various rolling conditions. The approach is based on formulating a velocity field in the roll bite zone that expresses the effect of interfacial friction on the distribution of axial velocity and longitudinal stresses across the strip thickness. The results obtained from the proposed approach are in fair agreement with finite element simulation results, whereas available analytical methods, which are usually valid for billets and thick plates, have given considerable error in the results. The proposed approach is applied to study the effect of thickness reduction ratio, coefficient of friction, work roll diameter and front and back tensions on the roll force, rolling torque and forward slip in thin hot strip rolling. The main merit of the proposed analytical approach, as compared to finite element simulation, lies in the drastic reduction in the computational time required in finite element simulation, which favours its use in online control of rolling thin strips. 相似文献
10.
《Materials Science & Technology》2013,29(8):951-956
AbstractThe embrittlement of hot isostatically pressed (hipped) diffusion bonds manufactured from 17-4 PH stainless steel has been investigated by Auger electron spectroscopy (AES) of in situ fracture specimens. Depth profiling by AES has revealed copper precipitation at the interface of the diffusion bond. This precipitation, up to a few monolayers in thickness, occurs during the ramp up to temperature and pressure of the hot isostatic pressing (hipping) cycle and is not readily removed by subsequent heat treatment. This effect is explained in terms of the metallurgical characteristics of copper within the steel. Results suggest that the extent of the precipitation decreases with increasing process temperature. In the case of PH 13-8 Mo stainless steel, where the precipitation hardening phase is NiAl, the interface is weakened by sulphur segregation and the formation of oxide particles. 相似文献