60t VD炉脱氢工艺优化实践

影响60tVD炉脱氢效果的主要因素有真空度、熔渣、吹氩流量和压力、原始[H]含量等,通过优化脱氢工艺,抽真空时,蒸汽压力稳定在0.80～0.85MPa,真空度67Pa以下,真空保持时间一般钢种8～10min、氢敏感性钢种10～12min、特殊要求钢种15min,吹氩压力≥0.20MPa,吹氩流量≥150L/min,钢中氢含量控制在了2.5×10-6以下,使单工位VD炉满足了快节奏生产的需求。     

Behaviour of Hydrogen in Industrial Scale Steel Melts

The behaviour of hydrogen during controlled industrial scale secondary steel making process has been examined in a variety of low alloy steels, sensitive to hydrogen flaking. The study examines the role played by the moisture in input raw materials such as the ferro-alloys, type of carbon additive and fluxes in enhancing the hydrogen content in the ladle furnace. Post alloying, the influence of vacuum degassing parameters such as the vacuum level, vacuum holding time, Ar flow rate, type of porous plug used, slag chemistry and the steel grade was examined. The vacuum degassing process was analysed using a kinetic model, which could justify the trends seen in the vacuum level, holding time and Ar gas flow rate. Finally, the hydrogen pick-up post vacuum degassing through slag cover and the casting tundish was found to be influenced by parameters such as the quality of the tundish spray mass, and casting sequence. The influence of steel grade in hydrogen removal was also examined.     

90t钢包精炼炉脱氢工艺探讨

选择两种脱气工艺对ＬＦ－ＶＤ精炼炉脱氢进行了试验,结果表明：真空脱气时用吹氩搅拌工艺比电磁搅拌结合吹氩工艺更合理;现有工艺通过调整真空时间可以有效地控制钢中［Ｈ］;要缩短真空时间必须加大吹氩量。     

超纯轴承钢的精炼工艺

通过控制电炉(供氧强度、渣中氧化铁比例、出钢挡渣率、出钢钢液的氧活度)、钢包炉(精炼渣系、脱氧剂、钢液温度、精炼时间、底吹氩压力、精炼钢包耐火材料的选择、铁合金种类的选择)、真空脱气(真空度、真空时间、底吹氩压力)的工艺参数以及真空后的软吹氩搅拌、并采用IPAS系统和控制钢液浇铸速度,使超纯轴承钢(SFGCr15)的w(S)、w(Ti)、w(O)分别达到0.003%、0.001 2%和0.000 7%以下,钢中非金属夹杂物也处于较好水平,满足了国际顶尖轴承厂家对轴承钢的超纯要求.     

Novel rapid discharge sintering technique for damage-free diamond metal matrix composites

Abstract

The performance of diamond/nickel metal matrix composites (MMCs) produced using a novel microwave plasma technique, rapid discharge sintering (RDS), and conventional tube furnace sintering in argon is compared. The MMCs were sintered at temperatures between 850 and 1050°C in both cases. The RDS treatments were carried out at 20 mbar in plasmas containing hydrogen or hydrogen–nitrogen gases. The addition of nitrogen gas to the hydrogen plasma facilitated a substantial increase in composite firing temperatures. A significant reduction in sintering times, to 10 min from several hours, was achieved using the RDS technique. A further advantage of the RDS treatments was the absence of any diamond graphitisation (as detected by X-ray diffraction), which was reflected in higher sintered densities and flexural strength for RDS than for furnace sintering.     

Hot plastic deformation of 08X21H5T steel

The nonuniformity of hot plastic deformation of 08X21H5T steel is studied. Tensile tests are conducted in the vacuum chamber of the IMASH-20-75 Ala-Too machine. The samples are attached to a clamp in the chamber by means of straps. A junction of a platinorhodium–platinum thermocouple is soldered to the side surface of the sample. Air is pumped out of the chamber to a residual pressure of 5.0 × 10^–5 mm Hg (6.7 × 10^–3 Pa). The sample is heated to 800–1200°C by means of industrial-frequency current. The precision of temperature maintenance is ±5°C. The deformation of the austenite and ferrite phases is investigated as a function of the overall deformation of the steel and the temperature. The influence of these factors on the slip rate of the austenite and ferrite phases along the grain boundaries is also considered. The hot-microhardness ratio of the austenite and δ ferrite in 08X21H5T steel is investigated as a function of the temperature.     

真空条件下钢液脱气过程的模拟研究

基于相似的动力学机理,利用水溶液中溶解氧的去除过程模拟了钢液的真空脱气行为. 在负压25 kPa条件下发现,容器壁面或测氧探头表面会析出大量细小气泡,这一现象与以往脱气数学模型假设的内部脱气反应非常类似;为了验证内部脱气位点的存在,通过引入机械搅拌,对溶池表面和内部脱气速率进行了分析计算. 实验结果表明,在整个脱气过程中溶池表面脱气速率很低,内部脱气位点析出的气泡会极大地提高溶解氧的去除速率,尤其当真空压力为25 kPa时,其脱气速率约为自由表面的脱气速率的10倍,但内部反应仅局限于脱气的初始阶段,即高溶解氧浓度范围内. 另外,水溶液中溶解氧的去除为一级反应过程,其体积传质系数（k · A · V?1）为常数,因此可以利用溶解氧在水溶液中的去除过程模拟钢液的真空脱气行为. 为了描述真空压力和吹氩流量对k · A · V?1的影响,引入搅拌动能密度（ε）的概念,通过线性回归得到了lg (k · A · V?1)与lg ε之间的函数关系,并与以往的模拟研究进行了对比.      

Influence of the pressure in the vacuum unit’s working chamber on the content of hydrogen and nonmetallic inclusions in steel

In electrosmelting shop 2 at Belarussian Metallurgical Plant, the removal of hydrogen from steel is studied as a function of the residual pressure in the working chamber of the RH vacuum unit. The influence of the pressure on the quantity and composition of the nonmetallic inclusions in cord steel is also investigated.     

Numerical Simulation of Dehydrogenation of Liquid Steel in the Vacuum Tank Degasser

Vacuum tank degassers are often utilized to remove hydrogen from liquid steel. A new comprehensive numerical model, which has been developed to simulate hydrogen removal in the vacuum degassers, is presented in this paper. The degassing model consists of two sub-models, which calculate the gas-steel flow field and the species transport of hydrogen. An extended k–ε turbulence model is adopted to consider the effect of gas injection on the turbulent properties and an interfacial area concentration model is introduced to compute the interfacial area density between liquid steel and the bubbles. The fluid dynamic sub-model is validated with a physical gas stirred tank, which is believed to have similar flow phenomena as the studied vacuum degasser based on the modified Froude number. Two fundamental expressions for mass transfer coefficient, which have been paid little attention by the researchers concentrating on vacuum degassing, are evaluated with a simulation case corresponding to practical operation. The effect of vacuum pressure on the dehydrogenation process is investigated and, moreover, the integrated model is verified with industrial measurements. The predicted final hydrogen contents in liquid steel show good agreement with the measured ones. The model and the main results are presented.     

Role of Direct Reduced Iron Fines in Nitrogen Removal from Electric Arc Furnace Steel

Electric arc furnace steel contains about 70‐120 ppm nitrogen. There is no suitable method for nitrogen removal from electric arc furnace steel up to the level desired for good quality bars and flat rolled products (30 ppm max). The existing process based on vacuum degassing can remove only up to 20% of nitrogen in steel. In the present study DRI fines have been injected into a steel bath which can drift out nitrogen in steel through production of fine CO bubbles in‐situ on reaction with residual FeO in DRI fines and C in bath. For high and medium carbon steel, nitrogen got reduced to 30 ppm and 60 ppm respectively where initial nitrogen was 150 – 200 ppm in steel. Nitrogen removal also depends upon bath depth and addition level of DRI.     

天津钢管公司100t RH的设备功能和冶金效果

国内自行设计制造的100 t RH真空循环脱气设备的真空度可达67 Pa以下,真空处理能力为500kg/h以上。生产实践表明,氩气流量越大,钢水循环速度越大,高真空脱气时间越长,钢水脱气效果越明显,所处理的管线钢的氢、氧、碳含量可分别降至1×10^-6、20×10^-6和20×10^-6以下。     

Behaviors of Denitrogenation in RH-MFB

 According to the analysis related to kinetic mechanism of vacuum denitrogenation and combining with the actual production of RH-MFB (a combination of Ruhstahl-Hausen vacuum degassing process with a multifunctional oxygen lance) at Liansteel, the limit step and model equation of vacuum denitrogenation are determined. Meanwhile, the influencing factors of nitrogen removal from liquid steel in vacuum of RH-MFB are analyzed. The results show that the limit step of vacuum denitrogenation in RH-MFB is the mass transfer of nitrogen in liquid boundary layer and the reaction follows first order kinetics. Keeping the necessary circulation time under the working pressure (67 Pa) is helpful to nitrogen removal from steel. The oxygen content in molten steel has little influence on the removal of nitrogen after deep deoxidation, while the sulphur content in liquid steel is always relatively low and has little effect on denitrogenation. The sharp decrease of carbon content in steel drives the process of denitrogenation reaction so as to exhibit a faster denitrogenation rate. The interfacial chemical reaction and argon blowing play a major role in the nitrogen removal when the carbon content in liquid steel is stable.     

Vacuum treatment of steel in a two-position unit in the oxygen-converter shop

Degassing and deep decarburization of steel in a two-position vacuum-treatment unit in the oxygen-converter shop at OAO Magnitogorskii Metallurgicheskii Kombinat is described. That unit went into operation in February 2010. To fulfill orders for pipe steel with specified hydrogen content (no more than 3 ppm in the final steel) and nitrogen content (no more than 0.006%), the minimum vacuum-degassing time is determined, the influence of additions of slag-forming materials and ferroalloys after vacuum degassing on the hydrogen content in the steel is assessed, and the potential of the new vacuum-treatment unit for deep decarburization of steel in natural and forced conditions is demonstrated.     

氩直流辉光等离子体钢液脱氮的研究

用25 kg真空感应炉对0.02%C钢液进行氩直流(DC)辉光等离子体条件的脱氮实验,研究了氩辉光等离子体对钢液脱氮动力学的影响。结果表明,氩辉光等离子体钢液脱氮速度和脱氮效果明显优于真空钢液脱氮,当钢液氧含量为180×10^-6,在氩辉光等离子体下钢液中氮含量可降至9×10^-6。氩辉光等离子体对钢液的脱氮效果体现在界面化学反应上,提供了加速脱氮反应的动力学条件。     

含锰钢RH真空过程锰的迁移行为

Ruhrstahl Heraeus（RH）精炼炉是重要的二次精炼装备,但在真空处理过程中会遇到钢液易挥发合金元素的损失量大的问题,且造成钢液真空喷溅的结瘤及对后续钢液的二次氧化。针对含锰钢RH真空处理过程锰的气化导致的元素损失及真空喷溅等问题,跟踪和研究了120 t RH不同真空处理模式下钢液中Mn元素的变化规律及迁移行为。分析了锰元素损失与其挥发和真空喷溅的关系,并在RH真空室内壁不同位置结瘤物的解剖实验中得到验证。研究表明,钢液中Mn元素在RH真空过程中存在着明显损失,真空前期损失量最大;RH真空室内壁结瘤物中锰氧化物的质量分数整体占比高达14%～70%;热力学计算结果显示:温度、钢中Mn的含量以及真空度对Mn的挥发行为均有着很大的影响,是真空过程锰迁移的关键影响因素。通过改进真空压降模式,采用步进式抽真空,元素锰的损失由原先的2×10?4降低至1×10?4,结果对现场生产具有很强的指导意义,通过改进真空压降模式可以有效的抑制钢液的喷溅和挥发,进而减少合金元素锰的损失。      

120t VD脱氢影响因素分析及工艺参数优化

为进一步改善VD脱氢效果,以VD脱氢热力学和动力学为基础,分析了吹氩流量、真空度、保持真空时间、炉渣碱度和初始氢含量对VD脱氢的影响。对120tVD的吹氩流量、真空度和保持真空时间等参数进行了优化。结果表明,VD的脱氢效果得到了显著改善,脱氢率基本都稳定在60％以上,平均脱氢率由优化前的56．2％提高到71．2％,最高脱氢率达90．6％。     

Current trends in the production of railroad wheels and the effect of out-of-furnace treatment of the steel on their properties

Current trends in the production of railroad wheels show the use of some promising techniques: a reduction in the carbon content of the finished steel; degassing the steel in a vacuum to decrease its hydrogen content; more efficient deoxidation and alloying of the steel. When used together, these measures are ensuring that the finished steel has the mechanical and service properties prescribed for wheel steel. Studies and factory testing of a new technology for making wheel steel have shown that the oxygen content of the steel can be reduced by its self-deoxidation during vacuum degassing. This approach also helps lower the steel’s hydrogen content while saving deoxidizers. Researchers have discovered certain laws that govern the relationship between the characteristics of wheel steel and its contents of sulfur and gases. The amount of sulfur and gases in this type of steel can be reduced by using efficient parameters for the treatment that is administered outside the steelmaking furnace. __________ Translated from Metallurg, No. 8, pp. 56–60, August, 2006.     

电弧炉冶炼超高强度凹螺纹钢筋钢工艺的探讨与研究

用电弧炉冶炼超高强度凹螺纹钢，钢中气体含量易偏高而造成氢脆和时效，从而影响钢的质量，通过冶炼工艺，采用钢包吹氩等措施，改善了钢的质量，满足了钢材的性能要求。     

Mathematical modelling of decarburisation and degassing during vacuum circulation refining process of molten steel: application of the model and results

The mathematical model for decarburisation and degassing in the vacuum circulation refining process of molten steel, proposed and presented earlier, has been applied to the refining process of molten steel in a multifunction RH degasser of 90 t capacity. The decarburisation and degassing processes in the degasser under the RH and RH‐KTB operating conditions have been modelled and analysed using this model. It was demonstrated that for the RH and RH‐KTB refining processes, the results predicted by the model are in good agreement with some plant data. The mean contributions of the three refining sites in six circulation cycles to decarburisation are 10.5 – 11.6, 37.4 – 38.0 and 50.5 – 52.1 % of the overall amount of decarburisation, respectively. The KTB operation can markedly accelerate the decarburisation of molten steel. Using the top blowing oxygen of 6 min with the flow rate of (600 ‐ 1000) m³(STP)/h, the initial carbon mass content of the liquid steel for the RH refining process may be increased to (550 ‐ 700) · 10‐⁴ from 400 · 10‐⁴ %. And the treatment time needed for reducing the carbon mass content in the steel to a level of ≤ 20 · 10‐⁴ % may be shortened over 3 ‐ 4 min. The effectiveness of decarburisation and degassing cannot be obviously improved by increasing the lifting argon blow rate to 900 from 600 I(STP)/min under the operating modes examined in the present work.     

钢包精炼轴承钢二十年

LFV精炼轴承钢功能包括加热、脱气、搅拌 ;轴承钢标准的不断提高、钢液的初炼工艺和精炼工艺的不断进步 ,使高碳铬轴承钢钢中w (O)从 2 5× 10 -6下降到 8.97× 10 -6,在国内处于领先水平