جستجوی مقالات مرتبط با کلیدواژه "low alloy steel" در نشریات گروه "مواد و متالورژی"

Third-generation advanced high-strength steels serve as advanced engineering materials in various industries, including land, air, rail, and maritime transportation, with expanding applications. In the present study, a sample of low-alloy steel with medium carbon content (0.529 wt%) and high silicon content (1.670 wt%) was selected and subjected to one-step quenching and partitioning heat treatment at temperatures of 140 and 180 oC for different partitioning times (isothermal holding for redistribution of carbon element between initial martnsite and untransformed austenite). Phase transformations and microstructural investigations were conducted using dilatometry, laser microscopy, and Electron Backscatter Diffraction (EBSD) analysis. Dilatometry results indicated that the formation of initial martensite occurs at a temperature of 275 oC, and during a holding time of 3600 s, only carbon partitioning into retained austenite takes place at temperatures of 140 and 180 oC, yet martensite formation occurs during the final cooling. Additionally, considering the changes in specimen width during isothermal holding, tempering of the initial martensite can be anticipated. Microstructural examinations also confirmed the formation of microphasic structures, including initial martensite, retained austenite, and final martensite.

In this research, the objective was to investigate the stabilized retained austenite in the microstructure resulting from the Q&P heat treatment since the primary goal in Q&P is to create a microstructure consists of stabilized retained austenite and martensite. For this purpose, a low-alloy steel with 0.4wt. % carbon was treated by quench and partitioning (Q&P) process. The Q&P was conducted at different quench temperatures to obtain a considerable amount of retained austenite, while partitioning temperature and time were kept constant. Through analysis of the XRD profiles, volume percent, carbon concentration, and lattice parameters of retained austenite and martensite were calculated. At quench temperature equal to 160°C, 12vol.% austenite was stabilized to the room temperature, which was the highest amount achieved. The microstructural observations carried out on selected samples, revealed that retained austenite has a nanoscale particle size, about 200nm. Distinguishing retained austenite in the SEM micrographs became possible by utilizing SE2 signals via the difference in phases contrast. Two types of morphology, film-like and blocky type, were identified by means of TEM and TKD and a schematic model was proposed in order to explain these morphologies

In the present study, the microstructure and mechanical properties of the dissimilar welding between ASTM A335 low alloy steel and ER309L austenitic stainless steel were investigated using the gas tungsten arc welding process. The welding of dissimilar materials between ASTM A335 low alloy steel and ER309L austenitic stainless steel was found to have a significant effect on the microstructure when the filler metal of ER309L was used. This research also studied the effect of carbon migration from the heat-affected zone (HAZ) to the melted zone in the interface between A335 low alloy steel and 309L filler metal using microstructure analysis and Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) Line Scan Technique. The results showed that the solidification of 309L as a primary ferrite exhibited a skeletal ferrite morphology and the solidification of ferritic-austenitic (FA) type. Moreover, the results of EDS provided evidence showing carbon migration from the low chromium side to the weld metal which had a higher chromium content and a tiny martensitic zone occurred in the melt boundary with a high hardness value. In the tensile test, all specimens were broken in the HAZ of A335 low alloy base metal with a ductile fracture and the welded specimens also showed the ductile fracture in the impact test.

This paper was aimed to address the modeling and optimization of factors affecting the corrosive wear of low alloy and high carbon chromium steel balls. Response surface methodology, central composite design (CCD) was employed to assess the main and interactive effects of the parameters and also to model and minimize the corrosive wear of the steels. The second-order polynomial regression model was proposed for relationship between the corrosion rates and relevant investigated parameters. Model fitted to results indicated that the linear effects of all of factors, interactive effect of pH and grinding time and the quadratic effects of pH and balls charge weight, were statistically significant in corrosive wear of low alloy steel balls. The significant parameters in the corrosive wear of high carbon chromium steel balls were the linear effects of all factors, the interactions effect of solid concentration, mill speed, mill throughout, grinding time, and the quadratic effects of pH and solid content. Also, the results showed that within the range of parameters studied, the corrosion rate of 78.38 and 40.76 could be obtained for low alloy and high carbon chromium steel balls, respectively.

This paper presents an experimental and theoretical investigation of the causes of corrosion of stack in a cement plant. In this paper, information related to metallic stack failures are given in the form of a case study in Neka Cement Plant, Mazandaran, Iran. Heavy corrosion attacks were observed on the samples of stack. The failure can be caused by one or more modes such as overheating, stress corrosion cracking (SCC), hydrogen embrittlement, creep, flame impingement, sulfide attack, weld attack, dew point corrosion, etc. Theoretical calculations and experimental observations revealed that, the corrosion had taken place due to the condensation of acidic flue gases in the interior of stack. Also, the chemical analysis of the corrosion deposits and condensates confirmed the presence of highly acidic environment consisting of mostly sulfate ions.