CHANGES IN PIPE GEOMETRY DURING SEQUENTIAL CREATION OF STRESSES ON THE INNER SURFACE UNDER EXTERNAL THERMOMECHANICAL EFFECTS

In modern high-tech industry, flexible pipe technology is widely used. Pipe benders are an integral part of pipeline systems. The most widely used are methods of pipes cold bending, which are accompanied by a number of negative phenomena – such as reduction in the crackle of the wall on outer side of the bend, ovalization of the cross section and formation of bumps. The article presents a study of influence of deformation technology of pipe billets by rolling with high tension on the structure and properties of the billet’s material. The method of pipe deformation by rolling with tension allows obtaining radial bending of the billet without its destruction and without causing obvious defects of the surface and microstructure. The tests were carried out on the samples from steel of 3sp and 12Kh18N10T grades. Research of the microstructure was performed in accordance with GOST 5639 – 82, of mechanical properties – with GOST 1397 – 84, of microhardness – with GOST 9450 – 76. The article examines the effect of changes in geometry of the pipe billet on its structure and properties. The process of pipe deformation by rolling leads to changes in the mechanical properties of the tested materials. The values of micro hardness and strength increase, while the grain points decrease. In the process of deformation, it is possible to change the microstructure of the material as a result of structural transformations (quenching). In the thermomechanical method of deformation, plastic flow of metal suggests possible change in structure of pipe walls as a result of recrystallization and heat treatment of material of the bend area. Therefore, it requires further study and more in-depth analysis of this technology.

Эволюция структуры и свойств сплава Ni-=SUB=-47-=/SUB=-Mn-=SUB=-42-=/SUB=-In-=SUB=-11-=/SUB=- после пластической деформации

Results of the study of the effect of various types of plastic deformation on microstructural features and change in physical and mechanical properties of the nonstoichiometric Heusler alloy Ni_47Mn_42In_11 are shown. It was demonstrated that the deformation by rolling and upsetting leads to an increase in the microhardness and to an embrittlement of the investigated alloy. Severe plastic deformation by torsion under high pressure of 8 GPa at room temperature was found to strongly refine initially coarse grain and to contribute to the formation of a nanocrystalline structure with grain fragments up to 10 nm. In this case, the fraction of viscous constituent on the fracture and the microhardness increased, while the magnetic susceptibility decreased.

Electroplastic effect in metals

A mechanism of electroplastic effect considered as well as possible areas of its technological application during rolling, drawing, stamping of thin sheets and other methods of metals forming.A conception justified that metal electroplastic deformation, based on electroplastic effect, can be applied at middle and final metallurgical stage. Electroplastic effect allows to decrease metal resistance to deformation by 25–30% and increase the ductility of a metal during its forming, to increase residual ductility till 30%. Due to increasing of axial texture perfection degree of wire during drawing technology with electroplastic effect application, a decrease of its electric resistance by 15% is reached. During the metal electroplastic deformation of stainless steels the austenite-martensitic phase γ→α transformation is practically completely suppressed, which makes unnecessary operations of money-and energy consuming austenizating annealing.Based on electroplastic effect about 45 mills and powerful metal-processing facilities, using metal electroplastic effect deformation created in different countries (mainly in Russia, South Korea, Italy, Great Britain and China). Different variants of effective energy-saving critical technologies are being developed by metal electroplastic effect deformation by rolling, drawing, stamping and flatting, as well as briquetting of metal wastes with current. A new equipment is created and existing equipment is modernized for application of metal еlectroplastic effect deformation technology.

Preliminary Investigation into the Suitability of 2xxx Alloys for Wire-Arc Additive Manufacturing

An investigation has been performed into the compatibility of aluminum alloys used in the aerospace industry with Wire-Arc Additive Manufacturing. Modelling and preliminary experimental trials have been performed to show that it is viable to use Al-Cu-Mg alloys, like 2024, without solidification cracking. A relatively fine and texture free grain structure was obtained in the as-deposited WAAM material and the addition of inter-pass deformation, by rolling each added layer, led to further grain size refinement. With adequate control of porosity and subsequent heat treatment, the WAAM material was found to have tensile properties comparable to that of standard wrought products.

Characteristic Structure of Cu-0.8Cr Alloy Using SPD Deformation by Rolling with Cyclic Movement of Rolls Method

The results of the microstructure and hardness investigations of the Cu-0.8Cr alloy after application of severe plastic deformation (SPD) implemented by rolling with the cyclic movement of rolls (RCMR) are presented in this paper. Performed substructure investigations showed that using the RCMR method can refine the microstructure of Cu-0.8Cr alloy to the ultrafine scale. The structure of the Cu-0.8Cr alloy was analyzed using light microscope (LM) and scanning transmission electron microscope (STEM). The quantitative studies of the substructure was performed with "MET-ILO" software, on the basis of images acquired on STEM microscope.