碳复合耐火材料对熔钢增碳作用的研究进展

叙述了MgO-C、Al2O3-C和ZrO2-C材料对熔钢增碳方面的研究进展;描述了MgO-C、Al2O3-C材料的增碳机理;指出了今后含碳耐火材料对熔钢增碳影响方面的研究重点。

熔钢真空脱气设备化学清洗技术

一、前言宝山钢铁总厂炼钢厂熔钢真空脱气设备是引进的大型装置(见图1)。共有脱气槽二台(包括上盖三只,下部槽三只),列管式气体冷却器二台,整流器一台;电极加热器二组,伸缩连接装置三组。该装置价格昂贵,仅上盖每只制造费就需25万元。

电磁场下熔渣和熔钢对镁铝尖晶石质耐火材料的侵蚀和渗透行为

为了研究电磁场作用下熔钢和熔渣对镁铝尖晶石质耐火材料的侵蚀和渗透行为,采用MgO和Al_2O_3含量(w)分别为84.40%和12.77%的镁铝砖,配制碱度为4的碱性渣,选用GCr15Si Mo钢,利用具有电磁场、真空、惰性气氛等多因素的抗渣炉,在1 600℃下进行侵蚀试验,测量试验后试样的侵蚀和渗透深度,并利用SEM、EDS、XRD对试验后试样进行表征。结果表明:电磁场作用下,熔渣和熔钢在1 600℃侵蚀1 h后,对镁铝尖晶石质耐火材料的侵蚀和渗透并不明显。因此,可以选择镁铝尖晶石质耐火材料来抵抗电磁场下熔渣和熔钢的侵蚀。

熔钢与Na_2O-Li_2O-SiO_2-B_2O_3熔渣间的界面作用研究

通过测定18031873K温度范围内3种熔钢与Na2O Li2O SiO2 B2O3熔渣间的界面张力值,研究了其间的相互作用。结果表明,在此温度范围内,随着熔钢中氧、硫含量的增加,界面张力值大幅降低,渣金间的相互作用加强,界面张力值随着渣中SiO2含量的增加而减小,随着Na2O和Li2O含量的增加而增加。

计算机单目视觉检测连铸结晶器熔钢液面高度

研究了把计算机单目视觉系统应用于连铸结晶器熔钢液面高度检测的可行性，为此配置了系统硬件，开发出相应的应用软件，进行了冷态模拟实验．结果证明此方法是可行的．在此基础上提出了一种响应时间短、测量精度高的连铸结晶器熔钢液位测量方法．

电渣重熔钢冷轧辊锻造过程的研究

本文研究的是用电渣重熔钢6X6MlΦ钢锭锻造冷轧辊的工艺参数。这种钢是为制造二十辊轧机的直径为130～152mm、长度为700～1700mm的冷轧工作辊而研制的,用以代替以前使用的9X钢和9X2MΦ钢。新钢种同9X钢和9X2MΦ钢相比,具有淬透性更好、耐热性更高的特点。这是因为,这种钢在回火过程中由于析出特殊碳化物而具有弥散硬化的能力。

难卷入熔钢的非牛顿结晶器保护渣的开发

防止结晶器保护渣卷入熔钢是提高铸坯质量的重要手段。至今采用的方法有以下三种：1）利用电磁力控制结晶器内钢水的流动；2）浸入水口的最佳化；3）保护渣的高黏度化。高黏度保护渣确实可以防止卷入钢水，但因结晶器与铸坯的润滑不够充分，而降低铸速，影响生产率。因此决定研究开发一种既能减少保护渣的卷入，又能实现高速浇注的含氮保护渣。

Microstructure and high temperature tribological behavior of laser cladding Ni60A alloys coatings on 45 steel substrate

The crack-free Ni60 A coating was fabricated on 45 steel substrate by laser cladding and the microstructure including solidification characteristics, phases constitution and phase distribution was systematically investigated. The high temperature friction and wear behavior of the cladding coating and substrate sliding against GCr15 ball under different loads was systematically evaluated. It was found that the coating has homogenous and fine microstructure consisting of γ（Ni） solid solution, a considerable amount of network Ni-Ni3 B eutectics, m^23C6 with the floret-shape structure and Cr B with the dark spot-shape structure uniformly distributing in interdendritic eutectics. The microhardness of the coating is about 2.6 times as much as that of the substrate. The coating produces higher friction values than the substrate under the same load condition, but the friction process on the coating keeps relatively stable. Wear rates of the coating are about 1/6.2 of that of the substrate under the higher load（300 g）. Wear mechanism of the substrate includes adhesion wear, abrasive wear, severe plastic deformation and oxidation wear, while that of the coating is merely a combination of mild abrasive wear and moderate oxidation wear.

Effects of reflowing temperature and time on alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution

Effects of reflowing temperature and time on the alloy layer of tinplate and its electrochemical behavior in 3.5%NaCl solution were investigated by electrochemical measurements and surface characterization.It is found that the amount of alloy layer increases with the increase of reflowing temperature and time.Then the corrosion potential of detinned tinplate shifts positively and the corrosion rate decreases.After being coupled with tin,the detinned tinplate acts as cathode and tin acts as anode initially.However,after being exposed for some time,the potential shifts of both detinned tinplate and tin reverse the polarity of the coupling system.The galvanic current density decreases with the increase of reflowing temperature and time.

不锈钢焊条熔滴过渡形态与气孔的关系

研究了不锈钢焊条熔滴过渡形态与气孔敏感性的关系.结果表明,细熔滴过渡时气孔倾向大,熔滴在电弧中吸收氢的总量是形成气孔的主要因素;促使熔滴细化的药皮组成物具有增大气孔倾向的作用;药皮中的水分对气孔的产生有重要影响;工艺因素对气孔的影响较为复杂.

热轧卷下表头部白条纹状翘皮缺陷调查及原因分析

文章通过对湛江钢铁热轧卷下表头部出现的白条纹状翘皮缺陷进行分析,发现连铸切下辊表面状态不良、辊面冷却水和辊子高速旋转异常是白条状翘皮产生的根源。通过加强辊面冷却水和辊子旋转的维护,下表白条纹状缺陷有明显改善。

真空自耗式钢材重熔工艺的微机控制

真空自耗炉是生产优质合金钢的设备。真空自耗式炼钢工艺的目的在于:第一进一步除去重熔钢材中所含的气体成份;第二使重熔钢材获得均匀的再结晶,从而提高钢材的质量。为实现这一工艺要求,必须在整个重熔过程中,对影响钢材质量的诸因素实施有效的监测和控制。在手工操作方式下,对工艺的控制主要是靠操作工人的经验,无法对整个熔炼过程进行全面和精确的控制,使钢材的质量和成材率受到很大影响。

Microstructures and mechanical properties of metal inert-gas arc welded Mg-steel dissimilar joints

The joining of Mg alloy to steel was realized by metal inert-gas arc welding, and the weld thermal cycle characteristics and Mg-steel joints were investigated. The results show that the temperature distribution in the joints is uneven. Mg alloy welds present a fine equiaxed grain structure. There exists a transition layer consisting mainly of AlFe, AlFe3 and Mg（Fe, Al）2O4 phases at Mg/steel interface, and it is the weakest link in Mg？steel joints. The welding heat input and weld Al content have the significant effect on the joint strength. The joint strength increases with increasing the heat input from 1680 J/cm to 2093 J/cm, due to promoting Mg/steel interface reaction. When weld Al content is increased to 6.20%, the joint strength reaches 192 MPa, 80% of Mg alloy base metal strength. It is favorable to select the suitable welding heat input and weld Al content for improving joint strength.

Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing

The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material nonlinearity,geometrical nonlinearity and work hardening on the welding process is studied,and the differences in the welding temperature field,residual stress and welding distortion by A-LWB and by single laser welding-brazing(SLWB)are analyzed.The results show that the thermal cycle,residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments,which verifies the effectiveness of FEM.Compared with the SLWB,A-LWB can make the high-temperature distribution zone of weld in width direction wider,decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress.And the welding deformation also decreases to some extent.

Microstructure and properties of laser cladding of 316L stainless steel on hydraulic support tube

In consideration of the special environmental conditions of coal equipment in mining, the seamless steel tube of hy-draulic prop made of 20^# carbon steel was taken as the substrate, and 316L stainless steel powder was used to clad the sub-strate by a fiber-coupled semiconductor laser. The microstructure of the cladding layer was determined by metalloscope. The hardness, wear resistance and corrosion resistance of the cladding layer were measured. The results show that metallurgy bind-ing interface between the cladding layer and the substrate is obtained without defects such as cracks and pores. The hardness of the cladding layer is much higher than that of the matrix, and the wear resistance and corrosion resistance are simultaneously better. According to the analysis, it is summarized that the improvement in performance of the cladding layer is closely related to the change of microstructure and the thermal effect in the cladding process. The maximum hardness occurs in the equiaxed zone, and with the grain coarsening, the hardness reduces simultaneously. In addition, the precipitated phase, hard particles and trace elements also have a great influence on the properties of the cladding layer, and they will prevent the surface from ab-rasion and reduce the plastic deformation of the matrix. It is verified that the 316L stainless steel is suitable for the 20^# steel in laser cladding repairing process. Since this study focused on coal machine equipment parts, it has certain practical significance for the repair of hydraulic equipment.

Microstructure and performance of laser cladding TiB_2 and Nickel-coated graphite composite coating on stainless steel 9Cr18

The antiwear and antifriction coating, which contains TiB2 and Nickel-coated graphite, has been obtained on stainless steel 9Cr18 by laser cladding. The processing method, microstructure, interface, microhardness, tribological properties and the forming mechanisms of the coating are analyzed. Results show that the microstructure of the clad coating are mainly long plume-like primary phase sosoloid Ni-Fe which form the matrix framework, while the in-situ anomalous synthetical TiC grains and uhrafine TiB2 grains uniformly disperse among the framework. The hardness and wear resistance of the coating has been greatly improved, which can be attributed to the reinforcement mechanism of TiC, TiB2, FeC, Fe3C and Cr23 C6. etc. At the same time, the coating has friction-reducing ability.

Porous ceramic coating formed on 316L by laser cladding combined plasma electrolytic oxidation for biomedical application

In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on titanium layer.The morphologies,microstructure and compositions of the coated samples were characterized by 3D surface profiler,SEM,EDS,XRD and XPS.The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid(SBF),respectively.The results showed that the porous ceramic coating mainly consisted of anatase and rutile,and highly crystalline HA was also detected.The main elements of the PEO coating are Ca,P,Ti and O.The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid.Furthermore,the composite coating could effectively improve the bioactivity of 316L stainless steel.

Preliminary Developments of Miniplate-Type Fuel of U-2.5Zr-7.5Nb Alloy Dispersed and Cladded in Zircaloy

Nuclear fuel based on uranium metal alloys is utilized in research and test reactors. For the purpose of the reduction of fuel enrichment, high densities of uranium-235 in this kind of fuel are needed. This can be achieved when uranium alloys are used containing elements such as Zr, Mo and Nb. The construction of fuel element with high-uranium density requires materials with low cross sections for neutron absorption, stability under irradiation and absence of the chemical interactions between the fuel and cladding elements. In case of U-Zr-Nb alloys, Zry （zircaloy） cladding is a better option due to the fact that they have a higher chemical compatibility when compared with the use of aluminum alloys. This study aims to develop plate type nuclear fuel using the U-2.5Zr-7.5Nb alloy dispersed in Zry. Powders of this uranium based alloy and Zry were obtained by hydriding-dehydriding process. These powders were homogenized, compacted in pellet that was sandwiched in plates and frame of Zry. This assembly was hot rolled forming the dispersion fuel miniplate.

Evolution of microstructure and mechanical properties in multi-layer 316L-TiC composite fabricated by selective laser melting additive manufacturing

In this study,the microstructure and mechanical properties of a multi-layered 316L-TiC composite material produced by selective laser melting(SLM)additive manufacturing process are investigated.Three different layers,consisting of 316L stainless steel,316L-5 wt%TiC and 316L-10 wt%TiC,were additively manufactured.The microstructure of these layers was characterized by optical microscopy(OM)and scanning electron microscopy(SEM).X-ray diffraction(XRD)was used for phase analysis,and the mechanical properties were evaluated by tensile and nanoindentation tests.The microstructural observations show epitaxial grain growth within the composite layers,with the elongated grains growing predominantly in the build direction.XRD analysis confirms the successful incorporation of the TiC particles into the 316L matrix,with no unwanted phases present.Nanoindentation results indicate a significant increase in the hardness and modulus of elasticity of the composite layers compared to pure 316L stainless steel,suggesting improved mechanical properties.Tensile tests show remarkable strength values for the 316L-TiC composite samples,which can be attributed to the embedded TiC particles.These results highlight the potential of SLM in the production of multi-layer metal-ceramic composites for applications that require high strength and ductility of metallic components in addition to the exceptional hardness of the ceramic particles.