Characterisation of Dispersed Nano‐Sulphides Precipitated in Low Carbon Steel Solidified under High Rate of Cooling

The aim of this study was to investigate size distribution, chemistry, thermal stability and deformability of nano‐sulphides finer than about 100 nm formed in low carbon steel solidified under high rate of cooling and to assess the effect of the nano‐sulphides on the properties of steel. Laboratory mini‐ingots of low carbon steel containing various amounts of Mn, Cu and S, solidified under conditions simulating the direct strip casting process, were used as experimental material. Nano‐sulphides of MnS, (Mn,Cu)S, CuS, Cu_2‐xS and CuS_2‐x were identified in substantial quantities (volume fraction up to 3 ·10^?4) using TEM techniques. It was shown that interaction between the nano‐sulphides and migrating grain boundaries of austenite occurred during annealing and in the course of thermomechanical processing resulting in grain refinement. Nano‐sulphides of MnS and (Mn,Cu)S type were also identified in significant quantities (volume fraction up to 6 ·10^?4) in the shell and corner areas of commercial continuously cast billet.     

The Influence of Non‐Metallic Inclusions Physical State on Effectiveness of the Steel Filtration Process

The work presents theoretical fundamentals of the process of refining molten steel from liquid non‐metallic inclusions, using the method of filtration with ceramic filters ‐ the thermodynamic precondition for the absorption of liquid non‐metallic inclusions on the surface of a ceramic filter. The theoretical consideration has been supported by the results of laboratory tests on the filtration of steel which was previously reduced with complex deoxidants giving liquid products of deoxidization. The filtration process of steel melts reduced with complex deoxidants of type Al‐Mn‐Si has proved to be more efficient. The deoxidation products were identified on the filtration surface of the ceramic filters.     

Effect of the Slag Composition and a Protective Atmosphere on Chemical Reactions and Non‐Metallic Inclusions during Electro‐Slag Remelting of a Hot‐Work Tool Steel

The remelting behavior of the hot‐work tool steel X37CrMoV5‐1 is investigated with several experimental melts on a lab‐scale ESR‐plant. The investigated parameters comprise a variation of the slag compositions and the use of a protective nitrogen atmosphere. Variations of the slag composition include slags with different contents of CaF₂, CaO, and Al₂O₃ as well as a variation of the SiO₂‐content in the slag. The remelted ingots are forged and analyzed regarding their chemical composition. The distribution and composition of the non‐metallic inclusions (NMI) is studied by an automated SEM‐EDX method. Additionally, the chemical composition of the slag after remelting is analyzed. The results show clearly an equilibrium reaction between Si and Al in the steel with SiO₂ and Al₂O₃ in the slag as well as the effect of oxygen in open ESR operation. A protective atmosphere reduces the Si‐losses during remelting, but has no major effect on the number or composition of NMI compared to open remelting. The content of NMI, especially the larger ones, is reduced significantly in all remelting experiments. The majority of the NMI are MA‐spinel type except for the CaO‐free slag, where alumina inclusions prevail. In general, remelting leads to an almost complete removal of sulfides, a reduction of oxisulfides, and a slight increase of oxides.     

Analysis of the Nails from the Roman Legionary at Inchtuthil

This study is focused on the nails found at Inchtuthil, Perthshire (UK) dating to 87 A.D., The investigated nails were subjected to a preliminary radiographic analysis in order to point out the distribution of significant non‐metallic inclusions within the metal bulk. After the sectioning of the sample, an accurate optical microscopy examination was performed in order to study the different structural constituents of the microstructure. SEM‐EDS analysis allowed to quantitatively characterise the chemical composition of non‐metallic inclusions, while SEM‐EBSD examination revealed the crystallographic textures of the examined alloy. This information, coupled with the measurements of the micro‐hardness suggests a new hypothesis on the plastic deformation process adopted for the realization of the observed nails.     

Study of the Formation of Non‐metallic Inclusions by Ladle Glaze and the Effect of Slag on Inclusion Composition using Tracer Experiments

In the present work, BaO was used as tracer in the ladle slag to investigate the effect of slag on inclusion composition and the formation of non‐metallic inclusions by ladle glaze. Experiments were carried out at Uddeholm Tooling AB, Hagfors, Sweden. In the first heat of each series, about 20 mass% BaO was added to the ladle slag. In the next heat(s) using the same ladle, no BaO was added. BaO was detected in the inclusions. This observation showed strong evidence for the generation of non‐metallic inclusions by the ladle glaze. Even in the second and third heats, the fractions of BaO containing inclusions were still very high in all stages of the ladle treatment, indicating that ladle glaze was one of the major sources of inclusions. The sizes of the BaO containing inclusions were relatively big. The average size was 20 μm, while the biggest was around 100 μm. The increase of the fractions of BaO containing inclusions and their average content of BaO with the treatment stage suggested that the effect of slag on the composition of inclusions was a very slow process, due to the low solubility of Ba in the steel.     

Controlling Nozzle Clogging by Secondary Steelmaking Without Reheating

Ever since continuous casting was introduced, nozzle clogging has been a recurring subject of metallurgical research and publications. Nozzle clogging is caused by the deposition of non‐metallic inclusions – on the casting equipment – which are solid at the temperature of casting. Calcium treatment already represents a possible solution to eliminate this phenomenon, but there are special steel grades which do not allow its application either because they are price sensitive or for certain other reasons.³ Cleaning the steel melt by agitation is an alternative solution, but it has time constraints due to the cooling of the melt. Over extensive cooling can be prevented by heating the melt (in ladle), but its introduction and operational costs per heat are often too high for an individual steelmaking plant to afford. The goal of our research is to find metallurgical solution to reduce the rate of nozzle clogging in plants which do not possess a ladle furnace and the time devoted to treatment or the price of the product do not allow Ca‐treatment to be applied.     

Examination of the Influence of Heat Treatment on the Properties of AI‐Si Alloys

In this paper the influence of heat treatment on the structural and mechanical properties of Al‐Si alloys was investigated. Silicon content in the examined alloys was in the range 11 to 14%, the contents of the other alloying elements were in the standard range [1] but all alloys were modified with strontium. The regime of the applied heat treatment was quenching (520°C/6h – cooling in water) + aging (205°C/7h –air cooling). The examinations were carried out at room temperature as well as at 250°C and 300°C. The obtained results showed a positive influence of the applied heat treatment on the mechanical properties of the examined alloys. The improvement of the mechanical properties can be considered as a consequence of a redistribution and change of morphology of the phases present in the structure of the alloys.     

超细金属颗粒的特性和应用

按当今新观点,将超细颗粒分成三个等级来处理,以澄清世上一些对其命名和概念所引起的混乱状况。通过对其表面效应、体积效应(包括量子尺寸效应)及对原子簇幻数结构的详细描述,可释明超细金属颗粒之所以具有不同于一般块、粒状金属的诸多特异性能。还着重介绍了超细金属颗粒在宇航、原子能、军事、电子、化学、冶金等工业及医学、生物工程方面的最新应用成果。     

Serration Behavior in Zr-Cu-Al Glass-forming Systems

The metallic glass matrix composites(MGMCs)and bulk metallic glasses(BMGs)were studied by statistical analysis during plastic deformation at the strain rates of 2×10~(-2),2×10~(-3),and 2×10~(-4) s~(-1),respectively.No serration events occur in both MGMCs and BMGs during compression tests at the strain rate of 2×10~(-2) s~(-1).When deformed at the strain rate of 2×10~(-3) s~(-1),the BMG displays a larger plasticity,which is due to the larger serration events followed by a series of small serrations caused by the continuous movement of free volume.The amplitudes and elastic-energy densities increase with increasing the strain rates owing to many serrations in MGMCs.It is deduced that the Young′s modulus decreases from the normalized stress drop and fluctuations are observed on stressstrain curves,which is attributed to a lower coefficient according to the stick-slip model.