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。     

The 80-year history of duplex stainless steel

80 years has passed since duplex stainless steels were first produced and now they have developed into an integral series with the efforts on R & D and development of technology.In the recent decade, duplex stainless steels have been accepted by more and more customers and increasingly used. The first duplex grade produced in Sweden was 453E(26Cr-5Ni) in the 1930s,and then developed into 329.These two grades were characterized by high carbon content and called the first generation of duplex stainless steels.At that time,it was very difficult to add nitrogen into the steels and maintain the phase equilibrium,thus influencing the application properties,for example,intergranular corrosion post welding. One method to solve this problem is to alter the chemical composition,like adding nitrogen,etc.And that came to reality with the development of AOD and metallurgical theory of stainless steels.New series of duplex grades,called the second and third generations duplex,have successively emerged since the 1980s. These grades are characterized by high amounts of alloying elements,like chromium,molybdenum and nitrogen.Furthermore,super duplex stainless grades,like S32750,S32760 and S32707,were developed for various harsh service environments with their outstanding corrosion resistance and workability.These grades possess corrosion resistance corresponding to super austenitic grades,or close to nickel-base alloys, and are used in ocean-engineering,sea water desalination and oil industries,etc. And the application of duplex stainless steel is expending into other industries.For instance,453E is used in the pulp & paper industry.2205(S32205),a medium-alloyed grade,has become the most typical one in the duplex stainless steel family and widely used in many industries like pulp & paper,chemical and oil.New applications are emerging with better understanding of the duplex grades. Modern duplex stainless steels features most the corrosion resistance and strength,making them most cost-efficient in more and more projects. In this paper,the history of duplex stainless steels is recalled and reviewed from R&D,production to application,and latest grades like S82441 are also introduced.     

Effect of Process Parameters on Clad Quality of Duplex Stainless Steel Using GMAW Process

In recent years, weld cladding are being applied in numerous industries as cost effective engineering solution to use a surface protection layer to protect carbon steel against corrosion attack. The desirable characteristics of cladding alloy are reasonable strength, weldability, resistance to general and localized corrosion attack. The duplex stainless steel having all the desirable characteristic is the candidate material for cladding. However, duplex weld metals have not been studied in detail as duplex stainless steels. Consequently, the properties of duplex weld metals are less well known and only partially understood. In the present study, the properties of duplex weld deposits of the 22 % Cr, 10 % Ni, 3 % Mo, and 0.12 % N type using GMAW process have been investigated. In particular, the influence of welding heat input and shielding gas composition in GMAW process on weld deposit microstructure, impact toughness and resistance to pitting corrosion have been studied. It is observed that concentration of nitrogen of weld deposits influenced by both heat input and shielding gas composition exerted significant effect on microstructure, low temperature toughness and resistance to pitting corrosion.     

445M铁素体不锈钢缝隙腐蚀性能的研究

研究了445M铁素体不锈钢(%:0.004～0.005C、22.24～22.29Cr、1.10～1.65Mo、0.015～0.016P、0.003～0.004S、0.012～0.016N、0.22～0.38Ti)和316L奥氏体不锈钢(%:0.022C、16.80Cr、10.19Ni、2.02Mo、0.025P、0.001S、0.046N)在40～60℃氯离子浓度(250～5 000)×10^-6的氯化钠溶液的缝隙腐蚀性能。结果表明,445M铁素体不锈钢的耐缝隙腐蚀性能优于316L奥氏体不锈钢;当445M钢中的Mo含量由1.10%提高至1.65%时,钢的耐缝隙腐蚀性能明显提高,表明点蚀当量Cr+3.3Mo是衡量不锈钢耐点蚀和耐缝隙腐蚀的重要指标。     

Nickel Release Rate of Several Nickel-containing Stainless Steels for Jewelries

Nickel-containing stainless steels have been widely applied in watch and jewelry production,and their responses to the Nickel Directive become a universal concern in the industry.The nickel release rates and corrosion behaviors of types 316 L,304,303 and 201stainless steels under the conditions of solid solution and mirror polishing were studied by artificial sweat soaking and electrochemical methods.The results show that the weekly nickel release rates in artificial sweat do not strictly correspond to the nickel contents,which present a descending order as 303 stainless steel of 2.06μg/cm2,201 stainless steel of 1.51μg/cm2,304 stainless steel of 0.08μg/cm2 and 316 L stainless steel of 0.02μg/cm2.Both the nickel release rates of type 303 and 201stainless steels significantly exceed the threshold values regulated in EN1811∶2011;therefore,they should be avoided to be used as watch and jewelry materials owing to the risk of nickel sensitization.The nickel release rates of 316 Land 304stainless steels meet the requirements of the standard.Sulfide inclusions in stainless steel become the sources of pitting and exacerbate the damage of the passivation membrane,which is the significant cause to enhance the nickel release rates.     

Corrosion Behaviour of Chrome–Manganese Austenitic Stainless Steels and AISI 304 Stainless Steel in Chloride Environment

Electrochemical behaviour of chrome–manganese austenitic stainless steels (Cr–Mn ASS) and AISI 304 stainless steel (SS) is evaluated in various chloride (Cl^?) concentrations (Cl^? free to 20,000 ppm) to simulate rural, industrial and marine environment. Potentiodynamic polarization and electrochemical impedance spectroscopy has clearly shown that with increase in Cl^? concentration, the corrosion rate of both Cr–Mn ASS and AISI 304 SS increases and polarization resistance decreases. Comparatively, Cr–Mn ASS is more affected by Cl^? concentration than AISI 304 SS. This is attributed to relatively low Cr content and lack of Ni. The findings have been explained with the help of point defect model. However, in less aggressive environment of up to 100 ppm Cl^? concentration, Cr–Mn ASS may be a candidate material as a cheaper substitute of AISI 304 SS. Ways of improving corrosion resistance of Cr–Mn ASS by alloying with various elements have also been discussed. It is argued that a dedicated effort is needed to improve corrosion resistance of Ni-free or low-Ni Cr–Mn ASS.     

超塑性奥氏体-铁素体双相不锈钢00Cr25Ni7Mo3N的研制

通过电弧炉-电渣重熔工艺开发研制了成分为(%):0.021C,24.16Cr,7.21Ni,2.87Mo,0.17N,0.48Cu超塑性双相不锈钢00Cr25Ni7Mo3N。试验结果表明,00Cr25Ni7Mo3N超塑性双相不锈钢的耐孔蚀性和耐缝隙腐蚀性远高于传统的304L和316L奥氏体不锈钢。在变形温度960℃、应变速率2×10^-3/s时,00Cr25Ni7Mo3N超塑性双相不锈钢的最高延伸率为960%,该钢超塑性变形的均匀性优于TC4钛合金,可显著减轻构件的重量。     

Effect of heating mode and electrochemical response on austenitic and ferritic stainless steels

Abstract

Powder metallurgical (P/M) processing has the main advantage of making near net shape products. Nowadays, in automobile industries, stainless steels have become the most promising material owing to their good corrosion resistance. In the current study, 316L and 434L stainless steel powders were sintered using microwave and conventional methods through powder metallurgy route. The effects of sintering modes on the microstructure, mechanical properties and corrosion responses of 316L and 434L stainless steel composites are investigated in detail. The results showed that the sample prepared through microwave sintering route exhibited significantly superior densification, higher hardness and better corrosion resistance as compared to the conventionally processed counterpart. On the whole, 316L composites showed better corrosion resistance than 434L stainless steels.     

镍对Cr-Ni-Si系铸造不锈钢性能的影响

研究了Ｃｒ－Ｎｉ－Ｓｉ系耐浓硝酸铸造不锈钢的化学成分,耐蚀性、冲击韧性。试验结果表明,含７％Ｎｉ的铁素体－奥氏体双相钢,具有良好的冲击韧性和耐腐蚀性能。     

445J2超纯铁素体不锈钢和316L超低碳奥氏体不锈钢在溴化锂溶液的点蚀分析

445J2铁素体不锈钢由于高的导热率、低的热膨胀系数以及良好的耐蚀性能使得其作为溴冷机中一些部件的良好候选材料,本文采用电化学测试方法对比研究了445J2超纯铁素体不锈钢(/%:0.01C,22.5Cr, 1.9Mo, 0.27Nb, 0.20Ti, 0.09Al, 0.36Cu, 0.015P,0.001S,0.015N)和316L奥氏体不锈钢(/%:0.002C,16.8Cr, 10.19Ni, 2.02Mo, 0.025P,0.0008S)在20～60℃0.1～1M的溴化锂溶液中的点蚀行为,并采用扫描电镜(SEM)和能谱分析仪(EDS)对电化学结果进行表征。结果表明,随着LiBr温度和浓度的升高,两种钢腐蚀电流密度增大,点蚀电位降低,耐点蚀性变差;氧化物和硫化物夹杂会引起两种钢的点蚀;高含量的Cr以及Mo、Ti、Nb、Al等合金元素使445J2钢具有优异的耐点蚀性能。     

NaCl+HCl溶液中Ce对双相不锈钢腐蚀行为的影响

为了研究酸性NaCl溶液中双相不锈钢的耐腐蚀性能,以含微量稀土Ce的UNS S31803双相不锈钢为研究对象,采用电化学阳极极化和交流阻抗相结合的方法测试其在NaCl+HCl混合溶液中的耐腐蚀性能。利用扫描电镜(SEM)观测腐蚀后的形貌特征,采用电子探针(EPMA)检测合金元素与杂质元素的分布特征,分析Ce元素的加入对双相不锈钢电化学腐蚀行为的影响机制。结果表明,钢中存在两相的选择性腐蚀并伴有局部点蚀,其中铁素体相是腐蚀较严重的相;阳极极化测试与交流阻抗测试结果相吻合,Ce拓宽了试验钢的钝化区间;Ce通过净化钢液、降低S和P元素在相界的偏聚及使Cr、Ni和Mo等合金元素在两相中的分布更均匀等作用,提高了钢的耐腐蚀性能。     

碳含量对Cr17Mo型耐蚀塑料模具钢组织和性能的影响

试验研究了成分(％)为:0．39C,0．70Ni,16．73Cr,1．07Mo和0．53C,1．05Ni,16．87Cr,0．96Mo两种Cr17Mo型耐蚀塑料模具钢的淬回火组织、力学性能和耐蚀性能。试验结果表明,当Cr17Mo型钢中碳含量由0．39％提高至0．53％时,经1 060℃淬火,475℃回火后该钢的峰值硬度HRC值由46．5提高到53．4;两种试验钢在弱酸、氧化性酸和1％盐酸中均有较高的耐腐蚀性能。     

超级高氮奥氏体不锈钢的耐腐蚀性能及氮的影响

用电化学测试、化学浸泡等方法研究了超级奥氏体不锈钢00Cr24Ni22Mo7Mn3CuN(654SMO)的耐点腐蚀和耐缝隙腐蚀的性能。通过改变氮含量,研究了氮对奥氏体不锈钢的耐点腐蚀和耐缝隙腐蚀性能的影响,结果表明,氮和适量的铬、钼结合,能显提高奥氏体不锈钢的耐点腐蚀和缝隙腐蚀的能力,并且随着氮含量的增国,砥体不锈钢的耐点腐蚀和耐缝隙腐蚀的能力也增强,对比实验表明,超级奥氏体不锈钢在耐点腐蚀,缝隙腐蚀等局部腐蚀性能方面可以和镍基合金C－276媲美,甚至优于镍基合金。     

硅对含强氧化性离子沸腾硝酸中奥氏体不锈钢耐蚀性的影响

 超低碳Cr Ni奥氏体不锈钢在含强氧化性离子的硝酸溶液中会发生过钝化腐蚀和晶间腐蚀,而高硅不锈钢在强氧化性浓硝酸中具有优良的耐蚀性。笔者以高纯级000Cr25Ni20和00Cr14Ni14Si4钢作为对比材料,发现在纯稀硝酸中000Cr25Ni20钢具有更优良的耐蚀性,在不同含量的40%沸腾硝酸溶液中,00Cr14Ni14Si4钢可有效抑制过钝化腐蚀,而且不发生晶间腐蚀。     

增氮节镍型316奥氏体不锈钢的耐冲蚀性能

采用30 kg真空感应炉熔炼了试验用316钢(/%:0.04C,0.36Si,2.00Mn,0.009P,0.024S,17.74Cr,11.74Ni,2.56Mo)以及采用常压充氮和加入氮化合金熔炼了试验用增氮节镍型316钢(/%:0.04C,0.25Si,1.86Mn,0.012P,0.021S,16.90Cr,8.18Ni,2.64Mo,0.36N),经锻造和轧制成4 mm带材,并经1 100℃1 h固溶处理。借助电子天平、扫描电镜以及自制的砂浆冲蚀磨损试验装置,对试验钢的冲蚀磨损率以及冲蚀磨损后的表面形貌进行了表征与分析。结果表明,两种试验奥氏体不锈钢的磨损率随着冲蚀角度的增大,出现了先上升,后下降,再上升的趋势,在45°与90°出现了两个峰值,当冲蚀角度为90°时,磨损率达到最大值;两种奥氏体不锈钢的冲蚀磨损率随着冲蚀速度和冲蚀时间的增加而增大。在相同的冲蚀条件下,增氮节镍型316奥氏体不锈钢具有较优的耐冲蚀磨损性能和较低的冲蚀磨损率。     

Corrosion behaviour of low-Cr high-Al stainless steels in 65% boiling HNO3

The corrosion resistance of low-Cr high-Al steels has been tested in 65% boiling HNO₃ solution. Comparison of this resistance and that of stainless steels 304, 430 and 410 under the same conditions reveals that Al has a beneficial effect on the corrosion resistance of Fe-Cr-Ni steels. The reduction of about 7% Cr can be compensated by about 5% Al provided that Ni is maintained at about 15–18%.     

Cr和Si元素对奥氏体不锈钢组织构成及凝固路线的影响

以316Ti奥氏体不锈钢为基础,设计不同Cr和Si元素含量的合金成分,结合Thermal-Calc热力学模拟计算与合金铸锭凝固组织形貌、成分分析,研究了Cr和Si元素对合金凝固组织构成的影响。研究结果表明,热力学计算能够获得奥氏体不锈钢中析出δ相的临界Cr和Si含量。合金凝固时的元素偏析和冷却过程中的“δ→γ”相变可对δ相析出预测产生一定影响。此外,本工作还针对δ相析出评价了两种凝固路线判据。      

钨含量及固溶温度对022Cr25Ni7Mo3.5WCuN钢耐腐蚀性能的影响

研究了钨含量及固溶温度对超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能的影响。通过化学浸泡失重法和电化学极化曲线法,测试了超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能,并运用Thermo Calc热力学计算辅助分析。结果表明,固溶温度对超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能影响效果显著,在1 100 ℃时,022Cr25Ni7Mo3.5WCuN 的耐腐蚀性能达到最佳;在理想的固溶条件下,钨元素有助于钝化膜的形成,钨含量的增加使得022Cr25Ni7Mo3.5WCuN的耐腐蚀性能增强,在钨质量分数为1.5%时,022Cr25Ni7Mo3.5WCuN获得最佳耐腐蚀性能,若钨含量继续增加,打破了α和γ两相的平衡,则耐蚀性能降低。     

硫酸介质中铸造奥氏体不锈钢的腐蚀磨损行为

研究了几种铸造奥氏体不锈钢在含有Ｃｌ－的硫酸介质中的点蚀规律,测定了腐蚀磨损率、摩擦因数和表面钝化膜破坏后的修复时间。实验结果表明,高铬、镍、铜不锈钢有较高的耐蚀性,但其腐蚀磨损失重却高于一般的１８－８型不锈钢     

高温浓硫酸中氟离子掺入对不锈钢耐蚀性能的影响

采用浸泡法和电化学测试方法结合扫描电镜和能谱仪研究了高温浓硫酸中氟离子的掺入对304、2507以及904L三种不锈钢耐蚀性能的影响.结果表明:氟离子的掺入对三种不锈钢在浓硫酸中的腐蚀具有抑制作用,综合来看,904L具有更为稳定的耐蚀性能;三种不锈钢在高温浓硫酸中由于生成了热力学不稳定的硫化镍而产生了活化转钝化现象,而掺入氟离子会和硫离子发生竞争使其排挤出电极表面,氟离子与镍离子结合形成另外一种更稳定的阻挡层使不锈钢耐蚀性提高.