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某换热器在长期使用后出现渗水和腐蚀现象,对其渗漏部位进行宏观检查、扫描电镜及能谱分析.结果表明:部分区域的铜焊料与不锈钢基体在焊接时未完全熔合;在换热器使用期间,多次热循环与水流周期性冲击使焊接未熔合区域的铜焊料与不锈钢基体分离,最终导致局部渗水. 相似文献
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本文综述了铜及铜合金与钢连接技术的国内外研究发展动态。简述了铜钢固相连接和熔化焊接领域国内外研究者已取得的部分研究成果,指出熔钎焊接工艺的发展推动了铜钢熔化焊接的应用。在工程中,须根据实际铜钢结构型式和使用条件来选择合适的焊接方法。 相似文献
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对6 mm厚的6082-T6铝合金进行两种表面处理然后实施搅拌摩擦焊接,研究了对接面氧化膜对接头组织和疲劳性能的影响。结果表明,进行速度为1000 mm/min的高速焊接时,对接面未打磨和打磨的接头焊接质量都良好,接头强度系数达到81%;两种接头的疲劳性能基本相同,疲劳强度均为100 MPa;少数样品在焊核区外断裂,大部分样品在热影响区断裂。与接头相比,两种接头焊核区的疲劳性能有所提高,均为110 MPa,在疲劳测试中裂纹并未沿“S”线萌生和扩展。 相似文献
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钢轨横截面出现斑痕的原因分析 总被引:1,自引:1,他引:0
焊接前的钢轨横截面在打磨过程中出现斑痕。经手提式硬度计检测,钢轨横截面硬度异常,疑是局部偏析或夹杂物等缺陷所致。通过取样检验,钢轨横截面试样正反两面的低倍组织,一面有斑痕,另一面无斑痕;经硬度测定和金相检验,认为钢轨横截面出现的斑痕是因打磨量控制不当,造成钢轨打磨面局部表层温度急剧升高,因钢轨母材仍处于常温状态,使打磨面表层快速冷却产生了马氏体组织转变,致使该面出现斑痕。 相似文献
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陈泉 《中国新技术新产品》2013,(23):73-73
文章主要从铁路线路施工中铜轨打磨的意义以及钢轨打磨的分类出发,对铁路线路的施工中钢轨打磨的技术进行分析和探究,以提高钢轨的使用寿命和列车的行车安全。 相似文献
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唐利 《理化检验(物理分册)》2010,(11):739-742
用φ4.0 mm 70号钢丝通过电阻对焊成环形的某批汽车零件,在焊接打磨后部分零件的焊缝区出现裂纹。通过化学成分分析、硬度测试和断口分析等方法对裂纹产生原因进行了分析。结果表明:裂纹是由于焊接时电极夹持力不足,没有充分将杂质挤出,使焊接后零件内部残留有氧化物引起的。经调整电极夹持力、改变切刀刃口形状及调整回火温度等工艺参数后,杜绝了裂纹的产生,零件各项焊接性能指标均达到了图纸要求。 相似文献
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铜和铝作为钛—钢爆炸焊接夹层时的复合工艺及焊接界面的实验研究 总被引:1,自引:0,他引:1
文章介绍了铜、铝作为钛-钢爆炸焊接夹层时的复合工艺,并对实验中的各种界面进行了超声探伤、扫描电镜及能谱分析,认为与铝相比铜更适合于作钛-钢爆炸焊接的中间夹层。 相似文献
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目的 研究GH600高温合金重熔层组织对T形激光焊接强度的影响。方法 采用激光焊工艺制备GH600高温合金T形焊接接头,采用金相显微镜、扫描电子显微镜和能谱仪观察重熔层去除前后焊接接头的显微组织和元素分布。采用电子万能试验机测试去除重熔层前后焊接接头的力学性能,采用维氏硬度计测试焊接接头的硬度。结果 去除重熔层的焊接接头的抗拉强度约为1400MPa,约为未去除重熔层焊接接头抗拉强度的3倍。结论 焊接强度下降的主要原因如下:重熔层内部存在较大的内应力和缺陷;二次结晶时内应力释放;第二相对晶界的钉扎失效使晶粒异常长大,进而形成白带层。 相似文献
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The effect of the removal of work hardened surface layers from specimens of 2024-T4 aluminum alloy and AISI-4130 steel on their fatigue lives has been investigated. Specimens were fatigued at selected stress levels for a given number of cycles and the surface layer was removed followed by subsequent fatigue cycling. Results confirm that when a material is subjected to fatigue loading, damage accumulates in the surface layers in the form of work hardening. Removal of the surface layer brings the specimen back to its pre-fatigued condition. 相似文献
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Richard G. Dobeson Stuart D. McDonald Matthew S. Dargusch 《Advanced Engineering Materials》2012,14(7):473-476
This paper reports on the development of a practical tool for determining minimum machining depths required after heat treatment of ASTM Grade 2 titanium alloys. Mechanical properties are adversely affected by the brittle alpha‐case that develops when titanium and its alloys are exposed to oxygen at elevated temperatures. This layer is normally removed by machining prior to putting the component into service. The exact depth of material that is required to be removed is dependent on the combined time and temperature of any prior heat treatment. This paper presents a study of oxygen diffusion in ASTM Grade 2 titanium alloy that was performed to quantify the rate of alpha‐case formation. A generalized method of predicting the depth of alpha‐case is discussed and a nomogram has been developed and presented as a tool for determining the minimum amount of material that needs to be removed. 相似文献
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B. S. Fokin M. Ya. Belenkiy V. I. Almjashev V. B. Khabensky O. V. Almjasheva V. V. Gusarov 《Technical Physics Letters》2009,35(5):440-442
The effect of nanoparticles in an aqueous dispersion (nanofluid) on the critical heat flux (CHF) removed by boiling liquid
from a heat-exchange surface has been studied. It is shown that a nanoparticles layer formed on the heated surface in the
course of boiling possesses a hierarchical structure. Hydrophilic properties of this layer and its high permeability facilitating
the supply of liquid to vapor bubbles lead to an increase in the CHF density. 相似文献
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《Materials Science & Technology》2013,29(9-10):1039-1044
AbstractAn ultrasonically aided laser drilling technique has been developed to raise the performance of traditional laser drilling on metal matrix composite materials. In the process, the workpiece is rigidly attached on top of a transducer which vibrates at a frequency of 20 kHz. Ultrasonic vibration has significantly increased liquid expulsion in laser drilling. For blind hole drilling of an aluminium alloy 2124/SiC composite, the thickness of the recast layer was reduced greatly by about 30–80% at different segments of the hole. In the recast layer the size and the amount of carbides were reduced when vibration was employed. Moreover, the depth of drill can be increased by as much as 20% when vibration was used. In through hole drilling of some 0'6-1'2 mm thick materials the recast layer was virtually removed and a reduced heat affected zone was obtained with no apparent depositionfound at either end of the hole. Also the diameter of the through hole became more uniform. 相似文献
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The sub-surface and surface damage produced by alumina and diamond grinding wheels has been studied as a function of material removal rate. Sub-surface damage is characterised in all cases by a discrete, dense layer of dislocations adjacent to the machined surface. The depth of the layer increases with material removal rate.The nature of the surface damage depends on the mechanism of material removal. As long as the cutting points are unloaded and the residue can escape the material is removed in a brittle manner. This is always the case for the diamond wheel and occurs for low rates of material removal with the alumina wheel. When the cutting surface is loaded with residue, the tool-workpiece interface temperature becomes so high that the material is removed by plastic flow. The finished surface is burnished. Unfortunately as the burnished surface cools down thermal quenching produces a network of surface cracks. 相似文献
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I MASSON J. P FEIEREISEN J. P MICHEL A MOCELLIN P BLUMENFELD 《Journal of Materials Science》1997,32(8):2215-2218
The effect of immersion in molten steel on subsequent creep behaviour has been investigated in two AlN ceramics. Steady-state
creep was not significantly affected but an enhanced initial creep rate was observed, especially when the surface layer had
not been removed after immersion. In immersed samples, SEM revealed some open porosity and microcracks near the surface and
particles containing steel constituents were found by TEM deep inside samples, in grain-boundary secondary phases.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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Zhongliang Liu Hongyan Wang Xinhua Zhang Sheng Meng Chongfang Ma 《International Journal of Refrigeration》2006,29(2):237-242
In this part of study, the comparative observations of the structure and the surface temperature of the frost layer of both the coated and uncoated surfaces ware carried out and a preliminary analysis was presented. A series of the repeated cycling tests were completed that lasted for more than 2 months, and the influences of the coating thickness were also investigated. The results show that the frost layer deposited on the coating surface has a very fragile structure and can be removed easily by external force. The coating thickness has an important effect on the anti-frosting performance of the paint. The results also show that the coating of the paint on the copper surface is durable and presents a very good repeated cycling performance. 相似文献
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In the present work, oil-field wastewater purification through superconducting magnetic separation technique using a novel magnetic nanoparticle was investigated. The magnetic nanoparticle, which has a multi-shell structure with ferroferric oxide as core, dense nonporous silica as inter layer and mesoporous silica as outer layer, was synthesized by co-precipitation method. To functionalize the magnetic nanoparticle, plasma polymerization technique was adopted and poly methyl acrylate (PMA) was formed on the surface of the nanoparticle. The multi-shell structure of the nanoparticle was confirmed by transmission electron microscope (TEM) and the characteristic is measurable by FTIR. It is found that most of the pollutants (85% by turbidity or 84% by COD value) in the oil-field wastewater are removed through the superconducting magnetic separation technique using this novel magnetic nanoparticle. 相似文献
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使用稀盐酸处理纳米镍粉表面的Ni2O3,然后用十二烷基苯磺酸钠(SDBS)对纳米镍粉表面进行改性,采用活性试验、红外光谱、热分析等手段对改性后的粉体进行了表征,并通过矢量网络分析仪,利用同轴波导的方法对粒子进行了电磁参数的测定.将试验所得到的电磁参数数据通过计算机模拟转化成材料对电磁波功率损耗值.结果表明,稀盐酸可以去除纳米镍粉表面氧化层;用4%十二烷基苯磺酸钠(SDBS)改性纳米镍粉能够显著提高纳米镍粉在有机介质中的分散性,提高了电磁波吸收性能. 相似文献