奥氏体不锈钢中氮溶解度的热力学计算和实验研究

采用热力学分析方法,对固态不锈钢304、304L、301S和301L(γ-相)以及奥氏体不锈钢熔体中氮溶解度进行了计算,得出了氮溶解度的计算模型;同时通过1 kg MoSi电阻炉对4种奥氏体不锈钢在1520～1580℃和33～100 kPa压力下的渗氮行为进行了实验研究。结果表明,氮在固态奥氏体不锈钢的γ-相中的溶解度最高;在常压冷却、凝固过程中存在的液相、δ-相至γ-相的转变;当不锈钢熔体中相对于δ-相过饱和的氮在钢中以气泡形式析出,则降低了奥氏体钢的氮含量,所以采用常压快速冷却或加压浇注有利于冶炼高氮奥氏体不锈钢。     

高氮不锈钢研究的发展近况

介绍了国内外高氮不锈钢研究近期的成果,内容涉及高氮不锈钢基础研究、力学性能、耐腐蚀性能、焊接性及高氮不锈钢新材料,反映了国内外高氮不锈钢研究的发展状况.鉴于高氮不锈钢卓越的综合性能而国内高氮钢研究已远远落后于国际发展水平的现状,应尽快在国内建立高氮钢试验装置,加快国内高氮不锈钢基础理论、生产工艺技术(特别是冶炼技术)和新材料的研究,把握不锈钢发展的方向,为中国不锈钢的发展提供有力的支持.     

粉末冶金高氮不锈钢的研究与发展现状

本文介绍了高氮不锈钢的优点及制造方法,总结了粉末冶金高氮不锈钢的制粉及成形方法.介绍了粉末冶金高氮不锈钢的应用领域及前景.     

304不锈钢熔体氮溶解度的测定

介绍并比较了纯铁液中氮溶解度测定方法--直接法和间接法,并在经典的间接法的基础上,重新设计了气体氮的配气、控制和计量系统,以及渗氮的方式.用该方法测定了304不锈钢熔体在不同温度和氮分压下的氮的溶解度值.     

高氮不锈钢的开发进展

加压冶炼高氮不锈钢是材料研究的一个新领域。介绍了高氮不锈钢的生产工艺及高压冶炼高氮不锈钢的主要设备。综述了欧美、日本等研发的高氮不锈钢的成分、力学性能及应用现状。由于受试验装备的限制,国内高氮不锈钢的研究与国外相比还有差距。针对高氮不锈钢具有多种优良性能,以及氮应用于对人体无害的生物、医疗材料方面前景广阔,提出医疗用高氮不锈钢将成为理想的生态材料。     

直读光谱仪快速分析不锈钢中氮含量准确度的研究

本文探讨直读光谱仪分析铬不锈钢中氮含量的方法,通过优化试样加工工艺及分析曲线,实现了铬不锈钢中氮的快速分析。分析结果表明,该方法可以快速准确分析铬不锈钢中的氮含量,适合炉前的快速生产。     

无磁钻铤用高氮不锈钢TSMF166冶炼实践

通过无磁钻铤用高氮不锈钢TSMF166冶炼实践,开发出低碳高锰冶炼和VOD+ LF组合增氮两项技术,将大部分锰合金加入时间移至VOD脱碳后,用廉价的氮气替代氮化合金,100％用氮气进行氮合金化,解决TSMF166钢冶炼中碳、锰、氮含量的控制问题,缩短K-OBM-S转炉、VOD真空精炼和LF生产周期,提高钢质纯净度,降低生产成本,彻底消除在LF加氮化锰增氮产生的巨大烟尘给环境带来的严重污染.VOD+ LF组合增氮技术既经济又环保,值得在生产中高氮不锈钢上推广或借鉴.     

低镍不锈钢生产中的若干冶金学问题

高氮低镍不锈钢具有良好的强度、延展性及耐腐蚀性能，且可以降低晶界的腐蚀敏感性。同时，以低成本的氮代替昂贵的镍可以降低生产成本。简要回顾了我国及世界不锈钢产业的发展历程，分析了低镍不锈钢中氮的作用及不锈钢中加氮工艺等一系列问题，并对不锈钢生产中存在的若干冶金学问题进行了总结。     

高氮不锈钢粉末冶金制备技术的研究进展

高氮不锈钢作为一种重要新型工程材料,具有优异的力学性能和耐腐蚀性能,受到国内外广泛重视。介绍了粉末冶金制备高氮不锈钢的原理和特点;论述了高氮不锈钢粉末的制备与成形技术;指出了利用粉末冶金制备高氮不锈钢所具有的技术优势,其中注射成形——氮化烧结工艺更具发展潜力。     

高氮不锈钢粉末冶金制备技术的研究进展

高氮不锈钢作为一种重要新型工程材料,具有优异的力学性能和耐腐蚀性能,受到国内外广泛重视。介绍了粉末冶金制备高氮不锈钢的原理和特点;论述了高氮不锈钢粉末的制备与成形技术;指出了利用粉末冶金制备高氮不锈钢所具有的技术优势,其中注射成形——氮化烧结工艺更具发展潜力。     

The Nitrogen Solubility in Molten Stainless Steel

Nitrogen solubility in the austenitic stainless steel melts was measured in the laboratory by bubbling nitrogen gas under different partial pressures of nitrogen and temperatures. A new thermodynamic model for the calculation of nitrogen solubility in molten stainless steel in a wide range of alloy concentrations, temperatures, and pressures has been successfully established by introducing a new term for the effect of pressure on the nitrogen activity coefficient. The calculation results were in good agreement with the measured values. The influences of temperature, nitrogen partial pressure and chemical composition on the nitrogen solubility in molten stainless steel are discussed based on the calculated results. It is possible to produce high nitrogen steels at normal pressure by optimizing the design of the alloy composition and controlling the lowest melting temperature from a thermodynamic point of view.     

Production of Nitrogen-Bearing Stainless Steel by Injecting Nitrogen Gas

 To replace nickel-based stainless steel, a nitrogen-bearing stainless steel was produced to lower the production cost stemming from the shortage of nickel recourses. Thermodynamic model to calculate the saturated nitrogen content in the stainless steel was developed and the model was validated by experimental measurements performed with a high temperature induction furnace. Nitrogen gas under constant pressure was injected into the molten steel with a top lance. Thus, the nitrogen was transferred to the molten stainless steel. The effects of chemical composition, temperature, superficial active elements and nitrogen flow rate on the transfer of nitrogen to the steel were investigated and discussed. The results showed that the dissolution rate of nitrogen in the molten steel increases with a higher temperature and larger nitrogen flow rate but decreases significantly with an increase in the content of surface-active elements. Alloying elements such as chromium and manganese having a negative interaction coefficient can increase the dissolution of nitrogen in the molten steel. It was also proposed that the primary factor affecting the final saturated nitrogen content is temperature rather than the dissolved oxygen content.     

不锈钢控氮理论计算与实践

采用不同的氮在钢中的溶解度公式,计算了两种含氮不锈钢冶炼时所需要的氮气压力,并在50kg真空感应炉上,通过改变氮气压力,对两种不锈钢进行了氮含量控制实践。结果表明,采用Fujio测定值的理论计算值与试验实测值吻合度较高,同时给出了钢中氮含量的理论计算公式。     

粉末冶金制备高氮不锈钢的研究进展

概述了加压冶炼制备高氮不锈钢存在的问题,介绍了粉末冶金制备高氮不锈钢的发展现状,其中包括高压气雾化法、机械合金化法等高氮不锈钢粉末制备技术,和注射成形、热等静压成形、热挤压、粉末包套烧结–自由锻造、等离子烧结成形等高氮不锈钢粉末致密化及成形技术,指出了粉末冶金制备高氮不锈钢存在的问题,并对其未来的发展趋势进行了预测。     

Development and application of nitrogen-alloyed austenitic stainless steels in Baosteel

In recent years,nitrogen-alloyed stainless steels have been a research hotspot in the field of stainless steel product and technology. Nitrogen-alloyed austenitic stainless steels developed by Baosteel and their applications are introduced. These steels are nitrogen-controlled products 304 N and 316 LN,nitrogen containing economical products BN series and high-nitrogen stainless steel( HNS) series. The results show that the presence of nitrogen can significantly improve the strength and corrosion resistance of steel produced. By nitrogen alloying,economical austenitic stainless steels w ith considerably less nickel than 304 can be obtained; the corrosion resistances of these steels are almost the same as 304. Furthermore,by a scientific approach of nitrogen alloying,high-nitrogen steel of0. 8% nitrogen content is fabricated under the non-pressurized conditions,and the pitting potential of this steel is 1. 0 V. At present,nitrogen-alloyed steels developed by Baosteel are w idely utilized in the manufacture of cryogenic storage containers,transportation containers,and many household w ares.     

Effect of Grain Size on Mechanical Properties of Nickel-Free High Nitrogen Austenitic Stainless Steel

The fine grained structures of nickel-free high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing.The relationship between microstructure and mechanical properties and gain size of nickel-free high nitrogen austenitic stainless steels was examined.High strength and good ductility of the steel were found.In the grain size range,the Hall-Petch dependency for yield stress,tensile strength,and hardness was valid for grain size ranges for the nickel-free high nitrogen austenitic stainless steel.In the present study,the ductility of cold rolled nickel-free high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined.The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.     

粉末冶金高氮不锈钢的研究现状

综述了粉末冶金高氮不锈钢的优点和所采取的主要工艺及国内外研究现状。系统总结了高氮不锈钢粉末的制备工艺和固化成形工艺。重点介绍了注射成形-烧结渗氮工艺,分析了部分产品的性能及应用前景,指出注射成形-烧结渗氮工艺是十分有潜力的制备高氮不锈钢的途径     

High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

 A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe Cr Mn Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 069% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 081%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃×1 h followed by water quenching, the microstructure consisted of homogeneous austenite.