【作者】 向红亮；

【导师】 罗吉荣；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2004， 博士

【摘要】 磨盘是高浓磨机中易损件,其使用寿命直接影响着纸浆质量和生产效率。本文研究开发一套长寿纸浆磨盘的精密成形新技术。获得的主要成果如下:系统研究了磨盘的失效模式和失效机理,发现纸浆磨盘的失效是由摩擦磨损、齿纹断裂、汽蚀、腐蚀及边缘磨损等几种失效模式复合作用引起的。摩擦磨损作为软磨料,主要由塑变疲劳引起,其过程首先是在基体与碳化物周围形成空洞,随着空洞的不断扩展,形成裂纹,裂纹不断扩展,相互连接,最终导致基体的剥落和碳化物的脱落。腐蚀不仅仅是齿与齿槽之间的电位差造成,还与材料基体与碳化物之间的电位差有关。对汽蚀失效进行了系统的理论分析,建立了形成汽蚀必要条件的判据。认为磨区的压力降造成汽泡的产生,是产生汽蚀的必要条件,而且建立了判据:≤0,当该公式成立时,容易产生汽泡。汽泡爆破冲击齿区。在汽泡爆破冲击力及射流的复合作用下,导致材料受损。研究了C、Cr、Mo以及Ni等元素对高铬合金材料性能的影响,随碳含量的增加,高铬合金材料硬度提高,冲击韧性降低。Cr含量的增加,硬度与冲击韧性都有所增加。随着Mo含量的增加,硬度跟冲击韧性都有所增加。随着Ni含量的增加,硬度递减,冲击韧性先增后减。筛选出一种优质的新型磨盘材料Cr27Mo2Ni-GT作为磨盘使用材料用于生产。采用电磁振荡法、旋转法、极化曲线法以及滑动摩擦法,研究了不同材料耐汽蚀、抗冲刷、耐腐蚀和抗磨等性能。发现片状碳化物在中性和碱性条件下,具有良好的抗汽蚀、耐腐蚀、抗冲刷以及耐摩擦磨损;网状的碳化物严重影响材料的性能,各项指标都处于最低状态。岛状碳化物比片状碳化物更耐腐蚀、耐汽蚀,但在耐摩擦和冲刷方面不如后者。同时探明马氏体组织具有比奥氏体好的耐腐、抗汽蚀以及抗冲刷的能力。 <WP=5>提出由具有激冷功能、强度高、发气性低的面砂和背砂组合的壳型精密铸造工艺,设计出成套的造型工艺装备,对浇注工艺参数进行了优化。确定小磨盘浇注温度为1520℃,浇注时间2-3s,浇道为半闭半式,F直:F横:F内为1.25:1:1.72。大磨盘浇注温度为1610℃,其F直:F横:F内为1:1.42:3.28。有效地防止气孔、缩孔、缩松以及冷隔的发生,稳定生产出尺寸精度CT8级,齿纹区表面粗糙度Ra3.2um的磨盘铸件,其使用寿命达到设计要求。采用本研究成果的精密成形技术生产的磨盘产品,已在国内广泛使用。更多还原

【Abstract】 Refiner plate is an easily broken part of high consistency disc refiner. Its service life span directly affects pulp quality and production efficiency. This paper studied the new precision form technology of long life pulp refiner plate. The main results followed as:Failure modes and theories of refiner plate were studied systematically. It was found that failure of refiner plate is caused by the compound action of wear abrasion, tooth breakage, erosion, corrosion and bar rounding etc. Wear abrasion is caused by galling fatigue. The procedure is that pore occurred at the side of matrix and carbide firstly. Then cracks begin to generate with pore extending. At last matrix and carbide fall off, because of crack extending and connecting. Corrosion is not only affected by potential difference between tooth and groove but also by between matrix and carbide.Erosion failure was systematically analyzed and the necessary condition criterion of erosion formation was deduced. It was considered that bubble generation is caused by pressure loss of refiner area, which is the necessary condition of erosion generation. The criterion is ≤0. When this formula value is less than or equal to zero, the bubble easily generates. Bubble blast attacks tooth area. The compound action of bubble blast and jet fluid results in material damage.The effects of element C, Cr, Mo and Ni on the properties of high chromium alloy material have been investigated. The more increases C content, the more improves hardness of high chromium alloy material and the less impact toughness. Hardness and impact toughness rise with increasing Cr and Mo. Hardness decreases with increasing Ni, but impact toughness firstly increases, then decreases. The new refiner plate material-Cr27Mo2Ni-GT is optimized and developed. By using ultrasonic vibratory method, rotating method, polarization curve method <WP=7>and sliding friction method, the different material properties of erosion resistance, corrosion resistance, scour resistance and frictional wear resistance were investigated. It was demonstrated the material with flaky carbide have good properties of erosion resistance, corrosion resistance, scour resistance and frictional wear resistance. Net carbide badly affects the material properties and results in every index being the lowest. Island carbide has better properties than flake carbide on corrosion consistence and erosion consistence. But its properties are not as good as material with flake carbide on scour resistance and frictional wear resistance. At the same time it was proved martensite structure has better properties than austenite on corrosion resistance, erosion resistance and scour resistance.It was presented that the shell precision casting process composed of back sand and facing sand with chilling, high strength and low gas-forming properties. A set of molding process and equipment was designed. Pouring parameters were optimized. Pouring temperature of small refiner plate was 1520℃. Pouring time was 2-3s. F直:F横:F内 was 1.25:1:1.72. Pouring temperature of large refiner plate was 1610℃. F直:F横:F内 was 1:1.42:3.28. Generation of pore by gas, shrinkage, dispersed shrinkage and cold shut was prevented by presents ways. Dimensional accuracy of stably produced casting was CT8. Tooth face roughness was Ra3.2um. Its life span met design requirement. Produced casting by using this precision process was extensively used in many plants.更多还原