MnS Particles Research Articles

Rapid detection of bioavailable heavy metals in sediment porewaters using acid-volatile sulfide gel probes

The acid-volatile sulfide (AVS) pool in anoxic sediments is believed to play an important role in the sequestration of heavy metals, forming less soluble mineral sulfides via replacement and coprecipitation reactions. In this study, novel sediment gel probes containing immobilized FeS or MnS particles were evaluated for their ability to concentrate and detect reactive heavy metals in solution. MnS-containing gels were more effective than FeS gels at concentrating most metals in solution external to the gels, but they were more difficult to prepare and use. Copper reacted with FeS in gel probes to form one or more secondary sulfide minerals insoluble in 1 N HCl. The pixel density of digital images of these gels was highly correlated with the concentration of copper in gels and total copper in solution, suggesting a method for rapid screening of bioavailable heavy metals. Copper added to Youghiogheny River (PA, USA) sediments could be detected using this approach.

The effect of sulfide type on the fracture behavior of HY180 steel

In this paper are discussed the effects of sulfide type on the fracture toughness of HY180 steel. Manganese was added to one heat and the sulfides in this heat were MnS. Lanthanum additions but no manganese additions were made to the second heat and the sulfur was gettered in this heat as particles of La 2O 2S. Neither lanthanum nor manganese additions was made to the other two heats. These two heats were modified by small titanium additions. The sulfur in these two heats was gettered as particles of Ti 2CS. After the usual heat treatment for HY180 steel the fracture toughness of the heat in which the sulfur was gettered as MnS was 256 MPa m . The fracture toughness of the heat in which the sulfur was gettered as La 2O 2S was 344 MPa m . The fracture toughness of this heat was greater than the fracture toughness of the heat in which the sulfur is gettered as MnS because the particles of La 2O 2S are larger and more widely spaced than the particles of MnS. The fracture toughness of the two titanium modified heats were 478 MPa m and over 550 MPa m . Void generation studies indicate that void generation is more difficult at particles of Ti 2CS than at particles of MnS or La 2O 2S. The improved fracture toughness of the heats in which the sulfur is gettered as Ti 2CS is attributed to the particles of Ti 2CS having greater resistance to void generation than particles of MnS or La 2O 2S.

In‐Situ Observation of the Formation of MnS during Solidification of High Sulphur Steels

A Confocal Scanning Laser Microscope equipped with a gold image furnace was used to directly observe the precipitation of MnS during solidification of high sulphur steels under isothermal conditions in the temperature region 1440 to 1480°C on the free surface of the steel melt. For the case of Al‐killed steels, below 1480°C MnS particles were found to precipitate with Fe forming simultaneously around them. This MnS containing structure continued to grow rapidly (264 μm/s) as a surface film. The film gradually changed, as the level of S in the melt decreased, into a eutectic structure (with lamella spacing of 2 μm) as predicted by thermodynamics. In Si‐ killed steels there was significantly lower tendency to form MnS both in terms of time until precipitation occurred and growth rate.

Nucleation of Proeutectoid Ferrite on Complex Precipitates in Austenite

Effect of various intragranular inclusions or precipitates (MnS, VC and V(C, N)) on the microstructure and kinetics of intragranular ferrite transformation at the temperatures between 973 and 823 K was studied using various Fe-2Mn-(0.13, 0.2)C(mass%) alloys with the small addition of sulfur, vanadium, and nitrogen. In Fe-2Mn-0.13C-50ppmS and Fe-2Mn-0.2C-470ppmS alloys, MnS particles, mostly incoherent in austenite, do not act as effective nucleation sites of ferrite. V addition slightly improves the potency of MnS as ferrite nucleation site by forming MnS+VC complex precipitates. The addition of both V and N largely enhances the intragranular nucleation of ferrite idiomorph on the MnS+V(C, N) complex precipitate. It is considered that two factors, i.e., (1) the advantage in the balance of interphase boundary energy and (2) the increase in the fraction of V(C, N) precipitate by the addition of nitrogen, are mainly responsible for the promotion of intragranular ferrite formation on the MnS+V(C, N) complex precipitate.

Effect of Equalisation Time on the Austenite Grain Size of Simulated Thin Slab Direct Charged (TSDC) Vanadium Microalloyed Steels

The thin slab direct charging process (TSDC) as applied to microalloyed steels has had a considerable development due to its relatively low production costs and ability to produce steels with good mechanical and toughness properties, comparable to those manufactured by the conventional cold charging process (CCC). This research is concerned with the effect of equalisation time on the microstructures. Three equalisation times (53 min, 318 min, and 1 333 min) at 1 150°C were investigated for a vanadium microalloyed steel, which contained a low carbon content (0.073 wt%) and a high nitrogen content (0.021 wt%). The experimental results show that MnS precipitates provided the main pinning forces during casting due to the high solubility temperature, but MnS particles did not provide a sufficient pinning force to prevent the austenite grains from growing. The austenite grain growth appears more likely to be abnormal in this stage. AlN precipitates were only identified at the longest equalisation time due to a low precipitation rate. The AlN pinning effect was evident at 1 333 min equalisation time, and was able to prevent further austenite grain growth by providing an additional pinning force. The study shows that vanadium does not have any effect on austenite grain growth at 1 150°C because of its low solubility temperature in austenite. When the steel was water-quenched, vanadium remained supersaturated in the solution but tempering in the ferrite phase field (650°C) can promote VN or VCN precipitation often using AlN as the nuclei.

Multiphase Crystallography in the Nucleation of Intragranular Ferrite on MnS+V(C,N) Complex Precipitate in Austenite

Crystallographic orientation relationships between intragranular ferrites, the MnS+V(C, N) complex precipitates acting as ferrite nucleation sites, and austenite matrix were studied in Fe-Mn-C alloys by scanning electron and transmission electron microscopy. VC holds a cube-cube orientation relationship (‹001›γ// ‹001›VC) when it is formed directly within austenite grains in an Fe-12Mn-0.8C-0.3V alloy. When VC precipitates nucleate on incoherent MnS particles dispersed in austenite, there is no specific orientation relationship between the three phases. Intragranular ferrite idiomorphs nucleating on the MnS+V(C, N) complex precipitate in austenite in Fe-1.5Mn-0.2C and Fe-2Mn-0.2C alloys often hold the Baker-Nutting orientation relationship ((001)α//(001)V(C, N), [110]α//[100]V(C, N)). Although several irrational ferrite/V(C, N) orientation relationships were observed, misorientation for either low-index planes or directions are relatively small between ferrite and V(C, N) for those relationships. The orientation relationships between intragranular ferrite and austenite were estimated by examining the misorientations between the ferrite and the neighboring martensite lathes from the Kurdjumov-Sachs inter-variant relationships. There is no specific orientation relationship between the intragranular ferrite idiomorph and the austenite matrix because of the low-energy orientation relationships between ferrite and V(C, N).

Three-dimensional distribution, morphology, and nucleation site of intragranular ferrite formed in association with inclusions

The three-dimensional (3-D) distribution, morphology and nucleation site of intragranular ferrite formed in association with MnS particles were observed by computer-aided reconstruction of images obtained by serial sectioning in an Fe–0.1mass% C–1.5mass% Mn alloy isothermally reacted at 610 and 640°C. 3-D analysis indicated that essentially all the intragranular ferrite precipitates nucleate at inclusions. The 3-D shape of idiomorphic ferrite precipitates was considerably more irregular than would be expected from their shape on polished specimen surfaces. Electron backscattering diffraction analysis showed that ferrite particles nucleated at inclusions were often composed of several grains and subgrains, and most of them were in contact with the surfaces of inclusions. Widmanstätten ferrite which grew radially from inclusions had a lath rather than a plate shape at the temperature studied.

Effects of gettering sulfur as CrS or MnS on void generation behavior in ultra-high strength steel

Void generation has been compared for two heats of AF1410 steel in which the sulfur has been gettered either as particles of MnS or as CrS particles. Voids are nucleated at lower plastic strains when sulfur is gettered as CrS than when sulfur is gettered as MnS. Diffraction results indicate that the CrS has a monoclinic structure.

Why stainless steel corrodes.

Stainless steels are used in countless diverse applications for their corrosion resistance. Although they have extremely good general resistance, they are nevertheless susceptible to pitting corrosion. This localized dissolution of an oxide-covered metal in specific aggressive environments is one of the most common and catastrophic causes of failure of metallic structures. The pitting process has been described as random, sporadic and stochastic and the prediction of the time and location of events remains extremely difficult. Many contested models of pitting corrosion exist, but one undisputed aspect is that manganese sulphide inclusions play a critical role. Indeed, the vast majority of pitting events are found to occur at, or adjacent to, such second-phase particles. Chemical changes in and around sulphide inclusions have been postulated as a mechanism for pit initiation but such variations have never been measured. Here we use nanometre-scale secondary ion mass spectroscopy to demonstrate a significant reduction in the Cr:Fe ratio of the steel matrix around MnS particles. These chromium-depleted zones are susceptible to high-rate dissolution that 'triggers' pitting. The implications of these results are that materials processing conditions control the likelihood of corrosion failures, and these data provide a basis for optimizing such conditions.

Nucleation of Intragranular Accicular Ferrite in a Ti-Containing Low Carbon Steel of High N Content

Formation of acicular ferrite grains by dispersing non-metallic inclusions which can act as intragranular nucleation sites within austenite grain is proposed as a method to obtain refined grain structure in steels. The microstructure of acicular ferrite steel consists of fine interlocking ferrite plates nucleated on dispersed non-metallic inclusions. This acicular ferrite structure provides a desirable combination of high strength and good toughness because of its small plate thickness and interlocking microstruture. in Ti-containing low carbon steels, researchers proposed that Ti2O3 or MnS, among inclusions, is the most effective nucleant for intragranular ferrite because of the formation of Mn depleted zone(MDZ) around Ti2O3 or MnS particles. TiN is also reported as a nucleation site owing to the coherency between ferrite and TiN crystals. But It has not been a simple task to identify which inclusions and what mechanisms are really effective in the formation of intragranular acicular ferrite.

Effect of Ni Interlayer on Corrosion Behaviour of Crn Pvd Coating Deposited onto Plastic Mould Steels

The plastics industry commonly uses moulds made of steels containing MnS inclusions. These inclusions play the role of heterogeneities, which make manufacturing easier. Moreover, these types of alloy are thermal treatment free, cheap, and easily available. Unfortunately, their use in corrosive conditions is prevented owing to the poor corrosion behaviour of the MnS particles. In order to mask these highly sensitive inclusions and to enhance the surface mechanical properties, hard physical vapour deposition (PVD) CrN coatings, elaborated at two different temperatures, have been used. The coated specimens have been tested in saline corrosive solutions using electrochemical techniques. Corrosion results from dissolution of the anodic substrate through coating porosity, inherent to the PVD process, which leads to the deposit peeling off. The aim of the present study is to determine the corrosion resistance of an underlayer electroless nickel deposited coating on a 40CrMnMo8S substrate coated with PVD CrN.

Ferrite nucleation potency of non-metallic inclusions in medium carbon steels

In recent years, there has been renewed interest in the role of non-metallic inclusions in controlling the microstructure of steels. The potency of various inclusions and precipitates such as SiO 2, MnO·SiO 2, MnS, Al 2O 3, Ti 2O 3 and VN for the nucleation of intragranular ferrite has been examined in the present study. Among them, single SiO 2, MnO·SiO 2, Al 2O 3, TiN and MnS particles seem to be inert to the nucleation of intragranular ferrite under the present experimental condition. Ti 2O 3 particles in a Mn-containing steel are very effective for the nucleation of intragranular ferrite, being (Ti,Mn) 2O 3 particles by absorbing Mn atoms from a steel matrix. On the other hand, Ti 2O 3 particles in a Mn-free steel are not effective. MnS and Al 2O 3 particles in high nitrogen steels containing vanadium also appear to be potent for the nucleation of intragranular ferrite. The decrease in transformation temperature causes a change in the morphology of intragranular ferrite from idiomorphic ferrite to acicular ferrite.

Monte-Carlo simulation of Goss texture development in silicon steel in the presence of MnS particles

A three-dimensional Monte-Carlo computer model of grain growth based on a full description of texture and microstructure is used to study the abnormal grain growth of Goss grains in the presence of coarsening MnS particles. This model incorporates the anisotropic grain boundary energy and anisotropic inherent mobility. The calculations show that high-energy boundaries are released at the early stages of the simulation. The results also demonstrate that at the early stages of the grain growth, the intensities of Goss and the main texture components increase. In the next stage of annealing, the intensity of the Goss texture increases at the expense of the main texture component. The growth of the largest grain reaches a steady-state growth rate.

In-situ Observation of Intragranular Ferrite Nucleation at Oxide Particles.

"In-situ" real time observation of the ferrite nucleation at nonmetallic inclusions has been successfully made at elevated temperatures with a confocal scanning laser microscope. The nucleation site, nucleation temperature, and/morphological change of the precipitates and ferrite can be sequentially determined as the phenomena occurring on the surface of steel. A polygonal ferrite starts to precipitate at an oxide particle at 1010 K and a Widmanstatten ferrite starts to precipitate at a MnS particle at 967 K. The degree of super cooling for austenite-ferrite transformation is found to be in good agreement with the prediction by a thermodynamic calculation.

Comparison between precipitation kinetics of manganese sulfide during hot compression process with one and two holding time in grain-oriented electrical steel

The aim of this work is the study of manganese sulfide particles precipitation (Fe-3%Si) after one and two holding time during hot compression process. Samples were heated at 1573K for 1800s. After the specimens were cooled down to 1373 and 1173K, hold for 32, 60 and 338s and the compression of 50% is applied during the holding time and then water quenched, in the process with two holding time, the first holding time is-60s (50% is applied), then the compression of 30% is applied (second holding time: 32, 60 and 338s), then water quenched. Grain size characterization was carried out using OM. The study of comparison precipitation has been carried out on the surface and the center of each sample. For TEM characterization of MnS particles an extraction replica technique has been used. Image analyzer measured the particle diameter. Optical micrographs showed that the grain size decreases with the second holding time process for the two temperatures on the two studied regions. Hot compression process with two holding time provides more dislocation and defects increasing the possibility of MnS particles precipitate and providing higher MnS particle density.

Nucleation of acicular ferrite enhanced by the precipitation of CuS on MnS particles

Nucleation of acicular ferrite enhanced by the precipitation of CuS on MnS particles

フラクトグラフィ ロータ鋼の各種破壊挙動に及ぼす組織異方性の影響

In order to clarify the anisotropy of fractography at fracture initiation site, monotonic tension, bending fatigue and tensile creep fracture tests were carried out at room and elevated temperatures, using three oriented specimens extracted from a Cr-Mo-V steel turbine rotor. In the case of monotonic tension, although the effects of temperature on tensile properties and fractography was prominent, the effects of specimen orientation on those were quite small at room and 839K temperatures. The fatigue limit of L-R oriented specimen was about 380MPa, and 25% higher than those of C-R and C-L oriented specimens. The scattering of fatigue life of C-R oriented specimen at the near fatigue limit stress condition was clearly larger than those of the other oriented specimens. Under bending fatigue, markedly different fractographic patterns were observed at the crack initiation site for all the three oriented specimens. It was found that the orientation of two kinds of inclusions, MnS and Al2O3 particles at the fatigue crack initiation site, influences the fractographic mode strongly. The creep result of L oriented specimen showed the longest life, as compared with those of the other oriented specimens, under nearly the same stress condition. The effect of specimen orientation on the fractographic patterns of creep was quite small.

Effect of Titanium Addition on the Formation and Distribution of MnS Inclusions in Steel during Solidification.

Effect of titanium addition on the size and dispersion of MnS inclusions in Fe-0.1 C-1 Mn-0.025(mass%) base alloys has been investigated by microscopy. Titanium addition brings about a marked decrease in the size of MnS inclusions which are otherwise large and globular in Ti-free specimens. The formation mechanism of MnS inclusions is discussed on the basis of phase diagram information and thermodynamics of particle engulfment during solidification. It is shown that the reduction in size of the MnS particles consequent on Ti addition is directly the result of successive nucleation events involving (Ti,Mn)O and MnS at the solid/liquid interface of iron.

Heat Treatment Response of Sintered M3/2 High Speed Steel Composites Containing Additions of Manganese Sulphide, Niobium Carbide, and Titanium Carbide

Abstract Metal matrix composites based on a sintered M3/2 high speed steel (HSS) and containing either single additions of TiC, NbC, or MnS particles or combined additions of MnS + TiC or MnS + NbC were sintered to full density and subjected to a conventional hardening heat treatment cycle of austenitisation, quenching, and double tempering. Relatively poor hardnesses and strengths were obtained in any composites that contained MnS particles, principally because of the weakening effects of MnS particles in the structure but also as a result of decarburisation of the steel matrix when oxygen introduced by the MnS particles reacted with carbon. Composites that contained TiC were changed in structure so that matrix M6C carbides were replaced by the less soluble MC carbide. They consequently showed slightly reduced hardening response compared to the baseline M3/2 HSS after heat treatment. Ball milling was necessary in powder mixtures that contained NbC to break up particle agglomerates. The resultant fine gra...

Creep damage of weldments in 1Cr-0.5Mo steels during long term service at elevated temperature

1. 1) The cracking of 1Cr-0.5Mo steel stub welds from the E.C.N.S.W. 3rd stage superheater outlet header occurs almost exclusively within the HAZ. The cracking is intergranular and follows prior austenite grain bo undaries. There is extensive cavitation along prior austenite grain boundaries adjacent to and ahead of these cracks. 2. 2) There is an enhanced concentration of MnS inclusions confined almost exclusively to the HAZ of those stub welds from the E.C.N.S.W. header exhibiting cracking. This is attributed to an effective “overheating” of the HAZ during weld formation, leading to dissolution and then re-precipitation of MnS particles at pr ior austenite grain boundaries during heating and cooling cycles, respectively. 3. 3) Techniques of scanning electron microscopy, and transmission electron microscopy of extraction replicas from both fracture surfaces and polished and etched sections, have been used to identify the presence of a large volume fraction of sub-micron MnS particles at prior austenite grain boundaries in the HAZ of cracked weldments. Coarse carbides have also been identified at these boundaries, the most common carbides being M 7C 3 and M 3C.