Development of Calibration Knives for Hot Cutting Shears

In this paper, the problem distortion the end of a cylindrical workpiece in the cutting process on hot shears before being fed to the piercing mill is considered. To solve this problem, a new calibration of knives has been developed, and a finite element model hot cutting shears has been developed using the DEFORM-3D computer simulation software package. Modeling the cutting process using the proposed calibration has been carried out. It was found that the knife calibers geometry plays an important role in the formation end part geometry of the blank. Based on the simulation results, it was concluded that proposed calibration reduces the ovality workpiece end by almost 2 times in comparison with current calibration. Recommendations have been developed for the production of changes in the existing technology for cutting pipe billets.

Increase of resistance of piercing mill mandrels at seamless pipes production of 13Cr grade martensite class stainless steel at line ТПА 159‒426 of JSC VTZ

At production of pipes of type 13Cr grade steel used at development of oil and gas deposits in areas with aggressive environment, intensive wear of instrument takes place, first of all, piercing mill mandrels. Factors, influencing the resistivity of the piercing mandrels considered, including chemical composition of the material, the mandrel is made of and its design. Based on industrial experience it was shown, that chrome content in the mandrel material practically does not affect on the increase of its resistivity, since the formed thin protective oxides having high melting temperature, are quickly failed and practically are not restored in the process of piercing. To increase the resistivity of piercing mandrels at production of casing tubes of type 13Cr grade steel, a work was accomplished to select a new material for their manufacturing. The chemical composition of steel presented, which was traditionally used for piercing mandrels manufacturing, as well as a steel grade proposed to increase their resistivity. First, molybdenum content was increased, which increases the characteristics of steel strength and ductility at high temperatures and results in grain refining. Second, tungsten content was also increased, which forms carbides in the steel resulting in an increase of its hardness and “red resistivity”, as well as in preventing grains growth during heating. Third, cobalt content was also increased, which increases heat resistivity and shock loads resistivity. The three elements increase enabled to increase the mandrels resistivity by two times. Results of mandrel test of steel 20ХН2МВ3КБ presented, the mandrel having corrugation on the working cone surface, which enabled to reach the resistivity growth to 12 passes without significant change of instrument cost. Microstructure of mandrels made of steels 20Х2Н4МФА and 20ХН2МВ3КБ shown. Application of the centering pin of special design was tested, which provided forming of a rounding edge on the front billet ends, eliminated undercut of mandrel external surface in the process of secondary billet grip and increase the service life of the piercing mill mandrels. At production of seamless pipes of martensite class type 13Cr stainless steels having L80 group of strength, an increase of piercing mandrel resistivity was reached by more than four times, which together with other technical solutions enabled to increase the hourly productivity of the hot rolling section of Volzhsky pipe plant ТПА 159-426 line by more than two times.

EZTM experience in designing and manufacturing of rolling mill main drive gearboxes

The experience of the Electrostal Heavy Machinery Plant (EZTM) in designing and production of special gearboxes and gear stands for main drive of various rolling mills is summed up. The specifics of section and ball-rolling mills, piercing and reduction mills, mills for cold rolling of tubes and mills for the production of reinforcing bars are considered. It was shown that at designing of special gearboxes for the main drives of rolling mills, the designer, taking into account the parameters of the mill, must build a cyclogram of their loading, which depends both on the range of rolled products and on the variability of loads within the rolling cycle of one billet. In the Designing Department of EZTM, the strength calculation of gears of different types is carried out in the REDUK 4.3 software package, which allows performing strength calculations of gears taking into account the expected loading cyclogram. At the same time, the program provides the initial data for calculating the shafts and bearings, i.e, the forces in engagement and the rotational speed of each of the shafts for the first stage of the cyclogram. The geometrical parameters of the gears are optimized according to the criterion of contact and flexural strength, both between the stages and within each of them.The load sequence diagram depends both on the range of rolled products, and variable loadings in a rolling cycle of a workpiece. Geometric parameters of gears are optimized by contact and bending equal strength, as between the stages as within each of them. Carburizing, hardening and grinding of teeth are provided and secured technologically. Currently, the gearboxes manufactured by the plant are successfully operated at many metallurgical enterprises, both in Russia and abroad. Among them, the gearboxes of main drive of the piercing mill of the Seversk Pipe Plant, the mills for cold rolling of tubes in the USA and China, the section mills at the Yartsevo Casting and Rolling Plant, the reduction mill at the Dnepropetrovsk Metallurgical Plant, etc.

The dynamics of the centreing mechanism of piercing mill mandrel of the pipe-rolling plant

The paper presents the results of the vibrodiagnostics of a centering machine mechanism for holding piercing mill mandrel N1 of the pipe-rolling plant (PRP) 350. In the paper, it is established that vibration acceleration of a bearing roller lever of the centering machine mechanism for holding piercing mill mandrel during milling of an Æ282х50 mm shell, steel 20 reaches 5…12 m/s2, and of the upper roller’s vibration frequency is 33.3 Hz. The paper presents the results of the thickness measuring of the Æ282х50 shell, steel 20 after using the piercing mill N1 350. The results shows the distinctive influence of the dynamics of the milling holding mechanism rod. The system is put forth for calculating the energy-power parameters during the realization of the technical process for making shells of the required specifications in a piercing mill. The paper establishes the value of the milling axial resistance to the flow of the milled metal (taking the calibration values into account). The paper presents a refined system for making a dynamic model for the piercing bill milling holding mechanism rod with the milling calibration parameters taken fully included. A differential equation for the milling rod movement is made, specifically for the dynamic model of the PRP piercing mill mechanical system. The dynamic values of the mechanical system are refined, which is used as a starting point for solving the tasks dealing with the analysis of the PRP piercing mill milling rod’s vibroactivity state. In order to decrease rod vibroactivity levels, the paper recommends choosing rational milling calibration and to set the shell milling modes using mechanical system dynamics modelling during the corresponding stages of the design of technological processes. The paper pro-poses a scheme for modernization of the PRP 350 piercing bill exit side by switching the centering machine rod system holding bridges gear to proportional hydraulics. Keywords: piercing mill, vibration diagnostics, thickness measurement, piercing, sleeve; difference in wall thickness, energy-power parameters, calibration, mandrel, vibroactivity, dynamics, mandrel retention mechanism.

Some peculiarities of the process of the pipe purse firmware on the firmware

Purpose. Conducting research aimed at choosing the rational modes of flashing the tubular billet by stabilizing the dynamic characteristics of the drive power line of heavy-duty piercing mills TPA. Methodology. The dynamics of the power line of the piercing mill of the pipe-rolling unit (TPA) are considered, taking into account the peculiarities of the behavior of the spindle hinges and the mechanism for setting the work rolls. Findings. The differential equation of motion of the line of the main drive of the piercing mill is composed and its numerical solution is given. An adapted three-mass dynamic model of the system is considered and a solution is obtained using the software Solid Works IT Simulation X. The basic conditions for the occurrence of unstable dynamic phenomena in the fieldline and the installation mechanism of the piercing mill rolls are formulated. It is shown that the unstable dynamics of the system are one of the main reasons for the discrepancy between the results of well-known theoretical, experimental studies and pipe thickness measurement at TPA 350 piercing mills. Originality. The main causes of the emergence of parametric oscillations in the drive of the working stand of the piercing mill, the installation mechanism of the work rolls in connection with the mechanism of formation of the thin-wall thickness of pipes are established. The areas of stability of the system’s functioning are determined depending on the operating modes and the angle of feed of the work rolls, taking into account the spatial position of the elements of the spindle device. The necessary and sufficient stability conditions for the joint stable functioning of the power line elements of the piercing mill are formed. Practical value. To stabilize the processes for flashing the tubular billet, a scheme has been proposed for upgrading the spindles of the main drive and the mechanism for installing the work rolls of the piercing mill No. 1 of TPA 350. The results are applicable to similar helical rolling mills. Keywords: firmware, billet, mill, pipe, uneven stroke, varying thickness, dynamics, drive, roll, oscillations, spindle, Cardan, hinge, moment of inertia, rigidity, drum, installation mechanism, stability.

Mastering of seamless pipes production from martensiticclass stainless steel of 13Cr grade type at the JSC “VTZ” TPA 159–426 pipe mill

Mastering of offshore deposits of hydrocarbons require application of new types of pipe products, capable to effectively work under conditions of constant impact of aggressive media. In this connection new tasks arose to produce seamless hot-deformed pipes made of martensitic class stainless steels with increase chrome content. Mastering of such pipes production is connected with necessity to overcome a series of technological problems. The problems are stipulated by metal structure peculiarities, appeared in low plasticity and narrow temperature range for hot deformation, increased inclination to defects formation in the rolling process, as well as more intensive wear of rolling instrument, in particular of that of piercing mill. Main stages of seamless pipes production mastering, made of type 13Cr steel grades at TPA 159–426 line with TPZ-3 continuous mill of JSC “Volzhsky Pipe Plant” presented. The complex of measures for the noted problems overcoming, including semi-product type selection, piercing mill rolling instrument calibration change, as well as deformation regimes and other measures presented. The elaborated complex of measures allowed providing of pipes manufacturing of necessary quality for PAO “Gasprom” demand as per TU 14-3Р-129–2015 specifications.

Modernization of Hot-Rolled Tubes Rolling Method

A new method of hot-rolled pipes rolling on the automatic tandem mill is suggested. It consists of two rolling stands. This method allows achieving the rough pipe preovalisation before reaching the automatic mill. The rough pipe preovalisation provides even groove filling and the decrease of pipe wall thickness variation. The rough pipe preovalisation will allow increasing the elongation ratio from 1.5 to 2.0 on the lengthwise rolling stand no. 1 and decreasing the elongation ratio on the piercing mill, therefore the chance of rolling skin formation on the external surface of the pipe is decreased. The way to reduce the probability of the formation of a guide mark defect due to the kinematic tension during rolling on a stub mandrel with rough tube preovalisation is investigated. The influence of the kinematic tension factor on the pipe forming in the groove taper at a lengthwise rolling with rough tube preovalisation is explored.