Metallurgist最新文献

The aim of the study is to determine factors affecting cast iron metallurgical quality in casting mass production using new modifiers. Results of studying mechanical properties, microstructure and thermal analysis are presented. Mechanical tests are performed on specimens cut from a stepped casting, and microstructural studies are conducted using a light microscope and a scanning electron microscope. Results of thermal analyses show that introduction of modifiers increases the eutectic minimum solidification temperature and therefore increases the

likelihood of forming a vermicular form of graphite within cast iron. An increase in nucleation potential may be achieved by adding modifiers obtained from silicon production waste. Modifiers obtained from silicon production waste containing silicon dioxide and carbon nanoparticles appear to be the most advantageous final modifiers in terms of obtaining the best gray cast iron microstructure parameters and ductility properties.

In this paper the influence introducing various plasticizers into an initial charge on the structure and properties of iron-based powder materials alloyed with copper is considered. It is shown that introduction of copper stearate into an initial powder mixture and warm mixing, pressing and subsequent sintering makes it possible to obtain low-porosity workpieces with relative porosity of 95%. Pores within the workpieces obtained have a small size of 10–15 microns and a rounded shape. Also, bending strength is determined for sintered samples of all the compositions of powder mixtures studied and the Rockwell hardness is determined on the C scale. Powder steels based upon mixtures have the best set of mechanical properties

• PZhRV 2.200.28 + 0.7 wt.% Br + 0.7 wt.% Cu + 1 wt. % StCu + warm mixing—hardness HRC 58. flexural strength 600 MPa

• PZhRV 2.200.28 + 1.4 wt.% Br + 1.4 wt.% Cu + 1.4 wt.% C + 1.0 wt.% StFe + warm mixing—hardness HRC 100, flexural strength 530 MPa

This paper presents a variant of compensation for the occurrence of an impact load during the operation of a rolling mill using a regulatory method based on the integration of a neural network into a control device. The neural network can effectively select the speed and preacceleration time for the main drive of the rolling stand. Due to the neural network adaptation, the system receives information updates during the process of work, predicting changes in the technological process. A block diagram of a neural network is developed. This work describes the developed block diagram of the main electric drive of the rolling mill, which includes an additional speed sensor based on an automatic adjustment system with a neural network, which is employed to improve the quality indicators of the engine preacceleration control. Experiments on the developed system showed that when using a neural network, the maximum value of the resulting torque decreased by 9.8% with decreasing speed overshoot by 14.3%. Using an automatic control system based on prediction with the use of neural networks, it was possible to decrease the kinetic moment occurring during the metal rolling process.

Microarc surface alloying of steel is performed in carbon powder under electric current flow conditions, which leads to accelerated surface material impregnation with carbon. For surface impregnation with other alloying elements, a coating containing a diffusion agent is used, which is previously applied to a strengthened component. The purpose of this work is a study the effect of microarc diffusion impregnation temperature of steel with boron combined with carbide-forming elements on coating structure, phase composition and microhardness. Cylindrical steel 20 specimens are subjected to multicomponent impregnation with B + Cr, B + Mo, B + V, B + W at 950, 1100 and 1250 °C. Duration of the impregnation process is varied from 2 to 8 min. A coating containing boric acid H₃BO₃ powder and ferroalloy powders of carbide-forming elements in a ratio of 1:1 by volume based upon an electrically conductive binder is used for alloying. It is found that after microarc multicomponent impregnation at 950 and 1100 °C a diffusion layer consists of a base in the form of a fine ferrite-carbide mixture with microhardness up to 9.4 GPa, within which there are high hardness finely dispersed inclusions of iron and carbide-forming element carbides and borides having a higher microhardness (up to 16.5 GPa) compared with single-component boriding. Then there is a carburized layer with a eutectoid structure, passing into the original ferrite-pearlite structure of steel 20. After multicomponent impregnation at 1250 °C a diffusion layer additionally contains sections of carbide forming eutectic existing within the Fe–C–B system, with an increased content of chromium and boron as a result of predominant diffusion along grain boundaries. Therefore, microarc surface impregnation of steel with boron combined with a carbide-forming elements increases the temperature of boride eutectic formation, which may lead to increased layer brittleness compared with single-component boriding. The greatest diffusion layer thickness is obtained after 6 min of the microarc multicomponent impregnation process and then it hardly increases due to carbon particle combustion and depletion of the diffusion agent source within a coating.

Digitalization of induction heating systems in the metallurgical industry is being developed from numerical simulations of electromagnetic fields to the construction and use of digital twins. The main stages in developing digital simulations, including computational experiments and digital twins of induction heating systems, are discussed. The main features in development of digital twins for induction heating systems have been identified. Efficient methods for computing electromagnetic fields in induction heating devices and principles for building multiphysical models, including the most important electrothermal models, have been developed. A complex of specialized programs for modeling not only induction heating devices but also technologies using induction heating has been developed. A close relationship between the optimal design and control of induction heaters is presented. Examples of digital twins of different complexes using induction heating are presented.

The effect of annealing temperature on the change in microstructure and properties of stainless steel rings after deformation by high-pressure torsion is studied. Analysis of specimen microstructure after deformation by high-pressure torsion at room and cryogenic temperatures shows that eight deformation cycles lead to a homogeneous nanostructure at both temperatures, but a finer-grained structure is obtained using cryogenic cooling. With deformation and cryogenic cooling a martensitic structure is obtained with a grain size of 0.2 μm, while at room temperature a microstructure of 0.5 μm consisting of a mixture of austenite and α‑martensite is obtained. Ductility properties obtained after such treatment are insufficient for further use. In order to increase the ductility properties and to check the possibility of preserving the microstructure when heated specimens after deformation specimens are annealed at 300–650 °C and exposure time of 15 min. The ultrafine grain structure formed in steel during deformation remains stable up to 600 °C.

The second part of the article (started in No. 11, 2023) presents engineering publication data on features, new production regimes, including heat treatment, and the advantages of semi-finished products of ultralight aluminum-lithium alloys and new aluminum-polymer composite materials of the SIAL class based upon them. The article also discusses prospects for development of aluminum alloys for additive technologies, which make it possible to manufacture components of complex configuration directly from 3D digital models by direct or layer-by-layer material supply (selective laser alloying). Information is provided for properties of new aluminum alloys used to prepare components by a selective laser alloying method, and special requirements for their manufacturing capacity in additive production.

The possibility of using wire arc additive manufacturing to obtain multilayer blanks from steels 30CrMgSi and 307Lsi by their simultaneous supply in different ratios is studied. The microstructure obtained in the samples following wire arc additive manufacturing is shown. In general, a defect-free structure is formed.