Influence of alternating cold flexure on the properties of low-alloy pipe steel (strength class K56–K65)

In laboratory conditions, the cold straightening of thick (17.5 mm) low-carbon low-alloy steel sheet (yield point no less than 550 N/mm²) is simulated by alternating flexure. The influence of the number of cycles and the strain in alternating flexure on the strength of the steel is studied. For industrial production on the 5000 mill at OAO Vyksunskii Metallurgicheskii Zavod (VMZ), the influence of the cold-rolling conditions on the yield point and strength of thick (15–23 mm) steel sheet (strength class K56–K65) is demonstrated.     

Influence of heat treatment conditions on the mechanical properties of Ti–6Al–4V alloy

In the current work, several heat treatments were carried out below and above the beta-transition temperature of the Ti–6Al–4V alloy followed by aging at 550 °C for 6 hours. The resultant microstructures and their effects on the mechanical properties of Ti–6Al–4V alloy were investigated. The results showed that solution treatment of Ti–6Al–4V samples followed by water quenching from β and α/β fields raised the alloy hardness from 380 to 575 and 656?HV, respectively, while no remarkable changes were observed after aging. The hot tensile strength of the as-forged sample increased from 671 to 756?MPa after water quenching from the ß- or α/ß- field, while the air cooling from β-phase field decreased the tensile strength to 644 MPa. The fracture mode of the tensile samples was more ductile in case of the solution-treated samples compared to the as-forged samples. A subsurface layer was formed due to the diffusion of oxygen into the surface at high temperatures. This layer which is known as ‘oxygen diffusion layer’ masked the differences of wear behaviour of the specimens.     

Influence of hot isostatic pressing on the structure and properties of an innovative low-alloy high-strength aluminum cast alloy based on the Al–Zn–Mg–Cu–Ni–Fe system

Hot isostatic pressing (HIP) is applied for treatment of castings of innovative low-ally high-strength aluminum alloy, nikalin ATs6N0.5Zh based on the Al–Zn–Mg–Cu–Ni–Fe system. The influence of HIP on the structure and properties of castings is studied by means of three regimes of barometric treatment with different temperatures of isometric holding: t ₁ = 505 ± 2°C, p ₁ = 100 MPa, τ₁ = 3 h (HIP1); t ₂ = 525 ± 2°C, p ₂ = 100 MPa, τ₂ = 3 h (HIP2); and t ₃ = 545 ± 2°C, p ₃ = 100 MPa, τ₃ = 3 h (HIP3). It is established that high-temperature HIP leads to actually complete elimination of porosity and additional improvement of the morphology of second phases. Improved structure after HIP provides improvement properties, especially of plasticity. In particular, after heat treatment according of regime HIP2 + T4 (T4 is natural aging), the alloy plasticity is improved by about two times in comparison with the initial state (from ~6 to 12%). While applying regime HIP3 + T6 (T6 is artificial aging for reaching the maximum strength), the plasticity has improved by more than three times in comparison with the initial state, as after treatment according to regimes HIP1 + T6 and HIP2 + T6 (from ~1.2 to ~5.0%), which are characterized by a lower HIP temperature.     

Water–air online quenching process of 3Cr2Mo steel based on numerical simulation

A three-dimensional finite element model was established to investigate the water–air online quenching process of 3Cr2Mo steel with 130-mm thickness. The temperature, metallographic structure and stress–strain fields of the steel were calculated under single-pass continuous quenching, multi-pass continuous quenching and multi-pass interrupted quenching (MPIQ) processes. The results show that the three quenching processes can avoid the pearlite appearance, and MPIQ process could be more effective to decrease the brittleness of steel. Besides, MPIQ process is able to reduce stress–strain, minimise deformation and avoid cracking problem. The hardness and the metallographic structure were tested after MPIQ process and tempering. After tempering, the metallographic structures were all tempered sorbite, and the hardness difference of the whole steel was less than 3HRC with no cracks. It can draw the conclusion that the MPIQ process is a suitable quenching process for 3Cr2Mo steel.     

Influence of the Oxygen Induced Surface Segregation Process of Solutes on the Anti-corrosion Properties of the Fe–Cr and Fe–Cr–Si Alloys

Metallurgical and Materials Transactions A - The influence of the oxygen-induced surface segregation process of Cr and Si solutes on the anti-corrosion properties of Fe–Cr and...     

Effect of austenitisation temperature on austenite transformations in 0·7%C Cr–Mo PM steel

Abstract

The effect of austenitisation temperature on austenite transformations on 0·7%C Astaloy CrL steel was studied by dilatometry. The steel has a good hardenability, forming martensite at most of the austenitisation temperatures and cooling rates investigated. Only on cooling from 1073 K, austenite transforms into bainite completely at 3 K s^?1 and partially at 12·5 K s^?1. The effect of austenitisation temperature on the prior austenitic grain size is quite poor because of the pinning effect of pores. The martensite start temperature M_s increases slightly with the austenitisation temperature up to 1173 K and decreases at 1523 K. This trend is due to the presence of nanometric carbides (Cr₂₃C₆), which were detected at TEM. They dissolve almost completely in austenite at 1523 K only, increasing the stability of austenite against the martensitic transformation. The effect of temperature in the range from 1073 K up to 1523 K is poor. As a consequence, the microstructural characteristics of hardened steels are very similar.     

Effect of Cr–Mo Addition on the Microstructure and Mechanical Properties of Medium-Carbon Steel

Herein, the effects of Chromium–Molybdenum (Cr–Mo) addition on the microstructural evolution and mechanical properties of medium-carbon steel after spheroidization annealing are systematically studied through scanning electron microscopy, electron backscatter diffraction, and tensile testing. Cr–Mo addition hinders the proeutectoid ferrite + pearlite transformation, thereby promoting the bainite transformation. Moreover, it refines the pearlite lamellar spacing as well as decreases the average carbide diameter, increases the number of carbides per unit area, and hinders ferrite recrystallization. Compared with those in the B1 steel annealed for 8 h, the size of carbides and their number per unit area in the CM1 steel are 30% lower and 2.2-fold higher, respectively. Due to finer ferrite grains, smaller carbides, and a higher amount of carbides, the strength of steel improves, and the plasticity slightly reduces after Cr–Mo addition. After 2 h of annealing, the yield strengths of Cr–Mo steels are 77.5–109.5 MPa higher than those of base steels; the elongations are above 20%. The contributions of the strengthening mechanism of steel to the yield strength are as follows (from high to low): grain boundary, precipitation, solid solution, and dislocation strengthening.     

Influence of the solidification temperature–time parameters on the structure and mechanical properties of nickel aluminide–based alloys

The influence of the technological parameters of directional solidification, namely, the solidification rate and the temperature gradient, on the microstructure, the structure–phase parameters, and the mechanical properties of nickel aluminide–based intermetallic alloys is considered.     

Influence of alloying titanium carbonitride by transition metals of groups IV–VI on the interaction with the nickel melt

The influence of alloying titanium carbonitride TiC_0.5N_0.5 by transition metals of Groups IV–VI on the mechanism of contact interaction with the nickel melt is studied. It is established that alloying metals exert a strongly destabilizing influence on titanium carbonitride TiC_0.5N_0.5, simultaneously increasing both its dissolution rate in nickel and the degree of process incongruence (the preferential transition of alloying metal and carbon into the melt). The influence of alloying on the phase stability of titanium carbonitride TiC_0.5N_0.5 in contact with a nickel melt manifests itself in its dehomogenization or phase separation. The destabilizing effect of alloying additives enhances in a series Me^IV–Me^V–Me^VI parallel with a decrease in their nitrogen affinity.     

Atom probe analysis of 2.25 Cr1Mo steel

Atom probe mass analysis was conducted on 2.25 Cr1Mo and 2.25 Cr steels containing a small amount of P and problems associated with this analysis were described. A reliable compositional analysis by the atom probe of these low alloying steels was demonstrated by comparing the compositions determined by the atom probe and by a chemical analysis. In order to apply the atom probe technique to the study of temper embrittlement of 2.25 Cr1 Mo steel, compositional variations with aging time at 773 K of alloy elements and P in ferrite phase were examined. It was found that Cr and P concentrations in ferrite increased within 10 h of the early stage of aging and then gradually decreased with further aging, while Mo concentration simply decreased with aging. It was suggested that P atoms in as tempered steel were concentrated in ferrite-cementite boundaries and they were dissolved into ferrite during a process in which M₃C was replaced by M₂C in the early stage of aging. These dissolved P atoms were then segregated to grain boundaries causing the temper embrittlement. It was found that the presence of Mo retarded the decrease of P concentration in ferrite with aging thus suppressing the grain boundary segregation of P.     

Influence of Molybdenum and Rhenium Dopants on the Structure and Properties of NiAl–Cr–Co Cast Alloy

Russian Journal of Non-Ferrous Metals - Centrifugal SHS casting has been used for the production of NiAl–Cr–Co–X alloys, where X = 2.5–15.0 wt % Mo and up to 1.5 wt % Re....     

Research on the heat treatment of tool steel 5Cr15MoV

Tempered tool steel 5Cr15MoV was normalized at different temperatures followed by air-cooling.It is found that the hardness increases with the increment of a normalizing temperature from 950℃ to 1 150℃,and it then decreases with the temperature getting higher.The Thermo-calc calculation reveales that the mole fraction of carbides decreases when the normalizing temperature increases,which indicates that more carbon dissolved in the matrix enhances the hardness of the steel.However,the existence of retained austenite causes hardness reduction when the normalizing temperature is over 1 150℃.The salt spray test shows that the steel possesses poor corrosion resistance when it is normalized at a temperature above 1 100℃.The precipitation of the carbides in the cooling process creates a number of chromium-depleted zones,making the steel vulnerable to corrosives.In the present work,an appropriate normalizing temperature is suggested.     

Influence of the packing-defect energy on the abrasive wear resistance of Fe–12Mn–1.2C steel castings cooled at different rates

The influence of the cooling rate of castings on the abrasive wear resistance is considered. It is shown that the wear resistance depends on the layer hardened by deformational twinning at the wear surface. According to the results, the maximum thickness of the hardened layer on the casting is formed at both low and high cooling rates. This is associated with decrease in the packing-defect energy, which, in turn, depends on the concentration of manganese, chromium, and silicon. At a moderate cooling rate, the degree of alloying of the austenite is such that the packing-defect energy is increased. Deformation twinning (TWIP) is hindered, and the hardened layer is of minimal thickness, if it appears at all.     

Influence of Oxygen on the Kinetics of Omega and Alpha Phase Formation in Beta Ti–V

Metallurgical and Materials Transactions A - A detailed understanding of the kinetics of phase formation in $$beta $$ -stabilised titanium is of decisive importance for the applicability of these...     

Influence of treatment of melts by electromagnetic acoustic fields on the structure and properties of alloys of the Al–Si system

The influence of treating the melts by electromagnetic acoustic fields on the structure and properties of Al–12% Si and Al–20% Si binary alloys is investigated. In the course of experiments, the frequency of the electromagnetic field induced in the loop antenna varies as 500, 1000, and 2000 kHz. The melts are treated after their degassing and refining. It is established that this treatment method of the melts leads to a reduction of the total preparation time of alloy by 12% on average. The short-term treatment of the melts by electromagnetic acoustic fields promotes the refinement of the main phase components of alloys and an increase in their mechanical properties. When treating the Al–12% Si eutectic alloy with a frequency of 500 kHz, α-Al dendrites are refined from 30 to 22 μm and eutectic Si crystals are refined from 13 to 10 μm. When treating the Al–20%Si eutectic alloy with a frequency of 1000 kHz, eutectic Si crystals diminished from 8 to 5 μm and these of primary Si diminished from 90 to 62 μm. The ultimate tensile strength of the Al–12%Si eutectic alloy increases 13% under the mentioned treatment modes, while the relative elongation increases 17%; as for the Al–20% Si eutectic alloy, the same characteristics increases 9 and 65%, respectively. Based on these investigations, it is concluded that the selection of the treatment parameters of the melts of the Al–Si system by electromagnetic acoustic fields should be determined by the silicon content in the alloy. It is necessary to treat the melt by waves with a higher oscillation frequency with an increase in the silicon concentration. This treatment method makes it possible to form the modified fine-crystalline structure of alloy and, consequently, improves their mechanical properties. It can be successfully used when fabricating fine-crystalline foundry alloys and in the production of alloys of the Al–Si system. To determine the optimal treatment parameters depending on the structure of the initial charge and alloy nature, additional investigations are required.