【作者】 吴劲锋；

【导师】 黄建龙；

【作者基本信息】 兰州理工大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 环模是制粒机的核心部件,加工苜蓿草颗粒的环模寿命只有加工配合饲料颗粒的四分之一。在环模草颗粒制粒过程中,由于草粉对环模磨粒磨损,当颗粒的成型率下降至75%时,产生环模失效。本文在农业部牧草产业化生产关键技术装备研究项目的支持下,对环模磨损失效机理、苜蓿草粉对金属材料的磨损机理、环模力学特性及对结构的影响进行研究,并取得了重要研究成果。1.通过对环模失效的分析研究,揭示了制粒环模失效机理是环模表面在塑性变形和显微切削两种磨损机制作用下产生表面的材料流失;2.通过对不同金属材料的抗苜蓿草粉磨粒磨损行为的研究,苜蓿草粉磨料对金属材料的磨损有两种不同的磨损机制,在硬磨料磨损条件下,以显微切削机制为主导,在软磨料磨损条件下,以多次塑性变形机制和低周期疲劳机制为主导;3.试验研究发现,提高金属材料抗植物材料磨料磨损抗力不是简单地提高金属材料表面的硬度,而是应综合考虑金属材料的硬度与韧性的合理配合,即在本试验条件下,45~#钢硬度HRC50.67,韧度0.69kgfm:4.确定了45~#钢的抗苜蓿草粉磨粒磨损的热处理制度即:45~#钢亚温淬火比常温淬火能提高耐磨性;45~#钢抗苜蓿草粉磨损最佳热处理工艺为:840℃保温30min水淬,550℃回火后水冷预处理;770℃加热5-6min,水淬,200℃回火2小时。5.通过对环模制粒过程的力学特性分析和挤出力与制粒密度的关系研究,建立了进行环模结构优化设计的数理模型,为环模结构设计提供了理论依据。本论文的研究成果开创了植物材料对金属材料磨料磨损机理研究的新领域,为农业机械、饲料加工机械的设计制造中的材料选择、热处理工艺的制定提供了理论依据。更多还原

【Abstract】 Circular mold is the core part of the Pelletier, when it is used to produce the alfalfa grass powder, the life of circular mold is only 1/4 of that processing mixed feed pellet. During the process of producing grass powder, because of the abrasion of grass powder to circular mold, the circular mold expires when the pellet formation rate drops to 75%. Supported by forage grass seed items of basic construction under the Ministry of Agriculture, this article does the research of the wear failure mechanism of circular mold, the abrasion mechanism of alfalfa grass powder to metallic material, and the influence of the mechanics characteristic of circular mold to its structure, and has obtained the important research results.1. Through analyzing and studying the expiration of the circular mold, it is revealed that the failure mechanism of circular mold is a superficial material outflow caused by the functioning of two attrition mechanisms which are plastic deformation and micro cuts in circular mold surface.2. By studying the abrasive attrition behaviors of alfalfa grass powder to different metallic material, it is found that the alfalfa grass powder to the metallic material has two kinds of different attrition mechanism, under the hard grinding abrasion condition, the micro-cutting mechanism dominates while under the soft grinding abrasion condition, the multiple plastic deformation mechanism and the low cyclical weary mechanism do.3. The experimental study indicates that the enhancement of the wear resistance of metallic material to plant material grinding abrasion can not simply lead to the enhancement of the metallic material surface hardness, but an overall evaluation of the reasonable coordination of metallic material degree of hardness and tough should be given. Hence under this test condition, degree of hardness of 45~# steel is HRC50.67, tenacity is 0.69kgfm;4. The heat treatment system is determined in abrasive wears of 45 steel to alfalfa grass powder. The subcritical quenches of 45 steel can better improve the wear resistance than normal temperature quenching. The most reasonable quenching condition of 45~# steel is: keeping warm with 840 0C for 30 minutes then quenching in water, tempering with 550 0C then watering cooling pretreatment, heating up 5-6min with 770 0C and tempering 2 hours with 2000C.5. By analyzing the mechanics characteristic of circular mould and the relationship between out strength and the density of palletizing, the mathematical model of circular mold’s structure optimization design is established, which will provide the theory basis for the circular mold’s structural design.The results of this paper creates a new domain in grinding abrasion mechanism research on plant material to the metallic material, and it provides the theory basis for the choice of material and design of heat treatment craft in the farm machinery and the feed process machinery.更多还原