Vol 48, No 6 (2018)

In accordance with the national energy strategy, the development of coal-fired power stations in Russia, especially in Siberia and the Far East, calls for utilization of their ash and slag wastes. The total quantity of ash and slag in Russian tailings exceeds 1.5 billion t. These wastes cover an area of more than 220 km². The utilization of these wastes is no more than 10%. The most promising approaches are utilization of the wastes in construction materials or road building, or a hybrid approach in which valuable metals are extracted during the production of construction materials. Some fly ash can be used in agriculture. The physicochemical properties of ash and slag waste and correspondingly their applicability and the choice of technology will be determined by the mineral component of the coal and the methods by which the coal is burned. In order to use fly ash in construction, dry processing methods for ash and slag waste must be introduced. On the one hand, that involves greater capital expenditures on equipment and structures for storage, classification, crushing, and grinding of the ash and slag waste, as well as means of modifying their properties. On the other, increased transportation and organizational barriers must be expected. Examples of proposed processing technologies based on metal extraction and the production of construction materials are presented. To obtain iron-bearing concentrates, single-stage magnetic separation is mainly employed. However, the resulting quality of the concentrate is unsatisfactory. A better approach to the extraction of metals from ash and slag waste is flotation. At the same time, the available data indicate that the application of flotation may be limited by economic and organizational factors and associated environmental hazards. The conclusion is that the use of such technologies at thermal power stations that are already in operation is possible, with state support.

The change in structure, phase composition, and defect substructure in the head of differentially quenched rail after the passage of gross traffic amounting to 691.8 million t is investigated over the central axis, at different distances from the top surface, by means of transmission electron microscopy. The results confirm that prolonged rail operation is accompanied by two simultaneous processes that modify the structure and phase composition of the plate-pearlite colonies: cutting of the cementite plates; and solution of the cementite plates. The first process involves cutting of the carbide particles and removal of their fragments, accompanied simply by change in their linear dimensions and morphology. The second process involves the extraction of carbon atoms from the crystal lattice of cementite by dislocations. That permits phase transformation of the metal in the rail, which is associated with marked relaxation of the mean binding energy of the carbon atoms at dislocations (0.6 eV) and at iron atoms in the cementite lattice (0.4 eV). The stages in the transformation of the cementite plates are as follows: the plates are wrapped in slipping dislocations, with subsequent splitting into slightly disoriented fragments; the slipping dislocations from the ferrite lattice penetrate into the cementite lattice; and the cementite dissolves with the formation of nanoparticles. The cementite nanoparticles are present in the ferrite matrix as a result of their transfer in the course of dislocational slip. On the basis of equations from materials physics and X-ray structural data, the content of carbon atoms at structural elements of the rail steel is assessed. It is found that prolonged rail operation is accompanied by significant redistribution of the carbon atoms in the surface layer. In the initial state, most of the carbon atoms are concentrated in cementite particles. After prolonged rail operation, the carbon atoms and cementite particles are located at defects in the steel’s crystalline structure (dislocations, grain and subgrain boundaries). In the surface layer of the steel, carbon atoms are also observed in the crystal lattice based on α iron.

In the creation of ERP systems, it is important to plan the pilot testing. In pilot projects (also known as experimental projects), the main functions of the system are tested by a limited set of advanced users. In planning the pilot testing, the key is to determine its extent. With too little testing, fundamental functions of the system may not be checked, and the probability of detecting significant errors only at complete rollout will be high. With excessive testing, the work required in the pilot project will be considerably increased, and the required speed and flexibility will not be attained in testing the basic functions. The effectiveness of pilot testing will be no better than the effectiveness of full-scale introduction. A mathematical formulation of the determination of the optimal extent of pilot testing is developed on the basis of the generation of a portfolio of IT services and their scheduling in the creation of the ERP system for a large steel company. The solution of this problem takes the form of a set of services that must be verified and the relations between them, within the specified constraint on the resources devoted to testing, such that optimal results are obtained. The solution is obtained by network programming, based on a structurally similar network representation of the relevant criteria and constraints. A solution procedure is outlined, along with an example of its use. In this procedure, dichotomous programming is used to solve individual problems. The approximate solutions obtained may be improved by solving a double network-programming problem. The branch and bound method may be used to find the global optimum of the initial problem. In that approach, the boundaries are values of the target functions for the approximate solutions. Generalization of this problem is based on the preferences of IT-service users regarding the quality of verification of different relations between the services. Those preferences may be taken into account by weighting the corresponding relationships. That leaves the basic solution procedure unchanged.

Coordinated parameter selection of the batch charged at the top of the blast furnace and the blast injected in the hearth is evaluated as a means of improving furnace performance.

Research on expanding the product range and minimizing the energy costs at a linear medium-bar mill with three-high roughing stands is discussed. The possibility of controlling the mechanical properties of the product by decreasing the initial rolling temperature is considered. Despite the improvement in mechanical properties, decrease in the initial rolling temperature in the range 900–950°C is accompanied by increase in current load at the primary drive and decrease in dimensional precision of the product.

With a view to ensuring structural stability of steels and alloys, a system for harmonizing the plasticity, strength, and deformation resistance of structural steels is developed. Principles for the formation of such properties are outlined. Means of controlling the change in these properties are considered. The sensitivity of some characteristics of the metal to changes in others is discussed. The reserves of strength in various structural steels are compared in terms of their ability to resist brittle failure, on the basis of the mechanical stability K_ms and the embrittlement expressed as the deformational strength (fracture resistance) B_r. The quality of structural steels is assessed in terms of their ability to resist embrittlement. The proposed approach here is to assess the quality of structural steels in terms of their deformational strength at specified yield point σ_0.2, which reflects the resistance to embrittlement.