宝钢汽车排气系统用铁素体不锈钢产品开发

最近几年,随着对全球环境问题的关注,各国都对汽车尾气排放要求给予高度重视以减低对环境的危害。随着汽车燃油的经济性和汽车尾气排放的等级化要求不断提高,排放标准变得更为严厉。因铁素体不锈钢具有良好的耐氧化性、低的热膨胀系数、高的抗腐蚀性能及更为经济的成本,铁素体不锈钢更多用于汽车排气系统零部件。欧美及日本汽车几乎全部使用超纯铁素体不锈钢用于排气系统零部件制造以满足汽车轻量化及严格的尾气排放要求。介绍了汽车排气系统的构成、各部件的性能要求及宝钢汽车用不锈钢的产品开发。     

汽车排气系统用409型铁素体不锈钢的开发研究

描述汽车排气系统的结构及其对材料的特殊要求,介绍不锈钢分公司409型铁素体不锈钢的开发过程.该钢具有良好的高温性能、成形性及耐腐蚀性,可以较好地满足汽车排气系统用钢的需求.     

太钢汽车排气系统用铁素体不锈钢的开发

作为当今世界上最大的不锈钢生产企业,为适应汽车工业对节能及环保要求的提高。太钢充分利用生产不锈钢的独特优势,开发出系列的铁素体不锈钢,广泛应用在汽车排气系统各部件,产品质量得到用户认可,市场份额逐年增加。     

汽车排气系统用铁素体不锈钢的应用及腐蚀失效评价

最近几年,随着对全球环境问题的关注,汽车燃油的经济性和汽车尾气排放的等级化要求不断提高,铁素体不锈钢更多用于汽车排气系统零部件。铁素体不锈钢性能得到了明显改善,使铁素体不锈钢具有低的价格和良好性能,欧美及日本汽车几乎全部使用超纯铁素体不锈钢用于排气系统零部件制造。介绍了汽车排气系统的构成及对各部件常用不锈钢的性能要求、排气系统零部件的主要失效形式和所用不锈钢材料的腐蚀评价方法。     

汽车尾气排放系统低温端用铁素体不锈钢开发

随着汽车工业的快速发展,以降低汽车自身重量和提高材料性能为目的的材料开发,得到了汽车部件制造厂商的重视.铁素体不锈钢因不含有贵重金属镍,明显降低材料成本,同时,铁素体不锈钢又具有比奥氏体不锈钢更好的抗点蚀、晶间腐蚀等性能,广泛用于汽车尾气排放系统中.介绍了宝钢超低碳、氮Cr17Mo汽车尾气系统低温端用铁素体不锈钢的开发过程.该钢种具备良好的力学性能、成型性能及耐腐蚀性能,可以满足汽车排气系统冷端部位的中管、消声器和尾管的使用性能要求.     

新型汽车排气系统用铁素体不锈钢的冷凝液腐蚀

为了开发既经济又具有良好耐冷凝液腐蚀性能的汽车排气系统用不锈钢,采用冷凝液腐蚀试验方法,对一系列的铁素体不锈钢进行了10周期的腐蚀评价研究。研究结果表明:Cr当量高于17%的铁素体不锈钢与Cr的质量分数为17%的铁素体不锈钢耐冷凝液腐蚀性能相当,且平均腐蚀失重量均小于6 g/m2,平均最大腐蚀深度均小于0.03 mm。在此试验结果的基础上,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、10、20周期的冷凝液腐蚀试验,并使用极值分析方法对三种周期冷凝液腐蚀试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。     

Application and failure evaluation of ferritic stainless steels for automotive exhaust systems

In recent years,with attention paid to global environmental problems,there have been requirements for continuous improvement of automobile fuel economy and exhaust gas purification rate.The properties of the ferritic stainless steels(FSS) used to make automobile parts have been improved.This paper introduces the construction of automotive exhaust systems and describes their main failure behaviors and corrosion evaluation procedures.     

Development of ferritic stainless steel products at Baosteel

Ferritic stainless steel(FSS) for various applications was developed on the basis of Thermo-calc simulation.Alloy design,precipitate analysis and processing parameters optimization were carried out on the basis of the simulation results according to the technical requirements of the applications.These developed products have outstanding properties,such as mechanical strength,ductility,formability,weldability and corrosion resistance. Baosteel has formed a series of FSS products which will increase the profit of the company and enhance the product variety of stainless steel.     

The effect of Ti addition on equiaxed grain formation in ferritic stainless steel welds

This study examines mechanisms for providing nuclei to equiaxed grains in the welds of pure ferritic stainless steel(FSS).The addition of the alloy element Ti to pure FSS 439 causes the precipitation of TiN,which can benefit the columnar-to-equiaxed transition(CET) of gas tungsten arc welding(GTAW).Meanwhile,the initial morphology of the precipitates,the concentration multiplications of Ti,N,etc.of FSS 439 should be controlled to induce the formation of CET during the short welding process.     

Effects of tungsten on the oxidation resistance and high-temperature strength of 18CrNbTi ferritic stainless steel

18CrNbTi ferritic stainless steel is a low-cost material mainly used for the fabrication of manifolds,which usually work at temperatures below 950 ℃.With the development of engine technology,exhaust manifolds tend to work above 1 000 ℃ and this may be even higher in the future.For developing a new kind of steel to satisfy these requirements,the effects of tungsten(W) addition on the high-temperature strength and oxidation resistance of18 CrNbTi ferritic stainless steel are discussed in this study.The test results show that W enhances high-temperature strength at 1 000 ℃ and significantly improves oxidation resistance.However,W addition tends to degrade oxide layer adhesion,causing spalling during alternate hot and cold conditions.     

High performance ferritic stainless steel B445R for architectural applications

Traditionally,austenitic stainless steels 304 and 316 have been employed in coastal regions as roofing materials unfortunately,they are expensive and not fully resistant to pitting corrosion under severe coastal corrosive environment.A ferritic stainless steel B445R was developed.Compared with austenitic 316L,B445R is①less costly;②uperior corrosion resistant with minor maintenance for long-term service;③insusceptible to thermal distortion in the welding seam. B445R sheet shows a higher yield strength and lower tensile strength,lower elongation and lower work-hardening than austenitic 316L.It can be easily fabricated and deformed just like plain carbon steel.After bending 180o,there is no occurrence of "cracking" or noticeable "orange peel".The formability of the welding seam is also satisfactory.The pitting potential of B445R is 650 mV,larger than that of 304 and 316L,as shown in Fig.1. The corrosion rate of B445R submerged in 6%FeCl,solution is 0.3 -0.56 g/(m² ? h^-1),much lower than that of 316L,as shown in Fig.2.The superior pitting corrosion resistance of B445R can be ascribed to synergetic effect of higher Cr and Mo. Dull-finished B445R sheets have been employed as the roofing materials for Guangzhou Asian Games Arena,as shown in Fig.3.About 380 t of 1.0 mm B445R with dull finish was used for roofing panels.About 100 t of 0.8 mm B445R with hairline or fluororesin paint finish was used for side wall panels.The composite roof build-up （from up to bottom） includes:①shingles of ferritic stainless steel B445R;②Kalzip-type standing seam of austenitic 304;③water-proof DFM;④structural steel;⑤75 mm thick insulation;⑥secondary purlin of 150 mm×100 mm×4.5 mm of galvanizied Q235;⑦0.8 mm thick profile deck of galvanizied Q235;⑧acoustic insulation.The roofing shingles or panels with the same width but different length were formed by bending four sides and fixed to a "L" shape reinforcing frames of stainless steel by fasteners.The "L" frames was connected to ribs of the standing seam by a clamping fixture made of aluminum.     

退火温度对441铁素体不锈钢组织性能的影响

为探索超纯铁素体不锈钢热轧板材在退火过程中组织和力学性能的演变,对441进行了900～1 050 ℃的退火试验,利用OM、SEM和TEM表征了441在退火过程中显微组织的变化规律,并通过拉伸试验和冲击试验研究了退火温度对力学性能的影响.结果表明,随着退火温度升高,轧制组织发生再结晶,且晶粒逐渐长大.退火后441热轧板材...     

VOD冶炼超纯铁素体不锈钢脱碳脱氮

要利用VOD冶炼超纯铁素体不锈钢脱碳脱氮模型,研究了在吹氧脱碳阶段氧气利用率以及脱氮能力与初始碳含量的关系,分析了自由脱碳阶段的VOD脱碳和脱氮能力,并讨论了停氧后碳含量对脱碳以及温度控制的影响.研究结果为VOD冶炼超纯铁素体不锈钢合理脱碳脱氮提供技术指导.     

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）.     

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。