Development of ferritic stainless steel B445R with superior corrosion resistance for architectural applications

The dull-finish ferritic stainless steel(FSS) sheet B445R for architectural roofing has been developed by Baosteel.This steel product exhibits excellent corrosion resistance superior to that of SUS 316L with a lower cost.It can be easily formed into roofing panels by ordinary processes.Moreover,the thermal strain of it is less than SUS 316L because of its lower thermal expansion coefficient,and its reflectivity is lower due to the dull-finish treatment.All of these features make it capable of being used as architectural roofing materials in coastal regions.     

建筑用高耐蚀性铁素体不锈钢B445R的研制

宝钢研制出了建筑屋顶装饰用铁素体不锈钢B445R毛面产品。该产品的耐蚀性比奥氏体不锈钢SUS316L更优越,成本也比SUS316L低,采用常规的成形方法就可以将其加工成屋顶面板。此外,由于该产品的热膨胀系数比SUS316L小,故其热变形也比SUS316L小,同时由于进行了毛化处理,其表面具有较低的光反射能力。所有这些优点使其有能力成为沿海地区建筑物的屋顶装饰材料。     

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。     

建筑维护系统用高耐蚀性铁素体不锈钢的研发与应用

研究了Mo、Nb、Ti对22.5%Cr铁素体不锈钢力学性能、耐腐蚀性能的影响,研究结果表明,Mo主要以固溶状态存在于铁素体不锈钢中,通过固溶强化提高了铁素体不锈钢的强度;在Ti/Nb双稳定铁素体不锈钢中,由于粗大TiN颗粒的形成和金属间化合物在晶界的析出,钢的韧性明显降低;在Nb单稳定铁素体不锈钢中,Nb以固溶状态和Nb(C,N)析出相存在于铁素体基体中,Nb(C,N)弥散分布于铁素体晶内,并作为σ相的形核质点,避免了σ相在晶界的析出,从而改善了钢的低温韧性。在此基础上研制出建筑维护系统用的高耐蚀性铁素体不锈钢B445R。测试结果表明,B445R在氯离子溶液中具有比316L更优越的耐点腐蚀性能,而且具有良好的成形性能和焊接性能,这些优点使其成为沿海地区建筑维护系统理想的装饰材料。     

B443超低碳氮铁素体不锈钢的研究

为开发价格昂贵的SUS304奥氏体不锈钢的替代产品,试验研究了不同含量C N和Nb,Ti稳定化对B443系列铁素体不锈钢再结晶组织、力学性能、点蚀电位的影响.试验结果表明,Nb,Ti双稳定化提高了B443铁素体不锈钢的再结晶温度和点蚀电位.在试验室研究基础上,宝钢不锈钢分公司试制了B443NT超低碳氮铁素体不锈钢.该产品不仅具有与SUS304相当的耐腐蚀性能,而且具有优良的深拉伸性能和满意的焊接性能,可用于运输、建筑、厨具等众多行业.     

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。     

TTS443高铬铁素体不锈钢的开发

针对304(Crl8-Ni8型)奥氏体不锈钢和430(Cr17型)铁素体不锈钢的特性,通过试验和分析Cr、Cu、Nb、Ti等合金元素对铁基合金材料性能的影响,开发出一种高铬铁素体不锈钢-TTS443(/%:O.010C、21Cr、0.40Cu、0.25Nb、0.20Ti、O.012N) 。该钢种的耐蚀性能与304奥氏体不锈钢相当,具有良好的成形性与焊接性能,TTS443铁素体不锈钢是304奥氏体不锈钢理想代替材料。     

新型汽车排气系统用铁素体不锈钢的冷凝液腐蚀研究

 铁素体不锈钢中Cr元素对其耐腐蚀性能起着非常重要的作用。本文采用实验室冷凝液腐蚀实验方法,对一系列汽车排气系统用铁素体不锈钢在实验室模拟冷凝液中的腐蚀性能进行了研究。所有钢种经过10周期的实验室冷凝液腐蚀实验后,研究结果表明：Cr当量高于17%的铁素体不锈钢与含17%Cr的铁素体不锈钢耐实验室冷凝液腐蚀性能相当,且平均腐蚀失重量均小于6g/m2,平均最大腐蚀深度均小于0.03mm。在此实验结果的基础上,对新开发的439M型铁素体不锈钢和409L型铁素体不锈钢进一步开展5周期、10周期、20周期的实验室冷凝液腐蚀实验,并使用极值分析方法对三种周期冷凝液腐蚀实验后样品的最大点蚀深度进行统计分析,研究结果表明,新开发的439M型铁素体不锈钢的预测寿命是409L的1.6倍。     

Development and application of nitrogen-alloyed austenitic stainless steels in Baosteel

In recent years,nitrogen-alloyed stainless steels have been a research hotspot in the field of stainless steel product and technology. Nitrogen-alloyed austenitic stainless steels developed by Baosteel and their applications are introduced. These steels are nitrogen-controlled products 304 N and 316 LN,nitrogen containing economical products BN series and high-nitrogen stainless steel( HNS) series. The results show that the presence of nitrogen can significantly improve the strength and corrosion resistance of steel produced. By nitrogen alloying,economical austenitic stainless steels w ith considerably less nickel than 304 can be obtained; the corrosion resistances of these steels are almost the same as 304. Furthermore,by a scientific approach of nitrogen alloying,high-nitrogen steel of0. 8% nitrogen content is fabricated under the non-pressurized conditions,and the pitting potential of this steel is 1. 0 V. At present,nitrogen-alloyed steels developed by Baosteel are w idely utilized in the manufacture of cryogenic storage containers,transportation containers,and many household w ares.     

Inclusion control of ultra clean ferritic stainless steel

The most important characteristics of the ultra clean ferritic stainless steel is that the carbon,nitrogen and other interstitial elements are very low.The ultra clean ferritic stainless steel has been widely used for household appliances,auto exhaust system,elevator,water treatment system,building roof and other various fields,because of its low cost,pro-environment,excellent properties.They can replace some traditional austenitic stainless steel.such 304 and 316L.The addition of titanium to liquid steel has become common for stabilizing nitrogen and carbon in steel.Titanium reacts with nitrogen,carbon,and oxygen to form titanium nitride,carbide, carbonitride and oxide.These inclusions may have a deleterious effect on the properties such as toughness, ductility,weldability and corrosion.In addition,the inclusions can also agglomerate and cause surface quality problem of the slab and clogging of the submerged entry nozzle during continuous casting process. The formation rules of inclusions in ultra clean ferritic stainless steel were investigated by the thermodynamic calculation,and methods of controlling inclusions were put forward to improve the quality of product.The composition,type,amount,size and distribution of the inclusions in the slab are investigated by optical microscope and scanning electron microscope.The results can be concluded as follows.（1） In the slab,the main original inclusions,with size of larger than 2μm,are Al₂O₃,TiN or Ti（CN） and complex TiN or Ti（CN） inclusion with core of MgO,MgO-Al₂O₃ and Ti₂o₃,which will not affect the performance of the steel if they are in diffusing distribution.The size of these inclusions are less than 10μm except some Al₂O₃ inclusions in size of 10-40μm.（2） Foreign inclusions are Ti₂O₃-Al₂O₃-MgO-SiO₂ in size above 50μm covered by TiN or Ti （CN）.Although these inclusions are few,they do harm to the surface quality of stainless steel.It is able to reduce the risk of forming this kind of inclusion by aluminium deoxidation with increasing Al content to restrain the formation of Ti₂O₃.（3 ） TiN or Ti（CN） is easy to precipitate on inclusions such as MgO,MgO-Al₂O₃ and Ti₂O₃,except Al₂O₃.Controlling the content of[Ti]and[N]and the formation of the oxides can be used to control the precipitation of TiN or Ti（CN）.     

Low molybdenum ultra-pure ferritic stainless steel for solar water heaters

In order to meet the demands of service life and the synthetical performance/price ratio of stainless steel in the solar water heater industry,the low molybdenum ultra-pure ferritic stainless steel(FSS) B445J1M was developed at Baosteel.In this study,comparative studies were carried out on the mechanical properties,the formability and the corrosion resistance of B445J1M,304 and 444,and the advantages and application fields of B445J1M were summarized.     

宝钢太阳能热水器用低钼超纯铁素体不锈钢

为满足太阳能热水器行业对不锈钢材质服役能力以及综合性价比的需求,宝钢开发了适用于水系统介质的低钼超纯铁素体不锈钢B445 J1M。对比分析了B445 J1M、SUS304以及SUS444不锈钢的力学性能、成形性能以及耐蚀性能,概括了B445 J1M钢种的优势与可应用领域,并就太阳能热水器行业不锈钢用材提出了建议。相较于SUS444,B445 J1M具有更佳的拉深成形性能以及焊接性能,其胀形能力、耐点蚀、盐雾腐蚀以及氯离子应力腐蚀性能与SUS444相当,同时有更佳的性价比;相较于SUS304,B445 J1M的耐氯离子应力腐蚀性能及耐点蚀性能更优,尤其是其耐氯离子应力腐蚀性能,更加适合于热水器对材质的要求。     

304L不锈钢焊缝在混凝土模拟孔隙液中的点蚀行为

采用动电位极化曲线、电化学阻抗谱、Mott-Schottky曲线等电化学方法研究了以308 L为焊丝的304 L不锈钢焊接接头在不同氯离子含量的混凝土模拟孔隙液中腐蚀行为和电化学规律.随Cl-增加,304 L不锈钢焊接接头的三个区域(母材、焊缝和热影响区)在混凝土模拟孔隙液中的自腐蚀电位、点蚀电位及电荷转移电阻降低,钝化膜中载流子密度和焊接接头的点蚀坑数量增加.在同浓度的腐蚀溶液中,308 L的焊缝区域耐蚀性最佳,热影响区次之,304 L基体表现出低的电荷转移电阻和高的掺杂浓度使得母材的耐蚀性最差.      

表面处理对海洋工程用316L不锈钢耐点蚀性能的影响

316L不锈钢为常用的耐蚀合金材料,然而其在海洋大气环境服役时易遭受点腐蚀而发生失效。通过点腐蚀速率、临界点蚀温度、点蚀电位、极化曲线测试等评价方法,对经过不同表面处理(光亮退火、抛光、酸洗钝化)后的316L不锈钢的耐点蚀性能进行测试分析。结果表明,不同表面处理对316L不锈钢的临界点蚀温度影响不大,但会使点腐蚀速率、点蚀电位有所差异;在测试条件下,抛光及酸洗钝化均可有效提高316L不锈钢的耐点蚀性能,其中酸洗钝化态的耐点蚀性能最好,因此建议对海洋工程用316L不锈钢产品在使用前进行酸洗钝化处理。     

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.     

Enhanced Corrosion Resistance of Stainless Steel Carburized at Low Temperature

The pitting corrosion resistance of surface-modified 316L austenitic stainless steel and N08367 (a “superaustenitic” stainless steel) were evaluated in 0.6 M NaCl solutions and compared to untreated samples of the same materials. The surface modification process used to treat the surfaces was a low-temperature carburization technology termed “low-temperature colossal supersaturation” (LTCSS). The process typically produces surface carbon concentrations of ~15 at. pct without the formation of carbides. The pitting potential of the LTCSS-treated 316L stainless steel in the NaCl solution substantially increased compared to untreated 316L stainless steel, while the pitting behavior of the LTCSS-treated N08367 was unchanged compared to the untreated alloy. This article is based on a presentation given at the “International Conference on Surface Hardening of Stainless Steels,” which occurred October 22–23, 2007 during the ASM Heat Treating Society Meeting in Cleveland, OH under the auspices of the ASM Heat Treating Society and TMS.

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439超纯铁素体不锈钢耐蚀性评价

通过盐雾试验、电化学试验和FeCl3点腐蚀试验,并结合扫描电镜,对比研究了439超纯铁素体不锈钢和430普通铁素体不锈钢的耐腐蚀性能。结果表明,碳、氮间隙元素极低的439超纯铁素体不锈钢耐点蚀性能明显优于430普通铁素体不锈钢,虽然430钝化膜修复能力较强,但点腐蚀速率也较快;430不锈钢具有严重的晶间腐蚀敏感性,同样,430普通不锈钢在干湿加速盐雾试验中发生了严重腐蚀,439超纯铁素体不锈钢在上述腐蚀试验中均表现出轻微的腐蚀。可见在430普通不锈钢基础上降低碳、氮间隙元素含量,同时加入钛稳定化元素,使其耐腐蚀性能大幅提高。     

Ce和W对444铁素体不锈钢耐点蚀性的影响

采用浸泡失重法和电化学方法研究Ce和W对铁素体不锈钢在含Cl-溶液中耐点蚀性能的影响,并通过恒电位极化法测定不同Ce和W含量的铁素体不锈钢临界点蚀温度(CPT)。结果表明,W和Ce都可显著抑制铁素体不锈钢在FeCl₃溶液中的腐蚀溶解,且含W的不锈钢蚀坑坑底有W元素富集。Ce和W的添加提高了不锈钢在5%NaCl溶液中的临界点蚀温度,并且当W的质量分数达到1%时,可以显著增强蚀坑的再钝化能力。添加Ce和W可提高不锈钢的点蚀电位,降低腐蚀电流密度,提高不锈钢的耐点蚀性能。不同成分的铁素体不锈钢在中性氯溶液中都表现出稳定的钝态,而Ce和W的添加可以提高钝化膜的稳定性,扩大钝化区范围。     

合金元素对双相不锈钢2101耐点蚀性能的影响

研究了合金元素对双相不锈钢2101耐点蚀性能的影响规律。结果显示,2101系列合金的浸泡点蚀腐蚀速率在1.9～7.0 g/（m^2.h）之间,与304不锈钢在同一数量级;Mo是提高2101系双相不锈钢耐腐蚀性的关键元素,而N对耐腐蚀性的影响不大;点蚀起源和Thermo-Calc计算结果显示2101成分体系中,铁素体相是耐点蚀性较弱相,提高铁素体相耐蚀性是提高合金整体耐蚀性的关键;当Cr含量固定在21.5%时,Mo作为铁素体形成元素将在铁素体相中富集,提高铁素体相的耐点蚀性能,从而提高合金整体耐蚀性。     

Influence of strain-induced phase transformation on the surface crystallographic texture in cold-rolled-and-aged austenitic stainless steel

Stainless steels (SSs) having a stable and metastable austenitic phase were studied to see the influence of strain-induced phase transformation in the metastable austenitic stainless steel on the evolution of texture during cold rolling and aging. AISI 304L and 316L SS plates were unidirectionally cold rolled up to a 90 pct reduction and aged at different aging temperatures. The strain-induced transformation of austenite to α′-martensite phase and the evolution of texture in both the phases were studied as a function of rolling reduction as well as aging temperature in the metastable 304L austenitic stainless steel. The X-ray diffraction (XRD) technique was employed to quantify the volume fractions and characterize the texture of austenite and martensite phases in the rolled and aged conditions. Results are compared with the texture evolution in the stable austenitic 316L SS.