2205双相不锈钢与304奥氏体不锈钢的焊接

采用焊条电弧焊(SMAW),以E2209作填充材料对2205双相不锈钢与304奥氏体不锈钢异种金属焊接工艺进行研究,通过优化焊接工艺参数,获得了具有良好力学性能和合适双相比例的焊接接头.接头力学性能测试表明,拉伸试样断裂发生在强度相对较低的304母材侧;2205母材侧热影响区的显微硬度值高于焊缝和2205母材,而304...     

Repassivation studies on an austenitic stainless steel in chloride solutions

The repassivation behaviour of an 18Cr---10Ni steel strained in tension in room temperature solutions of pH 2 containing chloride ion concentrations of 0·01M, 0·1M and 1·0M has been studied as a function of strain and potential under potentiostatic conditions. After straining the current decays such that — log is constant and this is interpreted as arising from the summation of a series of transients. The charge flowing during the repassivation process has been calculated and varies considerably, increasing with increasing strain and chloride ion concentration and as the potential is made more noble.     

On the mechanism of ion nitriding of an austenitic stainless steel

The mechanism of nitrogen transport has been investigated in an austenitic stainless steel (AISI 304) under high flux and low energy nitrogen ion beam irradiation at moderate temperatures in the range 270–550°C. The profiles of the distribution of nitrogen have been analyzed with nuclear reaction analysis (NRA) and glow discharge optical spectroscopy (GDOS), and the surface roughness with scanning AFM. The modeling is based on the study of the stochastic mixing of atoms ‘ballistically’ displaced by incident ions. The development of surface roughness and the formation of an altered layer highly enriched by nitrogen are analyzed, and it is concluded that the transport of nitrogen into the bulk results from a flux of matrix atoms driven by mobile vacancies at temperatures above 350°C. This behavior is consistent with an altered layer ‘growth’ that is controlled by the ion-beam-induced displacements of surface atoms.     

奥氏体不锈钢的回复与再结晶机制

研究了奥氏体不锈钢经等通道转角挤压冷变形后在退火过程中的组织变化.具有低层错能的奥氏体不锈钢在退火过程中可以发生多边化过程;亚晶的形成与长大方式有:a)形变带→带内位错胞→亚晶;b)形变带→高密度位错形变带界面→多边化→位错墙→亚晶.亚晶以晶界凸出机制迁移生长以及合并机制生长.再结晶的形核与生长:亚晶的不断长大形成再结晶晶核,晶核以凸出机制迁移长大.凸出机制在微观上是台阶长大机制,合并机制从宏观上看是晶粒转动机制.这两种机制是亚晶长大与再结晶晶核生长的基本机制.     

Repassivation kinetics studies on an austenitic stainless steel in chloride media

A new technique consisting in scratching an electrode kept under a constant load has been developed to study the initial stages of repassivation (10–100 ms) of an austenitic stainless steel in various media (sulphate and chloride) following the rupture of the protective film. S.c.c. criteria have been proposed and particularly a critical potential called transition potential, E_trans. The charge densities passed during repassivation have been measured and the transition between pitting corrosion and stress corrosion cracking in chloride media is also discussed.     

Propagation of stress-corrosion cracks in austenitic stainless steel

Abstract

Sensitive (<50 Å) extension measurements on direct-loaded wires of a susceptible austenitic Cr–Ni steel have revealed no discontinuities during crack propagation although the fracture surfaces are generally striated on a scale of ～0· 2 μ. These results are taken as support for the continuous mechano-chemical theory of propagation and a detailed crack model is proposed.     

The influence of bromine on the gaseous oxidation of an austenitic stainless steel

The effects of bromine on the oxidation behaviour of an austenitic stainless steel have been studied in oxygen and a CO₂/10%CO mixture at 750°C and 1 atm total pressure. Supporting work has also been carried out on chromium and nickel with similar results. Bromine at 0·06 atm enhanced under certain circumstances the formation of oxide scale in oxygen, but led to the formation of volatile halides in the CO₂/CO mixture. The former effect was only obtained when the bromine was present at the commencement of oxidation, or preformed protective oxide films were fractured by thermal cycling.     

低合金钢与奥氏体不锈钢堆焊层的焊接工艺

低合金钢与不锈钢堆焊层焊接时,因稀释反应、组织变化、内应力等,降低了焊接接头质量。通过试验对异种金属焊接接头力学性能和金相组织进行分析和验证,总结工艺上所存在的问题以及长时间热处理对此类焊接接头的影响。     

Effects of sulfur pressure on the sulfidation behavior of 310 stainless steel

High-temperature sulfidation behavior of 310 stainless steel was studied over the temperature range of 700–900°C above a pure sulfur pool with the sulfurvapor range of 10^–4–10^–1 atm. The corrosion kinetics followed the parabolic rate law in all cases. The corrosion rates increased with increasing temperature and sulfur pressure. The scales formed on 310 stainless steel were complex and multilayered. The outer scale consisted of iron sulfide (with dissolved Cr), (Fe, Ni)₉S₈ and chromium sulfides (Cr₂S₃ and Cr₃S₄ with dissolved Fe), while the inner layer was a heterophasic mixture of Cr₂S₃, Cr₃S₄, NiCr₂S₄, and Fe₁–_xS. Platinum markers were found to be located at the interface between the inner and outer scales, suggesting that the outer scale grew by the outward transport of cations (Fe, Ni, and Cr), and the inner scale grew by the inward transport of sulfur. The formation of Cr₂S₃, Cr₃S₄, and NiCr₂S₄ partly blocked the transport of iron through the inner scale, resulting in a reduction of the corrosion rates as compared with the results in the literature.     

Phase equilibria in the Al---Cr system

The Al---Cr system has been reviewed for Cr content up to 40 at.%. In this system several intermetallic compounds are formed by peritectic reactions. From the temperature of transformation and the composition of the phases, the nature of the invariant transformations is discussed. Transmission electron microscopy studies were performed on samples forming these compounds. A detailed structural interpretation is given for the phase θ-Al₇Cr. A new structure is proposed for Al₄Cr similar to that of the μ-Al₄Mn phase of which the crystal structure is known. The phase Al₅Cr (or Al₁₁Cr₂) was found to be orthorhombic and not monoclinic, as had been previously proposed. The existence of a cubic structure for the Al₉Cr₄ phase was confirmed.

On account of previous results, we should point out that the phases θ-Al₇Cr, Al₄Cr and Al₅Cr present characteristic features of pseudoicosahedral symmetry of the Al₄Cr icosahedral phase: it has been verified in the case of θ and μ that the same type of atomic cluster may be considered in order to describe these structures, i.e. 12 atoms located at the vertices of deformed icosahedra (either 12Al or 11Al + 1Cr or 10Al + 2Cr) whose centres are occupied by a Cr atom.

The reason for such an investigation originated from a study of the Al---Cr---Ni system for which the observed ternary structures appeared incoherent with those given for the binary Al---Cr system. This second study will be reported elsewhere.     

The air oxidation of an austenitic Fe-Mn-Cr stainless steel for fusion-reactor applications

The oxidation in air of an austenitic Fe-Mn-Cr steel containing 17.8 Mn, 9.5 Cr, 1.0 Ni, 0.27 C, and 0.03 N was studied over the range 700–1000°C. Oxidation of surface-abraded samples at low temperatures, 700–750°C, resulted in only Mn ₂O₃ containing dissolved chromium, except at corners, where large nodules containing spinel and manganowustite formed. The Mn₂O₃ layer grew into the substrate forming a globular-type film. This growth mode was the result of slow interdiffusion in the alloy after the cold-worked surface layer had been recrystallized and/or consumed, as evidenced by the formation of a ferrite layer subjacent to the scale and by the instability of the planar interface. No internal oxidation was observed beneath the Mn₂O₃ film at either 700 or 750°C. Samples oxidized in thehigh-temperature region, 800–1000°C, exhibited vastly different behavior, forming thick stratified scales at long times (24 hr), the scales consisting of a very thin outer layer of Mn₂O₃ (with appreciable iron in solution), Fe-Mn spinel beneath the outer layer, and a thick inner layer of manganowustite and a chromium-containing spinel. No chromium was found in the outer two layers. A thin layer of nearly pure Fe₂O₃ formed between Mn₂O₃ and the outer spinel. Quasiparabolic kinetics were observed. The high-temperature rates were about 10³ to 10⁴ times greater than at low temperatures at the transition temperature. The rapid rates at high temperatures were attributed to manganowustite growth. However, oxidation of an electropolished sample at 750°C, from which the superficial cold-worked layer had been removed, formed scales similar to those observed at high temperatures at comparable rates. A difference by a factor of over 10⁴ existed between the oxidation rate of the electropolished sample and the surface-abraded sample at 750°C. The much slower oxidation rate of the latter is attributed to greatly enchanced manganese diffusion through the high dislocation-density, cold-worked layer. Short-time tests at 800°C revealed an incubation period during which a thin protective layer of Mn²O₃ formed. The incubation period corresponded to the recrystallization time of the cold-worked layer. Subsequently, nodular growth occurred which was associated with internal oxidation. The nodules, consisting of spinel and manganowustite, eventually linked up to form a thick, stratified scale. Comparison of the scale structures with calculated phase diagrams of composition versus oxygen activity (at constant temperature), showed that the protective films formed at low temperatures were due to kinetics factors, involving enhanced manganese diffusion through the cold-worked layer, rather than to thermodynamics. A model for the breakdown of protective films is proposed which involves internal oxidation.     

奥氏体不锈钢应力腐蚀分析研究

详细论述了奥氏体不锈钢应力腐蚀断裂发生的条件、特征、原因和解决方法，为分析和解决奥氏体不锈钢应力腐蚀失效的问题提供了重要依据。     

奥氏体不锈钢焊条在修复实践中的局限性

奥氏体不锈钢焊条在工程修复中有着广泛的应用。人们利用奥氏体不钢锈焊条的良好工艺性能。在大大小小的工件缺陷（尤其是裂纹类缺陷）修复中取得了良好的工艺效果和经济效益。然而通过多年的工件修复实践,认识到对这种焊条的应用也要一分为二地对待。本文通过实例指出奥氏体不锈钢焊条在工件修复中的局限性,提出了在一定条件下应将采用过该种焊条施焊的焊缝作为缺陷对待的理由。     

含铜超级奥氏体不锈钢的固溶行为

通过Thermo-Calc热力学计算软件制定含Cu超级奥氏体不锈钢的固溶处理温度为1000~1200 ℃,保温60 min。通过光学显微镜、SEM与EDS研究了固溶温度对含Cu超级奥氏体不锈钢显微组织、析出相和夹杂物的影响,研究结果发现Cu能促进试验钢的再结晶及析出相的溶解,在1000 ℃以上固溶处理时析出相均为σ相。试验钢的夹杂物类型主要是镁铝氧化物和硫化物。确定1200 ℃为微Cu试验钢的最佳固溶处理温度。     

Developing an austenitic stainless steel for improved performance in advanced fossil power facilities

Designed for application in the demanding environments of power-generating systems, new steels with outstanding high-temperature creep rupture resistance have been developed at Oak Ridge National Laboratory. Stemming from years of research on precipitation in aged and reactor-irradiated steels, the precipitate microstructure in Fe-Cr-Ni steels was effectively tailored through carefully controlled additions of minor alloying elements and with the assistance of analytical electron microscopy.     

High corrosion resistance of austenitic stainless steel alloyed with nitrogen in an acid solution

Passivity of austenitic stainless steel containing nitrogen (ASS N25) was investigated in comparison with AISI 316L in deareated acid solution, pH 0.4. A peculiar nature of the passivation peak in a potentiodynamic curve and the kinetic parameters of formation and growth of the oxide film have been discussed. The electronic-semiconducting properties of the passive films have been correlated with their corrosion resistance. Alloying austenitic stainless steel with nitrogen increases its microstructure homogeneity and decreases the concentration of charge carriers, which beneficially affects the protecting and electronic properties of the passive oxide film.     

Martensitic transformation in an intergranular corrosion area of austenitic stainless steel during thermal cycling

An oxidation-assisted martensitic phase transformation was observed in an austenitic stainless steel after thermal cycling up to 970 °C in air in a solar thermal steam reformer. The intergranular corrosion areas were investigated by electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). The structural-and-chemical maps revealed that within intergranular corrosion areas this martensitic transformation primarily occurs in oxidation-induced chromium-depleted zones, rather than due to only sensitization. This displacive transformation may also play a significant role in the rate at which intergranular corrosion takes place.     

奥氏体不锈钢变薄拉深过程的数值模拟

利用有限元软件Deform-2D,对奥氏体不锈钢变薄拉深过程进行热力耦合的数值模拟,研究了凸、凹模与坯料间摩擦和变形速度对变薄拉深过程的成形载荷和坯料损伤的影响。模拟结果显示：当凹模与坯料之间的摩擦增大,成形载荷和坯料损伤明显增大;当变形速度增大,坯料损伤增大而成形载荷减小。上述结论为奥氏体不锈钢变薄拉深工艺优化设计提供了可靠的理论依据。