High Quality Doloma Refractories — Essential for Stainless Steel Production

In stainless steel production as in almost any kind of industrial activity it is important to know what kind of influence different factors such as process variables and conditions have on the process outcome. In order to productionally, economically and ecologically optimize the refining processes used in the production of stainless steels, one has to know these connections between the process outcomes and the process variables. In an effort to obtain this knowledge, process modelling and simulation as well as experimental procedures and analyses can be used as valuable tools (Heikkinen et al., 2010a).

The EAF Dusts and pickling sludges generated in the stainless steel production contain a lot of valuable metals such as iron, nickel, chromium and manganese. Their compositions are similar to those of laterite nickel ore, and sometimes even better than that at the contents of nickel and chromium. But it is regret that these valuable resources were random piled up or landed fill disposal. In this paper, the typical EAF dusts and pickling sludges and reductant coke powder were mixed in appropriate ratio, and then smelted in a medium frequency induction furnace. In the smelting process, the lime powder and fluorite was added to fluxing, and the ferrosilicon powder was added to strengthen the reduction. The product nickel-chromium-iron can be used as the raw material for stainless steel or cast iron production. The technology has good social and economic benefits.

Continuously increasing demands on the accuracy and durability of machine parts make it possible to expand the range of parts that need finishing machining operations. Nowadays, known methods often do not meet the requirements of intensifying metalworking and improving the performance properties of individual stainless steel parts and products, which leads to the search for the development of new methods for the final processing of various surfaces. The destruction of threaded connections operating under dynamic loads leads to emergency and unscheduled stops of machines. The performance properties of threaded connections largely depend on the quality of the faying surface. One of these methods is magnetic abrasive treatment, which is increasingly being used in practice to solve specific technological problems.

Austenitic steels are stainless steels with a high content of chromium and nickel. In the production of these (whether it be the production of stainless steel in foundries or steel mills), alloying elements need to be added to the base charge in the form of ferroalloys, primarily ferrochrome (FeCr), and, for stainless austenitic steels, also nickel (usually in the form of cathodic nickel). Alloys or alloying elements are usually very expensive due to the production process itself, while their production and transport also result in a high carbon footprint. In the production processes at Ekstera d.o.o., a large amount of grinding dust is generated during the cleaning and grinding of nickel alloys. This dust is classified as hazardous waste and can only be handed over to an authorized waste management company. We have developed and patented a process for briquetting this dust, resulting in a final product named Ni 60. Testing has shown that this briquette can replace alloying elements such as nickel, which is typically added in the form of cathodic nickel, and chromium, in the form of ferrochrome, in the production of austenitic steels. This has reduced costs for foundries while also lowering the carbon footprint and, importantly, introducing circular economy practices in the truest sense of the term at our company. We turned waste into a valuable, high-quality product.

<p>Stainless steels are well known for their durability in the built environment, having been widely used in external building cladding, street furniture and public artworks; the 1930’s stainless steel roof of the Chrysler Building is a fine example. Modern steelmaking techniques have facilitated the production of stainless steels with 85% recycled content and the production of high strength duplex stainless steels. High strength minimizes the weight of steel required and the inherent corrosion resistance means there is no need for additional corrosion protection even in aggressive coastal environments. These properties allow duplex steels to be efficiently used as durable structural engineering materials. The corrosion performance of several stainless steels, including a newly developed duplex grade LDX2404 (EN1.4662/UNS82441) has been studied in coastal atmospheric conditions. The performance of stainless steels under these test conditions is found to be similar to the performance in existing structural applications in comparable real-world environments. It is observed that the performance of a stainless steel grade can be adequately assessed in a given environment after only a few months or years, as the onset of any detrimental corrosion effects become visibly evident rather quickly. Appropriately selected grades of stainless steel for a given environment can be fully resistant to corrosion effects, and thus can be considered highly durable materials for bridges and other structural uses in the external environment.</p>

Stainless steels are corrosion resistant alloys that are widely used in consumer goods and industrial equipment. Stainless steels contain scarce and energy intensive elements such as Ni, Cr, Mo, which means that closed loop recycling is preferable for sustainable stainless steel production. However, some stainless steels are not separated from ordinary steel scraps in the recycling processes and cannot be recycled as “stainless steel”. The objective of this study is to analyze the dynamic substance flow of stainless steels in Japan and assess the potential for reducing CO2 emissions by promoting closed loop recycling of stainless steels in the future. First, the authors analyzed material balance of input elements, i.e. Fe, Ni and Cr, in the production of stainless steels in 2002 to determine which aspects associated with the material flow of stainless steel cannot be elucidated from available statistical data. The amount of post-consumer stainless steel that would enter into society in the future was estimated by employing a Population Balance Model (PBM). It was found that only 2% of post-consumer stainless steel containing Fe–Cr alloys was collected as stainless steel scraps while the remainder was collected as ordinary steel scrap. Conversely, approximately 95% of post-consumer stainless steel consisting of Fe–Ni–Cr alloys was collected as stainless steel scrap. A CO2 emission reduction potential for a 1% increase in the closed loop recycling of stainless steel scraps of Fe–Cr alloys was estimated at 75 000 t/year by Life Cycle Assessment (LCA).

Metal-roll of stainless steel is widely used in various industries of national economy. Data on domestic and European structure of stainless rolled products presented, as well as volume of Russian market of stainless steel products. In 2019 the volume of Russian market of stainless steel products accounted for 427.5 thousand tons comparing with 441.1 thousand tons in 2018. Its high dependence on import was noted. From 2014 to 2018 it varied in the range of 65.1–79%, and in 2019 it accounted for 76.6%. In 2019 the volume of Russian import of stainless steel rolled products accounted for 253 thousand tons. Within 2014–2019 import of stainless steel rolled products increase in natural terms by 58%, in cost terms – by 38%. The volume of Russian export was not large and in 2019 accounted for 13.3 thousand tons. Within 2014–2019 export of rolled stainless steel products from Russia increase in natural terms by 42%, in cost terms – by 21%. Production of stainless steel rolled products in Russia in 2014–2019 was varying in the range of 106 thousand tons (2017) to 155 thousand tons (2016). In 2019 130.4 thousand tons were produced, which exceeded level of 2018 by 7.1%. At present there are two projects for modernization and construction of new facility at Chelyabinsk metallurgical plant and metallurgical plant “Elektrostal”. Realization of the projects will enable to increase production of flat stainless steel rolled products (including cold-rolled one) by 200 and 250 thousand tons correspondently. A forecast of Russian market of stainless steel presented, according to which to 2030 its volume will increase to 1.14 mil tons, that is 2.7-fold large comparing with 2019.

This Preliminary Report is prepared to study the facilities required for recycling contaminated stainless steel scrap into plate which will be fabricated into boxes suitable for the storage of contaminated wastes and rubble. The study is based upon the underlying premise that the most cost effective way to produce stainless steel is to use the same processes employed by companies now in production of high quality stainless steel. Therefore, the method selected for this study for the production of stainless steel plate from scrap is conventional process using an Electric Arc Furnace for meltdown to hot metal, a Continuous Caster for production of cast slabs, and a Reversing Hot Mill for rolling the slabs into plate. The fabrication of boxes from the plate utilizes standard Shears, Punch Presses and welding equipment with Robotic Manipulators. This Study presumes that all process fumes, building dusts and vapors will be cycled through a baghouse and a nuclear grade HEPA filter facility prior to discharge. Also, all process waste water will be evaporated into the hot flue gas stream from the furnace utilizing a quench tank; so there will be no liquid discharges from the facility and all vapors will be processed through a HEPA filter. Even though HEPA filters are used today in controlling radioactive contamination from nuclear facilities there is a sparsity of data concerning radioactivity levels and composition of waste that may be collected from contaminated scrap steel processing. This report suggests some solutions to these problems but it is recommended that additional study must be given to these environmental problems.

In this work the technological issues related to the production of tape cast large-area porous stainless steel supports for Solid Oxide Fuel Cells (SOFC) applications were carefully investigated. The slurry formulation was optimized in terms of amount and nature of the organic components needed: rice starch and polymethyl metacrylate were found to be, respectively, the most suitable pore former and binder because easily eliminated during the thermal treatment in reducing atmosphere. The compatibility of the binder system chosen with the most widely used solvents for screen printing inks was also evaluated. Finally the influence of the sintering temperature and of the refractory supports to be used during the thermal treatments onto the production of porous stainless steel supports was discussed. The whole process optimization allows to produce flat, crack-free metallic substrate 900-1000 μm thick, dimensions up to 5×5 cm and with a tailored porosity of 40% suitable for SOFCs application.

II.10 - Thermochemical conditions for the production of low-carbon stainless steels

Reliability and performance of stainless and mild steel products in methanolic and aqueous sodium chloride media have been investigated. Weight-loss and pre-exposure methods were used. There was a higher rate of weight-loss of mild steels and stainless steels in 1% HCl methanolic solution than in aqueous NaCl solution. Solutions containing traces of sodium nitrite were found to enhance the reliability and performance of these steels. Mercuric and stannous chlorides were observed to reduce performance and reliability. Reliability and performance of these specimens decreased with continued exposure. Keywords: Reliability, performance, stainless steels, mild steels. [Global Jnl Engineering Res. Vol.2(1&2) 2003: 69-76]

Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF2, CaSO4, Me(OH)n (M: Fe, Cr, Ni), and the content of CaF2 is high in the sludge. The melting point of pickling sludge is about 1350 °C and the viscosity is about 0.14 Pa·s at 1450 °C, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF4 and AlF3 generated through the reactions of CaF2 with SiO2 and Al2O3. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.

The various groups of specialty steels require different melting techniques, treatments, pouring methods, and remelting processes. Depending on their composition and application, quality and cost are significant factors governing the decision for a specific procedure. For example, the two-stage technique—UHP electric furnace or BOF-vacuum plant—is successful in the production of anti-friction bearing steel, in that it reduces the oxide content and produces a more consistent product. In the production of alloyed engineering steels, as used by the automotive industry, excellent results are obtained with this same two-step method. This method reduces melting times with gains in purity and closer control of alloying content and grain size. For special requirements such as aircraft engines, the steel is vacuum-melted and vacuum-remelted. Precision forgings require degassing treatments and with unusual specifications for purity and freedom from segregation vacuum-arc or electro-slag remelting. Special purity tool steels are initially melted in the arc furnace or oxygen converter and then treated under vacuum. Widespread use is made of the possible variations in the two-stage arrangement, “melting furnace-vacuum plant”, in the production of stainless steels. As opposed to the traditional methods of producing this type of steel, appropriate combinations result in significant cost and quality advantages. High purity stainless steels, particularly in the form of flat shapes, are commonly VAR- or ESR-remelted. However, the most pronounced effects in melting, vacuum treatment, and remelting are found in the field of high-temperature materials.

In recent years, global warming has become a growing concern around the world, and greenhouse gases (GHG) are its major cause. In the current study, the GHG emissions from stainless steel production in Mainland China was evaluated based on two approaches. One (i.e., Approach I) was based on the data, which were collected from a life cycle inventory database (Ecoinvent). The second evaluation (i.e., Approach II) was performed according to the 2015 comprehensive energy consumption data of the Chinese stainless steel industry. When Approach I was employed, the results demonstrated that 1.44 kg CO2‐e of total GHG emissions were generated for producing 1 kg of stainless steel. When adopting Approach II, the average GHG emissions based on comprehensive energy consumption from four stainless steel manufacturers in Mainland China were calculated to be 1.76 kg CO2‐e/kg stainless steel. Further, the main hotspot area of GHG emissions for stainless steel production was found to be the blast furnace (BF) process, based on Approach I. Accordingly, employing an independent electric arc furnace (EAF) instead of a BF‐EAF, as well as choosing clean technologies and updating obsolete and low‐efficiency equipment, is recommended. It is expected that these two approaches can help stakeholders formulate a sustainable strategy for stainless steel production. And more broadly, provide some insights into adopting an appropriate framework for the evaluation of GHG emissions in industrial areas. © 2019 American Institute of Chemical Engineers Environ Prog, 38: 47–55, 2019

Process model for manufacturing 400 series stainless steel with purified CO2 as an auxiliary oxidant and realizing carbon cycle