孤东新滩油田KD18块普通稠油油藏降黏驱可行性研究

本文主要研究孤东新滩油田KD18块普通稠油油藏降黏剂驱的可行性,通过对降黏剂的界面性能、降黏性能及抗吸附性能评价的研究,设计适用于孤东新滩油田KD18块的普通稠油降黏剂。结果发现A-01、C-03、D-04、F-03这4种降黏剂适用于孤东新滩油田现场应用。     

Effects of post-weld heat treatment on microstructure and mechanical properties of friction stir welded joints of 2219-O aluminium alloy

Abstract

Post-weld heat treatment (PWHT) of 2219-O aluminium alloy friction stir welding joints was carried out at solution temperatures of 480, 500 and 540°C for 32 min followed by aging at 130°C for 9 h. The effects of PWHT on the microstructure and mechanical properties of the joints were investigated. Experimental results show that PWHT causes coarsening of the grains in the weld, and the coarsening degree increases with increasing solution temperature. The tensile strength of the heat treated joints increases with increasing solution temperature. The maximum tensile strength can reach 260% that of the base material at the solution temperature of 540°C. PWHT has a significant effect on the fracture locations of the joints. When the solution temperature is lower than 500°C, the joints fracture in the base material; when the temperature is higher than 500°C, the joints fracture in the weld. The change of the fracture locations of joints is attributed to the presence of precipitate free zones beside the grain boundaries and coarsening equiaxed grain structures in the weld.     

Two modes of metal flow phenomenon in friction stir welding process

Abstract

It has been widely recognised that the fundamental mechanism of weld formation in friction stir welding (FSW) is too complex, a phenomenon to be understood completely. In the present study two modes of metal transfer phenomenon in FSW have been discussed with the help of three FSW techniques. In the first technique a strip is welded to the plate by the process, in the second one the brass sheet is inserted perpendicular to the welding direction and in the third one the process is performed with tools having different pin lengths. The results suggest a strategy to model the process particularly for predicting welding tool performance.     

Effect of tool rotation rate on microstructure and mechanical properties of friction stir welded copper

Abstract

Defect free copper welds were achieved by friction stir welding (FSW) carried out at a constant welding speed of 100 mm min^?1. The influence of tool rotation rate on microstructure, mechanical properties and fracture location was investigated. As the tool rotation rate increased, the grains of nugget zone grew significantly, the thermomechanically affected zone became indistinct and the grain size increased, but the effect of tool rotation rate on the grain size of heat affected zone was limited. Both ultimate tensile strength (UTS) and elongation increased first and then decreased with increasing rotation rate and the UTS achieved a highest value of 282 MPa at the rotation rate of 400 rev min^?1 together with the welding speed of 100 mm min^?1, which was on the level of the base metal. The fracture occurred at the cavity defect on the advancing side of the joint when the FSW was performed at a low tool rotation rate, while it occurred on the retreating side when the tool rotation rate was relatively high.     

Friction stir welding of dissimilar A319 and A356 aluminium cast alloys

Abstract

In the present investigation, the microstructure and mechanical characteristics of dissimilar A319 and A356 cast Al alloys plates joined by friction stir welding (FSW) were evaluated. The effect of tool rotational and welding speeds as well as the post-weld heat treatment (PWHT) on such properties was investigated. Post-weld heat treatment was carried out at a solutionising temperature of 540°C for 12 h followed by aging at 155°C for 6 h. For the as welded specimens, the welded zone (WZ) exhibited higher hardness values when compared with the A319 and A356 parent alloys. The peak hardness at the WZ was found to increase by increasing the tool rotational speed and/or reducing the welding speed. In contrast, the post-weld heat treated (PWHTed) specimens exhibited lower hardness values at the WZ than the parent alloys. For PWHTed specimens, the peak hardness at the WZ was found to decrease by increasing the tool rotational speed and/or reducing the welding speed. Tensile tests results demonstrate that, for the as welded specimens, the tensile fracture took place on A356 side where the hardness was minimal. While for PWHTed specimens, the fracture took place at the WZ. Increasing the tool rotational speed reducing both tensile and yield strengths, but increases the ductility of the joint.     

Development of Trivex friction stir welding tool Part 1 – two-dimensional flow modelling and experimental validation

Abstract

This paper describes the application of the computational fluid dynamics (CFD) code, FLUENT, to modelling the metal flow in friction stir welding (FSW). Through the use of a novel slip model, a two-dimensional pin profile was optimised to minimise the traversing force. Two versions of a tool based on the optimised profile were developed: the plain 'Trivex' and the threaded 'MX-Trivex'. These were tested against one version of the 'MX-Triflute' tool that had comparable pin and shoulder diameters. Experiments showed that the traversing force was reduced by between 18 and 25% and the down force was reduced by approximately 12% when compared with the MX-Triflute tool. The different pin designs had little effect on the heat input and the tensile strengths of the welds were comparable. The development and validation of the full three-dimensional model for both the Trivex and Triflute tools is described in Part 2.     

37—THE SURFACE TOPOGRAPHY OF CHEMICALLY TREATED WOOL FIBRES

An account is given of experiments in which wool fibres were subjected to a large variety of chemical treatments considered as being representative of those commonly used in industrial finishing. For treatments designed to produce shrink-resistance, samples of similarly treated fabrics, subsequently subjected to a felting test (based on the International Wool Secretariat Specification 7), showed the area shrinkage to be within acceptable limits.

Qualitative scanning-electron-microscope studies revealed relatively little damage to the surface topography of wool fibres when treatments were applied at the ‘normal’ level.

When some of the treated fibres were subjected to a wash test (International Organization for Standardization No. 2), partial fragmentation of the cuticle occurred after chlorination and bleaching with hydrogen peroxide. However, little damage was observed after the wash test made on fibres treated at ‘normal’ levels.     

10—THE MECHANICS OF FRICTION-TWISTING

An analysis is given from which equations can be derived that relate the variations of twist factor, tension, and yam path through a false-twist friction spindle. The solution of these (differential) equations leads to predictions about the dependence of over-all twist factor and tension ratio on, among other parameters, the ratio of yam speed to spindle speed, the angle of wrap, and the input tension. These are compared with the early experimental results of Arthur and Weller and with more recent results.

The equations also yield the variation of twist factor and tension over the spindle surface and could be used to estimate wear.

The early part of the analysis would have general application in any situation in which a yarn is moving over a surface.     

Advances in friction welding process: a review

Abstract

Friction welding is now well established as one of the most economical and highly productive methods in joining similar and dissimilar metals. It is widely used in automotive and aerospace industrial applications. Friction welding is often the only viable alternative in this field to overcome the difficulties encountered in joining the materials with widely varying physical characteristics. This process employs a machine that is designed to convert mechanical energy into heat at the joint to weld using relative movement between workpieces, without the use of electrical energy or heat from other sources. This review deals with the fundamental understanding of the process. The focus is on the mechanism of friction welding, types of relative motions of the process, influence of parameters, heat generation in the process, understanding the deformation, microstructure and the properties of similar and dissimilar welded materials.