Cold-resistant Steels Research Articles

Increasing the reliability of low-carbon cold-resistant steel elements by diffusion zinc coating methods

The paper addresses the technological options for creating zinc diffusion layers on the surface of low-carbon cold-resistant steel 09G2S to ensure protection against wear and corrosion. We also investigated the possibility of obtaining coatings with a smooth gradient of hardness across the thickness and increased adhesion during diffusion zinc coating combined with gas nitriding.

Разработка режимов термической обработки новой конструкционной экономно-легированной высокопрочной стали для Арктики и Крайнего Севера

The structure and mechanical properties of novel structural high-strength cold-resistant steel 20G2SMRA are studied after quenching and tempering at different temperatures. The heat treatment mode providing combination of guaranteed yield strength σ 0.2 ≥ 600 MPa with low-temperature impact toughness KCV - 60 ≥ 50 J/cm 2 and ductility δ 5 ≥ 17% is suggested. The results of the study are to be used in commercial production as applied to mill 5000 of the MMK Company.

The study of influence of heat treatment procedures on structure and properties of the new high-strength steel with increased cold resistance

The study of influence of different heat treatment procedures on microstructure and mechanical properties of the new high-strength weldable cold-resistant steel 20G2SMRA (20Г2СМРА) is conducted. Morphology of martensite after steel quenching, as well after quenching and consequent tempering, is examined using optical metallography and electron microscopy. Regularities of varying of microstructure parameters, hardness values (HV1) and impact strength KCV were revealed in this work at the temperature –60 °С depending on heating temperature for quenching and consequent tempering. Amount of residual austenite after quenching starting from the temperatures 850, 950 and 1000 °C was determined using X-ray structural phase analysis. The rational procedure of heat treatment was established as a result of the study; it provides combination of guaranteed yield strength σ0,2 ≥ 600 N/mm2 together with low-temperature impact strength KCV–60 ≥ 50 J/sm2 and ductility δ5 ≥ 17%. The obtained results of investigation are aimed for commercial putting into practice in the conditions of heavy plate production at 5000 rolling mill of Magnitogorsk Iron and Steel Works (MMK). The work was done under financial support of the RF Ministry of Education and Science within the framework of execution of the grant of RF President (Agreement No. 075-15-2020-205 dated 17.03.2020 (int. No. MK-1979.2020.8)).

Quantitative assessment of structural inhomogeneity in cold-resistant low-alloy steel sheets for interpretation of technological features of their manufacturing

Microstructural inhomogeneity comparative automated complex analysis of plate low-alloy cold-resistant steels for Arctic application with a thickness of 25, 50 and 70 mm, produced by thermomechanical processing technology with various temperaturedeformation parameters, has been performed. The inhomogeneity of the microstructure over the plates thickness was estimated by the volume fraction of coarse packet-block regions of lath bainite and regions of bainite that does not have a developed internal subgrain structure (conventionally called “non-granular” bainite), as well as anisotropy of the microstructure at different dimensional levels: short and long distance neighborhoods. The obtained results of microstructural heterogeneity quantitative assessment over the plates thickness were used for its detailed interpretation, taking into account the metallurgical inheritance of the slab and special features of two-stage thermomechanical processing with accelerated cooling.

Electron-Beam Welding of Large Thickness Steels of Oil Producing Platform Components

The paper treats problems of reducing the cost of welding and improving the quality and productivity of welding parts of cold-resistant steel of great thickness during the construction of oil platforms. The design of tooling structure and devices for electron-beam welding have been developed such as a welding wire feeder, a video observation system, and software for controlling the workpiece movement and the electron beam gun travel.

Choosing the Rational Heat Treatment Conditions for High-Strength Cold-Resistant Weldable Steel with Yield Strength of more than 600 N/mm2

Rational heat treatment conditions for the new weldable cold-resistant steel grade 20G2SMRA ensuring a guaranteed yield strength σ0,2 ⩾ 600 N/mm2 combined with the lowtemperature impact strength KCV-60 ⩾ 50 J/cm2 have been searched. The effect of various quenching and tempering conditions on the steel microstructure parameters, hardness, and impact strength at a temperature of -60 °C has been studied. The dependencies of the microstructure parameters, hardness (HV1), and impact strength (KCV-60) on the quenching and subsequent tempering temperature are represented. Rational heat treatment conditions have been found for a new weldable cold-resistant steel with high yield strength.

Structure and Properties of High-Strength Low-Alloy Cold-Resistant Steel after Reheat and Direct Quenching with Tempering

Structure and Properties of High-Strength Low-Alloy Cold-Resistant Steel after Reheat and Direct Quenching with Tempering

Metallurgical Effect of Rare-Earth Lanthanum Fluoride and Boride in the Composite Coating of Wires in the Arc Welding of Bainitic-Martensitic and Austenitic Steel

For arc welding of high-strength and cold-resistant steels, the author developed an advanced design of steel wire with a micro-composite coating of a nickel matrix and nanoparticles of LaF3 and LaB6, which improves the metallurgical influence of rare-earth elements (REE) and forms refractory sulphides and oxides of REE, as well as boron nitride. The addition of 0.1–0.3 wt% La in the weld pool leads to an increase in the content of the refractory compounds La2O3, LaO2, and LaS, and to the reduction in the content of the low-melting and brittle oxides and sulphides SiO2, SiO, MnO, MnS, and SiS. The use of steel wire with the composite coating of LaF3 and LaB6 allows for microstructural refinement when welding S960QL bainitic-martensitic steel and X70 API bainitic steel, and increases the impact toughness of the welds by 1.17–1.6 times.

On the disperse acicular ferrite formation in the structure of cold-resistant joints under temperatures up to –70°С in MMA welding of 10KhSND steel. Part 1

The article presents an analysis of the metallurgical techniques that provide high quality electrodes for manual arc welding of low-carbon low-alloyed cold-resistant steels. It is shown that it is possible to improve technological and operational properties of welded joints at very low climatic temperatures up to –70°C implementing micro-alloying of the weld metal with nitrogen, titanium, cerium oxide and diamond nanopowder produced by detonation synthesis. The composition introduced into the electrode coating modifier mixture is identified. The cumulative effect of its components on the weld impact strength under temperature testing within the range from –20 up to –70°C was established. The matrix of the weld metal is composed mainly of disperse acicular ferrite, hardened by nanoparticles allegedly nitrides and carbonitrides of titanium and aluminum. It is shown that the centers for the crystallization of acicular ferrite are micro-sized non-metallic inclusions formed on ultrafine titanium nitrides. It was revealed that the toughness of the weld metal at low climatic temperatures is higher than toughness of joints welded by massively imported Japanese KOBELCO electrodes LB-52U. The results of the study make it possible to increase the cold resistance of welded structures for petrochemical plants and other facilities located in the Extreme North of the Russian Federation.Part 2 of the article will be devoted to the study of the welding and technological properties of coated electrodes.

Определение индуцированной водородом поврежденности акустическим методом

The 13HFA corrosion- and cold-resistant steel is studied by an ultrasonic method after hydrogen absorption for 96, 192, and 288 hours. Within the framework of classical flaw detection, it was found that the formation of macrodefects occurs only at 288 hours of hydrogen absorption. In the study of the material by the spectral-acoustic method, it was found that, during hydrogen absorption for 96 and 192 hours, the signal spectrum changes. This indicates the formation of microdefects. It is shown that the determination of the damage by the conventional ultrasonic flaw detection method and the use of the spectral-acoustic method for the evaluation of fracture at the microlevel give more complete information on the state of the investigated alloys.

The Assessment of the Possibility of Smelting a Cast Alloy for the Manufacture of Components and Parts of Arctic Technical Equipment Using Ore from the "Verkhnyaya Amga" Ore Occurrence

The research assesses the possibilities of using local minerals to create foundry alloys that are used in conditions of low temperature. The mineral-geochemical composition of iron ore from Verkhnyaya Amga ore occurrences in the Aldan region of the Sakha Republic (Yakutia) was studied in detail. The expedience of using iron ores from this ore occurrence to develop new cold-resistant and high-strength steels was analyzed. The chemical composition and microstructure of the cast alloys were studied. The ore contains oxides of alkaline earth metals: MgO; CaO; Sr0 and BaO, the total content of which is 4.2%, that contributes to the process of deoxidation of the melt during its cooling, and the deoxidation product in the form of oxides and other chemical compounds based on Ca, Sr and Ba floats into slag. During crystallization, the melt is cleaned of detrimental impurities, non-metallic inclusions, gases, pores, etc. Alloy is smelted from enriched ore, samples for static tension and toughness are made in order to study the physicomechanical properties. Microstructure of the obtained alloy and structural steel subjected to static tension at an external load of 0.8 yield strength (σ = 0,8 σт) was investigated. Mechanical properties and dynamic characteristics were measured. Analogues for comparing the strength and plastic properties were given.

Structure and properties of high strength low alloyed cold-resistant steel after reheat and direct quenching with tempering

The paper shows comparative investigations of structure of rolled plates from low alloyed coldresistant steel 08CrNi2MoCuNb with guaranteed yield strength 750 MPa after traditional reheat quenching and quenching from rolling heat (direct quenching) with subsequent high temperature tempering. The research is carried out by means of optical metallography, SEM and TEM. The peculiarities of parameters of bainitemartensite structure, which influence the strength level in initial (quenched) state, are revealed. Also, the impact of tempering on structure and properties of rolled plates after reheat and direct quenching is shown.

A Study of the Effect of Nickel on Structural and Phase Transformations and Properties of High-Strength Medium-Carbon Complexly Alloyed Steel

The effect of nickel content in a high-strength medium-carbon complexly alloyed steel on the structural and phase transformations, location of critical points, quantitative parameters of microstructure and critical quenching rate is studied. Thermokinetic diagrams of decomposition of supercooled austenite in the steel with original composition are plotted and the characteristic types of microstructure forming under cooling at different rates are described. The effect of nickel on the combination of mechanical properties of thick rolled sheets after quenching and low-temperature tempering is determined. The results obtained may be used for development of high-strength cold-resistant steels and modes of their heat hardening.

Formation of Bead Shape, Structure and Mechanical Properties of Cold-Resistant High-Strength Steel Produced by Direct Laser Deposition Method

The technology of direct laser deposition is the most promising for use in various industries. One of the most interesting industries for using this technology is shipbuilding. Due to its unique properties, cold-resistant steels are widely used in shipbuilding for brackets of mushroom propellers, stems, and also structures for work on the Arctic shelf. In this paper, the studies of the influence of technological parameters on the formation of the geometry and properties of products are represented. The technological parameters of the process of direct laser deposition parts from steel 0909CrNi2MoCu are determined.

Direct laser deposition of cold-resistant steels for Arctic shelf development

In the shipbuilding industry, due to the need to manufacture large-sized and complex products, the use of additive technology by direct laser deposition is promising. The object of the study was choosing of technological processes of direct laser deposition of products made from steel powder 09CrNi2MoCu. To achieve this goal, the complex of theoretical and experimental studies were carried out, including metallographic studies and mechanical tests of the deposition samples. Laboratory samples were manufactured both with local protection and in a protective medium with different residual oxygen contents. Based on the selected process parameters, a product is manufactured by direct laser deposition. During the research and analysis of the results, the regularity of the influence of technological parameters on the deposition products was established. It is established that the influence of the protective environment positively affects the structure and properties of the obtained products. The results of mechanical tests of samples obtained by direct laser deposition have a value higher than rolled products.

The influence of a protective environment during direct laser deposition on the formation of structure and properties of steel F690W (09CrNi2MoCu)

The article presents the study of the direct laser deposition (DLD) process of cold-resistant steel 09CrNi2MoCu (F690W). As a result, many bainite transformation products are produced. The formation of a bainitic structure in the process of deposition is still little studied; in the process of the growth of the deposited wall, the microstructure undergoes a phase transformation.The work details the equipment for direct laser deposition, describes the main technological parameters of the regime, and studies the surface of the steel powder. Mechanical tests for impact toughness were carried out at a temperature of −40 °C, with different laser emission powers. The results are given using the initial powder, as well as used powder with a different mixing ratio, and the results are analyzed. As a result of the study, it was established that the fractional composition of the F620W alloy powder has a significant effect on the mechanical characteristics of samples obtained by direct laser deposition. The effect of recycled powder on the mechanical properties of the samples obtained is given.

Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions: Part 2. Manufacturing Technology, Structure, Properties, and Serviceability of Sheet Products

Abstract—The paper presents results of the industrial implementation of hot plastic deformation and thermal treatment schemes for the production of rolled sheet products based on cold-resistant steel with yield strength not lower that 315–750 MPa for the Arctic. On the basis of the studies performed, a set of scientific and technological techniques has been developed for various technological processes (thermomechanical treatment followed by accelerated cooling, quenching from the rolling heating, and separate furnace heating with high-temperature tempering). The developed complex method provides the formation of a structure having an acceptable heterogeneity and anisotropy level corresponding to different morphological and crystallographic parameters throughout the entire thickness of rolled products up to 100 mm based on low-alloy steels with a yield strength not lower than 315–460 MPa and up to 60 mm based on economically alloyed steels with a yield strength not lower than 500–750 MPa. The structure of sheet products is presented that provides guaranteed characteristics of strength, cold resistance (impact energy KV at a testing temperature ranging from –60 to –80°C, critical ductile-to-brittle transition temperature Tkb, and nil ductility temperature NDT), and crack resistance according to a CTOD criterion in a low-temperature range to meet the requirements of the RMRS “Rules for the Classification and Construction of Ships” for steel with the Arc40 index.

Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions. Part 1: Alloying Principles and Requirements for Sheet Product Structure

Abstract—The results obtained upon choosing rational alloying and microalloying for cold-resistant steels with a guaranteed yield strength of 315–750 MPa on the basis of established interrelations between phase transformations, structure, mechanical properties, serviceability parameters, and the content of main alloying elements are presented. Quantitative requirements for various structural parameters and their maximum permissible difference throughout sheet product thickness up to 100 mm have been developed, depending on the strength category and manufacturing technology (thermomechanical treatment with accelerated cooling, quenching from separate furnace heating or rolling heating with high temperature tempering) to provide guaranteed characteristics of strength, cold resistance (impact energy KV at a testing temperature from –60 to –80°С, critical ductile-to-brittle transition temperature Тkb, and nil ductility temperature NDT), and crack resistance according to the criterion of critical crack tip opening displacement (CTOD).

Relation Between the Microstructure of Cold Resistant Steel 20GL and Some Parameters of the Melting Process

The microstructure, impact toughness and melting parameters of cold-resistant steel 20GL are studied. The impact toughness of the steel at negative temperature (KCV-60) is shown to be affected the most by the size of the primary (natural) grains of the metal. The size of the natural grains is shown to be dependent on the content of oxygen and (to a less degree) of silicon. Introduction of an elevated amount of slag-forming materials and aluminum into liquid metal provides the required (at most 0.005–0.008 wt.%) content of oxygen and an impact toughness (KCV-60) no less than 0.167 MJ/m2. Influence of the nonmetallic inclusions, of the size of actual grains, and of the content of pearlitic phase on KCV-60 in normalized steel has not been detected or was not obvious.

Research of Mechanical Properties of Cold Resistant Steel 09CrNi2MoCu after Direct Laser Deposition

Review focuses on describing of mechanical properties of the components manufactured via direct laser depositionfrom cold resistant steel material. The results of tensile and impact testing are presented and microstructures of the fractures are shown. The process of laser deposition of cold-resistant steels, the formation of structures, as well as the mechanical properties of these samples are poorly understood. The results of tensile and impact tests are presented, and microstructures are shown. Mechanical tests for impact strength were carried out at a temperature of -40˚С, with different laser radiation powers. The results are given using the as-received powder, as well as used powder with a different mixing ratio, and the results are analyzed. As a result of the study, it was found that the fractional composition of the 09XH2MD alloy powder affects the mechanical characteristics of samples obtained by direct laser deposition. The effect of recycled powder on the mechanical properties of the obtained samples is given, the optimal laser deposition regimes are selected