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.

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.

Analysis of High-Cr Cast Iron/Low Carbon Steel Wear-resistant Laminated Composite Plate Prepared by Hot-rolled Symmetrical Billet

This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of different rolling reductions(30%,45%,and 60%)on the microstructure(interface and HCCI layer)and mechanical properties(bonding strength,hardness,and wear resistance)of the composite plate were studied.SEM images showed that when the reduction was increased,no impurities and interlayers were found between the microscopic interfaces after hot rolling,and the bonding interface exhibited a wave-like shape.EDS analysis showed that the Cr element diffusion between two metals after hot rolling was promoted when the reduction was increased,thereby improving the bonding quality under the same rolling temperature and rolling speed.Experiments showed that due to the stress release effect of the LCS of the cladded layer,the macro-slab shape after hot rolling performed well,and the brittle HCCI layer underwent thermoplastic deformation without cracking.Moreover,the increase of rolling reduction improved the bonding quality.As the rolling reduction was increased,the volume fraction of Cr-carbides in the HCCI layer also increased,resulting in an increase of hardness and wear-resistance.

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.

Effect of Rolling Process on Microstructure and Wear Properties of High Carbon Equivalent Gray Cast Iron

Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.

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。

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.

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。

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。

堆焊-热轧制备高铬铸铁/低碳钢耐磨复合板性能研究

利用高铬铸铁焊条对碳钢板表面进行堆焊,经过对称组坯后分别采用15%,25%,30%的压下率在四辊轧机上进行多道次包覆热轧。采用扫描电镜和能谱点扫描、线扫描等方法对复合材料的结合界面和高铬铸铁层情况进行微观组织观察,并研究热轧对复合板力学性能的影响。实验结果表明,复合板经过热轧后板形良好,高铬铸铁与低碳钢实现热塑性变形;原堆焊结合界面处的裂纹和空隙缺陷被消除且出现了无碳化物区域和组织共生现象,剪切强度提高;热轧使得使堆焊高铬铸铁层的共晶碳化物链网状被打碎,碳化物弥散分布。

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.

YZ-1型组合式合金铸铁轧辊的结构与性能

分析了轧辊承载能力和YZ－1型组合式合金铸铁轧辊的设计原理、结构特点及性能．

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.

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.

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。

石墨及碳化物对高镍铬无限冷硬铸铁轧辊耐磨性的影响

本文研究了具有不同石墨和碳化物含量的高镍铬无限冷硬铸铁轧辊材料在滚动摩擦和干滑动摩擦条件下的摩擦学特性,考察了高镍铬无限冷硬铸铁中石墨和碳化物数量、分布对其摩擦学特性的影响。研究结果表明,组织中的石墨和碳化物数量、形态和分布对材料的耐磨性有较大影响。石墨含量在低于9.21%时,增加石墨量并适当减少碳化物量可以提高材料的耐磨性;呈均匀分布的长片状石墨和连续网状分布的碳化物对提高高镍铬无限冷硬铸铁轧辊的耐磨性有显著意义。

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。

电磁半连续复合铸造轧辊的思路与实践

为了实现复合轧辊的顺序凝固,研制了电磁半连续复合铸造试验装置,利用该装置进行了一系列电磁半连续复合铸造试验,探索出了一套合理的电磁复合铸造工艺,制造了高铬铸铁/45#钢复合轧辊,并进行了装机试验。结果表明:电磁半连续复合铸造轧辊思路正确,装置简单合理,既实现了轧辊在复合过程中的顺序凝固,减少了铸造缺陷,又使复合界面达到良好结合,提高了轧辊质量和生产效率。