Effect Of Reduction Ratio Research Articles

Effect of Reduction Ratio below Austenite Recrystallization Stop Temperature on Mechanical Properties of an API X70M PSL2 Line Pipe Steel

Steel grades having high toughness and high strength are required for line pipes since gas and oil should be transported through them at high pressures. Thermo-mechanically controlled rolling processes are used for increasing both toughness and strength at low temperatures since the line pipes are exposed to harsh climatic conditions at full length and rather severe service conditions. Various test methods such as Charpy, DWTT, CTOA have been used for measurement of toughness values of these steels and the results have been evaluated considering various criteria. In this study, thermo-mechanical rolling trials were performed at the temperature below the recrystallization temperature of austenite on an API X70M PSL2 grade steel, which is large scale used in the oil and natural gas line pipes, to increase the strength without sacrificing the toughness. Different reduction ratios were utilized and the effect of reduction ratios on mechanical properties and microstructures were investigated during the trials. It was observed that final grain size decreased and strength and toughness increased with increasing reduction ratio.

Strain-induced α-to-β phase transformation during hot compression in Ti−5Al−5Mo−5V−1Cr−1Fe alloy

Abstract The dynamic phase transformation of Ti−5Al−5Mo−5V−1Cr−1Fe alloy during hot compression below the β transus temperature was investigated. Strain-induced α-to-β transformation is observed in the samples compressed at 0−100 K below the β transus temperature. The deformation stored energy by compression provides a significant driving force for the α-to-β phase transformation. The re-distribution of the solute elements induced by defects during deformation promotes the occurrence of dynamic transformation. Orientation dependence for the α-to-β phase transformation promotion is observed between {100}-orientated grains and {111}-orientated grains. Incomplete recovery in {111}-orientated grains would create a large amount of diffusion channels, which is in favor of the α-to-β transformation. The effects of reduction ratio and strain rate on the dynamic phase transformation were also investigated.

Effect of Reduction Ratio and Heat Treatment on Mechanical Properties of Forgings from Steel 14Kh17N2

Results of experimental studies of the effect of reduction ratio and modes of heat treatment on the mechanical properties of two ingots of steel 14Kh17N2 in directions longitudinal and transverse with respect to the direction of the deformation are presented.

Interface characterization of Al/Cu 2-ply composites under various loading conditions

The effects of reduction ratio during roll bonding on the microstructural evolution at interface and subsequent mechanical properties of roll-bonded Al/Cu 2-ply sheets were investigated. The interface microstructures for several Al/Cu 2-ply sheets fabricated under different reduction ratios between 30% and 65% were verified by transmission electron microscopy (TEM). Taking the difference of interface microstructure into consideration, 3-point bending and peel tests were performed for obtaining flexural and bonding strengths for Al/Cu 2-ply sheets. The effect of the quantified areas of metallurgical bonding at interfaces on the bonding strength was also discussed. The results show that both the bonding and flexural strengths for Al/Cu 2-ply sheets are reduced by decreasing the reduction ratio during the roll bonding process, which is strongly correlated with the interface microstructure. This was especially verified by observing the interface delamination from the 3-point bent samples.

Effect of Processing Parameters on Edge Cracking in Cold Rolling

Experimental and numerical investigations have been carried out to study the effect of processing parameters on edge cracks in cold rolling process of silicon steels. The onset of edge cracks has been simulated by using finite element method (FEM) based on the Gurson–Tvergaard–Needleman damage model. Factorial design and Taguchi experimental design methods have been proposed to analyze the effects of reduction ratio, tension, work roll diameter, and friction coefficient on the formation of edge cracks. Parametric studies indicated that with the increasing of reduction ratio, friction coefficient, and tension, the crack length increases. A bigger work roll is beneficial to restrict the edge crack growth as well. The rank according to the impact degrees on the crack initiation from high to low is reduction ratio, tension, work roll diameter, and friction coefficient. Meanwhile, the combined effect curve of reduction ratio and tension on crack length was obtained which was validated by the experimental results as well.

Microstructure; bonding strength and thickness ratio of Al/Mg/Al alloy laminated composites prepared by hot rolling

In this study, 7075 Al/AZ31B Mg/7075 Al laminated composites were prepared by hot roll bonding method. Microstructure and bonding strength of the experimental laminated composites, and thickness ratio of the constituent layers after hot rolling were evaluated. Effects of reduction ratio and rolling temperature on the microstructure, bonding strength and thickness ratio were also studied. Dynamic recrystallization microstructures were observed in the composite. The bonding strength decreased with reduction ratio and rolling temperature due to the increase in the grain size and diffusion layer width with the reduction ratio and rolling temperature. The maximal bonding strength of the experimental laminated composite was 66 MPa. The thickness fraction of the Mg alloy plate after hot rolling decreased with the reduction ratio and rolling temperature.

고온압연공정에서 강종 및 감면율 변화에 따른 마찰계수 변화 분석

Abstract Experimental and numerical studies were performed to examine the effect of material temperature and reduction ratio on friction coefficient during hot flat rolling. We carried out a single pass pilot hot flat rolling test at the temperatures range of 900~1200℃ and measured the spread of deformed material while reduction ratio varied from 20% to 40%. Materials used in this study were a high carbon steel and two alloy steels. The dimension of specimen used in hot rolling experiment was 50mm×50mm×300mm. We performed a series of finite element simulation of the hot rolling process to compute the friction coefficient change in terms of steel grade and reduction ratio. Results showed that temperature dependency of friction coefficient is not noteworthy but the effect of reduction ratio on friction coefficient is quite large. For high carbon steel, friction coefficient at reduction ratio of 30% is lower than that at that of 20%. Meanwhile friction coefficient at reduction ratio of 40% was one and half times large compared with that at that of 20%. The effect of steel grade on friction coefficient was significant when reduction ration was large, e.g., 40%.

Effect of reduction ratio on annealing texture and r-value directionality for a cold-rolled Al–5% Mg alloy

The evolution of the macrotexture and r-value directionality of cold-rolled Al–5% Mg alloys during annealing at various temperatures was investigated to seek an optimum annealing condition to improve the formability of TRBs. The change of volume fractions for the typical texture components of Al–5% Mg alloys was calculated using a misorientation approach in 3-D Euler space. A visco-plastic self-consistent (VPSC) polycrystal model was used to predict r-value directionality of the cold-rolled and annealed Al–5% Mg alloys. The electron backscatter diffraction (EBSD) technique was used to investigate a rapid change of the initial deformation texture in the specimen deformed by a reduction of 9% during annealing. The results showed that an optimum annealing temperature for achieving the low planar anisotropy was strongly dependent on the rolling reduction ratio.

Shear deformation and grain refinement in pure Al by asymmetric rolling

Asymmetric rolling(ASR), as one of severe plastic deformation(SPD) methods, was widely used to make ultra-fined materials with enhanced performance. Internal marks were used to show the shear deformation during asymmetric rolling with pure aluminium as a model material. Effects of reduction ratio and mismatch ratio on the shear deformation were studied. With the observed shear deformation results, equivalent strain was calculated. For lager shear deformation, rolling equipment was modified to increase friction between specimen and the rollers. Consequently, extremely fine grains with size of 500 nm are obtained in pure aluminium. With improved asymmetric rolling, the ability of grain refinement of ASR is greatly improved.

Effect of reduction ratio, inclusion size and distance between inclusions on wire breaks in Cu fine wiredrawing

The presence of an inclusion in wire makes wire breaks easy to occur even with a high reduction ratio. The investigation presented here is mainly aimed at determining the reduction ratio when size of an inclusion, application of back tension and distance between inclusions are considered. In order to investigate the effect of back tension on wire breaks, the applied back tension in a slip type continuous drawing machine is calculated quantitatively using some parameters such as diameter and peripheral speed of capstan and coiling number. The effect of an inclusion size and reduction ratio on wire breaks is investigated when quantitatively calculated back tension being 28% of drawing force is applied. The size of an inclusion varies 5, 7 and 10 μm, the reduction ratio varies 10, 13 and 16%, the distance between inclusions is set to be 0.25 and 0.5 mm, respectively. Conical dies with a half angle α of 7°, which is the value generally used in commercial production. As the FEM code, the commercially available software DEFORM-2D is used. Copper is used for fine wire drawing process that initial diameter is 1 mm and final diameter is up to 50 μm. Accumulated strain and mean stress are simultaneously calculated to obtain damage value in the multistage wiredrawing. The defects of central burst type are generated at a smaller total reduction ratio with decreasing unit reduction ratio and with increasing inclusion size. Furthermore, damage value rises because the tensile stress in deformation zone increases by applied back tension. The distance between inclusions would not affect wire breaks because the distance is expanded excessively through multistage wiredrawing.

Analysis of Cold Extrusion of Non Re-entry Product Shapes

The paper presents a feature-based analysis of cold extrusion process for non re-entry shapes. Part drawing of the shape to be extruded is drawn using line, arc, circle, polyline and ellipse entities of AutoCAD R-12 and corresponding DXF file is created. Treating shape as a feature, DXF file is processed and necessary data are separated for feature recognition. An upper-bound model for design of non re-entry cold extrudable shapes is proposed. The concept is then used to compare various die profiles based on the consideration of total extrusion power. It is found that third order stream-line and cosine dies are the best among various profiles considered. Parametric study for a square section using a third order polynomial die profile is carried out to study the effects of reduction ratio, friction factor and die length. Elliptical, trocoidal, rounded square and clover sections are examined for validating the proposed methodology.

The effect of reduction ratio of hot rolling on texture and secondary recrystallization of MA 754 plate

Ni-base oxide-dispersion-strengthened (ODS) superalloys produced by a mechanical alloying process have been used for high temperature applications because of their excellent high temperature strength, which can be useful up to a relatively high fraction of their melting points [1]. The high temperature strength of ODS superalloys is attributed to the presence of finely dispersed inert oxide particles, which gives dispersion strengthening effect by acting as a barrier to dislocation motion [2]. In order to develop high temperature strength, fine grains should be transformed into elongated coarse grains, which contributes to the retardation of the creep process and thus the prolongation of rupture life. The coarse elongated grains with a high grain aspect ratio (GAR), which is defined as the ratio of grain length (L) to grain width (W ), are possible with a high temperature annealing, during which secondary recrystallization occurs [3–6]. In particular, INCONEL alloy MA 754, which has been used as a turbine vane material in advanced jet engines, obtains the desired grain structure by isothermal annealing [7]. Although the exact mechanism of secondary recrystallization behavior is not fully understood yet, the importance of GAR has received considerable attention [3, 6, 8]. The general aim of thermomechanical processing (TMP) of ODS superalloys is to achieve a coarse grain morphology by means of secondary recrystallization [8, 9]. Another purpose of TMP is to increase the availability of the necessary product forms. However, subsequent secondary recrystallization behavior strongly depends on the temperature, strain rate, and strain of the prior TMP operation and also such compositional factors as yttria content and the amount of excess oxygen [10]. Bieler et al. have reported that the temperature and strain history during hot working have a large effect on texture, even though the same final sheet thickness was reached [11]. In a recrystallization study on a similar alloy, the recrystallization texture of sheet was sensitive to the heat treatment and rolling history [12].

Effect of reduction ratio on the machinability of a medium carbon microalloyed steel

Even though the effect of reduction ratio on mechanical properties and fatigue has been studied, no work on its effect on machinability has been reported. In this work, billets of microalloyed steel were rolled to various diameter bars yielding a range of reduction ratios. Machinability was then evaluated by the turning test, the plunge test, and the drill test. Results show no deleterious effects of lower reduction ratio on machinability. In some aspects, machinability decreases with increasing reduction ratio. The cause can be traced to slightly increased as-rolled hardness of bars with higher reduction ratios.