Vol 46, No 7 (2016)

Globally, the working life of metallurgical products is being increased. To that end, a promising approach is the use of laminar composites. In particular, experience shows that the working life may be greatly increased by using bimetallic and lined pipe instead of monometallic pipe. Lined pipe is bimetallic pipe produced by the expansion of coaxial shells made from different materials. Little attention has been paid to lined pipe in the literature on the production of composite and bimetallic pipe. The shaping methods used in the manufacturing of lined pipe differ from those for other bimetallic pipe. These differences must be taken into account in the development of lining technologies. The lack of information regarding the shaping of the shells in lining complicates the machining of lined pipe. Therefore, the present research is devoted to the deformation and shaping of paired coaxial shells and the nonuniform strain distribution between the inner and outer shells in the lining process, as well as the influence of these factors on the ratio of strength properties of the materials in the lined pipe produced.

When hard water is used to cool the rollers of metallurgical machines, scale forms on the inner surface of the cooling channel. Predictions of the roller temperature usually fail to take into account that, in the initial period of roller operation, the cooling channel is scale-free and operates in conditions very different from those in the final period. With continuing growth of the scale layer, which has good mechanical properties and poor heat conduction, the working surface is heated to the temperatures at which the rollers in the machine are tempered. In the present work, the working temperature of the rollers is investigated when scale forms on the surface of the cooling channel. A method is proposed for estimating the working temperature of the rollers in those conditions. For the example of rollers in a continuous-casting machine, it is shown that, for the selected operating conditions, the maximum temperature of the roller’s external surface reaches its critical value after operation for half a year. By the proposed method, different approaches may be taken in determining the mean and maximum surface temperature of the rollers for different thermal loads, different cooling conditions, and different quality of the cooling water. The method provides the basis for determining the roller life and setting standards for the content of reagents in the cooling water.

One aspect of improving blade production is the production of blanks with a periodic profile from nickel and titanium alloys. In certain cases of vibrational deformation (in particular, in vibrational drawing), periodic change in the diameter of rod or wire over its axis is observed. This is associated with frictional oscillation and stability loss in deformation (on reaching the yield point in the rod, with the appearance of necking, or as a result of inertial forces). Formulas are obtained for use in determining the conditions of unstable deformation and stabilizing the production of periodic bars by regulating the parameters of vibrational drawing.

The formation of the excess phase in high-manganese steel is considered over a wide range of cooling rates. This phase, which consists of a phosphide eutectic and secondary carbides, may be deposited both along the grain boundaries and within the grains. At low cooling rates, the phosphide eutectic is mainly formed, with a small quantity of secondary carbides. In addition, excess phase with mixed morphology is encountered. It consists of the eutectic and secondary carbide, with a coherent boundary between them. With increase in the cooling rate, the excess phase consists primarily of secondary carbides; its size is reduced. The influence of the cooling rate on the chemical composition of the excess phase is also of interest. Increase in cooling rate is found to reduce the manganese content in the secondary carbides deposited. The ratio between iron and manganese in the phosphide eutectic does not depend on the cooling rate and is practically constant.

The formation of a surface defect (a lobed scab) in the final stage of large-diameter pipe production is analyzed. Surface microcracks are assumed to form in the rolling of thick sheet on account of problems in the two-phase region on rolling, with localization of the plastic strain, as well as the action of tensile stress in the surface layer and the attainment of limiting stress values. Physical modeling in the Gleeble system permits determination of the limiting stress (rupture strength) in rolling in the two-phase region, which depends on the temperature and is structure-sensitive. The limiting stress is determined by ferritic and bainitic transformation in the steel.

The influence of reduction on the distribution of axial, tangential, and radial residual stress over the cross section of cold-finished steel rods is experimentally studied. Computer modeling of the flexural rigidity of the rods indicates that, with 5–34% reduction, which is the range used in practice, the rigidity of the metal may be almost doubled. It is inexpedient to increase the rigidity of the rods by additional slight reduction, since that would lower the residual tensile stress.

A production technology has been developed for high-silicon (~3% Si) isotropic electrical steel with superlow magnetic losses (P_1.5/50 ≤ 2.70 W/kg for strip of rated thickness 0.50 mm). The influence of the temperature used in the normalizing annealing of vacuum-treated hot-rolled strip (<0.005% C) with complex alloying (>1% Al and >0.015% Sb) on the magnetic properties of the final isotropic electrical steel is investigated. Normalizing annealing increases the cubic orientation in the texture of the final steel, which lowers the magnetic losses.

The influence of plastic deformation and the heating rate on the solid-phase interaction of steel strip and aluminum powder is investigated. Recrystallization of the contacting materials determines the phase formation. The layer thickness of the Fe–Al intermetallides is plotted as function of the strain and heating rate. On that basis, the parameters of the transition layer may be predicted in selecting the technological conditions.