Chromium-manganese Steels Research Articles

On the formation of oxide inclusions in the high nitrogen chromium-manganese steel produced by the Wire and Arc Additive Manufacturing

Oxide inclusions significantly impeded the mechanical properties of the Wire and Arc Additive Manufacturing (WAAM) made high nitrogen Cr–Mn austenite stainless steels (HNSs). This paper focused on the inclusions' component, crystallization characteristics and formation mechanism. Results revealed that there are two types of inclusions: the round-shape nano-size inclusion (Type-I) and the micron-size island-shape inclusion (Type-II). The Type-I inclusion usually consists of the MnO particle or the combination of the MnO, Si-oxides and precipitations (MnS or Cr2N). Most of the Type-I oxide inclusion is located in the range between 300 nm and 700 nm,the number of Type-I oxide inclusion takes the main part of 69.7%.With higher content, smaller size and more even distributions, the isolated Type-I oxide inclusions would be beneficial to the mechanical properties owing to the Orowan strengthening mechanism. The Type-II inclusion is mostly composed of the MnO matrix and the coherent chromite spinel (MnCr2O4). In general, the larger the size, the more serious the negative impact on mechanical properties. And there was a strong negative correlation between the size and quantity of type II oxide inclusions. After heat treatment, abundant phase transformations occurred in the Type-II inclusions and some harmful phases (Sigma, MnS et cl.) were often found in or around the inclusions with specific orientation relationships. During deposition, the unstable droplet transformation and the trapped residual slag were the main causes for the inclusions in the molten pool.

Effect of Pulsed Helium Ion and Helium Plasma Flows on Austenitic Chromium–Manganese Steel Preirradiated with Deuterium

Effect of Pulsed Helium Ion and Helium Plasma Flows on Austenitic Chromium–Manganese Steel Preirradiated with Deuterium

Adhesive built-up edge on tool steels due to friction and wear

When processing metals by cutting, there are a number of materials prone to growth. This phenomenon leads to a change in the geometry of the cutter, cutting forces and surface quality, final dimensions of the part. In friction nodes: shaft-sleeve, piston-sleeve, etc. this phenomenon causes jamming. In this work, experimental studies of the processes of dry friction of tool steels with coatings were carried out to evaluate the effectiveness of reducing the growth process. As a result, it was established that the nature of formation, destruction and size of growth of materials prone to growth depends on the chemical composition of the material and modes of friction. High-strength chromium-manganese steels are most prone to growth and microseizures. It is shown that the well-known recommendation of increasing speed cannot always be used to prevent build-up, but it can be achieved by using single-layer and multi-layer coatings with a defect-free structure and moderate friction modes. It was found that electrolytic single-layer nickel and chromium coatings contribute to the formation of growth on the studied materials and this phenomenon does not depend on the modes of friction, while the same chemical coatings, which have an almost defect-free structure, are almost not prone to growth formation.

Analysis of phase equilibria in liquid chromium-manganese steels in the presence of calcium. Report 1. Phase diagrams of oxide systems.

The metallurgical industry produces a wide range of chromium-manganese steels, deoxidized and modified with calcium. To determine the non-metallic inclusions (NI) that can form in the Fe–Ca–Cr–Mn–C–O system, it is necessary to study the double and triple phase diagrams included in the FeO–CaO–MnO–Cr2O3 system. Divalent chromium oxide, which is also included in the oxide melt in the Fe–Ca–Cr–Mn–C–O system, practically does not occur in the literature as a component of double or triple state diagrams; therefore, the activity of chromium(II) oxide was equated to its ion fraction and state diagrams with it were not considered in this work. The state diagrams of oxide systems FeO–CaO, FeO–MnO, FeO–Cr2O3, CaO–MnO, MnO–Cr2O3, and FeO–MnO–Cr2O3 were previously studied by the authors. In this work, the state diagrams of the CaO–Cr2O3, FeO–CaO–Cr2O3, FeO–CaO–MnO, and CaO–MnO–Cr2O3 systems are calculated and plotted. The mixing energies are selected to determine activities in solid (theory of regular ionic solutions) and liquid (theory of subregular ionic solutions) oxide solutions to calculate the coordinates of the liquidus and solidus lines of these state diagrams. The enthalpy (103.4 KJ/mol) and entropy (21.958 J/(mol•K)) of melt-ing of calcium chromite CaCr2O4 are specified. The invariant points of the state diagrams of the FeO–CaO–Cr2O3 and CaO–MnO–Cr2O3 systems have been determined. The study of double and triple phase diagrams belonging to the FeO–CaO–MnO–Cr2O3 system will make it possible to determine all possible NIs that can form in chromium-manganese steels in the presence of calcium under equilibrium conditions.

Study of the microstructure of metastable austenitic chromium manganese steel 14Kh15G9ND by optical and electron microscopy

Modern metallography being a complex of qualitative and quantitative methods is widely used to analyze the microstructure of metal alloys. We present the results of studying the microstructure of austenitic chromium-manganese steel 14Kh15G9ND by optical and electron microscopy. The method of etching and the reagent, the most suitable for this steel grade, which provide identification of the main structural and phase components (austenite, twins, slip strips) of the steel were selected using the existing techniques. The results of optical and scanning microscopy of the samples deformed with a different degree of cold plastic deformation were compared with each other. It is shown that electrochemical etching in an aqueous solution of chromium anhydride should be used for qualitative determination of the steel microstructure. Optimal parameters of the current density and voltage were also determined. The results obtained can be used for optical microscopy of chromium-manganese steels, as well as for a more complete study of the dislocation structures present in them using scanning microscopy.

Precipitation characteristics and tensile properties of high-nitrogen chromium-manganese steel fabricated by wire and arc additive manufacturing with isothermal post-heat treatment

Wire and arc additive manufacturing (WAAM) technology is a promising method for fabricating high-performance protective materials and structural parts from high-nitrogen steel (HNS). However, owing to the complicated thermal fields generated by the process, it may produce some undesirable precipitates, such as the intermetallic σ phase or chromate nitrides, especially when the fabricated part is large. This study focused on the precipitation features of WAAM-produced high-nitrogen Cr-Mn steel containing 0.7 wt% nitrogen. When the isothermal post-heat treatment was conducted at approximately 900 °C, the σ phase dominated the original inter-dendritic ferrite (Inter-F) region. And, there were some secondary austenite precipitates (γ2) along with a small amount of Cr2N. The oxide inclusions (especially the MnO particles) provided excellent nucleation sites for the σ phase in the Inter-F region or at the Inter-F and γ matrix interface due to the high interface energy and lattice matching index. Further, when aging above 1000 °C, no σ phase was found, and the decomposition of the Inter-F to γ matrix was dominated by element diffusion. With the precipitation of the σ phase, a typical brittle fracture was observed in the samples aged at low temperatures of 800 °C and 900 °C.

ВЛИЯНИЕ СТАРЕНИЯ НА ФАЗОВЫЙ СОСТАВ И МЕХАНИЧЕСКИЕ СВОЙСТВА ВАНАДИЙСОДЕРЖАЩЕЙ ВЫСОКОАЗОТИСТОЙ СТАЛИ

Complex solid solution hardening of austenitic chrome-manganese steels by nitrogen and carbon is one of the most effective ways of production of high-nitrogen austenitic steels (HNS) without using special casting methods. To enhance the solubility of interstitials in the metal liquid state and suppress undesired secondary phases of Cr2N and Cr23C6, the carbide-forming elements (for instance, vanadium) are added to the HNS composition. By now, there are no experimental works on the age-hardening of ultrahigh-interstitial vanadium steels (more than 1 % wt.). In the present work, the authors used the X-ray structure analysis method, electron microscopy, and the uniaxial static tensile tests to study the effect of temperature (600 °С and 700 °С) and duration (0.5 h, 5 h) of age-hardening on the structure and mechanical properties of ultrahigh-interstitial vanadium-containing Cr–Mn steel (Fe–22Cr–26Mn–1.3V–0.7C–1.2N, N+C=1.9 % wt.). The experiments demonstrated that due to the complex decomposition (by intermittent and continuous mechanisms) of austenite saturated by interstitials, the aging at 600 °С and 700 °С is accompanied by a solid-solution hardening of the austenitic phase by carbonitrides Cr2(N, С) and (V,Cr)(N,С). The study identified that the increased temperature and prolongation of age-hardening stimulate the movement of intermittent decomposition front from the boundaries to the center of austenitic grains. (V,Cr)(N,С) particles formed by the continuous decomposition in the austenitic grains hinder the propagation of the reaction front, meanwhile, the large spherical (V,Cr)(N,C) and Cr2(N,C) particles, not dissolved after quenching, have little effect on its movement. At the chosen age-hardening modes, the yield strength of steel increases, and the fracture elongation decreases.

Precipitation Characteristics and Tensile Properties of High-Nitrogen Chromium-Manganese Steel Fabricated by Wire and Arc Additive Manufacturing with Isothermal Post-Heat Treatment

Precipitation Characteristics and Tensile Properties of High-Nitrogen Chromium-Manganese Steel Fabricated by Wire and Arc Additive Manufacturing with Isothermal Post-Heat Treatment

Structure Formation in Vanadium-Alloyed Chromium-Manganese Steel with a High Concentration of Interstitial Atoms C + N = 1.9 wt % during Electron-Beam Additive Manufacturing

Structure Formation in Vanadium-Alloyed Chromium-Manganese Steel with a High Concentration of Interstitial Atoms C + N = 1.9 wt % during Electron-Beam Additive Manufacturing

Microstructural effect on hydrogen embrittlement of high nitrogen chromium-manganese steel

Microstructural effect on hydrogen embrittlement of high nitrogen chromium-manganese steel

Critical Redistribution of Nitrogen in the Austenitic Cr-Mn Steel under Severe Plastic Deformation.

A narrow temperature range of changes in the mechanism and kinetics of structural-phase transformations during mechanical alloying under deformation in rotating Bridgman anvils was determined by the methods of Mössbauer spectroscopy, electron microscopy, and mechanical tests in the high-nitrogen chromium-manganese steel FeMn22Cr18N0.83. The experimentally established temperature region is characterized by a change in the direction of nitrogen redistribution—from an increase in the N content in the metal matrix during cold deformation to a decrease with an increase in the temperature and degree of severe plastic deformation. The change in the direction of nitrogen redistribution is due to the acceleration of the decomposition of a nitrogen-supersaturated solid solution of austenite with the formation of secondary nanocrystalline nitrides. The presence of a transition region for the mechanism of structural-phase transitions is manifested in the abnormal behavior of the mechanical properties of steel.

Planning an Experiment for Low-Cycle Fatigue under Conditions Deep Cooling

In the elements of structures with a limited resource during operation, significant cyclic stresses can occur, reaching and exceeding the yield strength; the results of an experimental study of the effect of the magnitude of preliminary plastic deformations on the strength and durability of structural alloys under low-cycle loading can be of undoubted interest for practice. The use of experimental planning methods in the study of the influence of the maximum cycle stresses and the magnitude of the preliminary permanent deformation on the low-cycle fatigue of 03Kh13AG19 chromium-manganese steel at T = 4.2 K under pulsating tension showed that these methods can be successfully used.

Chloride stress corrosion cracking of a non-standard, ‘Borderline’ Chromium-Manganese stainless steel – Problems of counterfeits and substandard materials

Nonstandard chromium-manganese (stainless) steels are gaining popularity nowadays, but data for them are inadequate as the majority of literature is on the ‘pedigrees’ such as the standard 200 series and 300 series steels. This paper begins with a brief overview of the counterfeit problems of such steels. It then presents the slow-strain-rate test results of a chromium-manganese ‘borderline’ stainless steel in room-temperature air, 60 °C NaCl and 60 °C distilled water (the lower-bound temperature for chloride stress corrosion cracking in austenitic stainless steels). At low strain rates (10-6 s−1), grain-boundary segregation of phosphorus and sulphur (especially the latter) can cause intergranular cracking in air and in 60 °C distilled water. In 60 °C NaCl, manganese sulphides may serve as the initiation sites of transgranular cracking. Many producers of nonstandard chromium-manganese (stainless) steels lack impurity control technologies, and so users must be vigilant of this issue. The fracture mode of the ‘borderline’ stainless steel is strain-rate dependent, changing from being mainly intergranular to being transgranular and dimpled as the strain rate goes up. The reason behind this is unclear, but a plausible suggestion is given in this paper.

Structure-Phase Transformations in the Course of Solid-State Mechanical Alloying of High-Nitrogen Chromium-Manganese Steels

The solid-state mechanical alloying (MA) of high-nitrogen chromium-manganese austenite steel—MA in a planetary ball mill, —was studied by methods of Mössbauer spectroscopy and transmission electron microscopy (TEM). In the capacity of a material for the alloying we used mixtures of the binary Fe–Mn and Fe–Cr alloys with the nitrides CrN (Cr2N) and Mn2N. It is shown that ball milling of the mixtures has led to the occurrence of the α → γ transitions being accompanied by the (i) formation of the solid solutions supersaturated with nitrogen and by (ii) their decomposition with the formation of secondary nitrides. The austenite formed by the ball milling and subsequent annealing at 700–800 °C, was a submicrocrystalline one that contained secondary nano-sized crystalline CrN (Cr2N) nitrides. It has been established that using the nitride Mn2N as nitrogen-containing addition is more preferable for the formation and stabilization of austenite—in the course of the MA and subsequent annealing—because of the formation of the concentration-inhomogeneous regions of γ phase enriched with austenite-forming low-mobile manganese.

Влияние фазовых превращений в процессе электронно-лучевой 3D-печати и последующей термической обработки на закономерности пластической деформации и разрушение образцов высокоазотистой Cr-Mn-стали

We investigated the phase composition, plastic deformation and fracture micromechanisms of Fe-(25-26)Cr-(5-12)Mn-0.15C-0.55N (wt. %) high-nitrogen chromium-manganese steel. Obtained by the method of electron-beam 3D-printing (additive manufacturing) and subjected to a heat treatment (at a temperature of 1150°C following by quenching). To establish the effect of the electron-beam 3D-printing process on the phase composition, microstructure and mechanical properties of high-nitrogen steel, a comparison was made with the data for Fe-21Cr-22Mn-0.15C-0.53N austenitic steel (wt. %) obtained by traditional methods (casting and heat treatment) and used as a raw material for additive manufacturing. It was experimentally established that in the specimens obtained by additive manufacturing method, depletion of the steel composition by manganese in the electron-beam 3D-printing and post-built heat treatment contributes to the formation of a macroscopically and microscopically inhomogeneous two-phase structure. In the steel specimens, macroscopic regions of irregular shape with large ferrite grains or a two-phase austenite-ferrite structure (microscopic inhomogeneity) were observed. Despite the change in the concentration of the basic elements (chromium and manganese) in additive manufacturing, a high concentration of interstitial atoms (nitrogen and carbon) remains in steel. This contributes to the macroscopically heterogeneous distribution of interstitial atoms in the specimens - the formation of a supersaturated interstitial solid solution in the austenitic regions due to the low solubility of nitrogen and carbon in the ferrite regions. This inhomogeneous heterophase (ferrite-austenite) structure has high strength properties, good ductility and work hardening, which are close to those of the specimens of the initial high-nitrogen austenitic steel used as the raw material for additive manufacturing.

Hardenability and Wear Resistance of Carburized to Hypereutectic Concentrations Steels

In this article the experimental data of the hardness and wear resistance of chrome-manganese steels 35H3G2F and 35HGF, which are cemented in a highly active paste-like carburizer and hardened at various temperatures, are presented. Cementation and high temperature carbonitriding of these steels leads to a high content of the carbide phase in the diffuse layers and an increase of hardness and wear resistance. The effect of carbides on the hardenability of diffuse layers are investigated. The hardening temperature ranges of these steels and the effect of alloying elements on hardness are established. The mechanism of the phase formation of the highest hardness structures is described. The carbides influence on the wear mechanism of cemented in various modes steels is studied.

Magnetic Ferritometry of Thermal Inhomogeneity with Determination of Residual Life of a Steam Heater Made of Steel Grade DI59

A study of the chemical composition of scale and metal on the outer surface of the superheater tube made of austenitic chromium-manganese (Cr-Mn) steel grade DI59 after prolonged operation is presented. It is shown that a modified layer is formed on the metal consisting predominantly of a ferromagnetic phase of a-Fe (ferrite). The thickness of the layer contains information about tube operating conditions. Results are provided for application of magnetic ferritometry to determine thermal inhomogeneity and steam heater residual life.

Study of the Process of Alloying Steel By Nitrated Chromium

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Engineering Method for Analysis of the Ability to Strain-Hardening of Steels

A study of the structure and strain-hardening ability relationship was carried out in this work for wear-resistant steels of two structural classes: high-manganese austenitic steel 110G13L and metastable austenitic chromium-manganese steel 60G9KhL. It is shown that the strain-hardening ability can be estimated using a methodologically simple engineering criterion. The criterion determines the metal tendency to harden by determining the Rockwell hardness at the bottom of the indentation cup of the Brinell press indenter

Experience of Using Steel DI59 for Manufacturing Boiler Superheaters

Favourable experience is summarized for manufacturing, welding, storage, and operation of superheaters made of heat-resistant chromium-manganese steel DI59, and a mechanism is described for overall corrosion breakdown and oxidation over pipe metal grain boundaries under action of active components fuel combustion products of V2O5 and sulfur compounds.