新标09CrCuSb耐酸钢的耐50%H_(2)SO_(4)腐蚀性能

通过电化学测试和全浸腐蚀试验,研究了不同温度(25,50,60,70℃)条件下新标09CrCuSb耐酸钢在50%H_(2)SO_(4)溶液中的腐蚀行为。结果表明:随着温度从25℃升至70℃,新标09CrCuSb钢的腐蚀速率整体呈现增大趋势,在70℃时,腐蚀速率达到最高,为2.70 g/(m^(2)·h),这与随温度升高,腐蚀产物中具有保护性作用的Fe_(3)O_(4)含量减少,无保护作用的FeSO_(4)·H_(2)O含量增加以及锈层中微孔变化有关。另外,由于新标调整了09CrCuSb钢中Cu、Mo、Sn、Sb、W等元素的含量,与旧标09CrCuSb钢相比,阳极维钝电流密度J维钝降低,同等温度条件下,新标09CrCuSb钢的耐蚀性得到较大改善。

High Temperature Behavior of Isothermally Compressed M50 Steel

The isothermal compression of M50 steel is carried out on a Gleeble-3500 thermo-mechanical simulator in temperature range of 1 223-1 423 K and strain rates range of 10-70 s^-1. The results show that the carbides play a significant role in the flow behavior and microstructure evolution during isothermal compression of M50 steel. The average apparent activation energy for deformation in isothermal compression of M50 steel is （281.1±42.6） kJ·mol^-1 at the strains of 0.4-0.8. The dynamic recrystallization of austenite grains occurs in isothermal compression of M50 steel at 1 363 K and 1 393 K, enhancing with the increase of strain rate and/or strain. The volume fraction of the carbides decreases with the increase of deformation temperature during isothermal compression of M50 steel and the fine carbides inhibit the dynamic recrystallization of austenite grain. With the occurrence of dynamic recrystallization, the austenite grains are refined, leading to a minor increase in the flow stress and apparent activation energy for deformation in isothermal compression of M50 steel. The austenite grains begin to coarsen at 1 423 K and dynamic recrystallization is limited. Hot working of M50 steel should not be performed above 1 393 K in order to achieve good workability.

PROBABILISTIC MODELS FOR LONG FATIGUE CRACK GROWTH RATES OF LZ50 AXLE STEEL

Experimental study is performed on the probabilistic models for the long fatigue crack growth rates （da/dN） of LZ50 axle steel. An equation for crack growth rate was derived to consider the trend of stress intensity factor range going down to the threshold and the average stress effect. The probabilistic models were presented on the equation. They consist of the probabilistic da/dN-△K relations, the confidence-based da/dN-△K relations, and the probabilistic- and confidence-based da/dN-△K relations. Efforts were made respectively to characterize the effects of probabilistic assessments due to the scattering regularity of test data, the number of sampling, and both of them. These relations can provide wide selections for practice. Analysis on the test data of LZ50 steel indicates that the present models are available and feasible.

Acoustic Emission Monitoring the Fatigue Crack Growth in SM50B-Zc Steel

The acoustic emission(AE)characteristics from the fatigue crack propagation in SM50B-Zc steel were strongly affected by the environment me- dium.The AE feature from the fatigue process both in air and in 3.5% NaCl aqueous solution mani- fested a periodicity which indicated the fatigue ex- tension was discontinuous.The fatigue striation and secondary cracking were the main AE sources during the fatigue crack growth in air.In contrast, AE during the fatigue crack propagation in 3.5% NaCl solution was released from the intergranular fracture and quasicleavage cracking.

50钢板表面龟裂纹的形成原因与控制

针对50钢200 mm厚连铸坯轧制钢板的严重表面龟裂(发生率7.92%)问题,采用扫描电镜、光谱分析等方法,研究了表面龟裂的形貌、分布、成分等特征。结果表明,表面龟裂随机出现在钢板上,宽度方向上表面龟裂没有固定位置,裂纹深度较浅,两边呈现高亮度组织和氧化原点特征,光谱分析显示裂纹处碳含量比基体高,增碳质量分数0.2%~0.3%。分析认为,连铸过程中铸坯局部增碳,在加热、粗轧过程中热塑性不均匀而导致裂纹及明显的高温氧化特征。根据连铸保护渣增碳机理,优化了结晶器渣线调整模式、铸坯拉速、水口形状、结晶器保护渣成分等连铸工艺参数,有效降低了连铸坯表面局部增碳及钢板龟裂的发生率。

汽车前轴用50钢疲劳试验失效原因分析

对50钢加工汽车前轴后疲劳试验失效试样进行断口、化学成分、金相组织等检测分析,结果表明,缺陷处异常脱碳是导致试样疲劳失效的原因,为客户锻造成型模具内氧化铁皮粘连造成。

Exploring the ultrahigh rolling contact fatigue life of M50 bearing steel by adjusting the cryogenic sequence

The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.

平均应力对50钢超高周疲劳性能的影响

为了进一步拓宽超声疲劳试验的研究范围，对50钢进行了含有平均应力的三点弯曲和非对称拉压疲劳性能试验，得到相应的疲劳，S-N曲线，研究了平均应力对其超高周疲劳性能的影响。结果表明：超声频率加载下平均应力对50钢疲劳性能有显著影响，在应力幅相同的情况下，随着平均应力的增大，疲劳寿命降低；常规疲劳用于描述平均应力影响的Morrow关系仍能描述超声频率加载下高周疲劳（〈10^7周次）范围内拉伸平均应力对50钢疲劳性能的影响，但是不能用来描述超高周范围内拉伸平均应力和弯曲平均应力对疲劳性能的影响；常规疲劳用于描述平均应力影响的Goodman模型仍能很好地描述超声频率加载下一定寿命的应力幅值和平均应力的配合。

热处理工艺对50钢超高周疲劳性能的影响

对50钢进行了正火+高温回火、中温回火、高温回火三种不同热处理状态的对称拉压超声疲劳试验,同时用扫描电子显微分析技术和X射线能谱分析方法对50钢的疲劳断口形貌进行显微分析,研究其疲劳断裂行为和疲劳断裂机理。结果表明,50钢存在表面和内部两种裂纹萌生机制;在本试验范围内,热处理工艺对50钢超高周疲劳性能的影响较低周和高周为小,随着寿命的增加,影响越来越弱;热处理工艺对50钢不同的疲劳阶段有不同的影响起源于不同的裂纹萌生机制,对常规疲劳性能起改善作用的热处理工艺可能对材料超高周疲劳性能的改善没有太大作用。

50车轴钢中异常组织的形成原因

用光学显微镜、透射电子显微镜以及电子探针等现代材料试验手段对50钢中存在的大块黑色团状异常组织进行了研究和分析。结果表明,这种黑色团状异常组织是由片间距不同的团状珠光体组成。产生这种组织的主要原因是50车轴钢锻造后混晶现象严重及存在特别粗大晶粒。

对40、50轴钢的几点看法

在40钢车轴断裂失效的模式、原因和统计分析的基础上,对40钢和50钢的基本力学性能进行了比较,并对40钢和50钢车轴的使用安全性提出了建议。

双道次热压缩50CrV4弹簧钢奥氏体的静态再结晶

通过Gleeble-1500热模拟机对50CrV4弹簧钢(/%:0.53C,0.18Si,0.84Mn,0.012P,0.003S,0.92Cr,0.12V,0.02Ti)50 mm连铸板坯锻制成的15 mm板进行双道次热压缩试验。研究该钢在850~1 000℃以真应变0.1~0.25,应变速率0.1~10 s^(-1),道次间隔1~80 s形变时的静态再结晶行为,并建立了静态再结晶动力学模型。结果表明,随温度、应变量、应变速率、道次间隔时间增加,会加速50CrV4钢静态再结晶进程;在950℃,真应变0.25,应变速率为0.1,1,10 s^(-1)时,该钢发生50%再结晶所需的时间分别为8.42,4.40,2.22 s;该钢静态再结晶激活能为249.974 kJ·mol^(-1)。

一种新型硫系易切削钢与50钢的切削性能对比研究

对比研究了一种新型硫系易切削钢与50钢的力学性能和切削性能。结果表明,两种钢的显微组织均为铁素体和珠光体混合组织,但硫系易切削钢的组织更细,并且含有大量的硫化物易切削相。与50钢相比,硫系易切削钢具有更好的力学性能和更好的切削加工性能。

Nitronic 50不锈钢低温冲击韧性大幅降低原因分析

针对低温风洞运动机构用Nitronic 50奥氏体不锈钢在复检中出现低温冲击吸收能量显著偏低的现象,对该批次不锈钢和参考样品分别取样,进行了化学成分、金相、扫描电镜以及能谱等分析。结果表明:该批次Nitronic 50不锈钢中存在大量短棒状的Al N脆性夹杂物,是导致其低温冲击韧性大幅度降低的主要原因;材料晶粒尺寸偏大且存在混晶现象也降低了其冲击韧性。

50#钢板坯连铸机粘结漏钢原因探讨及解决措施

本文结合酒泉钢铁公司4#板坯生产实际,系统分析了50#钢粘结漏钢的原因,从保护渣、结晶器、冷却水以及工艺操作等方面有针对性地制定了措施,杜绝了粘结漏钢事故,稳定了生产。

退火温度和再结晶比例对0.58Si无取向硅钢0.50mm冷轧板性能的影响

无取向硅钢(/%:0.003C,0.58Si,0.20Mn,0.010P,0.002S,0.25Al,0.003 0N)0.5 mm冷轧薄板由2.6mm热轧板冷轧而成。研究了390~820℃退火再结晶组织比例对该钢磁性能、抗拉强度和硬度的影响。结果表明,未发生再结晶时(390~480℃退火),退火温度对抗拉强度和硬度的影响很小;当再结晶组织比例≥70%时(560~820℃退火),降低退火温度能够有效提高抗拉强度,同时不显著恶化磁性能,但对硬度没有影响;当再结晶组织比例<70%时(>480~<560℃退火),降低退火温度使磁性能剧烈恶化,但能够大幅提高抗拉强度和硬度;当退火温度560℃,再结晶比例70%时无取向硅钢的性能为抗拉强度R_m 470 MPa,HV1硬度值140,铁损P_(1.5/50)7.5W/kg,磁极化强度J_(50)1.70 T,综合性能最佳。

铸钢用50t/32 MVA交流电弧炉炼钢过程电气运行特性

使用电气监测仪表对中信重工机械股份有限公司50t/32 MVA交流电弧炉炼钢过程中的电气参数进行了实测,得到52 310个有效数据。结果表明,有载条件下电抗器上端的功率因数均为0.800以上,供电回路中的电压、电流以及功率因数均处于三相平衡状态。以二次侧工作电流为自变量,建立非线性电抗模型,绘制电气运行特性曲线,确定现用各挡电压下的工作电流许用范围。研究表明,若将电抗器挡位由原来的3挡改设为4挡运行,则炉用变压器容量利用率将提高7.30%,功率因数将由原来的0.812提高为0.841。

卷取温度对50钢热轧钢带组织性能及淬火工艺的影响

文中主要研究了50钢带不同卷取温度条件下的热轧组织性能差异及其对淬火热处理工艺的影响。结果表明:卷取温度由720℃降至620℃,50钢带热轧组织中珠光体体积分数由50%增加至90%,珠光体平均片层间距由367 nm细化至188 nm;抗拉强度提高了166 MPa,但延伸率并未明显降低。随着卷取温度的降低,50钢带热轧组织中铁素体量减少,珠光体片层间距减小,其淬火热处理时奥氏体化速度加快。采用620℃卷取温度生产的50钢热轧钢带与720℃相比,其淬火工艺中的保温时间可缩短30%以上。

整合优势 跨越发展 争雄国内 跻身世界——为庆祝中国钢管诞辰50周年而作

中国钢管 5 0年来取得了举世瞩目的辉煌成就 ,无缝钢管和焊管产量双双居世界第一 ,从调整型数量增长阶段进入了结构推动型创新阶段。在适应中国广阔的市场容量和满足现阶段建设小康社会时期的基本需求的条件下 ,无论是无缝钢管还是焊管都应当不断开发出更高技术含量、更高质量和更高经济效益的新产品系列。

-50℃低温环境结构用S355NL φ406mm×15mm无缝钢管的开发

V-Nb-Ti微合金化S355NL大口径低温结构用无缝管(/%:0.14~0.15C,0.29~0.30Si.1.35~1.37Mn,≤0.014P,≤0.005S,0.02~0.03Nb,0.06~0.07V,0.010~0.020Ti,Ceq 0.39~0.41)的生产流程为100 t EAF-LF-VD-喂Ca线-φ400 mm圆坯连铸-3辊连轧机组-940℃30 min空冷正火处理。16炉批统计结果表明,通过EAF出钢加硅锰、硅铝铁合金,LF采用CaO-SiO2-Al_1O_3渣系,全程吹氩,VD处理20~25 min,连铸长水口和吹氩等工艺措施,钢管的实物质量和性能稳定,组织均匀,晶粒细小,各项性能达到或超过了标准和用户的技术要求;屈服强度R_(eH)380~435 MPa,抗拉强度R_m522~605 MPa,伸长率A 24%~29%,-50℃冲击功132~237 J。