浅析高铬白口铸铁磨球的铸态组织设计

在传统工艺的实际生产条件下，高铬白口铸铁磨球易形成较大的内应力，这是导致此类磨球生产和服役条件失效的主要原因。分析热加工全过程可知磨球铸态组织设计的重要性在于期望目标下的铸态组织完全可能仅需采用亚温处理工艺就可达到组织和性能要求，从而不仅从根本上解决了内应力这一中心问题，而且可降低能耗、成本，改善作业环境和缩短生产周期。     

保证高铬铸铁磨球质量的措施

介绍高铬铸铁磨球生产中采取严格选择原材料,执行正确工艺,设计合理的浇注系统,控制浇注温度、浇注速度,及时检修工装等措施,能够获得健全的高铬铸铁磨球,保证磨球的质量和寿命。     

适合现代规模化生产的高铬铸铁磨球新工艺

考虑磨料介质的实际服役工况条件，生产高铬白口铸铁磨球的工艺设计原则应为：在获得高硬度的前提下，进一步提高韧性。介绍在实践中成功运用在控制冷速、成分设计、铸造冶金处理和热处理等方面的新工艺，并指出该工艺适合现代工业的规模化生产方式，具有较强的市场竞争力。     

低铬铸铁磨球的生产实践

我公司热电厂使用的磨球是球磨机主要易损件之一，以往先后使用过抗磨锻钢磨球和球墨铸铁磨球。抗磨锻钢磨球具有韧性好，不易破碎的特点，但是硬度偏低，不耐磨，球耗较高，易失圆；球墨铸铁磨球球化率波动较大，要求严格的热处理工艺，同时球的破碎率较高。目前市场上常见的还有高铬铸铁磨球和低铬铸铁磨球，相对高铬铸铁磨球而言，     

一种新型高铬铸铁磨球的研制与应用

从成分设计、熔炼、铸造、热处理工艺等几方面入手研制新型高铬铸铁磨球，通过性能测试、组织分析及实际应用等方面证明其性能卓越。     

提高钨合金铸铁磨球使用性能的研究

以我们新开发的钨合金铸铁磨球为基础，探讨了采用稀土变质处理以提高其使用性能的可靠性。研究结果表明，钨合金铸铁经适量稀土变质处理后，共晶碳化物内网状分布变成断网状分布，磨球冲击韧性显著提高，硬度略有上升，耐磨性明显改善，冲击疲劳寿命显著提高，磨球各项指标达到了甚至超过了高铬铸铁球的水平。     

MPS（MBF）型中速磨煤机用高铬白口铸铁磨辊的研制

在分析ＭＰＳ（ＭＢＦ）型中速磨煤机用磨辊的工况条件和性能要求的基础上，结合国内资源，设计确定了材料的成分组成，制定了合理的铸造、热处理工艺，成功地研制了适合我国煤质特点的高铬白口铸铁磨辊．试验运行结果表明，同样工况条件下，所研制的高铬白口铸铁磨辊的耐磨寿命比进口镍硬Ｎ＃铸铁提高５０％以上，且成本降低，经济效益十分可观．     

有关高铬铸铁磨球的一些问题

根据实验及现场调查结果阐述了铬白口铸铁的组织组成、化学成分及生产工艺对磨球使用寿命的影响。并推荐具有（α＋Ｃｒ７Ｃ３）聚合组织的高铬铸铁用于水泥球磨机磨球。     

强韧型高铬铸铁的强韧性机理,性能及其应用价值

球磨机磨球用材质种类较多,有锻钢、球墨铸铁和高铬铸铁等。高铬铸铁有人称之为第三代抗磨材料,该材料视其金相组织中抗磨相的碳化物形状、数量、间距和分布的不同,又分为马氏体高铬铸铁、奥氏体高铬铸铁和强韧型高铬铸铁。与其他型材料相比,强韧型高铬铸铁具有较强的抗塑变能力,适宜的硬度,高的断裂强度等特点,适用于大、中、小型球磨机,且使用安全可靠,具有较好的应用价值。     

金属型高铬铸铁磨球生产工艺

在水泥、硅酸盐制品、新型建筑材料、耐火材料、化肥、黑色与有色金属选矿及玻璃陶瓷等生产行业，球磨机是粉碎和研磨矿石、煤、水泥等相关物料的主要生产设备，磨球是其主要易损件之一。与其他材质类磨球相比，高铬铸铁磨球以其高硬度、低磨耗、韧性好、破碎少及良好的综合力学性能等而得到广泛应用。     

Wear Characteristics of Large Grinding Balls in an SAG Mill

The wear characteristics of larger than 120 mm-diameter grinding balls used in large semiautogenous (SAG) mills is studied in the present paper. SEM observation on the worn ball surface reveals a severe microcutting process. Abrasion grooves can be found on the overall surface. Moreover, persistent microcracks are found on the surface. The observation on the cross section indicates extended white layers and white bands exist in the subsurface of worn balls. The white layer is not homogenous on the surface. The largest white layer is about 20 μm thick and 1.3 mm long. The wear resistance of the white layer is tested with a simulated high stress impact wear tester. It is found that the white layer is associated with delamination wear, which significantly increases the wear rate. The delamination wear mechanism is explained from the intensely deformed microstructure and microcracks inside the white layer. Based on the experimental results, a wear formula consisting of both microcutting wear and delamination wear is submitted. This formula means that high wear resistance is only achieved when the hardness and fracture toughness of grinding balls are increased simultaneously.     

烧结助剂含量对氮化硅陶瓷球致密化和力学性能的影响

以α-Si3 N4粉为原料,纳米级Y2 O3和Al2 O3为烧结助剂,采用气压烧结工艺制备氮化硅陶瓷球,研究了烧结助剂含量对氮化硅陶瓷球致密化及力学性能的影响.结果表明:随着烧结助剂含量的增加,氮化硅陶瓷球的相对密度逐渐增大,维氏硬度逐渐降低,断裂韧性不断提高;烧结温度为1750℃时,烧结助剂含量为8％的氮化硅陶瓷球综...     

复合金属型模具群铸磨球工艺早期失圆机理的数值分析

在对铸造磨球凝固过程进行理论分析的基础上,利用华铸CAE软件对复合金属型模具群铸磨球工艺进行充型凝固特性三维数值模拟研究,确定了造成磨球出现早期失圆和缩松缩孔缺陷的主要原因,为进一步改进复合金属型模具群铸磨球工艺奠定了理论基础.     

预应力淬硬磨削工件表面层质量试验研究

从抗疲劳制造与绿色制造的观念出发,融合预应力磨削与磨削淬硬技术原理,提出了将残余应力控制、表面淬火及磨削三者集成于一体的预应力淬硬磨削技术理论与方法。对45钢试件进行了预应力淬硬磨削加工试验,以工件淬硬层表面残余应力、硬度及粗糙度为研究对象,与相同条件下的磨削淬硬工艺试验结果进行了对比分析。结果表明：预应力淬硬磨削工艺可增大工件表面残余压应力,减小拉应力,其工件表面残余应力状态优于磨削淬硬工艺;预应力淬硬磨削工件表面硬度可以达到基体硬度的3倍左右,而工件表面粗糙度小于磨削淬硬工艺工件表面粗糙度。因此,在相同的加工条件下,预应力淬硬磨削工艺比磨削淬硬工艺具有更好的抗疲劳性、耐腐蚀性及表面完整性。     

Effect of impact on the grinding media and mill liner in a large semiautogenous mill

The introduction of large semiautogenous mills to grind larger pieces of ore necessitates the use of large diameter grinding balls. Grinding balls as large as 127 mm (5 in) in diameter are not rare. The increased height of fall of such grinding balls in these larger mills results in severe impact between the grinding balls and also between the grinding balls and the mill liners. The effect of this impact on the mill liner and the 127 mm diameter grinding balls used in a 8.2 m diameter semiautogenous mill were studied. It was observed that the repeated severe impacts resulted in the formation of adiabatic shear bands below the surface of both the mill liner and the grinding balls. Severe impact also resulted in fatigue failure of the mill liners and a phase transformation below the surface of the grinding balls due to the generation of high temperature. In smaller mills, using smaller grinding balls, considerable work hardening was observed beneath the surface of the grinding balls. The extent of the work hardening increased with increase in the ball and mill diameter.     

Magnetic fluid grinding of advanced ceramic balls

A new method of finishing advanced ceramics, namely, magnetic fluid grinding with a float, has been developed especially for Si₃N₄ balls. The removal mechanism in this process and the optimum grinding conditions have been studied in the last seven years. In this paper, the results from the published papers are surveyed and summarized from the viewpoints of removal rate, surface roughness and sphericity of balls. From this review, it was found that magnetic fluid grinding can be applied to the rough finishing process at high speed. However, if a sphericity smaller than 0.1 μm is required, some new ideas are necessary.     

A quantitative comparison between residual stresses and fatigue properties of surface-ground bearing steel (En 31)

Experimental measurements of the residual stresses in hardened and tempered En 31 steel have been made after grinding under various conditions. Wheel speed, downfeed, wheel hardness, dressing speed and lubricant type have been studied separately. Three combinations of parameters were then selected to represent abusive, conventional and gentle grinding conditions. It is clear that high tensile residual stresses can be generated even under “conventional” conditions mainly owing to the martensitic transformation and its associated volume change. A strong dependence of the endurance limit on the maximum residual stress level is found in reverse-bend fatigue tests.     

轴承钢球微观磨粒磨削过程的数值模拟

从微观视角出发,适当简化轴承钢球磨削过程,建立了微观磨粒磨削轴承钢球的几何模型,借助有限元软件Deform-2D对该磨削过程进行了数值模拟,研究了钢球表面微屑的形成和折断机理。通过模拟仿真试验,还得出了不同磨粒前角下钢球内部的应力应变场、温度场的分布云图以及主磨削力的变化趋势,为深入研究钢球磨削机理提供了一种新思路。     

Investigation of mechanical and tribological properties of amorphous diamond-like carbon coatings

We investigated the mechanical and tribological properties of amorphous diamond-like carbon (DLC) coatings deposited on Si(100) by a pulsed bias deposition technique. Tribological studies were performed using a pin-on-disc (POD) apparatus under a normal load of 6.25 N and at 10% relative humidity, with a ruby pin as a slider. Hardness measurements were performed using a nanoindenter and apparent fracture toughness using indentation techniques. We studied the influence of residual stresses on apparent fracture toughness. The data revealed that the thickness, hardness and compressive stress of the coating play different roles in the apparent fracture toughness. Crack initiation is influenced by the thickness and hardness of the coating, whereas crack propagation is influenced by the compressive stress in the film. The apparent fracture toughness of DLC coatings increased with coating hardness.     

[刀具及切削工艺]高速铣削中TaC（NbC）对硬质合金刀具磨损性能的影响

针对航空航天钛合金加工时硬质合金刀具磨损过快的难题,制备了主元素一致、微量合金碳化物TaC（NbC）含量不同的两种WC-Co基硬质合金材料。采用高温维氏硬度计检测两种材料的高温硬度和高温断裂韧性,并制备相同几何参数的立铣刀对钛合金TC4进行铣削加工试验。试验结果表明：在硬质合金中添加微量合金碳化物TaC（NbC）,可以同时提高材料的高温硬度和高温断裂韧性,在相同的切削条件下,添加微量合金碳化物TaC（NbC）的硬质合金立铣刀比未添加微量合金碳化物的立铣刀耐磨性更好,刃口断裂裂纹更少,刀具使用寿命更长,更适合航空航天钛合金材料的高速铣削加工。