Non-metallic Inclusions Research Articles

Optimization of scarfing depth for high quality automotive external panel steel slabs

Scarfing is commonly employed to improve the surface quality of interstitial-free (IF) steel slabs used for automotive external panels, and usually the steelworkers tend to scarf deeper to ensure surface quality even at the cost of losing yield. However, this may not work and sometimes the surface quality becomes even worse. In the present work, slab scarfing experiments were designed to study the effect of slab scarfing depths on the density of sliver defects on the cold rolled sheets and the distribution of nonmetallic macro inclusions (NMIs) in the slab surface were evaluated using automatic scanning electron microscopy (SEM). Results show that deeper scarfing cannot guarantee high surface quality, and the number of alumina-based sliver defects after slab scarfing 6–11 mm for a single side was much larger than those slabs with scarfing less than 6 mm and over 11 mm. In addition, inclusion aggregation zones (IAZs) existed at 7∼12 mm, and 7∼11 mm from the loose and fixed slab surface, respectively. A stagnant zone under the submerged entry nozzle (SEN) bottom with the solidifying shell thickness of 8∼13 mm may account for the existence of IAZs. Accordingly, a scarfing depth of 3 mm is recommended to balance removing hooks and ensure inclusions will not be exposed to the surface.

Enhanced Characterization of Non-Metallic Inclusions in Ultra-High-Strength Steels Using Advanced Synchrotron-Based X-ray Absorption Spectroscopy and Chemometric Analysis

Enhanced Characterization of Non-Metallic Inclusions in Ultra-High-Strength Steels Using Advanced Synchrotron-Based X-ray Absorption Spectroscopy and Chemometric Analysis

Grain size characterization of nickel alloy 718 with optimized metallographic sample preparation route followed by a novel etching technique

Abstract A suitable etching technique can distinguish the appearance of microscopic features such as grain boundaries (GBs), annealing twins (TBs), and precipitates, unlike nonmetallic inclusions, voids, and microcracks, which are visible in as-polished conditions. The difficulties arise when a semi-automatic or automatic grain size (GS) analyzer detects the TBs in addition to GBs concurrently. This study introduces a novel etching technique that has selectively highlighted the GBs without or faintly emphasizing TBs in heat-treated additively manufactured (AM) and wrought nickel alloy 718, respectively. The authors then measured the GS using the comparison and intercept procedure (lineal and Abrams three-circle) according to ASTM E112-2013. Moreover, the comparative study identified the comparison procedure as the most effective approach based on accuracy, post-processing, and time consumption. However, it had limitations in terms of precision and applicability. In contrast, the intercept procedure emerged as the preferred choice for higher accuracy demands.

Study on the Separation Process of Non-Metallic Inclusions at the Steel-Slag Interface Using Water Modeling Under Static and Dynamic Conditions

Study on the Separation Process of Non-Metallic Inclusions at the Steel-Slag Interface Using Water Modeling Under Static and Dynamic Conditions

Tracing the Origin of Oxide Inclusions in Vacuum Arc Remelted Steel Ingots Using Trace Element Profiles and Strontium Isotope Ratios

Non-metallic inclusions (NMIs) in steel have a detrimental effect on the processing, mechanical properties, and corrosion resistance of the finished product. This is particularly evident in the case of macroscopic inclusions (>100 µm), which are rarely observed in steel castings produced using state-of-the-art technologies, whereby casting parameters are optimized towards steel cleanliness, and post-treatment steps such as vacuum arc remelting (VAR) are used, but frequently result in the rejection of the affected product. To improve production processes and develop effective countermeasures, it is essential to gain a deeper understanding of the origin and formation of NMIs. In this study, the potential of elemental and isotopic fingerprinting to trace the sources of macroscopic oxide NMIs found in VAR-treated steel ingots using SEM-EDX, inductively coupled plasma mass spectrometry (ICP-MS), laser ablation ICP-MS (LA-ICP-MS), and laser ablation multicollector ICP-MS (LA-MC-ICP-MS) were exploited. Following this approach, main and trace element content and 87Sr/86Sr isotope ratios were determined in two specimens of macroscopic NMIs, as well as in samples of potential source materials. The combination of the data allowed the drawing of conclusions about the processes leading to the formation of these inclusions. For both specimens, very similar results were obtained, indicating a common mechanism of formation. The inclusions were likely exogenous in origin and were primarily composed of calcium–aluminum oxides. They appeared to have undergone chemical modification during the casting and remelting process. The results indicate that particles from the refractory lining of the casting system most likely formed the macroscopic inclusions, possibly in conjunction with a second, calcium-rich material.

Influence of refining slag composition on nonmetallic inclusions in 38CrMoAl steel

Influence of refining slag composition on nonmetallic inclusions in 38CrMoAl steel

Tracing non-metallic inclusions in steel with low levels of enriched magnesium stable isotopes: A novel approach

Tracing non-metallic inclusions in steel with low levels of enriched magnesium stable isotopes: A novel approach

INVESTIGATION OF THE INFLUENCE OF TECHNOLOGICAL FACTORS IN THE SMELTING OF LOW-ALLOY STEEL ON RESISTANCE TO HYDROGEN CRACKING

In the last decade, the oil and gas industry has been in dire need of seamless steel pipes resistant to corrosion destruction, which is associated with the development of oil production containing large amounts of hydrogen sulfide and other aggressive impurities. A key role in achieving high indicators of resistance to hydrogen cracking is given to the development and use of methods for controlling the type, quantity, size and morphology of non-metallic inclusions, forms of impurity presence, precipitation of non-metallic excess phases or strengthening structural components. The authors analyzed the current technology for smelting and casting of 13HFA steel at the KSP Steel PB LLP enterprise and developed a set of technological measures for smelting, extra-furnace treatment and casting of 13HFA steel, ensuring a high level of resistance to hydrogen cracking. A series of melts carried out according to the developed technological indicators ensured the achievement of the main HIC indicators at the level of CLR and CTR = 0 %. The research was conducted within the framework of grant funding from the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan under the competition for grant funding for scientific and (or) scientific and technical projects for 2024–2026 under the project AP23487674 «Complex processing of bauxites of Kazakhstan with additional extraction of iron by alternative reducing agents in the implementation of the low-carbon development strategy». Keywords: low-alloy steel, hydrogen cracking, smelting, out-of-furnace processing, continuous casting.

USING COAL FLOTATION WASTE AS A HEAT-INSULATING BILLING FOR THE HEAD PART OF A FORGING INGOT

The experience of using coal flotation waste as a weakly exothermic insulating backfill for insulating the head part of forging dead-melted steel ingots is presented. It has been shown that when using weakly exothermic fills based on single-component fills in the form of coal flotation waste, it is possible to reduce the chemical heterogeneity of the ingot by producing a closed shrinkage cavity, which allows halving heat loss and depth of penetration of shrinkage looseness into the body of the ingot, reducing the segregation of impurities, compacting the head part of the ingot and increasing the yield; moreover, the profitable part of the ingot is more dense and less contaminated with nonmetallic inclusions. The studied patterns of the formation of a closed shrinkage cavity with a dense “bridge” in the head part of a dead-melted steel ingot made it possible to develop and implement a technology for casting large forging ingots of sufficiently high quality using weakly exothermic heat-insulating materials based on metallurgical waste (coke screenings, coal flotation waste)

Investigation on the deformation mechanism of alkali metal on inclusions in cord steel containing different aluminium content

The control and modification of non-metallic inclusions are crucial in enhancing the deformability and production efficiency of cord steel. This study investigated the effects of Na2+ and K2+ on the morphology, composition and deformability of inclusions in cord steel by adding Na2CO3 and K2CO3. Scanning electron microscope equipped with energy-dispersive spectrometer and FactSage were applied to analyse the melting point and morphology of inclusions in ingots and forged samples. The results showed that the deformability of inclusions was improved and the melting point of inclusions decreased by adding Na2CO3 and K2CO3. These inclusions were in the form of long strips after forging. Moreover, the deformability of inclusions in steel increased more obviously by adding Na2CO3 than that with K2CO3. This study also found that the deformability of inclusions in sample with higher aluminium content was worse than that in sample with lower aluminium content. The inclusions can be deformed effectively under the condition of adding alkali metals into steel containing low aluminium content.

Analysis of the Distribution of Non-Metallic Inclusions and Its Impact on the Fatigue Strength Parameters of Carbon Steel Melted in an Electric Furnace.

Steels are currently the most commonly used industrial construction materials. The use of steels depends on their properties, including their fatigue strength. Despite the fact that many works have been devoted to fatigue strength studies, there is still a lack of research discussing the fatigue strength of low-carbon steels. This deficiency is also visible when analyzing the influence of impurities on the fatigue properties of these steels. In most cases, the literature of material fatigue tests includes results obtained for materials produced on the laboratory scale, and it is difficult to directly translate these results to the industrial scale, on which steels for industrial applications are produced. This paper presents studies on the influence of non-metallic inclusions on the fatigue strength coefficient. The analyzed steel contained an average of 0.23% C, 1.23% Mn, and 0.0025 B. It was melted in 140-ton production furnaces, and after being tapped into a ladle, it was desulphurized and refined with argon. A classic plastic working process was used to produce steel samples. Based on the analysis of the test results, it was mainly found that the fatigue resistance coefficient k decreased with the increase in impurities spacing, and with a large share of smaller non-metallic inclusions, a higher fatigue resistance coefficient was noted, which may indicate that small non-metallic inclusions with an oval shape do not reduce the fatigue life of steel, regardless of its microstructure.

The Mechanism of Modification Influence on Non-Metallic Inclusions in the Weld Metal of High-Strength Low-Alloy Steels

An analysis of the effect of modification by dispersed particles of various compounds on the distribution, composition, and morphology of non-metallic inclusions and phase precipitates in the weld metal of low-alloy high-strength steel has been conducted. It has been established that modification with dispersed TiN or Al<sub>2</sub>O<sub>3</sub> particles leads to the enlargement of non-metallic inclusions in the weld metal. It has been shown that some modifier particles of SiC or TiC dissolve in the liquid metal pool and precipitate as separate new phase inclusions on or near the surface of non-metallic inclusions, which overall results in changes in the composition and morphology of non-metallic inclusions in the weld metal. In the case of using ZrO<sub>2</sub> or TiO<sub>2</sub> modifiers, small 20-60 nm dispersed non-metallic inclusions are formed, enhancing the modification effect. During the analysis, no primary particles of modifiers were detected, but separate phase separations were detected, which may indicate the complete dissolution of particles in a liquid metal bath of some types of SiC, TiC separations and their subsequent separation from a supersaturated solid solution upon cooling welded joint. In cases where zirconium oxides ZrO2 or TiO<sub>2</sub> were used as modifying compounds, the size reduction of refractory oxides inoculated into the welding bath to nanosize (30...70 nm, the size of which can be compared to the size of the tip of the dendrite growing from the liquid metal of the weld pool during the crystallization process, increases the efficiency of the modification.

Effect of rare earth lanthanum on non-metallic inclusions in Fe-Mn-C-Al alloy

ABSTRACT The effect of La addition on non-metallic inclusions in Fe-Mn-C-Al alloy was studied by adding different contents of rare earth lanthanum (La). Among the studied samples, the one with La addition of 0.0043 wt.% demonstrates the best inclusion characteristics. In this sample, the average size of inclusions measures at 1.16 μm. Compared with the sample without the addition of rare earth La, the size and area density of inclusions decrease, while the quantity density increases. With the increase of rare earth addition, inclusions in the samples showed a gradually increasing trend in inclusions size and area density, but both were lower than those in the sample without the addition of rare earth La. Through scanning electron microscopy observation, as the amount of rare earth La added increases, MnS inclusions are gradually replaced by rare earth sulfides. Based on classical thermodynamics and Factage thermodynamic software, the modification law of inclusions after La addition was calculated. Combining theoretical calculations and scanning electron microscopy experimental observations, it was found that the main transformation path of non-metallic inclusions in La treated alloy is: Al2O3 → LaAl11O18 → LaAlO3, MnS → MnS + La2S3 → La2S3 + LaS.

Effect of nonmetallic inclusions and phase precipitates on the fatigue fracture resistance of low-carbon microalloyed steels

Effect of nonmetallic inclusions and phase precipitates on the fatigue fracture resistance of low-carbon microalloyed steels

Impact of Scrap Impurities on AlSi7Cu0.5Mg Alloy Flowability Using Established Testing Methods

In view of the increasing demand for secondary aluminum, which is intended to partially replace the very energy- and resource-intensive primary aluminum production, effective treatment methods can maintain the high quality level of light metal castings. The transition from a linear to a circular economy can result in an accumulation of oxides or carbides in aluminum. Therefore, melt purification is crucial, especially as foundries aim to increase the use of often dirty end-of-life scrap. Nonmetallic inclusions in the melt can impact its flowability and mechanical properties. As the purity of the melt increases, its flow length also tends to increase. Available assessment methods like reduced pressure test or K-mold are capable of ensuring high levels of purity. This study demonstrates the implication of inclusions originating from dirty scrap. An experimental test run deals with various scrap contents in an AlSi7Cu0.5Mg alloy and shows correlations between impurity and performance, expressed by flowability and mechanical properties. These performance indicators have been connected to inclusion and porosity rates. In conclusion, these findings emphasize the need for further extensive research on contaminants in the field of scrap melting and the development of methods for easy-to-handle assessment methods.

Results of metallographic studies of cutting parts of cultivator paws made of 30MnB5 steel

Rationale. Cultivators are widely used in our country for surface tillage. Moreover, their most common working organ is the pointed paw. In recent years, foreign manufacturers of agricultural machinery have begun to use boron-containing steels in the manufacture of working parts of agricultural machinery, which can increase the wear resistance and durability of machine parts. The article presents the results of metallographic studies of the structure and properties of the cutting parts of pointed cultivator paws made of boron-containing steel 30MnB5. The purpose of the work is to study the structure and properties of boron-containing steels after surfacing relit and subsequent hardening. Materials and methods. When carrying out metallographic studies, we used the cutting parts of the paws of the KPIR-3.6 and KPU-5.4 cultivators, mass-produced according to OST 23.2.164-87 at the Buinsky Machine-Building Plant of the Republic of Tatarstan. These working bodies were made of steel grade 30MnB5 DIN EN 10083-3. To ensure heterogeneity of the structure, a layer of relit was fused to one side of the cutting blade of the cultivator paw, after which the entire working element was hardened. The macro- and microstructure of the metal part was studied using a microsection cut out to the cutting edge. For macrostructural studies, a stereoscopic microscope from MEIJI RZ with a magnification of up to 7 times was used. The microhardness of the part was measured using the Vickers method (GOST R ISO 6507-1-2007) at different loads on a MicroMet 5104 microhardness tester. Contamination of the base metal of the part with non-metallic inclusions was assessed using the “Ш4” method according to GOST 1778-70. Results. The proposed manufacturing technology for cultivator blades made of 30MnB5 steel made it possible to obtain a cutting part that is heterogeneous in structure and hardness, which ensures self-sharpening of the blade during the friction of the cultivator blade on the soil. The steel base of the cultivator paw after heat treatment has a troostomartensite structure with a microhardness of ~ 564 HV 0.3. The deposited layer of relit has a dendritic cast structure of tungsten with a microhardness of 900...1020 HV 0.05 and tungsten carbides with a microhardness of 2315...2460 HV 0.05. The wear of paws made of 30MnB5 steel turned out to be 9.5% less than that of working bodies made of 65G steel. The cost of manufacturing working parts using the proposed technology was reduced by 14.3%. Conclusion. The practical value of the study lies in the fact that the results of studies of the cutting parts of self-sharpening cultivator paws, made of 30MnB5 steel using the proposed technology, are used in the production process of Buinsky Machine-Building Plant OOO in the Republic of Tatarstan. The paws manufactured using the proposed technology are installed on cultivators KPIR-3.6 and KPU-5.4. The presence of the self-sharpening effect of the paws made it possible to increase the quality of products required by consumers and its high competitiveness.

Microstructure analysis of non-metallic inclusions in continuous casted steels

Abstract According to the current quality requirements in the steel production field, high purity of steel composition is required. For this reason, defect detection technology is developing significantly. The paper presents the analysis of 35 charges of continuous casted steel, highlighting the presence of defects by microstructure analyzing of non-metallic inclusions in the semi-finished steel composition. The purpose of using these products is the automotive industry, in the production of hydraulic cylinders. The quality of the steel is directly reflected in the quality of the final product, in the mechanical properties and the duration of the life cycle.

Assessment and Improvement of Melt Quality of Recycled Secondary A357 Alloy by Application of the High Shear Melt Conditioning (HSMC) Technology

In addition to impurities in recycled aluminum alloys, non-metallic inclusions are a significant factor that deteriorates the material’s castability and final mechanical properties. This, therefore, restricts the ability to transition from a primary to secondary aluminum alloy. In this study, the cleanliness of the recycled A357 alloy was evaluated through non-metallic inclusions’ characterization, hydrogen content measurement, fluidity test, and casting defects identification. The non-metallic inclusions generated during the recycling process of A357 alloy were collected by the pressurized melt filtration technique. All of the inclusion types collected during filtration were examined and identified by analytical scanning electron microscopy (SEM). Extra additions of up to 2 wt.% swarf in these secondary A357 alloys were designed to simulate highly contaminated alloys. Different to the conventional melt cleaning technologies that mainly focus on complete removal of inclusions, this study developed a novel approach that combines the removal of easily removeable inclusions while preserving well-dispersed inclusions that do not adversely affect the mechanical properties. This study demonstrates that high shear melt conditioning (HSMC) technology can achieve well-dispersed small non-metallic inclusions, low hydrogen content, improved fluidity, and fewer casting defects. As a result, the melt quality of the recycled A357 alloys has achieved a quality comparable to that of primary A357 alloy.

Spalling Life Prediction for Rolling Bearings Using a Model with Stress Intensity Factor and Statistical Evaluation of Non-Metallic Inclusions

Spalling Life Prediction for Rolling Bearings Using a Model with Stress Intensity Factor and Statistical Evaluation of Non-Metallic Inclusions

Microstructure evolution and fatigue crack initiation life prediction of actual failed bearings under GRCF conditions

During the operation of bearings under alternating stress, contact fatigue failure often occurs, primarily due to non-metallic inclusions in bearing steel (GCr15). Based on actual fatigue-failed bearings, this study used Aspex scanning electron microscopy to analyze the inclusion distribution in bearing steels produced by two processes: electroslag remelting and vacuum refining. FIB-TEM technology was employed to characterize the microstructural evolution characteristics at the fatigue failure source area. Finally, considering the depth, area, and matrix hardness of the inclusions, a fatigue life prediction model based on gigacycle rolling contact fatigue (GRCF) was proposed. The prediction results closely matched the fatigue data of actual failed bearings.