Steel in Translation

The operation of the cold pipe rolling mill of JSC Sinarskii Pipe Plant is considered. A solution was proposed to modernize the main drive of the mill by forming four subsystems: the main drive, which ensures the movement of the main mechanism (stand) during pipe rolling; drive of working feed of the workpiece by 15–30 mm when the stand passes the extreme positions; front chuck rotation drive; rod chuck rotation drive, which ensures the workpiece rotation by 30 degrees. A mechatronic system was developed that covers each of the subsystems and allows for overall control. A mathematical model of the control loop for technological coordinates of the drive was developed and studied. The developed mechatronic system will improve the productivity of the cold rolling mill and the reliability of its operation while reducing the influence of mechanical loads.

Improvement in pipe production on a longitudinal rolling mill is proposed. The tandem longitudinal pipe rolling mill in the pipe-mill aggregate (PMA)-140 at PJSC (public joint-stock company) Sinarsky Pipe Works is considered. Currently, pipe is produced both from rolled billet (diameter 120 mm) and from continuous-cast billet. To reduce costs, it would make sense to discontinue the use of rolled billet and to produce all of the pipe from continuous-cast billet in the existing PMA-140. In order to employ continuous-cast billet, more profound reduction in the tandem mill is necessary. At present, the reduction is 1.16–1.5 in longitudinal rolling mill 1 and 1.07–1.15 in longitudinal rolling mill 2. With greater reduction, longitudinal guide marks may appear on the pipe surface. A possible approach to decreasing the pipe wall thickening in the groove taper and hence reducing the rejection rate due to longitudinal guide marks is to employ kinematic tension in rolling an oval sleeve on a short mandrel. The influence of the kinematic tension on the pipe shaping in grooves during longitudinal rolling of an oval sleeve is investigated. This method is found to diminish the thickening of the sleeve wall in the groove taper in longitudinal rolling mill 1. That lowers the likelihood of longitudinal guide marks on the pipe’s internal surface. The possibility of increasing the reduction in rolling on an automatic tandem mill is confirmed.

In this study, we consider the mechanism and kinetics of structure formation in the hardened zone during thermal deformation treatment of reinforced steel. Depending on the cooling rate and temperature conditions of austenite decomposition, pearlite and martensitic transformations are shown to occur with the formation of a gradient-layered structure, leading to structure modification of the surface layer of steel at a constant chemical composition, structure, and properties of the central layers of the workpiece. A high cooling rate due to a large temperature gradient near the surface is the reason for the formation of a finely dispersed layered structure. A diffusion-free martensitic transformation develops in the surface zone, leading to the formation of acicular martensite. In the underlying layers, the decomposition of austenite proceeds by diffusion and is accompanied by the formation of a lamellar ferrite–carbide mixture of varying dispersion degrees. An increase in the cooling rate leads to a strong refinement of the structure (grain point according to GOST 5639–82 is 11 in the surface layer and 8 in the core) characterized by an increase in the dispersion degree of the ferrite–carbide mixture, which causes an increase in strength and reduction of the plastic characteristics of steel. It is noted that the formation of a gradient-layered structure in the surface layer of strain-hardened reinforced steel allows excluding a sharp transition from the martensite structure to troosto-martensitic and mixed pearlite structures. This increases the contact-fatigue strength of reinforced steel and its crack resistance.

The possibility of introducing coal-dust fuel at Ukrainian metallurgical plants is considered. The use of coal dust in blast furnaces at rates of 120 kg/t of hot metal immediately reduces coke consumption by 2.7 million t and natural-gas consumption by 1.2 billion m3. In addition, by compensation of the negative impact of coal dust on the technology, the time for conversion to blast-furnace smelting based on coal-dust fuel may be reduced to a year.

Kansko-Achinsk 2B and 3B coal is of interest not only as a fuel but also as a raw material for the production of metallurgical reducing agents. Theoretical and practical aspects of the manufacture of briquets based on medium-temperature coke (thermocoke) produced from Berezovsk 2B lignite and their use in ferroalloy smelting are considered. The new material is compared with metallurgical coke. Keywords: coke, coal, medium-temperature coke, reduction, silicon, chromium, shaft electrofurnaces, gas liberation, ferroalloys

The microstructure and crystalline structure of laser-surfaced 9Kh2MF and 8Kh3SMFA steel samples are studied. Samples are taken from the working rollers of the reversible rolling mill at PAO Uralmashzavod. Sealing of surface cracks in the rollers by means of a laser is regarded as an effective repair method in small-scale production. The goal of the research is to monitor the quality of laser-surfaced steel components. The inspection focuses on metallurgical defects (nonmetallic inclusions, gaps, regions with nonuniform chemical composition) in the surfacing zone and the surrounding thermal influence zone. An ultrasound method is employed. Metallographic study of the microstructure and crystalline structure of laser-surfaced steel samples is necessary in order to develop an ultrasonic monitoring method. Metallurgical defects in steel are mainly found by means of a scanning electron microscope capable of X-ray spectral microanalysis (EDS analysis) and electron back-scattering diffraction (EBSD analysis). The present work employs a Carl Zeiss Auriga Crossbeam scanning electron microscope with EDS analysis of the surface’s elemental composition and EBSD analysis of the surface’s crystalline structure. The metallographic data for the laser-surfaced steel samples from the rollers reveal metallurgical defects along the boundary of the surfacing zone. The microheterogeneities measure 10–50 and 1–3 μm for 9Kh2MF and 8Kh3SMFA steel, respectively. The elements present include Mn, Si, and O for 9Kh2MF steel and Mn, Cr, and Mo for 8Kh3SMFA steel. The surface metal is found to be less textured than the basic metal and has more uniform acoustic characteristics. That must be taken into account in ultrasound monitoring of laser-surfaced steel components. In the ultrasound monitoring of laser-surfaced working rollers, signal recording with reflectivity equivalent to a flat-bottomed hole of 1.5-mm diameter is recommended.

The influence of the rolling parameters on the structural and phase transformations and mechanical properties of steel is analyzed. At a particular combination of temperature, strain, and strain rate, fine-grain austenite structure may be obtained, with highly developed polygonal substructure. For low-carbon steel, the best combination of cooling and winding parameters after rolling is as follows: t fr = 800–850°C; t in.co = 750°C; v co = 80°C/s; t wi = 500°C.