烟气脱硝用尿素水解装置关键部件用候选材料的腐蚀行为

在模拟烟气脱硝的尿素水解环境中研究了尿素水解装置关键部件用候选材料316L不锈钢、316Lmod不锈钢、HR3C不锈钢、Inconel718合金和TC4合金的腐蚀行为。结果表明:316L与316Lmod不锈钢在腐蚀初期均出现不同程度的溶解腐蚀,腐蚀后期316L不锈钢的腐蚀产物沉积量增多,腐蚀产物出现大面积剥落,腐蚀过程以点蚀为主,而316Lmod不锈钢则以均匀腐蚀、腐蚀产物沉积为主;TC4合金、Inconel718合金与HR3C不锈钢均具有比316L和316Lmod不锈钢更好的耐蚀性能;TC4钛合金表面形成一层约3μm厚的致密钛氧化层,腐蚀过程中水热合成了Cr_2O_3和Fe_2O_3产物;Inconel718合金在腐蚀初期出现少量溶解腐蚀,后期以大量氧化物沉积为主;HR3C不锈钢在腐蚀初期发生了明显的晶间腐蚀,之后以腐蚀产物沉积为主。     

甲胺升压系统尿素级不锈钢高压管道的焊接

介绍了尿素级不锈钢316L＋G510管道材料的性能特点和技术要求,通过焊接工艺评定制定正确的焊接工艺,成功完成尿素级不锈钢管道的焊接工作。     

尿素级不锈钢管道的焊接技术及质量控制

尿素装置具有高温、高压、易燃、易爆和易腐蚀等特点,属于特别危险生产区域。尿素装置工程管道是重点,应用于主要工艺介质管道的尿素级不锈钢的焊接则是重中之重。本文结合实践,归纳论述了尿素级不锈钢焊接的质量控制。     

316、317不锈钢耐氯离子腐蚀能力浅析

奥氏体不锈钢虽然耐大多数介质的腐蚀,但对氯离子腐蚀却比较敏感,文中通过比较316、317不锈钢不同牌号化学成分的不同,以氯离子对金属材料的腐蚀机理为基础,参照国内外不同行业标准对奥氏体不锈钢耐氯离子浓度的规定,利用耐点腐蚀能力指数公式,得出316、317各牌号不锈钢耐氯离子腐蚀能力的差异。     

有机硅涂层对316不锈钢的防护

研究了316不锈钢在高温（400℃）盐和水蒸气综合作用下的腐蚀行为及添加Al粉和Ti粉的有机硅涂层对不锈钢的防护作用。结果表明，316不锈钢裸样发生了较为严重的腐蚀。刷涂了有机硅涂层的316不锈钢在相同的条件下没有发生腐蚀，涂层对316不锈钢具有优异的防护作用．讨论了有机硅涂层的防护机理。     

304、316不锈钢和Inconel 617镍基合金在硝酸熔盐中的腐蚀行为

将304、316不锈钢和Inconel 617镍基合金在565℃硝酸熔盐(60%NaNO_3+40%KNO_3,质量分数)中进行长时静态腐蚀试验,对比研究了3种材料的腐蚀动力学曲线以及表面腐蚀形貌、物相组成和微区成分。结果表明:3种材料均发生了氧化腐蚀,其中304和316不锈钢具有抛物线型的腐蚀动力学特征,而Inconel 617镍基合金在短暂质量增加之后出现了明显的腐蚀质量损失现象;Inconel 617镍基合金的耐腐蚀性能最好,304不锈钢的最差;在腐蚀初期,304、316不锈钢表面均形成了针状和片状腐蚀产物,随着腐蚀时间的延长,腐蚀产物转变为尖晶石结构,Inconel 617镍基合金表面的腐蚀产物呈颗粒状,随着腐蚀时间的延长,部分颗粒变大;304和316不锈钢表面均形成了以Fe_2O_3和(Fe,Cr)_3O_4为主的腐蚀产物层,Inconel 617镍基合金表面则形成了以NiO和CoO为主的腐蚀产物层。     

氯离子杂质对304和316L奥氏体不锈钢在熔融硝酸盐中腐蚀行为的影响

采用恒温全浸腐蚀试验方法,研究了304和316L奥氏体不锈钢在565℃含不同质量分数（0,0.6%,1.0%,1.4%）氯离子杂质熔融硝酸盐（60%NaNO₃+40%KNO₃,质量分数）中的腐蚀行为。结果表明：在4种熔融硝酸盐中,304和316L不锈钢的腐蚀动力学曲线均呈抛物线型;随着氯离子含量增加,304和316L不锈钢的腐蚀速率均显著提升,腐蚀程度逐渐加重,腐蚀产物层在与基体结合处的裂纹增多,氯离子杂质通过活性氧化腐蚀作用加速了不锈钢腐蚀;与316L不锈钢相比,304不锈钢对氯离子杂质的腐蚀作用更敏感。     

316LN奥氏体不锈钢在含Cl-溶液中的腐蚀行为

采用慢应变速率拉伸法以及电化学方法,通过与316L奥氏体不锈钢进行对比,研究了316LN奥氏体不锈钢在不同温度(25,50℃)和不同腐蚀介质(质量分数为3%的NaCl溶液、质量分数为6%的FeCl₃溶液)中的应力腐蚀开裂和电化学腐蚀行为。结果表明：316LN钢在含Cl^-溶液中的应力腐蚀敏感性低于316L钢;316LN钢在NaCl溶液中发生钝化-击穿行为,而在FeCl₃溶液中则呈现活性溶解特征,阻抗谱均为单一容抗弧特征,且温度越高,316LN钢的自腐蚀电流越大,容抗弧半径和电荷转移电阻越小。316LN钢的耐腐蚀性能优于316L钢。     

在用尿素合成塔衬里更新修理

814F是兰石厂在1982年为刘家峡化肥厂制造的第二台尿素合成塔。尿素是中性高效氮肥，是我国大型化肥生产发展的重点，由于合成尿素过程中存在氨基钾酸按、氢氧酸按具有强烈的腐蚀性，因此，对设备耐蚀性要求较高，目前水溶液全循环流程工艺生产尿素所采用的尿素合成塔多为村里结构。我厂已有几十年制造尿素合成塔的经验，村里材料316L钢板在尿素合成塔中经过30000h液相挂片试验，显微分析结果表明：主要是晶间腐蚀，其次也可看到均匀腐蚀和局部集中腐蚀，物料冲刷腐蚀也不可忽略。814F尿素合成塔材质为BHW35＋316L（原衬里、厚6mm）．重…     

熔渗铜锡316L不锈钢的制备与性能

利用熔渗Cu90Sn10工艺制备粉末316不锈钢,研究了压制压力、熔渗温度对材料性能和组织的影响。结果表明：利用熔渗法可制备高致密的316L不锈钢,相对密度可达98％以上;基体骨架孔隙率应保证在189／6～229／5左右。熔渗后316L烧结不锈钢的硬度从49HRB提高至88HRB,且塑性也有所提高。同时,耐腐蚀性能也有很大提高,其腐蚀电位为-212mV,接近致密316L不锈钢。随着骨架密度的提高,熔渗制品密度基本不变,但硬度明显下降。应防止熔渗温度过高而使晶粒过分长大。     

高温碱液浓度与温度及应变速率对316L不锈钢应力腐蚀开裂的影响

通过不同应变速率的拉伸试验,研究了316L不锈钢在不同温度和浓度的NaOH溶液中的应力腐蚀开裂行为,分析了以上三个因素对该钢应力腐蚀开裂的影响.结果表明:当应变速率为10-5s-1时,316L不锈钢不会发生明显的应力腐蚀开裂,而当应变速率降低到10-6s-1时,在高温低浓度的NaOH溶液中该钢会发生明显的应力腐蚀开裂;当应变速率为10-6s-1时,NaOH溶液温度对316L不锈钢应力腐蚀开裂的影响程度要高于浓度的.     

Failure analysis of melt urea pump impeller

Abstract

A melt urea pump is out of work after only 6 days in service. The failure of the melt urea pump impeller is analysed using different methods including chemical composition analysis, metallographic observation, SEM and energy dispersive spectroscopy analyses, etc. The results show that the material of the impeller is not the reported AISI 321 stainless steel but AISI 316 stainless steel. There are many honeycombed holes on its impeller, which is the typical feature of cavitation damage. Therefore, the main failure reason of the impeller is the cavitation erosion, and the electrochemical corrosion of the medium also accelerated the failure of the impeller. The failure of the impeller is not related with the as casted defects of the material because no obvious as casted defects are found in the material.     

不锈钢内衬背侧缺陷Lamb波检测技术

根据Lamb波波动特性的Rayleigh-Lamb方程,推导出了316LMod不锈钢薄板相速度和群速度的频散曲线,为导波模式的识别和参数的选择奠定了基础。并通过对人工缺陷导波模式进行二维傅立叶变换,提取出背侧裂纹缺陷的主要Lamb模式,进而确定了8 mm厚316LMod不锈钢背侧裂纹的导波检测参数。最后通过含人工缺陷试块,绘制出了8 mm厚316LMod不锈钢背侧裂纹缺陷当量评定图,从而实现了对背侧裂纹缺陷的Lamb检测的定量评价。并通过尿素合成塔检测实例验证了该方法的有效性。     

Erosion–corrosion and corrosion properties of DLC coated low temperature gas-nitrided austenitic stainless steel

Low temperature nitriding of stainless steel leads to the formation of a surface zone of so-called expanded austenite, i.e. by dissolution of large amounts of nitrogen in solid solution. In the present work the possibility of using nitrogen expanded austenite “layers” obtained by gaseous nitriding of AISI 316 as substrate for DLC coatings are investigated. Corrosion and erosion–corrosion measurements were carried out on low temperature nitrided stainless steel AISI 316 and on low temperature nitrided stainless steel AISI 316 with a top layer of DLC. The combination of DLC and low temperature nitriding dramatically reduces the amount of erosion–corrosion of stainless steel under impingement of particles in a corrosive medium.     

Corrosive wear of carbon and austenitic stainless steels in NaCl solution

The wear rates of an AISI 52100 carbon steel and a type 316 austenitic stainless steel and the corrosion current I from the rubbing steels were measured in NaCl solution to study the interrelationship between the corrosion and wear of the steels. An on-off cyclic loading test was also conducted to examine the effect of static corrosion during an unloading period on the corrosive wear of the steels.

It was found that the wear rates of the carbon steel and the type 316 stainless steel reach a maximum at NaCl concentrations of about 3% and 0.1% respectively. The on-off cyclic test has shown that corrosive wear of the steels is influenced by static corrosion during an unloading period. The increment †I of the corrosion current due to sliding was associated with the corrosive wear rate of the steels.     

New Experimental Rig to Investigate Abrasive–Corrosive Characteristics of Metals in Aqueous Media

A new tribometer to investigate a conjoint effect of three-body abrasion and corrosion has been developed. In this design, a flat wear sample is loaded against a rotating cylindrical disc counterface and the abrasive slurry is delivered to the contact interface. Capabilities of the newly developed tribometer have been assessed through conducting abrasion–corrosion tests involving simultaneous electrochemical measurements. In this work, the stability of the passive layer on stainless steel under three-body abrasive wear in a near neutral electrolyte was investigated using potentiodynamic polarization tests. 316L Stainless Steel wear samples were abraded by coarse garnet particles in an aerated sodium sulphate electrolyte. The effects of load and speed on the polarization curves and passivity of 316L steel were determined. It was found that under abrasion–corrosion conditions 316L steel became more thermodynamically active and the passive corrosion rate has increased. Increasing the contact load resulted in a small increase in the passive corrosion current, while increasing the rotating speed had the opposite effect of decreasing the current. Linear polarization resistance method was used to analyse corrosion current changes with time during abrasion–corrosion testing. The existence of three distinct stages was explained by the third-body effect on the corrosion potential and current. First stage was revealed by continuous decrease of corrosion potential. Then, the potential reached a plateau for the second and third stages. In the first and second stages, particle constraint in the contact zone plays the major role and a linear rise in corrosion current with time has been recorded. After a certain amount of surface roughening, no further increase in particles entrapment is expected. Therefore, in the third stage steady-state corrosion current values are anticipated. The rig developed can also be used to simulate two-body abrasion–corrosion. The capabilities of the new rig have been compared against other experimental set-ups used in studies of combined abrasion–corrosion behaviour.     

316L不锈钢管手工钨极氩弧焊焊接工艺

通过对316L不锈钢焊接性能的分析、手工钨极氩弧焊焊接过程的控制、焊后进行无损检测、晶间腐蚀、力学性能等项目的数据分析,焊接接头的机械性能和耐腐蚀性达到了工艺要求,保证了316L不锈钢管的焊接质量,为广大焊接工作者提供参考。     

射频／直流磁控溅射不锈钢／Al2O3复合薄膜组织与性能研究

利用射频/直流碳控溅射法,制备了316L不锈钢/Al2O3陶瓷复合薄膜,研究了316L不锈钢/Al2O3陶瓷复合膜的组织形貌。测试了薄膜的显微硬度和耐磨性。结果表明：直流磁控溅射316L不锈钢薄膜呈柱状晶结构,主要有Fe-Cr和γ-Fe相构成,在Fe-Cr(110)晶面出现明显的择优取向,由于射频溅赈射Al2O3陶瓷的掺合,使316L不锈钢/Al2O3陶瓷复合薄膜柱状晶细化,并出现二次柱状晶,在Fe-Cr（211）晶面出现明显的掺优取向, 316L不锈钢膜硬度明显高于316L块体,掺合了Al2O3的金属/陶瓷复合薄膜耐磨性有显著的提高。     

不锈钢在压力容器中的应用及焊接技术(一)

通过对我国20世纪尿素不锈钢的焊接、腐蚀性能的研究及大型尿素设备、双相钢设备和高级不锈钢设备及管道的制造与焊接技术的回顾，介绍不锈钢在一些典型压力容器中的应用并展望其扩大应用的前景。