蓄热式燃烧技术在加热炉上的应用

为进一步挖掘节能潜力 ,降低燃耗 ,提高加热炉能力 ,承钢连轧厂加热炉进行了大规模改造。介绍了承钢加热炉蓄热式改造方案及其应用效果 ,改造后加热炉能力由 80t/h提高至 1 2 0t/h,单耗由 2 0 5m3 /t降至 1 3 5m3 /t。     

蓄热式加热炉技术的再优化

在蓄热式燃烧技术推广过程中,它总是被质疑为“炉膛压力不易控制,设备故障率高,节能不节钱”.结合一座棒材推钢式蓄热式加热炉和一座带钢步进梁蓄热式加热炉再优化改造,阐释了目前蓄热式加热炉普遍存在问题的原因和解决方案,还原了它的真实指标和运行状况.结果能为蓄热式燃烧技术的推广提供有益的参考.     

蓄热式燃烧技术在石特加热炉的应用与改进

介绍了石特棒材线双蓄热步进梁式加热炉的工艺条件、技术参数、蓄热式烧嘴和换向阀的特点,并针对该加热炉存在的蓄热能力不足、蓄热体寿命短、加热质量下降、换向阀故障率高而寿命短、煤气消耗上升等问题,通过增大蓄热体换热面积、将原有烧嘴的扁缝式喷口砖改为多孔射流板、将原旋瓣式三通阀改为直通双关式三通阀、改进加热炉燃烧自动控制系统,使加热能力由改造前的110t/h提高至150t/h,蓄热体寿命由8个月提高到15个月,换向阀的换向周期由60s延长到100s以上,使用寿命由1年延长到3年以上,且改善了加热质量,提高了加热炉的安全性。     

煤气反吹技术在蓄热式加热炉上的应用

本文从煤气反吹技术在蓄热式加热炉上的应用情况出发,阐述了轧钢加热炉蓄热式高温燃烧系统在生产中出现的问题,详细分析了普通蓄热式技术及其不足,介绍了煤气反吹技术的工作原理、特点、应用效果,山钢集团淄博张钢有限公司对其1座140t/h蓄热式高线加热炉进行的热平衡测试表明,炉子单位能耗为0. 907 GJ/t坯。     

酒钢炼轧厂板坯加热炉蓄热式节能改造

畜热式燃烧技术是冶金行业钢坯加热炉未来发展方向,炼轧厂板坯加热炉蓄热式节能改造是酒钢集团公司2008—2009年度重点节能环保项目,也是甘肃省循环经济发展战略的实际运用。通过对酒钢炼轧厂板坯加热炉蓄热式节能改造的研究,为今后新上项目的规划提供宝贵经验。     

熔模铸造型壳焙烧炉节能技术新进展

介绍了轻质耐火保温纤维、高温红外辐射涂料和蓄热式高温空气燃烧技术等工业加热保温节能新材料新技术的发展及其在国内熔模铸造型壳焙烧炉中的应用实例和节能效果。指出黑体炉衬材料与蓄热式高温空气燃烧技术相结合的加热炉是熔模铸造型壳焙烧炉的重点发展方向。     

影响蓄热式加热炉使用效果的原因分析

对蓄热式加热炉在使用过程中遇到的加热能力不足、蓄热室易积水等问题进行了分析，指出在蓄热式燃烧技术应用过程中，也应遵循传统的加热炉设计理论，并应对煤气进行更严格的脱水处理。     

蓄热式燃烧技术在大型低热值煤气环形加热炉改造中的应用

湖北新冶钢集团公司Φ170mm轧管机组中径21m的环形加热炉由于燃烧系统配置不合理．一直未能达到设计加热能力,仅为35t／h且能耗高,严重制约了机组生产能力的发挥。采用蓄热式燃烧技术对炉子燃烧系统进行改造后,该加热炉的加热能力明显提高,实测达到55t／h,最大达到60t／h;加热温度均匀,节能效果明显,管坯加热过程中无待温时间,满足了扩大生产能力的要求。     

实现节能15%以上的加热炉系统

最近，日本大同特殊钢公司开发的节能１５％以上的蓄热式系统将设置在川崎厂的连续式钢坯加热炉上，这在日本尚属首次。这种蓄热式系统是用与蓄热体构成一体的２个燃烧器交替地进行燃烧和排气，燃烧用空气可预热到接近炉内温度，因此是一种燃烧效率高、可达到大幅度节能的装置。它具有以下特点：①燃烧效率可达７５％以上，而传统的热交换器式加热炉为６０％左右，即可节能１５％以上。②因不需设置热交换器，因此炉子的配管和管道简单，结构紧凑。③因复数个燃烧器切换而交替燃烧，因此炉内温度分布均匀。④在钢坯热装率高的情况下，废气温…     

日本福山厚板厂分批式加热炉采用新蓄热式烧嘴

最近日本NKK公司在福山厚板厂1号分批式加热炉上全面采用新蓄热式烧嘴系统,该炉已于1998年5月正式投产。新蓄热式烧嘴（商品名称HRS烧嘴）是NKK公司和日本工业炉公司共同研究开发成的,是一种将蜂窝状的蓄热体和烧嘴构成一体而进行安装的紧凑式高速切换型高效烧嘴系统。这种烧嘴于1996年12月首先在福山第一热轧带钢厂3号连续加热炉上采用,接着用于京滨厂的加热炉,福山厚板厂是第3家。这次在更新的新型厚板分批式加热炉上采用这种烧嘴,其目的是使燃烧后的高温废气热量被陶瓷蜂窝蓄热体吸收,利用其热量将燃烧用空气预热到高温,以提…     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.