Metallurgist (v.57, #7-8)

This article examines the effect of the welding of steel 15Kh5M on the formation of local thermal stresses in a weld formed between a tube and the tube array of a shell-and-tube heat exchanger. The study was performed by computer modeling of the welding operation with the use of the finite-elements method.
Keywords: welding of heat exchanger; heat-exchanger array; welds in heat engines; structural transformations during the welding of martensitic steels

A hydrodynamic approach is used to explain the migration of the fine fraction of brex to their surface during extrusion. Such migration can have a significant effect on the strengthening of the surface layers of brex.
Keywords: extrusion briquettes (brex); stiff vacuum extrusion; fine fraction; hydrodynamic model

Effect of Reinforcing the Lining in the Impact Zone of a Steel-Pouring Ladle on the Melt-Stirring Parameters* by V. P. Piptyuk; S. E. Samokhvalov; I. N. Logozinskii; A. S. Sal’nikov; V. A. Kondrashkin; S. V. Grekov (586-591).
A study is made of the effect of reinforcing the lining in the impact zone of a 60-ton-capacity steel-pouring ladle on the melt-stirring parameters during different periods of the argon blow in the treatment of steel on an ac LFU.
Keywords: steel-pouring ladle; impact zone; melt-stirring; modeling

This article examines the problem of determining water discharge in the secondary cooling zone of a continuous caster in the automated-control regime. It is proposed that the problem be solved by the Model Predictive Control (MPC) method. The method is described along with aspects of its use to solve the given problem. Results are presented from numerical experiments.
Keywords: continuous casting; secondary cooling; automated control; mathematical modeling; predictive control

Aspects of rolling on tandem four-high cold-rolling tube mills are studied. The article examines how the gear ratio of the diagonal transmission of the stand is related to the axial force on the semifinished product and loss of stability by the tube. An improved method is developed for designing the rolls so that the deformation process is divided between a pair of breakdown rolls and a pair of sizing rolls. The study is performed using an expert automated system developed to design technologies for the cold periodic rolling of tubes. The laws that govern the accumulation of damage resulting from the effects of the main process parameters are described and technical recommendations are made on mastering the use of the given type of mill.
Keywords: cold-deformed tubes; cold periodic rolling of tubes; four-high stand of the mill; damage content of the metal; design of the mill rolls

Wavelet Analysis of Fluctuations in the Thickness of Cold-Rolled Strip by M. N. Skripalenko; M. M. Skripalenko; D. A. Ashikhmin; A. A. Sidorov; Xu Yang (606-611).
Results are presented from a wavelet analysis of fluctuations in the thickness of strip that was cold-rolled during vibration of the mill’s roll system. The vibrations were caused by a problem with the reduction gear in the main line of the mill. Results obtained by using the software Deform 2D to model the process of rolling with vibration are also presented.
Keywords: wavelet analysis; Meyer wavelet; spectral density; realization of the thickness of cold-rolled strip; computer modeling; Deform 2D; rolling mill; lengthwise variation of thickness

Pipe Steel Degradation during Operation and Brittle Failure Resistance by G. A. Filippov; O. V. Livanova; O. N. Chevskaya; I. P. Shabalov (612-622).
Pipe steel features and failure mechanism under conditions of cold brittleness, stress concentration and hydrogen brittleness, and also basic factors affecting these forms of failure are considered. The effect of structural state and deformation and heat treatment regimes for contemporary pipe steels on tendency towards corrosion cracking under stress is studied.
Keywords: pipe steels; mechanical properties; structure; prolonged operation; brittle failure; stress corrosion; hydrogen brittleness

Heat-Resistant Wrought Weldable Alloy for GTE Components with Low Linear Thermal Expansion Coefficient by S. V. Ovsepyan; B. S. Lomberg; T. I. Grigor’eva; M. M. Bakradze (623-628).
Features of the effect of alloying elements on linear thermal expansion coefficient of wrought heat-resistant alloys based on the Ni–Fe system are studied. Short-term and long-term strength at 600°C is simulated and parameters are used successfully as equivalent alloy chemical composition, calculated by a system of unpolarized ionic radii equations. A new deformable weldable alloy based on Ni–Fe–Co is developed with working temperature up to 650°C, with $ upsigma_u^{20 } $ = 1400 MPa, $ upsigma_u^{600 } $ = 1200 MPa, and $ upsigma_{100}^{600 } $ = 950 MPa, with low linear thermal expansion coefficient (α = 11.8 · 10–6 K–1 in the temperature range 20–600°C). The alloy is structurally stable, efficient in forming and welding, and with respect to set of properties it is better than standard alloys of similar designation. New alloy structure, phase composition, and properties are described.
Keywords: heat-resistant nickel alloy; structure; chemical composition; alloying; physicochemical modelling; strengthening phase; linear thermal expansion coefficient; strength; heat resistance

Residual Compressive Stresses and Defects of Layers Hardened by Chemical Heat Treatment by I. P. Banas; L. V. Morozova; E. N. Korobova; O. V. Sedov (629-632).
Reasons for the occurrence of defects in hardened layers created by chemical heat treatment, and their effect on component operating efficiency under bending cyclic loading conditions are analyzed fundamentally. Specific examples are provided for the effect of residual stresses on actual component quality.
Keywords: hardened layer; compressive stresses; tensile stresses; residual stresses; chemical heat treatment; carburization; nitriding; boriding

The Removal of Titanium from Metallurgical Silicon by HF–HCL Leaching by Keqiang Xie; Yi Mai; Wenhui Ma; Kuixian Wei; Jihong Zhou; Long Zhang (633-638).
The removal of titanium from metallurgical grade silicon (MG-Si) by HF–HCl leaching was investigated as a function of leaching time, temperature, particle size, and acid concentration. It was found that the extraction of titanium from MG-Si increased with a decrease in particle size and increase in hydrofluoric acid concentration. Titanium removal was improved very little by increasing temperature and hydrochloric acid concentration. The removal of titanium by HF–HCl took place rapidly. It was possible to remove 97% of the Ti after 0.5 h of leaching. A maximum of 99% of the Ti was removed by leaching MG-Si with 3% hydrofluoric acid and 2% hydrochloric acid at room temperature for 5 h. The main titanium-bearing Intermetallic compound in MG-Si is FeTiSi2, which cannot be attacked by hydrochloric acid but can be activated by it. Titanium is more easily removed from FeTiSi2 by hydrofluoric acid if this phase is first activated by hydrochloric acid.
Keywords: metallurgical grade silicon; removal of titanium; acid leaching

Structure Formation of Copper with Reverse Extrusion by N. A. Shestakov; V. N. Subich; A. V. Shukshin (639-646).
Data are provided for a new process achieving a greater degree of plastic deformation by reverse extrusion in bulky billets with the aim of forming a fine-grained structure. An algorithm is developed for loading stages of billets providing uniform accumulation of the degree of deformation throughout its volume. Data are provided for metal kinematic flow obtained by simulating reverse extrusion in Deform. New technology is proven by experiment using copper M1. Microstructure is studied after achieving a degree of deformation of 5.5–6. The possibility of obtaining a bulky billet with a grain size of 5–8 μm is demonstrated.
Keywords: metal forming; multistage deformation; fine-grained structure

Leaching of Refractory Gold Ores by Microwave Irradiation: Comparison with Conventional Leaching by G. Chen; J. Chen; Z. Y. Zhang; S. H. Guo; Z. B. Zhang; J. H. Peng; C. Srinivasakannan; X. Q. Li; Y. K. Zhuang; Z. M. Xu (647-653).
The present paper attempts to assess the effects of microwave irradiation on the leachability of refractory gold ores. Characteristics of the crystal structure and microstructure of the ores were determined by x-ray structural analysis (XRD) and scanning electron microscopy (SEM) before and after microwave irradiation. Compared to conventional processes, microwave leaching processes are highly energy-efficient, take less time, and do not harm the environment. The experimental results show that the amount of gold extracted increases with microwave leaching temperature. The results demonstrate that microwave irradiation techniques can be applied effectively and efficiently to the leaching of refractory gold ores.
Keywords: refractory gold ores; leaching; microwave irradiation

Features of Gold Cyanide Leaching in a Grinding Cycle by V. V. Elshin; A. A Kolodin; A. E. Ovsyukov; A. S. Mal’chikhin (654-658).
Features of gold cyanide leaching with combined gold-containing ore grinding are provided. Advantages of vibration cyaniding compared with agitation are demonstrated, in particular with respect to dissolution rate. The effect of various reagents on mineral surface tension coefficient facilitating an increase in the degree of grinding capacity is analyzed. The effect of oxygen content and ore impurity components on gold extraction is considered. A considerable role of dissolved oxygen during cyaniding is concluded, and monitoring its content makes it possible to avoid formation of passivating films at a metal surface.
Keywords: gold; grinding; gold-containing ore; dissolution; cyaniding; dissolved oxygen monitoring; passivating films; cyanide supply control system

The Ridder Zinc Plant is a large nonferrous metallurgy complex in the Republic of Kazakhstan. The process gases from the different conversions at the factory undergo fine-cleaning in bag filters and electrostatic precipitators. Recommendations are given on improving the performance of the dust-removal, ventilation, and aspiration systems of the factory's shops and several alternatives are proposed for modernizing the designs of the bag filters and precipitators. Implementation of the recommendations will improve air quality at the work stations and reduce the amount of metal lost in the hazardous emissions that are released into the atmosphere. The results can be used to design ventilation and aspiration systems at other plants in the nonferrous metallurgy industry.
Keywords: process gases; gas cleaning; cyclones; bag filters; electrostatic precipitators; efficiency; regeneration

Method of Determining the Degree of Combustion of Pulverized-Coal Fuel in Blast Furnaces by V. V. Kochura; S. L. Yaroshevskii; V. I. Kupenko; I. V. Mishin (671-681).
It is proposed that the completeness of combustion of pulverized-coal fuel injected into the hearth of blast furnaces be determined by petrographic analysis of the content of unburned coal particles in the top dust and slag and chemical analysis of the dust and slag.
Keywords: coal; pulverized-coal fuel; top dust; sludge; slag; blast furnace

Ferrochromium Smelting Technology by D. K. Isin; S. O. Baisanov; M. Zh. Tolymbekov; A. S. Baisanov; A. D. Mekhtiev; A. Z. Isagulov; B. D. Isin (682-689).
One effective method of reducing the cost of making refined grades of ferrochromium is the use of inexpensive silicon-aluminum reducing agents obtained from wastes formed in the coal-mining industry. A silicon-aluminum alloy is used to reduce chromium ore. In the course of smelting with the complex silicon-aluminum alloy, melting of the charge materials is accompanied by the reaction of magnesia-bearing chromium spinel with the aluminum of the reducing agent. The chromium-magnesia spinel subsequently decomposes. The reaction increases the speed and completeness of the reduction of chromium from the spinel thanks to the presence of silicon in the ferrosilicon-aluminum that is used in the process.
Keywords: silicon; ferrosilicon; metallothermy; charge; reducing agent; electric smelting; concentrate; coke; silicon; quartzite; iron; ferrochromium; alloying; basicity; oxide; slag

Optimizing the Thermophysical Characteristics of Slag-Forming Mixtures for a Tundish by I. V. Lebedev; V. V. Tinyakov; A. M. Toptygin; K. N. Anisimov (690-694).
This article examines the warming of steel in a tundish during the continuous casting of grades of steel that are used in critical applications. The authors examine how the introduction of an organic addition to the powdered slag-forming mixture affects its thermal conductivity. Quantitative relations are obtained to describe the dependence of the thermal conductivity and bulk density of the mixture on its content of rice husks. A comparative analysis of the warming properties of heat-insulating mixtures used at the leading Russian combines and powdered assimilating mixtures containing rice husks shows that the latter can be used without additional insulation.
Keywords: continuous casting; tundish; slag-forming mixture; thermal conductivity; bulk density

Structural Factors Governing Main Gas Pipeline Steel Stress Corrosion Cracking Resistance by A. I. Zaitsev; I. G. Rodionova; O. N. Baklanova; K. A. Udod; T. S. Esiev; I. V. Ryakhovskikh (695-706).
Work is devoted to fractographic study of steel specimens from main pipelines previously in operation and steel of current production with the aim of studying the capacity of various structural components to accumulate hydrogen during pipeline operation.
Keywords: stress corrosion cracking; stress corrosion; pipe steel; gas pipeline; hydrogen

Development of Vibration Damping Steels for Metallurgical Equipment Components by M. U. Alimanova; E. B. Utepov; E. I. Kuldeyev; Zh. K. Orzhanova (707-712).
Results are presented for a study of vibration properties of coil spring steels. An original procedure is used for impact of lamellar specimens with a percussive hammer, where due to amplitude-dependent damping of vibrations steel is revealed with a reduced level of vibrations.
Keywords: damping properties; vibration properties; steel; martensite; microstructure

Mechanical properties are analyzed for powder steels in relation to heat treatment after dynamic hot pressing. Dependences are obtained specifying the effect of annealing temperature and tempering on powder steel’s microstructure and mechanical properties.
Keywords: dynamic hot pressing; annealing; quenching; heat treatment

Use of Accelerated Cooling During Thermomechanical Rolling for Economically Alloyed Steel of Strength Class K60 (X70) by D. V. Nizhel’skii; A. A. Naumenko; Yu. D. Morozov; I. P. Shabalov; E. V. Yakushev (718-726).
The requirement is investigated for microalloying steel of strength class K60 with vanadium using thermomechanical rolling technology followed by accelerated cooling from the point of view of changing rolled product microstructure and mechanical properties. The effect of heating on rolled product mechanical properties, performed both using post-deformation accelerated cooling, and without it, is studied.
Keywords: thermomechanical rolling; microstructure; accelerated cooling; microalloying

Stainless steel of type AISI 316LN – one of the structural materials of fast neutron reactors – must have a long service life under conditions that subject it to different types of wear (galling, adhesion, fretting, and abrasion). Cobalt-based hard facings are generally avoided due to induced radioactivity. Nickel-based hard facings are strongly preferred instead. One alternative to both types of coatings is a hard-alloy coating of CrN. This article examines wear and friction characteristics during the sliding of uncoated steel SS316LN and the same steel with a CrN coating. In addition, a specially designed pin-on-disk tribometer is used to perform tests in a vacuum at temperatures of up to 1000°C in order to study the effect of oxygen on the wear of these materials. The morphology of the wear surface and the structure of the subsurface were studied by scanning electron microscopy. The formation of an adhesion layer and the self-welding of mating parts are seen to take place in the microstructure at temperatures above 500°C. It is also found that steel SS316LN undergoes shear strain during sliding wear. The friction coefficient depends on the oxygen content, load, and temperature, while the wear rate depends on the strain-hardening of the surface of the material being tested.
Keywords: austenitic stainless steel SS316LN; CrN plasma nitriding; weight loss; friction coefficient; wear rate

The effect of crystallization conditions (during casting in a copper chill mold, cast iron mold, and with ingot preparation by high-gradient directional crystallization) of high-strength deformable wear- and corrosionresistant alloy based on nickel-copper grade VKM1 (NMKZhMts-30-4-2-1-VI) on grain size in final semifinished product is studied, i.e., extruded bar with an identical heat treatment regime. It is shown that ingot casting in a cast iron mold provides preparation of a dense original ingot with coarse eutectic fragment precipitates that do not dissolve entirely on heating for extrusion, they initiate development of a considerable amount of slip planes during extrusion, and on quenching delay grain growth. This provides formation of a more fine-grained structure compared with metal cast in a copper chill mold and that obtained by high-gradient directional crystallization.
Keywords: nickel-copper alloy; wear resistance; ultimate strength; hardness; corrosion resistance; deformation; pressing; microstructure; γ′-phase Ni3Si

Effect of Single-Crystal Billet Macro- and Microstructure on Intermetallic Alloy Static and Dynamic Strength by O. A. Bazyleva; E. G. Arginbaeva; S. A. Golynets; A. B. Echin (742-747).
Research is presented for the effect of macro- and microstructure of single-crystal billets of intermetallic alloy VKNA-25 with different crystallographic orientations <001>, <011>, and <111>, prepared by directional crystallization using a seed, on material static an dynamic strength. The effect of microstructure on short- and long-term strength at 900, 1000, 1100, 1200°C on bases of 10, 100, 500, and 1000 h, and low-cycle fatigue (LCF) resistance by a “stiff” cycle, is studied. LCF tests are performed under cyclic tension conditions with a cycle asymmetry coefficient R = 0 at 850 and 1000°C. The dependence of stress rupture strength and LCF on single-crystal billet macro- and microstructure and test temperature is established.
Keywords: Ni3Al intermetallic; VKNA-25; single-crystal billets; crystallographic orientation (CGO); macrostructure; microstructure; long-term strength; stress-rupture strength; low-cycle fatigue (LCF); LCF limit

Manufacturing Technology for Titanium Tubes from Billets Prepared by Electron-Beam Remelting by S. I. Gorgul’; M. I. Medvedev; N. A. Bespalova; O. E. Sobko-Nesteruk; N. G. Tretyak; N. V. Chaika (748-751).
Technology is developed for manufacturing hot-pressed and cold-worked seamless tubes from titanium alloy billets prepared by electron-beam remelting, which makes it possible to reduce metal consumption and energy expended by lowering the number of production operations (excluding forging, machining, piercing, or expanding with preliminary drilling and heating before the above-mentioned operations). Billet mechanical properties and structure studied for hot-pressed and cold-worked pipe specimens show that the production parameters developed make it possible to obtain hot-pressed and cold-worked seamless tubes corresponding to specifications of domestic and overseas standard documents.
Keywords: technology; titanium alloys; billet; hot extrusion; cold working; mechanical properties

Improving the Durability of the Dies and Product Quality in the Production of Nichrome Strips by A. I. Snigirev; L. M. Zheleznyak; N. A. Snigirev; O. S. Gurtovenko (752-756).
Several complicated technological problems had to be solved to develop an alternative technology for the production of nichrome strips, the new technology involving the rolling of cast ingots and drawing of the hot-rolled semifinished products. In the traditional technology, sheet is hot- and cold-rolled and then cut lengthwise to form the strips. One particularly important advance over the existing technology is the improvement made to the geometry of the drawing channel in the hard-alloy dies. This modification significantly reduces die wear, practically eliminates breakage of the strip during drawing, and substantially improves the quality of the strip’s surface.
Keywords: nichrome strips; traditional and alternative technologies; drawing; hard-alloy dies; channel geometry; tool life; reduction in breakage; improved strip quality

Eleventh Russian Petroleum and Gas Congress by L. A. Kondratov (757-764).