630 stainless steel (hereinafter referred to as SUS630) stands out in cutting-edge industries due to its exceptional mechanical properties and corrosion resistance. The customers require very high standards on its purity. In this paper, the cleanliness of five SUS630 products from three processes (continuous casting, mold casting, and electroslag remelting) was investigated. The types, distribution, three-dimensional morphology, and microstructure of inclusions were compared using optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and electron probe microanalysis (EPMA). The results showed that the domestic A sample produced by the electroslag process was the cleanest, with an inclusion density of 18 inclusions/mm2 and an area fraction of 0.009%. The domestic B sample from the continuous casting process had the highest inclusion density and contained large-sized sulfide inclusions. The Japanese sample produced by the same mold casting process exhibited a uniform distribution of inclusions, while the domestic C sample showed significant Nb(N,C) segregation, posing a risk of pitting corrosion. This study filled a gap in the research on inclusions in SUS630 and provided data support for the future development of high-grade SUS630.
In the research of inclusions control, how to accurately characterize and analyze the inclusions in steel is the key link. Focused ion beam (FIB)-scanning electron microscopy (SEM) can realize the internal structure analysis and three-dimensional reconstruction of inclusions in steel as well as the sample preparation for transmission electron microscopy (TEM), so it has become an important detection method for the study of inclusions in alloy steel. In this paper, the working principle of FIB-SEM and its application in internal structure analysis, three-dimensional reconstruction of inclusions and TME sample preparation were discussed. By examining the structure, composition and distribution of inclusions in low alloy steel, high strength steel, bis steel and bearing steel, the formation process and reason of various inclusions such as magnesium aluminum spinel and sulfide complex inclusions, nitride and manganese sulfide complex inclusions, calcium aluminate and titanium nitride complex inclusions were analyzed. Through the three-dimensional reconstruction of inclusions in bearing steel, the size, three-dimensional morphology and spatial distribution of (Ti,V)N solid solution inclusions in steel were obtained. Moreover, the sample preparation for TEM was conducted. This paper provided method reference and theoretical reference for solving the problem of tracing the inclusions in alloy steel.
Rare metal ores are often associated with various dispersed metal elements such as zirconium, hafnium, uranium, thorium, thallium, gallium, tungsten and tin. However, there are few literatures on the related testing methods, and the existing rare metal ore reference materials also are in lack of certified values for associated elements such as zirconium, hafnium, gallium, thallium, uranium, and thorium. In this study, six types of rare metal ore reference materials were digested with nitric acid-hydrofluoric acid system with high pressure closed digestion. The residue was redissolved with aqua regia (1+1). The determination of zirconium, hafnium, gallium, thallium, uranium and thorium by inductively coupled plasma mass spectrometry (ICP-MS) was realized. The reference values of six associated elements in six rare metal ore reference materials were provided. The digestion effects of rare metal ore reference materials by three methods, namely open digestion with nitric acid-hydrofluoric acid-perchloric acid, open digestion with nitric acid-hydrochloric acid-hydrofluoric acid-perchloric acid, and closed digestion with nitric acid-hydrofluoric acid, were compared. The results showed that the sample could be completely digested by the high pressure closed digestion method. The rare metal ore reference materials were selected to investigate the redissolution effect by aqua regia (1+1). The results showed that the measurement values of zirconium and hafnium after redissolution with aqua regia (1+1) were consistent with those obtained by alkali fusion-ICP-MS and X-ray fluorescence spectrometry (XRF). It indicated that the hydrolysis problem of zirconium and hafnium could be solved using the oxidability of nitric acid and complexation effect of chlorine ion. The linear correlation coefficients of calibration curves of elements in this method were all higher than 0.999 9. The limit of detection and limit of quantification were 0.01-0.04 μg/g and 0.04-0.16 μg/g, respectively. The proposed method was applied for the determination of elements in certified reference materials GBW07103 (granite), GBW07832 (dispersed element ore), GBW07834 (dispersed element ore) and GBW04132 (sandstone uranium ore) with similar matrix and contents of testing elements. The relative standard deviations (RSD, n=8) of determination results were between 1.5% and 6.4%, which could meet the requirements in DZ/T 0130-2006 The specification of testing quality management for geological laboratories. The measurement results were basically consistent with the certified values of reference materials, and the relative errors (RE) were between -2.6% and 3.2%. The contents of zirconium, hafnium, gallium, thallium, uranium, and thorium in reference materials of rare metal ore (GBW07152-GBW07155, GBW07184 and GBW07185) were determined according to the experimental method, and the reference values of elements were provided. These data could be used as a reference for other studies and provided a foundation for further collaborative study and other work.
Accurate determination of trace element contents, including rare earths, in mudstone can be used to assess its potential as an energy resource, serving geological research and the strategic action for a new round of mineral exploration breakthroughs. In this paper, the mudstone sample was treated using an open acid digestion method with a five-acid system of nitric acid, hydrochloric acid, hydrofluoric acid, perchloric acid, and sulfuric acid. A mixed solution of hydrogen peroxide and aqua regia was added for extraction. Rh and Re were used as internal standards for correction. The method for the determination of 33 elements in mudstone including rare earths (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, Be, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Tl, Pb, Bi, Th, U, Ti, Nb, and Ta) by inductively coupled plasma mass spectrometry (ICP-MS) was established. The results showed that the linear correlation coefficients of the calibration curves for 33 elements were all greater than 0.999 5. The limits of detection and limits of quantification in this method were 0.000 1-0.9 μg/g and 0.000 4-3.6 μg/g, respectively. GBW07104 and five mudstone samples collected from the Turpan-Hami Basin in Shanshan, Xinjiang, were selected. The contents of 33 elements including rare earths were determined according to the experimental method. The results showed that the relative standard deviations (RSD,n=12) of the measurement results for each element ranged from 0.16% to 9.9%, which could meet the requirement of RSD ≤ 10% specified in DZ/T 0011-2015. The certified reference materials of rock (GBW07103 and GBW07104) with similar compositions to the mudstone samples were selected. The contents of 33 elements including rare earths were determined according to the experimental method. The results showed that the measured values of each element were basically consistent with the certified values. The logarithmic differences (Δlg) ranged from 0.00 to 0.08, which could meet the requirement of Δlg≤ 0.11 specified in DZ/T 0011-2015. Two mudstone samples were measured according to the experimental method, and a certain amount of mixed standard solution was added to each sample to conduct the recovery experiments. The results showed that the spiked recoveries of 33 elements including rare earths in the mudstone samples ranged from 92% to 110%, which could meet the requirement of 90%-110% specified in DZ/T 0130-2006 Specification for Quality Management of Geological and Mineral Laboratory Testing.
One imported “zinc oxide mixture”, which was a suspected solid waste, was characterized and analyzed by the means of multiple analysis methods including X-ray fluorescence spectrometry (XRF),X-ray diffraction (XRD),scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM/EDS), automatic mineral liberation analyzer (MLA) and standard methods. The characteristics of sample such as appearance, composition, physicochemical property and micromorphology were compared and matched with the commodity process source information provided by the client, the zinc-containing minerals, the zinc oxide products and retrieved relevant literature. The results showed that the appearance of the sample was milky white powdery, and it was mainly composed of zinc oxide and lead sulfate. Moreover, it also contained a small amount of alkaline lead sulfate and silicon-zinc ore. The content (mass fraction) of iron, fluorine, chlorine, cadmium, mercury, arsenic and lead in the sample was 0.52%, 0.04%, 0.62%, 0.16%, 0.000 2%, 0.26% and 11.08%, respectively. The content of zinc oxide was 81.25%. The chemical composition of the sample conformed to level requirements in the standards of YS/T 1343-2019 Zinc Oxide Riches for Zinc Smelting. The sample source may be the zinc oxide enriched materials which were obtained by reducing volatilization and enrichment processing through the rotary kiln fire method using the zinc-containing materials such as leaching slag from low-grade zinc ore and zinc concentrate as raw materials. In accordance with The law of the People's Republic of China on the prevention and control of environmental pollution by solid waste and GB 34330-2017 Identification standards for solid wastes general rules, such mixture containing zinc oxide did not belong to solid waste.
There are many kinds of by-products in iron and steel smelting with complex composition. Since they have certain reuse value, the adulteration of them in normal shipments occurs from time to time. In this study, one batch of imported "sintered iron ore" was taken as the example to establish the attribute identification method for such type of goods. According to the difference of particle size and appearance, the sample was divided into five sub-samples. The elemental composition, physical structure and micro-morphology were analyzed by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometry (EDS). The particle size and particle size distribution of powder sample were analyzed using a laser particle size analyzer. Moreover, the leachate of sample was also analyzed. The results showed that the samples were hydrophobic and the leaching solution was alkaline, which were different from that of natural iron ore. The main phases of the pelletized flakes were hematite and quartz. The main phases of irregular nodes were magnetite, hematite, iron, cementite, quartz, wüstite and calcite. The main phases of the bright flakes were wüstite, magnetite and hematite without metallic iron. The curled flakes had magnetic properties and metallic luster, and could be bent. The phases of the sample (-1 mm) were similar to those of the irregular nodes, but the particle size was very fine with non-normal distribution. There were flakes and globules with high contents of carbon and zinc. Through the comprehensive analysis of physical and chemical characteristics of each sub-sample, it was inferred that the sample mainly contained iron ore, pellet scraps and direct reduction iron residues. Moreover, the sample was mixed with solid wastes such as oxidized scale, iron chippings or shavings and precipitator dust, which belonged to the solid waste that were prohibited import items. This study provided a scientific basis for the customs supervision.
As a strategic mineral resource, the niobium-tantalum ore is often analyzed by inductively coupled plasma atomic emission spectrmetry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) after dissolution by alkaline melting or atmospheric pressure/microwave mixed acid digestion. However, the pretreatment period of these methods is long. Moreover, the prone to hydrolysis also results in lower analysis results. In this study, the determination method of Nb and Ta in ore sample by arc fractionation enrichment-emission spectroscopy was established. The carbon powder, aluminum oxide and chromium oxide were used as buffering agents in this method followed by mixing with sample in a mass ratio of 1∶1. The complete excitation of Nb and Ta in 360 s was realized. Based on the evaporation behavior of elements, the emission spectrum intensity of Nb and Ta elements increased by 1.5-2 times when the integration time was selected as 4-6 min. Hf and W with similar evaporation behavior to Nb and Ta were added quantitatively as the internal standard to improve the precision of method. The measurement range of Nb and Ta in the method was 10.6-3 635 μg/g and 88.6-8 354 μg/g, respectively. Four national first-class ore standard substances were determined according to the experimental method, and the found results were consistent with the certified values. The absolute value of relative errors were less than 18%, and relative standard deviations (RSD,n=12) were between 3.6% and 7.4%. This method adopted powder solid direct injection analysis and utilized arc fractionation enrichment to enrich Nb and Ta, which significantly enhanced the emission spectrum intensity of relevant elements, reduced the sample matrix interference, and improved the applicability and analysis efficiency of the method.
The accurate determination of alloying elements and impurities in titanium alloy is important for the performance study and quality control of alloy products. In experiments, the samples were prepared by turning or milling. After correcting the interference of coexisting elements, the analytical lines of each element were selected, i.e., Al 396.110 nm and Al 394.403 nm, Cr 425.433 nm and Cr 313.210 nm, Cu 324.710 nm and Cu 510.514 nm, Fe 259.940 nm, Mn 257.660 nm and Mn 293.310 nm, Mo 386.411mm and Mo 281.610 nm, Ni 231.604 nm, Si 288.158 nm, Sn 147.510 nm and Sn 317.505 nm, V 437.924 nm and V 290.810 nm, Zr 357.247 nm. A series of standard samples of titanium alloy for spectral analysis were used to draw the calibration curves, which were then fitted and optimized. A method for the determination of 11 alloying elements and impurities including aluminum, chromium, copper, iron, manganese, molybdenum, nickel, silicon, tin, vanadium and zirconium by spark discharge atomic emission spectrometry was established. The determination coefficients of the calibration curves were all greater than 0.999. The limits of detection were between 0.000 03% and 0.002 94%. The contents of eleven elements in the standard samples of titanium alloy were determined according to the experimental method, the relative standard deviations (RSD, n=11) of determination results were between 0.31% and 4.9%. The absolute value of relative errors (RE) between the determination results and standard values of elements were not more than 8.1%. Three grades of titanium alloy samples were analyzed and compared. The samples were determined according to the experimental method, and the found results were basically consistent with those obtained by YS/T 1262-2018.
Chromium stainless steel has good properties in oxidation resistance and corrosion resistance. The contents of As,Sn,Sb and Pb will affect the plasticity and strength of chromium stainless steel materials, so the detection of As,Sn,Sb and Pb is of great significance for judging the quality of steel. In daily analysis, the atomic absorption spectrometry (AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES) is mostly used for measurement. However, the above methods have some shortcomings such as complex operation procedure, time-consuming process and limited detection range. In this paper, the determination method of micro/trace As,Sn,Sb and Pb in chromium stainless steel by spark source atomic emission spectrometry was investigated. The calibration curves were prepared using domestic and imported chromium stainless steel standard samples and self-made internal control samples. The pre-burn time and integration time were optimized. It was found that the excitation intensity of As,Sn,Sb and Pb was most stable when the pre-burn time was 9 s and the integration time was 6 s. The interference of elements with the calibration curves was deducted by curvilinear regression. The limit of quantification for As,Sn,Sb and Pb was 0.000 3%,0.001 3%,0.000 5% and 0.000 06% (mass fraction, similarly hereinafter), respectively. The samples of chromium stainless steel with As,Sn,Sb and Pb contents in range of 0.000 4%-0.011% were selected for precision experiments according to the experimental method. The relative standard deviations (RSD, n=10) of determination results were all less than 5%. Five chromium stainless steel standard samples and three chromium stainless steel samples were selected for accuracy experiments, and the results showed that the measured values of this method were consistent with the standard value/certified value of the standard samples and those obtained by the graphite furnace atomic absorption spectrometry.
At present, the determination of tantalum pentoxide and niobium pentoxide in tantalum-iron and niobium-iron concentrate usually adopts gravimetric method, while the determination of titanium dioxide adopts diantipyrylmethane spectrophotometry or inductively coupled plasma atomic emission spectrometry (ICP-AES). However, these determination methods have long operation procedures, and the sample cannot be determined simultaneously in once sample preparation, which hardly meet the requirements of detection efficiency. In this study, the determination method of tantalum pentoxide, niobium pentoxide and titanium dioxide in tantalum-iron and niobium-iron concentrates by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) with fusion sample preparation was established. The working parameters of the instrument were optimized by experiments, and the melting temperature and time were studied. It was found that the optimal melting temperature and time were 1 100 ℃ and 10 min, respectively. The fluidity of melt flow good, the test piece was uniform without non-melt. In addition, the effects of internal standard correction and direct determination on the linear correlation coefficient of the calibration curve were compared. The results showed that the linear correlation coefficient of the calibration curve of tantalum pentoxide was significantly improved after correction with hafnium dioxide. There was no significant difference in the linear correlation coefficient of the calibration curve using internal standard and direct determination for niobium pentoxide and titanium dioxide. The contents of tantalum pentoxide, niobium pentoxide and titanium dioxide in three tantalum-iron and niobium-iron concentrate samples were determined according to the experimental method. The relative standard deviations (RSD, n=9) of determination results were less than 3%. The components of tantalum-iron and niobium-iron concentrate samples were determined by this method and the chemical wet method, and there was no significant difference in the results.
The chemical composition of refined slag in iron and steel metallurgical enterprises is generally determined by X-ray fluorescence spectrometry (XRF). Although there are national standard methods for reference, the analysis speed cannot meet the production requirements in front of the smelting furnace. In this study, the sample was prepared by pressed powder pellet method. The grinding time was 40 s, the pressure was 40 MPa, and the holding time was 40 s. Eight self-made refined slag samples were selected as calibration samples to establish the calibration curve. The method for determination of eight major components in refined slag, including silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron, was established by XRF with pressed powder pellet sample preparation. The linear correlation coefficients of calibration curves of components were all greater than 0.98. The contents of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron in the refined slag sample were determined according to the experimental method. The relative standard deviations (RSD, n=11) of determination results were all less than 0.06%. Three refined slag samples were determined according to the experimental method, and the measured results were consistent with those obtained by the chemical wet methods (where, the content of silicon dioxide was determined by perchloric acid dehydration gravimetry-silicon molybdenum blue spectrophotometry; the contents of aluminum oxide and calcium oxide were determined by EDTA titration; the contents of magnesium oxide, phosphorus pentoxide, manganese oxide, titanium dioxide, and iron were analyzed by inductively coupled plasma atomic emission spectrometry).
Spectrophotometry is adopted for the determination of thiocyanate in chromium (Ⅵ) containing cyanide residue. When the thiocyanate is leached with sodium hydroxide solution, chromium (Ⅵ) will be also leached, which causes interference with the determination of thiocyanate. In this study, the method for eliminating the interference of chromium (Ⅵ) was discussed. In experiments, chromium (Ⅵ) was reduced to chromium (Ⅲ) by adding 0.1 g of ferrous sulfate under weakly acidic condition at pH=5. Then 0.1 g of zinc sulfate was added for co-precipitation under weakly basic condition at pH=8. After boiling by heating for 10 min, the precipitation was complete and the adsorbed thiocyanate was fully released. The thiocyanate was totally in the leaching solution, thus eliminating the interference of chromium (Ⅵ). The content of thiocyanate was measured by spectrophotometry. Consequently, the method for the determination of thiocyanate in chromium (Ⅵ) containing cyanide residue by spectrophotometry was established. The contents of thiocyanate in three chromium (Ⅵ) containing cyanide residue samples were determined according to the experimental method. The relative standard deviations (RSD, n=6) of determination results were less than 3%, and the spiked recoveries were between 97% and 102%.
The accurate determination of potassium content in tungsten-rhenium alloys is of great significance for studying the high-temperature properties of materials and the room temperature plasticity after recrystallization. In this study, the sample was dissolved with nitric acid and hydrofluoric acid. The cesium chloride solution was added as an ionizing agent to suppress the ionization of potassium and eliminate ionization interference. A method for the determination of potassium with mass fraction of 0.000 5%-0.010% in tungsten-rhenium alloy by flame atomic absorption spectrometry (FAAS) was established. The interference test showed that tungsten or rhenium matrices had a significant impact on the measurement. Therefore, the matrix matching method was used to draw calibration curves to overcome the matrix effect of tungsten or rhenium. The influence of other elements in the sample, except for the matrix tungsten and rhenium, on the determination could be ignored. The experimental results showed that the correlation coefficients of calibration curves for sample WRe5 and WRe25 were 0.999 8 and 0.999 6, respectively, and the characteristic concentrations of potassium were both 0.007 6 μg/mL. The precision tests were conducted using four tungsten-rhenium alloy samples with different potassium content levels according to the experimental methods, and the relative standard deviations (RSD, n=9) of the measurement results ranged from 1.7% to 3.1%. The contents of potassium in WRe5 and WRe25 tungsten-rhenium alloy samples were determined according to the experimental method. Different amounts of 1 μg/mL potassium standard solution were added for the spiked recovery tests, with recovery rates ranging from 98% to 104%. The inductively coupled plasma mass spectrometry (ICP-MS) was used for method comparison and validation. The t-test analysis showed that there was no significant difference between the ICP-MS and the experimental method.
Monthly, Started in 1981 Sponsored by:
China lron & Steel Research Institute Group
The Chinese Society for Metals Managed by:
China lron and Steel Association Editor in Chief: JlA Yunhai ISSN: 1000-7571 CN: 11-2030/TF Postal Code: 82-157 Code No. 1579M
