Microstructure evolution and thermal expansion of Cu-Zn alloy after high pressure heat treatment

The thermal expansion coefficients of Cu-Zn alloy before and after high pressure treatment were measured by thermal expansion instrument in the temperature range of 25？700 ℃,and the microstructure and phase transformation of the alloy were examined by optical microscope,X-ray diffractometer（XRD） and differential scanning calorimeter（DSC）.Based on the experimental results,the effects of high pressure treatment on the microstructure and thermal expansion of Cu-Zn alloy were investigated.The results show that the high pressure treatment can refine the grain and increase the thermal expansion coefficient of the Cu-Zn alloy,resulting in that the thermal expansion coefficient exhibits a high peak value on the α-T curve,and the peak value decreases with increasing the pressure.

INFLUENCE OF HEAT TREATMENT ON OXIDATION PROPERTIES OF C/C COMPOSITES FABRICATED BY HIGH PRESSURE IMPREGNATION CARBONIZATION

Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the inter-laminar distance of (002) plane (d002) deceased while the microcrystalline stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invari-able at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.

Effects of high-pressure heat treatment on the solid-state phase transformation and microstructures of Cu_(61.13)Zn_(33.94)Al_(4.93) alloys

The phase transformation activation energy of the Cu61.13Zn33.94A14.93 alloys, which were treated at 4 GPa and 700 ℃ for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94A14.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from （111） to （200） of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β＇→β and/β→β＇ transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5-20℃/min.

Effect of High Pressure Heat Treatment on Microstructure and Compressive Properties of Low Carbon Steel

The effect of high pressure heat treatment on microstructure and compressive properties of low carbon steel were investigated by optical microscope,transmission electron microscope,hardness tester and compression test methods.The results show that martensite appears in low carbon steel at 1-5GPa GPa and 950°C for 15 minutes treatment,high pressure heat treatment can improve the hardness and compressive properties of the steel,the yield strength of the steel increases with increasing pressure,and its compressive properties are better than that treated under normal pressure quenching.

Flexible Furnace Concepts for Vacuum Heat Treatment Combined with High-pressure Gas Quenching

IN the past five years the process combination of vacuum hardening, respectively vacuum carburizing with high-pressure gas quenching was successfully introduced to the market, especially in the manufacture of gears. In the meantime furnace concepts for various applications are available to the industry. In the following report three plant varieties are introduced, which differ in process flexibility and throughput. This report also explains criteria for the selection of a furnace in view of the existing application requirements. Besides this a short introduction is given into the vacuum carburizing process and the high-pressure gas quenching technology.

Formability and strengthening mechanism of AA6061 tubular components under solid granule medium internal high pressure forming

A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 ℃ and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 ℃ and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio（MER） of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.

Characterization of A390 aluminum alloy produced at different slow shot speeds using vacuum assisted high pressure die casting

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390alloy at different slow shot speeds were evaluated.Plate-shaped specimens of hypereutectic A390aluminum alloy were produced on a TOYO BD?350V5cold chamber die casting machine incorporated with a self-improved TOYO vacuum system.According to the results,the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling.Meanwhile,tensile properties of vacuum die castings were deteriorated by the porosity content.In addition,the average primary silicon size decreased from23to14μm when the slow shot speed increased from0.05to0.2m/s,which has a binary functional relationship with the slow shot speed.After heat treatment,microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al)matrix.Furthermore,the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.

Different aging behaviors at surface layer and central region of a die-casting A380 alloy during heat treatment

Microstructural and hardness evolutions of a vacuum-assistant die-cast A380(Al-8.67 wt.%Si-3.27 wt.%Cu) alloy during heat treatment were investigated. Isothermal DSC test at 200 °C revealed that the precipitation reaction in the surface layer was faster than that in the central region. This corresponded with the hardness evolution that the surface layer hardened faster. The hardness increment in the surface layer was higher than that in the central region. Further experimental evidences indicated that the differences were due to the different amounts of heterogeneous nucleation sites for precipitation in the two parts. The influence of the characteristic as-cast microstructure on the artificial aging process is analyzed and discussed in detail.

Heat Treatment of Centrifugally Cast High-Vanadium Alloy Steel for High-Pressure Grinding Roller

The roller is one of the main parts of a high-pressure grinding roller, which is a type of highly efficient ore crushing equipment. Its working life is strongly affected by the materials used. In this paper, a new kind of roller material, the high-vanadium alloy steel （HVAS）, was investigated. The results showed that the as-cast microstructures of the HVAS roller contained martensite, residual austenite, and alloy carbides. The HVAS sample quenched at 1,080 ℃ had a high hardness, and it had much higher compressive strength and abrasive wear resistance after tempering at 560 ℃ for 30 rain. The mechanical properties of the HVAS are more sufficient than the existing roller materials, which are feasible for larger machine design.

12Cr2Mo1VR在电站辅机产品中的应用及制造工艺优化

本文主要介绍采用12Cr2Mo1VR材料短筒身的高压加热器,在制造过程中出现裂纹问题,针对此材料进行研究并采取措施,包括优化工艺、改进设计结构等,从而规避风险,保证产品质量。

CCPP机组余热锅炉高压蒸发器泄漏分析与处理

燃气-蒸汽联合循环机组(CCPP)作为高效能源转换系统,在钢铁等工业领域得到广泛应用。余热锅炉作为CCPP机组的核心部件,其稳定运行直接关系到整个机组的效率和安全性。文章针对某钢厂燃气轮机组配套余热锅炉高压蒸发器上部迎烟气面频繁泄漏问题进行了深入研究,分析泄漏原因为其下联箱内沉积物导致蒸发器管内水流量减小,进而产生汽水混合物的冲击腐蚀,同时炉膛局部区域的“烟气走廊”现象加剧了这一腐蚀过程。针对这一问题,采取更换泄漏管段、改造下联箱定排管系统以提高排污效率、修复和完善烟气挡板以减少“烟气走廊”形成、优化定期排污操作以及制定定期的检查和维护计划等措施,有效地解决了高压蒸发器的泄漏问题,提高了设备的稳定性和安全性。

高压液氨预热器管板环焊缝主副加热局部热处理

管板环焊缝局部热处理是影响高压液氨预热器服役安全的关键制造技术,传统局部热处理时温度分布不均匀、管板约束大,导致残余应力难以消除。对此,采用主副加热局部热处理方法,并验证该方法在高压液氨预热器局部热处理时的有效性。计算与测试结果表明,传统局部热处理仅可降低外表面的轴向和环向残余应力,而内表面轴向应力会略微增大,环向应力降幅较小;主副加热局部热处理使内表面轴向应力由283 MPa降低至100 MPa以下,降幅约64%,环向应力由324 MPa降低至206 MPa,降幅约37%,显著降低了设备内表面应力腐蚀开裂的敏感性。

高压渗流法制备中高体积分数SiCp/Al复合材料的研究现状

高压渗流法制备SiCp/Al复合材料因其适应性广、操作简单、易于实现中高体积分数SiCp/Al复合材料的生产等特点而受到广大科研工作者的关注与广泛应用。本文详细阐述了中高体积分数SiCp/Al复合材料的高压渗流工艺,包括预制体的制备和高压渗流过程两方面,并对预制体制备过程中颗粒粒径、添加剂等因素以及高压渗流过程中压力、温度等工艺参数对复合材料性能的影响进行了分析;简述了SiCp/Al界面润湿性的改善策略及其对复合材料性能的影响,以及热处理对复合材料组织与性能的影响;最后介绍了中高体积分数SiCp/Al复合材料的应用,并展望了高压渗流法制备中高体积分数SiCp/Al复合材料的发展前景。

重油加氢螺纹锁紧环换热器应用及运维策略

高压换热器是重油加氢裂化装置的核心设备之一,以螺纹锁紧环高压换热器应用最广。直径在φ1 600 mm以上者即为大口径高压换热器,该类换热器在国内部分炼油装置中出现过内漏情况。发生原因主要为内件和壳体膨胀差不同导致的,需要通过升级垫片和做好检修控制保证高压螺纹锁紧环换热器不发生内漏。

高压液氢泵行业研究现状及关键技术问题

将氢气液化,以液态氢的方式进行储运、加注是降低用氢总成本的重要方式之一,并有望成为未来面对更大用氢需求的更优选择。高压液氢泵作为液氢产业链中的核心设备,其国产化水平对于降低成本和提高产业链自主可控至关重要。为此,系统调研了高压液氢泵在加氢站的应用现状及国内外研发情况,分析了高压液氢泵研究中亟需解决的关键技术问题,提出了液氢泵国产化的技术攻关方向及主要路径。研究结果表明:①液氢加氢站主要有低压汽化压缩、液氢泵增压汽化和直接加注等3种技术模式,其中液氢泵增压汽化是液氢存储型加氢站的主流技术模式;②中国有关高压液氢泵研发的公开研究成果较少,高压液氢泵的国产化研发仍处在初级阶段,产品的稳定性和成熟度还有待验证;③高压液氢泵国产化研发亟需解决结构型式选择与设计、低温绝热性能、材料选择、活塞密封与泄漏控制等关键技术问题,并针对性地提出了液氢泵国产化的建议。结论认为,高压液氢泵设计需要在技术与性能,生产与维护之间综合考量,以确保其在极端低温环境下稳定、可靠运行;随着氢能产业的快速发展,氢能的跨境运输将成为现实,届时液氢将成为重要储运方式,高压液氢泵将在国际液氢物流运输船舶接收、储罐转注、液氢槽车充装、液氢加注等环节发挥更大的作用。

蜡油加氢裂化装置高压换热器换热效率降低的研究及对策

中海石油宁波大榭石化有限公司蜡油加氢裂化装置高压换热器换热效率持续降低,特别是E101、E103、E104和E106换热效率下降十分明显。由于高压换热器换热效率降低,反应进料加热炉负荷增加,反应入口温度难以提高,造成装置处理量无法提高,影响全厂的物料平衡。通过调研、现场技术分析、各方面讨论等技术服务措施,分析高压换热器换热效率降低的原因及可采取的措施,以延长装置运行周期,保证蜡油加氢裂化装置安全稳定运行。

超临界氢用空温式气化器的传热特性研究

液氢具有高密度、可常压下保存的优点,比高压气氢更适合于储存和运输。在目前的液态储存气态加注型加氢站中,储存的液氢需要增压和气化,在空温式气化器中变成高压气态超临界氢后才可加注。对于空温式气化器的设计,目前仅有基础的传热学计算公式作为指导,缺乏对高压(45 MPa)超临界流体所用的特殊结构气化器传热特性的探究。采用数值模拟方法,利用Fluent软件对包括内外流场和管壁固体域在内的整体耦合传热模型进行计算。以得到的总体传热系数为参考,对气化器的特殊结构、空气域的温度和流动状态、超临界氢流域的入口温度和流量进行探究。探究结果有助于相似气化器的设计计算,也为气化器在实际运行时的总体布置提供参考。

高压加氢换热器Ω环制造过程难点及质量控制

高压加氢换热器Ω环制造难度大,其制造质量对整体设备的运行安全有着举足轻重的影响。本文描述了高压加氢换热器现场检修中存在的问题,分析了其泄漏的原因,说明了高压加氢换热器Ω环的技术数据,重点阐述了制造新的Ω环的质量控制方法,以及加工中的问题改进,总结探讨了Ω环加工制造中的难题,为保证Ω环符合图纸技术要求、提升高压加氢换热器质量提供了一定的借鉴和参考。