CO2 Mixed Gas Research Articles

Reduction of blowholes in high-speed arc welding of hot-dip galvanised steel sheets

Summary This paper describes an investigation of the blowhole formation mechanism and the substances causing blowholes during high-speed arc welding of galvannealed steel sheets extensively used in the chassis components of motor vehicles. Based on these results, it clarifies the effect of the shielding gas composition on suppression of zinc vaporisation and also examines suitable preventive measures. The results obtained may be summarised as follows: 1. Provided the organic substances adhering to the base material amount to around 1 mg/cm2, they are not the main cause of blowhole formation. 2. Even after thorough degreasing in such a way that the amount of organic substances present is equivalent to less than 1 in 500 parts of the zinc coating weight, numerous blowholes are formed to much the same extent as those found in the base material before degreasing. 3. The gas collected through the blowhole zone being broken apart reveals its main components to be hydrogen and hydrocarbons, including methane. Hydrogen is present at the level of around 1 in 10 parts of methane. 4. Sinewy traces of zinc are found in the blowhole origins of the root zone extending from the heat affected zone of sheet fit-up. A zinc concentration gradient is found on the blowhole face walls extending from these origins towards the bead surface. 5. On the basis of (1)-(4), there is little possibility of hydrogen being the cause of blowholes, which appear to be due to the vaporisation of zinc. 6. An oxygen-containing shielding gas promotes zinc oxidation and suppresses zinc vaporisation and is therefore effective for blowhole reduction. The optimum addition rate is around 5% for a shielding gas consisting of 80%Ar + 20%CO2 mixed gases. Oxygen addition is especially effective at a joint gap width of 0.2–0.4 mm. 7. Suitable selection of filler materials with a melting point below 1400°C intended to ensure that the weldpool temperature is kept low and the application of an oxygen-containing shielding gas are effective for blowhole reduction.

Decomposition of CO2, CH4 and CO2-CH4 mixed gas hydrates.

To evaluate the possibility of CH4 exploitation in linkage with CO2 isolation, the decomposition rates of CO2, CH4 and CO2-CH4 mixed gas hydrates were obtained under isothermal isobaric conditions. The decomposition rates of CO2 and CH4 pure gas hydrates are proportional to the total amount of gas hydrate and the fugacity difference from the equilibrium state under the conditions of three-phase coexistence. The rate constant of CO2 hydrate decomposition is larger by one order than that of CH4 hydrate. In the CO2-CH4 mixed hydrate decomposition, CH4 composition in the generated gas is substantially larger than the value calculated from the pure hydrate decomposition rate while CO2 remains selectively in the mixed gas hydrate.

Influence of hydrogen limitation on gaseous substrate utilization in autotrophic culture of Alcaligenes eutrophus ATCC 17697 T

The influence of an insufficient supply of H 2 on microbial gas consumption was investigated in autotrophic culture of Alcaligenes eutrophus ATCC 17697 T. Experiments were conducted in a recycled-gas, closed-circuit system consisting of a 200-ml vessel containing 100-ml culture of 8.0 g· l −1 (on a dry matter basis) viable cells. A mixed gas of CO 2, H 2 and O 2 was used, in which the partial pressures of CO 2 and O 2 were kept at 10.1 and 20.3 kPa respectively, but that of H 2 was varied from 70.9 to nearly zero kPa by mixing with N 2. The total pressure was maintained at 101.3 kPa. The gas mixture was fed into the vessel at a flow rate of 100 ml·min −1 and the gas consumption rates of CO 2, H 2 and O 2 as well as the partial pressures of dissolved H 2 and O 2 ( p LH and p LO) were determined. The dissolved H 2 concentration ( C H) was calculated from the p LH, and its relationship with each gas consumption rate was examined. These values were plotted on a hyperbola. Lineweaver-Burk plots of all the gas consumption rates against C H gave straight lines. Gas consumption rates during the growth of this microorganism could be changed by varying the p LH under H 2-limited conditions, and could be expressed in the same form as Monod's equation with C H as the sole variable.

ＦｅＯｒＭｇＯ‐ＳｉＯ２系スラグへのニッケルおよび銅の溶解

To obtain the fundamental information on the dissolution of nickel and copper into the slag formed in the nickel and nickel alloy smelting processes, the phase relations between Ni-Cu-Fe alloys and FeOX-MgO-SiO2slags saturated with MgO were investigated under controlled oxygen partial pressure using CO and CO2mixed gas at 1, 673 and 1, 773KThe MgO solubility in the FeOx-SiO2slag increased from 16 to 30 mass% corresponding to 10 and 40 mass%SiO2 respectively at 1, 773 K.Ni and Cu are concentrated in the metal phase while Fe is distributed mainly in the slag phase under the present experimental condition. The distribution ratios of Ni and Cu into the slag increase with increasing oxygen pressure. At 1, 673 K, Ni dissolution in the slag is lower than Cu atPO2less than 2×10-4Pa.In the higher oxygen potential region, the Cu dissolution in the slag is much higher than Ni. Similar behavior is observed between the distribution ratios of Ni and Cu at 1, 773KApplying the logarithmic relationship between the distribution ratio and oxygen pressure, nickel and copper form NiO and CuO0.5in the slag equilibrated with the ternary alloys.

The effect of attractant in the Tabanid-fly, Tabanus iyoensis with mixed gas of CO2 and cyphenothrin

The effect of attractant in the Tabanid-fly, <i>Tabanus iyoensis</i> with mixed gas of CO₂ and cyphenothrin

Diamond Synthesis by the Microwave Plasma Chemical Vapor Deposition Method Using the Pretreated Carbon Dioxide and Hydrogen Mixed-Gas System

High-quality diamond was obtained by the microwave plasma-assisted chemical vapor deposition (plasma CVD) method using the pretreated carbon dioxide (CO2) and hydrogen (H2) mixed-gas system. The pretreatment method is as follows: at first, CO2 and H2 pass through the prereactor, where plasma is generated by microwave discharge, and then the reactant passes through the cold trap at around 185 K in order to remove water (H2O) produced in the plasma from CO2 and H2. The residue of the pretreated CO2 and H2 mixed gas, which consists of CO, CO2 and H2, is introduced into the main reactor where diamond is synthesized. Diamond can grow to a feed ratio of CO2/H2=25/100 sccm. Plasma diagnosis was performed using optical emission spectroscopy (OES) and gas chromatography (GC).

Sintering of Compositions in the System Cr&lt;sub&gt;2&lt;/sub&gt;(C, N)-ZrO&lt;sub&gt;2&lt;/sub&gt;

Cr2(C, N) was obtained by heating Cr metal powder in a mixed gas of CO and N2. This compound is useful for high temperature structural and heat element materials since it is high melting and electronic conductive. This compound, however, is easily oxidized in an atmosphere containing oxygen at high temperatures. The oxidation resistance is enhanced by forming a densely sintered Cr2(C, N)-ZrO2 body. This paper described a fundamental for the development of composites in the system Cr2(C, N)-ZrO2. The dense Cr2(C, N)-ZrO2 body was obtained by heating mixtures of Cr and ZrO2 in a gas mixture of CO and N2 at 1500°C. For example, a dense Cr2(C, N)-ZrO2 body with relative density of 95% was obtained from a (60wt% Cr-40wt% ZrO2) compact by sintering in a gas with pco of 0.2atm and pN2 of 0.8atm at 1500°C.

ガス浸炭窒化処理鋼の耐食性について

Corrosion resistance test of carbon steel carbo-nitrided in the mixed gas of CO and NH3 at 550-850°C, were made in air, water, 10% NaCl, 1N NaOH, 0.1N H2SO4, HCl, and HNO3 solution without agitation, by observing the change of weight and surface condition.The result: -Carbo-nitrided steel, compared with plain carbon steel, had high resistivity in water, air, 10% NaCl, 1N NaOH solution, but low in mineral acids. That treated at 850°C showed poor result due to the precipitation of Fe3C in surface layer (e-phase) produced during carbo-nitriding.

鐵鑛石間接還元難易の理由に關する二三の研究

The reducing velocities by CO gas were tested for a kind of limonite ore, 5 kinds of hematite ores, 4 kinds of magnetite ores and a kind of heating furnace cinder. Each ore was equally granulated in about 1m.m. dia. and 1c.c. of the granulated sample was taken in each experiment. 100c.c. of the mixed gas of CO(35%) and N2(65%) per min. were passed for some hours through the sample which was kept at 800°C. or 1000°C. in an electric resistance furnace. The % of CO2 in the exhausted gas from the sample was analysed every 10mins. The amount of CO2 indicated the amount of the oxygen taken from the iron ore, and thus the reducing velocities of the various ores were calculated.The reducing velocities of the limonite and hematite ores which contained not much silica, were more rapid than those of the magnetite ores and the heating furnace cinder, the velocity of the last being the slowest.Also the reducing velocities from Fe3O4 to FeO and those from FeO to (Fe. FeO) were compared in each ore and averaged. Averaging the ores which contained over 50% of iron (51 to 70% Fe) it was seen that the reducing velocity (at 1000°C. or 800°C) from Fe3O4 to FeO was about 2.2 times (1.4 to 3.1 times) greater than that from FeO to (Fe. FeO) and the ratio was greater for the siliceous hematite ores compared with the hematite ores which contained not much silica.Again the degree of the increment of the reducing velocities of the various ores at 1000°C. against that at 800°C. was compared, and it was found that the degree of the increment for the magnetite ores was much greater than that of the hematite ores.The conditions of easily reducible ore were ascertained from our experiment.