Search

The bearing steel's high-temperature brittle zone (1250 °C–1100 °C), second brittle zone (1100 °C–950 °C), and low-temperature brittle zone (800 °C–600 °C) were determined by the reduction in area and true fracture toughness. The crack sensitivity was strongest at temperatures of 1200 °C, 1000 °C, and 600 °C, respectively. Various experimental and computational methods were used to establish the phase type, microstructure, size, and mechanical properties of carbides in bearing steel. The critical conditions for crack initiation in the matrix (FCC-Fe, FCC-Fe, and BCC-Fe)/carbides (striped Fe0.875Cr0.125C, netted Fe2.36Cr0.64C, and spherical Fe5.25Cr1.75C3) were also investigated. The values for the high-temperature brittle zone, the second brittle zone, and the low-temperature brittle zone were 13.85 MPa and 8.21 × 10−3, 4.64 MPa and 6.52 × 10−3, and 17.86 MPa and 1.86 × 10−2, respectively. These were calculated using Eshelby's theory and ABAQUS 2021 version software. The ability of the three carbides to cause crack propagation was measured quantitatively by energy diffusion: M3C > MC > M7C3. This study analyzed the mechanism of carbide precipitation on the formation of high-temperature cracks in bearing steel casting. It also provided the critical conditions for carbide/matrix interface cracks in bearing steel continuous casting, thus providing effective support for improving the quality of bearing steel casting. [ABSTRACT FROM AUTHOR]

The new cast steel with a chemical composition of Fe-(0.85-0.95)C-(1.50-1.60)Si-(2.40-2.60)Mn-(1.0-1.2)Al-(0.30-0.40)­Mo-(0.10-0.15)V-(1.0-1.1)Ni (all in wt.%) was investigated in aspect of formation of the multiphase microstructure leading to high strength and ductility. Two types of heat treatment technologies were developed. The first one involves softening annealing at a temperature of 650°C for 4 hours, heating up to 950°C and holding for 2 hours, and then fast cooling down to 200°C and isothermally treated for 2 hours. The second one involves homogenizing annealing at 1100°C for 6 hours, then cooling with furnace down to 950°C and holding for 2 hours, then fast cooling down to 200°C and isothermally treated for 2 hours. A unique microstructure of cast steel consisting of martensite and retained austenite plates of various thicknesses and volume fractions was obtained. Additionally, nanometric transition carbides were noticed after the above-mentioned heat treatments. This microstructure ensures high hardness, strength and plasticity ( Rm = 1426 MPa and A = 9.5%), respectively, due to the fact that TWIP/TRIP processes occur during deformation related to the high volume fraction of retained austenite, which the stacking fault energy is above 15 mJ/m –2 resulting from the chemical composition of the investigated cast steel.

This article presents the results of research into the characteristics of cast steel alloyed with chromium and vanadium, subjected to heat treatment for increased strength parameters. In the first part, it discusses the state-of-the-art knowledge regarding technological developments in the field of cast-steel alloys and the influence of individual alloying additives on the microstructure and the properties of the steel alloy. Further sections present the results of microstructure observations performed with light microscopy, scanning electron microscopy, and transmission electron microscopy. This research focuses on the material in the state directly after casting and after heat treatment, which involved quenching and tempering at 200 °C. The microstructural analysis performed as part of this research has informed the discussion of the results obtained from tensile and impact strength tests. The article also includes the results of a fractography analysis performed as the final part of the tests and offers a general summary and conclusions. [ABSTRACT FROM AUTHOR]

Cast steel parts can realize rapid prototyping effectively, which is suitable for complex structural design. However, due to the large residual stress, the problem of mechanical property degradation is more obvious. In order to solve this problem, a high temperature excitation vibration treatment scheme is proposed in this paper. By applying different excitation frequencies and impact forces, the effects of mechanical properties and stress corrosion properties are studied and verified. Based on the finite element software ANSYS, the modal shape and resonant frequency of the cast steel parts are obtained, and verified by the sweep frequency module in the excitation vibration system. According to the characteristics of modal shape, five typical detection paths are set, and stress sensors are arranged every 200 mm. In order to obtain the specific effects of excitation frequency and impact force amplitude on mechanical properties, nine parts samples were prepared on the same production line according to the matching requirements of test parameters. In addition, the main external parameters that remain unchanged during vibration excitation are set as initial 750 ℃ and vibration excitation time of 60 s, which can fully affect the effect of austenite transformation. Keeping the synchronization of test parameters in different samples, the distribution rules of residual stress under different excitation frequencies and forces are obtained and analyzed. In the aspect of mechanical properties, the microstructure, hardness, yield strength and tensile strength of the specimens subjected to vibration were compared and analyzed. In the aspect of stress corrosion performance research, stress corrosion cracking test was carried out in weak acid environment to obtain the tensile stress curve and fracture morphology of the specimen. The results show that the excitation vibration at high temperature can effectively eliminate the residual stress of cast steel parts, but the increase of excitation frequency does not correspond to the effect of residual stress elimination. When the exciting force exceeds a certain value, the stress relief effect cannot be further improved. Excitation vibration can reduce the internal hardness of cast steel parts to a certain extent, and improve the yield strength and tensile strength. At the same time, it has a positive role in promoting the improvement of stress corrosion resistance. [ABSTRACT FROM AUTHOR]

The paper presents the research results on duplex corrosion-resistant chromium–nickel–molybdenum cast steel of the GX2CrNiMoCuN 25-6-3-3 grade. The aim was to determine the effect of the soaking temperature for the hyperquenching process Tp, that is, 950 to 1200 °C, on the microstructure and mechanical properties, that is UTS tensile strength, the yield strength, HB Brinell hardness, the elongation EL and impact strength KV of the steel, cast under industrial conditions with the minimum content of Cr, Ni, Mo and Cu according to the PN-EN 10283 standard. On the basis of the results, it was confirmed that the hyperquenching guarantees the elimination of the brittle intermetallic phase in the steel microstructure. In addition, the most favorable strength-to-ductility ratio of the steel with an almost equal amount of austenite γ and ferrite α in its microstructure was obtained using the soak temperature of 1080 °C, which was considered optimal for the above-mentioned duplex cast steel. [ABSTRACT FROM AUTHOR]

The new cast steel with a chemical composition of Fe-(0.85-0.95)C-(1.50-1.60)Si-(2.40-2.60)Mn-(1.0-1.2)Al-(0.30-0.40)- Mo-(0.10-0.15)V-(1.0-1.1)Ni (all in wt.%) was investigated in aspect of formation of the multiphase microstructure leading to high strength and ductility. Two types of heat treatment technologies were developed. The first one involves softening annealing at a temperature of 650°C for 4 hours, heating up to 950°C and holding for 2 hours, and then fast cooling down to 200°C and isothermally treated for 2 hours. The second one involves homogenizing annealing at 1100°C for 6 hours, then cooling with furnace down to 950°C and holding for 2 hours, then fast cooling down to 200°C and isothermally treated for 2 hours. A unique microstructure of cast steel consisting of martensite and retained austenite plates of various thicknesses and volume fractions was obtained. Additionally, nanometric transition carbides were noticed after the above-mentioned heat treatments. This microstructure ensures high hardness, strength and plasticity (Rm = 1426 MPa and A = 9.5%), respectively, due to the fact that TWIP/TRIP processes occur during deformation related to the high volume fraction of retained austenite, which the stacking fault energy is above 15 mJ/m–2 resulting from the chemical composition of the investigated cast steel. [ABSTRACT FROM AUTHOR]

In this paper, an experimental Mg-Al-RE-type magnesium alloy, named AEZ951, is presented. The chemical composition of the investigated alloy was ca. 9 wt% Al, 5 wt% RE (rare earth elements), 0.7 wt% Zn and 3 wt% Mn. The experimental material was gravity cast into a cold steel mould. Microstructure analyses were carried out by light microscopy, along with X-ray phase analysis and scanning electron microscopy with an energy-dispersive X-ray spectrometer (SEM + EDX). Detailed investigations disclosed the presence of primary dendrites of an α(Mg) solid solution and Al11RE3, γ and Al10RE2Mn7 intermetallic compounds in the alloy microstructure. The volume fraction of the Al11RE3 phase and α+γ eutectic was also presented. The hardness, impact strength, tensile strength as well as the yield strength of the alloy were examined in tests at room temperature. The examined experimental Mg-Al-RE-type magnesium alloy exhibited higher mechanical properties than the commercial AZ91 alloy (cast in the same conditions). [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of 4Kh4N5M4F2 steel in thermodeformed and cast states after quenching and tempering, and additional heating are investigated. After additional heating of hardened and tempered 4Kh4N5M4F2 steel, which models the operating conditions of the equipment (operating temperature during quasi-stationary exposure), at 630–650°C steel softens, which is associated with the formation of Me7C3 carbides. Such carbide phase in the metal structure of the cast steel under mentioned conditions is absent and is accompanied by the increase in its heat resistance. The expansion of the operating temperature range of cast 4Kh4N5M4F2 steel after the optimal mode of hardening and tempering allows using a tool made of this steel up to the operating temperature of 650°C. It is recommended not to use such steel in the cast and thermodeformed states for the manufacture of tools for hot deformation of non-ferrous metals and alloys, which operate under cyclic impact loading. [ABSTRACT FROM AUTHOR]

Postfire mechanical properties and fracture resistance of G20MnQT cast steels were investigated experimentally and effects of different cooling procedures were studied. G20Mn5QT cast steels were heated to 600°C, 700°C, 800°C, and 900°C and cooled to ambient temperature in air or in water. Metallographic examination found significant phase transformations only in G20Mn5QT cast steels cooled quickly in water from elevated temperatures of 800°C (800W) and 900°C (900W). Original ferrite and pearlite transformed to harder phases, such as martensite and bainite, in these two postfire materials. Vickers hardness tests, Charpy impact tests, and tension coupon tests were conducted on original and postfire G20Mn5QT cast steels. All test results confirmed the findings about phase transformation in metallographic examination. The martensite and bainite generated in phase transformation caused significant hardening of 800W and 900W. With no significant phase transformation, most mechanical properties of 600A, 600W, 700A, 700W, 800A, and 900A varied within ±15% compared with those of the original material, and the postfire Charpy impact energies increased moderately due to improvement of material homogeneity. Smooth notched tensile specimens were tested and material parameters in the void growth model were calibrated to evaluate the postfire fracture resistance of G20Mn5QT cast steels at high stress triaxialities. It was found that the fracture of 600A, 600W, 700A, 700W, 800A, and 900A was almost as ductile as that of the original G20Mn5QT cast steels, whereas 800W and 900W fractured brittlely, and had fracture resistance 87.6% and 78.4% lower than that of the original material. [ABSTRACT FROM AUTHOR]

We study metal samples taken from two batches of hot-rolled, semi-finished steel products and two batches of grade HC340LA cold-rolled steel, annealed in bell-type furnaces, produced from transitional slabs obtained by continuous casting of the developed high-strength, low-alloy, microalloyed, auto-sheet steel microalloyed with titanium (Ti) onto steel microalloyed with niobium (Nb). Based on the results obtained, for the first time, the possibility of continuous casting of the developed high-strength, low-alloy, auto-sheet steel microalloyed with Ti onto steel microalloyed with Nb is established. It is revealed that both grade S420MS hot-rolled steel according to EN 10149 and grade HC340LA cold-rolled steel, annealed in bell-type furnaces, can be simultaneously produced from transitional slabs while meeting EN 10268 requirements with reduced costs. [ABSTRACT FROM AUTHOR]

In this work, the effect of Ti addition and the cast part size on the solidification structure and mechanical properties of a medium carbon, low alloy cast steel was analyzed. The experimental analysis involved the design of the melts by using Thermo-Calc� software, where different amounts of Ti added to a standard chemical composition of an AISI 13XX steel were simulated. Then, the solidification macrostructure (dendritic pattern and grain size) and microstructure were characterized by using conventional and specific metallographic techniques. Finally, the mechanical behavior in terms of hardness and tensile properties were evaluated. The results show that the addition of 0.12% of Ti promotes a fine dispersion of Ti nitrides and carbides, but when the Ti concentration raises to 0.2%, the size of the Ti nitrides and carbides increases while its amount decreases. Ti nitrides and carbides particles act as nucleation sites for the precipitation of ferrite from austenite, and it was found that the addition of Ti in the higher concentrations refines the solidification macrostructure (dendritic pattern) for both cast part sizes evaluated. Regarding mechanical properties, the addition of Ti does not significantly vary the ultimate tensile strength but reduces the total elongation for cast part sizes

In this study, the characterization of production welds for high manganese steel castings exposed to little or no wear and moderate stresses, using the ER 307 stainless steel covered electrode, was investigated. The macro- and microstructural examinations were performed by means of stereo microscopy, optical microscopy, scanning electron microscopy and energy-dispersive spectrometry (EDS) to differentiate weld metal, partially melted zone (PMZ), heat-affected zone (HAZ), and base material (BM). Transverse micro-hardness test, Charpy impact tests and ultimate tensile tests were performed to evaluate the mechanical properties of the joints. The chemical analysis and elemental mapping were utilized to analyze the joint cross section in percentage weight with both optical emission spectrometer and X-ray spectrometer. The results indicated that the reduction in dilution from root to face regions led to an increase in the amount of delta ferrite contents through the weld passes from the root to the face. Moreover, the liquation cracks occurred due to the combination of eutectic phase formation, low thermal conductivity, and the large freezing range of the base metal. These cracks originated at the PMZ and propagated from the PMZ through HAZ to BM and lowered the tensile strength, % elongation and toughness of the weld joint by about 6 %, 27 % and 33.5 %, respectively. [ABSTRACT FROM AUTHOR]

In this study, a newly developed high-strength cast Fe81Cr15V3C1 (wt%) steel with a high resistance against dry abrasion and chloride-induced pitting corrosion is presented. The alloy was synthesized through a special casting process that yielded high solidification rates. The resulting fine, multiphase microstructure is composed of martensite, retained austenite and a network of complex carbides. This led to a very high compressive strength (>3800 MPa) and tensile strength (>1200 MPa) in the as-cast state. Furthermore, a significantly higher abrasive wear resistance in comparison to the conventional X90CrMoV18 tool steel was determined for the novel alloy under very harsh wear conditions (SiC, α-Al2O3). Regarding the tooling application, corrosion tests were conducted in a 3.5 wt.% NaCl solution. Potentiodynamic polarization curves demonstrated a similar behavior during the long-term testing of Fe81Cr15V3C1 and the X90CrMoV18 reference tool steel, though both steels revealed a different nature of corrosion degradation. The novel steel is less susceptible to local degradation, especially pitting, due to the formation of several phases that led to the development of a less dangerous form of destruction: galvanic corrosion. In conclusion, this novel cast steel offers a cost- and resource-efficient alternative to conventionally wrought cold-work steels, which are usually required for high-performance tools under highly abrasive as well as corrosive conditions. [ABSTRACT FROM AUTHOR]

Low‐alloy cast steel with ultrahigh strength is produced by a combination of normalizing and reheating, followed by water quenching and high‐temperature tempering. The cast steel quenched at 1000 °C for 30 min and tempered at 550 °C for 120 min exhibits superior tensile ductility. More precisely, the tensile strength is 1683.5 MPa, yield strength is 1635.3 MPa, elongation is 12.0%, and microhardness is 500.3 HV. The microstructure is composed of martensite lath + ferrite + M23C6 carbide. The strengthening mechanisms of the steel are mainly precipitation, grain refinement, and dislocation strengthening. When the quenching temperature is increased from 950 to 1000 °C, the M3C carbides precipitated between the martensite lath are transformed from short rod‐like to spherical shapes, which improves the plasticity of the steel. When the tempering temperature is increased from 550 to 630 °C, the number and size of the carbides also increase. The M23C6 carbides interact with the dislocations. M23C6 carbides play a crucial role in the precipitation strengthening and efficiently improve the strength of the steel. The fracture is changed from a mixed ductile and brittle fracture to a ductile fracture. [ABSTRACT FROM AUTHOR]

In this work, the effect of Ti addition and the cast part size on the solidification structure and mechanical properties of a medium carbon, low alloy cast steel was analyzed. The experimental analysis involved the design of the melts by using Thermo-Calc® software, where different amounts of Ti added to a standard chemical composition of an AISI 13XX steel were simulated. Then, the solidification macrostructure (dendritic pattern and grain size) and microstructure were characterized by using conventional and specific metallographic techniques. Finally, the mechanical behavior in terms of hardness and tensile properties were evaluated. The results show that the addition of 0.12% of Ti promotes a fine dispersion of Ti nitrides and carbides, but when the Ti concentration raises to 0.2%, the size of the Ti nitrides and carbides increases while its amount decreases. Ti nitrides and carbides particles act as nucleation sites for the precipitation of ferrite from austenite, and it was found that the addition of Ti in the higher concentrations refines the solidification macrostructure (dendritic pattern) for both cast part sizes evaluated. Regarding mechanical properties, the addition of Ti does not significantly vary the ultimate tensile strength but reduces the total elongation for cast part sizes. [ABSTRACT FROM AUTHOR]

This work presents the novel high‐strength cast steels Fe81Cr15Mo1V2C1 and Fe80Cr15Mo1V3C1 (wt%) with high resistance against abrasion and acid corrosion. By means of a tailored alloy design and a special casting technique, implying high solidification rates, multiphase microstructures composed of martensite, austenite and a complex arranged carbidic network are formed. The increase of the vanadium concentration by 1 wt% results in an enhanced content of martensite and a decreased fraction of metastable retained austenite as detected by X‐ray diffraction and magnetization studies. This affects significantly the deformation, strengthening and wear behavior of the presented cast steels. Nevertheless, both steels achieve very high compressive (>4500 MPa) and tensile strengths (>1100 MPa) already in the as‐cast state. Furthermore, a distinctly higher abrasive wear resistance than the conventional X90CrMoV18 cold‐work steel was determined for the novel alloys. In conclusion, the results of the microstructural, mechanical, tribological and corrosive characterizations illustrate the impact of alloy design and special solidification conditions on the microstructure and resulting properties for the newly developed cast steels. In addition, the high potential of Fe81Cr15Mo1V2C1 and Fe80Cr15Mo1V3C1 as materials for high‐performance tools, requiring high strength besides high resistance against abrasive wear and acid corrosion, is demonstrated. [ABSTRACT FROM AUTHOR]

In this work, the effect of Ti addition and the cast part size on the solidification structure and mechanical properties of a medium carbon, low alloy cast steel was analyzed. The experimental analysis involved the design of the melts by using Thermo-Calc® software, where different amounts of Ti added to a standard chemical composition of an AISI 13XX steel were simulated. Then, the solidification macrostructure (dendritic pattern and grain size) and microstructure were characterized by using conventional and specific metallographic techniques. Finally, the mechanical behavior in terms of hardness and tensile properties were evaluated. The results show that the addition of 0.12% of Ti promotes a fine dispersion of Ti nitrides and carbides, but when the Ti concentration raises to 0.2%, the size of the Ti nitrides and carbides increases while its amount decreases. Ti nitrides and carbides particles act as nucleation sites for the precipitation of ferrite from austenite, and it was found that the addition of Ti in the higher concentrations refines the solidification macrostructure (dendritic pattern) for both cast part sizes evaluated. Regarding mechanical properties, the addition of Ti does not significantly vary the ultimate tensile strength but reduces the total elongation for cast part sizes

In the present research, the microstructure and mechanical properties of low-density Fe-0.72Mn-3.7Al-0.53C steel were investigated after solution treatment at 900 °C, 1000 °C, 1110 °C and 1200 °C for 1 h. The density of steel is about 7.0 g·cm−3 due to the addition of a higher content of aluminum elements. The microstructure was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanical behavior was analyzed by room temperature tensile testing. The results show that the microstructure of the steel is ferrite and martensite after solution treatment, and that martensite can be divided into dislocation martensite and twinned martensite according to different substructures. Part of the martensite grows in a mirror-symmetrical manner in order to adjust the strain energy that increases with the system undercooling to form twinned martensite. After solution treatment at different temperatures, the tensile strength and elongation of the steel increased and then decreased with the increase of the solution treatment temperature, and the tensile strength could reach 928.92 MPa, while maintaining excellent toughness and elongation at 5.89%. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the resistance of cast duplex (austenitic-ferritic) steels to pitting corrosion with respect to the value of PREN (Pitting Resistance Equivalent Number). Pitting corrosion is one of the most common types of corrosion of stainless steels. In most cases, it is caused by the penetration of aggressive anions through the protective passive layer of the steel, and after its disruption, it leads to subsurface propagation of corrosion. The motivation for the research was a severe pitting corrosion attack on the blades of the gypsumcalcium water mixer in a thermal power plant operation. In order to examine the corrosion resistance, 4 samples of 1.4517 steel with different concentrations of alloying elements (within the interval indicated by the steel grade) and thus with a different PREN value were cast. The corrosion resistance of the samples was evaluated by the ASTM G48 – 11 corrosion test in a 6% aqueous FeCl3 solution at room and elevated solution temperatures. To verify the possible effect of different alloying element concentrations on the mechanical properties, the research was supplemented by tensile and Charpy impact tests. Based on the results, it was found that a significant factor in the resistance of duplex steels to pitting corrosion is the temperature of the solution. For the components in operation, it is therefore necessary to take this effect into account and thoroughly control and manage the temperature of the environment in which the components operate. [ABSTRACT FROM AUTHOR]

Plastic deformation and damage evolution in low-carbon cast steel containing non-metallic inclusions are analyzed experimentally and numerically. The cast steel was subjected to the heat treatment: normalizing, oil quenching and tempering. Tests were carried out at hydrostatic pressure of 500 MPa and 1 000 MPa. In the tensile test the tensile strength, elongation and reduction of area were examined. Fractography of the specimens was carried out to observe fracture mechanisms. The finite elements method has been used for modelling of deformation of the specimens. The computer simulation was performed using ABAQUS system. The computed output was compared with experimental results

The results of tests and examinations of the microstructure and mechanical properties of cast steel used for large-size slag ladles are presented. Castings of this type (especially large-size ladles with a capacity of up to 16 m3) operate under very demanding conditions resulting from the repeated cycles of filling and emptying the ladle with liquid slag at a temperature exceeding even 1600°C. The changes in operating temperature cause faster degradation and wear of slag ladle castings, mainly due to thermal fatigue. The tests carried out on samples taken from different parts/areas of the ladle (flange, bottom and half-height) showed significant differences in the microstructure of the flange and bottom part as compared to the microstructure obtained at half-height of the ladle wall. The flange and bottom were characterized by a ferritic-pearlitic microstructure, while the microstructure at the ladle half-height consisted of a ferritic matrix, cementite and graphite precipitates. Changes in microstructure affected the mechanical properties. Based on the test results it was found that both the flange and the bottom of the ladle had higher mechanical properties, i.e. UTS, YS, hardness, and impact energy than the centre of the ladle wall. Fractography showed the mixed character of fractures with the predominance of brittle fracture. Microporosity and clusters of non-metallic inclusions were also found in the fractures of samples characterized by low properties.

Boron and carbon contents are the main factors influencing the properties of high-boron steel. In this study, experimental samples with different boron-to-carbon ratios (%B/%C) were prepared. The microstructures of the different samples were observed, and their hardness, bending strength, and impact toughness were investigated. Results show that the main microstructures in the investigated high-boron steel samples are the eutectic Fe2B structure with a fishbone shape and the ternary peritectic Fe3(C, B) structure with a chrysanthemum shape. When the boron content is 2.5wt.% and the carbon content is 0.43wt.% (i.e., %B/%C=5.82), the overall mechanical properties of the alloy are the best. The alloy's hardness, bending strength and impact toughness reach their maximums, which are 67.3 HRC, 1,267.36 MPa and 6.19 J·cm-2, respectively. The optimized alloy is compared with conventional materials exhibiting excellent wear resistance (namely, high-manganese steel and high-chromium cast iron) through two-body and three-body abrasion tests. The wear resistance of this high-boron steelinvestigated in this work is found to be superior to those of the more common materials. [ABSTRACT FROM AUTHOR]

A widely used corrosion protection technique for steel structures is hot‐dip galvanizing. This method increases the life of steel structures and reduces maintenance costs. In this technique, steel elements are cleansed through caustic cleaning, rinsing, pickling, and dipping in flux solutions. After cleaning, components are dipped in molten zinc until a protective layer is formed. The galvanizing procedure and its effects on structural mild steel materials have been studied. However, the effects of galvanizing on mechanical properties of high and ultra‐high‐strength steels (HSS and UHSS) have received limited attention. This mechanical investigation is vital since UHSS, and HSS steels are sensitive to heating and cooling cycles, and their mechanical behavior may change when exposed to high‐temperature during hot‐dip galvanizing. To this end, an experimental program was designed and carried out to find out the mechanical behavior of standard coupons taken from UHSS and HSS tubes after galvanizing. HSS and UHSS tubes were cleansed and dipped in a molten zinc bath (460 °C) for 3.0 and 10.0 minutes. For comparison, a mild steel tube with the same dimensions was also galvanized by dipping in zinc for 10.0 minutes. After galvanizing, dog‐bones and short tubes were cut out from the tubes for standard tensile and compressive tests, respectively. The tests revealed that the ultimate tensile strength of HSS and UHSS tubes decreased noticeably while the changes in their yield strengths were not significant. These changes were more significant for longer molten zinc bath dipping times. For HSS and mild steel specimens, the heat exposure had a similar effect as normalizing or annealing done after casting steel. For mild steel, normalizing or annealing increases yield, and ultimate strength and the same thing happened here. It was shown how the observed behaviors and changes were related to the grade of steel materials and their manufacturing process. Finally, optical microscopy was conducted to inspect the micro‐scale properties of the zinc layer. Microscopic results show that under the same zinc dipping time the zinc layer thickness on UHSS and HSS is almost double of that on mild steel which can increase the lifespan of the galvanized parts while decreasing the adhesion of the zinc layer to the steel base. [ABSTRACT FROM AUTHOR]

Three medium-carbon, high-silicon cast steels with different alloy contents were austempered at 330 °C for different holding times in order to obtain carbide-free bainitic microstructures. Aiming at evaluating the influence of holding time and microstructural features on strength and ductility, tensile properties were measured for each steel at selected austempering times. The results obtained indicate that it is possible to adjust holding time in order to obtain the best strength/ductility combination at determined austempering temperature. Moreover, it has been shown that the mechanical stability of retained austenite is the key factor in controlling tensile performance. Short austempering times result in low carbon enrichment of the austenite (low stability) and promote higher ultimate tensile strength and lower ductility. For longer austempering times, steels present a slight decrease in ultimate tensile strength but a marked increase in ductility. This work shows that it is possible to obtain cast steels with ultimate tensile strength of 1682 MPa, yield strength of 1493 MPa and total elongation of 12.5% by means of bainitic reaction. This strength/ductility combination and others reported in this study are remarkable for cast steels. [ABSTRACT FROM AUTHOR]

Plastic deformation and damage evolution in low-carbon cast steel containing non-metallic inclusions are analyzed experimentally and numerically. The cast steel was subjected to the heat treatment: normalizing, oil quenching and tempering. Tests were carried out at hydrostatic pressure of 500 MPa and 1 000 MPa. In the tensile test the tensile strength, elongation and reduction of area were examined. Fractography of the specimens was carried out to observe fracture mechanisms. The finite elements method has been used for modelling of deformation of the specimens. The computer simulation was performed using ABAQUS system. The computed output was compared with experimental results. [ABSTRACT FROM AUTHOR]

In this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite. [ABSTRACT FROM AUTHOR]

The results of tests and examinations of the microstructure and mechanical properties of cast steel used for large-size slag ladles are presented. Castings of this type (especially large-size ladles with a capacity of up to 16 m3) operate under very demanding conditions resulting from the repeated cycles of filling and emptying the ladle with liquid slag at a temperature exceeding even 1600°C. The changes in operating temperature cause faster degradation and wear of slag ladle castings, mainly due to thermal fatigue. The tests carried out on samples taken from different parts/areas of the ladle (flange, bottom and half-height) showed significant differences in the microstructure of the flange and bottom part as compared to the microstructure obtained at half-height of the ladle wall. The flange and bottom were characterized by a ferritic-pearlitic microstructure, while the microstructure at the ladle half-height consisted of a ferritic matrix, cementite and graphite precipitates. Changes in microstructure affected the mechanical properties. Based on the test results it was found that both the flange and the bottom of the ladle had higher mechanical properties, i.e. UTS, YS, hardness, and impact energy than the centre of the ladle wall. Fractography showed the mixed character of fractures with the predominance of brittle fracture. Microporosity and clusters of non-metallic inclusions were also found in the fractures of samples characterized by low properties. [ABSTRACT FROM AUTHOR]

The results of microstructure examinations and UTS, YS, El, RA carried out on low-carbon cast steel containing 0.15% C. The tests were carried out on specimens cut out from samples cast on a large-size casting and from samples cast in separate foundry moulds. It has been shown that significant differences in grain size observed in the material of the separately cast samples and cast-on samples occur only in the as-cast. In the as-cast state, in materials from different tests, both pearlite percent content in the structure and mean true interlamellar spacing remain unchanged. On the other hand, these parameters undergo significant changes in the materials after heat treatment. The mechanical properties (after normalization) of the cast-on sample of the tested cast steel were slightly inferior to the values obtained for the sample cast in a separate foundry mould. The microscopic examinations of the fracture micro-relief carried out by SEM showed the presence of numerous, small non-metallic inclusions, composed mainly of oxide-sulphides containing Mn, S, Al, Ca and O, occurring individually and in clusters. [ABSTRACT FROM AUTHOR]

In this paper a plastic deformation and a damage evolution in low-carbon cast steel containing non-metallic inclusions are analysed experimentally and numerically. Two microstructures of the cast steel have been obtained after appropriate heat treatment. Tensile tests of smooth specimens and axisymmetric notched specimens have been performed. The notched specimens have the notch radii: 1 mm, 3 mm and 7 mm. Fractography of the specimens was carried out to observe fracture mechanisms. The mechanism depended on the stress state in the notched specimens. The fractography showed the existence of two fracture mechanisms: ductile failure and by shear. The process of the voids growth formed on the non-metallic inclusions was the process which included in the explanation of the damage mechanism. Modelling of deformation of the specimens has been used with the model suggested by Gurson, Tvergaard and Needleman. The model is implemented in the Abaqus finite element program. The computer simulation was performed using ABAQUS system. The computed output was compared with the experimental results obtained for specimens of the same shape. [ABSTRACT FROM AUTHOR]

Ablation casting is a relatively new casting technique which can improve the mechanical properties of castings. In this paper, the microstructure and mechanical properties of plain carbon steel castings produced by conventional casting and ablation casting techniques were compared. It was found that ablation increased the ultimate strength from 638 to 1094 MPa and tensile elongation increased from approximately 13 to 16% as a result of severe microstructural changes from ferrite and pearlite to acicular ferrite, bainite, and martensite. Ablation increased the core hardness of the casting from 182 to 467 HB and the surface hardness from 205 to 508 HB. [ABSTRACT FROM AUTHOR]

The paper presents the research results concerning the chromium-nickel-molybdenum duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade. The aim of studies was the description of the influence of hyperquenching temperature Tp i.e. 1100, 1125 and 1150? on microstructure and mainly mechanical properties i.e. tensile strength UTS, yield strength YS, hardness HB, elongation EL and impact energy KV of duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade. The range of studies included ten melts which were conducted in foundry GZUT S.A. Based on the obtained results was confirmed that application of hyperquenching process guarantees the elimination of brittle s phase in the microstructure of studied duplex cast steel. Moreover on the basis of conducted statistical analysis of the researches results is concluded that with the decrease in hyperquenching temperature increases ductility and amount of austenite, while decreases strength and amount of ferrite in studied duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade. [ABSTRACT FROM AUTHOR]

High-silicon cast steels and proper heat treatment cycles were designed in order to obtain carbide-free bainitic microstructures. The design process allowed to obtain the desired microstructures after heat treatment cycles compatible with industrial practices and using low amounts of inexpensive alloying elements. The different chemical compositions and austempering temperatures tested resulted in ultra-high-strength steels showing remarkably total elongations. The obtained tensile properties satisfy the minimum requirements specified for AHSS in ASTM A1088 standard, and also the requirements for high-strength cast steels stated in ASTM A148. Moreover, many microstructures developed in this work reach the tensile performance of the very expensive maraging steels. [ABSTRACT FROM AUTHOR]

It is proposed to use a new submersible nozzle with eccentric apertures in order to improve continuously-cast slab quality. Calculations show that up to 38% of the heat of steel overheating is removed in the upper part of the crystallizer. The number of equiaxed crystals increases by several factors with an increase in crystallization rate. Pilot plant approval of advanced continuous casting of low-carbon and low-alloy steels makes it possible to improve hot rolled metal strength and toughness. Forecasting low-carbon steel sheet ultimate strength and relative elongation is conducted using known experimental equations. Rolled steel quality is evaluated from slabs selected from eight melts. The slab sulfur content obtained using a nozzle with eccentric apertures is somewhat higher than in slabs cast through existing nozzles. [ABSTRACT FROM AUTHOR]

Austempered ductile irons exhibit an interesting combination of properties such as low cost, elevated strength, fatigue and wear resistance. This research presents the results of tribo-fatigue behavior of austempered ductile cast iron MoNiCa and gives a comparison with standard grades of steel and cast iron. Due to the possibility to combine the castability of cast iron and toughness of steel in one material, new structural material MoNiCa attracted attention of industry and science because of economic benefits and high performance at the different application areas. After successful former experiments the main directions of further development of research for solving relevant practical wear and fatigue problems in rail-wheel system were framed. The complex experimental studies have demonstrated that MoNiCa is consistent with heat treated steels including the rail steels: required tensile strength of rail steel ranges from 1180 MPa to 1280 MPa when rolling surface hardness have to be from 38 HRC to 44 HRC whereas new structural material showed higher tensile strength up to 1400 MPa and slightly higher hardness up to 50 HRC. Herewith the workability of frictional couple cast iron MoNiCa/steel 20MnCr5G exceeds work performance of steel/steel system by 14 %. Future prospect of this study is to compose mechanical-mathematical model of rail-wheel system, to analyze it under three-dimensional loading, and to execute the field tests of rails under operating conditions. [ABSTRACT FROM AUTHOR]

The effect of austenitizing temperatures at 850, 880, 910, 940, 970 and 1000 °C, respectively, and tempering at 250 °C on the microstructure, mechanical properties, strengthening and toughening mechanism, and wear behavior of Si-Mn-Mo cast steel containing 0.45%C-2.0%Si-1.0%Mn-0.3%Mo-0.8%Cr-0.004%B were systematically investigated. The results indicated that the microstructure of water quenching Si-Mn-Mo cast steel was mainly composed of lenticular martensite, martensite/austenite, bainitic ferrite and retained austenite. After tempering, the homogeneity of the microstructure improved. As the austenitizing temperature increased, the hardness of the steel increased first, and then it remained almost constant, the impact toughness decreased significantly, and the wear loss decreased first and then increased. Under low wear load, the steel austenitizing at 910 °C had excellent wear resistance before and after tempering. Under high wear load, after tempering, the steel austenitizing at 850 °C had the optimum wear resistance. The wear mechanisms were mainly abrasive wear, oxidation wear and adhesive wear. [ABSTRACT FROM AUTHOR]

The cooling rate of casting has a significant effect on microstructure and mechanical properties of castings. The 9Cr-1.5Mo-1Co cast steel, referred to as CB2, is one of the most promising alloys for various cast components to be used under ultrasupercritical conditions. In this study, HRTEM, SEM, and XRD methods were used for qualitative and quantitative analyses of contents, phases, and sizes of the inclusions and precipitates, as well as microstructure observation of the tempered martensitic steel at different cooling rates. Traditional tensile tests were conducted to characterize the material mechanical properties. Results show that the size of the boron nitride and precipitate, the width of the martensite lath and the content of the δ-ferrite are reduced as the cooling rate increases from 5-8 °C·min-1 (CB2-S steel) to 50-60 °C·min-1 (CB2-F steel). The precipitates are mainly composed of M23C6 and a small amount of M3C. The average diameters of the M23C6 precipitates in CB2-F and CB2-S are 202 nm and 209 nm, respectively. The inclusions are mainly composed of BN, Al2O3 and MnO2, and the inclusion ratios are 0.1969% for the CB2-F and 0.06556% for CB2-S steel. The average martensite lath widths of CB2-F and CB2-S steels are 289 nm and 301 nm, respectively. Furthermore, the M3C having a diameter of about 150 nm and a thickness of 20 nm is observed in the δ-ferrite of the tempered CB2-S steel. The presence of the δ-ferrite reduces the precipitation strengthening and dislocation density in CB2-S steel. In addition, the lower cooling rate stabilizes the δ-ferrite structure at room temperature. [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of an ultrahigh-carbon steel modified with amorphous ferrosilicon with a low melting point are studied. The methods of x-ray diffraction, optical and scanning electron microscopy are used to study the effect of the amorphous modifier on the structure of eutectic ledeburite in the cast steel. Tests for tensile strength and impact toughness are conducted. It is shown that the mechanical properties increase as a result of the modification without subsequent heat treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Small La additions refines the crystal microstructure of Fe-Mn-Al-C steel. • The Al 2 O 3 based oxide scale prevents the further diffusion of oxygen into the steel. • The cast Fe-Mn-Al-C steels have high ultimate tensile strength and oxidation resistance. An influence of La additions on microstructure, mechanical properties and high temperature oxidation of Fe-20Mn-12Al-1C (wt %) triplex steels has been investigated. It was shown that the melt modification with small lanthanum additions (0.1 wt %), not only purifies melt and refines the ferrite grains during crystallization, but also increases the oxidation resistance of steel. The uniform dense oxide film formation mainly consisted of Al 2 O 3 on the alloy/oxide scale interface, which better prevents the further diffusion of oxygen into the steel and protects it. Cast steels Fe-20Mn-12Al-1C have ultimate tensile strength (UTS) of >1 GPa and high oxidation resistance at the same time. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Applied Materials Engineering is the property of Lukasiewicz Research Network, Krakow Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The alloy steel 42CrMo and the cast Ni-based superalloy K418 were successfully joined by inertia friction welding. The effects of the initial flywheel kinetic energy on the microstructure and mechanical properties of the joints were investigated. The results showed that inertia friction welding is a rapid and efficient way to achieve metallurgical bonding between 42CrMo and K418. Intermetallic compounds Fe 0.64 Ni 0.36 , Ni–Fe–Cr, Ni 3 (Al, Ti) and MC-type carbides like NbC and TiC were observed at the interface containing a diffusion layer because of element diffusion. Elemental distribution analysis indicated that Fe and Ni were intermixed at the interface. The maximum tensile strength of the dissimilar 42CrMo/K418 joint was 772.19 MPa. Tensile fracture was identified to have occurred on the K418 side with brittle fracture features at an initial flywheel kinetic energy of 50.6 kJ. The origin and expansion of the cracks were mainly attributed to the MC carbides. • 42CrMo and K418 were successfully joined by inertia friction welding. • Phase composition and element transition layer identified at an initial flywheel kinetic energy of 50.6 kJ. • Brittle carbides formed at the interface were the source of crack formation. [ABSTRACT FROM AUTHOR]

The intention of this paper is to investigate the degradation of mechanical properties of corroded water pipes after long service. The mechanical tests are conducted to quantify the degradation of mechanical properties of corroded water pipes made of cast iron and steel. Various techniques (e.g. SEM, EDS, XRD, 3D scanning) are used for corrosion and material analyses at both micro and macro levels. It is found that there is a significant reduction of mechanical properties of the corroded pipes due to the change of microstructure, and that the reduction of modulus of rupture is more sensitive to the average corrosion pit depth while the reduction of tensile strength is more sensitive to the maximum corrosion pit depth. The findings presented in the paper can contribute to the body of knowledge of corrosion of metal water pipes for their failure assessment and service life prediction after long service. [ABSTRACT FROM AUTHOR]

This paper presents influence of rare earth metals (REM) on the mechanical properties, microstructure and morphology of non metallic inclusions as well as the cracking mechanism of G17CrMo5-5 high temperature cast steel. The research has been performed on successive industrial melts. It was found that non metallic inclusions the cracking mechanism of Charpy specimens and the impact strength were all changed. The following properties were tested: mechanical properties (Rm, Re), plastic properties (A, Z), impact strength (SCI) and the KJC stress intensity factor.

In this study, Taguchi method is used to find out the effect of micro alloying elements like vanadium, niobium and titanium on the hardness and tensile strength of the normalized cast steel. Based on this method, plan of experiments were made by using orthogonal arrays to acquire the data on hardness and tensile strength. The signal to noise ratio and analysis of variance (ANOVA) are used to investigate the effect of these micro alloying elements on these two mechanical properties of the micro alloyed normalized cast steel. The results indicated that in the micro alloyed normalized cast steel both these properties increases when compared to non-micro-alloyed normalized cast steel. The effect of niobium addition was found to be significantly higher to obtain higher hardness and tensile strength when compared to other micro alloying elements. The maximum hardness of 200HV and the maximum tensile strength of 780 N/mm2 were obtained in 0.05%Nb addition micro alloyed normalized cast steel. Micro-alloyed with niobium normalized cast steel have the finest and uniform microstructure and fine pearlite colonies distributed uniformly in the ferrite. The optimum condition to obtain higher hardness and tensile strength were determined. The results were verified with experiments. [ABSTRACT FROM AUTHOR]

A possibility to control the strength, hardness and ductility of the L35HM low-alloy structural cast steel by the applied tempering temperature is discussed in the paper. Tests were carried out on samples taken from the two randomly selected industrial melts. Heat treatment of the cast samples included quenching at 900 °C, cooling in an aqueous solution of polymer and tempering at 600 and 650 °C. The obtained results showed that the difference in the tempering temperature equal to 50 °C can cause the difference of 121 MPa in the values of UTS and of 153 MPa in the values of 0.2%YS. For both melts tempered at 600 °C, the average values of UTS and 0.2%YS were equal to 995 MPa and 933 MPa, respectively. The values of EL and RA did not show any significant differences. Attention was drawn to large differences in strength and hardness observed between the melts tempered at 600 and 650 °C. Despite differences in the mechanical properties of the examined cast steel, the obtained results were superior to those specified by the standard. [ABSTRACT FROM AUTHOR]

Application of cast steels instead of hot forged or rolled ones will significantly decrease manufacturing costs and the final product price. However, low levels of mechanical properties in cast steels, especially ductility, can slow down the substitution of forged and rolled steels with the cast. In the present work, the authors study the effect of 0.01-0.12 wt% vanadium additions on the microstructure and mechanical properties of 0.25 wt% C cast steels. The yield stress, ultimate tensile strength, and elongation to failure in the studied cast steels are 730-750 MPa, 955-1002 MPa, and 12.3-21.5%, respectively, which correspond to those in hot forged and rolled steels with similar compositions. So, high property values in the 0.25 wt% C cast steels are shown here for the first time. The simultaneous increase in strength and ductility with an increase in V content follow a decrease in pearlite fraction, interlamellar spacing, and average pearlite area size; an increase in amount of degenerated pearlite; an increase in V-rich particle volume fraction and number density in ferrite and pearlite; the occurrence of interphase precipitation (in 0.12 wt% V steel), and an increase in dislocation density in ferrite and pearlite. [ABSTRACT FROM AUTHOR]

Microstructure transformations occur in the Manaurite XM cast steel tubes during long-term operation in the reformer furnace were revealed and described. The relationship between mechanical properties, an increase of internal diameter of the tube and microstructure degradation is discussed. Static tensile test was performed on two types of samples with different shapes. It has been shown differences in the results of tests and an explanation of this phenomenon. [ABSTRACT FROM AUTHOR]

The edge-to-edge matching model was used to identify TiB 2 as a potential grain refiner to refine the high temperature δ-ferrite in low carbon steels. To effectively introduce the grain refiner, Al–5Ti–B master alloy (MA) was used to add TiB 2 particles into an A517 steel. However, there was no grain refinement in the as-cast A517 steel, attributed to the decomposition of TiB 2 particles in the molten A517 steel, into Ti and B. As a result, BN particles formed on the pre-existing Al 2 O 3 particles were detected within prior austenite grains. Nevertheless, there was significant grain refinement after reheating the A517 ingots to 1150 °C, isothermally holding for 2 h and air cooling. The austenite grain size of the reheated A517 steel was decreased from 318 ± 70 μm to 38 ± 4 μm using 0.1 wt% Al–5Ti–B MA. Grain refinement was caused by Ti-containing nanometre-sized precipitates along prior austenite grain boundaries inhibiting the grain growth. The grain refinement improved the strength and ductility of ingots after reheating and improved workability for the production of hot worked products. • TiB 2 has been identified as an effective grain refiner for low-carbon low-alloy steels. • Inoculation of the A517 steel with Al–5Ti–B master alloy could significantly refine the cast A517 steel after reheating. • With 0.05 wt% Al–5Ti–B master alloy addition, A517 steel showed the optimal strength-ductility trade-off. [ABSTRACT FROM AUTHOR]

The paper presents the results of tests on the spheroidising treatment of vanadium carbides VC done with magnesium master alloy and RE. The conducted metallographic studies have shown that introducing the magnesium master alloy to an Fe–C–V system of eutectic composition causes the crystallisation of spheroidal carbides. The content of these carbides is about 5.6%, representing 33% of all the crystallised vanadium carbides. Adding RE to the base alloy melt caused 31% of the vanadium carbides crystallise as dendrites. Testing of mechanical properties has proved that the spheroidising treatment of VC carbides in high-vanadium cast iron increases the tensile strength by about 60% and elongation 14–21 times, depending on the type of the spheroidising agent used. Tribological studies have shown that high-vanadium cast iron with eutectic, dendritic and spheroidal carbides has the abrasive wear resistance more than twice as high as the abrasion-resistant cast steel. [ABSTRACT FROM AUTHOR]

The article presents the microstructure and mechanical properties of cast duplex stainless steel type 23Cr-5Mn-2Ni-3Mo. It has been shown that the structure of the tested cast steel is composed of ferrite enriched in Cr, Mo and Si, and austenite enriched in Mn and Ni. In the initial state, at the interface, precipitates rich in Cr and Mo were present. A high carbon content (0.08%C) in this cast steel indicates that probably those were complex carbides of the M23C6 type and/or σ phase. Studies have proved that the solution annealing conducted at 1060°C was not sufficient for their full dissolution, while at the solutioning temperature of 1150°C, the structure of the tested material was composed of ferrite and austenite. Partial replacement of Ni by two other austenite-forming elements, which are Mn and N, has ensured obtaining mechanical properties comparable to cast duplex 24Cr-5Ni-3Mo steel of the second generation. Basing on the results of static tensile test, a twice higher yield strength was proved to be obtained, compared to the cast austenitic 18Cr-9Ni and 19Cr-11Ni-2Mo steel commonly used in the foundry industry. In addition to the high yield strength (YS = 547 ÷ 572 MPa), the tested cast steel was characterized by the following mechanical properties: UTS = 731 ÷ 750 MPa, EL = 21 ÷ 29.5%, R.A. = 43 ÷ 52%, hardness 256 ÷ 266 HB. Fractures formed in mechanical tests showed ductile-brittle character. [ABSTRACT FROM AUTHOR]