双相不锈钢的发展现状及未来市场趋势

从不同角度叙述双相不锈钢发展史,介绍合金设计,以及过去和现有的合金牌号。讨论了合金设计的基本原则,介绍了新的双相不锈钢。对于双相不锈钢的主要性能,也作了介绍,并着重强调其在新的应用领域具有极大的增长潜力。从所提供的数据中,也引伸出一些开放性的课题。这些课题将进一步推进2010年在法国博恩(Beaune)举办的双相不锈钢大会上的研讨。     

双相沉淀硬化粉冶不锈钢的开发

不锈钢可通过压制与烧结水雾化粉末来制取.粉冶品级的不锈钢有铁素体、奥氏体、马氏体、两相(铁素体+奥氏体)、双相(铁素体+马氏体)以及沉淀硬化(马氏体)等不锈钢.开发双相粉冶不锈钢反映了对较高强度、较高延性与韧性的需求在增长.在本研究中,开发出一种新的低成本粉冶不锈钢,它将双相(铁素体+马氏体)显微结构与沉淀硬化的优点结合在一起.它与其他沉淀硬化合金不同,尽管这种不锈钢在时效后强度与韧性有所提高,但延性与冲击韧度的提高更大.借助组成与显微结构评估了新合金的力学性能.     

耐海水腐蚀高压气阀研制

摘要：以含25％Cr的双相不锈钢和镍基高温合金为主体材料制成了25MPa高压气阀，解决了因耐压性能提高而造成的气阀体积放大问题；测试了阀件的液压密封性能和气压密封性能，耐1000次开启及关闭的疲劳性能，以及双相不锈钢和镍基高温合金同镍黄铜或铝青铜等材料组合使用的接触腐蚀性能；结果表明，气阀材料具有良好的耐海水腐蚀性能，在35℃的人造海水(3．5％的Nacl水溶液)中腐蚀失重率仅为0．002-0．005∥m^2·hr，接触腐蚀的影响也不明显。选用双相不锈钢和镍基高温合金材料制作高压气阀为设计具有更高耐压性能的阀件提供了一种新的途径。     

热处理工艺对SAF2205和SAF2304不锈钢晶间腐蚀和孔蚀的影响

双相不锈钢是铁、铬、镍的合金，其室温组织通常为50％的奥氏体和50％的铁素体。双相不锈钢同时具有高强度和耐腐蚀性能，而这是普通单相奥氏体或铁素体不锈钢所不具备的。与奥氏体不锈钢相比，双相不锈钢具有更好的耐局部和应力腐蚀的性能，尤其是在含氯离子的热腐蚀环境中。与铁素体不锈钢相比，双相不锈钢具有更好的成型性能、焊接性能及韧性。正是由于这些优良性能，双相不锈钢被越来越多地应用于海洋环境、石化工业和石油提炼业。尽管双相不锈钢早在20世纪30年代就已被开发出来，但直到高合金双相不锈钢的出现才使其得到广泛应用。这是因为早期的双相不锈钢难于进行热加工并且经焊接和热处理后易发生晶间腐蚀。     

经济型双相不锈钢的研发进展

 经济型双相不锈钢是一种高性能低成本的氮合金化不锈钢新材料,具有典型的铁素体-奥氏体双相组织。利用氮取代镍元素的奥氏体化作用,降低成本的同时获得优良的力学性能和耐腐蚀性能。介绍了经济型双相不锈钢的发展历史,重点讨论了合金元素和热处理对相变、力学性能和耐腐蚀性能的影响规律,并与304和316进行对比;同时,分析了经济型双相不锈钢焊接性能和焊接工艺的研究进展。经济型双相不锈钢S32101、S32003、S32202等,已用于核电、桥梁、建筑、热交换器等行业,取代传统奥氏体不锈钢AISI 304和316。由于经济型双相不锈钢具有高强度和优良耐蚀性,同时镍、钼等贵金属的含量都较低,已成为未来不锈钢发展的方向之一。     

特超级双相不锈钢的发展现状及趋势

概述了世界范围内特超级双相不锈钢的发展现状及趋势,重点对特超级双相不锈钢的成分设计思路、组织特点进行了分析,并结合其性能优势介绍了国外在相关领域的应用范例。强度更高、耐蚀性能更优的特超级双相不锈钢正在成为新一代的双相不锈钢材料,其将在海洋工程、石油石化、化工等领域获得广泛的应用。     

面对压力知难而进——访雪佛龙能源技术公司Richard Thompson先生

“雪佛龙普遍采用价格较低的合金，耐蚀材料，我们主要用中档合金”Richard解释说。“奥氏体不锈钢，超级双相不锈钢和22Cr双相不锈钢目前的用途越来越广。资源节约型双相合金是一种新型材料，     

节约型双相不锈钢组织性能控制与制造技术

节约型双相不锈钢在提高强度、改善韧性、耐蚀性能及焊接性能等方面具有突出优点,可望广泛应用于核电、石化、造船、造纸、海水淡化等领域,成为一种性能优良又节约资源的结构材料。但是,由于缺乏对其热加工特性及合理加工工艺全面深入的了解,还未能实现大规模工业化生产节约型双相不锈钢。针对节约型双相不锈钢热塑性更差、热加工制备更困难等关键问题,分析了合金成分设计、热变形行为与热塑性控制、微观显微组织演变、热加工安全区预测及脆性相析出动力学规律等的研究进展,指出了突破节约型双相不锈钢工业化生产的关键工艺技术方向。     

双相不锈钢的开发和应用现状

本文综述了双相不锈钢的开发和应用现状。介绍了新发展的含氮双相不锈钢和粉末冶金双相不锈钢,还叙述了双相不锈钢在改善热加工性方面,以及晶粒细化和超塑性化等方面的概况。     

高强度及超高强度双相不锈钢线材的应用

1前言 如今在许多领域中双相不锈钢被视为经久耐用的代名词。这主要是南于双相不锈钢兼具高强度、高塑性和优异的耐蚀性能。同溶条件下的双相不锈钢其强度约为奥氏体不锈钢的两倍。SAF2205是一种传统中等合金含量的双相不锈钢，具有高的耐蚀、力学性能和良好的焊接性能。SAF2205和其他2205型双相钢牌号之间的不同在于SAF2205成分控制范围更窄。     

超级双相不锈钢生产工艺实践

超级双相不锈钢S32760生产工艺流程为20tEAF→AOD→LF→30cm模铸。由于S32760成分设计中高铬、低磷、低硫、超低碳这一特点,冶炼后期钢水过氧化程度严重。为改善钢水洁净度、降低钢中氧质量分数,通过采取合理的脱氧造渣工艺,采用Al-Si-Ca复合脱氧,使钢中气体、夹杂物得到了有效控制,改善了钢水洁净度,成品钢中硫质量分数控制在0.002%以下,氧质量分数控制在0.004%以下。     

High density sintering of duplex stainless steels

Abstract

Duplex stainless steels prepared from mixes of elemental powders with martensitic 410L steel have been shown to possess stable dual phase microstructures. Following heat treatment, the steels possess good mechanical properties. The addition of boron as a sintering aid reduces compressibility but promotes densification through transient liquid phase sintering; its effect on corrosion resistance is particularly favourable.     

Vena cava duplex imaging before caval interruption

PURPOSE: Venacavograms are routinely obtained before vena cava filter placement to evaluate cava size, patency, and the presence of thrombus or venous anomalies. The objective of this study was to determine the ability of duplex ultrasonography to adequately evaluate the inferior vena cava (IVC) for size, patency, and the presence of thrombus before Greenfield filter (GF) insertion. METHODS: Duplex ultrasonographic scans were performed in 40 patients who had documented lower-extremity deep venous thrombosis diagnosed by duplex scan before GF placement. The infrarenal transverse and anteroposterior diameters of the IVC were measured, and the entire IVC was imaged for patency and the presence of thrombus or anomalies. Preoperative venacavograms were not obtained in any patients who had GFs placed in the operating room, but was performed during surgery during filter insertion. An additional 26 patients who had deep venous thrombosis and did not have caval interruption underwent IVC duplex to determine the patency and proximal extent of venous thrombosis. RESULTS: The indications for GF placement were contraindication to anticoagulation in 72.5% (29 patients); five filters were placed prophylactically; three for failure of anticoagulation; two after a complication of anticoagulation; and one before pulmonary embolectomy. The filters were placed in the operating room by surgeons in 82.5% of patients, with the remainder inserted in an angiography suite by an interventional radiologist. The ability of duplex to measure a transverse diameter of 26 mm or less had a sensitivity of 97.5%, positive predictive value of 100%, and overall accuracy of 97.5% using venacavography as the standard. Measurements of IVC diameter by duplex correlated with those based on venacavograms (r = 0.766; p < 0.001). Of the entire group of 66 IVC duplex examinations, one (1.5%) was incomplete because of technical limitations. IVC thrombus was noted by duplex in two patients who underwent GF insertion, which was confirmed with venacavography. No IVC anomalies were noted by duplex scans or venacavograms. CONCLUSION: Duplex ultrasonography is a useful and accurate method for assessment of the IVC before vena cava filter placement.     

Lowcycle fatigue behavior on duplex stainless steels

Stainless steels are used predominantly for their corrosion resistance in moderate to highly aggressive environments. For construction purposes, engineers normally select carbon steel due to low cost, long experience, applicable design rules and a large variety of strength classes. However, different stainless steel types can also provide a very wide range of mechanical properties and they have the advantage of not needing surface protection. Duplex Stainless Steels (DSSs) in particular, are austeno-ferritic steels with twice the mechanical strength of conventional austenitic and ferritic stainless steels and have a potential use in construction. In the early 1980’s, a ‘second generation’ of duplex steels was introduced with better weldability mainly through nitrogen alloying. The most common duplex grade today is the UNS S32205/S31803, which is used in a great number of applications in a wide variety of product forms. This grade was the basis for the development of a ‘third generation’ of duplex steels. These higher alloys are called super-duplex stainless steels and identified as UNS S32750/S32760. The cyclic hardening-softening response, the cyclic stress-strain curve and the microstructure evolution of a high nitrogen duplex stainless steel S32750 have been evaluated and the results compared with reference to low and medium nitrogen duplex stainless steels, S32205 and S32900 grades, respectively. The beneficial effects of nitrogen on the cyclic properties of most modern alloys have been analyzed in terms of the flow stress components, i.e. the back and the friction stress. A phenomenological model is proposed to explain the influence of nitrogen atoms on the cyclic behavior of these steels.     

Metastable precipitate in a duplex martensite +

The crystal structure and chemical composition of the strengthening precipitates in an Fe- 11.8 pct Cr-8.5 pct Ni-1.8 pct Ti-3.8 pct Mo martensite + ferrite duplex steel were determined by transmission electron microscopy (TEM). The study revealed that a metastable precipitate phase formed in the ferrite and martensite phases during the initial stages of aging. The meta- stable phase was proposed to have a hexagonal crystal structure similar to that reported for the omega phase in Ti alloys. Prolonged aging formed an equilibrium orthorhombic precipitate phase with a Ni₃(Mo, Ti) stoichiometry. The higher dislocation density in martensite accelerated the precipitation reaction, and the transition to the equilibrium precipitate occurred with shorter aging times compared to ferrite. The details of the electron diffraction and analytical electron microscopy studies of the precipitates are described.     

Colour-coded duplex sonography of preocclusive carotid stenoses

Gene replacement therapy is potentially a very powerful tool, targeting specific molecular mediators of cancer development and progression. p21WAF1 (p21) is a cyclin-dependent kinase inhibitor that is induced by p53 upon DNA damage or p53 overexpression, resulting in cell cycle arrest at the G1 checkpoint and inhibition of further cell proliferation. Using a replication-deficient recombinant adenovirus (AdV) ((rAd)-p21) as a p21 gene delivery system, we have evaluated the effect of p21 introduction in lung cancer cells in vitro as well as in vivo. In in vitro experiments, two human non-small cell lung cancer (NSCLC) cell lines, NCI-H460 and NCI-H322, showed dose-dependent p21 induction and concomitant cell growth inhibition following rAd/p21 infection. Flow cytometric analysis of the cell cycle revealed a significant increase in the percentage of NCI-H460 cells in G0/G1 following rAd/p21 infection compared with untreated cells, suggesting that p21-induced growth inhibition was due to G0/G1 arrest. We also tested the therapeutic efficacy of rAd/p21 in an in vivo human NSCLC model in SCID mice. Tumor-bearing mice were established by subcutaneous injections of NCI-H460 cells and treated by repeated intratumoral injections of rAd/p21. Intratumoral delivery of rAd/p21 significantly suppressed tumor growth and prolonged survival in rAd/p21-treated mice. Our in vitro and in vivo results provide strong preliminary evidence for the growth inhibition of NSCLC by rAd/p21. Collectively, these results justify further studies to evaluate the efficacy of rAd/p21 for gene therapy in human lung cancer.     

用户被双相钢良好的强度和抗腐蚀能力所吸引

扩大市场份额的机会。虽然双相不锈钢的全球市场份额约为1%,但仍被低估。其中欧洲的市场占比为3.9%,高于美洲和亚洲,但欧洲经济目前正停滞不前。这说明主要的市场增长在美洲特别是在亚洲,双相不锈钢目前在亚洲的市场份额仅为0.3%。中东地区也一样,海水淡化工业和油气开采业给双相钢带来的机遇说明双相不锈钢蕴藏着巨大的市场机会。