Effect of heat treatment on the mechanical properties and the structure of a high-nitrogen austenitic 02Kh20AG10N4MFB steel

The effect of heat treatment on the mechanical properties of a high-nitrogen austenitic 02Kh20AG10N4MFB steel has been studied in the temperature region 550—1200°C. The yield strength and the ultimate tensile strength are shown to change nonmonotonically as a function of the heat treatment temperature. They sharply decrease in the annealing temperature range 850—900°C, which can demonstrate a change in the character of the structure–phase state of this steel. After annealing at 850—900°C, aging occurs with the precipitation of embrittling phases; at higher annealing temperatures, these particles dissolve and austenite recrystallizes. The study of the stress–strain diagrams makes it possible to find the laws of strain hardening of the 02Kh20AG10N4MFB steel as a function of the heat treatment temperature.     

Effect of heat treatment on the structure and properties of a high-nitrogen austenitic corrosion-resistant 03Kh20AG11N7M2 steel

The structure and mechanical and corrosion properties of a high-strength austenitic 03Kh20AG11N7M2 steel after quenching and aging at 500 and 800°C are analyzed. The phase composition of the steel and the mechanism of the decomposition of austenite during heat treatment are studied by electron-probe microanalysis and transmission electron microscopy. This steel is thermally stable upon heating to 800°C for 1 h and is stable to the γ → α and γ → ɛ martensitic transformation during deformation up to tensile strains leading to fracture. The homogeneous decomposition of a supersaturated γ solid solution at 500°C leads to the formation of disperse CrN nitrides, which increase the strength of the steel and insignificantly decrease its plasticity. In this case, the stress corrosion cracking resistance slightly decreases and the passivation of the steel increases in an corrosive medium without loading.     

18-18-0.5N高氮奥氏体不锈钢冷轧变形过程中的组织演变和形变强化

利用XRD、TEM、SEM和拉伸实验等分析测试方法研究了18-18-0.5N高氮奥氏体不锈钢在冷轧变形过程中的组织演变和形变强化规律.结果发现:18-18-0.5N高氮奥氏体不锈钢在冷变形过程中并未发生形变诱导相变,微观组织和力学性能在变形量为43.8%附近出现转折.提出了屈服强度随应变变化的预测方程.     

Machinability of the high-strength corrosion-resistant high-ductility austenitic steel 06Kh22AG15N8M2F

The machinability of the high-nitrogen corrosion-resistant austenitic steel 06Kh22AG15N8M2F during turning is studied. The specific features of the structure of the surface layers in steel workpieces after turning are revealed. The cutting conditions that provide the lowest wear of VK8 alloy cutting tools upon turning are found: the cutting speed is 21–74 m/min, the feed is 0.15–0.60 mm/rev, and the cutting depth is 0.15–0.75 mm. The presence of a large amount of Cr₂N-type chromium nitrides in the structure of the steel annealed at 800°C for 2 h and a high nitrogen content in the austenite of the steel quenched from 1100°C increase the wear of the cutting tools. As to turning of the forged steel, the wear resistance of the cutting tools upon turning of the 06Kh22AG15N8M2F steel is higher than that upon turning of 08Kh18N10T steel, in which deformation martensite forms (in surface layers) during turning.     

Effect of heat treatment on the structure of high-nitrogen austenitic corrosion-resistant 04Kh22AG17N8M2F and 07Kh20AG9N8MF steels

The structures of high-strength austenitic 04Kh22AG17N8M2F and 07Kh20AG9N8MF steels are studied after various heat-treatment conditions, and the relation between these structures and the mechanical and chemical properties of these steels is analyzed. The phase compositions of the steels, the morphology of phases, the fine structure of austenite, and the mechanism of its decomposition upon heating are investigated by X-ray diffraction and transmission electron microscopy. The homogeneous decomposition of the supersaturated γ solid solution in the 04Kh22AG17N8M2F steel at 500 °C is shown to be accompanied by the formation of the CrN nitride, which is isomorphic to the matrix, and to increase the strength and elastic stresses in the austenite, decreasing the stress corrosion cracking (SCC) resistance of the steel. Heating at 800 °C facilitates stress relaxation and increases the SCC resistance of the steel.     

Weldability of corrosion-resistant high-nitrogen austenitic Kh22AG16N8M-type steels

The influence of thermal treatment on the structures and mechanical properties of welds of corrosion-resistant high-nitrogen austenitic 05Kh22AG16N8M-type steels is studied. In these steels, austenite is found to be highly resistant to discontinuous precipitation and the formation of σ phase and δ ferrite upon cooling regardless of the temperature of heating for quenching (from 900 to 1250°C) and the cooling conditions (water, air, furnace). Welding of these steels can produce high-strength welds with an enhanced impact toughness.     

Correlation between the granular structure and the mechanical properties of high-nitrogen austenitic 02Kh20AG10N4MFB steel after annealing

The effect of the annealing temperature and time on the formation of a granular structure in high-nitrogen austenitic 02Kh20AG10N4MFB steel has been studied. The hardness and the strength properties of the steel are shown to be related to the mean grain size by an inverse dependence, according to the Hall–Petch relation, and the impact toughness is proportional to the mean grain size. At annealing temperatures to 1100°C, structure formation is determined by the precipitation of secondary phases; at higher annealing temperatures, it is determined by the recrystallization of austenite grains.     

Cyclic strength of corrosion-resistant high-nitrogen austenitic 05Kh22AG15N8MF steel during repeated tension

The static and fatigue cyclic strength of high-strength corrosion-resistant nitrogen-bearing austenitic 05Kh22AG15N8MF steel are studied in various structural states after hot rolling at 1100°C (water quenching from 1150°C, subsequent annealing at 800°C for 1 and 10 h, and cooling in air). The maximum life and a higher fatigue limit (400 MPa) are shown to be characteristic of hot-rolled samples with a finegrained austenitic structure and numerous twins. The mechanisms of fatigue crack propagation are studied.     

Effect of hot-rolling and heat-treatment conditions on the structure and mechanical and technological properties of nitrogen-bearing austenitic steel 05Kh22AG15N8M2F-Sh

The effect of hot-rolling conditions on the structure, strength, ductility, fracture toughness, and technological properties of the nonmagnetic steel 05Kh22AG15N8M2F-Sh containing 0.55% N has been studied. A homogeneous and fine-grained austenitic structure forms in the steel upon rolling at 1000–1050°C and a reduction of more than 60–70%. This structure provides the following properties: σ_0.2 = 1044 N/mm², σ_u = 1172 N/mm², δ = 32%, ψ = 64%, and KCV = 1.06 MJ/m² at ?70°C. The possibility of recrystallization of the hot-rolled steel (deformed at 10–90% reductions) is checked upon its subsequent heating to 850–1200°C followed by water quenching. The steel is shown to have high strength, ductility, and fracture toughness and to retain an austenitic structure without cracks or exfoliation upon hot plastic deformation by rolling up to a 90% reduction.     

Effect of the rolling temperature on the structure and the mechanical properties of high-nitrogen austenitic steels 05Kh21G9N7AMF and 04Kh22G12N4AMF

The structure and the mechanical properties of high-nitrogen austenitic 05Kh21G9N7AMF (0.56% N) and 04Kh22G12N4AMF (0.49% N) steels have been studied after hot rolling. It is found that the temperatures of the onset and end of hot deformation influence the structure and the mechanical properties of these steels. The higher set of mechanical properties of steel 05Kh21G9N7AMF after rolling in the temperature range 1100–900°C is due to the formation of a lamellar and equiaxed fragmented structure.     

Effect of cold plastic deformation on the structure and corrosion resistance of austenitic aging 0Kh18N2A alloy

The effect of deformation on the structure and related chemical properties of an austenitic 0Kh18N2A alloy with an overequilibrium nitrogen content has been studied. Cold plastic deformation at an 8–11% reduction before aging at 350°C is shown to halve the corrosion rate of the alloy as compared to the undeformed state. A thermoplastic treatment by the schedule quenching + aging at 350°C + 20% reduction is found to be more effective: the corrosion rate decreases by an order of magnitude as compared to the undeformed state.     

Structure,properties, and deformation behavior of corrosion-resistant steel 12Kh18N10T subjected to equal-channel angular pressing

The results of investigation into the evolution of structure, properties, and deformation behavior of corrosion-resistant steel 12Kh18N10T in the course of severe plastic deformation by equal-channel angular pressing are reported. The formation of a fibrous ultrafine-grained structure of the steel, its twofold hardening accompanied by a slight decrease in the plasticity, and changes in the cold-deformation mechanism are shown.     

Structure of a cast high-strength corrosion-resistant 05Kh20AG10N3MF austenitic steel containing 0.40 or 0.53% nitrogen

The phase composition and fine structure of a high-strength corrosion-resistant 05Kh20AG10N3MF austenitic steel containing 0.40 or 0.53% N are studied by X-ray diffraction and electron microscopy. In the as-cast state, this steel has a structure containing austenite, δ ferrite, and dispersed CrV(C, N) carbonitrides. The δ ferrite is represented by layers between austenite grains, the dislocation density in which is lower than in the δ ferrite. After quenching from 1100, 1150, and 1200°C, the structure of the steel with 0.53% N has no δ ferrite and the structure of the steel with 0.40% N has a low δ-ferrite content and χ-phase precipitates.     

冷轧压下率对TRIP钢组织与力学性能的影响

研究了含铝TRIP钢在相同的热处理条件和不同冷轧压下率时的组织和力学性能。结果表明,随着冷轧压下率增加,材料组织细化,屈服强度连续升高;而抗拉强度和伸长率则由于晶粒细化以及TRIP效应,先升高后降低。冷轧压下率74%时材料的综合性能最佳,此时带状组织的危害也有所减轻或消失。     

Influence of deformation on the structure and mechanical and corrosion properties of high-nitrogen austenitic 07Kh16AG13M3 steel

The correlation has been studied between the structure of a high-nitrogen austenitic Cr-Mn-N steel formed in the process of combined hardening treatment, including cold plastic deformation (CPD), and its mechanical and corrosion properties. The structure and properties of commercial high-nitrogen (0.8% N) 07Kh16AG13M3 steel is analyzed after rolling by CPD and aging at 500 and 800°C. It is shown that CPD of the steel occurs by dislocation slip and deformation twinning. Deformation twinning and also high resistance of austenite to martensitic transformations at true strains of 0.2 and 0.4 determine the high plasticity of the steel. The contribution of the structure imperfection parameters to the broadening of the austenite lines during CPD is estimated by X-ray diffraction. The main hardening factor is stated to be lattice microdistortions. Transmission electron microscopy study shows that heating of the deformed steel to 500°C leads to the formation of the intermediate CrN phase by a homogeneous mechanism, and the intermtallic χ phase forms along the austenite grain boundaries in the case of heating at 800°C. After hardening by all investigated technological schemes, exception for aging at 800°C, the steel does not undergo pitting corrosion and is slightly prone to a stress corrosion cracking during static bending tests, while aging at 800°C causes pitting corrosion at a pitting formation potential E _pf = ?0.25 V.     

Effect of quenching conditions on the formation of the grain structure and the mechanical properties of high-nitrogen austenitic 02Kh20AG14N8MF and 02Kh20AG12N4 steels

The formation of the grain structure of high-nitrogen 02Kh20AG14N8MF and 02Kh20AG12N4 steels in forging and quenching and their mechanical properties in this state have been studied. It is found that both steels have close mechanical properties under the same quenching conditions. In 02Kh20AG14N8MF steel, a homogeneous structure of primarily recrystallized austenite grains forms under the quenching conditions under study. In 02Kh20AG12N4 steel, the processes of secondary recrystallization and normal grain growth take place.     

Structure and mechanical properties of corrosion-resistant high-nitrogen 04Kh22AG15N8M2F and 05Kh19AG10N7MFB steels after hot deformation

The structure and mechanical properties of corrosion-resistant high-nitrogen austenitic 04Kh22AG15N8M2F and 05Kh19AG10N7MFB steels are studied after hot rolling at 950 and 1100°C. The following specific features of the structure of hot-rolled 04Kh22AG15N8M2F steel are revealed: the presence of coarse grain-boundary precipitates of the molybdenum-rich ?? phase and its nonuniform distribution over the volume of austenite grains. The 05Kh19AG10N7MFB steel hot rolled at 950°C contains ultrafine carbonitrides particles and has the best combination of a high strength and a sufficient elasticity and impact toughness. The structures of the hot-rolled steels have no ferrite, martensite, and traces of recrystallized austenite grains.     

Formation of a submicrocrystalline structure in austenitic 08Kh18N10T steel during equal-channel angular pressing followed by heating

The structure and mechanical properties of austenitic 08KhN10T steel subjected to equal-channel angular pressing (ECAP) at room temperature (? = 3.2) and subsequent heating are studied. In the course of ECAP, the steel undergoes a martensitic transformation; the martensite content reaches 45%. Upon heating, martensite (ferrite) transforms into austenite. The partly submicrocrystalline oriented structure of the 08Kh18N10T steel in the austenitic (55%)-martensitic (45%) state (formed upon ECAP) provides its high strain hardening (σ_0.2 = 1315 N/mm²), as compared to the initial state (σ_0.2 = 250 N/mm²), and high plasticity δ = 11%. After heating to 550°C, the steel has a predominantly submicrocrystalline austenitic (80%)-ferritic (20%) structure, σ_0.2 = 1090 N/mm², and δ = 11%.