An Experimental Artificial Neural Network Model:Investigating and Predicting Effects of Quenching Process on Residual Stresses of AISI 1035 Steel Alloy

The present study establishes a new estimation model using an artificial neural network(ANN) to predict the mechanical properties of the AISI 1035 alloy.The experiments were designed based on the L16 orthogonal array of the Taguchi method.A proposed numerical model for predicting the correlation of mechanical properties was supplemented with experimental data.The quenching process was conducted using a cooling medium called “nanofluids”.Nanoparticles were dissolved in a liquid phase at various concentrations(0.5%,1%,2.5%,and 5% vf) to prepare the nanofluids.Experimental investigations were done to assess the impact of temperature,base fluid,volume fraction,and soaking time on the mechanical properties.The outcomes showed that all conditions led to a noticeable improvement in the alloy's hardness which reached 100%,the grain size was refined about 80%,and unwanted residual stresses were removed from 50 to 150 MPa.Adding 5% of CuO nanoparticles to oil led to the best grain size refinement,while adding 2.5% of Al_(2)O_(3) nanoparticles to engine oil resulted in the greatest compressive residual stress.The experimental variables were used as the input data for the established numerical ANN model,and the mechanical properties were the output.Upwards of 99% of the training network's correlations seemed to be positive.The estimated result,nevertheless,matched the experimental dataset exactly.Thus,the ANN model is an effective tool for reflecting the effects of quenching conditions on the mechanical properties of AISI 1035.

In situ observation of austenite grain growth behavior in the simulated coarse-grained heat-affected zone of Ti-microalloyed steels

The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.

Hot ductility behavior of V-N and V-Nb microalloyed steels

The hot ductility of V-N and V-Nb microalloyed steels was investigated on a Gleeble-1500 thermomechanical simulator, and the results were compared with those of V and Nb microalloyed steels. A ductility trough is found in both the steels in the temperature range of 700 to 1050℃. Compared to the V steel, the V-N steel has a wider and deeper ductility trough with the increase of N content, due to the in- creased precipitation of V（C, N） in the steel. Above 930℃, when 0.047wt% V is added to the 0.028wt% Nb-containing steel, the ductility becomes worse, owing to the rise of the onset dynamic recrystallization temperature. However, the ductility gets better at 800 to 930℃ be- cause of the coarsening of precipitates in austenite. With the improvement in ductility, the fracture mechanism is changed from intergranular to high ductile fracture in the temperature range of 800 to 1050℃.

Data-mining and atmospheric corrosion resistance evaluation of Sn-and Sb-additional low alloy steel based on big data technology

Machine-learning and big data are among the latest approaches in corrosion research.The biggest challenge in corrosion research is to accurately predict how materials will degrade in a given environment.Corrosion big data is the application of mathematical methods to huge amounts of data to find correlations and infer probabilities.It is possible to use corrosion big data method to distinguish the influence of the minimal changes of alloying elements and small differences in microstructure on corrosion resistance of low alloy steels.In this research,corrosion big data evaluation methods and machine learning were used to study the effect of Sb and Sn,as well as environmental factors on the corrosion behavior of low alloy steels.Results depict corrosion big data method can accurately identify the influence of various factors on corrosion resistance of low alloy and is an effective and promising way in corrosion research.

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

To obtain high-quality dissimilar weld joints, the processes of metal inert gas （MIG） welding and tungsten inert gas （TIG） welding for duplex stainless steel （DSS） and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy （SEM）; the chemical compositions in different zones were detected by en- ergy-dispersive spectroscopy （EDS）; the mechanical properties were measured by microhardness test, tensile test, and impact test; the corro- sion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG weld- ing. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaC1 solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints pro- duced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS $31803 duplex stainless steel and low alloy steel in practical application.

Influence of mill scale and rust layer on the corrosion resistance of low-alloy steel in simulated concrete pore solution

Electrochemical impedance spectroscopy, cyclic potentiodynamic polarization measurements, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy were used to investigate the influence of mill scale and rust layer on the passivation capability and chloride-induced corrosion behaviors of conventional low-carbon（LC） steel and low-alloy（LA） steel in simulated concrete pore solution. The results show that mill scale exerts different influences on the corrosion resistance of both steels at various electrochemical stages. We propose that the high long-term corrosion resistance of LA steel is mainly achieved through the synergistic effect of a gradually formed compact, adherent and well-distributed Cr-enriched inner rust layer and the physical barrier protection effect of mill scale.

Study on non-metallic inclusions in Al killed high strength alloy steel refined by high basicity and high Al_2O_3 content slag

Laboratory and industrial studies were carried out to investigate non-metallic inclusions in high strength alloy steel refined by high basicity and high Al_2O_3 slag.It was found that the steel/slag reaction time largely affected non-metallic inclusions.With the reaction time increased from 30 min to 90 min in laboratory study,MgO-Al_2O_3 spinels were gradually changed into CaO-MgO-Al_2O_3 system inclusions surrounded by softer CaO-Al_2O_3 surface layers.By using high basicity slag which contained as much as 41%Al_2O_3 in the laboratory study,ratio of low melting temperature CaO-MgO-Al_2O_3 system inclusions was remarkably increased to above 80%.In the industrial experiment,during the secondary refining,the inclusions changed in order of 'Al_2O_3→MgO-Al_2O_3→CaO-MgO-Al_2O_3'.Through the LF and RH refining,most inclusions could be transferred to lower melting temperature CaO-Al_2O_3 and CaO-MgO-Al_2O_3 system inclusions.

Recent progress in third-generation low alloy steels developed under M^3 microstructure control

During the past thirty years, two generations of low alloy steels(ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy steels is expected to achieve high strength and improved ductility and toughness, while satisfying the new demands for weight reduction, greenness, and safety. This paper reviews recent progress in the development of third-generation low alloy steels with an M^3 microstructure, namely, microstructures with multi-phase, meta-stable austenite, and multi-scale precipitates. The review summarizes the alloy designs and processing routes of microstructure control, and the mechanical properties of the alloys.The stabilization of retained austenite in low alloy steels is especially emphasized. Multi-scale nano-precipitates, including carbides of microalloying elements and Cu-rich precipitates obtained in third-generation low alloy steels, are then introduced. The structure–property relationships of third-generation alloys are also discussed. Finally, the promises and challenges to future applications are explored.

Microstructure and mechanical properties of high-strength low alloy steel by wire and arc additive manufacturing

A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.

Characterization of Rust Layer Formed on Low Alloy Steel Exposed in Marine Atmosphere

The iron rust phases formed on low alloy steels containing different quantities of Cr element have been characterized using EPMA, Raman spectroscopy, TEM, optical microscopy etc. The ion selective properties of synthesized rust films with the same phase constituent as the atmospheric corrosion products were investigated using self-made apparatus. The results showed that corrosion loss of steels exposed in marine atmosphere decreased rapidly as the Cr content of the steel was increased. Cr-containing steels were covered by a uniform compacted rust layer composed of fine particles with an average diameter of several nanometers. Inner rust layer of Cr-containing steel (2 mass fraction) was composed of a-CrxFe1-xOOH, with Cr content of about 5 mass fraction. Such rust layer showed cation selective property, and could depress the penetration of Cl- to contact substrate steel directly.

ISOCHRONOUS STRESS-STRAIN CURVES OF LOW ALLOY STEEL CROSS-WELD-SPECIMEN AT HIGH TEMPERATURE

In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.

Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.

A method to study interface diffusion of arsenic into a Nb-Ti microalloyed low carbon steel

A novel diffusion couple method was used to investigate the interface diffusion of arsenic into a Nb-Ti microalloyed low carbon steel and its effects on phase transformation at the interface. It is discovered that the content of arsenic has great effect on grain growth and phase transformation at high temperature. When the arsenic content is no more than lwt%, there is no obvious grain growth and no obvious ferrite transitional region formed at the diffusion interface. However, when the arsenic content is no less than 5wt%, the grain grows very rapidly. In addition, the arsenic-enriched ferrite transitional layer forms at the diffusion interface in the hot-rolling process, which results from a slower diffusion rate of arsenic atoms than that of carbon in ferrite.

Performance of the Aluminide Coating of SomeLow Alloy Steels

Two low alloy steels 0.5Cr-0.5Mo-0.25V and H85 were pack-aluminized at 900°for 4 h by using Fe-Al powder mixture containing 48% Fe, 20.6% Al- 29.4% Al2O3 and 2% NH4Cl by weight. The microhardness and oxidation resistance at 900℃ of the aluminide coatings were studied. It was found that pack-aluminizing improves the microhardness of the 0.5Cro.5Mo-0.25V steel while it reduces the microhardness of the H85 steel. Pack aluminizing highly improves the oxidation resistance after 20h exposure at 900℃ in air for the investigated steels.

Metal magnetic memory signals from surface of low-carbon steel and low-carbon alloyed steel

In order to investigate the regularity of metal magnetic signals of ferromagnetic materials under the effect of applied load, the static tensile test of Q235 steel and 18CrNiWA steel plate specimens were conducted and metal magnetic memory signals of specimens were measured during the test process. The influencing factors of metal magnetic memory signals and the relationship between axial applied load and signals were analyzed. The fracture and microstructure of the specimens were observed. The results show that the magnetic signals corresponding to the measured points change linearly approximately with increasing axial load. The microstructure of Q235 steel is ferrite and perlite, whereas that of 18CrNiWA steel is bainite and low-carbon martensite. The fracture of these two kinds of specimens is ductile rupture; carbon content of specimen materials and dislocation glide give much contribution to the characteristics of magnetic curves.

Grain boundary segregation of minor arsenic and nitrogen at elevated temperatures in a microalloyed steel

Auger electron spectroscopy （AES） was used to investigate the grain boundary segregation of arsenic and nitrogen in a kind of microalloyed steel produced by a compact strip production （CSP） technology at 950 to 1100℃, which are similar to the hot working temperature of the steel on a CSP production line. It was discovered that arsenic segregated on grain boundaries when the steel was annealed at 950℃ for 2 h. When the annealing temperature increased to 1100℃, arsenic was also found to have segregated on grain boundaries in the early annealing stage, for instance, within the first 5 min annealing time. However, if the holding time of the steel at this temperature increased to 2 h, arsenic diffused away from grain boundaries into the matrix again. Nitrogen was not found to have segregated on grain boundaries when the steel was annealed at a relatively low temperature, such as 950℃. But when the annealing temperature increased to 1100℃, nitrogen was detected to have segregated at grain boundaries in the steel.

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO_2–O_2–H_2S–SO_2 wet–dry corrosion environment of cargo oil tankers

The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2 wet–dry corrosion environment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance(Rct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.

Numerical simulation of residual stress and deformation for submerged arc welding of Q690D high strength low alloy steel thick plate

The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles.The simulation results show that as the welding heat input increases,the peak temperature during the welding process is higher,and the residual stress increases,they are all between 330–340 MPa,and the residual stress is concentrated in the area near the weld.The hole-drilling method is used to measure the actual welding residual stress,and the measured data is in good agreement with the simulated value.The type of post-welding deformation is angular deformation,and as the welding heat input increases,the maximum deformation also increases.It shows smaller residual stress and deformation when the groove angle is 40°under the same heat input.In engineering applications,under the premise of guaranteeing welding quality,smaller heat input and 40°groove angle should be used.

AN EXPERT SYSTEM FOR COMPUTER AIDED ALLOY STEEL DESIGN—ASPRES

An alloy steel pattern recognition expert system,ASPRES,has been established for the purpose of computer aided optimal design of alloy steel in compositions and process pa- rameters,Pattern recognition techniques are used to abstract inner relationship between mechanical properties and process variables.The ASPRES uses 2-dimensional graph as visual knowledge to represent domain expertise of specific object.Forward and back- ward chaining can be utilized by researcher in predicting sample performances or giving helpful suggestions about the chemical compositions and process parameters according to desired properties.

EFFECT OF THE CONTROLLED ROLLING CONTROLLED COOLING ON STRENGTH AND DUCTILITY OF THE BAINITE MICRO ALLOYED ENGINEERING STEEL

The continuous cooling transformation of hot deformation austenite austenite of test steel and the effect of different processing schedules of controlled rolling and controlled cooling on the strength and ductility have been studied. The theory and the experiment base are presented for controlled rolling and controlled cooling of the SBL micro alloyed engineering steel.