Laser Surface Remelting of Medium Ni-Cr Infinite Chilling Cast Iron Roll

Laser surface remelting of medium Ni-Cr infinite chilling cast iron was performed with a continuous wave COa laser beam with the power of 7 KW under the argon shielding. The microstructural analysis of the laser remelted layer by optical microscope shows that the laser remelted layer consists of three zones, which is the melting zone, the transition zone and the heat affected zone. The size of the dendrite of the melting zone is only in the 1/10 to 1/30 range of that of the substrate. The distribution of the hardness of the laser remelted layer was detected, and the carrying capacity of rolling steel was also field-tested. The results show that both the hardness of the remelted layer and the carrying capacity all increase, especially, the carrying capacity was 50% increased compared with the substrate.

Properties of Cross-Rolled Low Alloy White Cast Iron Grinding Ball

The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.

Centrifugal Casting of High Speed Steel/Nodular Cast Iron Compound Roll Collar

The centrifugal casting of compound HSS/nodular cast iron roll collar was studied,and the factors affecting transition zone quality were analyzed.The pouring temperature and interval in pouring are the main factors affecting transition zone quality.By controlling process parameter and flux adding during casting,high quality roll collar was obtained.The cause,why in the casting of HSS part,segregation appears easily,was analyzed and the countermeasure eliminating segregation was put forward,the measure eliminating heat treatment crackling was also put forward.

高镍铬无限冷硬球墨铸铁轧辊工作层离心铸造过程数值模拟

借助有限元模拟软件ProCAST对高镍铬无限冷硬球墨铸铁轧辊工作层离心铸造过程进行了分段建模,计算了铸件的温度场、流场。结果表明,铁液与离心铸型内壁接触后,受到自身重力、旋转铸型带来的离心力、摩擦力三个合力作用,以层状形式沿铸型内壁做圆周运动,沿着内壁同时向铸型两端运动,先到达离浇道距离较近的模具一端,沿轴向向另一端铺展。在有限元模拟辅助下生产出的高镍铬无限冷硬球墨铸铁离心复合轧辊,工作层为树枝状结晶组织,技术指标符合要求。

基于ProCAST数值模拟技术降低离心复合铸铁轧辊底波衰减发生率

离心复合轧辊生产过程中,由于其收缩特性轧辊芯部容易出现缩松等缺陷,造成其辊身出现底波衰减现象;为解决这一问题,唐山钢铁集团重机装备公司(以下简称唐钢重机)联合燕山大学利用ProCAST数值模拟技术,分析出降低底波衰减发生率的因素,用数值模拟结果优化生产工艺,降低底波衰减率或者驱逐缺陷位置至非关键位置。

高铬铸铁轧辊材质的氧化行为研究

将高铬铸铁轧辊材质试样分别在450℃、500℃、550℃下进行氧化,采用激光共聚焦显微镜、金相显微镜、扫描电镜观察氧化膜形貌、微区成分,硬度计检测硬度。结果表明:随氧化温度的升高、高铬铸铁轧辊中各相的氧化程度以及整体氧化膜的致密度均有明显差异,试样的硬度也有明显不同。

Chemical Compositions,Microstructure and Mechanical Properties of Roll Core used Ductile Iron in Centrifugal Casting Composite Rolls

The industrial manufacture processes of three kinds of roll core used ductile irons have been investigated via systematical experiments. EfFects of the ratio of C/Si, pig iron, nodularizer and alloying method on the microstructure and mechanical properties of the heavy section ductile iron have been analyzed. It has been found that when treated with RE-Mg plus Sb, high quality nodular castings can be produced even if much anti spheroidizing alloy elements are included in the pig iron. The alloy element Sb played an important role in the control of graphite morphology.

High Temperature Oxidation of a Work Roll Grade High-Chromium White Cast Iron

High-chromium white cast iron is a common material for the manufacture of the work rolls used in the fin- ishing stands in hot strip mills. The high temperature oxidation behaviour of as-cast and heat-treated high-chromium white cast iron was studied by gravimetric means at 650 ℃ in atmospheres that included dry air and a mixture of dry air and water vapour. For both environmental and material conditions, the oxidation rate of the alloys was represen ted by parabolic trends and the oxidation phenomenon was more obvious when the samples were oxidised in water vapour. Water vapour also influenced the chemical composition of the oxides formed in the alloy and under this condi tion, the oxide scale formed on the alloy contained the oxides FeCr2O4 , （Fe,Cr）3O4 and （Fe,Cr）2 O3. In contrast, the alloys exposed to dry air conditions only experienced the formation of FeCr2O4 and （Fe,Cr）2O3. It was found that the presence of water vapour and the chromium content of the alloys increased the oxidation rate by a mechanism that involved chromium depletion of the oxide as a result of hydroxide formation. The differences observed in the oxi- dation behaviour of the alloy are discussed in terms of the composition of the oxidant atmosphere and the metallurgi cal condition of the specimens.

轧辊用高钒高速钢的滚-滑动磨损性能及失效行为研究

在高应力滚-滑动(滑动率约10%)条件下,利用自制的磨损试验机研究了高钒高速钢的磨损性能,并利用电子显微镜分析了失效行为.结果表明:高钒高速钢的相对耐磨性是高铬铸铁(Cr20)的2倍以上.磨损失效形式为显微切削与疲劳剥落的复合,兼有碳化物碎裂.碳化物对磨损失效有重要作用,高铬铸铁中的杆状M7C3型碳化物易于弯曲、碎裂而在其内部形成大量裂纹,促进磨损表面产生大块的疲劳剥落;高钒高速钢中团块状VC硬度高、形态好、具有精细亚结构、不易碎裂,可有效地抵御显微切削和疲劳剥落,是高钒高速钢耐磨性优良的原因.

高钒高速钢与高铬铸铁的滚动磨损性能对比研究

以高铬铸铁为参照,在自制的模拟轧辊磨损试验机上研究了高钒高速钢的滚动磨损性能.结果表明:随磨损循环次数的增加,两种材料的磨损量均直线地增加,高钒高速钢的相对耐磨性是高铬铸铁的4倍以上;高铬铸铁中的裂纹主要由于M7C3的严重碎裂而萌生于M7C3的内部,高钒高速钢中的裂纹则主要萌生于VC与基体的界面,并沿VC的表面扩展.高钒高速钢中VC形状好、不易碎裂及基体硬度高是其耐磨性优良的主要原因.

铸铁电火花沉积WC-8Co超细涂层的组织及性能

采用电火花沉积技术,在铸铁表面制备WC-8Co沉积涂层。利用XRD、SEM、显微硬度计、摩擦磨损试验机研究了涂层的微观组织及耐磨性能。结果表明,通过优化的沉积工艺参数可以获得组织均匀、致密且与基体呈冶金结合的沉积层。沉积层主要由Co3W3C、Fe3W3C、W2C和Fe7W6相组成;沉积层中弥散分布有大量的超细碳化物颗粒。沉积层的最高硬度为1512.1Hv,其耐磨性能是基体的2.3倍;沉积层的磨损机制主要是磨粒磨损和疲劳磨损。涂层中弥散分布的超细硬质相是沉积层硬度及耐磨性能提高的主要因素。

热轧高铬铸铁轧辊氧化膜的研究

本文利用扫描电镜、能谱仪对热轧高铬铸铁轧辊氧化膜在不同温度和保温时间下的表面和截面形貌进行了观察和研究,通过X射线衍射仪对轧辊氧化膜的组成和结构进行了分析。结果表明,高铬铸铁轧辊氧化膜主要由Fe3O4和FeCr2O4组成,而温度是影响氧化膜质量最重要的因素。同时,对氧化膜表面瘤状物形成的原因和氧化膜的失效机制进行了分析,为现场辊温控制,有效控制高铬铸铁轧辊氧化膜完好,提高带钢的表面质量提供了参考。

高硬度高铬复合铸铁轧辊的研制

采用先进的三次浇注二次复合的轧辊生产工艺,解决了高铬复合铸铁轧辊结合层及芯部强度低的技术难题;采用先进的成分设计,对外层材质及中间层材质进行有效的变质处理,材料的强度、韧性及耐磨性得到提高;对轧辊进行高温淬火和二次回火热处理,成功地获得了高的辊身硬度及低的残余奥氏体含量。

高铬铸铁轧辊表面氧化膜影响因素的研究

分析研究了高铬铸铁轧辊在不同氧化温度、氧化时间、表面粗糙度和介质条件下的氧化膜形貌，得出高铬铸铁轧辊高的表面光洁度有利于获得均匀致密的氧化膜；随氧化温度的升高和时间的增加，氧化膜不断长大、增厚；高温水蒸气会加速轧辊氧化。并提出应适当调整轧辊冷却条件，使下线轧辊温度控制在60～65℃左右。

高铬镍无限冷硬铸铁轧辊材料的磨损性试验

利用自行开发研制的高温滑动磨损与热接触疲劳材料试验机,并运用表面覆膜技术、金相分析和扫描电镜,研究了用于精轧机的高铬镍无限冷硬铸铁轧辊材料在热轧状态下的耐磨特性,分析了这种轧辊材料的表面形貌、表层组织的变化情况。结果表明,当轧制公里数达到88 km时,高铬镍无限冷硬铸铁轧辊表面产生了碳化物的浮凸和剥落。

白口铸铁磨面辊齿等离子弧重熔组织和耐磨性

利用等离子弧重熔技术对离心铸造白口铸铁磨面辊齿面进行强化处理,借助光学显微镜和洛氏硬度计观察测试重熔层的组织结构及硬度,并对重熔前后试样表面的耐磨性进行了对比试验。试验结果表明:辊齿经等离子弧重熔组织由亚共晶白口转变为共晶和过共晶的混合组织,拉齿破坏的离心铸造的"流线的连续性"得到恢复,辊齿齿顶的硬度由原来HRC58～60提高到了HRC64～65,耐磨性是重熔前的2～3倍。

球墨铸铁曲轴表面强化处理技术

柴油机曲轴承受复杂交变的弯曲-扭转载荷和一定的冲击载荷,疲劳断裂是曲轴的主要破坏形式,裂纹源易发生在连杆轴颈与曲臂过渡圆角处,工艺上提高曲轴疲劳强度的方法主要是圆角强化,在其表层形成一定的压应力来实现的。介绍了滚压、淬火、氮化、喷丸、激光冲击强化等工艺方法,分析曲轴强化机理和工艺方法,为提高曲轴使用寿命提供了参考。

φ265中镍铬冷硬铸铁轧辊残余应力的测试分析

对265中镍铬冷硬铸铁轧辊铸态、热时效态和自然时效态的残余应力进行了测试，并分析了测试结果和分布规律。

高钒高速钢、高铬铸铁冷轧辊磨损试验研究

通过对高钒高速钢、高铬铸铁轧辊试样的冷轧模拟试验研究表明,高钒高速钢由于其均匀分布、形态较好的高硬度碳化物使其耐磨性大幅提高,在同等试验条件下为高铬铸铁试样的4.4倍。微观分析表明,轧辊试样磨损机理主要表现为疲劳剥落,浅层剥落主要表现为棘齿裂纹的萌生、扩展与断裂的过程;高铬铸铁轧辊试样深层失效主要表现为M7C3型碳化物的断裂并形成裂纹源并在疲劳循环过程中断裂失效,高钒高速钢轧辊试样MC型碳化物有少量破碎并形成晶间裂纹源,主要失效方式表现为碳化物颗粒剥落,并对此进行了定性的力学解释。

热处理对高铬铸铁轧辊组织和性能的影响

研究了淬火温度、淬火冷却方式和回火温度对高铬铸铁轧辊组织和性能的影响。结果表明，油冷条件下，淬火温度低于1000℃，随着淬火温度升高，硬度升高，随后硬度反而下降，雾冷和空冷条件下，淬火温度对硬度的影响规律与油冷时相似，获得最高硬度的淬火温度超过油冷时的淬火温度，达到1025℃。回火温度低于500℃时，高铬铸铁轧辊硬度变化不明显，超过575℃，硬度明显下降，高铬铸铁轧辊在450℃回火4小时，具有良好的综合力学性能和优异的耐磨性。