Corrosion Resistance on High Strength Bainitic Steel and 09CuPCrNi After Wet-Dry Cyclic Conditions

The accelerated wet-dry cyclic corrosion tests have been carried out of a high strength bainitic steel and 09CuPCrNi. The results indicated that the corrosion resistance of 09CuPCrNi was better than that of the bainitic steel based on the mass loss measurements. The morphology and composition of the rusting products have been investigated in order to realize the mechanism of rust formation on the two steels. The rust scale on both steels was composed of a dense inner layer and a loose outer layer. The inner layer grew thicker and denser as the test proceeding. Both of inner and outer layers were mainly composed of magnetite (Fe3O4) and maghemite (γ-Fe2O3) with a small amount of lepidocrocite (γ-FeOOH) and akaganeite (β-FeOOH). The rust phase of γ-Fe2O3 was detected in a higher amount of the inner layer, resulting in a much denser inner layer. The inner rust layer of 09CuPCrNi being denser and thicker than that of the high strength bainitic steel was attributed to the alloying elements such as copper, chromium and phosphorus enriched in it. The protective inner rust layer plays an important role in the corrosion resistance of the steel.     

Corrosion Resistance of High Performance Weathering Steel for Bridge Building Applications

 The mechanical properties, corrosion resistance and microstructures of high performance steel (HPS) was investigated by tensile testing machine, Charpy V-Notch (CVN) testing machine, cyclic immersion corrosion tester, XRD, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe micro-analyzer (EPMA). The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was composed of α-FeOOH phase and denser than that on PCS that was a mixture of α-FeOOH and Fe3O4. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS enrich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.     

Effect of Microalloying Additions on the Microstructure and Mechanical Properties of Low Carbon Steel

Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decrea     

Microstructures and Properties of X60 Grade Pipeline Strip Steel in CSP Plant

The microstructures and properties of X60 grade pipeline strip steel were researched.With Nb microalloying and TMCP,the X60 grade pipeline strip steel was developed in the Baotou CSP Plant.The mechanical properties meet the demands on machining and using of pipeline manufacture.The X60 strip steels had been used extensively,which had fine and uniform structures,good performance and excellent toughness.     

Development of 340MPa Grade Galvanized Automotive HSLA Sheet of Shougang

In the paper,development of 340MPa galvanized grade HSLA sheet of Shougang is introduced.The effects of annealing parameters on the precipitates,microstructures and mechanical properties were investigated.According to the experiment,it was indicated that the fine microstructures and disperse carbide of Nb caused high strength of the steel.And now,the product has been used to the reinforced inner panel.     

Influence of Alloying Elements Corrosion Resistance of Cold on Mechanical Properties and Rolled C-Mn-Si TRIP Steels

 The rust layer plays an important role in the corrosion of steel in chlorinated environments. Salt spray, potentiodynamic polarization curve and tensile test were conducted in laboratory for the specimens after two-stage heat treatment. The influence of the alloying elements on mechanical properties and corrosion resistance of three kinds of steels was investigated by observing the microstructure and the morphologies of rust layer. The results show that the highest value (29%) of total elongation for steel A is obtained. The mechanical property of the specimen for steel C exhibits best strength ductility balance (21384 MPa·%) because of the presence of the multiphase microstructures after a two-stage heat treatment and the addition of the alloying elements. The corrosion products are known to be a complex mixture of Fe3O4, Fe2O3 and α-FeOOH for steel C. The presence of the alloying elements results in the formation of compact and dense rust layers in steel B and C. Passive film protects the substrate of TRIP (transformation induced plasticity) steel containing a complex mix of multiphase. Superior corrosion performance is exhibited for steel C with low alloying contents due to the enrichment of alloying elements within the rust layers.     

Effect of Nb on Microstructure and Mechanical Properties in Non-magnetic High Manganese Steel

Microstructure and mechanical properties of two kinds of non-magnetic high manganese steels with and without Nb addition which experienced the same rolling and heating treatment were investigated by means of scanning electron microscopy,electron back-scattered diffraction,transmission electron microscopy,X-ray diffraction and tensile test.It was found that the microstructure of the high manganese steel was refined by the Nb addition.Moreover,steel with Nb addition has a higher stacking fault energy which favors the deformation twinning.Twinning is the most important deformation mechanism in the Nb-bearing steel.Therefore,steel with Nb addition has much higher strength and higher plasticity.The product of tensile strength and total elongation exceeds 61.8 GPa·%.In addition,steel with Nb addition also has excellent non-magnetic property.     

Effects of Rolling Processes on Bainite and Mechanical Properties of Ultra-High Strength Pipeline Steel

Ultra-high strength pipeline steels were rolled by thermal mechanical controlling process (TMCP),and effects of the volume fraction,the size and microstructure morphologies of three different bainite (AF,GB and LB) on mechanical properties were investigated by optical microscope.The results showed that,X120 ultra-high strength pipeline steel was rolled through the reasonable thermal mechanical controlling process (TMCP),and the yield strength and the low temperature charpy impact energy (-30℃) were higher than 840MPa and above 230J,respectively,meanwhile,the ratios of tensile strength to yield strength were lower below 0.82.As for X100 pipeline,of which the mechanical property were higher than that by X100 pipeline steel of ISO standard,yield strength of the steel was 715 MPa,ultimate tensile strength 963 MPa,impact energy 282J,and yield ratio 0.74.     

A New Series of Mo-free 215Cr-35Ni-xW-02N Economical Duplex Stainless Steels

A new series of economical Mo-free duplex stainless steels 21.5Cr-3.5Ni-xW-0.2N(x=1.8-3.0,mass%) have been developed.The effects of W on mechanical properties and corrosion resistance were investigated,and the microstructures were analyzed by optical microscopy,X-ray diffraction,transmission electron microscopy and electron backscatter diffraction.The designed steels have a balanced ferrite-austenite relation and are free of sigma phase after solution treatment at 750-1 300℃for 30min followed by water-quenching,whereas a small number of Cr23 C6 precipitates were found after solution treatment at 750℃.After solution treatment at 1 050℃,the steel with 1.8%(mass percent)W exhibits the highest room temperature tensile strength due to the strongest work hardening effect, while the steel with 3.0%(mass percent)W exhibits the highest fracture elongation owing to the transformation-induced plasticity(TRIP)effect.The ductile-brittle transition(DBT)and martensite transformation are respectively found in the ferrite and austenite,which deteriorates the impact properties of the steels with the increase of W content.The corrosion resistance of the designed steels is improved with the increase of W content.The pitting resistance of austenite is obviously better than that of ferrite for the designed alloys.Among the designed steels,the steel with 1.8%(mass percent)W is found to be an optimum steel with excellent comprehensive properties and lowest production cost.     

Corrosion Behavior of S450EW Low-alloy Weathering Steel in Cyclically Alternate Corrosion Environments

Weathering steel is widely used in various fields due to its excellent mechanical properties and high corrosion resistance. The effect of chromium content on the S450 EW weathering steel in cyclic immersion test was studied. The results indicated that the corrosion resistance of S450 EW weathering steel is closely related to chromium content. The addition of chromium significantly inhibited the weathering steel corrosion. The corrosion rate of experimental steel after 96 h immersion was 1.101 g·m-2·h-1. The rust of S450 EW weathering steel was mainly constituted of Fe OOH and Fe3O4 phase, and the elevation of chromium content promoted the formation of α-Fe OOH. The fine precipitates of the two phases contributed to the formation of dense dust layer of test steel. Furthermore, the increase of chromium is beneficial for the cure of original defects and cracks of the rust layer via the enrichment of chromium. The corrosion potential and the resistance of corrosion process were thus increased, protecting the experimental steel from further corrosion. A S450 EW steel with corrosion resistance more than 1.5 times of Q450NQR1 steel was prepared.     

Corrosion Behavior of 110S Tube Steel in Environments of High H2S and CO2 Content

 The corrosion behavior of the 110S tube steel in the environments of high H2S and CO2 content was investigated by using a high-temperature and high-pressure autoclave, and the corrosion products were characterized by scanning electron microscopy and X-ray diffraction technique. The results showed that all of the corrosion products under the test conditions mainly consisted of different types of iron sulfides such as pyrrhotite of Fe0. 95S, mackinawite of FeS0. 9, Fe0. 985S and FeS, and the absence of iron carbonate in the corrosion scales indicated that the corrosion process was controlled by H2S corrosion. The corrosion rate of the 110S steel decreased firstly and then increased with the rising of temperature. The minimum corrosion rate occurred at 110 ℃. When the H2S partial pressure PH2S below 9 MPa, the corrosion rate declined with the increase of PH2S. While over 9 MPa, a higher PH2S resulted in a faster corrosion process. With the increasing of the CO2 partial pressure, the corrosion rate had an increasing trend. The morphologies of the corrosion scales had a good accordance with the corrosion rates.     

低合金耐海水腐蚀钢的开发

 设计、冶炼了Cu-Mo和Cu-Mo-Cr系的3种成分的耐海水腐蚀钢,并轧制成20mm厚钢板,然后测试了设计钢种的力学性能、耐海水腐蚀性能及焊接性能。96,240,336和500h盐雾加速腐蚀试验结果表明：与普通碳素钢（SM490A）相比,3种设计钢的耐海水腐蚀性能均有明显提高,且随着腐蚀时间的延长优势更明显。设计钢种的耐腐蚀性能随Cr含量增加而增加,当Cr质量分数为0.85%时,耐腐蚀性能比对比钢提高59.1%。Cr元素在内锈层的均匀富集有效阻碍了Cl-的侵蚀,提高了耐腐蚀性能。Gleeble热模拟结果表明：不预热和焊后热处理,在焊后冷却速度为5~60℃/s时,焊接粗晶区的KV≥57J,揭示了设计钢种良好的焊接性能。     

油管钢高温高压CO2腐蚀行为研究

在高温高压条件下，对P110，N80，J55三种油管钢在模拟油田CO2环境下的腐蚀性能进行了研究评价，结果表明：在静态条件下，三种钢对温度和压力的依赖关系均为类似抛物线规律，P110最不耐蚀，动态条件下对P110钢的进一步研究显示，由于流速的存在，与静态下相比，最高均匀腐蚀速率点向温度和CO2分压升高的方向移动。     

低碳中铬钢在模拟CO2-EOR环境下的腐蚀行为

 为了研究Cr5和Cr7(质量分数/%)钢在CO₂-EOR高温高压服役条件下的腐蚀机理,利用高温高压反应釜模拟其腐蚀行为,使用失重法测定了腐蚀速率,采用SEM、EDS、XRD和XPS等手段对腐蚀产物进行了观察与分析,探讨了试验钢在CO₂条件下的腐蚀机理,并提出了腐蚀模型。研究结果表明,Cr5钢的腐蚀速率为0.734 75 mm/a,Cr7钢的腐蚀速度为0.217 32 mm/a;腐蚀产物均由外层的FeCO₃晶体以及内层的非晶态FeCO₃和Cr(OH)₃组成;腐蚀初期,产物膜以原位形成和阳极溶解后逐渐沉积两种途径生成;产物完全覆盖基体后,离子在界面处的扩散后沉积成为产物膜生长的主要途径。     

高耐候结构用Q355GNH钢的开发与性能研究

通过对高耐候钢产品的性能要求分析,本试验钢在成分设计上以Cu、P为基,添加少量Cr、Ni,并制定相应的轧制及卷取工艺而成功开发了355强度级别的高耐候结构用钢.对该试验钢的各项性能进行检测,同时根据其成分设计进行了耐腐蚀性能预测,并利用实验室加速腐蚀试验方法对Q355GNH试验钢及Q345B对比钢的腐蚀速率以及其锈层构...     

Cr对低合金钢在流动NaCl溶液中耐蚀性的影响

对碳钢和Cr含量不同的实验钢在流速为0.8m/s的流动的3.5％(质量分数)NaCl溶液中的腐蚀行为进行研究,最长腐蚀周期为192h.对4种实验钢的腐蚀失重进行了比较,并利用动电位极化曲线、SEM、EPMA和TEM等分析手段,对实验钢表面形成锈层的特征进行了系统研究.结果表明,含Cr实验钢的腐蚀失重低于碳钢,并且随Cr的质量分数由0.5％提高至2％,腐蚀失重亦降低.Cr元素在内锈层中的富集是含Cr钢耐蚀性改善的重要原因.这种富集可使腐蚀产物颗粒获得细小的尺寸,致密内锈层形成的原因就是由于这种尺寸细小的腐蚀产物的形成,使内锈层的保护性获得明显的改善.     

Study on the corrosion properties of 0Cr11 ferritic stainless steel for automotive exhaust systems

This study investigates the corrosion properties of 0Cr11Ti and 0Cr11NbTi ferritic stainless steels(FSS) for automotive exhaust systems.The results indicate that the base metal and weld seam of 0Cr11NbTi steel exhibit better intergranular and condensate corrosion resistant properties because carbon and nitrogen are stabilized by Nb and Ti,and the precipitation of Cr carbide is retarded in grain boundaries.