20G和12Cr1MoVG无缝钢管低温形变退火研究

研究了低温形变退火生产的20G、12Cr1MoVG热扩无缝钢管的显微组织、晶粒度、非金属夹杂物和室温力学性能,参考GB5310-2008对试验结果进行了评价,并与原管和热扩后经后续热处理的钢管比较。结果表明,低温形变退火生产的20G、12Cr1MoVG热扩无缝钢管和经后续热处理钢管的显微组织、晶粒度、非金属夹杂物和室温力学性能,均符合GB5310-2008对20G、12Cr1MoVG的要求。这为进一步推广生产流程简单、质量稳定、经济实用的热扩工艺奠定重要基础。     

厚壁12Cr1MoVG高压锅炉管热处理工艺优化研究

通过对现有经热处理工艺热处理后的12Cr1MoVG高压锅炉管的力学性能不合格情况进行统计分析,指出热处理生产的难点,提出一种"间歇式淬火+回火"热处理工艺。分析认为:控制正火后的冷却速度,使厚壁12Cr1MoVG高压锅炉管的组织以铁素体+贝氏体为主,是保证其具有良好综合力学性能的关键。大生产应用结果表明,采用"间歇式淬火+回火"热处理工艺,完全能生产出满足GB/T 5310—2017标准和用户要求的12Cr1MoVG高压锅炉管。     

锅炉管爆裂原因分析

锅炉管在使用1年后,发生爆裂。管的工作环境:管内压力9.8MPa,温度540℃。经过扫描电镜分析、 金相显微镜分析、化学成分检测和力学性能试验,结果表明,该锅炉生产厂错将20G钢当12Cr1MoVG钢使用,由于20G钢抗高温蠕变性能比12Cr1MoVG钢低,加之锅炉管运行时超温,管壁金属长期过热运行,导致高温蠕变加速,强度下降,最终发生早期蠕变爆裂。     

12Cr1MoV轧材表面裂纹原因分析及探讨

12Cr1MoV管坯钢常用于锅炉管钢,莱钢特钢事业部生产初期出现表面裂纹现象。通过对轧材表面裂纹缺陷部位进行金相组织观察、扫描电镜分析,发现裂纹附近组织存在明显的脱碳现象及夹杂物和氧化物圆点,并且裂纹末端存在多条铁素体条带,结果表明连铸坯本身存在的质量缺陷是12Cr1Mo V圆钢产生表面裂纹的主要原因。     

12Cr1MoVG大直径高压锅炉管适应新标准的工艺技术优化

介绍按GB 5310—2008标准生产的12Cr1MoVG大直径高压锅炉管的热处理生产工艺数据,对全壁厚大直径高压锅炉管试样进行热处理正交试验,分析影响12Cr1MoVG大直径高压锅炉管硬度指标的因素。分析认为:新版GB/T 5310—2017将表面硬度列入验收条件,大大增加了热处理难度;影响表面硬度的主次因素依次为回火温度、回火保温时间、淬火冷却方式、修磨深度;应根据实际生产条件,对生产数据进行统计分析,找出规律,不断优化热处理参数。     

国内外不同H13钢冶金质量及性能对比分析

针对国产H13钢使用性能明显低于国外同类优质钢的现状,利用金相显微镜、扫描电镜和能谱分析等方法研究了国内外5种H13模具钢的成分、力学性能、非金属夹杂物和显微组织。利用Thermal-calc软件,计算了试验钢中温度与析出相之间的关系。结果表明:国产H13钢中的S、N和O元素含量远高于国外钢种,钢中氧化物、硫化物以及Ti N类夹杂物的数量多、尺寸大且析出温度更高。国产钢中出现的VC-CrC类大块状夹杂物和一次共晶碳化物是导致钢材性能下降的主要原因。得出了降低国产H13钢中的N及O元素含量,同时加强电渣重熔和高温均匀化处理和锻造工艺优化的研究,成为改善国产H13钢性能的主要途径。     

低碳铸钢丸中的夹杂物分析

采用扫描电镜和能谱分析研究了低碳铸钢丸中的夹杂物形貌和组成,并分析了其形成机理和去除途径。结果表明,低碳铸钢丸中存在的夹杂物主要有球形的多元复合氧化物夹杂物,分布在枝晶间的不规则形状的硫化铁和磷化铁二元复合夹杂物以及带尖角的磷化铁、硫化铁和碳化铁的三元复合夹杂物。夹杂物的存在与脱氧不充分和硫、磷含量偏高有关。通过稀土复合脱氧和深度脱磷、脱硫可以显著降低夹杂物的水平。     

控制终扩温度生产高压锅炉管的工艺试验研究

通过在热扩机组上采用控制终扩温度代替正火处理,或控制终扩温度代替正火+离线回火处理工艺,生产20G和12Cr1MoVG钢高压锅炉管的试验研究证明,根据产品的规格和品种,合理制定终扩温度和扩制道次能够达到以控制终扩温度代替正火的目的,按此工艺生产的20G和12Cr1MoVG钢高压锅炉管的各项常温性能指标能够满足GB5310-1995标准要求,解决了大直径中厚壁(壁厚≤20mm)钢管热处理后变形的问题。     

索氏体化率及夹杂物对82B盘条力学性能的影响

通过成分分析、金相观察、夹杂物形貌观察、能谱分析及拉伸断口分析,研究了82B盘条的索氏体化程度与夹杂物的类型及尺寸对其力学性能的影响。结果表明:82B盘条试样室温组织主要是索氏体与少量先共析铁素体,且索氏体含量均高于80%。索氏体化率低是影响82B盘条的抗拉强度、断面收缩率主要因素。随着索氏体化率增加,82B盘条的抗拉强度也相应增高,而断面收缩率也逐渐增大。82B盘条中的夹杂物主要是氧化物夹杂,且氧化物夹杂主要是Al_2O_3、Si O_2、Ca O和Cr O。夹杂物尺寸主要集中在0~20μm,较大尺寸的夹杂物含量较高时,主要对82B盘条断面收缩率的影响较大,并呈显著降低的趋势;而大尺寸的夹杂物对抗拉强度的影响较小。82B盘条拉伸断口属于韧性断裂,主要是剪切唇区和纤维区。纤维区夹杂物主要为氧化物,如Al_2O_3、Ca O,其晶粒尺寸为31.8μm。     

生物质锅炉过热器用钢在混合碱金属熔盐中的电化学腐蚀行为

以过热器12Cr1MoV钢为研究对象,在不同的混合碱金属熔盐中开展电化学腐蚀试验。结果表明：12Cr1MoVG钢在600、700 ℃ KCl+NaCl熔盐腐蚀环境下的电化学阻抗谱表现出双容抗特征;电化学反应时间越长,阻抗谱的高频端阻抗值越大;在600 ℃条件下的阻抗值高于700 ℃下的阻抗值,随着温度的升高,12Cr1MoVG钢的腐蚀速率更大;在混合熔盐中12Cr1MoVG合金整体的腐蚀速率大小顺序为。     

Reduction in area and appearance of hydrogen-assisted fracture surfaces of cathodically charged differnt Low-alloy sulphur containing steels

The present work is concerned with the role of sulphidic inclusions in hydrogen-assisted cracking of low-alloy steels with different sulphur contents. The steels were previously cathodically charged in sulphuric acid solution. Evaluating the susceptibility to hydrogen-assisted cracking in terms of the reduction in area values, the high sulphur steel is less susceptible than the low sulphur steel. The fracture surface of the low sulphur steel appears rather brittle, with local quasi-cleavage fractures around large intergranular fracture facets. In contrast, the fracture surface of the high sulphur steel is characterized predominantly by the microvoid coalescence mode, with a great number of manganese sulphide inclusions. The difference between the two sulphur steels is based upon the concept that the interfaces between sulphidic inclusions and matrix act as trapping sites for hydrogen and thus hydrogen is uniformly distributed over the sulphidic inclusions.     

X120钢级螺旋缝埋弧焊管研制结果及分析

X120钢级管线管是目前国际上研发的最高钢级的管线管。介绍了渤海装备公司华油钢管有限公司研制开发X120钢级螺旋缝埋弧焊管的结果。通过金相组织分析及各项试验表明,所研制钢管的性能满足APISpec5L标准(44版)的要求,安全性高,但屈服强度偏高,夏比冲击功偏低。针对存在的不足,提出了降低钢带屈服强度,提高卷曲温度,适当降低钢中B、Mo和Ni合金元素含量,以及降低钢的碳当量等建议。     

Cover Picture: Materials and Corrosion. 6/2020

Cover: Three types of oxide inclusions are contained in the steel. Al-Si-Ca-O and Al-Mg-Si-Ca-O inclusions are more electrochemically active than the steel, and pitting corrosion occurs on both inclusions. α phase has a higher electrochemical activity and a lower corrosion resistance than γ phase. Pitting corrosion is more likely to occur at the inclusion/α phase interface, rather than the inclusion/γ phase interface. More detailed information can be found in: Yaohua Zhang, Qian Hu, Mingjie Dai, Feng Huang, Y. Frank Cheng, Jing Liu, Investigation of microelectrochemical activities of oxide inclusions and micro-phases in duplex stainless steel and the implication on pitting corrosion, Materials and Corrosion 2020 , 71, 876.     

Investigation of micro-electrochemical activities of oxide inclusions and microphases in duplex stainless steel and the implication on pitting corrosion

In this study, the oxide inclusions contained in the 2205 duplex stainless steel were characterized, and the pitting corrosion initiated at the inclusions was statistically analyzed. The micro-electrochemical behavior was measured by a home-designed capillary microelectrode technique. Results show that three types of oxide inclusions are contained in the steel, namely, Al–Mg–O (inclusion A), Al–Si–Ca–O (inclusion B), and Al–Mg–Si–Ca–O (inclusion C) inclusions. Inclusion A possesses higher electrochemical stability than the steel substrate, and there is no corrosion pit initiated on the inclusion. Inclusions B and C are more electrochemically active than the steel, and pitting corrosion occurs on both inclusions. The α phase has higher electrochemical activity and lower corrosion resistance than the γ phase. Pitting corrosion is more likely to occur at the inclusion/α phase interface, rather than the inclusion/γ phase interface. When the inclusion is located at the α/γ interface, the pit initiation is dominated by the α phase on the coexisting dual phases.     

Influences of Contents and Reaction of Carbon and Oxygen on Microstructure and Mechanical Properties of Sintered 93W-4.6Ni-1.9Fe-0.5Co Alloys

采用具有不同碳氧含量的初始粉末,利用真空液相烧结制备93W-4.6Ni-1.9Fe-0.5Co合金试样,研究碳氧含量的变化及其平衡反应对合金力学性能与组织的影响。结果表明,压坯在真空高温烧结过程中,原料自身含有的碳具有较强的脱氧能力,通过碳氧反应可减少合金中的氧、碳含量,阻止氧化物、碳化物夹杂的生成,在钨颗粒与粘接相之间形成牢固的界面。当合金总氧含量低于500μg/g时,合金的力学性能显著提高。     

Characterization of protective rust on ancient Indian iron using microprobe analyses

Local compositional and structural information was obtained from an ancient 1500-year-old Indian iron and its protective scale utilizing microprobe techniques (μXRD and μPIXE). Different locations in the iron matrix and in the entrapped slag inclusions were also analyzed for P contents. The P content of the metallic iron matrix was very heterogeneous. Lower P contents were observed in the regions near slag inclusions. The surface oxide scales was layered. Enrichment of P in the metal-scale interface and in the scale adjacent to the interface was determined. The P content in the scale decreased on moving away from the interface. Microdiffraction patterns obtained at different locations in the oxide scale indicated that at locations where the P content was high (i.e. nearer the interface), the oxide was amorphous while at locations where P was low, crystalline phases were identified. The presence of crystalline phosphates was also confirmed at some regions in the scale, where the P content was relatively very high. The probable reasons for the presence of the identified phases in the atmospheric corrosion product have been discussed.     

Grain refinement in coarse-grained heat-affected zone of Al–Ti–Mg complex deoxidised steel

The particles and microstructure characteristics of coarse-grained heat-affected zone (CGHAZ) in Al–Ti–Mg killed steels with different Al contents were investigated. The results show that inclusion in high Al steel consists of Al–Mg oxide surrounded with a layer of MnS. However, inclusion in low Al steel is Al–Ti–Mg oxide covered with a layer of MnS, effectively promoting the formation of acicular ferrite. The precipitates of both steels are (Ti, Nb)N, the finer and more dispersed inclusions and precipitates in low Al steel can effectively inhibit austenite grain growth by grain boundary pinning during the thermal cycle. The fine-grained microstructure is obtained in CGHAZ of the low Al steel due to the pinning effect of finer particles and the high density of acicular ferrite.     

Impressions and Conclusions of the Conference on Mechanical Properties and adherence of scale layers and their influence on the oxidation of metals

Review of the papers presented to the Conference and of discussions. The topics dealt with included the various ways in which growing oxide scales can deform to accommodate their growth stresses. According to that plastic deformation occurs by the following mechanisms: dislocation glide, dislocation climb, Herring-Nabarro stress-assisted diffusion creep, grain-boundary sliding, mechanical twinning and viscous flow of amorphous oxides. The deformation depends on the scale configuration and the stress system; many oxide systems are rather plastic at high temperatures, but pores, defect doping elements and second phase inclusions play important parts, too. It is generally accepted that the evidence for some plastic deformation in growing oxide scales is very strong, the most favoured mechanism at high temperatures being diffusion controlled creep associated with grain boundary sliding. Factors influencing adhesion of scales include electrostatic forces at the metalloxide interface, interface irregularities, stress/strain interactions between oxide and metal, stress relaxation in metal and oxide, and the presence of stress raisers such as voids, second phase particles and pores at the metal/oxide interface. The necessity of developing new measuring methods is pointed out, too.     

QUALITY OF LADLE-DEOXIDIZED RAIL STEEL

<正> 平炉碳素镇钢的脱氧操作有许多不同方式,但主要由于近代钢种的化学成分范围规定很严,为了较有把握地控制成品成分不使出格,目前各国大多数工厂都采用着某种形式的炉内脱氧,就是说,将一部分脱氧剂在出钢以前加入炉内.1955年苏联平炉熔炼标准技术规程就是为此而规定了部分炉内脱氧的.但炉内脱氧引起脱氧剂消耗的增大和熔炼时间的延长.如果炼钢工的技术熟练程度足能保证得到规定的化学成分,而且如果缶内脱氧不致使产品质量降低的话,那末将全部脱氧剂加入缶内当然是一个更为合理的方法。近年来缶内脱氧在苏联得到了相当大的重     

稀土氧化物对焊缝微观组织和性能的影响及作用机理

研究了稀土添加剂氧化钇对焊缝微观组织、化学成分以及焊缝金属力学性能的影响,并分析了氧化钇的作用机制.试验研究结果表明,氧化钇对细化焊缝组织、改善夹杂物形状和分布状态、降低熔敷金属中硫含量和扩散氢含量以及提高焊缝金属低温冲击性能等方面具有明显作用.