氧对锰铁渗氮的影响

应用X射线衍射、惰性气体熔融法氧氮分析等实验测试方法,研究了真空电阻炉高温渗氮粒度、温度、组成等因素对低碳锰铁和金属锰渗氮的影响.氮化试样的相组成为Mn4N、MnO和α-Mn,随渗氮时间的延长渗氮量相应增加.渗氮试样中均有一定的氧含量,渗氮试样的氧含量愈低,单位时间的增氮率愈高,氧含量是影响低碳锰铁和金属锰渗氮的重要因素之一.     

Mn—N相图和金属锰氮化

应用真空电阻炉高温渗氮、X射线衍射、惰气熔融法氧氮分析等实验测试方法,研究了粒度、温度等因素对金属锰渗氮的影响,热力学计算分析表明,高纯氢气在高温渗氮气氛中可有效抑制金属锰在渗氮的同时发生氧化,结合Mn－N相图和渗氮实验研究结果,氮含量低于Mn4N的计量组成时,渗氮试样的主要相组成为氮化锰稳定相Mn4N和残余金属α－Mn渗氮试样的氮含量大于Mn4N的计量组成时,主要相组成为氮化锰稳定相Mn4N和稳定相、ξ（计量组成约为Mn2N）。     

H13钢挤压模具双级氮化工艺研究

采用生产用氮化炉、金相显微镜、维氏硬度计等设备研究了双级氮化过程中氨分解率、氮化温度、氮化时间、炉压等氮化工艺对氮化质量的影响。结果表明：在批量H13钢挤压模具双级渗氮过程中,综合考虑氨分解率、氮化温度和保温时间对渗氮层的影响,首先要保证氮化温度,其次要保证氨分解率,（515℃保温6 h,37%氨分解率）+（535℃保温6 h,47%氨分解率）氮化工艺可以获得优良的渗层。     

含氮锰铁的生产方法

首先将商品硅锰(Si 含量14—25%)和低碳锰铁配制成含硅3—26%的锰合金(在此含硅量范围内,随着含硅量增加氮化温度上升,且含氮量随之增加)。然后球磨粉碎。其粒度在100—300目为最好。因为,太粗则渗氮慢;太细(如400目以上)则破碎时表面容易形成氧化膜,妨碍渗氮。把这些粉末加热并通入氮气进行渗氮。渗氮的温度最好低于氮化物分解的温度。但是,如果低于700℃则渗氮的速度变慢,且与合金中的含硅量无关;如果高于1400℃,则会产生夹杂。所以应控制在700—1400℃,最好在800     

钛表面气体氮化的工艺研究

研究了氮化温度、氮化时间、氮气压力和流量等因素对钛氮化反应的影响，确定了钛表面气体氮化的工艺参数，并对氮化覆层的相组成及各项性能进行了研究。     

C-HRA-5含Nb奥氏体耐热钢中氮的溶解行为研究

为实现C-HRA-5含Nb奥氏体耐热钢冶炼过程气相氮合金化精确控制,进行了0.033～0.1 MPa氮气压力和1 793～1 853 K下的气相渗氮实验,建立了含Nb耐热钢的氮溶解度模型和气相渗氮动力学模型。结果表明:通过考虑Cr、Ni与Nb对氮活度相互作用系数,含Nb奥氏体耐热钢的氮溶解度模型计算结果和实测值吻合良好,氮溶解度随冶炼温度升高而减小,随氮气压力增大而增大且符合Sieverts定律。气相-钢液间的渗氮动力学过程主要受界面化学反应速率控制,氮溶解反应速率常数随温度升高而增大,氮气压力则对其无明显影响,C-HRA-5钢的氮溶解反应速率常数可表示为lgk=2.1-7 889/T cm/(%·s)。     

金属锰粉氮化过程动力学研究

为研究金属锰粉的渗氮机理,采用热重分析法分别研究了等温和非等温条件下的氮气中,不同粒度的金属锰粉的氮化反应动力学。研究表明:金属锰粉发生氮化反应的起始温度和氮化锰的分解温度分别为470℃和1 016℃。同一粒度下,随着温度升高,表观速率常数增大,但饱和氮含量反而下降,出现吐氮现象;同一温度下,锰粉粒度越小,氮化速率越快,达到平衡的时间越短。金属锰粉粒度从40目降到100目,氮化反应的表观活化能从189.2 kJ/mol降低到115.2 kJ/mol。不同温度下和不同粒度金属锰粉的氮化过程中界面化学反应是整个过程的控制步骤。     

钛催化渗氮的新工艺方法

正实验结果表明,钛催化渗氮的新工艺方法与传统的气体氮化法或盐浴氮化法相比,具有化合物层厚度增加,表面硬度高,渗氮速度快,生产效率高的优点。是一种提高工具钢和模具钢性能的有效方法。钛催化渗氮的新工艺方法,对多种材料进行了渗氮处理。渗氮工艺可以有效提供工具的耐磨性和耐腐蚀性而被广泛使用,同时氮化还可提高抗热疲劳性和抗粘附性能。但普通氮化工艺的最大缺点就是渗层薄,而且工艺时间长、生产效率低。     

38CrMoAl渗氮钢表面镀铁及渗硼行为的研究

以38CrMoAl钢为研究对象,对其表面分别进行渗氮、镀铁以及渗硼处理。利用X射线衍射仪、光学显微镜、显微硬度计对渗氮层、镀铁层以及渗硼层进行表征分析。结果表明,采用镀铁和渗硼相结合的方法,可获得100μm厚的渗硼层,仅由Fe_2B单相组成,呈针齿状楔入基体,与基体牢固结合。38CrMoAl渗氮钢经镀铁渗硼处理后,其表面硬度得到显著提高,高达1 700 HV,明显高于普通氮化处理的38CrMoAl钢,从而达到了提高所修复材料表面性能的目的。     

锰铁氮化

在一台高温天平装置上对固态锰铁进行了氮化处理。氮化速度及吸氮量与温度、金属成分和粒度有关，在完全转化的物料中得到的含氮量在２．７－９．２ｗｔ％之间。相分析表明，低碳锰铁生成的是硅氮化物ＭｎＳｉＮ２和碳氮化物（Ｍｎ，Ｆｅ）４（Ｃ，Ｎ）的混合物，其相对数量取决于物料的初始成分，高碳锰铁的分析表明，是氮置换了（Ｍｎ，Ｆｅ）碳化物晶格中的碳，氮化速度主要取决于温度和粒度。     

Phosphorus distribution between rare earth oxides containing slags and ferromanganese alloy

In this paper, factors influencing the phosphorus distribution ratio between RE oxides containing slags and ferromanganese were studied. The results demonstrated that phosphorus distribution ratio values between RE oxides containing slags and ferromanganese are higher than those between CaO-based slags and ferromanganese. An increase in the temperature leads to a decrease in the phosphorus distribution ratio, and the downward trend is more pronounced when the temperature increases above 1673?K (1400°C). An increase of RE oxide content in the pre-melted slags, and of the oxygen partial pressure of the experimental system, improves the phosphorus distribution ratio. It was also found that when the Si content is below 0.25?wt-%, there is almost no change in the phosphorus distribution ratio; however, the phosphorus distribution ratio decreases as the Si contents increases further.     

Activation Energy of Nitriding Medium Carbon Ferromanganese Alloy

Investigation of some kinetics aspects of the reaction between nitrogen and medium carbon ferromanganese (MC-FeMn) was made. Nitriding process of fine medium carbon ferromanganese was carried out at temperature ranging from 973 to 1 223 K and time up to 480 min. Nitriding was carried out under nitrogen and hydrogen gas pressures. At temperature of 573 K, hydrogen gas was injected with pressure of about 0.2 MPa followed by injection of nitrogen gas up to 1.2 MPa. Sample mass was 35 g, nitrided in cylindrical chamber with 34 mm in inner diameter and 1 200 mm in length. The change in nitrogen pressure was taken as an indication for nitrogen pickup. The mass gain i.e. nitrogen pickup in kilograms per surface area (m2) was determined by time at different temperatures. Nitriding rate constants were calculated and the activation energy of nitriding process was derived from Arrhenius equation. The nitriding rate constant was found to be increased by increasing temperature of the reaction. The activation energy of nitriding process of fine medium carbon ferromanganese at time ranging up to 28 800 s is around 140 kJ/mol. It was found that the rate controlling step of the nitriding process of MC-FeMn is diffusion mechanism.     

Decarburization Thermodynamics of High-Carbon Ferromanganese Powders During Gas-Solid Fluidization Process

 Thermodynamic conditions of reactions between high-carbon ferromanganese powders and gas decarbonizers like O2, CO2 and water vapor were studied by thermodynamic calculation. In O2, CO2 and water vapor atmosphere, high-carbon ferromanganese powders were decarburized in a fluidized bed. When the temperature is respectively higher than 273, 1226 and 1312 K, the gas-solid decarburization reaction will occur between ferromanganese carbide on the surface of the high-carbon ferromanganese powders and different gas decarbonizers. Since metal manganese is easy to be oxidized by O2, CO2 or water vapor, the decarburization reaction will transfer into a solid-solid phase reaction of ferromanganese carbide and ferromanganese oxide, promoting external diffusion of carbon to achieve a further decarburization of high-carbon ferromanganese powders.     

VOD精炼316L不锈钢吹氮合金化的研究

用0.8 kg钢水石墨坩埚的硅钼棒炉研究了常压下氮气分压(33～100 kPa) 、吹氮时间(0～50 min) 、吹氮流量(0.3 L/min) 、钢液温度(1 773～1 833 K)对316L钢(%:0.031C、16.13Cr、10.12Ni、2.12Mo、0·028N)中氮含量的影响,并试验了在前期真空条件下1 853～1 833 K吹氮40 min、2 kPa、0.1 L/min,中期吹氮40 min、100 kPa、0.3 L/min,后期吹氮50 min、100 kPa、自然冷却至1 773 K时316L钢水的增氮行为。结果表明,钢中氮含量随着吹氮时间、氮分压的增加而增大,常压下吹氮10 min,钢液含氮量即可超过0.10%,随吹氮流量增加钢液达到饱和的时间缩短,氮的溶解度随着钢液温度的降低而升高。应用热力学和动力学模型进行了分析。     

Thermodynamics of carbon in liquid manganese and ferromanganese alloys

The thermodynamics of carbon in manganese and ferromanganese melts were studied to predict the refining limit of carbon during the decarburization of molten ferromanganese. The equilibrium carbon content in a Mn-C melt was determined by the C-CO equilibrium in the presence of pure solid MnO at 1673 to 1773 K. The activities of manganese and carbon in the Mn-C melt were then calculated from the experimental results, the equilibrium constant for the reaction, and the Gibbs-Duhem equation integrated by the Belton-Fruehan treatment. The standard free-energy change of carbon dissolution in the manganese melt was determined to be 41,700 — 59.6 T J/g · atom, with the standard state taken as 1 wt pct carbon in solution. The effect of iron on the activity coefficient of carbon in ferromanganese was determined by measuring the carbon solubility in Mn-Fe melts. The first- and second-order interaction parameters between carbon and iron in ferromanganese melts were determined. The activity coefficient of carbon in the ferromanganese alloy melt can be expressed as

高氮Fe-Cr-Mn-Ni系奥氏体不锈钢的加压感应熔炼

采用MgO坩埚高频真空感应炉在氮气压力0.45~1.0MPa、温度1640~1700℃下,对加压感应熔炼高氮Fe-Cr-Mn-Ni系奥氏体不锈钢进行了实验研究。结果表明,1913K、1.0MPa氮气氛中Cr12、Cr17Mn5Ni5、Cr19Mn15和Cr20Mn8不锈钢中氮的溶解度分别为0.391%、0.692%、1.120%和0.899%,氮在液态不锈钢中的溶解与Sievert定律有所偏离;氧浓度在350×10^-6内,1913K、1.0MPa氮气氛中Cr20Mn8钢液的吸氮反应仍为一级反应,其传质系数为0.023cm·s^-1;随钢中氧浓度的增加,液态钢的吸氮速率和钢液中的平衡氮含量显著降低。     

Dephosphorisation of ferromanganese alloy using rare earth oxide-containing slags

The phosphates of rare earth (RE) metals are highly stable in natural environment, and RE oxides have higher optical basicity than CaO and BaO. Therefore, the thermodynamic conditions for dephosphorisation using RE oxide-containing slags are expected to be favourable. Factors influencing the efficiency and Mn loss during the dephosphorisation of ferromanganese using RE oxide-containing slags were studied. An increase in the dephosphorisation temperature up to 1673?K (1400°C) is beneficial to the process and decreases Mn loss, and the maximum degree of dephosphorisation for slags containing 6 wt% RE oxides are 47.44 and 50.85%, corresponding to the minimum values of Mn loss are 1.64 and 1.35% at 1673?K (1400°C); further temperature increases would deteriorate the dephosphorisation efficiency and lead to an obvious increase in Mn loss. An increase in the quantity of pre-melted slags, and of their RE oxide content, improves the dephosphorisation efficiency but inevitably leads to a more pronounced Mn loss. It was also found that an increase in Si contents above 0.25 wt% in the ferromanganese alloys not only deteriorates the dephosphorisation efficiency but also increases the Mn loss; and the dephosphorisation efficiency decreases to almost zero when the silicon content increases up to 0.62 wt%.     

Nitrogen solubility in liquid manganese and ferromanganese alloys

The nitrogen solubilities in liquid manganese, manganese-iron, manganese-carbon, and manganese-iron-carbon alloys have been measured by the gas-liquid metal equilibration technique in the temperature range of 1623 to 1823 K. The equilibrium nitrogen content in pure liquid manganese at an atmospheric nitrogen pressure is high, and it does not follow Sievert’s law, i.e., f _N is not unity. The reduced nitrogen partial pressures by dilution with argon enabled us to obtain more reliable information on the thermodynamics of nitrogen in liquid manganese. The nitrogen dissolution follows Sievert’s law at nitrogen contents below 1 wt pct. The standard free-energy change for the dissolution of nitrogen in pure liquid manganese has been determined as −67,222+30.32T J/g atom, with the standard state of nitrogen taken as a 1 wt pct solution. Carbon and iron in manganese-rich melts decrease the nitrogen solubility significantly. The first- and second-order interaction parameters between nitrogen and other elements in manganese alloy melts have been determined. The activity coefficient of nitrogen in a ferromanganese alloy melt can be expressed as

Different Approaches for the Development of Low-Cost CO2 Adsorbents

Different carbon materials were tested as precursors for the production of CO2 adsorbents. The chemical modification of the surface of the prepared adsorbents was studied by means of three different approaches: impregnation with amines, electrophilic aromatic substitution, and heat treatment in the presence of ammonia. The samples were chemically characterized and the porous texture was evaluated from the N2 adsorption isotherms at ?196°C. The CO2 adsorption capacities of the adsorbents at 25 and 100°C were evaluated in a thermogravimetric analyzer. In general, the incorporation of basic nitrogen functionalities enhanced the CO2 capture capacities of the modified carbons, but this increase depended on the textural properties of the support and the surface modification methodology. CO2 adsorption capacities of up to 111?mg CO2/g at room temperature were attained. All the tested samples were completely regenerated when subjected to heat treatment at 100°C under inert atmosphere.     

稀土氨氮废水治理及资源化集成技术的研究

以吸附法与化学沉淀法的集成技术组成氨氮废水处理的闭路循环系统,用自制的MgHPO4(MHP)为吸附剂,对NH4+浓度为5175mg/L稀土硫酸铵废水进行了氨氮吸附性能实验,研究发现pH、MHP的投加量和氨氮初始浓度是影响氨氮去除效果的关键因素。在室温下,调节反应体系pH=9.5,MHP用量按摩尔比n(MHP)∶n(NH4+)=2∶1投料,搅拌吸附30min,氨氮去除率可达85.7%,且氨氮初始浓度越高,吸附效果越好。MHP再生与循环使用实验表明,MAP焙烧可使MHP再生,同时可回收高浓度的氨水,MHP循环使用三次,氨氮的去除率均在70%以上。如果采用MHP二级吸附法后,再用MAP沉淀法处理废水,可使出水氨氮浓度降低为87mg/L,累计氨氮去除率可达到98%以上。