Cast Steel Research Articles

Enhanced thermal shock resistance and higher molten steel purification efficiency of Al2O3-MgAl2O4-C filter with in-situ β-SiC whiskers: Compared with Al2O3-C filter

The porous ceramic filter is mainly utilized in the final stage of molten steel casting and serves as an important means for adsorbing non-metallic inclusions in order to improve the quality of the steel. In this study, Al2O3-MgAl2O4-C filter (filter AM) was prepared from porous Al2O3-MgAl2O4 micropowder, and referenced Al2O3-C filter (filter A) was prepared from α-Al2O3 micropowder. The phase composition, microstructure, mechanical properties and purification efficiency on molten steel of filter AM were compared with filter A by XRD, SEM, EDS and immersion test with molten steel. The results indicate that the filter AM exhibited a uniform skeleton without cracks, and plenty of β-SiC whiskers were generated internally. However, there were some cracks in the strut of filter A with the formation of many SiC/SiO2 spheres inside. The different microstructures resulted in the retention rate of cold compressive strength after thermal shock test as high as 91.11 % for filter AM and only 58.06 % for filter A, respectively. According to the immersion test, an Al2O3-MgAl2O4 layer was formed on the rougher surface of filter AM and contributed to the adsorption of the inclusions, leading to about 80 % reduction in the quantity of inclusions of various sizes. The cleanliness of steel was significantly improved as the T.O content was reduced from 56.3 ppm to 11.7 ppm. Finally, the mechanisms underlying the enhancement of thermal shock resistance and the improvement of purification efficiency by porous Al2O3-MgAl2O4 micropowder were proposed.

Does Sn2+ play well with Zn2+ as their molten chloride salts react with Cr–Al–B MAB phase?

Novel Zn-MAX phases like Ti2ZnC were synthesized in the literature by the reaction between Lewis acid salts like ZnCl2 and the MAX phase. The interactions between the Cr–Al–B MAB phase contained in the PLS coating formed during HDA of Fe–Cr–B cast steel and five types of molten chloride salts (ZnCl2 and SnCl2) were investigated. The results showed that the Cr-(Al, Zn)–B and Cr-(Al, Sn)–B MAB phase solid solution were formed as the PLS coating reacted with the molten ZnCl2 and SnCl2, respectively, through topochemical reaction. Zn and Sn could not coexist in the A-site Cr–Al–B MAB phase solid solution, and the replacement ability of Sn2+ contained in molten salt was much stronger than that of Zn2+. Zn and Sn whiskers could spontaneously grow on the Cr-(Al, Zn)–B and Cr-(Al, Sn)–B MAB phase solid solution respectively.

Experimental and computational investigation of FGM coated cylinder liners prepared using HVOF technique

In the present work, to improve the wear resistance of the cylinder liner, without affecting the heat dissipation, cast steel cylinder liners are coated with five-layer Functionally Graded Material (FGM) coatings prepared using High-velocity oxy-fuel (HVOF) technique. The powders were designated as C1 (WC-10Co-4Cr) which is Tungsten Carbide with 10% Cobalt and 4% Chromium, C2 (WC-12Co) which is Tungsten Carbide with 12% Cobalt and C3 (Ni-25Cr) which is Nickel with 25% Chromium. The results revealed that the FGM coating designated as Functionally Graded Coated Sample-1 (FGCS-1) wears less compared to Functionally Graded Coated Sample-2 (FGCS-2) and Functionally Graded Coated Sample-3 (FGCS-3), due to the presence of wear resistive elements in the composition and uniform material homogeneity. Numerical analysis of FGCS-2, conducted using Ansys Fluent software, revealed a negligible temperature gradient across the coating thickness. This is due to the highly conductive coating material and the extremely thin coating layers, making it suitable for engine cylinder liner applications where less wear and high heat transfer rate is desirable.

Serpentinised olivine used in tundish refractory working layer: A source of blowhole defect in steel billets

In this research, the effect of different types of commercial tundish refractory working layers (gunning mix, prefabricated board (PB), and dry mix) on the formation of blowhole defect in continuous casting steel billets was investigated. To protect the tundish body, three refractory layers are applied on its metallic shell including a safety layer, a permanent layer, and a working layer. Due to the direct contact of molten metal and slag with the tundish working layer, this layer plays an important role in guaranteeing the quality of steel. In the current research, the amount of molten metal hydrogen pick-up due to contact with the abovementioned tundish working layers was measured by a Hydris device. The hydrogen content of all the melts increased after transferring from ladle to tundish, but the rising rate strongly depended on the type of tundish working layer with PB having a minimum amount of hydrogen pick-up. To characterise the working layers, their chemical and mineralogical composition as well as their thermal behaviour up to 1400 °C were evaluated using X-ray fluorescence, X-ray diffraction, and thermogravimetry-differential scanning calorimetry techniques. The results showed that olivine is a main constituent of all the working layers. Also, the amount and quality of olivine (especially the amount of its serpentinization) have a great effect on the formation of blowhole defects in the steel billets.

Microstructure, Tensile, and Low-Stress Abrasive Wear Properties of a New High Silicon Dual-Phase Cast Steel

Microstructure, Tensile, and Low-Stress Abrasive Wear Properties of a New High Silicon Dual-Phase Cast Steel

Remaining Useful Life for Heavy-Duty Railway Cast Steel Knuckles Based on Crack Growth Behavior with Hypothetical Distributions

The current research on the integrity of critical structures of rail vehicles mainly focuses on the design stage, which needs an effective method for assessing the service state. This paper proposes a framework for predicting the remaining useful life (RUL) of in-service structures with and without visible cracks. The hypothetical distribution and delay time models were used to apply the equivalent crack growth life data of heavy-duty railway cast steel knuckles, which revealed the evolution characteristics of the crack length and life scores of the knuckle under different fracture failure modes. The results indicate that the method effectively predicts the RUL of service knuckles in different failure modes based on the cumulative failure probability curves for different locations and surface crack lengths. This study proposes an RUL prediction framework that supports the dynamic overhaul and state maintenance of knuckle fatigue cracks.

Casting Production in Poland Versus European Trends in 21st Century

This article presents changes of the total casting production volumes and of the production of castings made from basic casting alloys in Poland, in Europe and worldwide in years 2001–2021. Analogous casting production parameters were compared for Poland, Europe and countries being the leading European and global manufacturers in years 2001, 2011 and 2021. The leading casting manufacturers in Europe (with the manufacturing volume exceeding 1 million tons in the mentioned years) include Germany, Italy, the Ukraine, France and Spain. For years, the largest casting manufacturer worldwide has been China. In 2001–2021, global casting production increased from ca. 68 million tons to ca. 97 million tons (i.e. by ca. 42%), whereas the European one decreased from ca. 17 million tons to ca. 12 million tons (i.e. by close to 30%). In the analyzed period, the Polish production volume grew from ca. 0.75 million tons to ca. 0.88 million tons (i.e. by ca. 17%). The presented data reveal the decreasing importance of gray cast iron and cast steel and the increasing one of ductile cast iron and aluminum alloys. However, the Polish average annual growth rate for aluminum alloy casting production was 10.3%, whereas the global one was 3% and the European one 0.7%.

FINITE ELEMENT ANALYSIS OF A LONGITUDINAL TRANSMISSION SYSTEM

This paper addresses how a longitudinal transmission system of a car could be analyzedusing Autodesk Inventor software. The longitudinal transmission, also known as a driveshaft or cardan shaft, is a system used in rear-wheel-drive or all-wheel-drive vehicles where power is transmitted from the engine to the rear axle or to both axles. During the operation of the longitudinal transmission, various loads can lead to the wear and tear of the universal joints, resulting in failures or even the destruction of the system. To prevent these issues, we considered it necessary to analyze the modelled driveshaft using Inventor based on von Mises stresses and the safety factor. The material used in this study is cast steel with the following properties: Mass Density 7.85 g/cm³, Yield Strength 250 MPa, Ultimate Tensile Strength 300 MPa, and Young's Modulus 210 GPa. The results obtained for different angles of inclination of the universal joint axes lead to the conclusion that the positioning of the driveshaft significantly influences the durability of the longitudinal transmission system.

Shape optimization of cast steel tubular joints based on subdivision surface and genetic algorithm

Cast steel tubular (CST) joints are extensively employed in steel structures for their excellent integrity and mechanical performance. However, the diverse configurations of CST joints result in the absence of standard verification formulas, leading to inefficient trial-and-error design approaches. To tackle this issue, this paper introduces a novel shape optimization method for CST joints that integrates subdivision surface techniques with genetic algorithms. The method comprises three key components: geometric modeling, structural analysis, and optimization algorithm, with shape optimization achieved through their collaborative operation. Applied to two types of CST joints, this approach resulted in significant reductions in joint volume by 39.2 % and structural stress by 49.0 %, respectively. The shape-optimized joints were compared with topology-optimized joints from published literatures, and demonstrated enhanced mechanical performance while presenting superior manufacturability. The proposed method offers considerable advantages over traditional trial-and-error approaches and topology optimization methods. It generates designs with continuous and smooth boundaries, better suited for the conventional casting process, and overcomes manufacturability issues of topology optimization. Additionally, the genetic algorithm allows for flexible selections of optimization objectives, addressing the restrictions of topology optimization methods. Furthermore, the methodʼs high level of automation is anticipated to expedite the joint design process, significantly reducing the requirement for manual intervention.

Growth Kinetics and Development of the Solid–Liquid Interface in Low-Carbon and High-Alloy Steel Castings Enabled by Confocal Microscopy

Growth Kinetics and Development of the Solid–Liquid Interface in Low-Carbon and High-Alloy Steel Castings Enabled by Confocal Microscopy

Effect of Niobium Modification on Solidification and Crystallization Mechanism of Medium-Carbon Cast Steel

Effect of Niobium Modification on Solidification and Crystallization Mechanism of Medium-Carbon Cast Steel

Investigation of The Effect of Molding Material Difference on Design in GGG70 Ductile Cast Iron Production

The casting process involves filling a prepared mould cavity with molten metal, which takes the shape of the container. While the liquid metal takes the shape of the container it is in, the method is attractive, while the volumetric changes during the liquid-solid transformation reveal the importance of moulding design for the manufacture of solid parts. Especially in cast irons, moulds with the same design may produce different results depending on the changing casting and foundry conditions because the volumetric change that occurs during the solidification of ductile cast irons is affected by many parameters and develops differently than in steel and aluminium castings. This study used model wet and resin molding materials to create single and double-riser moulding and castings with different section thicknesses. The importance of the type of mold material used in castings and the number of feeders for the robust production of the cast part was evaluated using experimental and modeling techniques. When the results were examined, it was seen that the shrinkage risk was lower with resin mould than with green sand moulding. In addition, depending on the riser connection point, the importance of the riser neck has emerged.

Spontaneous growth of Sn whisker on the hot-dipping Al[sbnd]Sn alloy coating on Fe-Cr-B cast steel

Although the MAX phase solid solutions and spontaneous growth of Sn whiskers had been reported widely, the study on the spontaneous growth of whisker at room temperature on the MAB phase was very rare. In our previous work, the periodic layered structure consisted of alternatively arranged Cr-Al-B MAB phase and FeAl3 was formed during the hot-dip aluminizing of Fe-Cr-B cast steel. Herein, the Cr-(Al, Sn)-B MAB phase solid solution was prepared by HDA of Fe-Cr-B cast steel in a AlSn alloy melt and subsequently thermal diffusion treatment. Sn atoms in the Al melt could partially occupy the positions of Al atoms in the Cr-Al-B MAB phase by A-site replacement approach, which resulted in the formation of the Cr-(Al, Sn)-B MAB phase solid solution. Subsequently, spontaneous growth of β-Sn whisker occurred on the Cr-(Al, Sn)-B MAB phase solid solution at room temperature. The original Sn source was the pure Sn phase among the grains of Cr-(Al, Sn)-B MAB phase solid solution. The mass transport pathway for maintaining the spontaneous growth of Sn whiskers was: pure Sn among the grains of Cr-Al-B MAB phase→ Cr-(Al, Sn)-B MAB phase→ SnO2 → Sn whisker. The spontaneous growth of Sn whisker in the air resulted in the deep grooves covered on the surface of whisker, while, growth in the vacuum resulted in the prism structure at the bottom of whisker. The spontaneous growth of Sn whisker could grow from both the bottom and the tip. The findings will expand the family of MAB phase and help well understand the growth mechanism of Sn whisker.

Properties of Laser-Alloyed Stainless Steel Coatings on the Surface of Gray Cast Iron Discs

The influence of laser-alloyed stainless steel coatings on the properties of the surfaces of cast iron discs, such as friction-induced vibration and noise, friction coefficient, residual stress, hardness, and corrosion resistance, was investigated in this study. The experimental results show that after laser alloying, the surface hardness of the cast iron discs increased significantly. The residual stresses on the surfaces of the laser-alloyed discs changed from tensile to compressive residual stresses, while any compressive residual stresses increased by more than six times. Most of the laser-alloyed discs demonstrated better performance in friction-induced vibration and noise damping and friction reduction. Metallographic observation and XRD (X-ray diffraction) analysis results show that the laser-alloyed layer is mainly a mixture of acicular martensite and dendritic material, while the phase composition of laser-treated discs is mainly martensitic, [Fe, Ni], Fe3Si, Cr23C6, and austenite, which plays a significant role in the improvement of the properties of the laser-alloyed cast iron in physics, tribology and corrosion resistance. This research has significance for the laser surface treatment of various cast irons and steels, which is an increasingly important manufacturing technology in the vehicle friction brake industry.

Characteristic analysis of mold level fluctuation during continuous casting of Ti-bearing IF steel

Mold level fluctuation has always been one of the key factors in slab quality control. Abnormal fluctuations can easily cause slag entrainment and form surface defects of hot-rolled and cold-rolled steel sheets, thus reducing the product qualification rate. In this study, mold level fluctuation data was collected during Ti-bearing Interstitial Free (IF) steel in a stable state for a complete casting sequence in a certain factory. The mold level fluctuation is analyzed using the discrete wavelet transform (DWT) method, and its characteristic values are classified based on frequency. Combined with the corresponding process parameters, the causes were traced during abnormal fluctuation characteristic values. It was found that the formation of abnormal mold level fluctuation mainly comes from two aspects. On the one hand, there are random fluctuations in the low-frequency band, and on the other, there are clustered fluctuations in the relatively high-frequency band. There is always a rising trend in mold liquid levels when there are random abnormal fluctuations in the low-frequency band. There is a delay of approximately 0.1412 s in the feedback of the stopper rod to the mold level fluctuation. The major causes of the low-frequency random fluctuations include variations in the tundish weight, casting speed, and mold width, and the clogs peeling. The clogging of the side hole at the submerged entry nozzle (SEN) is the primary cause of abnormal clustered fluctuations in the high-frequency band. These are certain relationships with clogging, whether it is high-frequency clustered or low-frequency random abnormal fluctuations. Without a doubt, this is a crucial link that limits the slab quality.

Calculation and experimental study of reactivity between CaO–BaO–Al2O3–CaF2–Li2O mould slag and low density and high strength steel

In the continuous casting of low-density and high-strength steel, minimising or eliminating steel–slag reactions is imperative to ensure stable slag properties and a smooth casting process. This study conducted steel–slag contact experiments at 1400 °C, based on thermodynamic calculations predicting the reaction trends of the proposed CaO–BaO–Al2O3–CaF2–Li2O mould slag with low-density and high-strength steel containing 8 wt-% Al. The changes in compositions, rheological, and solidification characteristics of slags pre- and post-reaction are analysed. The findings reveal that only Li2O reacts with Al in the steel, forming LiAlO2 rather than Al2O3. Reactivity is affected by component activity and the partial pressure of Li vapour at the reaction interface, established to vary between 0.154 and 0.253 atm. Within the current range of slag composition, increasing Al2O3 and reducing Li2O content in the slag inhibits the slag–metal reaction. Specifically, Li2O remains unreactive with Al when 2.5 wt-% < Li2O < 5 wt-% and Al2O3 > 27 wt-%. Conversely, the reaction occurs when Li2O > 4.5 wt-% and Al2O3 < 18 wt-%. In conclusion, low- and non-reactive mould slags suitable for casting low-density and high-strength steel are proposed, considering both reactivity and stable slag properties.

Effect of cooling rate on solidification microstructure, microsegregation, and nanoprecipitates in medium carbon CrMo cast steel

Precipitation strengthening is a crucial method for enhancing the mechanical properties of steel. The bridgman directional solidification furnace, optical microscope (OM), scanning electron microscope (SEM), electron probe analyzer (EPMA) and transmission electron microscope (TEM) were used to investigate the effect of solidification cooling rate on the solidification microstructure, microsegregation, and nanoprecipitates in medium carbon CrMo cast steel. The results indicate that as the cooling rate increases, the solidification microstructure is significantly refined. The relationship between the cooling rate (CA) and primary dendrite arm spacing (PDAS, λ1) and secondary dendrite arm spacing (SDAS, λ2) are given by λ1 = 123.74 × C-0.4088A, λ2 = 66.63 × C-0.6532A. Solute elements like Cr, Mo, and V exhibit noticeable positive segregation in the inter-dendritic. When the cooling rate does not exceed 0.47 °C/s, the solute concentrations in the inter-dendritic increase with higher cooling rate, leading to a decrease in the effective solute partition coefficient. This phenomenon is primarily attributed to the back diffusion of solute elements during solidification. Following heat treatment, precipitation of M6C, V(C,N), and M23C6 occurs within the inter-dendritic regions. If the solidification cooling rate does not exceed 0.47 °C/s, the density and volume fraction of nanoprecipitates increase with higher cooling rate. This trend primarily results from the reduction in critical nucleation radius and critical nucleation energy, facilitating easier nucleation of nanoprecipitates.

Calculations of phase composition of austenitic high-nitrogen welding wire and study of a welded joint made from it

The processability of a material is directly related to the possibility of its production, operation and maintainability. One of the most important indicators of the processability of any metal is weldability. Austenitic steels with a high nitrogen content proved themselves as high-strength, corrosion- and cold-resistant materials, but the issue of their weldability is still not fully understood. The lack of welding filler materials on the market specifically designed for welding high-nitrogen steels is the primary obstacle to solving this problem. Thus, the goal of the work was to develop and obtain a laboratory sample of high-nitrogen welding wire. Based on calculations of nitrogen solubility and the phase composition of the weld metal, the chemical composition of Cr – Mn – Ni – Mo – V, N steel was selected for this wire. A defect-free ingot with 0.57 % N was obtained, and wire with a nitrogen content of 0.57 wt. % was produced using hot plastic deformation and drawing methods. Testing of this wire to obtain a welded joint of austenitic cast steel, close to it in chemical composition, with the welding process carried out according to the developed technological recommendations, made it possible to obtain a defect-free welded joint without loss of nitrogen in the weld metal. With a microhardness of the base metal of 252 HV50 , due to the alloying of the welding wire steel with nitrogen and vanadium, the metal of the weld and fusion line had a high microhardness (278 and 273 HV50 , respectively), significantly exceeding the microhardness of Cr – Ni cast austenite. The metal of the welded joint has high strength (0.9 of the base metal strength) and high impact toughness. The fracture of impact samples is characterized by a dimple structure characteristic of viscous materials. According to the obtained results, the new welding wire showed itself to be a promising material for welding austenitic high-nitrogen steels.

Analysis of Fragmentation Phenomenon of Composite Layers of Fe-TiC Type Obtained “in situ” in Steel Casting

A method for fabrication of a composite layer on the surface of a steel casting using coating containing TiC substrates was presented. The reaction of the synthesis of the ceramic phase was based on the SHS method (Self-propagating High-temperature Synthesis) and was triggered by the heat of molten steel. High hardness titanium carbide ceramic phases were obtained, which strengthened the base material improving its performance properties presented in this article. Microstructural examinations carried out by light microscopy (LM) on the in-situ produced composite layers showed that the layers were the products of reaction of the TiC synthesis – the phenomenon called “fragmentation” by the authors of study. The examinations carried out by scanning electron microscopy (SEM) have revealed the presence of spheroidal precipitated and free of impurities. The presence of titanium carbide was twofold increase in hardness in the area of the composite layer as compared to the base alloy which was carbon cast steel.

Functional Failure Behavior of Submerged Entry Nozzle during the Continuous Casting Process of the Bearing Steel GCr15

The submerged entry nozzle (SEN) is an indispensable functional structural ceramic in the current continuous casting production. The stability and safety of the SEN is very important during the casting process. In this article, the functional failure of the SEN during the continuous casting process of the bearing steel GCr15 is studied. The results show that the functional failure of the SEN during the bearing steel GCr15 casting process is caused by the clogging inside the SEN which is led by the low cleanliness and the high impurities n the molten steel. The clogging in the SEN can be divided into solidified steel area, loose area, dense area, and surface area. To improve the castability of bearing steel or other high‐cleanliness steel, it is necessary to strengthen the refining process and treatment effect, strengthen the sealing and the effect of the protective casting of the molten steel, and moderate optimization of nozzle materials or the application of external fields on the SEN.