Effect of silicon on the eutectic carbides in as-heated M2 high speed steel

The effect of silicon on the eutectic carbides in as-heated M2 high speed steels is investigated by using optical microscope, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction analysis. The high speed steel ingots with different silicon additions are produced by electroslag remelting process (the mass content of silicon is 0.3%, 0.8%, 1.6% and 2.4%, respectively). The ingots are annealed at 780 ℃ for 10 h and heated at 1 165 ℃ for 2.5 h. The results show that the eutectic carbides distributed in the dendrites with continuous or semi-continuous net-shape in the as-annealed ingots. The eutectic carbides change from lamellar-like M2C to herringbone-like M6C with the increase of silicon content. After 2.5 h heating at 1 165 ℃, the lamellar-like M2C decomposes into granular M6C and MC, and the size of granules in M2 high speed steel ingot with 0.8%Si addition is smaller than that in the 0.3%Si. Whereas herringbone-like M6C is unchanged during heating treatment, and coarse primary blocky carbides which are harmful for properties still exists after the deformation.     

Influence of obstacles on the parameters of flame front in gas explosion

The temperature, ion current, overpressure and photoelectric signal of flame front at the same cross-section in square tube of laboratory simulation of tunnel are recorded by homemade thermocouple, homemade ion probe, pressure transducer and photoelectrical transducer at the same time. The parameters changes of flame front with the same gas concentration of 10.17% are compared with obstacles or without obstacles. The results show that, when the obstacles exists, the value of temperature is slightly lower, the temperature is from 1 303.7 ℃ down to 1 234.4 ℃ by close to ignition position and from 1 198.7 ℃ down to 902.5 ℃ away from ignition position. The value of ion current is slightly higher and the double peak values occur obviously in the signals of ion current, the peak value of ion current is from 1 46.25 nA up to 160 nA in the vicinity and from 432.5 nA up to 605 nA in the distance. The precursor compression wave in flame propagation tube is appeared ahead to further promote the gas explosion process in DDT. Therefore, roadway should minimize the presence of obstacles.     

不同生物降解地膜对大蒜生长发育的影响及降解效果研究

以金乡白皮蒜为试验材料,研究了“降解1号”、“降解2号”、“降解3号”3种氧化-生物双降解地膜、普通地膜及不覆膜对大蒜生长发育和产量的影响,并研究了不同降解地膜的保温保墒和降解性能。结果表明：氧化-生物双降解地膜和普通地膜处理之间,株高、植株重量、假茎粗、单叶平均叶面积以及鳞茎亩产鲜重差异均不显著,3种降解地膜比较,“降解3号”鳞茎产量较高,为28932.75 kg/hm2不覆膜处理由于低温冻害,鳞茎产量为覆膜处理平均产量的17.53%。对比不覆膜处理,不同覆膜处理均能显著提高5 cm和15 cm的土层温度以及10 cm土层的土壤含水量,尤其能够显著提高深层土壤温度,生物降解地膜与普通地膜处理之间差异不显著。降解性能对比,“降解1号”降解效果最好,至大蒜成熟期,最大拉力和断裂伸长率为0,“降解2号”和“降解3号”断裂伸长率分别为102.83%和360.28%。     

Influence of high temperature on the performance of some Phaseolus species at different developmental stages

Summary The effect of short term high temperature exposure on the performance of five Phaseolus species and of long term (continuous) exposure on the performance of P. vulgaris was studied at three growth stages. Phaseolus species subjected to 26.7, 32.2 or 37.3°C for two days showed small differences in the number of pods produced and in visual leaf damage, but large differences in leaf heat killing time, as measured by conductivity. P. coccineus had the shortest heat killing time (20–60 minutes) and P. acutifolius and P. lunatus the longest times (180 and 153 minutes), respectively. The P. vulgaris genotypes were intermediate in killing times to P. acutifolius and P. coccineus. Species response was not consistent with temperature within developmental stage. On average, the number of pods decreased as temperature increased from 32.2 to 37.3°C. Heat killing time and leaf damage also increased with temperature. CO₂ exchange rates of plants grown at prolonged high temperatures (30–40°C/20–30°C, day/night) decreased with the age of the plant. Shoot lenght was decreased as high temperature. P. vulgaris genotypes differed on the basis of either short term exposure or of continuous exposure. These results suggest that there may be useful germplasm in Phaseolus for improving heat tolerance.Scientific Journal Series Paper Number 13,8000 of the Minnesota Agricultural Experiment Station, USA.     

The Influence of the Arrangements of Pipes on Gas solid Flow Characteristics in the Dense Section of the Stand Pipe

The influence of the arrangements of pipes on gas solid flow characteristics in the dense section of standpipe in the circulating fluidized bed is studied on a cold state experiment platform.The influence relationships of the percentage of area of pipes in the standpipe cross section and section shape of pipes and the circulation rate,adjusting range and distribution percentage of loose air are studied emphasizedly.     

MgO对高铝高炉渣脱硫的影响及其动力学分析

随着廉价高铝铁矿石的不断使用,高炉炉渣内Al₂O₃含量也随之升高,这势必会影响高炉炉渣的各项冶金性能。为深入研究高铝高炉渣脱硫性能,明确MgO含量对高铝渣脱硫性能的影响,笔者通过改变高铝渣中MgO的含量,分别设定渣中MgO含量为5%、9%、13% MgO,研究不同MgO含量高炉高铝渣的脱硫性能及其脱硫动力学。结果表明：MgO含量不仅对高铝渣的黏度、脱硫能力有不同的影响,还使炉渣的脱硫速率发生了很大的改变。MgO含量越高对应的黏度越低,脱硫能力越大;但脱硫速率却表现出了不同规律,9% MgO的脱硫速率表现为最大;经过综合比较,当碱度固定为1.1、Al₂O₃含量固定为17%时,MgO含量为9%的炉渣同时具有较好的粘度和脱硫性能。