22th issue of the journal "KB"

Abstract. Currently small size rebars ranging from 8 mm to 16 mm are being produced in slit rolling using dog-bone groove and round slitting groove which requires 5 to 6 continuous rolling stands having better performance at rolling speed above 8 m/s. In oval-slit pass design number of operational stands can be reduced from 5 to 4 to produce rebars even at lower speeds 3 to 8 m/s. In this work, plain strain analysis was performed on 2-D groove models designed using AutoCAD and simulation performed using ANSYS 19.1. Results showed that, shape of grooves matters most in rolling as it controls spread, reduction, plastic strain and plastic work/volume being produced. Less strain inhomogeneity in oval-slit pass design predicted greater geometric tolerances and uniformity in temperature due to relatively even deformation. In proposed oval-slit pass design plastic strain, and plastic work/volume are much lesser than that of round slitting pass design which will result in lesser energy consumption and groove wear. Little variation in plastic strain and plastic work/volume with the change in rolling speed indicated that at elevated temperatures, strain rate has little effect in hot rolling. Feasibility of oval-slit pass design to produce rebars at rolling speed ranges from 3 to 12 m/s with lesser chances of breakage and bursting is better than round slitting pass design.
Keywords: roll pass design, rebar, slitting pass design, ANSYS.

Abstract. The article describes experience grinding balls production with a diameter of 120 mm of grade hardness 5 of 77ХГФМН steel in conditions of ball rolling mill in raillway rolling shop at JSC EVRAZ NTMK. Analytical calculation of temperature conditions, calcinability and critical diameters of ball and actual modes of heat treatment are presented. Tests of this experimental batch were carried out not only within the requirements limits of GOST 7524-2015 with measurements of hardness along circumference and cross-section of the ball. As well as with tests for impact resistance and analysis of the macro and microstructure of balls. It was found that increased grinding balls calcinability with 120 mm diameter made of 77ХГФМН steel allowed not only to increase the depth of hardened layer, but also to significantly stretch the transition zone up to the central zone with formation of bainite, which minimizes the risks associated with destroyed balls.
Keywords: grinding ball, bulk hardness, quenching, tempering, thermal stresses, alloying.

Abstract. The article proposes a method for determining the possibility of distributing long pipes on broaching equipment. The main attention is paid to the exclusion of the loss of stability of the pipe during its deformation.
Keywords: long pipe, expansion, buckling, folds.

Abstract. A method has been proposed and calculations have been made for the diameters of roll barrels of TPU 8-16" rolls with pilgrim mills of ChelPipe JSC for rolling pipes with a diameter of 273 to 630 mm, based on the rollback path of feeders 1450±25 mm. For translation of the existing park of rolls in the amount of 120 pairs, a method is proposed for increasing the diameters of roll barrels for rolling pipes with a diameter of 273, 299, 325, 351, 377, 402, 426, 450, 465, 530, 550, 610 and 630 mm, including the existing park of rolls made of carbon steel type 45L with a diameter of 980, 1025 and 1045 mm, machining of barrels and roll necks, multiple rough machining of the profile of the roll groove for surfacing on roll lathes according to a copier or program, multiple surfacing of the working profile of the rolls with wear-resistant heat-resistant wire on a surfacing installation according to a copier with an allowance for machining, multiple machining on roll lathes with subsequent grinding of roll gauges to specified dimensions, it is proposed to determine the diameters of the roll barrels according to the specified polishing coefficients and the rollback path of the feeder. The analysis of the current state of the method for the production of seamless pipes at pipe-rolling plants with pilgrim mills and the existing methods for calculating roll sizing showed that in order to expand the size range towards increasing diameters, it is necessary to further improve the sizing of rolls and the technological process of pipe production. For the first time in the world practice, in rolls with a barrel diameter of 1150 mm in a caliber of 560 mm, pig pipes 550x40x5800-6000 mm in size made of steel grade 08X18H10T-Sh were rolled for subsequent machining-boring and turning them into commercial pipes 530x16-25 mm in size according to TU 14- 3R-197-2001 for nuclear facilities.
Keywords: pilger mill, pilger mill rolls, seamless hot-rolled pipes, feeding value, polishing ratio, calibration pilger rolls, longitudinal and transverse different-thickness of pipes, the way the rollback feeding device, fusing.

Abstract. Methods for the manufacture and operation of mandrels for rolling hot-rolled pipes with diameters from 273 to 630 at TPU 8-16″ of Chelyabinsk Pipe Rolling Plant JSC are considered. Hollow and composite mandrels have been developed and partially implemented, which, during operation, showed increased durability compared to solid ones. Comparative test results of solid, hollow and composite mandrels are presented. Hollow mandrels are the most promising in order to increase resistance to hot cracks.
Keywords: solid, hollow, water-cooled and composite mandrel for pilgrim pipe rolling, fire cracks, heat treatment.