Decrease Of Silicon Content Research Articles

高速度工具鋼の靭性に及ぼすＳｉの影響

This study has been carried out in order to investigate the effects of contents of silicon and other impurity elements on the toughness, heat treatment characteristics and tool life of SKH 51 type high speed tool steel.Results are summarized as follows:(1) Decrease of silicon content is most effective in comparison with the decrease of sulfur, phosphorus and nitrogen contents for the improvement of toughness at 20°C.(2) Solidification structure and microsegregation are improved with decreasing silicon.It is considered that the improvement of toughness is due to the fine solidification structure and low degree of microsegregation.(3) Tempered hardness is decreased with decreasing silicon content.(4) Tool life of low silicon steel is almost the same as 0.30% silicon base steel at the same hardness.

Precipitation of Hydrated Silica From Spent Hydrofluoric Acid: How Much of a Problem Is It? (includes associated papers 16441 and 16444 )

Summary Recent studies have shown that the reaction of clay withhydrofluoric (HF) acid is more complex than was earlier believed. It hasbeen found that fluosilicic acid, generated during initial dissolution ofclay, reacts with additional clay, extracting aluminum and depositing hydrated silica. It has been suggested that this silica precipitation may result in significant formation damage. The paper describes studies designed to investigate further the silicadeposition phenomenon as it relates to potential formation damage. Possible beneficial effects resulting from clay stabilization also areexplored. Long core tests show that in spite of extensive silica precipitation, there is little evidence of actual formation damage. Scanning electronmicroscope (SEM) examination of clays situated beyond the zone ofpermeability improvement shows major modification of clay surfaces as aresult of secondary reactions. Sand grains appear clean, however, withsilica deposition apparently confined to the clays. Energy-dispersive X-ray (EDX) analysis of modified clays indicates complete loss of alumin. Bulk analysis of core material, however, reveals that much undissolved aluminum remains through the entire length of the acidized core. Water-sensitivity testing of acidized cores shows almost completestabilization of clays both in the zone of permeability improvement and fora considerable distance beyond. Long-term flow testing reveals no increasein the migration tendency of fines as a result of the acid treatment. Introduction Precipitation of insoluble reaction products from spent HFacid has long been recognized as a major problem insandstone-matrix acidizing. The reaction of HF acidwith clays, feldspars, and other minerals can result in theformation of various insoluble precipitates. Failure toconsider this problem can lead to poor treatment results and, in some cases, severe formation damage. HF acid is usually used in sandstone-matrix acidizing because of its ability to dissolve a variety of siliceousminerals, including quartz, clay, and feldspar. Althoughquartz (SiO2) constitutes the bulk of most sandstoneformations, the greatest portion of the HF acid is consumed by reaction with clays and feldspars because of their muchfaster reaction rate. It has been estimated that thereaction rate of HF acid with clay is 100 to 200 times fasterthan with quartz. As a result, the reaction with quartzis so limited that it is usually ignored, and thegeneralized initial reaction of HF acid with clays in theformation is expelled as Actually, this is only the initial stage of a complexreaction sequence. Depending on free fluorideconcentration, silicon fluorides can exist as SiF4, SiF5 -, andSiF6 --, while the aluminum fluorides are present as Al+++, AlF++, AIF2+... AlF6. Because aluminumhas a greater affinity for fluorine than silicon, the siliconfluorides and more-fluoride-rich aluminum species reactwith undissolved clays, extracting aluminum andprecipitating hydrated silica. Thus the aluminumconcentration in the acid increases with a corresponding decreasein silicon content. As a result, most of the silicon initially dissolved by the HF acid precipitates within the matrixof the rock. That this can be a major cause of formationdamage has been suggested. In addition to Si(OH)4 Precipitation, other insolublereaction products can also form. Among these areNa2SiF6, K2SiF6, and CaF2. All these materials arerelatively insoluble. Damage resulting from theirprecipitation, however, can be minimized by use of an HClpreflush, ahead of the HF acid, to remove any CaCO3present and by avoidance of brines containing Ca, Na, or K during the treatment. However, there is no knownway to prevent precipitation of Si(OH)4, exceptpossibly by returning the spent acid before precipitation occurs. The main purpose of this study was to investigate thedegree of damage caused by Si(OH)4 precipitation and, if necessary, to propose methods of minimizing thisdamage. Formation Damage FromSilica Precipitation Precipitation of hydrated silica from spent HF acid hasbeen the subject of extensive investigation. Theconditions under which Si(OH)4 precipitation occurs havebeen established, and there is little doubt that most of the silicon dissolved by HF acid during acidizing ofargillaceous sandstone is precipitated as hydrated silica beforethe spent acid can be recovered from the formation. Themanner in which the precipitate forms and the magnitude of the resulting formation damage, however, have notbeen thoroughly investigated. JPT P. 1234^

高強度鋼溶接金属のじん性改善法

Many investigations on low carbon weld metals have revealed that weld metal composed of fine acicular ferrite has sufficient toughness and the addition of Ti or T1-B into weld metals effectively forms the acicular ferrite microstructures. However, the majority of these investigations were concerned in the approximate strength range of 50-70 kg/mm2 and not in the range over 70 kg/mm2.The toughness of baimtic and/or ferntic weld metal of high strength steel was investigated in this report.The specimens of weld metal were prepared by DC-GMA welding process and the effects of the oxygen content and silicon content on the toughness of weld metal were investigatedThe oxygen levels affected the microstructure change of high strength steel weld metal as had been found in 50-70 kg/mm2. And decreasing silicon content in weld metal was remarkably effective in producing the fine microstructure and imrpoving charpy impact properties of high strength steel weld metalThe test results could be explained in terms of decreasing martensite-austenite (M-A) constituent with decreasing silicon content.

Superconductivity of Zr-Nb-Si amorphous alloys

Superconducting amorphous alloys with high strength and good ductility have been found in rapidly quenched alloys of the Zr-Nb-Si system. These alloys were produced in a continuous ribbon form of 1 to 2 mm width and 0.02 to 0.03 mm thickness using a modified single roller quenching apparatus. The amorphous alloys were formed over the whole composition range between zirconium and niobium, but the silicon content was limited to the relatively narrow range between about 12 and 24 at%. All the amorphous alloys showed a superconducting transition whose temperature, Tc, increased from 2.31 to 4.20 K with increasing niobium content or with decreasing silicon content. The upper critical magnetic field, Hc2, and the critical current density, Jc, for Zr15Nb70Si15 alloy were of the order of 4.5 Tesla(T) and 5.5×106 A m−2 at 1.5 K in the absence of applied field. The upper critical field gradient at Tc, \((dH_{c2} /dT)_{T_c } \), and the electrical resistivity at 4.2 K, ρn, decreased from 2.89 to 2.10 T K−1 and from 2.70 to 1.80μΩm, respectively, with the amount of niobium. The Debye temperature, θD, the electron-phonon coupling constant, λ, and the bare density of electronic states at the Fermi level, N(Ef) were calculated from the experimentally measured values of ρn, \((dH_{c2} /dT)_{T_c } \), Young's modulus and density by using the strong-coupling theories. From the comparison of Tc with their calculated parameters, it was found that λ is the most dominant parameter for Tc. The GL parameter, κ, and the GL coherence length, ξGL(0), were estimated to be 70 to 100 and about 7.6 nm, respectively, from the experimental values of \((dH_{c2} /dT)_{T_c } \) and ρn by using the GLAG theory and hence it is concluded that the present amorphous alloys are an extremely “dirty” type-II superconductor having a very weak flux pinning force.

Non-equilibrium crystalline superconductors in Zr-Si binary alloys rapidly quenched from melts

The new non-equilibrium superconductor with a b c c structure has been found in rapidly quenched Zr-Si alloys. The silicon content in the b c c alloys was limited to the narrow range between 8 and 11 at%. The b c c alloys showed a superconducting transition whose temperature increased from 3.20 to 3.84 K with decreasing silicon content. The upper critical magnetic field and the critical current density for Zr92Si8 alloy were of the order of 3.58 × 106 Am−1 at 2.0 K and 3.3 × 10−2 Am−2 at 2.42 K in the absence of an applied field. The upper critical field gradient at the transition temperature and the electrical resistivity at 4.2 K were about — 1.82 × 10−1 Am−1 K−1 and about 150 μΩcm. The Ginzburg-Landau parameter κ and coherence length ξGL (0) were estimated to be about 65 and 6.3 nm, respectively, from these experimental values by using the Ginzburg-Landau-Abrikosov-Gorkov theory and hence it is concluded that the present b c c alloys are extremely “soft” type-II superconductors with a high degree of dirtiness.

Effect of Gibberellic Acid on Silica Content and Distribution in Sugarcane

The effect of gibberellic acid on the content and distribution of silicon in the stem, leaf sheath, and leaf lamina of sugarcane was analyzed in relation to the effect of gibberellic acid on stem growth. Silicon content was measured by neutron activation analysis, and its distribution was followed by scanning electron microscopy and X-ray analysis.Foliarly applied gibberellic acid increased stem length and fresh weight and decreased silicon content. Gibberellic acid treatments had little or no effect on growth or silicon content of leaf laminae or sheaths. The close correlation between increase in growth of an internode in response to gibberellic acid and the decrease in silicon content of that internode indicated a dilution effect of growth on the amount of silicon rather than a direct effect of gibberellic acid on silicon deposition. This conclusion was supported by scanning electrom microscopy, X-ray map photos, and counts of silica cells per unit of epidermis area.

Superconductivity of ductile Ti-Nb-Si amorphous alloys

Amorphous superconducting alloys with high strength and good ductility have been found in rapidly quenched alloys of the Ti-Nb-Si system. Continuous ribbons of these alloys were produced about 2 mm wide and 0.04 mm thick using a modified single roller quenching apparatus. The silicon content in the amorphous alloys was limited to the range between about 13 and 21 at. % and the niobium content was in the range 0–43 at. %. The alloys containing more than 10 at. % niobium showed a superconducting transition above the liquid-helium temperature (4.2 K). The transition temperature Tc increased with increasing niobium content or with decreasing silicon content. The highest value obtained was 5.1 K for Ti45Nb40Si15. The upper critical magnetic field Hc2 and the critical current density Jc were of the order of 1.6×106 A/m at 4.2 K and 300 A/cm2 at zero applied field and 4.2 K.

Phase transformation of low-carbon silicon steels LS 1.2 and LS 1.5

This paper contains information on the high-temperature phase equilibria and transformation behavior of two commercial low-carbon silicon steels (1.4–1.5% Si) determined by dilatometry and metallography. Use of a picric acid etching reagent has enabled the distribution of the α and γ phases to be determined on specimens cooled relatively quickly from high temperatures, and measurements of the quantity of γ present by normal etching in nital are shown to be underestimates. The steels studied contain some γ at temperatures from 760°C to at least 1200°C, with the amount increasing with decreasing silicon content and increasing temperature.

Variations of nitrogen with silicon content of electrical steels

The nitrogen content of commercial heats of electrical steels has been observed to increase with decreasing silicon content prior to teeming despite a constant nitrogen content prior to addition of alloying silicon to molten steel. This behavior can be qualitatively described by a nitrogen transfer model which predicts: the rate of absorption of nitrogen by the metal is greater at lower silicon contents; a final nitrogen level increasing with decreasing silicon; the thermodynamic activity of nitrogen is approximately constant regardless of silicon content at teem time; the nitrogen level increases with longer holding times; and ladle practice will affect nitrogen levels.