高氮不锈钢的试制

不锈钢的高氮化不仅可提高钢的耐蚀性 ,而且可促进奥氏体相的稳定化和取代贵金属 Ni,从而达到产品品质与成本方面的双收益 ,然而 ,高氮不锈钢的生产必须在加压气氛下进行。目前 ,其制造方法主要有加压感应炉法、加压等离子炉法和加压电渣炉法 3种方式。现在欧洲已有 2 0 t/ 42× 10 5Pa的加压电渣炉在运行。概述了上述 3种高氮不锈钢制造法的原理、设备结构与特点。作为小规模高 N不锈钢制造技术的研究 ,着重对加压感应炉方式的熔炼方法、试验材料、试验设备与条件及其试验结果作了介绍。图 12表 5参 4高氮不锈钢的试制@陈留根…     

降低电炉管线钢氮含量生产工艺摸索

对绝大多数管线钢来说,氮是有害元素,钢水中氮含量偏高会使钢产生应力时效,降低管线钢的成型性及高温韧性、塑性和焊接性能。介绍了电炉冶炼高端管线钢钢水中氮元素来源,主要为废钢原料含氮不稳定以及电弧区钢液容易吸氮,并通过冶炼工艺的比对,对电炉不同钢渣性能、不同铁水比例、冶炼时熔池流场对N含量的影响进行了分析,找出控制电炉钢水氮含量的有效途径,主要有提高电炉钢渣性能、合理的铁水配比、电炉底吹CO2气体、精炼、连铸防二次增N工艺等,工艺改进后氮含量平均控制在8×10-5以下。     

奥氏体氮碳共渗加时效工艺研究与应用

本文研究了低碳易切钢的奥氏体氮碳共渗,再经180～340℃温度范围,进行不同温度和不同保温时间的人工时效。观察了其显微组织的变化,测试了其ε相化合物层、奥氏体淬火层的显微硬度及其机械性能。结果表明:低碳易切钢经奥氏体氮碳共渗比常规铁素体氮碳共渗得到更厚的ε相化合物层,且可获得常规铁素体氮碳共渗所没有的奥氏体淬火层;经恰当的人工时效可显著提高其内侧ε相化合物层及淬火层的硬度。分析了该新工艺在现代工业中的适用范围及应用前景。     

高氮钢热加工性能研究

对Mn18Cr18N高氮钢进行不同温度下的固溶处理,通过扫描电镜SEM对组织进行观察和分析,试验结果表明热处理温度对材料的组织形态起决定性作用,在温度不低于1 150℃时,钢中奥氏体组织占绝大部分;同时在Gleeble-1500热模拟机进行热模拟试验,对Mn18Cr18N高氮钢的高温塑性进行了研究,在1 150~1 250℃时塑性最好,断面收缩率超过60%,是热加工的最佳温度区间;对高温下的断口形貌进行分析得出拉伸过程中的变形方式不仅有位错滑移,还伴有形变孪晶方式。     

GCr15钢LF增氮因素分析及措施

分析了GCr15轴承钢“LD→ LF→ VD→ CC”生产工艺中的氮含量情况及LF精炼过程中钢水增氮的原因.结果表明,LF精炼阶段的“原材料”和“钢液裸露”是造成钢液增氮的最主要原因.提出了GCr 15轴承钢LF精炼过程控氮措施,通过工业试验,降低了精炼过程氮的增加,使成品氮含量得到有效控制.     

小议不锈钢材料在换热设备中的应用

不锈钢也叫不锈耐酸钢,因其防腐性能好、颜色美观、综合效益经济合理,在化工方面应用越来越广.不锈钢按其组织结构分为马氏体不锈钢、铁素体不锈钢、奥氏体不锈钢.其中,奥氏体不锈钢以其优异的综合性能,近些年常常在建筑领域的换热给水等压力设备中采用.奥氏体不锈钢的典型品种-S30408(既18-8型)应用最多,但由于部分用户对奥氏体不锈钢的使用限制条件不太清楚,造成设备投入运行后短期内就产生严重腐蚀甚至导致设备报废,造成很大的经济损失.     

高氮钢电渣重熔夹杂物控制研究

对高氮钢电渣重熔前后夹杂物进行对比研究,分析不同渣系和自耗电极氧含量对重熔后夹杂物的影响。研究发现,不同渣系对电渣钢的洁净度影响很大,适当提高w(Ca O)/w(Al2O3)可有效降低电渣锭中的夹杂物和全氧量。对高氮钢电渣重熔的脱硫进行研究,分析了不同渣系和熔炼速率对高氮钢脱硫率的影响,实验结果表明:电渣重熔后,硫化物夹杂的平均直径和单位面积数量大大减少,夹杂物的主要类型为Mn S+Al2O3复合型夹杂物,同时适度提高渣中Ca O含量实现提高硫分配比是提高脱硫效率的有效手段。脱硫动力学推导中发现重熔速率越低,脱硫效果越明显,但实验发现脱硫率随重熔速率的降低呈现先降低后升高的趋势,其原因在于渣池中发生硫化物富集,导致"回硫"现象发生。     

新型奥氏体耐热钢与马氏体耐热钢焊接工艺探究

高铬镍奥氏体不锈钢与高合金马氏体耐热钢在成分、组织和性能上的差别很大,所以焊接异种钢时会遇到一些特有的问题。对焊后进行热处理及热处理参数进行对比研究,可以为工程实际应用提供参考。     

奥氏体不锈钢与珠光体耐热钢异种钢焊接研究

本文主要介绍大型电站锅炉受热面管系,奥氏体不锈钢与珠光体耐热钢,异种钢焊接工艺和异种钢焊接接头的机械性能研究结果,对实际生产有一定参考意义。     

SAF2205双相不锈钢焊接残余应力有限元分析

双相不锈钢是基于石油化工行业中强酸强碱易造成局部点蚀、应力腐蚀以及孔穴腐蚀现象，采用一般不锈钢难以胜任而研制开发的。双相不锈钢具有奥氏体和铁素体混合组织。奥氏体的存在降低了高铬铁素体的脆性、氢脆和晶粒长大倾向，提高了可焊性和韧度。而富铬铁素体则又提高了奥氏体的屈服强度、抗晶问腐蚀和应力腐蚀能力。     

Effects of nitrogen and argon on ammonia-oxygen explosion

The primary task of this work is to clarify ammonia-oxygen explosion characteristics under nitrogen and argon atmosphere. Firstly, the flame behavior and explosion pressure are experimentally obtained. Then their correlation is revealed quantitatively. The thermal, diffusive and chemical analysis is conducted at last. The results demonstrated that the variation tendency of flame propagation velocity (FPV), maximum explosion pressure (MEP) and maximum rate of pressure rise (MRPR) is completely consistent. All index of FPV, MEP and MRPR, becomes increased and decreased with increasing equivalence ratio, continues to decrease with increasing inert gas fraction. All index of FPV, MEP and MRPR under argon atmosphere is totally larger than that under nitrogen atmosphere. By considering the state equation of ideal gas, spherically smooth flame and adiabatic compression, the flame behavior and explosion pressure under nitrogen and argon atmosphere is significantly controlled by laminar burning speed (LBS). As the inert gas fraction and equivalence ratio change, the LBS under nitrogen and argon atmosphere is significantly controlled by adiabatic flame temperature. The joint action of adiabatic flame temperature and thermal diffusivity contributes to the LBS difference.     

秸秆再燃还原氮氧化物的分析研究

秸秆是一种可再生能源,在我国有着广泛的来源。再燃技术是目前控制NOx排放的主要方法之一,针对燃料再燃降低NOx排放的原理,对秸秆再燃降低NOx生成进行了分析研究。主要是关于秸秆的C、H、N、S的含量和挥发分含量对NOx还原效果的影响,以及秸秆再燃的经济效益;其次是由于秸秆的燃烧特性,当秸秆再燃时可能产生的问题及解决方法进行了分析。结合国内外的研究现状,提出了对我国中,大型锅炉实行秸秆再燃的可行性和实用性。     

生物炭的制备及其对氮肥吸附效果的研究

以玉米秸秆为原材料,分别在350、400、450℃下炭化3 h制备玉米秸秆生物炭(分别命名为B350、B400、B450),利用X射线衍射仪、扫描电镜仪、比表面积及孔径分布仪、红外光谱仪等对材料进行表征,确定材料的相关性能,并探讨其与氮肥吸附的相关性。以平衡实验法研究了溶液pH对生物炭吸附氨氮的影响。实验结果表明:玉米秸秆生物炭B350、B400、B450对氨氮的吸附过程均遵循二级吸附动力学模型,且采用Langmuir方程能更好地描述吸附等温线模型;玉米秸秆生物炭对氨氮的饱和吸附量按从大到小依次为B400、B350、B450,且均为有利吸附;玉米秸秆生物炭对氨氮吸附的最佳pH为8～12。     

Effect of nitrogen on deflagration characteristics of hydrogen / methane mixture

In order to study the influence of nitrogen on the deflagration characteristics of premixed hydrogen/methane, the explosion parameters of premixed hydrogen/methane within various volume ratios and different dilution ratios were studied by using a spherical flame method at room temperature and pressure. The results are as follows: The addition of nitrogen makes the upper limit of explosion of hydrogen/methane premixed gas drop, and the lower limit rises. For explosion hazard (F-number), hydrogen/methane premixed fuel with a hydrogen addition ratio of 10% has the lowest risk, and nitrogen has a greater impact on the dangerous degree of hydrogen and methane premixed gas whose hydrogen addition ratio does not exceed 30%. In terms of flame structure, the spherical flame was affected by buoyancy instability as the percentage of nitrogen dilution increased, but the buoyancy instability gradually decreased as the percentage of hydrogen addition increased. The addition of diluent gas reduces the spreading speed of the stretching flame and reduces the stretching rate in the initial stage of flame development. The laminar flame propagation velocity calculated by the experiment in this paper is consistent with the laminar flow velocity of the hydrogen/methane premixed gas calculated by GRI Mech 3.0. Considering the explosion parameters such as flammability limit, laminar combustion rate and deflagration index, when hydrogen is added to 70%, it is the turning point of hydrogen/methane premixed fuel.     

氮源和无机盐对酵母菌发酵酒精浓度的影响

在ypd培养基条件下,研究了尿素这种氮源对酒精发酵的影响,发现其对酵母菌发酵生成酒精的最佳浓度值为9.6g/L.并对5种发酵无机盐硫酸镁、硫酸锌、氯化镁、氯化铁、磷酸二氢钾的浓度与发酵酒精浓度之间的关系进行研究,初步找到了该株酵母所需无机盐的临界值,分别是硫酸镁为4.8g/L,磷酸二氢钾为4.8g/L,氯化镁为4.8g/L.添加硫酸锌、氯化铁的两组实验得到的乙醇产量明显比其他组要低,此酵母菌发酵随浓度的增大乙醇产量降低,由此推断硫酸锌、氯化铁对此种酵母菌发酵有着制约作用.     

Effects of CaO on nitrogen transformation during pyrolysis of soybean protein

To elucidate the effects of CaO on nitrogen transformation during sludge pyrolysis, transformation behavior from char N into NO_x precursors during pyrolysis of soybean protein (SP) with CaO at 600–700°C was investigated. Results showed that CaO inhibited the transformation of pyridine N and quaternary N into HCN and promoted HCN conversion into NH₃ at 600–700°C. CaO inhibited the conversion of protein N and tar N into NH₃ at 600°C but promoted it at 700°C. NO_x precursor yield was the lowest when SP was pyrolyzed with CaO/N of 5.5 at 600°C (reduced by 11.66% compared with raw SP pyrolysis).     

Boiling and spreading of liquid nitrogen and liquid methane on water

An experimental and theoretical investigation was carried out to study the boiling and spreading of liquid nitrogen and liquid methane on water, in a one-dimensional configuration. With the equations of continuity and momentum transfer, a mathematical model was developed to describe the boiling-spreading phenomena of cryogens spilled on water. The model accounts for a decrease in the density of the cryogenic liquid due to bubble formation. Experimental spreading fronts were successfully simulated by assuming constant evaporation rates (40 kW/m² and 92 kW/m² for nitrogen and methane respectively) in the theoretical model. The model predicts the maximum spreading distance and the time for complete vaporization.     

Wood ash and nitrogen influence on ground vegetation cover and chemical composition

An experiment was set up in a 38-year-old Scots pine stand (forest type Pinetum vacciniosum) on a sandy soil (Haplic Arenosol). Raw wood ash (WA) and nitrogen (N) fertilizers were applied. There were 6 treatments: (1) 1.25 t WA ha⁻¹; (2) 2.5 t WA ha⁻¹; (3) 5.0 t WA ha⁻¹; (4) 180 kg N ha⁻¹; (5) 2.5 WA t ha⁻¹ together with 180 kg N ha⁻¹; and (6) control (without ash or N). The effects on ground vegetation cover, biomass and chemistry of Pleurozium schreberi (Brid.) Mitt. were studied.The ground vegetation cover measurements were performed from the initial phase of the experiment and continued annually in all treatments. The ground vegetation biomass and the concentrations of the main plant nutrients (N, P, K, Ca and Mg) and some heavy metals (Cr, Cd, Pb, Ni, Cu and Zn) were determined in the 5.0 t WA ha⁻¹ and 180 kg N ha⁻¹ plots 2 years after the application.The study results showed a significant reduction of the moss cover after the application of wood ash, and the higher ash dose gave a higher decrease. N and wood ash applied together with N also decreased the cover of the moss. Small changes in the mean cover of the vascular plants occurred after the N application. The biomass of the moss remained unaffected. Significant increases of the P, Ca and Mg concentrations in P. schreberi were found after the application of 5.0 t WA ha⁻¹, and also higher N concentrations were obtained after N application. No wood ash influence on the heavy metal (Cd, Pb, Cr, Ni, Cu and Zn) concentrations in P. schreberi was found.     

Enhanced electrocatalytic activity of platinum supported on nitrogen modified ordered mesoporous carbon

Nitrogen-modified ordered mesoporous carbon is synthesized via the 900 °C carbonization of polyaniline-coated mesoporous carbon. The electronic states of nitrogen atoms are investigated by XPS technique. Pyridinic nitrogen and quaternary nitrogen generate disorders and curvatures on the surface of graphitic carbon layers with nitrogen atoms replacing carbon atoms at the edges and the interior of carbon stacking, and thus offering beneficial anchoring sites for PtCl₆²⁻ ions. Pyridinic nitrogen and pyrrolic nitrogen offer p electrons to the sp² hybridized graphitic carbon layers, decreasing the inner electrical resistance of the catalytic carbon layer, enhancing the rate of proton diffusion, and transporting more free electrons to oxidative platinum. Due to the advantageous modification of the electronic structure of carbon atoms, platinum nanoparticles with a narrow size distribution are homogenously dispersed onto the surface of nitrogen-modified ordered mesoporous carbon, as evidenced by TEM images. Electrochemical tests show that the samples loaded platinum calcined at the 900 °C exhibit the optimum loading performance among as-made catalysts and a gradually decreased decay in electro-catalytic activity with time, with the current density stabilized at 3.64 mA cm⁻², which is far higher than that of mesoporous carbon (0.15 mA cm⁻²).