Calcium Treatment Research Articles

Influence of Calcium Treatment and Electromagnetic Stirring on Ridging in Dual‐Stabilized Ferritic Stainless Steels

Titanium and niobium are added to ferritic stainless steels (FSS) to enhance their surface and mechanical properties. The use of titanium to obtain FSS sheets that are resistant to ridging due to the formation of equiaxed rather than columnar grains during solidification is well established. However, the use of titanium results in clogging the submerged entry nozzle during casting, causing surface defects in cold‐rolled products and overall production losses. To overcome the clogging problem, calcium treatment is conducted in the ladle furnace to transform inclusions into the liquid state. However, this delays the formation of the TiN inclusions which act as nuclei for the equiaxed grains, thereby increasing the fraction of columnar grains in the slabs and susceptibility to ridging in the final cold‐rolled and annealed product. Herein, the effect of calcium treatment and electromagnetic stirring (EMS) on the equiaxed grain ratio and ridging is studied with industrially produced material. The beneficial effect of EMS on grain structure and ridging is largely lost at high calcium contents, but it can be retained, provided the level of calcium is maintained at a sufficiently low, optimum level.

Ferrosilicon-Based Calcium Treatment of Aluminum-Killed and Silicomanganese-Killed Steels

Calcium-containing ferrosilicon—FeSi(Ca)—does give much higher calcium yield than calcium disilicide during calcium treatment of steel under laboratory conditions, in line with industrial observations. Upon calcium treatment of both aluminum-killed and silicomanganese-killed steel, a new population of small calcium-rich inclusions forms. The results indicate that pre-existing (deoxidation) inclusions dissolve into the liquid steel after calcium addition, rather than directly reacting with the added calcium.

Calcium Transfer to Oxide Inclusions in Al-Killed Steel Without Calcium Treatment

Alumina inclusions generated from aluminum deoxidation may undergo several transformations depending on steelmaking conditions. Under reducing conditions, in contact with MgO-saturated slag, alumina inclusions are known to transform to spinel. However, there are uncertainties related to CaO pick-up by alumina-based inclusions. This work aims to provide some clarification of CaO pick-up by alumina inclusions through a series of experiments. First, the role of silicon in calcium transfer from slag was examined by conducting two similar experiments: one without any silicon addition and a second with 1 wt pct electronic grade silicon addition. Second, the role of crucibles was tested by conducting experiments in ZrO2 and CaO-3 pct ZrO2 crucibles. It was found that the addition of silicon significantly enhances the rate of CaO pick-up when there was no silica in the slag at the start of reaction. The effect of the crucible on CaO pick-up was found to be weaker than that of the 1 wt pct silicon addition.

Effect of calcium content on inclusions during the ladle furnace refining process of AISI 321 stainless steel

The effect of three heat processes with different calcium contents on the evolution of inclusions during the ladle furnace refining process of AISI 321 stainless steel was investigated. The size, morphology, and composition of the inclusions were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. After the addition of aluminum and titanium, the primary oxide in the AISI 321 stainless steel was an Al2O3-MgO-TiOx complex oxide, in which the mass ratio of Al2O3/MgO was highly consistent with spinel (MgO·Al2O3). After calcium treatment, the calcium content in the oxide increased significantly. Thermodynamic calculations show that when the Ti content was 0.2wt%, the Al and Ca contents were less than 0.10wt% and 0.0005wt%, respectively, which was beneficial for the formation of liquid inclusions in molten steel. Moreover, the modification mechanism of calcium on TiN-wrapped oxides in combination with temperature changes was discussed.

Sex-specific responses of Populus deltoides to combined salinity and calcium under waterlogging conditions

In this study, we investigated the sex-specific ion uptake and physiological and biochemical responses to combined salinity and calcium treatments of male and female Populus deltoides under waterlogging conditions. Results indicate that both P. deltoides clones were sensitive to salinity and calcium. Under well-watered conditions, salinity stress could especially increase the Na content in female P. deltoides clones, whereas salinity and calcium could increase the K and Ca content in male clones. Waterlogging could evidently stimulate Na content in leaves under salinity, especially in female P. deltoides clones. However, waterlogging had no visible effects on the amount of Ca absorption between the two clones under abundant calcium conditions. The physiological and biochemical responses to combined salinity and calcium exceeded the effects of salinity or calcium individually. However, no significant difference was observed, hence indicating the similar responses of male and female P. deltoides clones. The lower Na content and Na:Ca ratio, and the higher K and Ca content in male clones suggest that the male clones could maintain ion homeostasis better than the female clones. The sex-specific differences in net photosynthetic rate, intercellular CO2 concentration, effective quantum yield of photosystem II, photochemical quenching coefficient, non-photochemical quenching coefficient, photosynthetic electron transport rate, content of superoxide anions, hydroxyl radicals, H2O2, soluble protein, and activities of superoxide dismutase under certain conditions suggest that female P. deltoides clones are more sensitive to salinity, calcium, and the combination of both than their male counterparts.

Interaction of serum calcium and folic acid treatment on first stroke in hypertensive males

The role of serum calcium on the risk of stroke is still uncertain. We aimed to evaluate the effect of serum calcium on first stroke risk, and on the efficacy of folic acid treatment in prevention of first stroke among hypertensive patients. Our analyses included a total of 19,644 eligible hypertensive adults from the China Stroke Primary Prevention Trial (CSPPT). In the CSPPT, a total of 20,702 hypertensive patients were randomly assigned to a double-blind, daily treatment with either 10mg enalapril and 0.8mg folic acid or 10mg enalapril alone. The primary outcome was a first stroke. Over a median of 4.5 years, among those not receiving folic acid, a significantly higher risk of first stroke was found in hypertensive males with baseline albumin-corrected serum calcium ≥2.43mmol/L (median) (vs. <2.43mmol/L; 6.5% vs. 2.3%; adjusted HR, 2.47; 95% CI: 1.72, 3.55). For those with enalapril and folic acid treatment, compared with the enalapril only group, the risk of first stroke was reduced from 6.5% to 3.0% (adjusted HR, 0.49; 95% CI: 0.35, 0.68) in hypertensive males with baseline albumin-corrected serum calcium ≥2.43mmol/L, whereas there was no significant effect among hypertensive males with baseline albumin-corrected serum calcium <2.43mmol/L. However, among hypertensive females, serum calcium did not significantly affect the first stroke risk and the efficacy of folic acid in prevention of first stroke. Among Chinese hypertensive males, those with elevated serum calcium levels had increased risk of first stroke, and this risk was reduced by 51% with folic acid treatment.

Characterization of Nutrient Disorders and Impacts on Chlorophyll and Anthocyanin Concentration of Brassica rapa var. Chinensis

Essential plant nutrients are needed at crop-specific concentrations to obtain optimal growth and yield. Foliar tissue analysis is the standard method for assessing nutrient levels in plants. Symptoms of nutrient deficiency or toxicity occur when the foliar tissue values become too low or high. Diagnostic nutrient deficiency criteria for Brassica rapa var. Chinensis (bok choy) is lacking in the current literature. In this study, green (‘Black Summer’) and purple (‘Red Pac’) bok choy plants were grown in silica sand culture, with control plants receiving a complete modified Hoagland’s all-nitrate solution, and nutrient-deficient plants induced by using a complete nutrient formula withholding a single nutrient. Tissue samples were collected at the first sign of visual disorder symptoms and analyzed for dry weight and nutrient concentrations of all plant essential elements. Six weeks into the experiment, the newest matured leaves were sampled for chlorophyll a, b, and total carotenoids concentrations for both cultivars, and total anthocyanin concentration in ‘Red Pac’. Compared to control plants, the dry weight of ‘Black Summer’ green bok choy was significantly lower for nitrogen (N), phosphorus (P), calcium (Ca), or boron (B) deficiency treatments, and nutrient concentrations were lower for all variables except iron (Fe) deficiency. Dry weight was less in ‘Red Pac’ plants grown without N, potassium (K), Ca, B, or molybdenum (Mo), and nutrient concentrations were lower for all except Mo-deficiency compared to controls. Total chlorophyll and total carotenoid concentrations were lower in leaves from N−, Fe-, and manganese- (Mn) deficient plants of both cultivars. Leaf anthocyanin concentration was lower only for K-, Ca-, and B-deficiencies in ‘Red Pac’. Our results indicate that visual symptoms of nutrient deficiency are well correlated with nutrient disorders. In contrast, changes in dry weight, chlorophyll, and anthocyanin did not show consistent changes across nutrient disorders.

Influence of Prohexadione Calcium Rate on Growth and Yield of Peanut (Arachis hypogaea)

ABSTRACT Prohexadione calcium, a plant growth regulator, is commonly used on virginia market type peanut (Arachis hypogaea L.) cultivars to manage excessive vine growth and improve digging efficiency. However, use of prohexadione calcium on runner market type cultivars has been minimal. The objective of this research was to evaluate prohexadione calcium on virginia and runner market type peanut cultivars at multiple rates in small-plot (17 site years) and on-farm (5 site years) experiments. Applications of prohexadione calcium were at the manufacturer's recommended use rate of 140 g a.i./ha (1x), 105 g a.i /ha (0.75x), and 70 g a.i /ha (0.5x) rates. A non-treated control was also included in all experiments. Cultivar and treatment responses were evaluated based on mainstem height, yield, total sound mature kernels, and return on investment. Plants treated with prohexadione calcium had greater row definition based on a 1-10 row visibility rating scale. Plant main stem heights were often shortened when prohexadione calcium was applied compared to the control, although response varied by location and by year. Average mainstem heights were 26 cm for non-treated plots and 23 cm for prohexadione calcium treated plots across all virginia market type small plot experiments. Prohexadione calcium did not significantly increase yield at any rate in any small plot experiments regardless of rate. Reduced rates of prohexadione calcium significantly increased yield in all the large on-farm experiments compared to the control. Yield increases ranged from 453 to 731 kg/ha for all prohexadione calcium treatments compared to the control across all large plot on-farm experiments. The greatest return on investment was the 0.75x rate resulting in an increase in revenue of $210 ha−1. With an increase in yield and return on investment in all large plot on-farm experiments and not in small plot experiments no matter the market type, it is assumed that the growth and yield response to prohexadione calcium may be more pronounced where soil variability is greater, affecting growth, digging, and yield potential. Prohexadione calcium can be beneficial in virginia market type and runner market type peanut cultivars to decrease vine growth and increase yield.

Treatments of osteoporosis increase bone material strength index in patients with low bone mass

Effects on bone material properties of two-year antiosteoporotic treatment were assessed using in vivo impact microindentation (IMI) in patients with low bone mineral density (BMD) values. Antiresorptive treatment, in contrast to vitamin D ± calcium treatment alone, induced BMD-independent increases in bone material strength index, measured by IMI, the magnitude of which depended on pretreatment values. Bone material strength index (BMSi), measured by IMI in vivo, is reduced in patients with fragility fractures, but there is no information about changes in values during long-term therapy. In the present study, we assessed changes in BMSi in patients receiving antiosteoporotic treatments for periods longer than 12 months. We included treatment-naive patients with low bone mass who had a BMSi measurement with OsteoProbe® at presentation and consented to a repeat measurement after treatment. We studied 54 patients (34 women), median age 58 years, of whom 30 were treated with bisphosphonates or denosumab (treatment group) and 24 with vitamin D ± calcium alone (control group). There were no differences in clinical characteristics between the two groups with the exception of a higher number of previous fragility fractures in the treatment group. Baseline hip BMD and BMSi values were lower in the treatment group. After 23.1 ± 6.6 months, BMSi increased significantly in the treatment group (82.4 ± 4.3 vs 79.3 ± 4.1; p < 0.001), but did not change in the control group (81.5 ± 5.2 vs 82.2 ± 4.1; p = 0.35). Changes in BMSi with antiresorptives were inversely related with baseline values (r = − 0.43; p = 0.02) but not with changes in BMD. Two patients in the control group with large decreases in BMSi values sustained incident fractures. In patients at increased fracture risk, antiresorptive treatments induced BMD-independent increases in BMSi values, the magnitude of which depended on pretreatment values.

Expression and clinical significance of serum retinol binding protein 4, superoxide dismutase and hypersensitive C-reactive protein in patients with acute ST-segment elevated myocardial infarction

To analyze the expression and clinical significance of serum retinol binding protein 4 (RBP4), superoxide dismutase (SOD) and hypersensitive C-reactive protein (hs-CRP) in patients with acute ST-segment elevated myocardial infarction (STEMI). Seventy-eight patients with STEMI who underwent percutaneous coronary intervention (PCI) admitted to Nanxishan Hospital of Guangxi Zhuang Autonomous Region from January 2017 to March 2019 were enrolled. On the basis of the routine treatment, atorvastatin calcium or rosuvastatin calcium treatment was given. According to the results of coronary angiography, the patients were divided into three groups: single-vessel, double-vessel and three-vessel lesions, and the severity of coronary artery disease score (SYNTAX score) was performed. The serum RBP4, SOD and hs-CRP were measured and compared among different groups before and after treatment. The correlation between the three serum parameters of STEMI patients and the SYNTAX score, risk prediction (STEMI high-risk score) and prognosis were recorded and compared among different groups. There was no significant difference in serum RBP4, SOD and hs-CRP among different groups before treatment. In multivessel (double-vessel and three-vessel) vascular disease group, SYNTAX score was significantly correlated with RBP4 and hs-CRP (double-vessel lesions: r values were 0.616 and 0.489 respectively, three-vessel lesions: r values were 0.423 and 0.357 respectively, all P < 0.05), but had no correlation with SOD (r values were 0.108 and 0.055 respectively, both P > 0.05), and high-risk score was closely correlated with RBP4 and hs-CRP levels (r values were 0.581 and 0.623 respectively, both P < 0.01). There was no significant difference in the prognosis of patients treated with different statins. There were 8 and 7 high-risk patients in the atorvastatin calcium group and rosuvastatin calcium group, respectively, and 2 and 3 dead patients respectively (both P > 0.05). Combined detection of serum RBP4, SOD and hs-CRP levels can be used as better indicators to predict the risk of STEMI, which is worthy of clinical application.

Calcium Treatment Alleviates Pericarp Browning of 'Nanguo' Pears by Regulating the GABA Shunt After Cold Storage.

Long-term storage of pear fruit at low temperature can retard senescence but may result in pericarp browning. We previously reported that increasing endogenous γ-aminobutyrate (GABA) content by exogenous GABA treatment can maintain mitochondrial structure integrity, thereby alleviating pericarp browning of ‘Nanguo’ pears after cold storage. Here, we tested the effectiveness of Ca2+ treatment on pericarp browning in relation to GABA biosynthesis. Fruit browning was reduced by treatment with Ca2+ after 180 days of storage. Pericarp Ca2+ and calmodulin content in treated fruit increased, and concomitantly, endogenous GABA content, key GABA synthesis-related enzyme activity, and gene expression were upregulated. Moreover, the mitochondrial structure in the pericarp tissue was found to be well preserved. Thus, Ca2+ treatment effectively reduced pericarp browning of refrigerated ‘Nanguo’ pears owing to improvement in the GABA biosynthesis capacity in the fruit.

Evolution of nonmetallic inclusions in pipeline steel during LF and VD refining process

AbstractThe formation and evolution of nonmetallic inclusions in pipeline steel were investigated by SEM, EDS and INCA Feature Analysis System, with the industrial process of electric arc furnace → ladle furnace (LF) refining → vacuum degassing → continuous casting. The composition, size and amount of inclusions during refining process were discussed systematically. The results show that inclusions at each refining step are mainly small-particle inclusions (below 5 µm), and the total number of inclusions has been reduced significantly due to the refining effect of slag during LF refining. The calcium (Ca) treatment increases the amount of small inclusions. The types of inclusion are mainly Al2O3 and MnO–SiO2–Al2O3 before LF, and they are transformed into CaO–Al2O3, MgO–Al2O3 and CaO–MgO–Al2O3 during LF process. After Ca treatment, inclusions are changed to CaO–Al2O3–(CaS) and CaO–MgO–Al2O3–(CaS). Typical inclusions are still mainly CaO–Al2O3 and CaO–MgO–Al2O3 in tundish, but the composition of those inclusions has been changed and located to the low melting point region in ternary phase diagram. Such inclusions will further be removed as continuous casting approaches.

Correlation between bone turnover and metabolic markers with age and gender: a cross-sectional study of hospital information system data

BackgroundBone turnover and metabolic indicators are related to age and gender. Age and gender should be matched in subjects in disease control research of bone turnover and metabolism, but strict matching of gender and age increases the difficulty and cost of the research. Therefore, the aim of this study was to solve it is necessary to strictly match age and gender in clinical research in bone metabolism.MethodsA cross-sectional study was conducted from the data were extracted from the HIS of ZhuJiang Hospital. Data relating to seven bone turnover and metabolic indicators from 1036 patients between January 2018 and October 2019 were analyzed.ResultsP1NP, β-CTx and 25(OH)D were significant different in individuals younger than 20 years of age. ALP was significantly higher in those under 20 years of age and lower at age 20–39 compared with other age groups. The concentrations of Ca and P were different among the groups aged 0–19, 20–39, and 40–59 years of age groups but exhibited no difference above 60 years of age. PTH expression was not dependent on age. P1NP, β-CTx and PTH concentrations were not significantly different between the genders within the same age group. ALP was significantly different between genders within the age range 20–59 years. Ca and 25(OH)D were significantly different between the genders for those older than 60. Serum P was significantly different in the two genders for those aged 40–79. Patients received both alfacalcidol and calcium treatment differently from the others in P1NP, β-CTx, Serum Ca, P and ALP.ConclusionP1NP and β-CTx were highly correlated with age. If these two indictors require analysis in a case control study, the patients and controls should be strictly matched by age under 20 years. The demarcation point for ALP was 40 years of age. Ca and P were strongly recommended strict matching according to age in disease research. The difference in P1NP, β-CTx, 25(OH)D and ALP between genders depends on age differences. Medication history should be considered in bone turnover and metabolic clinical research.

Novel insights into the calcium action in cherry fruit development revealed by high-throughput mapping.

This work provides the first system-wide datasets concerning metabolic changes in calcium-treated fruits, which reveal that exogenously applied calcium may specifically reprogram sweet cherry development and ripening physiognomy. Calcium modulates a wide range of plant developmental processes; however, the regulation of fruit ripening by calcium remains largely uncharacterized. In this study, transcriptome, proteome and metabolome profiling was used to document the responses of sweet cherry fruit to external calcium application (0.5% CaCl2) at 15, 27 and 37days after full blossom. Endogenous calcium loading in fruit across development following external calcium feeding was accompanied by a reduction in respiration rate. Calcium treatment strongly impaired water-induced fruit cracking tested by two different assays, and this effect depended on the fruit size, water temperature and light/dark conditions. Substantial changes in the levels of numerous polar/non-polar primary and secondary metabolites, including malic acid, glucose, cysteine, epicatechin and neochlorogenic acid were noticed in fruits exposed to calcium. At the onset of ripening, we identified various calcium-affected genes, including those involved in ubiquitin and cysteine signaling, that had not been associated previously with calcium function in fruit biology. Calcium specifically increased the abundance of a significant number of proteins that classified as oxidoreductases, transferases, hydrolases, lyases, and ligases. The overview of temporal changes in gene expression and corresponding protein abundance provided by interlinked analysis revealed that oxidative phosphorylation, hypersensitive response, DNA repair, stomata closure, biosynthesis of secondary metabolites, and proton-pump activity were mainly affected by calcium. This report provides the fullest characterization of expression patterns in calcium-responsive genes, proteins and metabolites currently available in fruit ripening and will serve as a blueprint for future biological endeavors.

Root-mediated acidification and resistance to low calcium improve wheat (Triticum aestivum) performance in saline-sodic conditions

Salinity represents a medium with high soluble salts where as sodicity represents a medium with high exchangeable sodium, low calcium and highly alkaline pH. Salinity and sodicity commonly occur together in salt-affected soils however physiological studies have mostly considered salinity alone ending up in poor field success of the selected genetic resources. Similarly, the role of root-mediated acidification in salt resistance is not known in wheat. Here six wheat genotypes were exposed to salinity (NaCl: 125 mM), low calcium (25% of non-treated control) and salinity + low calcium in solution culture. There were significant differences among the wheat genotypes for growth and leaf ionic composition under salinity, low calcium and salinity + low calcium treatments. The wheat genotypes SARC-1, 25-SAWSN-42 and Pasban-90 accumulated higher K+ and Ca2+ and lower Na+ and Cl− and were resistant to the combined stress of low calcium and salinity.These genotypes also showed higher root-mediated acidification under stress conditions. The wheat genotypes resistant to salinity + low calcium supply in solution culture also performed better in the saline-sodic soil in a lysimeter study. A genotype resistant to salinity alone accumulated lower Ca2+ and showed lower rhizosphere acidification potential and did not perform good in saline-sodic soil conditions. Therefore, root-mediated acidification potential and resistance to low calcium supply improves resistance of wheat to saline-sodic conditions. It is further suggested that screening of the wheat germplasm for saline-sodic soils should be carried out at salinity + low calcium to better simulate saline-sodic field conditions.

Reference range for 24-h urine calcium, calcium/creatinine ratio, and correlations with calcium absorption and serum vitamin D metabolites in normal women.

Recommendations for a normal range for 24-h urine calcium vary from a low of 50 mg to a high of 400 mg; most "laboratory normal ranges" based on older literature are incorrect. The objective of this analysis is to define a normal range for young women age 25-45 years and older women age 55-90 years, white and black, for 24-h urine calcium and calcium/creatinine ratio, and to examine the relationship between 24-h urine calcium, calcium absorption, and vitamin D metabolites. Data from 3 studies was collected on 959 normal black and white women, ages 25-87 years, for 24-h urine calcium, creatinine, calcium intake, serum 25-hydroxyvitamin D (25OHD),1,25 dihydroxyvitamin D (1,25(OH)2D), and calcium absorption. Urine calcium and creatinine were measured on an auto-analyzer. Calcium absorption was measured by a single isotope method. Serum 25OHD and 1,25(OH)2D were measured by competitive protein binding assay or radioimmunoassay. Because 24-h urine calcium did not fit a normal distribution, non-parametric methods were used to determine the 95% reference interval (RI) and 90% non-parametric confidence intervals (CI) calculated for groups. The 95% reference intervals for 24-h urine calcium for women were as follows: black older 7-225 mg, black younger 8-285 mg; white older 37-275 mg, and white younger 23-287 mg. In older white women, 24-h urine calcium was significantly correlated with serum 1,25(OH)2 D, r = 0.23, p < 0.001, calcium intake r = 0.12, p = 0.001, and calcium absorption r = 0.18, p = 0.003, but not serum 25OHD r = 0.07, p = 0.06. The normal reference interval for 24-h urine calcium for black women is lower than white women. Twenty-four-hour urine calcium was correlated with serum 1,25(OH)2 D calcium intake and calcium absorption, but not serum 25OHD. This range will be useful clinically for defining hypercalciuria and for following patients on vitamin D and calcium treatment.

Postharvest calcium treatment of apple fruit increased lenticel breakdown and altered cuticle structure

Abstract Lenticel breakdown (LB) mainly occurs in susceptible ‘Gala’ and ‘Red Delicious’ apples following storage. Postharvest calcium treatment increased LB of both cultiavrs as well as the less susceptible ‘Orleans’ and ‘Granny Smith’. Calcium increased the number and size of damaged lenticels. Callose was deposited in the sub-lenticular cells and the cuticle of the damaged lenticels, as well as in non- damaged lenticels. Suberin was deposited in the sub-lenticular cells, but only in the most severely damaged lenticels, and especially in calcium-treated fruit. Postharvest calcium treatment increased the micro- cracking of the skin surface and removed the epicuticullar wax following storage. It also decreased the thickness of the cutin and wax layers. Gene expression, mainly of those involved in the wax biosynthesis and cutin and wax transport, were reduced in peel of calcium-treated fruit. Our study suggests that the deleterious effect of calcium on fruit skin occurs due to a decrease in cuticle deposition during storage, resulting in a thinner cuticle, leading to micro-cracks, which culminates in increased lenticel damage.

Synthesis of high purity nano-sized transition-metal carbides

Nano-sized transition-metal carbides with high purities were synthesized by vacuum carbothermal reduction coupled with a novel method for the removal of free carbon by molten calcium treatment. Transition-metals oxides were firstly reduced by excessive carbon black under vacuum condition, and then the obtained product was treated in molten calcium to remove the free carbon. After acidic leaching the product, pure carbides were obtained. The excess carbon in the carbothermic reduction stage could not only increase the contact between reactants and make the reduction more thorough, but also act as barrier to restrict the grain growth of the products. The effects of carbothermic reduction temperature, calcium treatment temperature and particle sizes of oxides on the reaction products were discussed in detail. It was concluded that after carbothermic reduction of corresponding oxides at 1823K in vacuum and the following calcium treatment at 1173K, TiC, ZrC, HfC, V8C7, NbC and TaC with the particle sizes of 100nm, 70nm, 130nm, 200nm, 150nm and 120nm, could be prepared, respectively.

A Review of Steel Processing Considerations for Oxide Cleanliness

Control of non-metallic inclusions is essential for the production of high-quality steel. This review summarizes processes that change inclusion compositions and concentrations during secondary steelmaking—slower changes are limited by reaction between bulk steel and slag or refractory, and faster changes involve direct additions to the steel bath. An example of the former is conversion of alumina inclusions to spinels during ladle treatment, while reoxidation and calcium treatment are typical exemplars of the fast changes. For the slower changes, inclusions approach equilibrium with the liquid steel and conceptually simple kinetic models correctly describe inclusion evolution during ladle treatment. Disequilibrium from faster changes persists for several minutes under typical ladle conditions, with small-scale inhomogeneity in the steel. Fast scanning electron microscopy with microanalysis has facilitated detailed study of these inclusion evolution processes by providing information on inclusion composition, size, and shape. Machine learning methods are likely to be increasingly important in analysis of the results. Such methods have already shown promise to improve classification of inclusions and recognizing inclusion clusters, from analyses of polished sections. Several unresolved issues that require future study are noted.

Effect of calcium treatment on inclusions in Si-Mn-killed 304 stainless steels

In the current study, two plant trials for the ladle refining process without and with the calcium treatment were compared to investigate the effect of the calcium treatment on the inclusion deformation in Si-Mn-killed 18Cr-8Ni stainless steels. The total aluminum rose from 10ppm to 25ppm due to the slag and steel reaction, increasing the Al2O3 in inclusions during the ladle refining process. Without the calcium treatment, inclusions changed from Al2O3-SiO2-MnO-CaO with about 20% MnO to Al2O3-MgO-SiO2-CaO with about 10% MnO. The calcium treatment obviously lowered Al2O3 and MnO in inclusions and led to the formation of CaO-rich inclusions. Inclusions changed from Al2O3-SiO2-CaO-MnO to SiO2-CaO-Al2O3 after the calcium treatment of Si-Mn-killed stainless steels. Calculations showed that the calcium treatment of 15−25ppm lowered the melting temperature of inclusions but further additions increased the melting temperature. Calculations also showed that calcium addition lowered Young’s modulus. Calcium treatment was an effective method to improve the deformability of inclusions in Si-Mn-killed stainless steel during the cold rolling process.