High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe-Cr-Mn-Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 0.69% in 18Crl8Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel-free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 0.81%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 um. After homogenization of the hot rolled plate at 1 150℃ × 1 h followed by water quenching, the microstructure consisted of homogeneous austenite.

Heavy Metals in Soil and Salad in the Proximity of Historical Ferroalloy Emission

Emissions of manganese (Mn), lead (Pb), iron (Fe), zinc (Zn), copper (Cu) from ferro-alloy operations has taken place in Valcamonica, a pre-Alp valley in the province of Brescia, Italy, for about a century until 2001. Metal concentrations were measured in the soil of local home gardens and in the cultivated vegetables. Soil analysis was carried out using a portable X-Ray Fluorescence (XRF) spectrometer in both surface soil and at 10 cm depth. A subset of soil samples (n = 23) additionally was analysed using the modified BCR sequential extraction method and ICP-OES for intercalibration with XRF (XRF Mn = 1.33 * total OES Mn – 71.8;R = 0.830, p Lactuca sativa and Chichorium spp.) were analyzed with a Total Reflection X-Ray Fluorescence (TXRF) technique. Vegetable and soil metal measurements were performed in 59 home gardens of Valcamonica, and compared with 23 gardens from the Garda Lake reference area. Results indicate significantly higher levels of soil Mn (median 986 ppm vs 416 ppm), Pb (median 46.1 ppm vs 30.2 ppm), Fe (median 19,800 ppm vs 13,100 ppm) in the Valcamonica compared to the reference area. Surface soil levels of all metals were significantly higher in surface soil compared to deeper soil, consistent with atmospheric deposition. Significantly higher levels of metals were shown also in lettuce from Valcamonica for Mn (median 53.6 ppm vs 30.2) and Fe (median 153 vs 118). Metals in Chichorium spp. did not differ between the two areas. Surface soil metal levels declined with increasing distance from the closest ferroalloy plant, consistent with plant emissions as the source of elevated soil metal levels. A correlation between Mn concentrations in soil and lettuce was also observed. These data show that historic ferroalloy plant activity, which ended nearly a decade before this study, has contributed to the persistence of increased Mn levels in locally grown vegetables. Further research is needed to assess whether this increase can lead to adverse effects in humans and plants especially for Mn, an essential element that can be toxic in humans when exceeding the homeostatic ranges.

CHARACTERISTICS OF MARTENSITE IN A HIGH CARBON FERROALLOY

Some characteristics of plate martensite in a 1.03% C ferroalloy have been studied by using the transmission electron microscopy.The habit plane of the plate martensite in this ferroalloy was found to be close to{224}_f.The morphology,distribution,coalescence and curving of martensite as well as the substructure in both martensite and austenite have been observed. The mechanism of both nucleation and growth of the martensite have been discussed.

THE SOLUBILITY OF FERROALLOYED NEODYMIUM IN MOLTEN SALT CONTAINING NEODYMIUM TRICHLORIDE

The solubility of ferroalloyed neodymium in molten salt containing neodymium trichloride and the de- pendence of solubility on temperature and composition of the melt are determined by means of electrochemical method.The data obtained are in good agreement with result of chemical analysis of the quenched molten salt samples.

Sulfur distribution in preparation of high titanium ferroalloy by thermite method with different CaO additions

Ferrotitanium is used as a deoxidizer and alloying agent during steelmaking process,which has a high demand for sulfur control.Sulfur was introduced from raw materials in the process of producing ferrotitanium by thermite method,where CaO was used as fluxing agent.At the same time,CaO has a great desulfurization capability.Effects of CaO addition on the distribution of sulfur in high titanium ferroalloy prepared by thermite method were studied in this work.The equilibrium diagram of Ti-AlFe-S system was calculated by FactSage 6.4 software package with FactPS and FTmisc database.The alloy and slag samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),inductively coupled plasma atomic emission spectrometer(ICP-AES),X-ray fluorescence(XRF)and high-frequency infrared ray carbon sulfur analyzer.The result indicates that the sulfur in the alloy firstly exists in the form of liquid FeS,thereafter TiS(s)and eventually Ti2 S(s)during cooling.The sulfur is mainly distributed in the alloy,and only a small amount of sulfur remains in the slag.Moreover,it is noted that the sulfur in the alloy does not distribute homogeneously,and it exists in the form of solid solution phase,(Ti,Al,Fe)S.S content in the slag,the sulfur capacity of the slag and the sulfur distribution ratio(LS)all increase with the increment of CaO addition,while S content in alloys decreases.

Effect of Melting Iron-Based Alloy Temperature on Carbon Content Observed in Laser-Induced Breakdown Spectroscopy

Our recent work has determined the carbon content in a melting ferroalloy by laser- induced breakdown spectroscopy （LIBS）. The emission spectrum of carbon that we obtained in the laboratory is suitable for carbon content determination in a melting ferroalloy but we cannot get the expected results when this method is applied in industrial conditions： there is always an unacceptable error of around 4% between the actual value and the measured value. By comparing the measurement condition in the industrial condition with that in the laboratory, the results show that the temperature of the molten ferroalloy samples to be measured is constant under laboratory conditions while it decreases gradually under industrial conditions. However, temperature has a considerable impact on the measurement of carbon content, and this is the reason why there is always an error between the actual value and the measured value. In this paper we compare the errors of carbon content determination at different temperatures to find the optimum reference temperature range which can fit the requirements better in industrial conditions and, hence, make the measurement more accurate. The results of the comparative analyses show that the measured value of the carbon content in molten state （1620 K） is consistent with the nominal value of the solid standard sample （error within 0.7%）. In fact, it is the most accurate measurement in the solid state. Based on this, we can effectively improve the accuracy of measurements in laboratory and can provide a reference standard of temperature for the measurement in industrial conditions.

Mossbauer Measurements of Amorphous Nd-Fe Films

The 57Fe Mossbauer measurements for amorphous NdxFe1-x films (x=0.20-0.40), prepared by flash evaporation with substrate temperature 77K, show a broad hyperfine distribution and it is nearly independent of Nd content x. The effective magnetic moment of Fe atoms in the film is μFe=1.30μB and independent of x within the investigated composition range. The magnetic ordering temperatures Tc deduced from Mossbauer measurements are consistent with those from magnetic measurements under the same conditions (H&rarr0).

Research on Collision Response of Titanium Alloy Cylindrical Pressure Shell

Titanium alloy materials are widely used in the marine and aviation fields due to their excellent properties. The submersible sailing on the water surface is faster than underwater diving, so once an accident occurs, the consequences are unimaginable. Based on the failure criterion of the J-K model, this paper uses finite element simulation software to study the impact of impact velocity and impact angle on the collision response of a titanium alloy cylindrical pressure shell, providing a reference for the deep sea titanium alloy pressure shell.

Preparation of Fe_(3)Si and FeSi intermetallic compounds from copper slag by electrochemical method

Fe_(3)Si and FeSi intermetallic compounds were prepared by CaCl_(2)-NaCl melt electrolysis at 800℃from the non-magnetic copper slag compound.The phase transition of the cathode particles with different electrolysis voltages and durations was investigated by X-ray fluorescence spectroscopy,inductively coupled plasma spectroscopy,X-ray diffraction,and scanning electron microscopy.The results showed that Fe_(3)Si and FeSi intermetallic compounds can be obtained by one-step electrolysis for 10 h at 3.2 V and two-step electrolysis of 2.5 V for 4 h and 3.2 V for 6 h.However,the current efficiency increased from 31.70%of one-step electrolysis to 39.87%of two-step electrolysis.The formation of Fe_(3)Si and FeSi intermetallic compounds is a gradual evolution process with the increase in Si content,following the formation law of Fe→FeSi→Fe_(3)Si+FeSi→FeSi.The metallic impurities of the final product were 1.29 wt.%Mg and 3.85 wt.%Al,respectively.