共查询到18条相似文献,搜索用时 93 毫秒
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采用金相和扫描电镜断口分析方法,对77MnA盘条在冷拉拔过程中断裂进行了分析,结果表明,盘条内部存在缺陷是造成断裂的主要原因。 相似文献
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在77MnA线材拉拔终端、拉拔中段和拉拔之前发生脆性断裂的试样中都存在心部马氏体,并且,在拉拔中段的试样中马氏体断成竹节状,在拉拔终端的试样中马氏体与屈氏体基体之间存在孔洞。可以认为脆性的马氏体不能在拉拔过程中与屈氏体协调形变是导致试样开裂的原因。心部马氏体中铬、锰等稳定奥氏体的元素明显偏高,因此,77MnA线材脆性断裂与成分偏析也有一定关系。 相似文献
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作为拉拔用材的77MnA盘条正常显微组织是索氏体和少量珠光体,而在盘条生产过程中出现的马氏体、屈氏体、网状碳化物、较多粗片状珠光体、表面缺陷和拉拔中产生的硬化层组织都会导致盘条在拉拔过程中断裂。 相似文献
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对77MnA预应力钢丝的拉拔易断裂问题进行了分析,主要分析轧制过程中影响质量缺陷的因素,并针对脱碳层的控制、通圈性能不稳定等问题改进措施。 相似文献
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规格Φ5.5 mm的双相不锈钢2205线材经过5道次拉拔至Φ2.5 mm,在拉拔过程中经常出现拉拔断裂。为查找断裂原因,采用宏观分析、光谱成分分析、金相分析、扫描电镜-能谱分析等方法对断裂样品进行了试验检测分析。结果表明,双相不锈钢2205线材基体中大量金属间化合物使材料塑性和韧性下降,在冷拔力的作用下产生断裂。 相似文献
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通过定向凝固+冷拉拔变形工艺制备了不同线径的Cu-20%Ag(质量分数)合金微细丝线材。通过扫描电子显微镜(SEM)观察了不同线径的Cu-20%Ag合金线材的微观组织演变,发现在拉拔变形过程中, Cu-20%Ag合金线材内部晶粒不断细化,共晶区域较之铜基体区域更为明显,当真应变为 8.13 时线材内部的共晶纤维细化至平均宽度 500 nm 左右。研究了 Cu-20%Ag 合金冷拉拔变形过程中组织性能的演变规律,探明了其组织演变对导电率变化的影响机理。Cu-20%Ag合金在拉拔变形过程中晶粒的细化和破碎导致的晶界面积增加是导电率降低的主要原因。 相似文献
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B7钢Φ22 mm热轧盘条在冷拔中断裂,采用断口观察、化学成分、显微组织检验以及能谱分析测试了断裂盘条.测试结果表明:Mn、Cr偏析导致盘条中心存在马氏体组织是造成拉拔断裂的原因.通过轧制吐丝温度由905~ 915℃降至840~ 850℃以及保温时间由285 s延长至420 s,可有效减少心部马氏体的产生,消除了冷拔断... 相似文献
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A comparative study was conducted on the effects of lamellar cementites and globular cementites on the cold drawing process and the mechanical properties of pearlitic wire steel, with the help of metallographic microscope, scanning electron microscope, transmission electron microscope, tensile tester and hardness tester. The lamellar cementites showed the deformation capacity to some extent during the cold drawing process. As the drawing strain increased, the pearlitic wire with globular cementites evolved into the fibrous form gradually and no obvious defects were found in the microstructure. The globular cementites turned to the drawing direction without any deformation of itself during the deformation process. And micro- cracks occurred in the cementite/ferrite interface due to stress concentration caused by pinning dislocations in spherical cementites. The strength and hardness of both pearlitic wires gradually increased as the drawing strain rose. And the pearlitic wire with lamellar cementites had a higher drawing hardening rate. The ferrite <110> texture formed in both pearlitic wires during the cold drawing process. Compared with the globular pearlite, the pearlitic wire with lamellar cementites had higher ferrite <110> texture intensity. And the difference of their ferrite <110> texture intensity became bigger and bigger as the drawing strain increased. 相似文献
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According to DIN-ISO 898-1 high tensile bolts of class 8.8 must have a quenched and tempered structure. Therefore either quenched and tempered wire rod is used for cold heading or the bolts are quenched and tempered after the bolt forming process. This paper presents a new wire rod, which offers the chance to get comparable or even better final properties and lower production costs: a low-carbon MnSi wire rod is used as basic material. The final tensile strength is produced by drawing and cold forming. The conventional final quenching and tempering is omitted and for many cases also baking can be avoided. An increased fatigue resistance and the elimination of final straightening of the bolts are additional advantages of the new process. 相似文献
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