International Journal of iron and steel society of Iran
Volume:18 Issue: 2, Summer and Autumn 2021

Mould powders are mainly composed of SiO2, CaO, alkaline, and alkaline-earth oxides along with traces of fluoride and carbon. Their crucial responsibility is lubricating the surface between mould walls and the solidified steel crust. The viscosity and crystallization of these powders are influenced by Fluorine. However, the emission of evaporating materials leads to environmental pollution. Therefore, this research aims to decrease the amount of CaF2 and the effect of substitute compositions on the viscosity and crystallization of mould powders. Hence 12 powder samples are prepared having employed Portland Cement Clinker and other as the main composition. To compare the laboratory samples with the molten reference powder, groove viscometer tests were conducted. The crystalline behavior of the samples was examined employing XRD, SEM and STA analyses. Results showed some low-CaF2 samples had similar viscosity as molten reference powder (MRP). XRD analysis results presented crystalline phases of gehlenite, cuspidine, akermanite, nepheline and Mn3O4 .Likewise, the crystalline phases of B2SiO5, Na2ZnSiO4 and perovskite (CaTiO3) were examined after adding B2O3, ZnO and TiO2. SEM analysis results showed crystals in the glass matrix, which can optimize the viscosity in mould powders. TGA analysis results revealed the reduction on ignition loss of a low-CaF2 sample compared to the reference powder. Moreover, DTA analysis revealed the crystallization and melting temperatures of the same low-CaF2 sample, similar to that of the reference powder. Finally, three low-CaF2 samples containing CaF2, Li2O, TiO2, ZnO and B2O3 were nominated as the apt substitutions for reference powder in laboratory scale.

In the form of a technical note, this article deals with the production of sponge iron products in the world and compares it with Iran in 2020. Predicts the future of sponge iron products in the world, especially in Iran and examines the strengths and weaknesses ahead using the available figures. According to development plans, Iran is expected to be one of the world's top producers this year. India, Iran, Russia, Mexico and Saudi Arabia are the world's largest producers of sponge iron. Sponge iron is loaded cold, hot briquette and hot charge in an electric arc furnace. Last year, the world's sponge iron production was 104.4 million tons. 11.38 million tons of hot iron (HDRI) sponge iron are charged in arc furnaces. The production of hot briquettes (HBI) in the world last year was more than 9 million tons. Mobarakeh Steel Company (Isfahan-Iran) is the world's largest producer of sponge iron with a production of 7.25 million tons. The process of producing Iranian sponge iron (PERED) is expanding more and more.

In this research, AISI 4140 steel samples were normalized at 850 ºC for 60 min, then, they were kept at 720 ºC for 3 min and were directly transferred to a salt bath with temperature of 400 °C for 4 min and after that, the samples were quenched in water (25 °C). Finally, the triple-phased samples were tempered at 250, 450 and 650 ºC for 90 min. The microstructure and tensile properties were examined by a FE-SEM equipped with an EDS detector and a universal tensile test machine, respectively. Results showed that the microstructureکار سختی of sample tempered at 250 °C was upper bainite and martensite along with carbide particles resulted from the decomposition of martensite, while the microstructure of sample tempered at 450 °C was lower bainite and martensite along with carbide particles. Nevertheless, in the sample tempered at 650 °C, bainite and martensite phases were decomposed completely to carbide. In comparison with not-tempered sample, the sample tempered at 250 °C had higher yield strength, greater elongation and lower ultimate tensile strength. As the tempering temperature increased from 250 to 650 °C, the yield strength and ultimate tensile strength decreased while the elongation increased. Tensile test results of the tempered samples showed a two-stage work-hardening behavior. In both stages, with increasing the tempering temperature the strength coefficient (k) decreased. The work-hardening exponent (n) in the first stage decreased only for the samples tempered at higher than 250 °C, while in the second stage, it continuously decreased for all tempered samples.

This paper investigates the effects of 25Cr-35Ni and 35Cr-45Ni filler metals on the weldability, microstructure, and mechanical properties of 25Cr-35Ni heat-resistant steel. Alloy 25Cr-35Ni is known to have excellent high temperature properties, such as creep resistance and high temperature corrosion/oxidation resistance, making this grade an ideal option for demanding high temperature applications in oil, gas, and petrochemical industries. Gas tungsten arc welding is a routine welding practice for the repair and joining of components, made of heat resistant steels. Microstructure and mechanical properties of welded samples with 25Cr-35Ni and 35Cr-45Ni filler metals were studied using optical microscopy, electron microscopy, and tensile and hardness tests. Fractography of fracture surfaces was also conducted, using electron microscope. Results show that the microstructure in the heat affected zone area in both cases are largely affected by the heat input during melting. A noticeable carbide dissolution was observed in both cases. In neither of filler metals was there any indication of sigma phase formation in the weld, which is related to the high nickel content of filler metals. Results also showed that mechanical properties in both cases are controlled by heat affected zone.

Production companies currently face a significant environmental concern. The circular economy (CE) was raised due to those concerns. The CE is an economic system that aims to eliminate wastes by reusing them. This study aims to investigate the factors affecting the reverse supply chain in order to implement the CE in Mobarakeh Steel Company of Isfahan. Structured interviews were conducted with 13 managers and experts of the company. Among the factors in the literature, 16 factors were specifically identified as relevant to the company. We use the Delphi method in order to determine the importance and priority of the factors for the company. To analyze the data, in this research, the analytical-survey method was used and a combination of library and field research methods was used to collect information. By using these methods, we select 7 factors out of 16 that were very important for the company. They are environmental-oriented design, industrial ecology, redistribution, reuse, redesign, recycling, and reduction. We prioritize these factors using the fuzzy TOPSIS method based on 6 criteria: efficiency of steel resources, slag use, electricity consumption, water consumption, gas consumption, and SO2 emissions. The result shows that “Industrial ecology” has the 1st and “Reuse” has the 7th priority. We identify the relationships of these factors, with the help of a panel of experts and, we plot the relationships as an IDEF0 (Icam DEFinition for Function Modeling) model. This is the first attempt to configure the model of reverse supply chain factors in a steel company.

Alkaline bricks, especially magnesia refractory products containing spinel, are the most important refractory materials that are used in many refractory industries such as steel, cement and non-ferrous industries due to their special physical, chemical and mechanical properties. In this study, the effect of titania addition on the properties and microstructure of magnesium-alkali refractories without spin-band chromium was studied. After cooking the product samples at two temperatures of 1500 and 1600 °C, different physical and mechanical properties such as density, apparent porosity, cold compressive and flexural strength, load retardation and hot rupture modulus were evaluated according to ASTM standard. The results showed that with increasing titania up to 6% by weight after sintering at 1600 ° C compared to the reference sample without additive, density and apparent porosity due to the formation of spinel phases and especially magnesium -titanate increased and decreased, respectively. Also, cold compressive and flexural strength increase to 4% by weight with the addition of this material, and with further increase, cold compressive and flexural strength due to the increase in volume percentage of magnesium- titanate and magnesium aluminate-spinel phases decrease and increase, respectively. The results also show that by increasing the titania up to 6% by weight compared to the sample without additives, the modulus of hot rupture increases at 1000 and 1400 °C and on the delay under load by increasing the amount of titania to 2% by weight from temperature T0 =1570 ºC is added to 1620 ºC under load 2 Kg / Cm2.

Mill pellets are most used in cement, steel and copper industries and its role in crushing and production of materials and products with optimal grain size and as a mineral production agent in metal and non-metallic mineral processing industries including cement factories, stone mines Iron and copper mines are required. On the other hand, it is used to a limited extent in some defense industries and heavy metal mines. in this study, the factors affecting the failure of steel balls produced from continuous casting ingots with 70Cr2 material during the quenching process in water have been investigated. The samples are 2 destroyed balls and a healthy ball that the destroyed balls, during the production process and before being put into operation (some balls immediately after the quenching process and some others have failed after the tempering process. In order to investigate the causes of destruction, visual inspection, emission spectroscopy, metallography, hardness and scanning electron microscopy studies were performed along with EDS analysis. The high hardness of the sample is due to improper heat treatment and cracking during cooling and when hitting the bullets from the place of forging defects and below the surface in the place of grains, defects and impurities.

Roller tables, rollers, and pinch rolls are widely used in different industries ranging from rolling mills, sheet metal works, ceramic and tile production industries, etc. Their harsh working conditions, like heating furnaces with high temperatures, oxide debris, and ceramic materials, have been a matter of concern. High wear-resistant cast iron has always been a common material for making these tools. In the present study, motivated to use in the rollers of the rolling line, the production of cast iron-based matrix surface composite reinforced with tungsten carbide (WC), as a surface metal matrix composite (SMMC), using a centrifugal casting process was evaluated in detail. The microstructure of samples was characterized using optical microscopy (OM) and scanning electron microscopy equipped with energy dispersive X-Ray spectroscopy (SEM-EDX). The results indicated that a 3 mm thick composite layer was formed on the sample surface. The findings reveal that the formation of a composite structure on the surface can dramatically improve the wear resistance of cast iron; as a result, the weight loss of composite samples was decreased by 61% after a 1000 m sliding distance at 25 °C when compared with non-composite samples. Results suggest that the production of cast iron-based matrix surface composite reinforced with WC using centrifugal casting, as a feasible and acceptable process, can be a promising and cost-effective way to improve the performance of rollers of rolling lines and even hot rolling mill rolls.