柳钢含铌钛及铌钒钛钢坯热塑性能研究

采用Gleeble-2000热模拟实验机测试了柳钢产铌钛及铌钒钛微合金钢的高温力学性能,两种钢的第Ⅲ脆性温度区分别为650℃～850℃和750℃～950℃,分析了裂纹敏感性及脆化机理,经生产实践后,提出减少铌钛及铌钒钛微合金钢铸坯角部横裂纹缺陷的措施。     

钛铌微合金钢连铸坯角部横裂纹敏感性

为明确不同速度冷却时表面奥氏体的长大规律和在第Ⅲ脆性区的热塑性,用Gleeble-3500热模拟机分别对钛铌微合金钢进行了奥氏体长大热模拟试验和第Ⅲ脆性区热拉伸试验。研究结果表明,当冷却速率小于5℃/s时,钛铌微合金钢铸坯表面容易形成粗大的(大于1mm)奥氏体晶粒;随着冷却速率的增大,奥氏体边界析出细小的Ti(C,N),能有效地钉扎限制奥氏体的长大。在热拉伸试验过程中,当冷却速率为1和5℃/s时,钛铌微合金钢铸坯在800℃热拉伸时断面收缩率仅为29.7%和23.0%,2种冷速下都伴随有70～200nm矩形或不规则形的(Ti,Nb)(C,N)和40～100nm针状的Nb(C,N)析出。铸坯角部振痕谷底处在高温低冷速下形成粗大奥氏体晶粒,并在第Ⅲ脆性区矫直,是导致钛铌微合金钢角部横裂纹敏感性高的主要原因。     

铌钒钛微合金钢连铸坯表面裂纹

采用多种分析手段,对武钢大生产中的几种铌钒钛微合金钢连铸坯表面裂纹的形成原因及影响因素进行了深入研究。并根据研究结果在生产中采取相应对策,使连铸坯表面质量得到改善。同时还在铸坯试样上预制不同深度的表面裂纹,通过模拟轧制试验,探讨了连铸坯表面裂纹对中厚板表面质量的影响。     

微合金钢薄板坯连铸边角裂纹控制

微合金钢薄板坯连铸过程高发边角部裂纹,致使热轧卷板边部产生翘皮、烂边等质量缺陷,是钢铁行业的共性技术难题。本文立足于某钢厂QStE380TM低碳含铌钛微合金钢薄板坯连铸生产,检测分析了铸坯角部组织金相结构与碳氮化物析出特点、不同冷却与变形速率条件下钢的断面收缩率,并数值仿真研究了不同结构结晶器和二冷区铸坯温度与应力的演变规律。结果表明:微合金钢薄板坯连铸过程存在明显的第三脆性区,且变形速率越大,第三脆性区越显著。传统薄板坯连铸工艺条件下,结晶器的中上部及其出口至液芯压下段的二冷高温区,铸坯角部冷速较低,致使其组织晶界含铌钛微合金碳氮化物呈链状析出。铸坯在液芯压下过程,低塑性角部因受较大变形与应力作用而引发裂纹缺陷。实施沿高度方向有效补偿坯壳凝固收缩的窄面高斯凹型曲面结晶器及其足辊区超强冷工艺,可分别提升铸坯角部冷速至10和20 ℃·s?1以上,从而促使铸坯角部组织碳氮化物弥散析出,并促进铸坯窄面在液芯压下过程金属宽展流动而降低角部压下应力,大幅降低了微合金钢薄板坯边角部裂纹发生率。      

浅谈低碳含铌钢铸坯裂纹形成原因分析与改进措施

文章通过运用多种显微镜和扫描电镜以及能谱分析仪等工具,针对低碳含铌钢铸坯表面产生的裂纹缺陷开展研究,仔细观察分析造成这一类缺陷的主要原因.经分析后结果显示,用于实验的钢碳含量0.09％～0.11％,且在1496℃时钢液出现包晶的反应,随着包晶的反应在体积方面出现较大的变化及线收缩,在坯壳的凹陷部位受到凝固的收缩及钢液静压力而导致微裂纹的产生.另外,受到铌和镍及铝等元素的影响而提升了铸坯脆性,并在后续矫直时受到应力的集中,及在脆性的温度区矫直也提高裂纹的增加,由此致使铸坯存在严重的裂纹缺陷.对出现的问题通过制定有效的控制措施才能提高铸坯的质量,其对生产具有非常重要的作用和意义.     

微钛固氮降低含铌钢皮下裂纹敏感性的机理

 降低含铌低合金钢铸坯的裂纹敏感性,是实现热装热送工艺的必要条件,采用超高温激光共聚焦显微镜(HT-CLSM)、透射电镜(TEM)等手段研究了钛含量不同的含铌低合金钢(Q390、Q390GJD)高温铸坯的晶粒度及析出物特征,旨在揭示微钛固氮降低含铌钢皮下裂纹敏感性的机理。热力学计算与TEM检测结果表明,增加钢中钛质量分数(由0.010%上升到0.023%)提高了氮化钛粒子的析出温度(大于1 400 ℃),高温析出细小弥散的氮化钛粒子可钉扎奥氏体晶界,细化高温铸坯的晶粒度(由4级变成6.5级),晶粒尺寸降低了约44%,使高温铸坯的裂纹敏感性明显降低;氮化钛粒子优先析出固氮降低了铌碳氮化物、氮化铝的开始析出温度,并作为异质形核核心,抑制了铌、铝析出物在晶界析出概率,降低了析出物脆化晶界的危害。通过微钛固氮调控氮化物的析出温度、析出位置及细化晶粒的作用,有效降低了含铌钢第三脆性温度槽的宽度和深度,同时,高温抗拉强度提高了21.3%~27.5%,铸坯皮下裂纹发生率降低了80%以上。为了避免析出物的晶界链状析出导致含铌钢铸坯热装轧制裂纹,应将其钛质量分数控制在0.015%~0.020%的合理范围。     

含铌微合金钢表面微裂纹产生机理分析

通过对缺陷钢板及对应铸坯进行取样,利用光学显微镜、扫描电镜和透射电镜对缺陷组织及成分进行分析,确定了含铌微合金钢表面微裂纹缺陷产生的原因。     

连铸含铌钢板坯表面横裂纹原因分析和措施

通过对邯钢三炼钢厂板坯连铸生产高强度船板用等铌微合金钢,铸坯发生表面横裂纹的机理分析,讨论了铸坯表面横裂纹产生的影响因素,并提出了连铸解决含铌钢表面横裂纹的有效措施。     

铌-钛微合金化中碳硼钢连铸坯的高温力学性能

为了避免或减少铌-钛微合金化中碳硼钢320mm×280mm铸坯(%/:0.35C,0.04Si,0.87Mn,0.010P,0.007S,0.27Cr,0.031Alt,0.03Nb,0.030Ti,0.0018B,0.0046N)表面裂纹,研究了该钢种连铸坯的高温力学性能,并对高温拉伸断口和断口附近显微组织进行了观察。结果表明:在600～1250℃,试验钢在600℃时的断面收缩率为54.4%,其它测试温度点的断面收缩率均高于60%;试验钢第Ⅰ脆性区; 1200℃,第Ⅲ脆性区在750～850℃,在850～1200℃试验钢具有良好的热塑性;试验钢在800℃时具有相对偏低塑性,但拉伸断口微观下仍以韧窝形貌为主;试验钢在实际连铸生产时,采用≤1.0m/min铸速和≥950℃矫直温度,连铸坯表面质量良好。     

铌微合金化异型坯高温热塑性的研究

针对铌微合金化异型坯S355ML钢存在翼缘裂纹缺陷问题,采用扫描电镜和光学显微镜分析了铸坯缺陷处组织以及断口形貌,并研究了异型坯的断面收缩率、抗拉强度等高温性能.结果表明:在1×10-3 s-1应变速率下,第Ⅲ脆性区间为700～950℃,随着第Ⅲ脆性区断口处α铁素体析出量的增加,该钢种的塑性先减小后增大,测试温度为85...     

China's Major Non-ferrous Metals Imports & Exports

正~~     

Zinc Production by Province in 2014

正~~     

80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.