共查询到20条相似文献,搜索用时 10 毫秒
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S. -H. Song Z. -X. Yuan J. Jia D. -D. Shen A. -M. Guo 《Metallurgical and Materials Transactions A》2003,34(8):1611-1616
The effect of tin on the hot ductility of a 0.15 wt pct C steel is investigated using a continuous-casting thermal simulator
with three cooling rates: 5 °C/s, 10 °C/s, and 20 °C/s. Non equilibrium grain-boundary segregation of tin occurs during cooling
and plays an important role in reducing the steel hot ductility. There is a critical cooling rate for the Sn segregation being
between 5 °C/s and 20 °C/s. When the cooling rate is higher than the critical cooling rate, the segregation caused by diffusion
of tin-vacancy complexes to the boundary is dominant, leading the boundary concentration of tin to increase with decreasing
cooling rate. However, when the cooling rate is lower than the critical cooling rate, the desegregation caused by backward
diffusion of tin away from the boundary also takes place during cooling, leading the boundary concentration of tin to decrease
with decreasing cooling rate. 相似文献
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利用透射电镜研究了低碳微量铌钢过冷奥氏体形变过程中的碳氮化物析出,运用Gladman晶粒粗化机制讨论了析出相颗粒的平均直径、体积分数和铁素体晶粒尺寸的关系.实验结果表明:实验用钢中的微量Nb在1200℃时完全固溶,并在760℃变形前的冷却过程中无Nb(CN)析出.在形变过程中Nb(CN)的析出同样需要孕育期,但与等温过程相比大大提前.当变形量积累到一定值(本实验条件下ε=0.69)时,大量动态析出的Nb(CN)颗粒弥散分布在晶界以及位错线上.Nb(CN)析出随着应变量的增加而增加,但颗粒长大不明显,计算得到的铁素体晶粒平均截径与实际测得的铁素体晶粒吻合得较好. 相似文献
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The loading capacity of ultralarge container ships has reached 24 000 TEUs so far, and to ensure the safe operation of these ships, the maxmium thickness of crack arrest steel used in the upper deck areas reaches 100 mm, and crack arrest toughness(Kca) needs to be >8 000 N/mm3/2.The EH47 steel was employed to study the effect of Nb on the phase transformation of supercooled austenite in the continuous cooling process after rolling and the effect of Nb on microstructure a... 相似文献
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为了得出铌微合金化H13钢中合适的铌元素添加量,以H13钢中的一次碳化物为研究对象,通过实验室冶炼不同铌元素质量分数的H13钢,系统地研究了Nb-H13钢中一次碳化物的析出机理和合适的Nb添加量。结果表明,当H13钢中铌的质量分数小于0.03%时,Nb-H13钢中的一次碳化物主要为富钒相;当H13钢中铌的质量分数达到0.05%时,Nb-H13钢中的一次碳化物主要为富钒相和富铌相。铌微合金化H13钢中铌元素的添加量应小于0.03%。铌质量分数的高低会显著影响FCC相中碳化物的析出顺序,随着铌质量分数的增加,碳化物的析出顺序由首先析出富钒相转变为首先析出富铌相,且富铌相的热稳定性要远高于富钒相。理论计算结果与试验观察结果基本一致,工业试验结果同样论证了本研究的结论。 相似文献
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Two grades of the Nb-microalloyed steel, one modified with B, were subjected toin situ melting and the thermal schedules experienced by the billet surface in the continuous casting process. The hot ductility
was evaluated at various temperatures at the straightening stage of the process. It was found that addition of B improves
the hot ductility in the austenite region. Such improvement could be due to fast precipitation at grain boundaries as well
as depletion of precipitants and strengthening elements in the matrix. 相似文献
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通过Gleeble热模拟实验研究了含0.038%Nb(质量分数)的热轧TRIP钢在高温奥氏体区的热加工工艺,借助光学显微镜、扫描电镜和透射电镜分析了组织演变和Nb的析出行为,并利用电感耦合等离子体发射光谱仪定量分析了Nb的固溶/析出程度.在1250℃奥氏体化5 min后添加Nb有70%固溶于奥氏体.在1000℃以上的奥氏体再结晶区变形过程中Nb的析出量仅占总固溶量的3%,不能有效抑制静态再结晶,奥氏体晶粒得到明显细化.在900℃的奥氏体未再结晶区变形前析出Nb量已达到总固溶量的9%,再结晶被抑制而获得拉长状奥氏体.奥氏体未再结晶区变形可促进铁素体转变并细化铁素体晶粒.再结晶奥氏体或形变奥氏体状态下冷却至650℃时分别有占总添加量的48%和40%的Nb仍以固溶态存在. 相似文献
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针对含铝冷镦钢在浇铸过程中的塞棒异常侵蚀问题,通过塞棒基体成分分析、塞棒侵蚀层的元素分布观察以及热力学计算,探究了含铝冷镦钢生产过程中塞棒侵蚀的成因,并提出相应的改善措施。结果表明,钢中高质量分数的钙与耐火材料中的Al2O3、SiO2、C发生反应,生成低熔点钙铝酸盐或硅铝酸盐以及Al2O3-C质塞棒本身材质中C+SiC的质量分数过高是造成含铝冷镦钢浇铸过程中塞棒严重侵蚀的主要原因,通过规范钙处理工艺、更换镁碳质塞棒等措施,能够显著改善塞棒的异常侵蚀问题,塞棒的使用寿命由286~824 min提升至460~1 020 min,平均使用寿命由原来的495 min上升至802 min。 相似文献
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A. I. Fernández B. López J. M. Rodriguez-Ibabe 《Metallurgical and Materials Transactions A》2002,33(10):3089-3098
Static recrystallization mechanisms have been studied in a coarse-grained Nb microalloyed austenite. An austenite with a coarse
grain size of 800 μm, typical of thin slab casting processes, has been deformed in torsion at a temperature of 1100 °C. After deformation, the
specimens have been held for different times at this high temperature and then water quenched. The microstructural changes
occurring during static recrystallization were characterized by metallographic evaluation. It has been observed that new recrystallized
grains nucleate preferentially on parent austenite grain boundaries and tend to form in clusters. Once all the boundaries
have been consumed, intragranular nucleation is actived at late stages of recrystallization. Clustered nucleation allows impingement
to take place early during the recrystallization process, favoring grain-coarsening phenomena to occur behind the recrystallization
front, which is denoted by the significant reduction in the number of grains per unit volume observed during early stages
of recrystallization. Static recrystallization proceeds heterogeneously, as a result of a nonuniform distribution of stored
energy in the deformed material. A continuous decrease of the average migration rate of the recrystallization front is observed,
which can be ascribed to the reduction of the driving force for migration as recrystallization advances. 相似文献
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本文利用优化设计的结论,给出了中厚板车间使用的双臂曲柄摇杆式翻板机机构设计的详细方法。这种方法对于此类翻板机的设计及改进具有一定的参考价值。 相似文献
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吴锦圆 《冶金标准化与质量》2012,50(3):22-24
介绍50mm的钢球用圆钢B2的开发过程,并对开发过程中出现的质量问题进行分析改进。永钢开发B2钢球用钢过程中出现了低倍中心裂纹的质量问题。采取延长加热时间、提高收集温度等措施后质量均能满足客户要求。 相似文献
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对唐钢生产的20CrMoA抽油杆用钢存在的锻造开裂进行了分析,并提出了改进措施,经实施达到预期的实用效果。 相似文献
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从转子结构、螺栓试验分析、受力计算等方面对大型凸极同步电动机转子极靴固定螺栓断裂失效原因进行分析.螺栓头部贯通十槽及开槽深度超过允许值将降低螺栓强度.极靴螺栓静态预紧力过大,可能会导致在电动机磁极高速运转的离心力作用下螺栓产生塑性变形.选择合适的螺栓头部结构型式及螺栓静态预紧力可以保证螺栓连接的可靠性. 相似文献
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针对780 MPa级双相钢表面存在严重的条状色差缺陷,从微观特征方面进行系统研究。采用SEM及EPMA分析手段研究缺陷表面情况,结果表明,缺陷处微观形貌呈粗糙破碎状,破碎的密集程度和缺陷的严重程度正相关;能谱和电子探针证明,破碎处只存在轻微氧化。应用辉光手段分析表层富集情况,色差严重程度与硅、锰等元素富集峰值距表层深度密切相关,结合热轧截面分析富集现象在热轧以橄榄石相的形式存在,宏观表现为条状红铁皮,该铁皮经过酸洗后难以除尽,在后续冷轧时不同区域表层元素富集深度及破碎密集程度存在差异,表现为连退板表面的条状色差缺陷。在此研究基础上优化热轧和冷轧生产控制方案,最终有效降低或消除了连退板表面条状色差缺陷。 相似文献