40000m~3/h空分设备主换热器的设计及制造

通过对进口 4 0 0 0 0m3 /h空分设备主换热器进行结构分析及对比模拟计算 ,用国产传热翅片进行设计、采用真空钎焊工艺制造的主换热器 ,经并网运行 ,设计指标优于原空分设备 ,为今后成套大型空分设备板翅式换热器国产化设计、制造创造了条件。     

Investigation of electrode and hydrogen induced crack in welded joint of dissimilar steel

The welded joint of dissimilar heat-resisting steels 20Crl2MoV(F12)and 12 Cr2MoWVTiB(102)generally works around 600°C.In this paperthree kinds of ferritic electrodes are used for testing.They are R817 high-strength electrode(CrllMoVNi),R347 low-strength electrode(Cr2MoVWB)and newly-developed R507MoNb medium-strength electrode.The study on theinfluence of those three different electrodes on carbon migration,HIC and hy-drogen diffusion shows that medium-strength electrodes can well control thecarbon migration,and that the tendency to HIC in the joint formed by R817 issmaller than that by R347 instead.Considering the effect of weld metal transfor-mation on the restraint stress and hydrogen concentration of a joint,the hydro-gen distribution in the heat-affected zone(HAZ)is calculated by using finite ele-ment method(FEM)with stress and strain changing,and so the effect of thetransformation behaviour on HIC is revealed.In addition,newly-developedR507MoNb electrodes,tested the elevated-temperature property,oxidation re-sistance and creep rupture strength,have fulfilled the technical standards con-cerned and passed the examination of on-the-spot operation.     

Material flow and microstructure in the friction stir butt welds of the same and dissimilar aluminum alloys

The material flow and microstructural evolution in the friction stir welds of a 6061-Al alloy to itself and of a 6061-Al alloy to 2024-Al alloy plates of 12.7 mm in thickness were studied under different welding conditions. The results showed that plastic deformation, flow, and mechanical mixing of the material exhibit distinct asymmetry characteristics at both sides of the same and dissimilar welds. The microstructure in dissimilar 6061-Al/2024-Al welds is significantly different from that in the welds of a 6061-Al alloy to itself. Vortex-like structures featured by the concentric flow lines for a weld of 6061-Al alloy to itself, and alternative lamellae with different alloy constituents for a weld of 6061-Al to 2024-Al alloy, are attributed to the stirring action of the threaded tool, in situ extrusion, and traverse motion along the welding direction. The mutual mixing in the dissimilar metal welds is intimate and far from complete. However, the bonding between the two Al-alloys is clearly complete. Three different regions in the nugget zone of dissimilar 6061-Al/2024-Al welds are classified by the mechanically mixed region (MMR) characterized by the relatively dispersed particles of different alloy constituents, the stirring-induced plastic flow region (SPFR) consisting of alternative vortex-like lamellae of the two Al-alloys, and the unmixed region (UMR) consisting of fine equiaxed grains of the 6061-Al alloy. Within all of these three regions, the material is able to withstand a very high degree of plastic deformation due to the presence of dynamic recovery or recrystallization of the microstructure. The degree of material mixing, the thickness of the deformed Al-alloy lamellae, and the material flow patterns depend on the related positions in the nugget zone and the processing parameters. Distinct fluctuations of hardness are found to correspond to the microstructural changes throughout the nugget zone of dissimilar welds.     

高温钎料PdCu-Ti在氧化铝陶瓷上的润湿性及界面反应

本文采用座滴法试验研究了合金系统ＰｄＣｕ－Ｔｉ在Ａｌ２Ｏ３上润湿性的变化规律，探讨了界面冶金及结合等行为，运用热力学理论对结果进行了分析，随Ｔｉ含量的增加及Ｐｄ含量的减少润湿角逐渐降低，Ｔｉ的加入使界面发生了一个双重变化；液相侧富氧，钛吸收层的生成及随后的固相侧氧化钛的生成，只有界面上生成一氧化钛，才能有较好的润湿行为和较强的结合力。     

热处理工艺对截齿钎焊接头强度的影响

为获得采煤机用截齿钎焊接头的优良性能，作者研究了钎焊后热处理工艺参数对钎缝抗剪强度的影响。试验表明，高温区停留时间在保证钎焊时钎料充分熔化的前提下越短越好；冷却速度对接头的强度有较大影响，一般情况下，钎焊后由880℃冷却到200℃的时间应控制在5～20min之间；回火温度在350～450℃之间抗剪强度有低谷区。截齿钎焊采用HL105钎料，配以合适的钎剂能获得较理想的接头性能。     

陶瓷/金属钎焊与扩散连接的研究现状

工程陶瓷由于具有优异的综合性能,在许多领域得到广泛应用,但其加工性能差,通常需要与金属组成复合结构.实现陶瓷与金属之间的可靠连接是推进陶瓷材料应用的关键,钎焊和扩散连接被认为是陶瓷/金属连接中较为适合的方法.文中对近年来国内外陶瓷/金属钎焊和扩散连接技术领域的研究现状进行了综述,认为活性金属钎焊和部分瞬间液相连接发展比较成熟,部分瞬间液相连接充分结合了活性钎焊和固相扩散连接两者的优点,将成为未来陶瓷/金属连接的发展方向.     

高频焊管用464-H14铝复合带材力学性能的研究

结合工业生产研究了高频焊管用464－H14铝合金复合带材的退火工艺和加工工艺对材料力学性能的影响。结果表明：成品材料冷轧前的软化退火温度应选择在既能使材料完全软化而又不发生Si原子扩散的350－400℃之间，冷加工率应控制在20％－40％，这样可使材料获得较好的力学性能，能够满足产品的技术标准和使用要求。     

钛及钛合金电弧钎焊及接头强度

用Ti—Cu—Ni，Ti-Cr-Zr钎料在TIG电弧加热条件对TA2和Ti—6Al—4V钛合金进行钎焊。结果表明：用Ti—Cu—Ni钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是418．3MPa和439．6MPa；用Ti—Cr—Zr钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是575．2MPa和656．1MPa。对Ti-Cu-Ni钎料／母材界面分析认为固液异分化合物η相((Cu，Ni)Ti2)生成时呈笋状生长，嵌入钎缝对钎缝的强度提高有利。对Ti-Cr-Zr钎料／母材界面分析，认为主要是固溶体β-Ti(Cr)存在提高了钎缝强度。     

Low-melting-point titanium-base brazing alloys—part 2: Characteristics of brazing Ti-21Ni-14Cu on Ti-6Al-4v substrate

Filler metal of a low-melting-point (917 °C) Ti-21Ni-14Cu was brazed onto the substrate of Ti-6Al-4V alloy at 960 °C for 2,4, and 8 h to investigate the microstructural evolution and electrochemical characteristics of the brazed metal as a function of the period of brazing time. Optical microscopy, scanning and transmission electron microscopy, and x-ray diffractometry were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that diffusion of copper and nickel from the filler metal into the equiaxed a plus intergranular β structure of Ti-6Al-4V substrate causes the lamellar Widmanstätten structure to form. The intermetallic Ti₂Ni phase existing in the prior filler metal diminishes, while the Ti₂Cu phase can be identified for the metal brazed at 960 °C for 2 h, but the latter phase decreases with time. Advantage might be taken from the evidence of faster diffusion of nickel than copper along the β phase to the substrate. In deaerated Hank’s solution, corrosion potential, corrosion current density, and critical potential for active-to-passive transition decrease while the passivation range broadens with the period of brazing time. However, all the brazed metals, immersed for different periods in oxygen-saturated Hank’s solution, show similar corrosion behavior, irrespective of the brazing time.     

Al/Cu管异种材料火焰钎焊连接

采用火焰钎焊技术，实现了Al/Cu管异种材料的中温钎焊连接。所采用的改进型的CsF-AlF3钎剂Si粉含量在1％时，钎焊接头的抗裂性能最好。本试验所采用的钎剂具有熔点低、免清洗、无腐蚀、钎剂活性佳和接头抗裂性能好等优点，该技术达到了国内领先水平。