【作者】 王崧全；

【导师】 张德坤；

【作者基本信息】 中国矿业大学 ， 机械设计及理论， 2014， 博士

【摘要】 矿井提升用钢丝绳作为一种承载部件，连接着提升机和提升容器，担负着提升煤炭、矸石，下放材料、升降人员和设备的任务。在矿井提升过程中，钢丝绳承受着反复地拉伸、弯曲和扭转载荷；同时矿井的淋水作用使提升钢丝绳长期处于高湿和酸碱浸蚀的恶劣环境中，这导致提升钢丝绳的腐蚀现象十分严重。钢丝绳在服役过程中承受着外加应力与腐蚀的共同作用，其内部钢丝会产生极其危险的低应力破坏形式，在恒定应力或者慢速率应变状况下会产生应力腐蚀开裂；而在循环交变拉应力与腐蚀的共同作用下，钢丝又极易发生腐蚀疲劳断裂。针对这些存在问题，本文主要对矿用钢丝在特定矿井腐蚀环境中的电化学腐蚀行为、应力腐蚀行为及腐蚀疲劳行为进行研究，同时对钢丝腐蚀与应力之间的交互作用对钢丝寿命影响进行系统研究，开展的研究内容及获得的主要结论如下：（1）通过对不同表面处理方式的钢丝在不同腐蚀溶液中的极化曲线进行分析，获得了钢丝在不同条件下的阴、阳极反应过程，发现钢丝腐蚀过程中表面有腐蚀产物膜生成，膜对钢丝基体的保护作用与溶液的腐蚀性及浸泡时间有关。使用Tafel直线外推法对极化曲线进行分析，获得了钢丝在不同阶段的腐蚀电位及腐蚀电流密度的变化规律，发现裸钢丝在酸性溶液中的腐蚀速度最快，不同条件下钢丝的耐蚀性与浸泡时间有关。对钢丝在不同条件下的电化学阻抗谱(EIS)进行了测量，并通过Zsimpwin软件对Nyquist图进行拟合获得了钢丝在不同条件下的等效电路，对了解钢丝电化学腐蚀过程提供了理论依据。（2）采用光滑无缺口钢丝进行慢应变拉伸试验(SSRT)，探讨不同外加电位、不同腐蚀溶液对钢丝应力腐蚀开裂(SCC)敏感性的影响，结果表明钢丝在三种溶液中均有SCC敏感性，其中酸性溶液中在外加Ecorr+400mV电位时，钢丝的抗拉强度最低，约1673MPa，平均延伸率也最低，约为14.71%。腐蚀溶液中拉伸断口形貌与空气中拉伸相似，以韧窝形貌为主，在SCC敏感区伴随有少量脆性断裂特征。酸性溶液中随着外加阳极电位的增大，由阳极溶解作用导致的SCC倾向降低，在开路电位下钢丝产生的SCC倾向较弱，而中性及碱性溶液中钢丝随着外加阳极电位的增大，由阳极溶解作用导致的SCC倾向增大；在外加阴极电位时，三种溶液中钢丝SCC机制均完全受氢脆机制影响，随外加阴极电位的负移，析氢反应剧烈导致氢含量明显增大，SCC敏感性增强。研制了一种钢丝恒应力腐蚀试验机，通过钢丝在不同溶液中、不同外加恒定应力下的应力腐蚀试验，获得了腐蚀电位与Nyquist图随时间的变化曲线，结果表明，外加应力会造成钢丝腐蚀电位的降低，这一规律受溶液腐蚀强弱影响，同时外加应力对钢丝的Nyquist图影响剧烈，其中试验1h后，酸性溶液中在外加1125MPa时低频容抗弧半径最大。（3）开展了钢丝的腐蚀疲劳试验，对比分析了钢丝在空气及不同腐蚀溶液中的S-N曲线，发现钢丝在酸性溶液中的腐蚀疲劳寿命最短，碱性次之，中性最大，应力与腐蚀对腐蚀疲劳寿命的降低有相互促进的作用。通过不同应力比、不同频率下钢丝的腐蚀疲劳试验结果发现，应力比越小、频率越高时，腐蚀疲劳寿命越小，裂纹萌生主要与钢丝本身缺陷及形变活化有关，而应力比越大，频率越小时，钢丝腐蚀疲劳寿命越大，裂纹萌生主要受阳极溶解机制控制。通过对不同外加电位下钢丝的腐蚀疲劳行为研究发现，阳极极化作用能大大降低钢丝的腐蚀疲劳寿命，钢丝断口疲劳源处有明显韧窝形貌，韧窝区面积随着外加阳极电位的增大而增加；外加阴极极化电位时，阴极反应生成的氢无法进入钢丝基体，腐蚀疲劳寿命由于对阳极溶解反应的有效阻碍而大大增大，钢丝断口较为平滑，显示明显的脆性断裂机制。（4）通过有限元建模探讨了不同大小点蚀坑、不同外加应力对钢丝点蚀坑内部应力分布的影响规律，发现外加拉应力越大，点蚀坑底部应力集中越明显，等效应力越大，应力集中处有沿垂直于外加拉应力的方向向外扩展的趋势（主裂纹扩展方向），而当外加拉应力相同时，腐蚀程度越严重，点蚀坑半径越大，等效应力越大，主裂纹向垂直于外加拉应力的方向扩展的趋势越明显。分析了复杂应力状态（包括应力比及加载频率）对钢丝点蚀坑内应力分布的影响，发现不同应力条件下钢丝点蚀坑附近等效应力分布相差不大，各点的等效应力与距离点蚀坑底部的位置有关。通过理论计算了在不同外加应力下，不同直径的点蚀坑底部阳极腐蚀电流密度(iσ)的大小，结果发现提高外加拉应力或增大点蚀坑半径均能增大iσ。更多还原

【Abstract】 As a load bearing member to connect the hoist and lifting container, wire ropefor mine hoisting has the mission of promotion of coal and gangue, decentralization ofmateirals, movement of personnel and equipment. During mine hoisting, the ropes aresubjected to externally applied tensile load, cyclic axial load and cyclic bending load.While the corrosion phenomenon of steel wire is very serious for the harshenvrionment of high humidity and acid erosion. Furthermore, wire rope will enduregreat applied stress in the process of servicethat produce extremelydangerous low-stress damage form under the combined action of stress and corrosion,therefore, constant stress or slow rate of strain conditions will result in stresscorrosion cracking. In the joint action of cyclic tensile stress, steel wire is prone toproduce corrosion fatigue fracture. In view of this situation, the paper focuses onimprove electrochemical corrosion behavior, stress corrosion behavior and corrosionfatigue behavior of steel wire for hoisting under specific mine corrosive environmentas well as systematically investigate the impacts of corrosion-stress interaction onlifetime of steel wire. The main research contents and the resulting conclusions are asfollows:(1) Through analysis of polarization curves of the steel wire in different corrosivesolutions with different surface treatments to obtain the anode and cathode reactionprocess of wire under different conditions. The results showed that corrosion productfilm was generated in the corrosion process of steel wire. The protection of the film tosteel substrate was related to the solution of corrosive and soaking time. The variationof corrosion potential and corrosion current density in different stages was acquiredby the analysis of the polarization curve using Tafel linear extrapolation. The resultssuggest that the corrosion rate of bare wire is the fastest during the whole process ofsoaking in acid solution, and the corrosion resistance of steel wire under differentconditions was associated with immersion time. Electrochemical impedancespectroscopy (EIS) of steel wire under different conditions were measured. Theequivalent circuit of steel wire under different conditions was acquired by usingZsimpwin software to fit the Nyquist diagram, which provided a theoretical basis tostudy the electrochemical corrosion process.(2) Slow strain rate tensile test (SSRT) was conducted with smooth wirewithout gap to investigate the influence of different applied potentials and different corrosion solutions on the sensitivity of stress corrosion crack. The result suggestedthat the steel wires in three different solutions had SCC susceptibility. The steel wirein acid solution under Ecorr+400mV had the minimum tentile strength of about1673MPa, and the minimum average elongation of about14.71%. The fracturemorphologies of steel wires in corrosion solutions were similar to the morphology inair, which were mainly the dimple pattern. The SCC sensitive area was accompaniedby minor brittle fracture characteristics. The tendency of SCC caused by anodicdissolution will decrease with the raise of the anode potential in acid solution. And theSCC sensitivity under the open circuit potential was weaker. However, the tendencyof SCC created by anodic dissolution will increase with the raise of additional anodepotential in neutral and alkaline solution. The steel wire SCC mechanisms arecompletely influenced by hydrogen embrittlement mechanism in these three solutionswhen they are couple with cathode potential. Vigorous hydrogen evolution reactioncontribute to obvious hydrogen content increase and enhancement of SCC sensitivityalong with the negative shift of applied cathode potential.A constant stress corrosion testing machine of steel wire is developed to acquirethe corrosion potential and Nyquist curves over time through stress corrosion test ofthe steel wire in different solutions and different applied constant stress. It turned outthat the applied stress may reduce steel corrosion potential which is influenced bysolution corrosion strength. The influnce of applied stresses on the Nyquist diagram ofsteel wire is violent. The radius of low-frequency capacitive when applied1125MPain acid solution is the biggest after1h.(3) Corrosion fatigue tests of steel wires were conducted to compare the S-Ncurves in the air and different corrosive solutions. The findings showed that the wirehad shortest corrosion fatigue lifetime in acidic solution with alkaline take the secondplace, and then followed by neutral solution. Moreover, stress and corrosion had amutual promotion relationship on reduction of fatigue lifetime. The results of steelcorrosion fatigue test under different stress ratio and different frequency showed thatthe smaller of the stress ratio and higher of the frequency had a shorter corrosionfatigue lifetime of steel wire. The initiation of crack is mainly controlled by anodicdissolution mechanism. The corrosion fatigue behavior of steel wire under differentapplied potential study showed that anode polarization effect could significantlyreduce the corrosion fatigue lifetime of the wire and obvious fracture morphologymay occurred at wire fracture fatigue source. The area of dimple region may increase with the raise of applied anode potential. When applied with cathodic polarizationpotential, the hydrogen produced by cathodic reaction of hydrogen was not able toenter into the steel substrate and the corrosion fatigue lifetime may significantlyprolonged as a result of effective obstruction of anodic dissolution reaction. Therelatively more smooth fracture suggested a clear and definite brittle fracturemechanism.(4) The effect of different pits sizes and different applied stress on internal stressdistribution of pit was investigated through finite element model. And the findingsindicated that the greater of the external tensile stress, the tendency of stressconcentration at the bottom of pits were more obvious with which accompanied byhigher equivalent stress. The stress concentration area was likely to extend out alongby the direction of applied stress vertical line (main crack propagation direction). Thelarger radius of pits and stronger equivalent stress were also visible for the severecorrosion tend when the external stress is the same.The extension tendency was moreobvious for main crack vertical to the applied stress. The effect of complex stress state(including stress ratio and loading frequency) on steel wire pits stress distribution wasanalyzed to find that different conditions may lead to similar equivalent stressdistribution around the pits and equivalent stress of each point was relevant to thedistance from the bottom of the pits. The magnitude of anodic corrosion currentdensity (iσ) at the bottom of the pits of different diameter was calculated underdifferent applied stress by theoretical calculation to find that improved external tensilestress and increased pits radius was able to increase iσ.更多还原