Papers by Keyword: Ferrite

Abstract: In this paper, the author performed orthogonal tests of ultrasonic vibration grinding on ferrite in the DMG machining center, and established a prediction model of ferrite surface roughness in ultrasonic vibration grinding with multiple linear regression analysis method based on the test results, and carried out significance tests on regression equation and regression coefficient, showing that the prediction model had high credibility, the effect of spindle speed and amplitude of ultrasonic vibration on surface roughness was significant, but of grinding depth and feed rate was not obvious.

Abstract: This lecture presents the authors personal views on the landmark events that have strongly affected the welding of stainless steels over their lifetime. Although 1913 is commonly recognized as the birth of stainless steels with the commercialization of the martensitic alloy of Harry Brearly and the austenitic alloy of Eduard Maurer and Benno Straus, the story can be considered to begin as long ago as 1797 with the discovery of chromium by Klaproth and Vauquelin, and the observation by Vauquelin in 1798 that chromium resists acids surprisingly well. From the 1870s onwards, corrosion resisting properties of iron-chromium alloys were known. One might mark the first iron-chromium-nickel constitution diagram of Maurer and Strauss in 1920 as a major landmark in the science of welding of stainless steels. Their diagram evolved until the outbreak of World War II in Europe in 1939, and nominally austenitic stainless steel weld metals, containing ferrite that provided crack resistance, were extensively employed for armor welding during the war, based on their diagram. Improved diagrams for use in weld filler metal design and dissimilar welding were developed by Schaeffler (1947-1949), DeLong (1956-1973) and the Welding Research Council (1988 and 1992). Until about 1970, there was a major cost difference between low carbon austenitic stainless steels and those austenitic stainless steels of 0.04% carbon and more because the low carbon grades had to be produced using expensive low carbon ferro-chromium. Welding caused heat affected zone sensitization of the higher carbon alloys, which meant that they had to be solution annealed and quenched to obtain good corrosion resistance. In 1955, Krivsky invented the argon-oxygen decarburization process for refining stainless steels, which allowed low carbon alloys to be produced using high carbon ferro-chromium. AOD became widely used by 1970 in the industrialized countries and the cost penalty for low carbon stainless steel grades virtually vanished, as did the need to anneal and quench stainless steel weldments. Widespread use of AOD refining of stainless steels brought with it an unexpected welding problem. Automatic welding procedures for orbital gas tungsten arc welding of stainless steel tubing for power plant construction had been in place for many years and provided 100% penetration welds consistently. However, during the 1970s, inconsistent penetration began to appear in such welds, and numerous researchers sought the cause. The 1982 publication of Heiple and Roper pinpointed the cause as a reversal of the surface tension gradient as a function of temperature on the weld pool surface when weld pool sulfur became very low. The AOD refining process was largely responsible for the very low sulfur base metals that resulted in incomplete penetration. The first duplex ferritic-austenitic stainless steel was developed in 1933 by Avesta in Sweden. Duplex stainless steels were long considered unweldable unless solution annealed, due to excessive ferrite in the weld heat-affected zone. However, in 1971, Joslyn Steel began introducing nitrogen into the AOD refining of stainless steels, and the duplex stainless steel producers noticed. Ogawa and Koseki in 1989 demonstrated the dramatic effect of nitrogen additions on enhanced weldability of duplex stainless steels, and these are widely welded today without the need to anneal. Although earlier commercial embodiments of small diameter gas-shielded flux cored stainless steel welding electrodes were produced, the 1982 patent of Godai and colleagues became the basis for widespread market acceptance of these electrodes from many producers. The key to the patent was addition of a small amount of bismuth oxide which resulted in very attractive slag detachment. Electrodes based on this patent quickly came to dominate the flux cored stainless steel market. Then a primary steam line, welded with these electrodes, ruptured unexpectedly in a Japanese power plant. Investigations published in 1997 by Nishimoto et al and Toyoda et al, among others, pinpointed the cause as about 200 ppm of bismuth retained in the weld metal which led to reheat cracking along grain boundaries where the Bi segregated. Bismuth-free electrode designs were quickly developed for high temperature service, while the bismuth-containing designs remain popular today for service not involving high temperatures.

Abstract: During forging of as-cast for fractured connecting rod, the key is to determine heating temperature and to control cooling speed after forging. They two points are correlated with each other. To assure metal fluidity in the course of striking and forging, fillet should be enlarged at transit between ribs and web. Wrought parts shall be subject to normalizing by residual heat from forging process. Its metallographic structure consists of pearlite and ferrite. Content of ferrite should not exceed 35%. In addition, it should be such that the fraction for volume of ferrite get bigger and grain should be greater and evenly distributed.

Abstract: Ferrite material is a kind of special ferromagnetic mental oxide with Fe3+ as a main component. Based on the assumption that the reduction of Fe3+ and the magnetic variations could produce potential active impacts on degradation of organic pollutants under anaerobic conditions, we took water and sediment samples from Chongming east intertidal flat, a typical coastal wetland, to investigate the effects of exogenetic addition of ferrite on the removal of toluene in sediments during an 11-day incubation. Ferrite (Fe₁₂O₁₉·Sr, M.W. 1061.75, Nanosized spherical material 800 nm, the purity >98%) was added into sediment samples by proportions of 0.0, 5.0, 10.0, 20.0 g/kg with 0.0, 0.2, 0.5, 1.0 ml/kg toluene, respectively. It is found that the rate of toluene removal is the highest when the ferrite added is 10.0 g/kg with toluene recovery rates of 0.24%, 20.79%, 30.36% for treatments of 0.2, 0.5, 1.0 ml/kg toluene addition by the end of 11th day of incubation, respectively. In contrast, the recovery rates are 1.85%, 50.05%, 55.68%, respectively, when ferrite content rises to 20.0 g/kg. In addition, all toluene recovery rates are less than 2% after 11 day incubations under the condition of 0.2 ml/kg toluene, indicating that the removal rate of toluene depends on the contents of toluene in sediments. In summary, it confirm that application of exogenetic ferrite material can effectively enhance the removal of toluene from the sediment.

Abstract: Electromagnetic microwave absorbing composite material containing magnetic Mn-Zn ferrite/conductive polyaniline nanocomposites introducing into epoxy resin were fabricated. The conductivity of the Mn-Zn ferrite/polyaniline nanocomposites were investigated by a four point probe method. Complex permeability and reflection loss of the Mn-Zn ferrite/conductive polyaniline/epoxy resin composites have been studied in the frequency of 30 MHz to 1 GHz. It has been found that the conductivity of the nanocomposites can be tailored by controlling the weight percentage of polyaniline. The complex permeability increased with the decreasing weight percent of polyaniline. The composite with the polyaniline weight percent of above 60.89 % can effectively broaden the absorbing band with minimum absorption of 5 dB about 500 MHz. It has also been found that the composite with the polyaniline weight percent of 28.12 % has a maximum absorption of 23 dB at about 700 MHz for a coating thickness of 2 mm. Therefore, the prepared composites can be potentially applied in electromagnetic absorbing field in the low frequency.

Abstract: High temperature flow curves were evaluated on two Nb steels in both compression and torsion and at a series of temperatures and strain rates. The critical strains for the initiation of dynamic transformation (DT) were determined by the double differentiation method. These are shown to be distinctly lower than those associated with dynamic recrystallization (DRX). It is also evident that the compression critical strains for both DT and DRX are lower than the equivalent torsion critical strains. Mean flow stresses (MFSs) were calculated by integration from the flow curves. When plotted against inverse temperature, stress drops were observed about 30 degrees above the Ae₃. These drops are shown to be caused by the dynamic transformation of austenite to ferrite, a softer phase. The characteristics of the ferrite produced dynamically are described and the transformation is shown to be displacive in nature, leading to the appearance fine Widmanstatten plates.

Abstract: W-type hexagonal ferrite BaZn_0.6Co_1.4Fe₁₆O₂₇ was prepared by the method of coprecipitation with flux. Various products were prepared by different thermal treatments. The microstructure, element composition, crystal structure, phases and dynamic electromagnetic parameters of the products were analyzed by SEM, EDS, XRD and the microwave vector network analyzer. The formation of the ferrite was studied and the optimal thermal treatment condition was confirmed, under which pure tiny W-type hexagonal ferrite powders were achieved.

Abstract: DC/DC converter modules have been used in military and civil industrials on a large scale. This paper mainly elaborates the application scope and characteristics of soft materials, which are used in DC/DC converter modules, and the effect of core type and integrating method on converter modules were researched. The development trend is pointed out combining with the technology of DC/DC converter modules.

Abstract: The factors affecting pipeline fractures are reviewed briefly, with particular emphasis on the influence of the {100} texture component. The deformation texture components introduced by rolling in the austenite temperature range are introduced, together with the component changes associated with recrystallization. The effect of the γ-to-α phase transformation on the austenite deformation and recrystallization texture components is described. The changes to the texture brought about by rolling in the ferrite (or in the intercritical) phase field are also outlined. The controlled rolling parameters that promote minimization of the texture intensity of the deleterious {100} component are summarized.

Abstract: Mechanical properties, especially fatigue strength, of ferritic spheroidal graphite cast iron might depend not only on the graphite size but also on the ferrite grain size, little systematic research has been made on these factors. To clarify the influences of these structural factors as well as loading condition, fatigue tests have been carried out on ferritic spheroidal graphite cast iron with different sizes of graphite nodules and ferrite grains, under the axial loading with mean stress from -70MPa to 240MPa. The results obtained in this study are summarized as follows: (1) The fatigue limits are decreased with increasing graphite nodule and matrix grain sizes. (2) The fatigue limit decreases with increasing tensile mean stress. The fatigue limit at an arbitrary mean stress has been estimated by the modified Goodman diagram as well. (3) The parameter α is evaluated from the experimental results relating to the stress ratio R, for the mean stress acting on the tensile side and on the compressive side separately. For the case of R0, the value of α is 0.324. The result has been applied to the fatigue limit evaluation equation of Y.Murakami et al, the fatigue limit ratio falls within the range of about ±10%.