【作者】 李远辉；

【导师】 罗德福；

【作者基本信息】 江苏大学 ， 材料学， 2007， 博士

【摘要】 QPQ技术的实质是在盐浴渗氮或盐浴氮碳共渗之后,再进行盐浴氧化、抛光和二次氧化的工艺方法。此技术在汽车、模具等耐磨性要求较高的行业已经得到了广泛的应用。近年来,QPQ处理的工件良好的耐磨性和高抗蚀性的结合引起了其它行业的重视,如活塞杆、石油开采等行业。活塞杆等以前使用镀铬技术的产品,因环保问题的原因,现在普遍采用QPQ技术进行处理。在这些产品中,国内外对耐磨性和抗蚀性都有较高的要求。这为QPQ技术的推广提供了一个极好的舞台。石油管在从出厂到放入油井中使用这段时间之内,直接放在大气之中,经常在下井时,油管表面已经生锈,这必然影响石油管在下井后的使用性能。这两种情况都要求QPQ处理的产品有较好的在大气条件下的抗蚀性。在本论文的研究中,针对上述两个实际应用中的问题,采用了两种试验方法评价QPQ处理后试样在大气下的抗蚀性。第一种方法是将QPQ处理试样放入3‰H₂O₂+10%NaCl（以重量百分比计算）溶液中做浸泡腐蚀试验。用精度为万分之一克的电子天平称量试样浸泡前后的质量,计算腐蚀质量损失。第二种方法是将原材料加工成Φ20×100mm的圆柱试样,经QPQ处理后把试样放入盐雾试验箱中,做5%NaCl溶液中性盐雾试验,试验温度35℃,试验时试样与垂直方向成30°。通过分析各种工艺因素对QPQ处理的试样在大气中抗蚀性的影响规律,最终获得能得到最佳抗蚀性的工艺。首先是工件在QPQ处理前的预处理过程中,尽量清洗干净,活化金属表面。第二,工件初始表面粗糙度应保持在0.18微米以内,以防工件表面峰谷中的污垢影响渗氮。第三,在QPQ盐浴渗氮过程中,调整好炉子中盐浴的状态,使渗氮工件的化合物层有尽量多的致密层和较少的疏松层,让闭塞电池没有形成条件,从而可以提高抗盐雾试验的能力。第四,渗氮后进行氧化,在表面形成更抗蚀的四氧化三铁氧化膜,进一步提高抗蚀性。第五,对氧化后的工件进行抛光,抛光应抛掉表面疏松层。抛光后进行二次氧化。第六,氧化后用密封剂浸渍,进一步弥补氧化膜的不均匀和破损所带来的对抗蚀性的损失,填充可能未完全抛掉的孔洞。待密封剂干后,将试样浸防锈油。目前,我国许多主力油田已进入中、高含水开发期,随着综合含水的不断上升,油、气、水集输系统的腐蚀日趋严重,腐蚀成为影响管道系统可靠性及使用寿命的关键因素,是造成管道事故的最主要原因。油管在油井中服役时,既要求具有高的抗蚀性,也要求承受一定的应力。本论文针对油管在油井中使用的实际情况,利用高压釜腐蚀试验来评价QPQ处理的N80钢的抗CO₂腐蚀性能。试验时,采用油田模拟溶液作为腐蚀介质,在放入试样后,先对高压釜通入高纯氮气2小时除氧,然后再充入CO₂至设计压力。为评价油田中使用油管时的抗H₂S腐蚀性能,采用了抗H₂S恒载荷拉伸试验。通过未处理的试样和QPQ处理试样的对比,评价QPQ处理试样的抗H₂S腐蚀性能。针对石油管服役时的力学性能要求,我们采用API 5CT标准规定的具体方法,制作标准试样,通过常规力学拉伸试验和冲击试验,获取QPQ处理试样的抗拉强度、屈服强度、伸长率和冲击功的试验数据,分析QPQ工艺参数变化对力学性能的影响规律。通过上述试验,获得了能够同时满足抗蚀性和力学性能要求的处理N80钢石油管的QPQ工艺,主要要求渗氮温度在650℃以上,渗氮时间90分钟左右。在QPQ处理后,需要在密封剂中浸泡,然后浸防锈油。更多还原

【Abstract】 QPQ technology contains mainly salt bath nitriding or salt bath nitrocarburising, salt bath oxidizing,polishing and second salt bath oxidizing.It has been used widely in automobile and die industries which demand good wear resistance.In recent years, because QPQ treated workpieces combine good wear resistance and high corrosion resistance,QPQ technology attracts attention of many other industries,such as piston pole and petroleum.In piston pole and other similar industries,chromeplating technology was used in the past.Now QPQ technology is widely used in these industries for environment protecting problem.In these industries,high corrosion resistance and high wear resistance are all needed.It provides a good stage for QPQ technology.Oil tubes were placed in atmosphere directly before they were used in oil well.When they were placed in oil well,the surface had rusted already.It will deteriorate the corrosion resistance.In this paper,for the above two problems in practice,two experiment methods were adopted to evaluate the corrosion resistance in atmosphere environment.The first method is immersion test.The immersion solution is 3‰H₂O₂+10%NaCl water solution by weight.Before and after the immersion test,the weight of specimens was quantified by electrical scale accurate to 0.0001 gram.The balance of them is the corrosion weight loss.The second method is neutral salt spray test.The solution used in this test is 5%NaCl water solution and the test temperature is 35℃.In the test,theΦ20×100mm cylinder specimens were placed 30°from the vertical direction.For the best corrosion resistance,an appropriate technics was attained by analyzing the relations of processing and the corrosion resistance.Firstly,wash and activate the workpieces during pretreatment.The second is to limit the roughness to 0.18μm.The third is to adjust the salt in the furnace and ensure the nitrided workpieces have compact compound layer to enhance the rust starting time in salt spray test.The fourth is to oxidize the workpieces after nitriding.The aim is to develope Fe₄O₃ oxidizing film to increase the corrosion resistance.The fifth is polishing and second oxidizing.During polishing,the porous compound layer should be eliminated completely.The sixth is immerse the workpieces in sealant to compensate the decreasing of corrosion resistance for the breakage of oxidizing film.After the sealant becomes dry,immerse the workpieces in antirust oil.At present,many oil fields in China come into middle-high hydrous exploitation period.With the increasing of water content,the corrosion of transportation system of oil,gas and water becomes more badly.Corrosion is the main cause of dependability and invalidation of oil tube.When oil tube is in use,it would endure corrosion and bear the stress.In this paper,considering circumstance of oil tube in oil well,autoclave test was used to evaluate the corrosion resistance of N80 steel in CO₂ solution.In the test,the solution is simulated oil field water.Before CO₂ was filled to scheduled pressure,oxygen was eliminated by pure nitrogen.To evaluate the corrosion resistance of oil tube steel in H₂S solution,constant force tensile test was adopted.Through the compare of untreated specimens and QPQ treated specimens,the corrosion resistance of oil tube steel in H₂S solution was evaluated.We manufacture specimens according to API 5CT standard.Though the tensile tests and impact tests,the tensile strength,yield strength,elongation and impact energy were attained.We analyzed the relations of QPQ processing parameter and mechanical properties too.Through the above tests,we attained the QPQ technics to treat N80 oil tube to meet the demands of high corrosion resistance and mechanical property at the same time.It demands the nitriding temperature should be above 650℃and nitriding duration should be about 90 minutes.After QPQ treatment,the workpieces should be immersed in sealant and antirust oil.更多还原