酸洗和固溶处理对不锈钢抗点蚀性能的影响

研究了酸洗和固溶处理对８种不锈钢筋电阻对焊接头抗点蚀能力的影响。研究发现,酸洗和因咱都有效地改善和恢复不锈钢电阻对焊接头的抗点蚀性能。对于普通双相钢,固溶处理比酸洗能更有产地改善接头的抗点蚀性能,并无晶粒粗化。对于奥氏体钢和超纸奥氏体风,固溶处理的效果不及酰洗,且会引起母材晶粒粗化。对含Ｍｏ含Ｎ较高钢种的对焊接头,两者的更佳,尤其是两者综合处理后的接头,其临界点蚀温度ＣＰＴ其至高于对应母材经酸洗以     

固溶处理对254SMo钢焊接接头性能的影响

超级奥氏体不锈钢254SMo因其良好的抗点蚀和晶间腐蚀能力被广泛应用于化工等产业.针对254SMo焊接接头存在力学性能和耐腐蚀性能降低的情况,采用1150℃固溶处理方法改善其性能.采用GTAW焊接254SMo,并通过试验对比分析焊接接头在焊态和固溶处理状态下的力学性能、冲击韧性及耐腐蚀性能.结果表明:经1150℃固溶处...     

双相不锈钢焊接接头的耐腐蚀性能

根据母材临界点蚀温度(CPT)的试验结果,利用小试样的腐蚀实验方法研究了奥氏体-铁素体双相不锈钢焊接接头的耐点蚀性能.结果表明,手工电弧焊工艺过程对双相不锈钢材料的耐点蚀性能具有显著的影响,点蚀优先发生在焊缝金属或焊接热影响区中.双相不锈钢材料的耐点蚀性能与材料本身奥氏体和铁素体相比例有关.腐蚀试样的表面状态(粗糙程度)对母材金属的耐点蚀性能有明显的影响.表面越粗糙,耐点蚀性能越差,临界点蚀温度越低.     

固溶处理对多股绞丝焊接S32205双相不锈钢焊接接头组织及性能的影响

针对多股绞丝焊接的S32205双相不锈钢焊接接头，进行1080℃固溶处理。采用电子背散射衍射、扫描电镜、电子万能试验机以及电化学试验等手段，对比分析了固溶处理对焊接接头显微组织、力学性能以及耐点蚀性能的影响。结果表明，经过1080℃固溶处理，焊接接头主要合金元素得到充分扩散，组织更均匀，焊缝奥氏体体积分数增加11.2%,两相比例更均衡；焊接接头的平均抗拉强度提高了32.7 MPa,塑性略有改善，同时焊接接头的耐点蚀性能也有明显的提高。     

双相高铬铸造不锈钢的固溶处理对耐蚀性的影响

研究了不同固溶处理对双相铸造不锈钢的组织及其耐蚀性能的影响。结果表明，1050℃固溶处理，使钢有适量的均匀分布的奥氏体相，钢的抗均匀腐蚀、晶间腐蚀和抗点蚀性能最好。     

高温浓磷酸中不锈钢SAF2507焊接接头的耐蚀性能

采用动电位极化曲线和电化学阻抗谱结合光学显微镜研究了超级双相不锈钢SAF2507焊接接头经不同温度固溶处理后在高温浓磷酸中电化学行为。结果表明:2507不锈钢固溶处理可以改善原始焊接接头的组织提高其耐蚀性能;其中经950℃固溶处理后的焊接接头自腐蚀电流密度和致钝电流密度较小,极化后的电极表面点蚀较轻;腐蚀行为受电荷转移电阻和有限扩散层的混合控制,符合半无限扩散过程的特征;经950℃固溶处理后焊接接头在高温浓磷酸中形成的钝化膜较为致密。     

06Cr18Ni12Mo2Cu2奥氏体不锈钢焊接接头组织与力学性能

通过拉伸、弯曲、维氏硬度等试验以及金相分析,对06Cr18Ni12Mo2Cu2奥氏体不锈钢焊接接头的显微组织和力学性能进行了研究。结果表明:焊条电弧焊焊接接头有良好的抗拉性能和弯曲性能,焊缝区硬度略高于母材,而热影响区硬度略低于母材。焊缝组织为奥氏体+5%铁素体组织。焊接热影响区过热区奥氏体晶粒粗大,导致材料强度和硬度下降。     

Cr2N沉淀相对2101双相不锈钢焊接接头综合性能的影响

对经济型2101双相不锈钢焊接接头1050℃固溶后在700℃进行不同保温时间的时效处理.采用光学显微镜、SEM和TEM观察接头各区域的组织演变,对接头进行低温冲击试验和动电位极化腐蚀试验.结果表明,1050℃固溶处理改善了接头的组织和性能;700℃时效处理后焊缝和HAZ析出Cr₂N沉淀相,随着时效时间延长,沉淀相长大,数量变多并向铁素体内部生长,使接头冲击韧性降低,断口由塑性断裂的韧窝状转变为脆性断裂的解理状;固溶处理试样点蚀发生在铁素体内部,时效处理后点蚀发生在Cr₂N周围的二次奥氏体区,时效时间越长,接头的抗点蚀能力越差.Cr₂N的析出对接头焊缝区的影响最为显著.     

焊后热处理对2101双相不锈钢接头组织和性能的影响

采用等离子弧焊+手工电弧焊工艺焊接经济型双相不锈钢2101,焊接接头分别在1050、1150℃固溶处理,利用金相显微镜、SEM、EDS和低温冲击试验等方法分析了接头组织、成分和性能。结果表明:2101双相不锈钢焊接时焊缝和HAZ易生成沉淀相Cr2N,使接头冲击韧性下降;1050℃固溶处理可以消除沉淀相,均衡两相比例,保证接头性能;固溶温度进一步升高,接头组织中铁素体含量增多,晶粒粗化,性能恶化。     

固溶处理对304不锈钢焊缝腐蚀性能的影响

采用两种工艺对304不锈钢氩弧焊接接头进行固溶处理,并通过金相试验、阳极极化曲线测试以及全面腐蚀的实验,比较分析不同工艺对焊缝腐蚀性能的影响。结果表明：1200℃固溶处理后的焊接接头不锈钢可获得碳化物完全固溶于奥氏体基体内的均匀单相组织,从而提高其抗蚀性能;电化学腐蚀试验的结果也表明,在蒸馏水、5%H2SO45、%NaOH5、%NaCl和5%HCl介质中,经1200℃固溶处理的不锈钢焊缝的耐蚀性能均有不同程度的提高。304不锈钢焊接接头的优选固溶处理工艺为1200℃下保温60min并用木炭作覆盖剂。     

Die Oberflächenbehandlung von Schweißverbindungen hochkorrosionsbeständiger 6% Mo-Stähle und Nickel-Basis-Legierungen

Surface treatments of high alloy 6 Mo stainless steel and nickel alloy weldments High alloy stainless steels (6% Mo) and a high nickel alloy (alloy 625) weldment have been tested in order to answer the question whether post-treatment of the weldment has an effect on the corrosion resistance, especially on pitting corrosion. Therefore, the critical pitting temperature of weldments was tested in acidic chloride solution (standard tests). As a result grinding with rough emery paper as well as sand blasting lowers the localized corrosion resistance in the weldment area, while pickling has a positive effect, especially after blasting. Pickling can be done either by a solution of nitric + hydrofluoric acid or by a commercial pickling paste. In any event pickling is recommended as a final surface treatment for high alloy stainless steels and nickel alloys, especially in case of prevailing highly corrosive conditions such as pitting and crevice corrosion.     

Microstructure and corrosion behavior of shielded metal arc-welded dissimilar joints comprising duplex stainless steel and low alloy steel

This work describes the results of an investigation on a dissimilar weld joint comprising a boiler-grade low alloy steel and duplex stainless steel (DSS). Welds produced by shielded metal arc-welding with two different electrodes (an austenitic and a duplex grade) were examined for their microstructural features and properties. The welds were found to have overmatching mechanical properties. Although the general corrosion resistance of the weld metals was good, their pitting resistance was found to be inferior when compared with the DSS base material.     

Improvement of the Corrosion Resistance of High Alloyed Austenitic Cr-Ni-Mo Stainless Steels by Solution Nitriding

Characteristic features of austenitic steel grades combine a good corrosion resistance with a low hardness, wear resistance and scratch resistance. An interesting possibility for improving the wear behaviour of these steels without loss of their corrosion resistance lies in enriching the near surface region with nitrogen. The process of a solution nitriding allows the rise of the solution of nitrogen in the solid phase. On this state nitrogen increases the corrosion resistance and the tribilogical load-bearing capacity. The aim of the study was, to investigate the improvement of the pitting corrosion behaviour by solution nitriding. A special topic was to observe the effect of nitrogen by different molybdenum content. So austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.06 to 3.6%) had been solution nitrided. The samples could be prepared with various surface content of nitrogen from 0.04 to 0.45% with a step-by-step grinding. The susceptibility against pitting corrosion of these samples had been tested by determination of the stable pitting potential in 0.5M and 1M NaCl at 25℃. For the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen. The influence of nitrogen to all of the determined parameters can be described well by PRE = Cr 3.3 * Mo 25 *N. XPS analysis of the sample surfaces support the results of the pitting corrosion tests.Additionally surface investigations with an acid elektolyte (0.1M HCl 0.4M NaCl) were performed. In this case the passivation effective nitrogen content increases markedly with rising molybdenum concentration of the steel.Obviously an interaction of Mo and N is connected with a strongly acid electrolyte.     

核级316NG控氮奥氏体不锈钢的局部腐蚀行为

采用电化学测试法、点腐蚀试验法、盐雾腐蚀试验法和慢应变速率测试法,分别对比研究了核级316NG控氮奥氏体不锈钢和321奥氏体不锈钢的局部腐蚀行为,并利用扫描电子显微镜、光学显微镜等分别观察腐蚀后不锈钢的表面形貌。结果表明:316NG和321不锈钢晶间腐蚀再活化率分别为3.83%和4.47%,点腐蚀速率分别为10.74g/(m2·h)和45.97g/(m2·h),盐雾腐蚀速率分别为2.14×10-2 g/(m2·h)和12.32×10-2 g/(m2·h),应力腐蚀开裂敏感指数分别为0.078和0.10;316NG不锈钢中N和Mo元素提高了其耐局部腐蚀性能,因此其耐局部腐蚀性能均优于核电站结构材料321不锈钢的。     

Microstructure and pitting corrosion of similar and dissimilar stainless steel welds

Abstract

Pitting Corrosion behaviour of similar and dissimilar metal welds of three classes of stainless steels, namely, austenitic stainless steel (AISI 304), ferritic stainless steel (AISI 430) and duplex stainless steel (AISI 2205), has been studied. Three regions of the weldment, i.e. fusion zone, heat affected zone and unaffected parent metal, were subjected to corrosion studies. Electron beam and friction welds have been compared. Optical, scanning electron microscopy and electron probe analysis were carried out to determine the mechanism of corrosion behaviour. Dissimilar metal electron beam welds of austenitic–ferritic (A–F), ferritic–duplex (F–D) and austenitic–duplex stainless steel (A–D) welds contained coarse grains which are predominantly equiaxed on austenitic and duplex stainless steel side while they were columnar on the ferritic stainless steel side. Microstructural features in the central region of dissimilar stainless steel friction welds exhibit fine equiaxed grains due to dynamic recrystallisation as a result of thermomechanical working during welding and is confined to ferritic stainless steel side in the case of A–F, D–F welds and duplex stainless steel side in the case of D–A welds. Beside this region bent and elongated grains were observed on ferritic stainless steel side in the case of A–F, D–F welds and duplex stainless steel side in the case of D–A welds. Interdiffusion of elements was significant in electron beam welding and insignificant in friction welds. Pitting corrosion has been observed to be predominantly confined to heat affected zone (HAZ) close to fusion boundary of ferritic stainless steel interface of A–F electron beam and D–F electron beam and friction weldments. The pitting resistance of stainless steel electron beam weldments was found to be lower than that of parent metal as a result of segregation and partitioning of alloying elements. In general, friction weldments exhibited better pitting corrosion resistance due to lower incidence of carbides in the microstructure.     

焊接氧化皮对奥氏体不锈钢孔蚀性能的影响

采用电化学测试技术,在NaCl介质中焊接氧化皮对3种奥氏体不锈钢的耐孔蚀性能进行了探讨.结果表明,有焊接氧化皮部位较比母材更易产生孔蚀,去除氧化皮则改善耐蚀性能.有焊接氧化皮的不锈钢耐孔蚀性能依NK1<316<304次序变劣.通过表面SIMS分析,发现焊接氧化皮合金表面贫乏铬,从而导致耐孔蚀性能下降.有焊接氧化皮NK1不锈钢耐孔蚀性能之所以优于304不锈钢,是由于表面膜中富集铜元素,并参与了成膜过程,改善了表面电化学行为,增强了表面膜抵抗侵蚀性离子破坏的能力.     

Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel and nickel base alloys

Abstract

Super austenitic stainless steels are often welded using high Mo, Ni base filler metals to maintain the corrosion resistance of the weld. An important aspect of this processing is the weld metal dilution level, which will control the composition and resultant corrosion resistance of the weld. In addition, the distribution of alloying elements within the weld will also significantly affect the corrosion resistance. Dissimilar metal welds between a super austenitic stainless steel (AL-6XN) and two Ni base alloys (IN625 and IN622) were characterised with respect to their dilution levels and microsegregation patterns. Single pass welds were produced over the entire dilution range using the gas tungsten arc welding process. Microstructural characterisation of the welds was conducted using light optical microscopy, scanning electron microscopy, and quantitative image analysis. Bulk and local chemical compositions were obtained through electron probe microanalysis. The quantitative chemical information was used to determine the partition coefficients k of the elements in each dissimilar weld. The dilution level was found to decrease as the ratio of volumetric filler metal feedrate to net arc power increased. Reasons for this behaviour are discussed in terms of the distribution of power required to melt the filler metal and base metal. In addition, the segregation potential of Mo and Nb was observed to increase (i.e. their k values decreased) as the Fe content of the weld increased. This effect is attributed to the decreased solubility of Mo and Nb in austenite with increasing Fe additions. Since the Fe content of the weld is controlled by dilution, which in turn is controlled by the welding parameters, the welding parameters have an indirect influence on the segregation potential of Mo and Nb. The results of the present work provide practical insight for corrosion control of welds in super austenitic stainless steels.     

节镍型不锈钢的耐腐蚀性能比较

通过3.5%NaCl溶液中动电位极化曲线测定和中性盐雾试验,对200系列奥氏体不锈钢和400系列铁素体不锈钢两类节镍型不锈钢与304不锈钢的耐腐蚀性能进行了对比研究。结果显示,400系列铁素体不锈钢的耐点蚀性能优于200系列奥氏体不锈钢,两种节镍型不锈钢的耐点蚀性能均不如304不锈钢好;200系列奥氏体不锈钢的耐均匀腐蚀性能最差,443不锈钢耐均匀腐蚀性能与304不锈钢相当,439不锈钢比304不锈钢耐均匀腐蚀性能稍差。201、202、304、439和443不锈钢在3.5%NaCl溶液中的点蚀电位分别为(vs.SCE)-32 mV、-22 mV、312mV、165 mV和227 mV,腐蚀速率分别为0.0071 mm/a、0.0062 mm/a、0.0026 mm/a、0.0038 mm/a和0.0024mm/a。     

Oberflächenbehandlung als Korrosionsschutzmaßnahme von nichtrostenden Stählen

Surface treatment as corrosion protection measure of stainless steels The pickling behaviour of several stainless austenitic steels and of one steel with ferritic/austenitic grain structure were investigated in pickling solutions of different compositions based on hydrofluoric acid. Because of uncertainties in practical applications, the influence of temperature, time and acid content on the mass loss is of high interest. In another series of experiments, aqueous solutions of citric acid were tested for their suitability as pickling chemicals for the materials X 6 CrNiTi 18 10 (AISI 321) and X 6 CrNiMoTi 17 12 2 (AISI 316 Ti). Finally, the pickling procedures based on nitric acid/hydrofluoric acid mixtures were compared with mechanical cleansing methods and with pickling procedures based on aqueous citric acid solutions as well, to elucidate their influence on the corrosion resistance of the treated materials. The valuation followed a pitting corrosion test in sodium chloride solutions of different concentrations after Herbsleb and Schwenk. Pickling with hydrofluoric acid solutions is superior to other cleansing procedures, if corrosive environments are present. The ecologically beneficial citric acid solutions are only able to remove the annealing colours from stainless steels.