High-strength austenitic stainless steel

Based on the studies of carbon and nitrogen effects on the electron structure, short-range atomic order, and thermodynamic stability of iron solid solutions, a physical concept for alloying steels with carbon and nitrogen is proposed. The concept is used for the design of a cost-effective austenitic corrosion-resistant steel of super-high strength and fracture toughness.     

Hydrogen transport in austenitic stainless steel

The permeability, diffusivity, and solubility of hydrogen in austenitic stainless steels were determined by analysing the time-temperature dependence of deuterium flux through foil specimens. For a variety of such steels, the temperature dependence of these transport properties is given by: .These equations lie within the range of reported values. Much of the scatter between the results of previous investigators probably resulted from surface control of permeation. Surface effects were minimized in the current study; therefore, the above equations should approximate diffusion-controlled hydrogen transport.     

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...     

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.     

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.     

奥氏体不锈钢焊接磁性控制

我厂承制的HT - 7U超导托卡马克核聚变试验装置工程是中科院等离子所国家级科研项目 ,其中的内冷屏、外冷屏及冷屏颈管 ,母材为 30 4L ,设计要求焊后焊缝磁导率小于 1.1。通过试验测得奥氏体不锈钢焊接后磁导率大于 1.2 ,根本不能保证产品设计要求。而奥氏体不锈钢通常没有磁性 ,但经过冷作加工后可在钢内析出少量铁素体或马氏体的组织 ,会出现磁性。通常奥氏体不锈钢焊后 ,其焊缝组织为奥氏体 +铁素体双相组织 ,当焊缝中铁素体组织含量增加时 ,其磁性将随之提高。目前国外只有几家焊材生产厂家生产无磁性焊材 ,国内只有个别厂家针对母材…     

304奥氏体不锈钢热诱发马氏体相变研究

借助X射线衍射技术,研究了304奥氏体不锈钢热诱发马氏体相变倾向.结果表明:C、Mn、Cr和Ni接近标准规范下限,304不锈钢的稳定性急剧下降,致使液氮内冷却后接近1/3的奥氏体转变为α'或ε马氏体,室温拉伸即形成应变诱发ε和α'马氏体,而且较小的室温变形显著增大随后液氮内冷却的热诱发α'马氏体相变倾向,但随室温预应变增大快速形成应变诱发α'马氏体,致使随后在液氮内发生热诱发α'马氏体倾向下降.此外,研究表明ε马氏体的形成及消失与α'马氏体的累积量有关.     

Laser surface hardening of austenitic stainless steel

For the purpose of studying the possibilities of increasing the wear resistance, keeping a high level of corrosion strength, austenitic stainless steel specimens mainly containing 19.2%Cr and 9.4%Ni were two-step surface alloyed using added materials (AMs) with hard particles of carbides (WC), nitrides (TiN), and borides (TiB₂). The simultaneous melting of AM and surface layer was performed by a CO₂ continuous wave laser on a numerically controlled X-Y table. On these specimens, the microstructural characteristics, microhardness, and depth of the molten zone were determined, which allowed definition of the AM with the best hardening effect. The research continued by two-step laser surface alloying of the same base material with different effective AM quantities. The specimens were processed by continuous wave laser radiation, by multiple-pass with 35% overlap. The alloyed layers were described by light optical microscopy, x-ray diffractometry, flash spectrometry, and hardness measurement. The conditions to obtain compact surface layers with 2.5 to 3 times higher hardness than the base material were determined.     

Pitting of austenitic stainless steel clad metals

Austenitic stainless steel welds with different ferrite contents (4 and 12 FN) were obtained by the Submerged Arc Welding (SAW) strip cladding process, and some clads were remelted by TIG. The welds were post weld heat treated (PWHT) at 600, 800, 1000°C for 1 h. Pitting potentials were measured in 1 N H₂SO₄ + 0.5 N NaCl. Etching at the pitting potentials was carried out in the same solution in order to locate the pit sites; pitting studies were also conducted in 10% FeCl₃ solution. The results showed that an increase in ferrite content decreases pitting resistance. PWHT at 800°C decreases pitting resistance, too, whereas PWHT at 1000°C results in increased pitting resistance at austenite/ferrite interfaces. TIG samples showed less pits than their SAW counterparts.     

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。     

超级奥氏体不锈钢254SMO的焊接

根据工程实践,详细介绍了254SMO钢与焊接有关的各种性能,包括成形、加工、接头设计、表面和坡口的清理等,并着重介绍了焊接工艺要点。     

Grain-boundary structure and precipitation in sensitized austenitic stainless steel

Grain-boundary carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy to clarify the effect of grain-boundary structure on precipitation and corrosion. The propensity to intergranular precipitation depends strongly on the grain-boundary structure. Carbide precipitates tend to be detected at grain boundaries with higher Σ values or larger deviation angles (Δθ) from low-Σ coincidence site lattice misorientations. The more ordered boundary requires a longer time for intergranular carbide precipitation and corrosion than less ordered or random boundaries. For more information, contact Hiroyuki Kokawa, Aoba-yama 02, Sendai 980-8579, Japan; telephone 81-(22)-217-7351; fax 81-(22)-217-7351; e-mail kokawa@material.tohoku.ac.jp.     

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。     

Carbide precipitation in austenitic stainless steel carburized at low temperature

Low-temperature gas-phase carburization can significantly improve the surface mechanical properties and corrosion resistance of austenitic stainless steel by generating a single-phase “case” with concentrations of interstitially dissolved carbon exceeding the equilibrium solubility limit by orders of magnitude. Upon prolonged treatment, however, carbides (mostly χ, M₅C₂) can precipitate and degrade the properties. High-resolution and spatially resolved analytical transmission electron microscopy revealed the precise carbide–austenite orientation relationship, a highly coherent interface, and that precipitation only occurs when (i) the carbon-induced lattice expansion of the austenite has reached a level that substantially reduces volume-misfit stress and (ii) diffusional transport of nickel, chromium, and iron – enhanced by structural defects – can locally reduce the nickel concentration to the solubility limit of nickel in χ-carbide.     

304奥氏体不锈钢应变诱发马氏体的研究

用X射线衍射(XRD)、磁针法、力学性能和显微分析研究了商用热轧态和冷轧态304奥氏体不锈钢在不同变形方式下应变诱发马氏体的行为。结果表明:304钢热轧态由于存在多量碳化物和组织不均匀性,其奥氏体稳定性低,拉伸应变诱发马氏体量达40%,冷轧(固溶)态组织均匀、奥氏体稳定性高,拉伸应变诱发马氏体量仅9%;304冷轧板材扩孔、杯突成形时其切向和径向的二向拉应力有助于γ→α’转变,诱发马氏体量(30%～35%)多于单向拉应力的拉伸诱发马氏体量(8%～10%)。对于冷轧304不锈钢,在20%以上拉伸工程应变的驱动下才能较明显地诱发马氏体。304明显的强化效果(△σ达320～400 MPa)来自应变硬化和马氏体相变强化两方面:冷轧304钢的强化主要来自应变硬化本身;热轧304钢的强化不光有应变硬化的贡献,还有应变诱发的多量马氏体的重要贡献,而且后者是主要的。     

奥氏体不锈钢焊接接头在含硫介质中的腐蚀性

利用恒电位极化曲线法及金相显微分析方法,研究了奥氏体不锈钢手弧焊焊接接头在含Na2S溶液中的腐蚀行为.结果表明,采用A102焊条的焊缝,其耐蚀性优于A307焊条焊缝;20℃条件下,Na2S质量分数的增加加速腐蚀反应的阴、阳极过程;在Na2S质量分数一定的条件下,温度升高到80℃时,在阳极极化区有钝化现象.     

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。