Korrosionsprobleme in chlorhaltigen Medien: Lösungsmöglichkeiten durch einige nichtrostende Spezialstähle

Corrosion problems in chloride containing media: possible solution by some stainless special steels The increasing water pollution forces the chemical industry to use water with increasing chloride content for cooling and other purposes. This trend brings about increasing corrosion danger, in particular pitting, stress corrosion cracking and corrosion fatigue as well as crevice corrosion. The present paper deals with some steels characterized by resistance to these specific corrosion phenomena. A steel containing (%) 21 Cr., 7.5 Ni, 2.5 Mo, 1.5 Cu, to 2 Mn, to 1 Si and 0.06 C is particularly resistant to stress corrosion cracking. It contains 30 to 50% ferrite in an austenitic matrix. Even in Mg chloride solutions it may be kept under a load of 7 kg/mm² without stress corrosion occurring (with a steel of the 18 10 CrNiMo type the admissible load is only 2 kg/mm²). A steel containing (%) 25 Ni, 21 Cr, 4.5 Mo, 1.5 Cu, to 1 Si, to 2 Mn, and 0.02 C has a broad passivity range and is resistant to general corrosion in acid reducing media and phosphoric acid of all concentrations. A ferritic steel containing (%) 26 Cr. 1 Mo and minor additions of C, Mn, Si, Cu, Ni and nitrogen is resistant to stress corrosion cracking in neutral chloride solutions and general corrosion in oxidizing and neutral media, even against hydrogen sulfid and organic acids; it is beyond that lergely resistant to pitting in chloride solutions.     

合金元素对12SiMoVNb抗氢钢埋弧焊焊缝金属热裂纹敏感性的影响

本文用横向可变拘束裂纹试验法研究了合金元素对12SiMoVNb 钢埋弧焊焊缝金属热裂纹敏感性的影响,指出了Si、Nb、Ni 和Mo 提高焊缝金属热裂纹敏感性,Cr、W、V 等降低焊缝金属热裂纹敏感性.在试验基础上,提出了具有良好抗裂性的Cr-W 合金系统的焊丝,解决了该钢埋弧焊时的热裂纹问题.     

Stress corrosion cracking of bainite 0.3C‐1Cr‐1Mn‐1Si‐1Ni type steel in acid rain simulated solution

The effect of carbon content, heat treatment and surface treatment of high strength aircraft 0.3C‐1Cr‐1Mn‐1Si‐1Ni type steel on susceptibility to pitting corrosion, on hydrogen transport and on hydrogen embrittlement has been studied in acid rain simulated solution. Under open circuit conditions, susceptibility to stress corrosion cracking is associated with susceptibility to pitting corrosion and decreases with decreasing carbon content and at application of shot peening. Susceptibility to hydrogen embrittlement governed by hydrogen trapping is promoted by carbon segregation at boundaries of bainite laths and parent austenite grains. Decrease in the carbon content caused the decrease in hydrogen trapping resulting in increasing resistance to hydrogen embrittlement. Shot peening increased the trapping efficiency within the deformed layer, but the presence of the shot peened layer decreased the hydrogen flux entering the core and thus decreased the susceptibility of the core to hydrogen embrittlement. The shot peened low carbon steel, exhibiting mechanical properties required by the appropriate Standard and high resistance to stress corrosion cracking may be considered to replace the standard 0.3C‐1Cr‐1Mn‐1Si‐1Ni steel for the aircraft parts.     

Cr对钢耐海水腐蚀性的影响

获得了５种含铬低合金钢在海水中暴露１、２、４、８（７）年的腐蚀数据,讨论Ｃｒ对钢耐海水腐蚀的影响,铬钢的耐海水腐蚀性不仅与Ｃｒ的含量有关,还与其他复合合金元素有关。短期浸泡时,钢的耐海水腐蚀性随铬含量（无其他合金元素复合）增加而提高。长期浸泡,Ｃｒ对钢的耐海水腐蚀性有害,约１％Ｃｒ与Ｍｏ（－Ａｌ）复合对钢的耐海水腐蚀性的影响与Ｃｒ的影响没有左别大于２％Ｃｒ与Ｍｏ（－Ａｌ）复合大幅度提高钢在海水中短期浸泡的耐蚀性,并使耐蚀性逆转时间明显推迟.小于1%Cr与Mn-Cu、Cu-Si-V、Ni-Cu-Si、Ni-Mn等复合对钢的耐海水腐蚀性有害。     

低合金高强度抗应力腐蚀开裂海洋软管用钢的开发

通过合金成分设计,轧制、热处理工艺的探索,开发了低合金高强度海洋软管用钢,其屈服强度大于600 MPa且满足抗氢脆、抗氢致开裂、抗应力腐蚀开裂性能,并通过全浸腐蚀实验对该钢的海水腐蚀行为进行了研究。结果表明,采用低C、低Mn并复合添加耐蚀元素Cr、Mo和采用合理的热轧、冷轧、调质处理工艺,可获得满足抗应力腐蚀开裂性能的600 MPa级高强钢。耐蚀元素的添加使实验钢具有良好的耐海水腐蚀能力,腐蚀稳定状态下的平均年腐蚀速率为0.11 mm/a。     

Die Ermittlung der Beständigkeit gegen Spannungsrißkorrosion (SpRK) von hochlegierten Sonderstählen in chloridhaltigen wäßrigen Medien

Determination of resistance to stress corrosion cracking (SCC) of high-alloy special steels in chloride-containing aqueous media The 18 Cr 10 Ni(Mo) based stainless steels have been continually improved by raising the Cr, Ni and Mo contents. The behavior of these high-alloy steels towards SCC was determined in test media generally used in practice since the question of the resistance to stress corrosion cracking (SCC) had still remained unanswered to a large extent. SCC tests on U-bend samples in boiling 62% CaCl₂ solution showed a good differentiation depending on the Ni and Mo contents. With increasing Ni content, the susceptibility of special high-alloy steels to SCC is shifted towards longer service lives, alloys containing ≧ 42% by weight of Ni being resistant. High-Mo special alloy steels are more resistant to SCC than low-Mo special alloy steels. These results could be confirmed by tests carried out on circular cross section samples in boiling 62% CaCl₂ solution under constant load and potentiostatic control. The free corrosion potentials recorded for 25% Ni special alloy steel and Ni-based alloys are within the potentiostatically determined range of insusceptibility to SCC. The high-Mo special alloy steel X 2 NiCrMoCu 25 20 6 (1.4529) shows the same critical SCC potential on the anodic side as the Ni alloy NiCr21 Mo (2.4858). Superferrit X 1 CrNiMoNb 28 4 2 (1.4575) and austenitic ferritic steel X 2 CrNiMoN 22 5 (1.4462) showed that the SCC behavior was unsatisfactory in both tests as in the case of steel X 10 CrNiMoTi 18 10 (1.4571). Tests in boiling 4 m NaCl showed no SCC, not even under the aggrevated test conditions in the test set-up. The great influence of the oxygen content was demonstrated in tests carried out in the autoclave with defined oxygen and chloride concentrations. The resistance of the steels to SCC decreases under air-saturated conditions (8 … 10 ppm O₂) whereas the chloride concentration (200 and 2000 ppm Cl^?) does not exercise an important influence. U-bend samples should be given preference to Erichsen samples for SCC tests. SCC break characteristics could be determined metallographically and by scanning electron microscope.     

Effect of carbon,chromium, and nickel on the α ⇄ γ transformation and properties of Cr - Ni - Mo - V steels

The aim of the present investigation is to determine some regular features of alloying Cr - Ni - Mo - V steels for critical parts with allowance for the structure, hardenability, level of properties, and semibrittleness temperature. For this purpose the concentration of carbon in Cr - Ni - Mo - V steels was varied from 0.03 to 0.47%, chromium from 0 to 4%, and nickel from 0 to 5% at a constant concentration of the other elements (0.5% Mo, 0.6% Mn, 0.25% Si, -0. 1% V, 0.015% S, 0.012% P), and the cooling rate from the austenitization temperature was varied from 25 to 1000°C/h.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 7 – 9, March, 1996.     

Effect of nickel alloying on crevice corrosion resistance of stainless steels

The crevice corrosion behaviour of stainless steels containing 25 mass% Cr, 3 mass% Mo and various amounts of Ni was investigated in natural seawater. The results showed that ferritic steels containing nickel were more resistant to corrosion than both ferritic steels without nickel and austenitic steels. The superiority of the Ni bearing ferritic steel over the other steels was in close agreement with the depassivation pH of those steels in acidic chloride solutions. The results showed that the addition of Ni to ferritic steel was effective in decreasing the depassivation pH and the dissolution rate in acidic chloride solutions at crevices.     

EFFECT OF ALLOY ELEMENTS ON QUASIEQUILIBRIUM MICROSTRUCTURE IN Fe-Mn-Ni-Cr STEELS

The microstructures of Fe-Mn-Ni-Cr steels with medium carbon and the effect of alloy ele-ments on them have been investigated by means of X-ray diffraction quantitative phase ana-lyses,metallography and hardness tests.The volume fraction of martensite in steels quenchedat 1100℃ can be expressed as:f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)Based on this expression,the quasi-equilibrium microstructure diagram has been obtained.Itis shown that the effect of Mn on the austenite stability is greater than that of Ni.The equiva-lent [Ni]=2.104Mn+Ni and equivalent [Cr]=Cr+Mo+V.The driving force for martensite transformation at M_s point has been calculated to hedrastically decreased by element Mn.     

Korrosion von Stahl vom Typ 03Cr18Ni13Mo2,5 und 02Cr25Ni22Mo2N bei der Harnstoffsynthese

Corrosion of steels type 03Cr18Ni13Mo2.5 and 02Cr25Ni22Mo2N in urea processing environment Long-term corrosion tests with the steel types 03Cr18Ni3Mo2.5 having different chemical compositions and chemical purity, and 02Cr25Ni22Mo2N have been carried out for up to 112517 and 64 699 h, respectively, in the urea manufacture environment. According to the results the first steel is a suitable material of construction for the high pressure parts of urea plant, provided its chromium content is higher than 18%. This quality meets requirements of urea grade steels. The steel 02Cr25Ni22Mo2N is even more corrosion resistant, but its use may be critical because of the high nickel content. A mathematical model has been developed for the weight loss-time-dependence and the results have been extrapolated to up to 1.5 ·10⁵h.     

Stress-induced failure of high-strength steels in environments containing hydrogen sulphide

Abstract

The pre-cracked cantilever beam test is a sensitive means of evaluating the relative susceptibilities of different steels to stress-Induced failure in H₂S-containing environments. This, test indicated that a 12Ni 5Cr.3Mo maragmg stee1 is considerably more resistant to stress-induced crackining than the low-alloy steels 0Ni 1Cr 2Mo and 2Ni 1Cr 3Mo. For low-alloy steels with no applied potential the failure appears to be caused predominantly by hydrogen embrittlement. Impressed anodic or cathodic potentials have no effect on the time to Failure of low-alloy steels where as a zone of immunity exists for maraging steel with Impressed potentials Within the approximate range ?0·6 to ?1·0 V. This suggests that the maraging steel is less susceptible to hydrogen embrittlement than the quenched and tempered low-alloy steels. Permeability studies indicate that stress-induced failure is related to the ability of the steel to transmit hydrogen and to the nature of hydrogen traps in the steel.     

Eigenschaften des schweißbaren,hoch korrosionsbeständigen Stahles X 2CrNiMoN 25 22

Properties of the weldable and corrosion resistant steel X 2 CrNiMoN 25 22 In view of the limited application of con- ventional CrNiMo steels the authors have investigated potential applications of the above mentioned steel. An optimum com- position would be (%) 0.02 C, 25Cr, 22 Ni, 2 Mo and 0.1 N. The low carbon content is a vital factor and the nickel content must not exceed 22% because higher contents would give rise to very pronounced precipitation. The new steel ist largely resistance to boil- ing nitric acid it is considerably superior to conventional steels, The high break-through potential is indicative of high pitting resist- ance. Improvements are equally remarkable with respect to mecanical properties and weldability     

Corrosion behavior of nickel alloys in wet hydrofluoric acid

Wet hydrofluoric acid at concentrations below approximately 60% is highly corrosive to glass, reactive metals, carbon steel and stainless steels. Nickel alloys offer moderate corrosion resistance over a wide range of acid concentration and temperature. The corrosion behavior of eleven commercial alloys was quantified through laboratory testing. Variables that were studied included testing time, acid concentration, temperature, vapor and liquid phases and the presence of residual stresses. Results show that the corrosion rate of a Ni‐Cu and a Ni‐Cr‐Mo‐Cu alloy increased with the acid concentration and the temperature. However, both for increasing acid concentration and temperature, the corrosion rate of the Ni‐Cu alloy increased faster than the corrosion rate of the Ni‐Cr‐Mo‐Cu alloy, especially in the vapor phase. Even in unstressed coupons, nickel alloys showed internal penetration in presence of wet HF; the mode of this internal penetration varied from alloy to alloy. Considering all the studied variables that influence corrosion, the highest ranked material for wet HF service was a Ni‐Cr‐Mo‐Cu alloy.     

MICRODISTRIBUTION OF Ce IN CERTAIN STEELS AND Fe-Cr-Al ALLOY

测定了铸态16Mn,25MnTiB,Cr24NiTSi2N以及FeCrAl中的稀上合金化量。涂敷法自射线照相结果表明,在16Mn与25MnTiB中,分布于珠光体中的Ce比分布于铁素体中的Ce多。在FeCrAl耐热合金与Cr24NiTSi2N耐热钢中,当稀土含量高时,则稀土元素在晶界有明显的富集;在FeCrAl的不同晶粒内稀土的含量不同,具有微观的不均匀性。     

Hitzebeständigkeit von Schweißverbindungen ferritischer Chromstähle

Heat resistance of welds in ferritic chromium steels With a view to the suitability of steels for use at temperatures up to 1000 °C various alloyed steels have been investigated. The results yield the conclusion that the following maximum working temperatures can be considered: 13% Cr steel 800 °C; 13% Cr steel with 2% Si an 0.8% Al 900 °C; 24% Cr steel with Si 1000 °C. The filler material can be an identical alloy having about the same Cr content. In the case of the high chromium steel a filler material containing 16% Cr and 36% Ni can be used as well, because the resulting weld has more suitable thermal dilatation properties. As to the after treatment of the weld seam it is indispensable to keep to a certain set of conditions, in particular during cooling, in order to prevent undesirable structural transformations.     

Cu基钎料MIG钎焊接头断裂行为分析

研究用Cu3SilMn钎料、Cu10Mn6Ni钎料分别MIG钎焊镀锌Q235钢板及1Cr18Ni9Ti不锈钢板。试验结果表明,在钎料／母材界面分别存在Si、Mn富集带,经XRD分析Si是以Fe2Si相形式存在,而Mn是以固溶体形式存在;用Cu3SilMn、Cu10Mn6Ni钎料钎焊镀锌Q235钢板接头抗拉强度试样均断在母材,抗拉强度为308．2－308．7MPa,钎焊1Cr18Ni9Ti不锈钢板,拉伸均断在钎缝,其抗拉强度分别是331．5MPa、423．6MPa;拉伸断口分析发现,断裂起裂点在搭接钎缝的根部,主要是母材成分与少量的钎料成分混合、溶解而成,是脆性断口;止裂点在钎缝金属中（Cu3SilMn钎料）或在近界面上（Cu10Mn6Ni钎料）,是塑性断口。     

合金元素对钢在海水飞溅区腐蚀的影响

讨论了合金元素对钢在海水飞溅区腐蚀的影响。合金元素在青岛、厦门和榆林海域对钢在海水飞溅区的腐蚀有基本相同的影响效果。Mn、P、Si、Cr、Mo和Ni能减轻钢在飞溅区的腐蚀,其影响大小的顺序为：P＞Si＞Cr和Mo＞Ni和Mn;S、Al、V对钢的飞溅区腐蚀有害。Cu-P、Mn-Mo、Ni-Cr-Mo复合对减轻钢在飞溅区的腐蚀有好的效果。     

激光熔覆Ni-Si金属硅化物复合材料涂层显微组织与耐蚀性

以Ni,Si,Cr元素粉末为原料 ,利用激光熔覆技术在A3钢表面制得了Ni Si金属硅化物复合材料涂层。分析了该涂层的显微组织 ,采用测定阳极极化曲线的方法评价了该涂层在 0 .5mol/LH2 SO4 及 3 .5 %NaCl水溶液中的耐蚀性能。结果表明 :激光熔覆Ni Si金属硅化物复合材料涂层组织由Ni2 Si初生胞状树枝晶及枝晶间少量FeNi/Ni31Si12 共晶组成 ,涂层表面平整、组织细小、与基体间为完全冶金结合 ;涂层组织显微硬度在HV80 0～ 95 0之间且沿层深分布均匀 ;由于涂层组织组成相Ni2 Si和Ni31Si12 等本身均具有很好的耐蚀性并具有快速凝固细小均匀的显微组织 ,激光熔覆Ni Si金属硅化物复合材料涂层在 0 .5mol/LH2 SO4 及 3.5 %NaCl水溶液中均表现出优良的耐蚀性能。激光熔覆Ni Si金属硅化物复合材料涂层可望成为一种很有发展前景的耐蚀涂层新材料。     

Korrosion in der Wärmeeinflußzone geschweißter chemisch beständiger Stähle und Legierungen und ihre Verhütung

Corrosion in the heat-affected zone of welds in chemically resistant steels and alloys, and respective preventive measures As to weldability, chemically resistant steels and alloys can be classified as follows: (1) weldable without any restriction; (2) weldable only with reduced wall thickness; (3) weldable only with ultimate thermal treatment. These restrictions are due to the precipitation of chromium carbide and intermetallic phases at the grain boundaries; this effect gives rise to a Cr and Mo depletion and, finally, to intercrystalline corrosion susceptibility. In view of the fact that weldability requires the delay of the precipitation of chromium carbides at 650°C for at least 1 hour, and of intermetallic phases at 900°C for at least 10 min it is possible to reduce the carbon content and/or to add stabilizing elements (Ti, Nb). It should be taken into account, however, that the precipitation behaviour is not a function of carbon concentration, but rather of carbon activity which, again, depends from the overall composition of the respective alloy. This activity is increased by Ni and Si, while Mn and N function as decelerators and, consequently, contribute to weldability. In the case of the steel X 3 CrNiMoN 17 13 5 the addition of N inhibits not only the carbide precipitation but also the precipitation of the Chi-phase (at 950°C). In the case of the alloy NiMo 16 Cr the gradual reduction of the contents of secondary constituents has resulted in a practically pure ternary system characterized by high precipitation resistance: carbides are precipitated only after 5 hours at 800°C.     

预置镍基合金片对异种钢UNGW接头组织及性能的影响

研究了预置镍基合金片对15CrMo/1Cr18Ni9Ti异种钢超窄间隙焊接接头组织及性能的影响。结果表明,预置镍基合金片厚度小于0.6 mm时,15CrMo熔合线附近焊缝区部分区域以A模式凝固并形成奥氏体胞状晶,而其它区域仍以FA模式凝固,其组织为等轴晶奥氏体+枝晶状铁素体,并且焊缝中心无凝固裂纹形成。预置0.9~1.2 mm厚的镍基合金片时,焊缝中心因镍偏聚而以A模式凝固,形成粗大的奥氏体柱状枝晶,并有凝固裂纹形成。预置镍基合金片厚度在0.6~0.9 mm时,可使15CrMo熔合线附近焊缝区的Ni质量分数比填充金属(ER347L)的提高约2%,明显比未预置镍基合金片的接头具有更好的抑制碳扩散效果,但当镍基合金片厚度在0.3~1.2 mm范围内变化时接头抑制碳扩散的效果并无明显变化。焊态的异种钢接头不均匀混合区内存在马氏体层,而热时效后在熔合线附近会形成一定宽度的富碳硬化区及贫碳软化区。