Impurities In Alloys Research Articles

Preparation of low-oxygen Ti–Al alloy by sustainable recovery of spent SCR catalyst

The wide spread application of NH3-selective catalytic reduction (NH3-SCR) process has led to the accumulation of large amounts of spent SCR catalyst. In this study, Al reduction–electromagnetic directional crystallization was used to recycle Ti, W, and V from spent SCR catalyst to prepare W- and V- containing TiAl alloys. The effects of the slag composition, reaction time, and amount of reductant added on the recovery ratios were investigated. The maximum recovery ratios of 94.16 %, 81.85 %, and 98.14 % for Ti, W, and V, respectively, were achieved at a reaction time of 60 min, addition of 45 wt.% Al, and CaO / Al2O3 ratio of 2 / 3. Furthermore, directional crystallization was performed on Ti–Al alloy under different atmospheres (99.99 % Ar or 90 % Ar + 10 % H2 gas) to investigate their effects on deoxygenation. 90 % Ar + 10 % H2 gas could effectively remove O from the Ti–Al alloys. Si and P impurities were enriched at the bottom of the alloy and Fe impurities at the top. The Ca and Mg impurities contents are approximately 50 and 10 ppmw, respectively, and S was removed difficultly. The total impurities content of the resulting W- and V- containing TiAl alloys were less than 1.85 %. The entire process is low-carbon and environmentally friendly.

The effect of phosphorus content in copper alloys used for crystallisers of continuous casting machines

One of the key elements defining the technical level and operational capabilities of continuous casting machines (CCM) is the complex of physico-mechanical properties of copper or copper alloys used in its production. The paper provides a comprehensive assessment of the possibility of obtaining high-quality copper plates for CCBC crystallizers based on domestic technologies and equipment using refined copper. Special attention was paid to the need to optimize the chemical composition of the copper alloy within a narrower range of chemical element values. The analysis of the research shows that currently used copper alloys for CCM crystallizer manufacturing have a wide range of fluctuations in the main operational properties, namely thermal conductivity (260-390 W/(m·K)) and solidification temperature (250-700 °C). However, most of the alloys used have narrower fluctuation limits for acceptable values, constituting 340-390 W/(m·K) for thermal conductivity and 300-370 °C for solidification temperature, significantly depending on the impurity content in the copper alloy. Generalizing graphical dependencies, it should be assumed that the rational phosphorus content in the alloy is in the range of 40-120 ppm. In this case, the thermal conductivity of the alloy will be in the range of 370-400 W/(m·K), the solidification temperature will be 410-440 °C, and the recrystallization start temperature will be 370-400 °C. Moreover, such a phosphorus content interval is technologically feasible to maintain during billet casting. It is also shown that normalization annealing after cold deformation in the temperature range of 320-350 °C is capable of increasing the thermal conductivity of the alloy by 1-2 %. As a result of the conducted research, optimal limits of phosphorus content in fire-refined copper were established, ensuring the level of its physico-mechanical properties not lower than the indicators characteristic of alloys obtained from cathode copper. However, besides phosphorus, other alloy impurities, the content of which differs from the values characteristic of alloys obtained from cathode copper, may affect the properties of the material made from refined copper. Therefore, further research will focus on studying their complex impact on the physico-mechanical properties of refined alloys.

Analyzing the effect of iron and silicon impurities in 5005A alloy on the appearance of anodic sheet coatings

Analyzing the effect of iron and silicon impurities in 5005A alloy on the appearance of anodic sheet coatings

Effects of Alloying Elements on the Dissolution and Precipitation Behaviour of Fe in Mg-Al Alloy Melts

It is necessary to strictly control the iron (Fe) impurity in Mg-Al alloys to guarantee good corrosion resistance and mechanical properties. In this work, the effects of alloying elements and temperatures on the solubilities of Fe in the Mg-Al-based alloy melts (Mg-rich liquid phases) at 963–1033 K were studied by combining the in situ sampling method for the high precision solution values and the multiple regression numerical analysis method for the feature analysis. The solubilities of Fe in Mg-xAl (x = 1 and 3 wt.%) alloy melts could be significantly reduced by adding the yttrium (Y) or manganese (Mn) elements. However, the solubilities of Fe in Mg alloy melts were not in a monotonous relationship with the contents of the alloying elements in the Mg alloys. For the addition of Mn or Y, the lowest solubilities of Fe presented in the Mg-rich liquid phases were for the Mg-xAl alloys with the addition of 2 wt.% Mn or 1 wt.% Y, respectively. Additionally, the Fe-containing precipitations in the related systems were analysed and the Fe was mainly combined with Mn or Y and precipitated, which contributed to the removal of Fe from the Mg melt. The present study provides fundamental thermodynamic information regarding Mg-Al-Fe based systems and the design principle for the removal of Fe in Mg alloys.

Defect-Free Few-Layer M4 C3 Tx (M=V, Nb, Ta) MXene Nanosheets: Synthesis, Characterization, and Physicochemical Properties.

High-quality few-layer M4 C3 Tx (M=V, Nb, Ta) MXenes are very important for applications and are necessary for clarifying their physicochemical properties. However, the difficulty in etching for themselves and the existence of MC/MC1-δ and M-Al alloy impurities in their M4 AlC3 precursors seriously hinder the achievement of defect-free few-layer M4 C3 Tx (M=V, Nb, Ta) MXenes nanosheets. Herein, three different defect-free few-layer M4 C3 Tx (M=V, Nb, Ta) nanosheets are obtained by using a universal synthesis strategy of calcination, selective etching, intercalation, and exfoliation. Comprehensive characterizations confirm their defect-free few-layer structure feature, large interlayer spacing (1.702-1.955nm), types of functional groups (-OH, -F, -O), and abundant valance states (M5+ , M4+ , M3+ , M2+ , M0 ). M4 C3 Tx (M=V, Nb, Ta) free-standing films obtained by vacuum filtration of few-layer M4 C3 Tx inks show good hydrophilia, high thermostability, and conductivity. A roadmap on synthesis of defect-free few-layer M4 C3 Tx (M=V, Nb, Ta) nanosheets are proposed and three key points are summarized. This work provides detailed guidelines for the synthesis of other defect-free few-layer MXenes nanosheets, but also will stimulateextensive functional explorations for M4 C3 Tx (M=V, Nb, Ta) MXenes nanosheets in the future.

High-Pressure Synthesis of Cubic ZnO and Its Solid Solutions with MgO Doped with Li, Na, and K.

The possibility of doping ZnO in its metastable rock salt structure with Li, Na, and K intended to act as acceptor dopants was investigated. For the first time, MgxZn1-xO alloys and pure ZnO with a rock salt structure doped with Li, Na, and K metals was obtained by high-pressure synthesis from pure oxides with the addition of carbonates or acetates of the corresponding metals as dopant sources. Successful stabilization of the metastable rock salt structure and phase purity were confirmed by X-ray diffraction. Transmission electron microscopy was used to study the particle size of nanocrystalline precursors, while the presence of Li, Na, and K metals in rock salt ZnO was detected by electron energy-loss spectroscopy and X-ray photoelectron spectroscopy in MgxZn1-xO alloys. Electron paramagnetic resonance measurements revealed the acceptor behavior of Li, Na, and K dopants based on the influence of the latter on native defects and natural impurities in ZnO-MgO alloys. In addition, diffuse reflectance spectroscopy was used to derive band gaps of quenched rock salt ZnO and its alloys with MgO.

Enrichment and separation behaviors of impurities from stripped copper wire with super-gravity fields

Supergravity technology is an efficient method to remove trace impurities and recycle valuable components from secondary sources. This study investigated the enrichment and separation behaviors of impurities from simulated Cu alloys that based on the typical impurity compositions (such as Pb, Fe, Sn, Al, and inclusions) of waste stripped copper wire using supergravity technology. After supergravity enrichment, nonmetallic inclusions and Fe impurity were concentrated in the top of the sample, and the enrichment degree positively correlated with the gravity coefficient. The low-melting-point impurities in Cu alloys were separated by supergravity. Improving the gravity coefficient and temperature benefited the removal of Pb and Sn but had negative influence on the recovery of Cu. Ultimately, the removal rates of Fe, Sn, and Pb were 79.1%, 39.8%, and 74.4%, respectively, and the recovery of Cu was 91.2% under the optimal conditions. Based on these results, supergravity technology is feasible for purification of Cu alloy and achieves good application. It has provided theoretical foundation for recycling of high purity copper and also pointed out a green and efficient way for recycling waste stripped copper wire that can improve resource utilization and prevent environmental damage.

Copper-loaded chitosan coating for improved in-vitro corrosion resistance and endothelialization of magnesium alloy stents

For degradable magnesium alloy stents, excellent corrosion resistance and rapid endothelialization are two essential properties. In this paper, we plan to use a copper-loaded chitosan coating to accelerate the endothelialization process of the stent, which not only improves the biocompatibility of the magnesium alloy stent, but also its corrosion resistance by improving the service environment in vivo. Copper is an impurity in magnesium alloys, so how copper-containing coatings affect the corrosion resistance of magnesium alloy stents is the focus of this paper. The corrosion properties of the material were characterized by electrochemical experiments, immersion experiments, and in vitro cellular experiments characterized the effect of the copper-loaded coating on endothelial cells. The results showed that the Icorr of the copper-loaded chitosan coated sample and the Icorr of the unloaded copper chitosan coated sample were both in the order of 10−8, and the decrease of the corrosion resistance of the magnesium alloy by the copper-containing chitosan composite coating was not significant, and it still had a protective effect on the magnesium alloy substrate. During the immersion process, magnesium and copper ions were slowly released, followed by the hydrogen released. In addition, the weight loss rate of different coated samples presented the tendency of slower at inital, faster at last, and the weight loss rate of 0.041% for the copper-loaded chitosan coated sample was not significantly different from that of 0.035% for the unloaded copper coating group, after 28 days of immersion. The in vitro degradation products of the copper-loaded composite coating on the surface of magnesium alloy were also analyzed by XRD and EPMA, which included Mg(OH)2, Mg3(PO4)2 and Ca3(PO4)2; in addition the degradation process was analyzed. The cellular experiments results showed that the copper-loaded magnesium alloy had a proliferation rate of 243.0% for endothelial cells, which indicated that the copper-loaded coating could endow magnesium alloy stent a good biofunctional properties.

Acceptable Concentrations of Cu and Ni in Corrosion Resistance of Mg–6 mass% Zn Alloy

Cu and Ni impurities in Mg alloys are deleterious contaminants that reduce the corrosion resistance of the alloy. Mg2Cu and Mg2Ni precipitates can cause significant anodic dissolution of the Mg matrix, owing to their potential difference. Suppression of these phases can prevent the deterioration of corrosion resistance. The neutralization of these impurities through the formation of Mg–Zn intermetallic phases has been studied, because the atomic radii of Cu and Ni are similar to that of Zn. As a result, the MgZn2 phase may precipitate during the rapid cooling that occurs during the solidification of the Mg–6 mass% Zn alloy, and introduce substitutional impurity atoms in the crystal lattice. Mg(Zn, Cu)2 and Mg(Zn, Ni)2 phases can be formed instead of Mg2Cu and Mg2Ni, in the presence of both of Zn and these impurities. The microstructures and corrosion properties of the Mg–6 mass% Zn alloy with various Cu or Ni concentrations are investigated in this work. The Cu and Ni impurities are concentrated into MgZn2 phase in the Mg–6 mass% Zn alloy without Mg2Cu or Mg2Ni formation when the concentrations of these impurities are within acceptable limits. Consequently, the corrosion rate of the Mg–6 mass% Zn alloy with 1.4 mass% Cu or 0.25 mass% Ni is almost the same as that of the alloy without Cu and/or Ni contaminations.

Recycled Aluminium Alloys and their Models: Role and Behaviour of Alloying Elements during Alkaline Etching

Alkaline etching is a common pretreatment for aluminum surfaces. Etching behavior was compared between an alloy based on post-consumer scrap (PCS) and several model alloys of rolled AA3005 and extruded AA6060 with systematically varied amounts of Mn, Cu and Ni. Analysis of concentrations of alloy elements in the etching solution by inductively coupled plasma mass spectrometry (ICP-MS) shows that significant fractions of the investigated elements Cu, Fe, Mg, Mn, Ni, and Zn dissolve. Surface analysis of samples in different stages of the etching process show (i) an increase in oxide layer thickness with etching time, (ii) an enrichment of important alloy elements and impurities (Cr, Cu, Fe, Mg, Mn, Si) near the metal/oxide interface, and (iii) the deposition of Mg, Fe, Si-containing aluminum hydroxide on the surface. A comparison with open circuit potential measurements and time-resolved electrochemical polarization resistance measurements enables a detailed analysis of the etching mechanism. The aluminum dissolution rate during etching is limited by the transport of species through the oxide precursor layer, thus is potential-independent. Differences in etching rates between different alloy classes, evidenced by mass loss measurements, are related to differences in the cathodic or anodic reaction mechanisms (hydrogen evolution or metal dissolution) during etching.

The influence of surface Fe on the corrosion of Mg

Iron is a common impurity in magnesium alloys, and is acknowledged to accelerate Mg corrosion, contributing to Mg’s poor corrosion resistance. However, an atomistic understanding of this acceleration effect is still incomplete. Here we use Density Functional Theory simulations performed with the Quantum Espresso package to investigate several Fe/Mg models, calculating the associated work functions, atomic charges, and H and Fe absorption energies. Compared with a pure Mg slab, we find that Fe’s existence increases the work function and decreases the H adsorption energy. Furthermore, a general trend is observed that the Fe absorption energy decreases with increasing interaction between Fe atoms on the Mg substrate. Based on these results, a mechanism based on charge redistribution is put forward to explain how Fe accelerates the corrosion of Mg. Our findings provide insight into Mg’s corrosion process at the atomic level that might inform future measures to prevent corrosion.

Impurities in commercial titanium dental implants – A mass and optical emission spectrometry elemental analysis

ObjectiveTitanium (Ti) is considered bioinert and is still regarded as the “gold standard” material for dental implants. However, even ‘commercial pure’ Ti will contain minor fractions of elemental impurities. Evidence demonstrating the release of Ti ions and particles from ‘passive’ implant surfaces is increasing and has been attributed to biocorrosion processes which may provoke immunological reactions. However, Ti observed in peri-implant tissues has been shown to be co-located with elements considered impurities in biomedical alloys. Accordingly, this study aimed to quantify the composition of impurities in commercial Ti dental implants. MethodsFifteen commercial titanium dental implant systems were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES). ResultsThe elemental composition of implants manufactured from commercially pure grades of Ti, Ti-6Al-4V, and the TiZr alloy (Roxolid) conformed to the respective ISO/ASTM standards or manufacturers´ data (TiZr/Roxolid). However, all implants investigated included exogenous metal contaminants including Ni, Cr, Sb, and Nb to a variable extent. Other contaminants detected in a fraction of implants included As and the radionuclides U-238 and Th-232. SignificanceAlthough all Ti implant studies conformed with their standard compositions, potentially allergenic, noxious metals and even radionuclides were detected. Since there are differences in the degree of contamination between the implant systems, a certain impurity fraction seems technically avoidable. The clinical relevance of these findings must be further investigated, and an adaptation of industry standards should be discussed.

An end-to-end computer vision methodology for quantitative metallography

Metallography is crucial for a proper assessment of material properties. It mainly involves investigating the spatial distribution of grains and the occurrence and characteristics of inclusions or precipitates. This work presents a holistic few-shot artificial intelligence model for Quantitative Metallography, including Anomaly Detection, that automatically quantifies the degree of the anomaly of impurities in alloys. We suggest the following examination process: (1) deep semantic segmentation is performed on the inclusions (based on a suitable metallographic dataset of alloys and corresponding tags of inclusions), producing inclusions masks that are saved into a separated dataset. (2) Deep image inpainting is performed to fill the removed inclusions parts, resulting in ‘clean’ metallographic images, which contain the background of grains. (3) Grains’ boundaries are marked using deep semantic segmentation (based on another metallographic dataset of alloys), producing boundaries that are ready for further inspection on the distribution of grains’ size. (4) Deep anomaly detection and pattern recognition is performed on the inclusions masks to determine spatial, shape, and area anomaly detection of the inclusions. Finally, the end-to-end model recommends an expert on areas of interest for further examination. The physical result can re-tune the model according to the specific material at hand. Although the techniques presented here were developed for metallography analysis, most of them can be generalized to a broader set of microscopy problems that require automation. All source-codes as well as the datasets that were created for this work, are publicly available at https://github.com/Scientific-Computing-Lab-NRCN/MLography.

Study of cluster ions produced from ToF-SIMS analysis of a U-6%Nb target

Cluster ions have been previously observed during time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of metals and metal oxides. Here, we have used ToF-SIMS to investigate cluster ions formed from the hydrocarbon-containing overlayer, the mixed U and Nb surface oxide, and underlying metal of a U-6 %Nb (U6Nb) target. In the overlayer, we observe UxOy+ oxides and U-species likely containing hydrocarbons. In the surface oxide, we observe UO2+, U2O2+, U3O5+, and U4O6+ as the most intense ions for each family of oxide ions containing x U atoms. Nb oxides for NbO1-2- were only observed in negative polarity. In contrast to the oxide, analysis of the underlying U6Nb alloy resulted in repeating units of Un+, Un(Nb)+, and Un(Nb2) + ions for n = 3–11 as the highest intensity ions for each family of ions containing n U atoms. Nbn+ clusters were not observed. Un+, Un(Nb)+, and Un(Nb2)+ clusters containing C- and O-species were observed and were likely produced from soluble C or O species or precipitates known to be present in U6Nb.Cleaning of the surface oxide with varying ion current density of 25 keV 69Ga+ to perturb local chemistry did not influence ion distributions and suggests that observed high intensity ions are stable lattice fragments ejected from the surface oxide. Cleaning of the underlying alloy with varying ion current density increased the content of Un+, Un(Nb)+, or Un(Nb2)+ clusters in comparison to the C and O-containing species. These results suggest a different mechanism of cluster ion formation than what was observed in the metal oxide. Preferential sputtering of U from the surface or low local Nb content may also contribute to the enrichment of U in observed clusters. We conclude that cluster ions may be of great value in studying local chemistry, contaminants, and impurities in oxides and alloys.

First-principles study of the interstitial stability and microscopic diffusion mechanism of hydrogen atom in Zr, Ti elemental and ZrTi2 alloys

Hydrogen absorbing materials based on titanium with high hydrogen absorbing capacity such as Ti–Mo, Ti–Zr–V, Ti–Zr and so on have gained significant attention in recent years. It's necessary to optimize and improve the properties of structural materials for studying the behavior of hydrogen impurities in zirconium-titanium alloys. In order to discuss whether hydrogen atoms can stably exist in the interstitial space of Ti–Zr alloy and find the optimal diffusion path of hydrogen atoms in Ti–Zr alloy, we study the hydrogen atom diffusion ability and migration path in Ti–Zr alloy and the change of the formation energy of hydrogen atom at the interstitial defect based on First principles in this paper. Through calculations, it can be concluded that hydrogen atoms tend to occupy the tetrahedral gaps containing only Ti atoms. Furthermore, it's easiest for hydrogen atoms to diffuse between the gaps of the Zr–Zr layer and the best diffusion path for hydrogen atoms in the Ti–Zr alloy is also in the Zr–Zr layer. In general, it's easy for hydrogen atoms to migrate near Zr atoms. The energy expansion barrier of hydrogen atoms between adjacent gaps will be affected by the first neighboring metal atoms, and the first neighboring metal atoms have an inhibitory effect on the diffusion of hydrogen atoms. By comparing the diffusion of hydrogen atoms in Zr, Ti and Zr–Ti alloys, it has been found that the diffusion rate of hydrogen atoms in Zr–Ti alloys is greater than that in Zr and Ti. The above results will provide a theoretical reference for further exploring the microscopic mechanism of hydrogen diffusion in zirconium-titanium alloys.

Plasma Spheroidisation of Irregular Ti6Al4V Powder for Powder Bed Fusion

Metal powders suitable for use in powder bed additive manufacturing processes should ideally be spherical, dense, chemically pure and of a specified particle size distribution. Ti6Al4V is commonly used in the aerospace, medical and automotive industries due to its high strength-to-weight ratio and excellent corrosion resistance properties. Interstitial impurities in titanium alloys have an impact upon mechanical properties, particularly oxygen, nitrogen, hydrogen and carbon. The plasma spheroidisation process can be used to spheroidise metal powder consisting of irregularly shaped particles. In this study, the plasma spheroidisation of metal powder was performed on Ti6Al4V powder consisting of irregularly shaped particles. The properties of the powder relevant for powder bed fusion that were determined included the particle size distribution, morphology, particle porosity and chemical composition. Conclusions were drawn regarding the viability of using this process to produce powder suitable for additive manufacturing.

Archaeological applications of natural gold analyses

Abstract Compositional studies of natural gold usually have a geological focus, but are also important in archaeological provenancing. Both methodologies rely on compositional comparison of two sets of samples, one of which is geographically constrained. Here we describe how experiences in gold characterization resulting from geological studies are relevant to archaeology. Microchemical characterization of polished sections of natural gold identifies alloy compositions, alloy heterogeneity and mineral inclusions. Gold from all deposit types shows Cu and Sn values much lower than those recorded during numerous studies of artefacts. Inclusions in artefact gold include various Cu- and Sn-bearing compounds which indicate specific high temperature reactions that could ultimately illuminate the conditions of (s)melting. The use of LA-ICP-MS to generate a wide range of elemental discriminants for provenance studies may be compromised by alloy adulteration and/or unrepresentative analysis of natural/artefact alloys, which are commonly highly heterogeneous at the micron scale. Geological studies normally characterize only the earliest-formed (hypogene) alloy, whereas archaeology-focused studies should entail analyses of bulk alloy compositions and impurities that may be incorporated during (s)melting. Isotopic-based provenancing alleviates many of these problems but, to date, generates regional rather than locality-specific targets. A dual isotopic–compositional approach is recommended.

Microstructure evolution and mechanical property of quaternary Cu-7%Al-4%Ni-2.5%Mn alloy solidified within ultrasonic field

An intensive field of 20 kHz power ultrasound with various amplitudes was applied during the solidification process of quaternary Cu-7%Al-4%Ni-2.5%Mn single-phase alloy to investigate its dynamic solidification mechanism and mechanical performance improvement. It is found that α(Cu) phase nucleates at small undercoolings and mainly grows along (111) crystalline plane direction into coarse dendrites with developed secondary arms. With the rise of amplitude, ultrasonic wave increases the nucleation rate by improving the wetting effect between alloy melt and impurities and also breaks some growing dendrites into fragments. Once the ultrasonic amplitude reaches the maximum of 15.2 µm, the prominent cavitation effect further increases the nucleation rate by three orders of magnitude, and also leads to the symmetrical distribution of temperature field, solute field and flow field in the solidification front, eventually resulting in the formation of tiny equiaxed α(Cu) grains without any obvious preferred growth orientation, inside which the solute distribution also tends to become uniform. Meanwhile, the compressive yield strength of Cu-7%Al-4%Ni-2.5%Mn alloy is significantly increased by 3 times after ultrasonic solidification. Theoretical analysis indicates that grain strengthening and dislocation strengthening are the two main reinforcement factors induced by power ultrasound.

Accounting for the plasma background radiation influence and calibration curve export in atomic emission spectrometry with CCD-based registration system when determining metal and alloy impurities

This paper is dedicated to development and application of an algorithm allowing determining an accurate actual value of the plasma background radiation under the analytic element line using standard data obtained from emission spectrometer registration system. A unique technique has been developed that allows calibrating spectrometers in the range of small concentration of impurities with two standard samples, which is very relevant for analysis of metals and alloys, powdered samples, ultrapure materials. The paper demonstrates efficiency of this technique when applied to series-produced emission spectrometers manufactured in Russia.

Characterization of Impurities and Inclusions in Ferrochrome Alloy and Their Effects on the Inclusion Characteristics in Stainless Steels

Laboratory scale alloying experiments were carried out by the addition of a commercial low carbon ferrochrome (LCFeCr) alloy to 430-grade ferritic stainless steel. The inclusions in FeCr alloys as well as in the steel samples before and after alloy addition were investigated using an electrolytic extraction (EE) technique. The results show that the Ti content decreases after the FeCr alloy addition. MnCr2O4 inclusions from FeCr alloys are transformed into Ti2O3-Cr2O3 based liquid inclusions and Ti2O3-rich solid inclusions. They are formed due to the reactions between MnCr2O4 and either TiN or dissolved Ti, which needs to be further studied. The ratio of Ti/Al in the steel melt has a direct influence on the evolution of the inclusions. The present study aims to contribute for understanding the impurities in FeCr alloys and their effect on the inclusion characteristics for the stainless steel production.