Cold-resistant Steels Research Articles

Heat treatment effects on the mechanical properties and cold resistance of medium-carbon medium-alloyed high-strength steels

The paper studies heat treatment effects on the mechanical properties and cold resistance of medium-carbon, medium-alloyed high-strength cold-resistant steels. Kind of changes in strength and plastic properties depending on the tempering temperature have been revealed. It has been established, that tempering in the temperature range 560–580°C provides an optimal combination of strength and plastic properties and makes it possible to increase the cold resistance of the steel.

Analysis of cold cracking resistance when welding high-strength cold-resistant steel

Analysis of cold cracking resistance when welding high-strength cold-resistant steel

A Study of Decomposition of Supercooled Austenite in High-Strength Medium-Carbon Complexly Alloyed Cold-Resistant Steels

A Study of Decomposition of Supercooled Austenite in High-Strength Medium-Carbon Complexly Alloyed Cold-Resistant Steels

Study of phase and structural transformations in overcooled austenite for high-strength cold resistant steel during continuous cooling

Study of phase and structural transformations in overcooled austenite for high-strength cold resistant steel during continuous cooling

Structure and mechanical properties of shipbuilding steel produced by direct laser deposition and hot rolling

The structure and properties of specimens obtained by direct laser deposition from 09CrNi2MoCu steel have been investigated. The results of anisotropy of properties and structural heterogeneity induced by high rate of obtaining cold-resistant steel specimens are presented. It is shown that the content of residual austenite and cementite in the steel structure, after direct laser deposition at the boundaries of fusion rolls is significantly higher, which contributes to anisotropy. Rolling of the deposit specimens was carried out in order to reduce the anisotropy of properties and to increase the strength and plastic properties. In the work two rolling technologies are considered: hardening from furnace heating and from rolling heating, as well as the next high tempering.

Influence of the thermal cycle on microstructure formation during direct laser deposition of bainite-martensitic steel

The article presents the formation of structure and mechanical properties of bainite-martensitic steel in the process of exposure to a laser source. By varying the inter-pass temperature, the thermal cycles take place in a different temperature range, at which the formation of martensite and metastable austenite occurs. The formation of residual metastable austenite has a significant impact on the mechanical properties and performance of the product. During continuous growth, the process of phase transitions takes place in the high-temperature region. In the high-temperature region and slow cooling, bainite ferrite forms. The ferritic structure leads to brittle fracture at negative temperatures, which is unacceptable in cold-resistant steels. When specimens are deposition with a pause, the formation of the structure occurs in the low-temperature region, forming mainly bainite-martensitic structures. The resulting properties are quite high, but anisotropy is also preserved.

Influence of magnetic-abrasive machining parameters on ceramic cutting tools for technological quality assurance of precision products from cold-resistant steels

In connection with the development of the Far North and Siberia, the issues of wear resistance of equipment and technological methods for processing precision products from cold-resistant steel are of particular relevance. At low temperatures, steel exhibits a loss of ductility and toughness and an increased tendency to brittle fracture. The achievement of the required quality of machining of precision products made of cold-resistant steels is significantly influenced by the tool and the technology of its manufacture. One of such tools involved in the processing of cold-resistant steels is ceramic plates of the VOK-60 brand. This article discusses an alternative method of finishing a tool based on cutting ceramics – magnetic abrasive processing. This is a modern solution for tool processing, which allows you to obtain high quality workpieces from cold-resistant steels with minimal defects in their surface layer. The quality of the surface layer of the product during magnetic abrasive processing is influenced by many parameters, some of which will be studied in this article: electromagnetic induction, processing time, rotational speed and feed rate. The influence of these input parameters on the surface roughness of ceramic plates will be considered taking into account the combined influence on each other. The success of application of magnetic abrasive processing can be judged by the topography of the surface of the cutting ceramic plates, made using an electron microscope, as well as the results of roughness analysis using a profilometer. The data obtained during the study demonstrated the importance of individual input factors in the processing of products. Based on the results of experimental studies, recommendations have been formulated to improve the efficiency of applying the process of magneticabrasive processing in the preparation of ceramic cutting plates.

Improvement of the out-of-furnace steel treatment technology for improving its mechanical properties

The problem of increasing the competitiveness of technology today is largely determined by the quality of manufacturing large-sized cast billets for their supporting systems. Many factors are involved in forming the service properties of a casting. Each factor is important and affects the quality of the resulting casting. The presence of "cold" slag does not allow refining processes to be fully realized during the induction melting of steel. Therefore, attempts to achieve the same results for induction melting steel without additional furnace treatment as for electric arc melting steel do not always lead to success. In recent years, various methods of out-of-furnace steel processing have been developed, which make it possible to eliminate certain disadvantages of induction melting. One of them is the modification of steel in the bucket with rare earth metals (REM). Additional modification of steel in the ladle along with REM also allows for further improvement of steel quality. Currently, REM, with a high affinity for oxygen, sulfur, nitrogen, non-ferrous metals, and other impurities, are widely used in the steel production. Studies have been carried out to improve the technology of out-of-furnace steel processing and its mechanical properties. The effect of alkaline earth and rare earth master alloys on impact strength and the contamination index with non-metallic inclusions of cold-resistant steel is shown.

Production of Cold-Resistant Steel by Nanomodification in 3D Printing by Electric Arc Surfacing

Production of Cold-Resistant Steel by Nanomodification in 3D Printing by Electric Arc Surfacing

Dependence of the microstructure and mechanical properties of cold-resistant steel sheets with a guaranteed yield strength of 420 MPa on the thermomechanical processing

For the production of sheets with a thickness of 5 and 15 mm from cold-resistant steel with a guaranteed yield strength of 420 MPa, continuous rolling was developed and tested in laboratory conditions. The present study considers the influence of the parameters of thermal deformation treatment (temperature of the end of rolling and cooling rate) on the formation of the final microstructure. The mechanical properties of the sheets were analyzed taking into account the formed structural features. Technological recommendations for hot rolling of low-carbon low-alloy steel sheets with a guaranteed yield strength of 420 MPa are proposed.

Study of the fatigue strength of steel 09G2S obtained by 3D printing based electric arc welding in a wide range of low temperatures

In this work, we consider the issues of obtaining workpieces from cold-resistant steel 09Mn2Si by a promising method of 3D-printing by electric arc surfacing (electric arc additive growing). The task of assessing the mechanical properties of the obtained material and understanding the process of its destruction is urgent. The assessment of the fatigue strength of the obtained material after deposition and after subsequent heat treatment (HT) (normalization) in a wide range of low temperatures is carried out. A fractographic analysis of fatigue fractures of 9Mn2Si steel using scanning electron microscopy was also carried out. Ultimately, this makes it possible to assess the reliability of parts manufactured by 3D-printing arc welding. In the course of the work, the mechanical properties were obtained and the analysis of the curves of low-cycle fatigue of the samples after 3D-printing and after further HT in the temperature range of -60 ... 20 °C was carried out. Metallographic studies have been carried out and structural changes have been established in the process of fatigue loading at different operating time of the sample. A relationship was established between the value of the maximum cycle stress and the operating time corresponding to the onset of the onset of the main crack and the moment of fracture of the sample for steel 9Mn2Si steel. The dependence of the average growth rate of the main crack on the applied stress during fatigue tests is obtained.

Simulation of Rolling and Analysis of Structure and Properties of F420W Cold-Resistant Steel for Manufacture of Wind Turbine Towers

Two schemes of thermomechanical processing of F420W cold-resistant steel to produce sheets with thickness of 5 and 15 mm for manufacture of wind turbine towers, were developed and tested in laboratory conditions. The first scheme simulated hot rolling on a continuous mill, including reductions with minimal inter-deformation pauses and subsequent slow cooling. The second one corresponded to hot rolling on a reverse mill with accelerated cooling. Mechanical properties were analyzed taking into account the related structural features. Technological recommendations for hot rolling of a thin sheet made of high-strength cold-resistant steel were proposed.

Submerged arc welding process peculiarities in application for Arctic structures

<abstract> <p>The paper focuses on the submerged arc welding (SAW) process in application to structures for Arctic conditions. One of the technical challenges for modern Arctic structures is to produce high-quality welds since a weld is usually the weakest part of any structure. Welding is especially difficult for the high strength steels (HSS), which are used in structures for weight-reduction purposes. The objective of the study is to explore the usability, development possibilities and parameters of SAW process for welding of thick cold-resistant HSS plates. Meeting this objective required in-depth understanding of the welding and material science background, which includes the quality requirements of weld joints intended for Arctic service as described in various standards, properties of cold-resistant HSS and description of testing methods used to validate welding joints for low temperature conditions. The study describes experimental findings that improve understanding of SAW process of thick quenched and tempered (QT) and thermo-mechanically processed (TMCP) HSS plates. Experiments were conducted to develop SAW procedures to weld several thick (exceeding 25 mm) high strengths (580–650 MPa tensile strength) cold-resistant (intended operational temperature at least −40 ℃) steel grades. The welds were evaluated by a wide range of industrial tests: analyses of chemical, microstructural and mechanical properties; hardness tests; and cold resistance evaluation tests: the Charpy V-notch impact test and the Crack tip opening displacement (CTOD) test. Acceptable welding parameters and recommendations were developed, and the results of the experiments show that high quality welds can be obtained using heat input up to 3.5 kJ/mm.</p> </abstract>

Study of structure of high-strength cold-resistant steel after quenching and tempering

The conditions of heat treatment, providing achievement of high strength characteristics (σ0,2 ≥ 600 N/mm2) in combination with low-temperature impact strength (KCV−60 ≥ 50 J/cm2) and plasticity (δ5 ≥ 17 %), were determined for the new weldable sparingly alloyed steel 20G2SMRA. Steel structure was formed after hot rolling, quenching from the temperature 860 °С and consequent high tempering at the temperature 600 °С (which determined the obtained complex of steel properties) and then was examined via the method of scanning electronic microscopy. The results of energy-dispersion analysis of carbide particles which were extracted during tempering of quenched steel are presented. It is shown that the required level of strength and cold resistance is provided due to forming of mainly finedispersed lath martensite (with α-phase lath width 0.2–0.7 μm) and with small part of residual austenite (about 1 %), as well as dislocation high-temperature martensite. Sub-grain α-phase structure (with size of single sub-grains 0.1–0.7 μm) and cementite-type of carbide particles are formed during tempering. The research was carried out under financial support of the RF Ministry of Education and Science within execution of the RF President’s grant (Agreement No. 075-15-2020-205/1 dated 29.03.2021 (int. No. MK-1979.2020.8/1)).Electron microscope examination of foils for clearance were conducted within the boundaries of the State assignment for the theme “Structure”, State reg. No. АААА-А18-118020190116-6.

ON THE CLASSIFICATION OF COLD RESISTANT MATERIALS

Low-temperature technologies are increasingly used in various industries. Cold-resistant materials have gained particular popularity in the field of creating low-temperature machinery. The need for a special approach when choosing cold-resistant materials used in the production of machines, equipment and structures, whose operation is carried out under extreme conditions [low temperatures, dynamic/static loads and (or) intense wear], caused the need to systematize them according to a complex of mechanical properties. Despite the fact that a wide variety of products is produced from new cold-resistant materials in Russia and abroad, neither the scientific literature nor the regulatory documentation provides a common unified classification, which covers a wide range of their categories. Research was carried out for shipbuilding cold-resistant steels, which is reflected in the Russian National Standard R 52927–2008 “Steel rolled for shipbuilding from normal, increased and high strength steel”, however, this classification is incomplete and covers strength categories from 265 to 735 MPa. This article presents comprehensive systematization of scientific data of new structural cold-resistant steels of various leading industries of strength category up to 1550 MPa with corresponding characteristics of plasticity and cold resistance. The article considers and summarizes various criteria used to classify cold-resistant materials, as well as preferred classification features, determines numerical ranges of constituent properties. The article develops a classification system of structural steels according to groups of strength, cold resistance and hardness. The use of the proposed classification of structural alloys makes it possible to select material of certain category (class) of strength depending on operational loads of structural elements, machines and equipment of leading industries in conditions of low temperatures, and also to predict their reliability life depending on interval of low-temperature operating threshold

Effect of thermal cycles on the microstructure and mechanical properties of cold-resistant steel 09CrNi2MoCu during laser deposition

The formation of microstructure features of cold-resistant bainite-martensite steel 09CrNi2MoCu has been investigated. Thermal cycles during direct laser deposition were studied. The thermal cycles at different points of the deposited samples were investigated. The thermal cycles and CCT diagrams on microstructure formation and mechanical properties have been analyzed. The numerical calculation of the three-dimensional thermal conductivity problem by the finite element method is carried out. The received data of experimentally measured thermal cycles and the calculated data have shown good coincidence of temperature values. On the basis of the obtained data the calculated dependence of inter-layer temperature at depositing the sample with and without a pause is given. The microstructure and mechanical properties of the samples in the initial state and after heat treatment have been studied and compared with traditional hot rolling. The microstructure features at different pauses between passes in different parts of the obtained samples were revealed. The effect on static tensile and impact toughness at -40°C in the bred and heat-treated state was investigated.

Разработка технологии электронно-лучевой сварки рабочих колес центробежных насосов для судов и морских сооружений, эксплуатируемых в Арктике

Object and purpose of research. Centrifugal equipment is widely used in various sectors of industry. One of the main part of centrifugal equipment is the impeller. Application of impellers in shipbuilding is a promising field, in particular for fail-free operation in harsh Arctic environment. The purpose of this study is development of manufacturing processes for impellers involving electro-beam welding (EBW) without soldering alloys and final thermal treatment. Materials and methods. The main material chosen for the impeller is the high-strength cold-resistant steel 10ХН3МД. Main results. In the process of technology development, the impeller design was chosen. Welding conditions were optimized on mock-up samples modeling the T-joint of cover plate with vane. Sample tests and investigation were done. Conclusions were made regarding the follow-on work and EBW introduction. Conclusion. EBW technology for manufacturing of impellers was developed making it possible to fabricate impellers of high-strength cold resistant materials, including difficult-to-weld materials.

Technology of production and research of quality of super-thick sheets of high-strength structural steel AB2R made of large forging ingots

The manufacturing technology was tested and the quality study of super-thick sheets made of highstrength structural cold-resistant steel AB2R made from large ingots was carried out. Ingots are poured with siphon using modern pouring and heat-insulating mixtures while protecting the metal with argon. The use of the developed technology for casting large ingots together with the use of out-of-furnace refining and metal modification with aluminum and calcium provides a high level of quality of super-thick rolled products.

Features of heat treatment of high-strength lean alloyed cold-resistant steel

Mechanical characteristics of an alloy, used for manufacturing parts of heavy-duty machines, operating under conditions of dynamic and cyclic loads, should meet increased requirements. According to the concept of lean alloying, quality of an alloy and highest possible properties of a chemical composition are determined by the modes of heat treatment. Results of a study of quenching temperature effect on microstructure and properties of a new lean alloyed steel MAGSTRONG 450L having the following chemical composition, %, mass: 0.21 С; 0.23 Si; 0.96 Mn; 0.03 Cr; 0.41 Ni; 0.023 Ti; 0.0021 B presented. Smelting of ingots of a given chemical composition was carried out in a vacuum induction furnace ZG-0.06L. Reduction of ingots was carried out on a hydraulic press П6334 and on a single-stand reversing hot rolling mill 500 duo. The samples were heated in a ПКМ 3.6.2/12,5 chamber furnace. Best mode of the hardening heat treatment of sheet rolled product of steel MAGSTRONG H450L was established, ensuring forming of a mixed structure, comprising 80% of lath martensite and about 20% of high temperature lamellar martensite. Such a structure ensures maximum values of impact toughness KCV–40 = 38 J/сm2 at high strength parameters (tensile strength σв = 1514 МPa, offset yield strength σ0,2 = 1243 МPа, hardness 460 HBW) and satisfactory indices of plasticity (percent elongation δ50 = 16 %) which correspondents to requirements ТС 14-101-1034–2015. Based on results obtained, recommendations were elaborated for heat treatment of the sheet steel MAGSTRONG H450L, thickness 8–20 mm as per OJSC “BELAZ” order. Application of the obtained results of the study will enable to create and perfect the technological modes of heat treatment of alloys with similar composition.

Research of Properties of Austenitic Steels

Active development of the territories of Siberia and the Far East requires the use of materials that are able to work under the combined influence of low temperatures and a complex state. When operating equipment parts at low temperatures, it is necessary to take into account the impact of static and dynamic loads, as well as the influence of an external aggressive environment. The paper studies corrosion-resistant cold-resistant metastable austenitic steels, which are widely used for manufacturing parts of low-temperature equipment. Tests were performed to assess the strength and ductility characteristics of smooth samples and samples with annular notches for static stretching in the temperature range from 293 to 77 K.