Edge defect analysis of high-strength corrosion-resistant steel

In this study, a 600 MPa hot-rolled corrosion-resistant steel plate produced by a specific company is investigated. Edge jagged defects and edge surface defects generated on both sides of the strip during production are characterized and analyzed. The results indicate that the distribution of reoxidation granules is located underneath the surface peel and that copper-containing granules diffuse along austenite grain boundaries. This phenomenon combined with the chemical composition and production parameters of a strip indicate that copper brittleness leads to edge jagged defects. However,the surface defects should be attributed to inherent defects on the surface of the strip. Measures that prevent surface oxidation and copper segregation at grain boundaries would likely eliminate these two types of edge defects.

耐候钢低成本生产工艺研究与实践

针对耐候钢生产工艺及成分设计特点,通过成本组成分析,对各工序低成本运行进行精准控制。介绍一种低成本生产控制工艺,通过目标成分的精准控制攻关、工艺路线优化调整、辅料料型搭配优化及耐候废钢定向回收利用等措施,通过在某厂120 t炉区生产实践验证,在保证质量稳定可靠的基础上,可有效地降低耐候钢炼钢生产成本。

10.9S级耐候钢螺栓在桑园子黄河大桥上的应用

检测了应用于桑园子黄河大桥的10.9S级耐候钢螺栓连接接头的力学性能和抗延迟断裂性能。对Q370qENH耐候桥梁钢板(被连接材料)和耐候钢螺栓进行了周期性浸润加速腐蚀试验,分析了锈层的形态和腐蚀产物的物相。结果表明:10.9S级耐候钢螺栓连接接头的力学性能满足国标要求,以0.85的加载系数恒载荷拉伸试验100 h的缺口试样未断裂,符合要求;耐候钢螺栓的耐蚀性能略优于Q370qENH耐候桥梁钢板,两者的相对腐蚀速率为6.1%,10.9S级耐候钢螺栓与被连接材料发生电偶腐蚀的风险较小。

Progress in corrosion-resistant coatings on surface of low alloy steel

Low alloy steels are widely used in bridges,construction,chemical and various equipment and metal components due to their low cost and excellent mechanical strength.Information in the literature related to the preparation,advantages and disadvantages,and applications along with research progress of various types of protective coatings suitable for low-alloy steel surfaces is reviewed,while a conclusive and comparative analysis is also afforded to the numerous factors influencing the protective ability of coatings.The characteristics of coatings drawn from the latest published literature are discussed and suggest that the modification of traditional metal coatings and the development of new organic coatings under the consideration of environmental protection,low cost,simplicity and large-scale industrial application are simultaneously proceeding,which holds promise for improving the understanding of corrosion protection in related fields and helps to address some of the limitations identified with more conventional coating techniques.

Some Advances in the Application of Weathering and Cold-Formed Steel in Transmission Tower

Application of weathering and cold-formed steel in transmission lines can reduce steel consumption and environmental pollution. Some advances in the studies on the weathering and cold-formed steel in transmission tower are introduced. Firstly, corrosion-resistant tests of weathering steel samples under different simulating technical atmospheres were carried out separately for 240 hours. It shows that the corrosion degree of joint samples is higher than that of single chip samples, and the corrosion-resistant performance of weathering steel is superior to common carbon steel. The corrosion-resistance of weathering steel meets with the requirement of transmission tower. Secondly, experiments and finite element analysis for cold-formed angles and a 220kV prototype tower were completed, and the stability coeffi-cient fitting curves as well as the modification formulas of slenderness ratio for cold-formed members were determined. According to the structural characteristics of transmission towers, four sections of cold-formed angles with different sections and slenderness ratios were selected in this study. The finite element model well predicted the buckling behav-iour of the cold-formed members. Ultimate loads calculating by the fitting curve were well agreed to the experimental values, especially for the members with small slenderness ratios. Weight of the cold-formed steel tower can be reduced by more than 5 percent after considering the strength enhancement. Cost of the weathering and cold-formed steel transmission tower is nearly equivalent to that of hot-rolled steel tower with hot galvanizing.

浅谈钢结构突出屋面设备洞口防水措施

为处理好设备占用建筑空间后留下的防水收口问题,论文结合实际项目中出现的问题进行了探讨,对钢结构屋面突出屋面设备洞口处理的理论做法与实际施工存在的差异进行了阐述,最后从经济方面、可实施性和防水效果方面做出了总结和建议。

耐火耐候钢在工业和海洋大气环境中的腐蚀行为研究

通过干湿交替腐蚀试验、扫描电镜和XRD等研究了耐火耐候钢在工业大气和海洋大气环境中的腐蚀行为。结果表明:耐火耐候钢在工业大气环境中的腐蚀速率低于海洋大气环境中的腐蚀速率,工业大气环境会促进耐火耐候钢锈层中α-FeOOH的生成,而海洋大气环境中形成的锈层中有β-FeOOH生成。在这两种大气环境中产生的锈层的形貌有差异,耐火耐候钢在不同大气环境中发生腐蚀的机制也不相同。

新型耐候桥梁钢的热处理与腐蚀行为研究

为了提升耐候桥梁钢的综合使用性能,开发了热轧态、退火态和正火态这3种不同状态的耐候桥梁钢,分析了不同状态耐候桥梁钢的显微组织、力学性能和耐腐蚀性能。结果表明•热轧态、退火态和正火态耐候桥梁钢的组织都由铁素体和珠光体组成,平均晶粒尺寸分别为15.81、12.76和10.95 pun;不同状态耐候桥梁钢的断后伸长率、屈强比和0°C冲击功较为接近,而退火态和正火态试样的抗拉强度和规定塑性延伸强度都要高于热轧态试样的。电化学阻抗谱与极化曲线测试结果保持一致,即热轧态试样具有最佳耐腐蚀性能,而正火态试样的耐腐蚀性能最差;热轧态、退火态和正火态耐候桥梁钢的年腐蚀速率分别为0.1022.0.1099和0.1148 mm/a,年腐蚀速率从大至小顺序:正火态〉退火态〉热轧态,失重腐蚀测试结果与电化学测试结果相吻合。

微量Nb、V对高强度耐候钢组织与性能的影响

对低碳的0.4Cu-0.07P-0.6Cr-0.3Ni高强度耐候钢分别添加0.026%Nb或0.073%V后,进行同一轧制工艺试验和正火处理,结果发现含Nb钢比含V钢塑韧性高但强度低,且组织更易发生岛状马氏体或粒状贝氏体转变。

经济型耐蚀耐候稀土钢的研制

简述了稀土元素在钢中的作用,在钢铁冶金中应用的物理化学基础,以及耐蚀耐候稀土钢工业化生产需解决的关键问题。稀土元素在钢中应用已取得了突破性进展,并试制了经济型耐蚀耐候稀土钢钢筋、热轧板卷等产品。稀土元素的收得率可稳定在70%以上,炼钢-连铸生产能顺利进行。耐蚀耐候稀土钢节约了合金元素加入量,降低了成本,耐蚀性显著优于不加稀土的同级别钢种。经济型耐蚀耐候稀土钢的研发及推广应用对解决我国轻稀土资源过剩及涂镀防腐造成的环境污染具有重要意义。

园林用耐候钢的开发

研制了两种不同成分的园林用耐大气腐蚀钢,其编号为A和B。A钢含0.13%C(质量分数,下同)、0.51%Cr和0.14%Ni,B钢含0.20%C、0.79%Cr和0.60%Ni。A钢的显微组织为条状、块状、针状铁素体和珠光体,B钢的显微组织为珠光体和贝氏体;B钢的强度高于A钢,但断后伸长率和0℃冲击吸收能量均低于A钢。开路电位、极化曲线和电化学阻抗谱测试结果表明:铬、镍含量较高的B钢耐腐蚀性能优于A钢,前者的平均腐蚀速率为0.0679 mm/a,后者为0.0870 mm/a,二者的腐蚀产物都主要由α-FeOOH、β-FeOOH、γ-FeOOH和Fe3O4组成,但B钢中Fe3O4更稳定、致密,其保护基体金属的作用更大。

桥梁钢的耐大气腐蚀性能研究

针对沿海地区大型钢桥建设对于桥梁钢耐大气腐蚀性的高要求,将以含有Cu、Ni抗腐蚀元素的耐候钢为研究对象,通过干湿周浸润加速腐蚀实验、失重分析、电化学测试等方法,分析海洋大气环境下桥梁钢的耐大气腐蚀性。实验结果表明:Cu、Ni含量不同的4种桥梁钢耐大气腐蚀性能存在一定差异,Cu、Ni合金元素可增强桥梁钢的耐腐蚀性、降低腐蚀深度与速率,且Cu含量与钢基体中的自腐蚀电位、极化电阻成正比,对于钢基体的初期腐蚀速率及大气腐蚀发展趋势均有显著减弱功能。

转向架轴箱垫片开裂原因分析

SPA-H耐候钢车用转向架轴箱垫片在使用中开裂。为确定垫片开裂的原因,采用Agilent 5110SVDV电感耦合等离子体发射光谱仪、CS800碳硫分析仪、光学显微镜和扫描电镜对开裂的垫片进行了化学成分分析、断口分析和金相检验。结果表明:垫片的化学成分和显微组织符合要求;垫片属于疲劳断裂,是不合理的悬空设计增大了振动力矩所致。

沙钢超薄带双辊铸轧工艺及超薄带耐候钢的发展现状

沙钢超薄带铸轧生产线是国内第一条,也是目前唯一实现了商业化运营的双辊连铸热轧薄钢带产线。作为一种近终成形技术,与传统热轧工艺相比,超薄带双辊铸轧工艺具有流程短、能耗低、排放少等优点,同时钢水在凝固过程中具有更高的冷却速率,在生产耐候钢等合金钢时,可大大降低合金元素的偏析程度,更易于形成性质均一的产品。沙钢超薄带耐候钢能够在相对较低的耐腐蚀元素添加量的前提下,达到甚至超越传统热轧耐候钢的性能。沙钢超薄带铸轧生产线能够以较低的成本生产高强度、优良耐蚀性的超薄热轧带钢,从而拓展了耐候钢的应用前景。

回火温度对NHL10耐候高强度螺栓钢组织和力学性能的影响

对NHL10耐候高强度螺栓钢进行了875℃水淬和400~650℃回火。检测了钢的显微组织和力学性能。结果表明:随着回火温度的升高,钢的显微组织由回火托氏体转变为回火索氏体,碳原子向马氏体板条边界聚集、球化;马氏体板条束的平均尺寸逐渐增大,大角度晶界数量增多,钢的屈服强度与马氏体板条束、板条块结构尺寸的-1/2次方呈线性关系。经875℃水淬和500℃回火的钢的力学性能满足10.9S级高强度螺栓的要求。

超高强度冷轧耐候马氏体钢的组织与性能

介绍了采用鞍钢常规喷气冷却连续退火机组试制一种冷轧超高强耐候马氏体钢的工艺流程,并使用金相显微镜、扫描电镜、透射电镜、X射线衍射仪及室温拉伸试验等手段对其显微组织和力学性能进行了表征。结果表明,试验钢组织由板条马氏体和少量残留奥氏体组成,马氏体有明显的分解现象,同时在马氏体基体中有大量弥散分布的渗碳体和碳化物析出。试验钢的综合力学性能良好,屈服强度可达1 039 MPa,抗拉强度达到1 131 MPa,断后伸长率A50为9.0%。通过微合金元素V和Ti的沉淀强化和细晶强化作用,试验钢的强度提高。

SPA-H高强度耐候钢的工艺实践

唐山不锈钢有限责任公司在SPA-H高强度耐候钢生产过程中,采用转炉冶炼、LF精炼、连铸等工艺,达到了钢材的质量要求。

屈服强度700 MPa级冷轧耐候双相钢的组织与性能

介绍了鞍钢连续退火机组试制屈服强度700 MPa级冷轧耐候双相钢的工艺流程,并对所研究钢板进行了力学性能测试和显微组织分析。结果表明,通过常规喷气冷却连退工艺处理,试验钢的屈服强度达到742 MPa,抗拉强度为952 MPa,断后伸长率为11.5%,屈强比为0.78。试验钢组织由铁素体和马氏体的双相细晶组织构成,铁素体位错密度较高,马氏体呈板条状,其体积分数约为65%,马氏体发生部分分解,回火过程中有一定量的合金渗碳体析出。通过微合金元素Nb和Ti的细晶强化和沉淀强化,提高了试验钢的强度。

国内外铁路车辆用耐候钢板发展现状

国外铁路车辆用耐候钢产品强度高、产品的配套解决方案完善,我国无论在耐候钢强度级别、产品质量以及推广应用上均与国外存在着一定的差距,因此急需加快研发高耐蚀性高强度耐候钢和低成本耐候钢。

耐候型膨胀钢结构防火涂料研究

选择丙烯酸树脂作为涂料的基料,以三聚氰胺包覆的聚磷酸铵代替普通聚磷酸铵,双季戊四醇代替季戊四醇,制备高耐候性能防火涂料。对比试验发现优化后涂料的耐水性能显著增加。通过正交试验,确定了涂料的基础配方。在涂料中添加紫外线吸收剂(Tinuvin 99-2)和受阻胺光稳定剂(Tinuvin 292),提高涂料耐光氧老化性能,并考查两种光稳定剂对涂料耐候性能的影响。结果表明:在一定添加量范围内,两种光稳定剂的添加对涂层的耐火时间影响不大。确定了耐候型防火涂料的最优配方,即添加2%的Tinuvin 99-2。红外测试表明,该配方可以有效降低涂料中丙烯酸、季戊四醇及三聚氰胺的光氧分解。