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.     

电化学方法在不锈钢腐蚀研究中的应用现状及发展趋势

电化学手段可以实现对不锈钢材料的快速评价和腐蚀机理研究,因而受到广泛应用。在不锈钢耐蚀性评价方面,最常采用的电化学手段主要有腐蚀电位测试、交流阻抗测试、恒电位极化测试以及循环动电位极化测试。本文分别针对上述四种电化学方法在不锈钢耐蚀性评价上的应用情况进行了介绍,明确了各种检测方法的特点。腐蚀电位及交流阻抗测试是无损检测手段,可以满足长周期腐蚀监测需求;恒电位极化和循环动电位极化测试可以获得材料的极化特征参数,有利于对材料的腐蚀机理及耐蚀性进行评价。结合当前的不锈钢腐蚀研究现状,展望了电化学方法在腐蚀研究领域的发展趋势:未来电化学方法将更多作为腐蚀调控手段,需要结合其他检测技术实现对不锈钢腐蚀过程的精细分析。      

Corrosion-resistant coating for GTE compressor parts made of steels with low tempering temperatures

The corrosion resistance of an Ni–Co–Cr–Al–Si–Y + SPh (SPh is silicophosphate impregnation) alloy coating on 30Kh13, 38Kh2MYuA, VKS5, and VKS7 structural steels with low tempering temperatures has been studied. The steel–coating compositions have been tested to determine the accelerated cyclic corrosion resistance, the corrosion resistance under tropic climate chamber conditions and in salt fog, the stress corrosion resistance, and the corrosion resistance in an industrial atmosphere. The heat stability of coated samples is studied, metallographic studies of the samples before and after the tests are performed, and the influence of the coating on the strength characteristics of the structural steels is studied.     

Comparative Evaluation of Low Nickel and Nickel Free Lean Duplex Stainless Steels with 316L in a Variety of Corrosive Media

For many applications duplex stainless steels with their superior strength coupled with lower raw material cost have emerged as an attractive alternative to austenitic stainless steels. With emphasis on conservation of scarce resources like nickel and molybdenum there is continuing endeavour to develop essentially molybdenum free lean duplex stainless steels with low nickel content such as 2304 (23Cr–4Ni), 2202 (22Cr–2Ni), 2101 (21Cr–1.5Ni). This paper compares the corrosion behaviour of a low nickel duplex (21Cr–1.5Ni) and a nickel free duplex (21Cr–1.5Cu) with 316L stainless steel in several corrosive media. All the three alloys exhibit similar excellent corrosion resistance under boiling conditions in less aggressive organic acids such as 20 % acetic acid, 25 % lactic acid, 25 % citric acid. However, in stronger organic acids such as 5 % formic acid, 5 % oxalic acid, and mixture of formic and acetic acid, the duplex grades exhibit superior corrosion resistance. This edge over 316L continues on addition of chloride ions in these acids. In boiling 50 % nitric acid solution, the corrosion resistance of these nickel free and low nickel duplex is slightly better than 316L grade. Since 304L grade is generally used in nitric acid plants, tests were also conducted on 304L and these duplex grades were found to be more resistant. Similarly in 50 % phosphoric acid also, the duplex grades exhibit superior corrosion resistance compared to 316L grade. Alloying with nickel and molybdenum is known to give rise to significant improvement in corrosion resistance in this acid. However, even in the absence of these elements, the beneficial effect of higher chromium content is evident. Of all the inorganic acids, sulfuric acid is used in largest volume in the industries. Boiling tests in dilute 1 and 5 % H₂SO₄ indicate that nickel free copper bearing duplex is more resistant than low nickel duplex grade and vastly superior to 316L Thus nickel-free and low-nickel duplex stainless steels offer a very attractive combination of high corrosion resistance coupled with cost effectiveness in a wide variety of corrosive media.     

高强度油井管用钢专利技术的现状及发展趋势

概述了近年来对于高强度油井管用钢专利技术的重点研发领域-耐高温(≤650℃)、耐腐蚀(H₂S、CO₂、Cl^-介质)、抗挤毁(屈服强度380～1241 MPa)等关键技术的研究,介绍了最新高强度油井管用钢的研究和发展特点,生产典型高强度油井管用钢的关键技术。当前油井管用钢的开发趋势为通过低C、高合金和调质处理工艺生产具有耐高温、耐腐蚀、抗挤毁等复合特性的高强度焊管和无缝管。     

Increasing the corrosion resistance of low-alloy and carbon steels for automobile construction by optimizing the metallurgical technology

It is shown that the corrosion resistance of automobile sheet can be improved by ensuring that steels of this type have a low content of corrosion-active nonmetallic inclusions (CANI). The main mechanisms responsible for the formation of CANI in automobile sheet have been established, and recommendations have been developed to reduce their concentration in this product • optimize the deoxidation processes that are used by ensuring that the proportions of the additions made to the steel are consistent with the composition of the ladle slag and that certain key temperature-time parameters of these processes are maintained • control the composition of the ladle slag to prevent the formation of solid phases in the slag and their transfer to the metal; certain conditions must also be observed in the argon blow and the introduction of the addtions. Use of the above recommendations to make automobile sheet and tube steels cleaner with respect to their content of CANI and thus help optimize out-of-furnace treatments at metallurgical and pipe plants will make it possible to improve the corrosion resistance of metal products used in automotive manufacturing. __________ Translated from Metallurg, No. 2, pp. 45–48, February, 2006.     

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%.     

非API 13Cr系马氏体不锈钢油套管的发展现状

API(美国石油协会)13Cr油套管具有良好的耐CO₂腐蚀性,但随新油田的开发,要求油套管具有优良的抗H₂S、CO₂高温耐蚀性。文中分析了国内外非API 13Cr马氏体不锈钢油套管(Cr13-Ni5-Mo,Cr13-Ni5-Mo2,Cr15-Ni6-Mo2-Cu等)的发展现状,叙述了相关生产厂家油套管的化学成分、力学性能和耐蚀性。     

Corrosion behaviors of cold rolling automotive sheets coated with anti- rust oil

To investigate the corrosion performance of commercial automotive cold rolling sheets under severe atmospheric environment, electrochemical impedance spectroscopy was used to detect the electrochemical behaviors of three types of cold rolling sheets and a humid- temper test was carried out to explore the corrosion behavior under shipping and storage environments. Meanwhile, the effects of surface status and micro- structure of the sheets on the corrosion behaviors were analyzed based upon the results of profile measurements, contact angle tests and metallographic analysis.The results show that with the same load of anti- rust oil, 590DP steel presents the largest electric resistance of oil film and charge transfer resistance, and the longest incubation period of rust under storage environment. All these good properties could be assigned to the surface profile of the steel. However, the generation rate rust turns to be faster later on, which can be attributed to its dual- phase microstructure. In sum, the surface wetting status of different types of sheets are almost the same, which has no significant effect on the corrosion performance of the steels. Comparatively, surface profile of the steels plays an important role during the initial stage of corrosion, and the difference in microstructure has a more remarkable influence on the development stage of corrosion.     

Increasing the Resistance of Automobile Sheet to Atmospheric Corrosion by Optimizing its Chemical Composition and the Parameters of the Manufacturing Process

A method involving alternating immersion in a 3.5% NaCl solution has been developed for corrosion tests of automobile sheet. Results obtained from 30 cycles of tests (10 + 50 min) of specimens of steels 08Yu, 08ps, 08YuP, 08YuDP, 08GSYuT, and IF established the dependence of the steel's unit weight gain from corrosion products on its combined content of carbon and silicon: steels with a lower content of these elements show a smaller gain in weight, i.e., they exhibit greater corrosion resistance. Steel alloyed with copper (0.23–0.34%) and phosphorus (0.06–0.08%) – the production of which has been mastered by the company Severstal' — has the highest resistance to corrosion. Use of the method makes it possible to rank grades of automobile sheet in one of three corrosion-resistance classifications in relation to their chemical composition and the parameters of the production process. __________ Translated from Metallurg, No. 8, pp. 46–52, August, 2005.     

Resistance against Abrasive Wear and Corrosion of Laser Powder Bed Alloyed High Chromium Tool Steels

Additive manufacturing by laser-based powder bed fusion of metals (PBF-LB/M) enables the production of complex shaped components. High-carbon tool steels tend to cracking during PBF-LB/M due to internal stresses caused by the rapid solidification. Expensive atomization and long lead times for powder generate high costs in this processing route. In situ alloying during PBF-LB/M of powder blends from conventionally available powders enables a more flexible approach of alloy design. For industrial use, the mechanical properties of in situ alloyed parts must be comparable to those of conventionally manufactured parts. In some cutting and forming applications, high wear resistance and corrosion resistance are required simultaneously. High alloyed cold work tool steels with sufficient chromium solved in the metal matrix fulfill these demands. Herein, AISI H13 is modified by Cr₃C₂ and elemental Cr to suit these requirements. Two novel alloys are modeled thermodynamically and processed by PBF-LB/M. In-depth microstructural investigations by backscatter electron imaging and diffraction in combination with abrasive wear tests and potentiodynamic polarization curves allow microstructure property correlations for different heat-treated conditions. Partial crack-free processing, hardenability, formation of Cr-rich carbides, and residual Cr-rich inclusions are observed and their influence on the wear and corrosion resistance is discussed.     

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.      

Pitting corrosion behavior of Cu-P-RE weathering steels

The weathering steels are prone to pitting corrosion in an environment containing chloride ions.The pitting behavior of Cu-P-RE weathering steels and its effect on the corrosion resistance of steels were investigated by multifarious analytical techniques,such as field emission-scanning electron microscopy(FE-SEM),electron probe microanalysis(EPMA),scanning Kelvin probe force microscopy(SKPFM),electrochemical workstation and a series of immersion tests.The results show that the original stripshap...     

经济型耐腐蚀钢中氧作用的研究

为了冶炼不同氧含量的碳素船体钢,通过机械性能试验和周浸试验研究了钢中氧含量对钢材腐蚀性能和机械性能的影响。结果表明,在连铸生产许可的氧范围内,随着钢水脱氧程度的减弱,钢中氧质量分数增加,钢材的平均腐蚀率略有下降,而耐点蚀性能有较明显增强,变化曲线的高氧端比低氧端平均点蚀深度下降约22.7%。弱脱氧钢的机械性能符合规范要求,可达到D级钢水平。分析认为,氧提高钢材耐蚀性的原因主要是固溶氧可提高铁的热力学稳定性,提高了蚀孔内铁的腐蚀电位,降低了蚀坑扩展速度。氧作为耐蚀元素应用可以显著降低耐蚀钢的成本,提高经济性。      

Study on the Corrosion Resistance of Multiphase TRIP Steels

Multiphase TRIP (Transformation Induced Plasticity) steels are known to combine higher strength with higher ductility.In this paper,the corrosion resistance of this steel has been has been investigated by accelerated corrosion tests,such as wet/dry cyclic corrosion and the weight loss in laboratory.The morphologies of their rust layers were observed by using scanning electron microscopy,and the corrosion performance of these steels was discussed by analyzing the protective mechanism.The results show that the corrosion rate of steel A is significantly greater than that of steels B and C in wet/dry cyclic corrosion and weight loss tests.The corrosion performance of conventional C-Mn-Si TRIP steel is deteriorated in both NaHSO 3 and 3.5 wt.% NaCl aqueous solutions.And superior corrosion performance is exhibited for TRIP steel with low alloying contents due to its high thermodynamic stability.The enhancement of corrosion performance of TRIP steel is attributed to the additions of alloying elements,such as Al,Cu,Cr,Mo,Ni,etc.The alloying elements increase the compactness of rust layers,so electrochemical characteristic of TRIP steel is improved.     

Structure and mechanical and corrosion properties of new high-nitrogen Cr-Mn steels containing molybdenum

The structure, mechanical properties, and pitting corrosion of nickel-free high-nitrogen (0.8% N) austenitic 06Kh18AG19M2 and 07Kh16AG13M3 steels have been studied in various structural states obtained after hot deformation, quenching, and tempering at 300 and 500°C. Both steels are shown to be resistant to the ?? ?? ?? and ?? ?? ? martensite transformations irrespective of the decomposition of a ?? solid solution (06Kh18AG19M2 steel). Austenite of the steel with 19 wt % Mn shows lower resistance to recrystallization, which provides its higher plasticity (??₅) and fracture toughness at a lower strength as compared to the steel with 13 wt % Mn. Electrochemical studies of the steels tempered at 300 and 500°C show that they are in a stable passive state during tests in a 3.5% NaCl solution and have high pitting resistance up to a potential E _pf = 1.3?C1.4 V, which is higher than that in 12Kh18N10T steel. In the quenched state, the passive state is instable but pitting formation potentials E _pf retain their values. In all steels under study, pitting is shown to form predominantly along the grain boundaries of nonrecrystallized austenite. The lowest pitting resistance is demonstrated by the structure with a double grain boundary network that results from incomplete recrystallization at 1100°C and from the existence of initial and recrystallized austenite in the 07Kh16AG13M3 steel. To obtain a set of high mechanical and corrosion properties under given rolling conditions (1200?C1150°C), annealing of the steels at temperatures no less than 1150°C (for 1 h) with water quenching and tempering at 500°C for 2 h are recommended.     

Corrosion Behaviour of New Railway Axle Steels

Corrosion behaviour of two newly developed axle steels (MS3 and MS6) is critically analysed and compared with that of the conventional railway axle steel with respect to the rust formed on the surface and microstructure of the steels. The microstructure of all three steels is ferrite–pearlite. Immersion, salt-fog exposure and dynamic polarisation tests in 3.5 wt% NaCl solution are carried out. New steels have much better mechanical properties and comparable corrosion resistance in immersion and dynamic polarisation test and much better corrosion resistance in salt-fog exposure test than that of the conventional axle steel.     

Recent developments in stainless steels:austenitic,ferritic,duplex

A review is given concerning some of the recent industrial developments of stainless steels. In austenitic stainless steels,two different directions of alloy development are noticeable:low nickel austenitic stainless steels and high nitrogen stainless steels.In these two cases the aims are different,particularly in terms of strength,but the philosophy of alloy development and the scientific approaches are very similar and they all revolve about the role of nitrogen as an alloying element and how this affects strength,ductility and corrosion resistance. There is now a broad and useful basis of information as to how nitrogen affects solid solution hardening,grain boundary hardening and work hardening and how to make use of these effects in developing materials required by the world market. In the field of corrosion resistance,ferritic,duplex and austenitic stainless steels compete with each other and now there is a growing body of information concerning the relative corrosion resistance based on laboratory data. However,for practical applications and for alloy selection,more than just laboratory data are needed,and thus,the first results are presented here of a many years comparison of the corrosion resistance of 24 commercial stainless steels exposed to corrosion in outdoors marine atmosphere.Hope is expressed to involve in the near future even more steels from a wider range of manufacturers in such corrosion studies.This might help consumers in appropriate alloy selection.It might also help steel makers in developing appropriate stainless steel grades.     

Cr Release from Stainless Steels

Cr release from stainless steels in different simulant fluids according to different test conditions is carried out with emphasis on ferritic stainless steels. Effects of Cr content and surface roughness on Cr release are discussed specially with a relation to corrosion resistant and passive film formation. Some primary results are attained： （1） higher Cr content means better corrosion resistance including higher potential and lower corrosion rate and less amount of Cr release from base metal; （2） decreasing surface roughness is in favor of the formation of passive film which can re- train Cr release from base metal effectively; （3） Cr content and surface roughness have synthetical effects on Cr release with a narrow innoxious field referring to surface roughness with decreasing Cr content in stainless steels.     

钢铁材料环境腐蚀野外台站试验技术与监测评估

介绍了国内外钢铁材料环境腐蚀试验技术发展的现状,总结了新型耐蚀钢铁材料研发中所需的各类试验方法,分析了室外暴露试验、室内模拟加速试验、在线腐蚀监检测与大数据评估技术的研究重点和发展趋势。鉴于钢铁材料自然环境腐蚀试验对保障其服役过程中的安全性和可靠性至关重要,构建规范化、标准化的环境腐蚀试验技术体系是提升我国钢铁材料品质的重要工作。