To explore the dissolution effect of aluminum inclusions in different forms in steel materials by microwave digestion,aluminum oxide,spinel and mullite were selected in this study to simulate aluminum inclusions in steel.The content of aluminum was determined by inductively coupled plasma mass spectrometry(ICP-MS) and inductively coupled plasma atomic emission spectrometry(ICP-AES).The effect of different digestion methods on aluminum recovery was systematically evaluated.The temperature and time in microwave digestion were optimized.The results showed that the three methods,including open digestion,HCl-HNO₃ microwave digestion, and HCl-HNO₃-HF atmospheric pressure sealed digestion,all failed to achieve satisfactory dissolution of aluminum oxide,spinel and mullite inclusions.However,the dissolution efficiency of all aluminum inclusions was significantly improved when HCl-HNO₃-HF microwave digestion method was used.Moreover,the dissolution effect could be further enhanced by increasing the digestion temperature and prolonging the digestion time.The dissolution effect of aluminum inclusion simulated sample with different aluminum contents was investigated under the optimized microwave digestion conditions,i.e., 180 ℃ and 40 min.The results showed that aluminum oxide and mullite inclusions could be well dissolved,and the recoveries of aluminum were 83%-99% in addition range of 0.4-5 mg (the theoretical mass fraction of aluminum in inclusion state was 0.15%-2.64%).Although the spinel inclusion was hardly decomposed,the recoveries of aluminum could also reach 90% when the addition amount was 1 mg (the theoretical mass fraction of aluminum in inclusion state was 0.41%),indicating that the proposed method could effectively dissolve the aluminum inclusions in steel materials.The simulated sample for digestion tests was prepared using coarse aluminum oxide powder(with average particle size of 100 μm),coarse spinel powder (74 μm),and mullite sand (150 μm).The results of digestion experiment demonstrated that the proposed method exhibited high effective efficiency in digestion of large-sized aluminum inclusion particles.The certified reference materials/reference materials of steel and alloy were used for method validation.The measured results of total aluminum by ICP-MS were consistent with the certified/standard values,and the relative standard deviation(RSD) was not more than 5.0%.

The revision of ISO 15355(Steel and iron-Determination of chromium content-Indirect titration method) has been approved by International Organization for Standardization/Technical Committee 17/Subcommittee 1-Steel/Methods of Determination of Chemical Composition(ISO/TC17/SC1) at the 34th meeting in 2024.This revision project intended to analyze the international co-operation test data of ISO 15355 using ISO 5725 and ISO/TR 21074,recalculate the precision of the method,and evaluate its scope of application,so as to meet the current analytical requirements and reflect the actual level of analytical technology.This paper mainly introduces the revisions involved in the amendment process of the international standard ISO 15355.Based on ISO 5725,the international co-operation experimental data of ISO 15355 were re-evaluated using ISO/TR 21074:2016.The results could better reflect the current precision level of determining chromium content in steel by alkali fusion-indirect potentiometric titration method.Compared with the assessment in ISO/TR 21074:2016,the differences in data processing in CEN/TR 10345:2013 could lead to different exclusion results for the co-operation experimental data.Furthermore,by comparing the precision data of ISO 4937:2024 and ISO 15355,the influence of two different sample dissolution methods,i.e.,acid dissolution and alkali fusion,on the precision was evaluated.The results showed that there was little difference in overall accuracy between acid dissolution and alkali fusion method.In terms of repeatability,however,the alkali fusion method had better consistency.

The morphology and size of sulfide inclusions in free-cutting steel have a significant impact on the cutting performance of the steel.Currently,there is a lack of effective methods for the evaluation of sulfide inclusions in free-cutting steel in China,which affects the determination of cutting performance and quality of free-cutting steel.In this study,based on the evaluation standards,including the national standard GB/T 10561-2023,the German standard SEP 1572-2019,the French standard NF A04-108-1986,and the newly formulated industry standard in China YB/T 6458-2026,for sulfides in free-cutting steel at home and abroad,4 methods for evaluating sulfides in free-cutting steel were introduced.The evaluation process,content,and results of each method were introduced.The methods adopted in these 4 standards were different.In national standard GB/T 10561-2003,the grade of various types of inclusions is evaluated based on their length and width,and the inclusions include sulfides,aluminum oxide,silicates and oxides.This method is not applicable for the evaluation of sulfide inclusions in free-cutting steel.German standard SEP 1572-2019 is a set of 26 spectra arranged in rows and columns based on the length,width,and area of sulfides.Comparison and image analysis methods are used for evaluation,and the results are represented by K.Z indicating the rows and columns.In French standard NF A04-108-1986,the sulfides are divided into two morphologies,i.e.,spindle-shaped and stringer-shaped.The sulfide inclusions are classified into 9 levels from A to I for comparative evaluation based on the ratio of spindle-shaped to stringer-shaped inclusions.The newly formulated sulfide industry standard in China YB/T 6458-2026 includes the grade assessment of vertical sulfide inclusions and the distribution uniformity assessment of horizontal sulfide inclusions.Wherein the grade assessment of vertical sulfide inclusions is developed based on the adoption of German standard SEP 1572-2019,while the distribution uniformity assessment of horizontal sulfides adopts Delaunay triangulation method.In this paper,some examples were provided to illustrate the image analysis method in German standard and the evaluation method for the transverse distribution uniformity of sulfides in the domestic industrial standard which were relatively difficult to understand,so as to facilitate their better application.Through the description and introduction of various methods,it is hoped that appropriate sulfide evaluation methods can be adopted in practice.This article provided useful reference and support for the research and development of free-cutting steel products.

In response to the demand for trace detection of 31 kinds of persistent chlorinated organic compounds(including highly toxic and refractory pollutants) such as Dechlorane Plus,Chlordecone,Dicofol and Methoxychlor in environmental water samples,a method for the analysis and determination of 31 persistent chlorinated organic compounds in water by gas chromatography-tandem mass spectrometry(GC-MS/MS) with dispersive liquid-liquid extraction and solid phase extraction(SPE) purification was established in this study.The pH of water sample was adjusted with phosphoric acid(1+1) to pH≤2.After adding surrogate,sodium chloride,matrix modifier(isopropanol),the dispersive liquid-liquid extraction was conducted using dichloromethane as the solvent.The organic phase was collected and dehydrated with anhydrous sodium sulfate.The organic phase was concentrated and the solvent system was transferred to n-hexane followed by purification with Florisil-MgSO₄-graphitized carbon black-Cu(Florisil-MgSO₄-GCB-Cu) mixed solid phase extraction column.Then,it was eluted with 12 mL of n-hexane-acetone-isopropanol(V/V/V=90∶10∶2) to achieve the efficient enrichment and low matrix residue of persistent chlorinated organic compounds.The persistent chlorinated organic compounds were analyzed using chromatographic column with program temperature.In addition,after continuous detection of 50 samples,the degradation rates of Endrin and p,p′-DDT were 11.8% and 4.60%,respectively.The multiple reaction monitoring(MRM) mass spectrometry mode was used for qualitative and quantitative analysis of persistent chlorinated organic compounds.The experimental results showed that the linear correlation coefficient(r) of calibration curves for 31 persistent chlorinated organic compounds was all higher than 0.999 in mass concentration range of 5-250 μg/L.The limit of detection of this method was 0.002-0.004 μg/L,and the limit of quantification was 0.008-0.016 μg/L.For blank water samples spiked at 3 mass concentrations(0.010,0.10 and 0.20 μg/L),the relative standard deviation(RSD,n=7) of determination results was 1.1%-15.7%,and the recovery was 73.4%-119%.In the test of water body samples,the relative deviations between two parallel samples were 0.0%-18.3%,which were all lower than 20%,the recovery was 74.7%-117%.The proposed method could meet the efficient screening and accurate analysis of large-scale water quality samples in environmental geological survey,and it provided a reliable standardized detection scheme for the monitoring and risk assessment of pollutants in surface water and groundwater.

The traditional detection methods for the key quality indices of petroleum coke (including ash content,volatile matter,fixed carbon and calorific value) are complicated and time-consuming.This study aimed to develop a rapid and synchronous detection method based on Raman spectroscopy combined with partial least squares(PLS) regression.Total 61 petroleum coke samples were collected,and their spectral data were acquired using a confocal Raman spectrometer (532 nm laser).Asymmetric least squares(ALS) was employed for the baseline correction,then the spectral preprocessing was conducted by combining with Z-score standardization.A PLS regression model was established using the preprocessed spectral data as the independent variables and the measured values of 4 quality indices as the dependent variables.The Akaike information criterion(AIC) was innovatively introduced to determine the optimal component number of model,and Monte Carlo cross-validation was used to evaluate the generalization ability and robustness of the model.The established quantitative models exhibited excellent prediction performance.The determination coefficients(R²) of the models for volatile matter,fixed carbon and calorific value reached 0.972,0.987 and 0.953,respectively,while the R² for the ash content model was 0.819.The differences between the predicted values for 3 independent validation samples and those determined by the standard method were all within the allowable range specified by the standard repeatability limit,verifying the reliability of the model.The proposed method required only approximately 20 s for a single test,and it enabled simultaneous multi-index analysis within minutes by combining with model calculation.The efficiency was improved effectively compared to the traditional methods.This study provided a novel technical solution for on-site quality monitoring and rapid detection of petroleum coke sample.

Asbestos,as a filler and associated mineral, is widely present in various fields such as building materials, rubber, pharmaceuticals,and cosmetics. In view of the long-term shortage of domestic certified reference material(CRM) of asbestos, a set of qualitative CRMs of asbestos(GSB 08-4340-2025) was developed in this study. The set included chrysotile,tremolite asbestos, actinolite asbestos,crocidolite,and anthophyllite asbestos.The tests verified that the homogeneity and stability of these asbestos CRMs could meet the requirements for CRMs.The property values and corresponding uncertainties were assigned through collaborative characterization by 8 qualified laboratories.This set of developed CRM can be applied to operator proficiency testing,validation of analytical methods,instrument calibration,and quality supervision,filling the domestic gap in CRMs asbestos.

Lime is a key desulfurizer in ironmaking and steelmaking processes,and its moisture content has a significant influence on the desulfurization efficiency,product quality,and production stability.The traditional moisture detection methods suffer from low efficiency,susceptibility to environmental interference,and poor operational safety,making them difficult to meet the current requirements for efficient and accurate analysis.In this study,a method based on infrared absorption was developed for the determination of adsorbed water and combined water in desulfurizer under the following conditions:the inert atmosphere (N₂);the sample mass was 0.5 g and the purge flow rate was 5 000 mL/min;a two-stage temperature program was set at 105 ℃ for 360 s and 500 ℃ for 780 s.The precision and trueness of the method were systematically evaluated.The results showed that the relative standard deviations(RSD,n=8) of determination results for adsorbed water and combined water in pre-melted desulfurizer and secondary lime desulfurizer ranged from 1.7% to 3.6%.The measured values of certified reference materials were in good agreement with the certified values.It was further confirmed that the moisture mainly existed in the form of adsorbed water and combined water with Ca(OH)₂.Moisture measurements at different time points(Day 2 and Day 7) after sample preparation revealed that CaO in lime desulfurizer easily absorbed moisture,leading to a significant increase in combined water content over time,indicating that the analysis should be completed within 24 hours after sample preparation.The proposed method effectively overcame the drawbacks of traditional methods such as complicated procedures,moisture uptake,and potential safety hazards.It provided a reliable analytical tool for moisture control and process optimization of desulfurizers,showing good prospects for popularization and application.

The size and number of inclusions have a direct influence on the performance and service life of bearing steel.Therefore,the requirements for inclusions in bearing steel are extremely strict.Due to the characteristics of inclusions including small size,complex types,and concealed nature,a single testing method cannot fully characterize their properties.In this study,based on an extreme value statistical model and multi-scale characterization technology,combined with a field emission scanning electron microscope(FESEM) and Aztec inclusion analysis software,three-dimensional quantitative analysis of the composition,morphology,and size of inclusions in bearing steel was realized.Using the extreme value statistical model,the limitation of the visual field in traditional microscopic detection was overcome,and the maximum size inclusions was successfully predicted and verified experimentally.The results showed that the Aztec inclusion analysis software could detect all inclusions on the inspection surface,including nitrides,oxysulfides(complex),sulfides, and oxides. Among them,the oxysulfides(complex) accounted for approximately 60%,and the nitrides accounted for about 30%.By detecting the maximum size inclusions on 24 inspection surfaces of inclusion specimens,the extreme value statistical model predicted that the maximum length of aluminum oxides inclusions at a reversal period of T=1 000 was approximately 226 μm,and the maximum diameter of point inclusions was approximately 40 μm.After actual sampling and verification,the maximum length of aluminum oxides inclusions detected at T=50 was approximately 188 μm,and the maximum diameter of point inclusions was approximately 28.2 μm,which was close to the predicted values of 151.07 μm and 28.77 μm.

Rare earth magnesium ferrosilicon alloy is a commonly used spheroidizing agent,in which magnesium is the main spheroidizing element.The accurate determination of magnesium content is of great significance for the research,development and application of this product.The sample was decomposed with nitric acid and hydrofluoric acid,followed by the addition of perchloric acid and heating at low temperature to fume until nearly dry.After dissolution with hydrochloric acid(1+1),barium and strontium were separated by sulfate precipitation.Then excess sodium hydroxide solution was added to the filtrate to remove aluminum and phosphorus by filtration.The precipitate was dissolved,and ammonium chloride was added as an electrolyte.Rare earths,iron,manganese and other interfering elements were separated by ammonia precipitation.The content of calcium was titrated with EDTA standard titration solution at pH>12 using triethanolamine as masking agent and calcium red as indicator.The total content of calcium and magnesium was titrated at pH≈10 using chromium black T as indicator.Then the magnesium content was calculated by the subtraction method.The analysis method for the determination of magnesium in rare earth magnesium ferrosilicon alloy by EDTA titration was established,with a determination range of 5.00%-30.00%.The synthetic samples of rare earth magnesium ferrosilicon alloy with low,medium and high magnesium contents were analyzed according to the experimental method.The relative standard deviations(RSD, n=11) were between 0.33% and 2.1%,and the recoveries were between 98.8% and 101.6%.Inductively coupled plasma atomic emission spectrometry(ICP-AES) was used for method comparison.The results showed that the measured values of two methods were consistent,indicating that the proposed method was suitable for the quantitative analysis of magnesium in such alloys.

Phosphorus is a harmful element in rare earth fluorides.The accurate determination of phosphorus content is of great significance for guiding smelting process.In this study,the content of phosphorus in rare earth fluorides was determined by bismuth phosphomolybdate blue spectrophotometry.The effects of different sample decomposition methods on the determination results were systematically investigated.The testing conditions such as system acidity,coloring time and temperature,and absorption spectra were optimized.The interference of coexisting elements was also evaluated,including Al,Mg,Ca,Mn,As,Ti,Cr,Ni,Co,V,Cu,Mo,Sr,Ba,Zn and rare earth elements.The results showed that the sample could be completely decomposed using 3 mL of nitric acid and 5 mL of perchloric acid.The hydrolysis of rare earth elements and bismuth could be effectively inhibited by controlling the pH of color developing solution below 0.1.After coloring at (25±5) ℃ for 20 min,the ascorbic acid could reduce the yellow phosphorus-bismuth-molybdenum ternary heteropolyacid to stable blue complex which had maximum absorption peak at 700 nm.The interference of arsenic could be eliminated by adding 5.0 mL of sodium thiosulfate-anhydrous sodium sulfite mixed solution.The calibration curve of phosphorus showed good linearity within the linear range,and the correlation coefficient was r=0.999 6.The apparent molar absorptivity was ε=1.3×10⁴ L·mol^-1·cm^-1.The limit of detection of this method was 0.000 6%(mass fraction,similarly hereinafter),and the quantitation range was 0.002%-0.200%.The proposed method was applied for the determination of phosphorus in 5 rare earth fluoride samples.The relative standard deviations(RSD,n=8) of determination results were all less than 3%,and the recoveries were between 97.9% and 101.4%.The measured results of 3 rare earth fluoride samples were basically consistent with those obtained by inductively coupled plasma atomic emission spectrometry(ICP-AES).

To address the problem of low efficiency caused by the reliance on single-element wet chemical methods in industrial standard methods(YS/T 358-2011 series) for the determination of titanium,tin,and manganese in tantalite and columbite concentrates,a method for the simultaneous determination of titanium,tin and manganese by inductively coupled plasma optical emission spectrometry(ICP-OES) was established in this study.The procedures for sample decomposition were optimized.It was found that the pretreatment route consisting of alkali fusion,hydrofluoric acid complexation,and hydrochloric acid acidification(reagent dosages:4 g of sodium peroxide,5 mL of hydrofluoric acid,and 35 mL of hydrochloric acid) could achieve efficient co-dissolution of titanium,tin,and manganese.The method validation results showed that the linear correlation coefficients of calibration curves for all elements were greater than 0.999,and the limits of detection of this method ranged from 0.001 1% to 0.005 9%.The content of titanium,tin,and manganese in tantalite and columbite concentrates was determined according to the experimental method.The relative standard deviations(RSD, n=11) of determination results were less than 3%,and recoveries were between 99% and 101%.The contents of titanium,tin and manganese in tantalite and columbite concentrates were determined separately by the proposed method and the industrial standard methods(titanium:YS/T 358.2-2011 Diantipyrylmethane spectrophotometry;tin:YS/T 358.10-2011 Potassium iodate titration;manganese:YS/T 358.11-2011 Atomic absorption spectrometry).A comparison of the results was conducted.The F-test and t-test results demonstrated that there was no significant difference between the two methods.

With the increasing number of high value,high precision large-scale instrument and equipment in universities in China,how to achieve their scientific management,efficient operation,and enhanced open sharing has become a key issue affecting the efficiency of scientific research output,which has attracted extensive attention from universities.At present,some universities still have deficiencies in the management and operation of sophisticated instrument and equipment,mainly including a lack of management experience,high maintenance costs,and a low level of open sharing.In this study,the focused ion beam(FIB) system was selected as an example.Based on the management practice of the State Key Laboratory for Mechanical Behavior of Materials in recent years,this paper systematically summarized the management experience of such high precision instrument from the aspects of the construction of operation and management systems,user training for independent operation,establishment of equipment operation archives,improvement of independent maintenance capabilities,and professional development of equipment managers.This study aimed to summarize the existing practices,identify the current problems,and provide a reference for laboratories to further improve the scientific and efficient management and operation of instrument and equipment.

A significant systematic bias exists between the aluminum chloride gravimetry and X-ray fluorescence spectrometry(XRF) in the determination of Al₂O₃ content in silicon-containing complex aluminum electrolyte.This study revealed the interference mechanism that impurity phases such as SiO₂,Fe₂O₃,and TiO₂ were hardly dissolved in AlCl₃ solution and underwent heterogeneous coprecipitation with Al₂O₃.The experimental results showed that the total mass fraction of impurity phases reached 31.14%,leading to systematically higher results by the gravimetry compared with XRF.Based on this interference mechanism,a combined XRF-gravimetry correction model was proposed.The aluminum content in the precipitate obtained after Al₂O₃ dissolution was accurately determined by XRF.After conversion according to the stoichiometric relation(the conversion factor between Al and Al₂O₃ was 1.889 5),the true Al₂O₃ content in sample could be obtained.Then the proposed method was validated by the analysis of silicon-containing complex aluminum electrolyte.This model effectively eliminated the systematic error caused by co-precipitation,and controlled the detection error of Al₂O₃ content within 0.1%.It overcame the interference from variable chemical forms of impurity phases,and significantly improved the accuracy and applicability of traditional gravimetry for Al₂O₃ analysis in high-silicon complex aluminum electrolyte system.