Fin formation model during pre-roll ploughing of copper 3D outside fin tube

The mechanism of pre roll ploughing for 3D fins on the outside surface of copper tube was studied systematically, and especially the process and conditions of 3D fin formation were analyzed. The right mathematical model was also established. Based on the volume of fin ploughed out is equal to the volume of the metal extruded up by the extruding face of the tool, the relations between fin height, pre roll ploughing feed and pre roll ploughing depth have been achieved. With the increase of pre roll ploughing depth which must be equal to groove depth, the fin height gradually becomes larger. There are different critical feeds with the various depths of pre roll ploughing. The pre roll ploughing feed is the critical one, the height of fin is largest. And when the feed is above the critical one, the fin height will reduce with the increase of feed. The theoretical analysis basically accords with experimental results.

Macrostructure and properties of thin walled copper tubes prepared by the downward continuous unidirectional solidification method

The macrostructure and properties of the thin walled copper tube prepared by the downward continuous unidirectional solidification （DCUS） method were studied. The result shows that the macrostructure is closely related to the solid-liquid interface profile, which is influenced by the distance between the cooling water location and the solidification front. The mechanical properties of the thin walled copper tube prepared by the DCUS method are near those of the normal cast copper, and it has good relative density, electrical conductivity, and elongation, which are not greatly affected by casting speed. The thin walled copper tube prepared by the DCUS method also has good processing properties that can be taken to further drawing procedures directly without an intermediate process, and obtains good mechanical properties with the total processing rate of 89.8%.

Microstructure and properties of TP2 copper tube with La microalloying by horizontal continuous casting

The TP2 copper tube was prepared with La microalloying by horizontal continuous casting(HCC). The absorptivity of La and its effects on microstructure, tensile and corrosion properties of HCC TP2 copper tube were studied by means of the inductively coupled plasma optical emission spectrometer(ICP-OES), optical microscope(OM), scanning electron microscope(SEM) and potentiodynamic polarization measurements. The results show that the absorptivity of La in the HCC TP2 copper tube is about 15% under antivacuum conditions due to the good chemical activities of La. The impurity elements in copper tube such as O, S, Pb and Si can be significantly reduced, and the average columnar dendrite spacing of the copper tube can also be reduced from 2.21 mm to 0.93 mm by adding La. The ultimate tensile strength and the elongation with and without La addition are almost unchanged. However, the annual corrosion rate of the HCC TP2 copper tube is reduced from 10.18 mm·a^(-1) to 9.37 mm·a^(-1) by the purification effect of trace La.

AXIAL LOADS ACTING ON MANDREL IN COPPER RIFLED TUBE DRAWING PROCESS

Stresses and axial loads acting on the mandrel in the copper rifled tube drawing process were analysed,and factors affecting on the axial loads on mandrel were discussed.Results show that the depth of the mandrel dragged into sizing zone and lubrication have major influence on drawing loads and fin shapes.

A Study of Water Treatment Chemical Effects on Type I” Pitting Corrosion of Copper Tubes

It is known that one of the causes of pitting corrosion of copper tubes is residual carbon on the inner surface. It was confirmed that type I” pitting corrosion of the copper tube is suppressed by keeping the residual carbon amount at 2 mg/m2 or less, which is lower than that of the type I’ pitting corrosion, or by removing the fine particles that are the corrosion product of galvanized steel pipes. The developed water treatment chemical was evaluated using three types of copper tubes with residual carbon amounts of 0 mg/m2, 0.5 mg/m2, and 6.1 mg/m2. The evaluation was conducted for three months in an open-circulation cooling water system and compared with the current water treatment chemical. Under the current water treatment chemical conditions, only the copper tube with a residual carbon amount of 6.1 mg/m2 showed a significant increase in the natural corrosion potential after two weeks, and pitting corrosion occurred. No pitting corrosion and no increase in the natural corrosion potential were observed in any of the copper tubes that were treated with the developed water treatment chemical. In addition, the polarization curve was measured using the cooling water from this field test, and the anodic polarization of two cooling waters was compared. For copper tubes with a large amount of residual carbon, the current density near 0 mV vs. Ag/AgCl electrode (SSE) increased when the developed water treatment chemical was added.

Compound forming technology of outside 3D integral fin of copper tubes

Using rolling-ploughing-extrusion compound processing methods,a 3D integral-fin structure on outside surface of red copper tube with diameter of 16.0 mm and wall thickness of 1.5 mm was obtained. When both rolling depth and ploughing-extrusion(P-E) depth were 0.2 mm,rotating speed was 50 r/min,feed speed was 0.16 mm/r,3D fin structures with height of 0.25 mm were gotten. Two different fin structures were obtained in grooves formed with rolling-ploughing-extrusion compound forming technology and observed by scanning electron microscope(SEM). One is the compound structure with V-shaped groove and U-shaped groove,and the other is the single structure with V-shaped grooves. Two kinds of groove structures obtained by rolling processing and ploughing extrusion processing are restricted together by groove interval and rolling depth,and pitch and P-E depth,respectively. Based on the analysis of interaction of rolling and P-E processing,it is found from the result that the outside 3D integral-fin can be achieved by rolling-ploughing-extrusion compound processing when single V-shaped groove structures are formed by both rolling and P-E processing.

Localized Corrosion in Copper Tubes by Volatile Organic Substance

An unusual form of localized corrsion in copper tubes was detected early in service and in leakage tests after manufacturing.The morphology of this corrosion is similar to that of an ant's nest when viewed in cross section. The corrosion mechanisms, cases ofant's nest corrosion, and preventive measures are presented.

Evolution of Goss texture in thin-walled copper tube at different heat treatment temperatures

The evolution of microstructure,textures,and mechanical properties of thin-walled copper tube during heat treatment was investigated using EBSD technique and tensile test.The results show that the initial deformation textures of pre-drawn thin-walled copper tube are mainly composed of Copper and Y components,while with the increase of temperatures,the textures are transformed into a strong Goss texture gradually.The high-resolution microstructural characterizations indicate that the new Goss recrystallized grains nucleate and grow up within the deformed Copper grains and Y grains in different mechanisms,respectively.The tensile strength of the thin-walled copper tube decreases gradually with the increase of the temperature,while the elongation increases first and then decreases sharply due to the action of grain sizes and texture components.

Ammonia corrosion analysis of copper tubes and experimental research on non-copper improvement for heat exchanger in power plant

Ammonia corrosion in copper tube will affect the safety of boiler running in power plant. Therefore, no copper in heating system has become a technical orientation in heat exchanger reconstruction, This paper analyzes the condition and mechanism of ammonia corrosion occurring in copper tube used in coal-fired power plants. Using a general steam condensation testing equipment only for horizontal single tube, with water vapor and water as working fluid, on two types of steel tube with 2-side enhancement heat transfer, namely, a spirally fluted tube and a ratchet tube with internal spiral groove （RISG tube） which was developed recently, a set of experimental tests are conducted to investigate the characteristics of heat transfer and hydromeehanics. In order to compare easily, both one copper smooth tube and one steel smooth tube are also used in the experiment. The experimental results, which get from single horizontal tube, show that the overall heat transfer coefficient of steel spirally fluted tube are improved by 10%o to 17%, and that of the steel RISG tube（22%-28%） is better than steel spirally fluted tube, its flow resistance coefficient is only increased by 22% to 66% when compared with smooth tube. Based on a lot of experimental data, the steel spirally fluted tube and the steel RISG tube were applied in a low pressure preheater and an oil-cooler of some or other power plant respectively. The field testing results showed that their heat transfer coefficient with each types of enhancement heat transfer tubes were improved by 2.5% and 21%-45% comparing with copper smooth tube heat exchangers. Both basic and field experiment indicates that the steel tube with 2-side enhancement heat transfer is an ideal choice for heat exchanger reconstruction in no copper issue in power plants.

Simple Measurement of Carbon Films on Copper Tubes and Their Effects on Corrosion

It has been reported that pitting corrosion in copper tubes occurs due to the effect of a carbon film produced by the influence of undergoing an oil and heat treatment. As a quantitative method for determining the residual carbon amount, it has been reported that the inner surface of a copper tube can be dissolved with a mixed acid to collect and analyze the adhering carbon;however, this method is dangerous and difficult. Therefore, two methods were examined as a simple quantitative method for obtaining the residual carbon amount using copper tubes with known residual carbon amounts. One method utilizes X-ray photoelectron spectroscopy (XPS), and the other method utilizes the potential difference between the carbon film-adhered surface and carbon film-removed surface. In regard to XPS measurement, a linear correlation was found between the spectral intensity of C and the residual carbon amount;therefore, XPS measurements were considered to be effective as a simple measurement method for the carbon film on the inner surface of a copper tube. In the evaluation method by measuring the corrosion potential, a correlation was observed between the potential difference ΔE and the residual carbon amount of the inner surface of the tube and the outer surface of the polished tube. It is considered possible to estimate the residual carbon amount from the prepared calibration curve. Through these studies, it is suggested that the carbon film was non-uniformly present on the surface of the copper tube. Therefore, the galvanic current was measured, and the effect of a non-uniform carbon film on corrosion behavior was investigated. As a result, in the measurement of galvanic current, the current flowed from the copper tube with a large amount of residual carbon (cathode) to the copper tube with a small amount of residual carbon (anode). In addition, the higher the area ratio of the carbon film was, the larger the galvanic current tended to be.

爆炸焊接铜/钢复合管界面组织表征与性能研究

为了研究应用于压力容器的管道或承压部件的铜/钢双金属复合管材料中晶粒存在形式和力学性能之间的关系,通过爆炸焊技术获得了T2铜/316L不锈钢复合管,并对其界面形貌与微观组织进行分析。结果表明,T2铜/316L不锈钢复合管结合界面处呈现平直界面和周期性波状界面,波形结合区域的平均波长203μm、波高58μm。复合管结合界面两侧的元素发生互扩散,扩散层厚度为1μm。界面处Fe侧晶粒尺寸较小,随着结合界面距离的增加晶粒尺寸逐渐变大。通过纳米压痕试验发现,波峰处界面的纳米压痕结果达到了3.16 GPa,波谷处的纳米压痕结果达到了2.44 GPa,同时波峰处界面附近区域的纳米压痕结果均高于波谷处,Fe侧纳米压痕结果均高于Cu侧。纳米压痕试验获得的力学性能分布规律和微观组织的分布规律相一致。

工艺参数对三辊行星旋轧铜管尺寸定量影响研究

目的借助有限元模拟对管材三辊行星旋轧的尺寸进行定量研究与分析。方法采用三维扫描仪获得轧辊的宏观几何模型,采用Simufact.forming有限元软件,探究推进力、轧辊角度、自转速度及表面摩擦因数对TP2铜铸坯旋轧过程中变形和尺寸的影响。结果通过扫描发现,轧辊的倾斜角和偏转角分别为50°和29°;模拟结果显示,采用剪切摩擦更适合管材尺寸的准确模拟,剪切摩擦因数最佳值为1.2;增大喂料小车推力有利于轧件三角形区域的增大,最佳推力为13 kN;此外,轧辊转速对轧件尺寸有一定影响,增大轧辊转速有利于扩径,最佳转速为160 r/min。结论轧辊最低点位置和轧辊表面摩擦因数是影响轧件归圆后尺寸的2个关键因素,通过模拟研究可以准确获得管材的变形和几何参数。

换热器T2紫铜管在水线部位的腐蚀机理研究

目的基于对换热器中T2紫铜管因受残留水作用而出现泄漏降压现象的研究,分析换热器T2紫铜管在水线部位的腐蚀机理。方法通过T2紫铜管的润湿试验,对腐蚀样品进行宏观和微观形貌观察,对点蚀坑部位的腐蚀产物进行EDS和XPS等表征手段分析,探究腐蚀产物的成分和结构,从而推导出反应机理。结果铜管水线上部位和下部位都以均匀腐蚀为主,但是颜色有所差异。水线部位以点蚀为主,肉眼即可见排成直线的斑点状腐蚀坑,腐蚀产物的颜色主要为黑色和绿色。根据表征分析结果可知,腐蚀体系中含有HCO_(3)^(-)和SO_(4)^(2-)。腐蚀产物的组成有,内层Cu_(2)O,外层CuO,水线部位和水线以下部位铜管表面还有一层CuCO_(3)Cu(OH)_(2)膜。结论根据腐蚀产物的元素分析可知,在HCO_(3)^(-)和SO_(4)^(2-)共同存在的环境中,铜具有很高的点蚀敏感性,T2紫铜管很容易发生局部腐蚀,加之氧浓差电池的作用,水线部位铜管发生严重的点蚀以致穿孔失效。

加装螺旋导流板的双层铜管换热器传热性能分析

为提高螺旋铜管(SCT)换热器的综合传热性能,通过在换热器内加装螺旋形导流板,采用双向流固耦合计算方法,分析了不同入口流速和导流板安装位置下对换热器内部双层SCT的振动和传热性能的影响。数值结果表明:双层SCT换热器外层SCT的振动强度明显高于内层;无振动时内层SCT的传热系数高于外层,有振动时外层SCT的传热系数高于内层;随着入口流速增加,内外层SCT的振幅均增大,传热系数提高;导流板的安装位置会直接影响SCT的振动和传热特性,且在SCT呈现最大振动强度和最佳传热性能时的安装位置并不相同;对比振动强化传热参数Q PEC和综合传热性能因子R JF发现,双层SCT换热器的Q PEC和R JF均高于单层,两螺旋导流板分别安装在换热器的左、下位置时,Q PEC最大,安装在换热器的左、上位置时,R JF最大且比安装在左、下位置时最高增大了7.99%。该研究可为高性能SCT换热器的设计提供理论和数据支撑。

基于有限元模拟的水平连铸TP2铜管坯一次冷却结构优化研究

对比多种结晶器结构下温度场、速度场等分布状态及石墨模具内部温度变化趋势,探究其对铜套、石墨模具等易损件及铜管铸坯温度变化的影响。结果表明,在一次冷却结构增设12道Φ10 mm且倾斜角度为30°的流槽,可使冷却水流态平稳均衡,铜套受热均匀,有利于铸坯周向同时凝固。本文通过有限元软件模拟铜管水平连铸过程一次冷却结构优化对温度的影响,为生产企业改善产线冷却效果,提高产品质量,降低模具成本和延长使用寿命,提供了实验参照和理论指导。

铜管坯水平连铸水冷调控与实验分析

为实现传统铜管坯水平连铸水冷控制系统在线自动化精准控制,提高生产质量与精度,改善管坯组织性能,对现有铜管坯水平连铸一冷水控制进行分析。采用程序设计和物理实验验证的方法,开展了基于可编程逻辑控制器(PLC)闭环策略下石墨结晶器冷却水量自动控制的相关研究。实验结果表明,基于闭环控制逻辑的自动水冷控制系统可以将流量波动控制在±0.5 L/min范围内,离散系数为2.68×10^(-3),明显小于传统水冷控制系统,铜管坯水平连铸一次冷却水闭环控制系统可以实现连铸过程的精确控制。

某油冷却器换热管泄漏原因

某公司生产的油冷却器换热管在投入使用9~12个月后发生腐蚀泄漏现象。采用宏观观察、化学成分分析、金相检验、扫描电镜和能谱分析、原子吸收光谱分析等方法分析了管道腐蚀泄漏的原因。结果表明:油冷却器换热管介质中的氯离子和硫离子在管内壁积垢中沉积并富集在管壁基体前沿,导致内壁产生大量点腐蚀,点腐蚀位置与未腐蚀位置形成大阴极小阳极腐蚀电池,增大了腐蚀速率,在管内介质的冲刷作用下,点腐蚀坑进一步扩大,最终导致管道泄漏。

TP2铜管精整工序喷墨质量不良原因分析及改进措施初探

在精密铜管精整复绕工序中,涡流探伤装置检测到伤点后会向喷墨装置发送信号,以对铜管表面缺陷进行喷墨标记,但是该过程普遍存在喷墨不良,严重影响了对缺陷的判断。本文介绍了TP2铜管生产线中涡流探伤仪器的工作原理,对原有的涡流探伤仪器、喷墨装置以及喷枪结构进行调研,分析了原有喷墨装置喷墨时存在的漏墨和拖墨问题,探讨了等离子技术与激光刻蚀技术作为喷墨技术替代方案的可能性。文献调研、现有技术分析及其他替代试验的结果表明,采用等离子体表面处理技术对已喷墨铜管进行处理后,可以一定程度地改善铜管拖墨的问题;采用功率为300 W的激光对铜管表面进行刻蚀处理,激光头速度分别为80 mm/s和200 mm/s时,对铜管表面刻蚀呈现出的不同效果,均能够进行缺陷的有效标识。因此,铜管表面激光刻蚀技术可以作为喷墨技术的替代方案。

无压烧结工艺对浆料直写式定向多孔铜组织及致密度的影响

管式炉无压烧结工艺对浆料直写(Direct ink writing,DIW)式定向多孔铜的组织和致密性起决定性作用。本工作通过浆料直写和烧结制备定向多孔铜,通过X射线衍射仪(XRD)和扫描电子显微镜(SEM)对比高纯氩气和Ar-H_(2)混合气下烧结后的定向多孔铜的微观组织,分析烧结时定向多孔铜的氧化行为。在不同烧结参数下对定向多孔铜进行烧结处理,研究烧结温度以及保温时间对定向多孔铜致密度的影响规律。结果表明:在高纯氩气下烧结时,定向多孔铜发生严重氧化并生成Cu_(2)O,而Ar-H_(2)混合气通过还原作用有效避免定向多孔铜的氧化;烧结温度1100℃、保温时间6 h为最佳烧结工艺参数,在此条件下,定向多孔铜的致密度达到了87.2%,收缩率为33.3%。本研究可为管式炉无压烧结DIW打印多孔铜提供理论指导。

旋流条件下螺旋弹性铜管振动强化传热性能分析

为了充分利用流体诱导螺旋弹性铜管(helical elastic copper tube,HECT)振动增强传热,以获得更高综合传热性能的HECT换热器装置,基于安装正向螺旋引流板的螺旋弹性铜管(helical elastic copper tube-forward spiral baffle,HECT-FSB)换热器和逆向螺旋引流板的螺旋弹性铜管(helical elastic copper tube-reverse spiral baffle,HECT-RSB)换热器,采用双向-流固耦合法,研究了旋流条件下入口流速(U_(in))对HECT振动强化传热性能的影响。研究表明:U_(in)在计算范围内增加,HECT的振幅增大、传热系数提高,HECT换热器的进出口压降增大、PEC(performance evaluation criteria)值减小;HECT-RSB换热器的HECT振幅和传热系数、进出口压降明显高于HECT-FSB换热器。HECT-FSB换热器的PEC值高于HECT-RSB换热器,振动强化传热性能更佳,当U_(in)=0.3 m/s时,PEC值高出了9.00%。HECT-RSB换热器的综合传热性能因子JF值最大,综合传热性能最佳,与已发表文献中的换热器相比,U_(in)在计算范围内综合传热性能因子JF值平均提升了2.7%。该研究可为HECT换热器装置综合性能的提升提供技术支撑。