Formation of Complex Inclusions in Gear Steels for Modification of Manganese Sulphide

Suitable MnS inclusions in gear steel can significantly improve the steel machinability and reduce the manufacturing costs. Two gear steel samples with different sulphur contents were prepared via aluminium deoxidation followed by calcium treatment. The shape, size, composition and percentage distribution of the inclusions present in the steel samples were analyzed using an electron probe micro-analysis (EPMA) technique. The average diameter of MnS precipitated on an oxide inclusion is less than 5 µm. It was found that the steel with high sulphur content contains a greater number of elongated MnS precipitates than low sulphur steel. Moreover, there are more oxide inclusions such as calcium-aluminates and spinels with a small amount of solid solution of (Ca,Mn)S in low content sulphur steel after calcium treatment, which indicates the modification of solid alumina inclusions into liquid aluminates. The typical inclusions generated in high sulphur steel are sulphide encapsulating oxide inclusions and some core oxides were observed as spinel. The formation mechanisms of complex inclusions with different sulphur and calcium contents are discussed. The results are in good agreement with thermodynamic calculations.

Effect of packaging material and postharvest calcium treatment on weight loss, decay and biochemical quality of strawberry fruits during storage

Strawberry (Fragaria x ananassa Duch.) fruits are highly perishable which lose their marketability within a short period of time, resulting in considerable loss of fruits after harvest. In present study, the packaging materials treatment i.e. polypropylene terephthalate (PET) Punnet and High density polythene (HDPE) crates and calcium compounds (CaCl2 and Ca(No3)2) were examined for the storability and biochemical quality of strawberry (cv. Winter Down) fruits in cold condition (3±1 °C) in comparison to the untreated control fruit in ambient storage for 3, 6 and 8 days storage period. Results revealed that physiological loss in weight (PLW) and fruit decay increased with the advancement of the storage period irrespective of the treatments. Fruits treated with CaCl2 (2%), packed in PET Punnets and stored in cold condition (3±1 °C) showed significantly minimum PLW (6.55, 11.12 and 15 34 %) and fruit decay (7.29, 17.71 and 34.38 %) at 3, 6 and 8 days storage, respectively. Non-treated control fruits at ambient conditions could not maintain their marketability even 3 days of storage and showed relatively high decay losses (25.00, 62.21 and 91.67 % at 3, 6 and 8 days of storage, respectively). Packaging and calcium treatment did not affect the fruit total soluble solids (TSS) and total sugars but was found effective to slow down the decrease of ascorbic acid and acidity contents of the fruit during storage. PET Punnets packaged fruits treated with CaCl2 (2%) under cold conditions retained better shelf-life with better biochemical quality of fruits during storage while untreated control fruits deteriorated rapidly.

The resistance of peanut to soil-borne pathogens improved by rhizosphere probiotics under calcium treatment

Background Peanut (Arachis hypogaea L.) is an important oil and economic crop. Calcium modulates plants in response to abiotic stresses and improves plant resistance to pathogens. Enrichment of beneficial microorganisms in the rhizosphere is associated with plant disease resistance and soil development. The purpose of this study was to analyze the differences in peanut rhizosphere microbial community structure between the calcium treatment and the control during two growth stages and to explain why calcium application could improve the resistance of peanuts to soil-borne pathogens. Results The 16S rDNA amplicon sequencing of rhizosphere microbiome showed that calcium application significantly enriched Serratia marcescens and other three dominant strains at the seedling stage. At the pod filling stage, ten dominant stains such as Sphingomonas changbaiensis and Novosphingobium panipatense were enriched by calcium. Serratia marcescens aseptic fermentation filtrate was mixed with PDA medium and inoculated with the main soil-borne pathogens in the seedling stage, which could inhibit the growth of Fusarium solani and Aspergillus flavus. The aseptic fermentation filtrate of Novosphingobium panipatense was mixed with PDA medium and inoculated with the main soil-borne pathogens in the pod filling stage, which could inhibit the growth of Sclerotium rolfsii and Leptosphaerulina arachidicola. Conclusions Calcium application increases the resistance of peanuts to soil-borne pathogens by enriching them with specific dominant bacteria.

Evolution of oxide and nitride inclusions during processing of stainless steel

Because of its superior properties, stainless steel has been widely used for many applications. Nonmetallic inclusions can influence the quality of stainless steel products. A set of samples was used to track the response of inclusion composition during processing of a heat of titanium-bearing 18% chromium steel, from deoxidation after decarburization, to the solidified slab. The oxide inclusions responded as expected to additions of deoxidizers and calcium treatment, changing from silica to alumina and spinels, and then to calcium aluminates. The samples confirmed that titanium nitride can nucleate on liquid calcium aluminate during steel solidification.

Effect of Calcium Treatment on Inclusions in H08A Welding Rod Steel

The effect of calcium treatment on inclusions in H08A welding rod steel was studied by industrial experiment and using thermodynamics theory. The effects of inclusion composition, morphology, quantity, and size in H08A welding rod steel before and after calcium treatment were studied by metallographic microscope, scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). Thermodynamic studies show that the addition of calcium can form various forms of xCaO·yAl2O3, under the condition that the composition of molten steel remains unchanged, the control of calcium content is the key to generate low melting point calcium-aluminate complex non-metallic inclusions and improve the quality of molten steel. The production practice in steel plant shows that for welding rod steels, the calcium content in a suitable range can meet the requirements of calcium treatment. Effective calcium treatment can not only transform the high melting point Al2O3 inclusions into the low melting point complex non-metallic inclusions between 3CaO·Al2O3 and 12CaO·7Al2O3, but also make the original shape-diversified inclusions into the spherical calcium-aluminate complex non-metallic inclusions. Meanwhile, the total number of inclusions and large-scale inclusions in welding rod steel are reduced, and the inclusions tend to disperse in the steel, which is very conducive to the improvement of steel quality. The results show that the modification path of magnesium aluminate spinel in steel is as follows: Al2O3 → MgO-Al2O3 → MgO-CaO-Al2O3. In addition, calcium treatment can modify MgO-Al2O3 spinel in steel into liquid MgO-CaO-Al2O3 complex non-metallic inclusions with low melting point.

The Resistance of Peanut to Soil-Borne Pathogens Improved by Rhizosphere Probiotics Under Calcium Treatment

Background: Peanut (Arachis hypogaea L.) is an important oil and economic crop. Calcium can regulate plant autoimmunity, respond to biotic and abiotic stresses, and improve plant resistance to pathogens. The enrichment of beneficial microorganisms in the rhizosphere is related to plant disease resistance and soil development. The purpose was to analyze the differences of peanut rhizosphere microbial community structure between calcium treatment and control during two growth stages, and the reason that calcium application could improve peanut’s resistance to soil-borne pathogens.. Results: The 16S amplicon sequencing of rhizosphere microbiome showed that calcium application significantly enriched Serratia marcescens and other three dominant strains at the seedling stage. At the pod filling stage, ten dominant stains such as Sphingomonas changbaiensis and Novosphingobium panipatense were enriched by calcium. Serratia marcescens aseptic fermentation filtrate was mixed with PDA medium and inoculated with soil-borne pathogens, which could inhibit the growth of Fusarium solani and Aspergillus flavus at the seedling stage. The fermentation filtrate of Novosphingobium panipatense was mixed with PDA medium and inoculated with main pathogens, which could inhibit the growth of Sclerotium rolfsii and Leptosphaerulina arachidicola.Conclusions: Calcium application enhanced the ability of peanuts to resist pathogens by enriching specific dominant bacteria.

Modification of Type B Inclusions by Calcium Treatment in High-Carbon Hard-Wire Steel

To investigate the modification of type B inclusions in high-carbon hard-wire steel with Ca treatment, Si-Ca alloy was added to high-carbon hard-steel, and the composition, morphology, size, quantity, and distribution of inclusions were observed. The samples were investigated by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The experimental thermal results showed that the modification effect of inclusion was better in high-carbon hard-wire steel with Al of 0.0053% and Ca of 0.0029% than that in steel with Al of 0.011% and Ca of 0.0052%, in which the inclusions were mainly spherical semi-liquid and liquid CA2, CA, and C12A7. The inclusion size decreased from 3.2 μm to 2.1 μm. The degree of inclusions segregation was reduced in high-carbon hard-wire steels after calcium treatment. The results indicate that the modification of inclusions is conducive to obtaining dispersed inclusions with fine size. The ratio of length to width decreased and tended to be 1 with the increase in CaO content in the inclusion. When the content of CaO was higher than 30%, the aspect ratio was in the range of 1 to 1.2. The relationship between the activity of aluminum and calcium and the inclusions type at equilibrium in high-carbon hard-wire steel was estimated using classical thermodynamics. The calculated results were consistent with the experimental results. The thermodynamic software Factsage was used to analyze the effect of aluminum and calcium additions on the type and quality of inclusions in high-carbon hard-wire steels. The modification law and mechanism of type B inclusions in high-carbon hard-wire steels are discussed.