Study of features in weld root formation under double-sided synchronized arc welding of vertical joints of steel tanks

It is shown that increase in the welding productivity of vertical joints of storage tanks for oil and oil products can be achieved due to the double-sided synchronized formation of the X-shaped groove. To minimize various disturbances, including variation of gap size and root face dimension, computer engineering analysis is performed, which showed that the formation of root pass during welding with the movement of the electrode down (vertical down) with increased dimension of the root face leads to lack of penetration, but during groove filling with the movement of the electrodes up (vertical up) deep penetration is achieved given the considerable root face dimension. It is defined that during welding of 30 mm thickness plates with root face dimension range from 6 to 8 mm, it is necessary to ensure the root gap dimension range from 1.5 to 3 mm along the entire length of the seam. In this case, the remaining unfilled cross-sectional area of the groove is small, which makes it possible to fill it in during single pass under two-arc double-sided welding. There is area of double-sided synchronized welding modes in which the occurrence probability of typical defects during the formation of the weld root is minimal.

Effect of titanium alloys elasticity modulus on warping of stamped blanks during cooling

Wide spread in the values of the elasticity modulus of the titanium VT6 alloy and its analogs Ti—6Al—4V, Ti—6Al—4V ELI at room temperature and at elevated temperatures is revealed аs result of the literature sources analysis. The data are ambiguous, the available temperature dependences of the elasticity modulus have very different values starting from the temperature T l 500 °C. Mathematical modeling of the warping process is carried out on the example of figurine-shaped stamped blank of turbine blade using various dependences of the elasticity modulus on temperature. Cases of warping during cooling of stamped blank after cooling-down in stamp with and without cumulative deformation are considered. The difference in the course of thermal deformations during the cooling of the workpiece is obtained using different temperature dependences of the elasticity modulus. The presence of preliminary deformation increases the warping of the workpieces.

Manufacture features of grinding elements for coal mills made of high-tech wear-resistant chromium-nickel cast iron

New high-tech spheroidal graphite chromium-nickel cast iron with improved as-cast properties is developed. The technological advantages of the new alloy are shown in comparison with foreign cast iron of the type Nihard-4. High-quality castings of grinding elements made of new domestic wear -resistant cast iron are made in the conditions of Russian plants using the developed technology. Medium-speed coal grinding mills equipped with these grinding elements have successfully passed the operational test at domestic and foreign thermal power plants. The technical and economic advantages of the new technology in comparison with foreign ones are shown, which made it possible to guarantee the stable production of high-quality wear-resistant massive castings of complex c onfi guration using domestic materials under the conditions of Russian plan.

Improvement of nonmonotone deformation technology in plastic metal working

The production of semi-finished products made of refractory metals is considered. The advantage of parts production using combination of two types of straining with change in the straining direction: direct extrusion and equal-channel pressing is shown. The experimental investigation data of pure and simple shear for the semi-finished products processing made of tungsten and molybdenum are presented. Requirements for the tool providing diagonal flow and angular straining are formulated based on the analysis of the stress-strain state of the processes of axial symmetric extrusion and simple shear of plastically inhomogeneous body. Effectiveness evaluation of the combination of various types of fixtures and the rational sequence for using of diagonal flow and angular pressing is given. Experimental devices for practical application of the proposed technology are developed.

Development of technology for processing of chip wastes made of Al—Mg—Sc system alloy using hot extrusion method

The problem of chip processing of aluminum alloy containing scandium is considered. The difficulty of remelting due to easy oxidation of the alloy components is noted. It is proposed to dispose of the shavings without transferring the metal to liquid state. The aim of the work is to construct technological scheme for the processing of waste chips of the Al—Mg—Sc alloy formed as result of machining cast billets by cutting. Results of experiments including cold briquetting, hot extrusion and drawing are presented. The mechanical properties of the product obtained according to several variants of the technological scheme are measured. The possibility of continuous drawing of semi-finished product is shown. The conclusion is made about the possibility of using the scheme in the production process.

Increasing in rationality of using of cold extrusion in production of parts such as steel deep glasses

The limited use of cold volume stamping for the production of parts only for narrow traditional range of such parts in mass and large-scale productions is shown. Original technological techniques that improve the quality of products and the punches fatigue resistance are developed to expand the application of this technology to new types of parts. Such techniques used at various stages of the production process by cold forging of deep steel glasses are described. The value of rational design of stamps and the example of design of well-proven production stamp are shown.

Some aspects for increasing of heat-temperature strength of casting complex alloyed nickel-based alloys due to effect of redistribution of alloying elements between γ-solid solution and hardening γ′-phase

The positive effect of alloying elements on the thermal stability of the γ-matrix and the strengthening γ'-phase of casting nickel alloys, and consequently, on the increase in their heat-temperature strength is established. The alloying elements inhibit diffusion processes, thereby increasing the creep resistance of alloys at high temperatures and loads. It is found that the most indicative parameters of the phase composition of the test alloys are the alloying elements distribution coefficients between the γ- and γ'-phases. The basic principles of balanced alloying are formulated, on which the choice of the optimal chemical composition of heat-temperature nickel alloys is carried out.

Interaction of elements in carbon-graphite—Al—Mg—Zn—Cu melt system under combined action of temperature and pressure

Redistribution of chemically active elements is established on its inner surface of pores and at the interface with the alloy when impregnating carbon-graphite framework with Al—Mg—Zn—Cu alloy at temperature of 800 °C under pressure of up to 3 MPa. In this case, change in the solubility of melt elements in aluminum is possible as result of the combined action of temperature and pressure in the impregnation process, created due to the difference in the coefficients of thermal and thermal expansion of the matrix alloy, and the material of the impregnation device during impregnation. Titanium compounds are found in the pores filled with metal that are not added to the matrix alloy, but are formed as result of the contact of the matrix alloy melt with the walls of the impregnation device.

Application of preliminary low-temperature heating for cold forming of complex parts on cold former

The results of experimental studies of flow curves of 32CrB4, 20G2R and 1.4034 (analogue of 40Kh13 steel) steels at different heating temperature of workpieces are presented. Rational intervals of preliminary lowtemperature heating of workpieces made of studied steels are obtained. It allows to decrease forces during cold forging, loads on the working tool and to increase of tool life time up to 2 times.

Development of technique for determining of stamping hammer blow efficiency

The multiple-stage process of large-sized turbine blade blanks on steam-air die-forging hammer is considered. Mathematical modelling of the stamping process of large-sized turbine blade on falling parts 25 t mass stamping hammer is carried out. Measurements of the number of hammer blows and the under-stamping of blade blanks at each stage of the technological process are performed. Method for determining of the hammer blow efficiency is developed. Diagram of the force—displacement of falling parts 25 t mass hammer is constructed. The dependence of the blow efficiency of falling parts 25 t mass hammer is obtained, with can be used in mathematical modelling of the stamping processes of large-sized forgings on this hammer.