Basic Steel Research Articles

Effects of Ce addition on inclusion modification in martensitic stainless steel

The control of inclusion features, i.e., chemical composition, distribution, quantity, and size, is in high demand for stainless steels to achieve good surface quality, pitting corrosion resistance, and mechanical properties. In this paper, the effects of rare earth (RE) modification on the inclusions of martensitic stainless steel were explored. Martensitic stainless steels with various contents of Ce were prepared, and the inclusions in the cast billets were characterized by field emission scanning electron microscopy (FE-SEM) and an automatic analysis system for nonmetallic inclusions in steels (OTS). The effect of Ce on the modification of nonmetallic inclusions during solidification was explored with thermodynamic calculations. The results showed that the addition of Ce modified the oxygen and sulfur inclusions by transforming them from irregular elongated inclusions to nearly spherical RE composite inclusions. Compared with those in basic martensitic stainless steel, nine types of RE inclusions were found in the presence of Ce. As the Ce content increased from 0.048 wt% to 0.092 wt%, the CeAlO3 content decreased, whereas the Ce2O2S content increased. Moreover, there were 80% fewer inclusions than in the basic martensitic stainless steel.

Reactivity of air granulated basic oxygen furnace steel slag and its immobilization of heavy metals

Air granulation of basic Oxygen furnace slag can improve its hydraulic potential to enhance recycling potential. The hydration behaviour of the slag has been investigated via isothermal calorimetry, QXRD, and TG/DTG analysis. The air granulated slag exhibited improved early-age hydration and led to the formation of C–S–H, hydrogarnet, and hydrotalcite phases. The slag reactivity is controlled by the dissolution of SiO2 and Fe2O3 bearing phases as observed by SEM-EDX-based PARC analysis and the hydration degree reaches up to 41% after 28 days curing. The hydrated slag features an improved immobilization of V and Cr as confirmed by ICP-OES analysis.

Digital twin model of a large scale hot molten metal ladle pouring system

In steel-making processes, large quantities (frequently exceeding 300 t) of liquid metal are transferred between vessels. In Basic Oxygen Steel (BOS) making process, metal is poured from Hot Metal (HM) ladles, utilising overhead gantry cranes, into furnaces for further processing. Due to the large quantities of liquid metal poured, this operation poses significant safety concerns associated with metal spillage and releases of heat emissions. This can further lead to damage being caused to surrounding infrastructure. Pouring automation can reduce the likelihood of metal spillage, optimising ladle movement for reduction in heat emission releases. Given the hazardous nature of this operation, robust testing and evaluation of automated crane pouring movements is required prior to their application. A digital twin (DT) model of an overhead gantry crane/HM ladle system is presented here, intended to provide a safe testing environment for controlled pouring movement and serve as a testbed for control system design studies. Accurate crane movement is achieved using multi-body dynamics, solving for non-linearities present due to rigid joint frictional components. The flow rate of HM is estimated through the application of a dynamic model, allowing the modelling of system dynamics due to differences in HM pouring weights. The devised DT model is evaluated by simulating real crane movement and making a comparison on the resultant changing HM weight inside the ladle. The devised DT removes the need for construction of a physical model or performing tests directly on the HM pouring system.

Enhancing Accuracy and Consistency in the Valuation of Plant and Equipment through Cubic Regression Models of Physical Deterioration

The valuation of plant and equipment often involves valuers deducting physical, functional and economic depreciation from replacement cost estimates. These calculations have faced accuracy and consistency problems in the aspect of determining how much physical deterioration should be deducted. This study attempted to develop cubic regression models to resolve these accuracy and consistency problems in the basic metal, iron and steel and fabricated metal product sectors in Ogun state, Nigeria (Sango Ota and Agbara). Questionnaire surveys were administered on senior operators of plant and equipment in these sectors to draw information on the degree of physical deterioration of plant and equipment over service life, using expenditure on repairs as a proxy for physical deterioration. The questionnaire sought information on the service lives of plant and equipment, the pattern of physical depreciation over the service lives, and the degree to which the pattern is influenced by various operational factors. Data were analysed using means, standard deviations, multiple linear regressions and cubic regressions, to produce what could be the first potentially accurate and consistent valuation model of physical deterioration in Africa. The service lives of various plant and equipment were found to range at various times between 8 to 60 years. Cubic regression analyses showed that the pattern of the movement of transitions of expenditure on repairs (proxy for physical deterioration) over useful life of plant and equipment were not linear but cubic, and generally followed S-shaped patterns. Multiple regression analyses showed that the S-shaped patterns were in turn influenced by operational factors (such as intensity of use and power outages). The study concluded that valuers’ interests in accuracy and consistency in plant and equipment valuation were not served by any of the accounting methods hitherto used by valuers; accuracy in physical deterioration modelling follows an S-shaped transition over time.

An investigation on effectiveness of tuned mass damper (TMD) device in mitigating structure vibration: a case study of small-scale steel beam

TMD devices are considered a reasonable solution to enhance the bearing capacity of the structures under unpredictable impacts from external forces because their operating principle is quite simple and does not vary the main structure. This paper investigated the influence of the TMD device, including its mass and stiffness, on the vibration reduction of the primary structure, a basic steel beam. In which, a small-scale steel beam model with boundary conditions through experiments was carried out. Then, simulated the experiment using MATLAB based on the experimental results to study the effect of TMD on the vibration of the structure. The results exhibit that the vibration-damping capacity of the main structure increases as the TMD mass increases. The stiffness of the main structure is less than 1,8k for both TMD 3% and 5%, resulting in the rapid increase of oscillation reduction efficiency.

Identification of Intermetallic Phases Limiting the Growth of Austenite Grains in the Low-Pressure Carburizing Process

This article presents the results of a study to identify intermetallic phases whose role is to limit austenite grain growth in the low-pressure carburizing process. A drawback of high-temperature low-pressure carburizing is the austenite grain growth during the process. Using low-pressure carburizing with pre-nitriding technology (PreNitLPC®) offers the possibility of reducing austenite grain growth. This technology involves the application of doses of ammonia during the heating stage of the steel, at the carburizing temperature, to introduce nitrogen into the surface layer of the steel and to form nitrides. It is these phases that cause restrictions on austenite grain growth during carburizing. The research carried out in this article was aimed at identifying these phases. The research was carried out on one of the basic steels used for carburizing—16MnCr5 steel. The carburizing of this steel with and without pre-nitriding was performed, followed by an evaluation of the austenite grain size after these processes and the identification of the intermetallic phases present in the surface layer of the steel.

Implementation of model predictive control in a programmable logic controller

The article is aimed at the development of modern automatic control systems, which should provide high-performance indicators in the conditions of variable operating modes of industrial equipment due to effective control structures and algorithms. The purpose of the study is to reduce the cost of the basic oxygen furnace steel, which is a consequence of the increase in the share of scrap metal due to the enhanced post-burning of CO to CO2 in the cavity, by optimal controlling the duty mode parameters using model-predictive control. The blowing mode of the basic oxygen furnace was considered as a technological object of control, and the problem of controlling blowing parameters in conditions of non-stationarity of the rate of metal decarburization was analyzed. The use of a model-predictive controller made it possible to improve the quality of control for the oxygen flow circuit by 39% and the maximum dynamic deviation of the CO2 content in the gases was reduced by 16.5% compared to the PID control. The implementation of a software-hardware control system using model-predictive control based on a programmable logic controller is considered.

Testing procedures for CO2 uptake assessment of accelerated carbonation products: Experimental application on basic oxygen furnace steel slag samples

Many CO2 reactive by-products from industrial processes can be valorised via carbonation to produce building materials. The amount of CO2 captured in mineralisation processes is environmentally and economically relevant, however results from the literature are often controversial owing to a lack of standardisation in the existing CO2 quantification techniques.In this study testing procedures for the assessment of carbonation efficiency are outlined and applied on basic oxygen steel slag samples providing CO2,uptake estimates ranging from 13.3% to 17.0%. Thermogravimetry, thermal decomposition and acid digestion, emerged as valuable techniques for carbonates quantification that can be adopted on samples of different nature, i.e. powders, pastes and mortars. Advantages and drawbacks of each method are discussed, and their field of application is defined. A comparison of the experimental results with similar studies from the literature is reported as well.

Effect of Supercritical Bending on the Mechanical & Tribological Properties of Inconel 625 Welded Using the Cold Metal Transfer Method on a 16Mo3 Steel Pipe.

The presented work deals with the investigation of mechanical tribological properties on Inconel 625 superalloy, which is welded on a 16Mo3 steel pipe. The wall thickness of the basic steel pipe was 7 mm, while the average thickness of the welded layer was 3.5 mm. The coating was made by the cold metal transfer (CMT) method. A supercritical bending of 180° was performed on the material welded in this way while cold. The mechanical properties evaluated were hardness, wear resistance, coefficient of friction (COF) and change in surface roughness for both materials. The UMT Tribolab laboratory equipment was used to measure COF and wear resistance by the Ball-on-flat method, which used a G40 steel pressure ball. The entire process took place at an elevated temperature of 500 °C. The measured results show that the materials after bending are reinforced by plastic deformation, which leads to an increase in hardness and also resistance to wear. Superalloy Inconel 625 shows approximately seven times higher rate of wear compared to steel 16Mo3 due to the creation of local oxidation areas that support the formation of abrasive wear and do not create a solid lubricant, as in the case of steel 16Mo3. Strain hardening leads to a reduction of possible wear on Inconel 625 superalloy as well as on 16Mo3 steel. In the case of the friction process, the places of supercritical bending of the structure showed the greatest resistance to wear compared to the non-deformed structure.

Thermal fatigue testing with repeatable temperature cycles on thermomechanical simulator

This paper presents two thermal fatigue tests developed to simulate the typical thermal fatigue behavior of hot-work tools and rolls. The tests are carried out on a Gleeble 1500D thermomechanical simulator with computer-controlled heating and cooling of the test specimens. In the first test, internal cooling of the specimens is performed, and in the second test, external cooling is performed. This allows constant test conditions and the collection of reliable experimental data on the thermal fatigue behavior. The internally cooled test rig is used for testing the thermal fatigue properties of bulk materials. Indefinite chill double-poured cast iron is used to present the basic capabilities of the test. At the material, the cracks take flattened graphite–cementite pathways. The external cooling test rig, on the other hand, is designed for comparative testing of four surfaces simultaneously. Thus, the capabilities of the second test are presented in the comparative testing of three different laser-welded functionally graded material surface layers and the basic H13 tool steel, simultaneously. The highest thermal fatigue resistance is shown by the weld with the lowest silicon (Si) content. Quantitative evaluation of thermal fatigue resistance as well as following of degradation processes in both tests is enabled.

Refining at the impact and emulsion zones of basic oxygen steel making process – a fundamental study

ABSTRACT Insights into the kinetics occurring during the combined blown (top and bottom blowing) oxygen steelmaking process, particularly at the impact and emulsion zones within separate reactors, can provide a deeper understanding of the refining mechanism in steelmaking. A dynamic model has been developed that can predict the contributions of various refining processes such as decarburization, desiliconization, demanganization, and dephosphorization. The model considers gas–metal interactions at the impact zone and slag–metal–gas interactions at the emulsion zone in an oxygen steelmaking converter. The model includes sub-models for lime dissolution and heat loss calculation. FactSage™ software and its macro programming facility were employed to integrate thermochemical and kinetic information into the model. The model predicts the temperature, composition, and volume of several phases involved in the process. The model predictions transient metal and slag compositions and metal bath temperature, were found to be consistent with the plant data.

Dissolution behavior of steelmaking slag for Ca extraction toward CO2 sequestration

The indirect steel slag (SS)-based carbon capture, utilization, and storage (SS-based CCUS) process is recognized as a promising way for simultaneous mitigation of CO2 emissions and valorization of wastes. Even so, much still needs to be done for sizeable and economic implementations of the SS-based CCUS process, such as enhancement of the selective extraction efficiency of Ca from SS, and a prior prediction of the Ca extraction potential of SS. It is necessary to simultaneously study mineralogy, morphology, solution chemistry, and passivation layer during the dissolution process of SS to improve the overall understanding of the Ca extraction behavior and dissolution mechanism. Therefore, in this work, three kinds of SS were investigated, such as basic oxygen steel slag (BOFS), electric arc furnace slag (EAFS), and ladle furnace slag (LFS). First, the mineral phase composition, and Ca distribution of various SS were identified and compared. In addition, the Ca extraction behavior and passivation mechanism of various SS were investigated by carrying out a series of leaching and corrosion tests in NH4Cl and CH3COOH solution. Results showed that whilst the Ca contents of the three SS samples were similar, the leaching behavior and the Ca extraction yield were significantly different. In addition, various passivation layers were observed, which was formed closely related to the dissolution manner of mineral phases in various solution environments, which was further assessed at atomic level.

Comparison of main metal industry sub-business lines from occupational health and safety perspective using CIRITIC and EDAS methods

The basic metal industry is one of the most economically important business lines in the manufacturing industry. According to the Social Security Institution (SSI) 2020 data, the basic metal industry in Türkiye is represented by 16 sub-businesses lines. In this study, it is aimed to evaluate the risk levels of the sub-business lines of the basic metal industry class, which is included in the SSI economic activity classification. Occupational Health and Safety data included in the 2020 SSI statistics were used to determine risk levels. The number of employees who have an occupational disease, the number of deaths because of work accidents, the period of temporary incapacity for work (inpatient), the period of temporary incapacity for work (outpatient), and the number of employees who have had a work accident are the criteria selected from these data. In the evaluation made according to these criteria, Multi-Criteria Decision-Making methods were used. Criteria Importance Through Intercriteria Correlation (CRITIC) and Evaluation Based on Distance from Average Solution (EDAS) methods were used to determine and classify the importance levels of the criteria determined for 16 sectors. As a result of the analysis, it has been determined that the riskiest sector among the main metal industry sub-business lines is the “Manufacture of basic iron and steel products and ferrous alloys” and the most important criterion is the number of insured persons with occupational diseases.

Dry Magnetic Separation of Ash from a Coal Power Station

The purpose was to expand the applicaation area of dry ash in power plants. It was shown that using ash with a low content of Fe2O3 (~7%) allows to obtain a high-iron concentrate with a Fe2O3 content of 70%. The Fe2O3 extraction from ash is dependent on the magnetic induction and fractional ash composition. The conclusion was made about the possibility of using the obtained magnetite concentrate in ferrous metallurgy in the manufacture of basic iron and steel.

Mechanical Properties of Open-Graded Asphalt Friction Course Mixtures with Basic Oxygen Furnace Steel Slag as Coarse Aggregates

Open-graded asphalt friction course (OGAFC) is an asphalt course constructed over a dense-graded and impermeable surface to allow quick drainage of surface water runoff and enable reduction of hydroplaning and splash and spray. OGAFC mixtures demand high-quality aggregates to perform the intended functions while transferring traffic loads to the underlying layer. Steel slag is a byproduct generated during steel production, and large quantities are unutilized in steel-producing countries, including India. This study evaluated the mechanical performance properties of OGAFC mixtures using basic oxygen furnace (BOF) steel slag as replacement for coarse aggregates at percentages of 0%, 25%, 50%, 75%, and 100%. OGAFC mixtures with two types of modified asphalt binders and five percentage replacements of coarse natural aggregates with BOF steel slag were fabricated. The mechanical performance of the OGAFC mixtures was evaluated in terms of rutting resistance (dynamic creep test and Hamburg wheel tracking device test), cracking potential (indirect tensile strength, cracking tolerance index, and semicircular bending test), fatigue life (indirect tensile fatigue test), and modulus properties (indirect tensile stiffness modulus and resilient modulus). The test results indicated that the use of BOF steel slag not only improved the performance of OGAFC mixtures in terms of rutting resistance, cracking potential, and modulus properties, but also increased the fatigue life of the OGAFC mixes. OGAFC mixes up to 100% BOF steel slag content exhibited superior performance compared with the mixtures with natural aggregates.

The influence of the addition of different kinds of slags on the friction and emission behavior of a commercially employed friction material formulation

Keeping sustainability and the circular economy in mind, numerous studies have been conducted on the feasibility of the utilization of industrial wastes in friction material formulations for braking applications. One such highly produced waste is slags from blast furnaces. The present work focuses on the friction, wear, and emissions behavior of a commercially employed friction material formulation observing the inclusion of three kinds of slags. Two types of slags were obtained from a blast furnace; the difference was the cooling method. The third type of slag was collected from a basic oxygen steel furnace. The prepared samples were tested in the form of pins on a pin on disc equipment at 1.51 m/s, 1 MPa, and ambient conditions to replicate a mild braking scenario. Irrespective of the type of slag, the addition of the wastes observed either a decrease or similar emissions when compared to the virgin formulation. The friction and wear were in the range comparable to that of the reference composition; the CoF for slag specimens ranged between 0.49 and 0.51 compared to 0.45 for the reference composition. On the other hand, by inspection of the worn surfaces of the pins, it was seen that the slag-containing specimens had compact and expansive secondary contact plateaus with the inclusion of slag particles in their composition. Through this preliminary analysis, the possibility of the utilization of different slags is highlighted, especially in an already implemented commercial formulation, paving the path for further testing and validation.

Remediation of Acid Mine Drainage (AMD) Using Steel Slag: Mechanism of the Alkalinity Decayed Process.

Steel slag has been proven to be an effective environment remediation media for acid neutralization, and a potential aid to mitigate acid mine drainage (AMD). Yet its acid neutralization capacity (ANC) is frequently inhibited by precipitate after a period of time, while the characteristics of the precipitate formation process are unclear yet. In this study, ANC for basic oxygen steel slag was conducted by neutralization experiments with dilute sulfuric acid (0.1 M) and real AMD. Some partially neutralized steel slag samples were determined by X-ray diffraction (XRD), scanning electron microscopy combined with an energy dispersive spectrometer (SEM-EDS), and N2 adsorption tests to investigate the potential formation process of the precipitate. The results indicated that Ca-bearing constitutes leaching and sulfate formation were two main reactions throughout the neutralization process. A prominent transition turning point from leaching to precipitate was at about 40% of the neutralization process. Tricalcium silicate (Ca3SiO5) played a dominant role in the alkalinity-releasing stage among Ca-bearing components, while the new-formed well crystalline CaSO4 changed the microstructure of steel slag and further hindered alkaline components releasing. For steel slag of 200 mesh size, the ANC value for the steel slag sample was 8.23 mmol H+/g when dilute sulfate acid was used. Neutralization experiments conducted by real AMD confirmed that the steel slag ANC was also influenced by the high contaminants, such as Fe2+, due to the hydroxides precipitate reactions except for sulfate formation reactions.

Utilisation of aged and unaged basic oxygen furnace steel slag aggregates in pavement quality concrete

ABSTRACT The study presented in the paper evaluated the properties of pavement quality concrete (PQC) containing coarse aggregates made from aged and unaged basic oxygen furnace (BOF) slag. Workability, air content, strength, drying shrinkage, expansion, abrasion resistance and expansive potential of PQC were evaluated. Air content and workability of fresh slag concrete increased marginally. Compressive and flexural strength of the concrete containing aggregates of aged and unaged slag was observed to be less than the strength of normal concrete. The reduction in strength of concrete containing aged slag aggregates was more as compared to the concrete containing unaged slag aggregates due to the presence of a dusty coating around the aged aggregates. The drying shrinkage of the concrete increased with the content of steel slag aggregates. The abrasion resistance of the slag concrete was found to be better than the abrasion resistance of conventional concrete. Deterioration of slag concrete was not observed due to normal water curing up to 90 days. However, accelerated aging of concrete in water at 70°C resulted in the localised cracking and eruptions due to expansion. The study showed that, aged as well as unaged slag aggregates may be used for the preparation of concrete mixtures of required properties for road construction.

Cost effective decarbonisation of blast furnace – basic oxygen furnace steel production through thermochemical sector coupling

We present here a first-principles study of the sector coupling between a thermochemical carbon dioxide (CO2) splitting cycle and existing blast furnace – basic oxygen furnace (BF-BOF) steel making for cost-effective decarbonisation. A double perovskite, Ba2Ca0.66Nb0.34FeO6, is proposed for the thermochemical splitting of CO2, a viable candidate due to its low reaction temperatures, high carbon monoxide (CO) yields, and 100% selectivity towards CO. The CO produced by the TC cycle replaces expensive metallurgical coke for the reduction of iron ore to metallic iron in the blast furnace (BF). The CO2 produced from the BF is used in the TC cycle to produce more CO, therefore creating a closed carbon loop, allowing for the decoupling of steel production from greenhouse gas emissions. Techno-economic analysis of the implementation of this system in UK BF-BOFs could reduce steel sector emissions by 88% while increasing the cost-competitiveness of UK steel on the global market through cost reduction. After five years, this system would save the UK steel industry £1.28 billion while reducing UK-wide emissions by 2.9%. Implementation of this system in the world's BF-BOFs could allow the steel sector to decarbonise in line with the Paris Climate Agreement to limit warming to 1.5 °C.

The macrosegregation behaviour of Fe-C-Cr-Mo type steel in laboratory scale model ingot.

In ingot casting, it is important to predict and control segregation and casting defects that occur during the solidification process, because they have a significant effect on the quality of the steel ingot. In some special steels, in typical Fe-C-Cr-Mo type high carbon tool steels, macro-segregation tends to be more pronounced due to their wide solid-liquid coexistence temperature range and molten steel properties such as relatively higher liquid viscosity than basic carbon steels. In order to investigate segregation and defect formation phenomena during solidification, many experiments have been conducted using specially designed laboratory scale model ingots that can induce partial difference of solidification to cause macrosegregation phenomena. However, these kind of experimental approaches for special steels are less conducted and influence of alloy types on the macrosegregation behaviour is still not well understood. In this study, a model ingot which have a steel chill ring in the middle region of a mullite mold was prepared, then Fe-0.45C(mass%) carbon steel, Fe-1C-1.8Cr(mass%) bearing steel and Fe-1C-8Cr-2Mo(mass%) high carbon tool steel were cast into 30kg ingots and the macrosegregation behaviour was investigated.