【作者】 周天宝；

【导师】 吴劲锋；

【作者基本信息】 甘肃农业大学 ， 农业机械化工程， 2008， 硕士

【摘要】 材料的磨损是机械产品中常见的失效形式,每年给社会带来巨大的经济损失。我国采用加工配合饲料的环模制粒机生产苜蓿草颗粒,作为苜蓿饲草产品加工利用的主要方式,已解决了苜蓿产业化生产中贮藏、运输及饲喂的问题。但是,由于苜蓿的物理机械性能与普通饲料不同,因此在用加工配合饲料的颗粒机加工苜蓿草颗粒的生产实践中,颗粒机环模的磨损非常严重,即环模抗苜蓿草粉的耐磨性较低,其产量只有生产配合饲料产量的四分之一左右,这便增加了苜蓿草颗粒产品的生产成本。环模制粒机的环模选材多以优质合金钢为原材料,其成本昂贵,这无形中也增加了饲料企业产品的生产成本。以价格低廉的优质碳素结构钢45#钢作为制造环模的代表材料,并把45#钢作为抗苜蓿草粉磨损性能比较的参照材料,为以后的抗苜蓿金属材料的磨损做基础工作。因此,分析研究颗粒机环模磨损失效的原因,以及苜蓿草粉对金属材料的磨损性能的影响,对提高颗粒机环模的使用寿命有现实意义。本课题的主要工作有以下几方面,①分析环模失效形式,从宏观上观测实际环模失效机理,从磨损形貌上进一步分析其失效原因;②对45#钢毛坯件进行化验,确定其毛坯件本身无缺陷;③以选定的热处理方案进行淬火处理,首先将四组试件统一做组织均一化的预热处理,使其晶粒细化,组织结构统一,其次将四组试件按预定方案做常规淬火热处理和亚温淬火热处理,再低温回火,并测得各试件硬度值;④对试件做冲击试验,求得其平均韧度值;⑤进行磨料磨损失重试验,主要从质量损失上观察耐磨性优劣情况,用电子扫描显微镜观察磨损面的宏观磨损状况,判断磨损机理,再运用金相显微镜从金相组织方面分析解释耐磨性的原因,进一步验证试验结果。最后得到试验结论,结论如下:(1)由于磨损使得环模产生孔径增大、进料倒角被磨损、模孔内壁凹凸不平、壁厚减小,强度降低4种结构失效现象,导致了颗粒形成的受力关系的变化而最终导致环模失效;(2)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,造成环模的磨损失效。(3)淬火后的45#钢抗苜蓿草粉的耐磨性要优于未经淬火热处理的试件,耐磨性最好的是亚温淬火的试件;(4)苜蓿草粉磨粒对未经热处理的45#钢金属材料表面的磨损为硬、软磨粒共同作用的结果,在硬磨料磨损条件下以显微切削为主要磨损机制,在软磨粒磨损条件下以多次塑性变形和低周期疲劳为主要磨损机制,经过热处理之后的试件的磨粒磨损仍然以显微切削机制为主导,塑性疲劳磨损不明显;(5)在苜蓿草粉磨料对45#钢的磨粒磨损实验中,单一的提高硬度不是提高耐磨性的有效途径,硬度、塑性、韧度的合理配合能提高45#钢的抗苜蓿草粉磨粒磨损能力。更多还原

【Abstract】 The attrition of the material is the common expiration form in the mechanical product, and brings the huge economic loss to the society every year. Using the circular mold Pelletier producing the mixed feed to product the alfalfa grass pellet in our country, as the main expiration form on product and utilize the alfalfa forage product, which has solved the problem of stores, transports and feeds on the process of the alfalfa industrialization. But in production practice of using the Pelletier of the mixed feed to product the alfalfa grass pellet, the attrition of circular mold is extremely serious, that is to say the abrasive resistance of circular mold is low in wearing alfalfa grass pellet, its output only about 1/4 of that of the mixed feed, and increases the production cost of grass pellet because the alfalfa’s physical and mechanical property is different from the ordinary feed. The material of the circular mold Pelletier machine mostly takes the high quality alloy steel as the raw material, its cost is expensive, and which increases the cost of enterprise’s product in some way. Using the high quality carbon structural steel 45# steel which low in price as the circular mold’s representative material and the reference material with alfalfa grass powder in attrition performance, which is the foundation work for the later anti-alfalfa metallic material’s attrition. Therefore, analyzing the expiration reason of circular mold, studying the influence of the alfalfa grass powder’s wear performance with the metal material, which have the practical significance to enhances the circular mold’s service life.This topic’s prime task has the following several aspects,①Analyzes circular mold expiration form, observe the actual circular mold expiration mechanism from macroscopic, and further analyzes its expiration reason from the attrition appearance;②Carries on the chemical examination of the 45# steel’s raw materials, determined that its raw materials itself does not have the flaw;③Carries on quenching processing using the designated heat treatment plan, firstly makes the micro-structure homogenizing preheating processing for four group of test sample, causes its grain refining, and the micro-structure to be unified, next makes the conventional quenching heat treatment and the subcritical quenches heat treatment for four groups of test samples according to the predetermined plan and tempering ,and then obtains various test samples degree of hardness value;④Performs the impact test to the test sample, obtains its average tenacity value;⑤Carries on the grinding abrasion weightlessness experiment, mainly observes the wear resistant situation whether good or bad from the mass defect, with the scanning electronic microscope to observe the wearing surface’s macroscopic wear condition, to judge the abrasion mechanism, and analyzes and explains the reason of wear resistant again using the micro-structure microscope from the microstructure aspect, further confirms the test result. Finally obtains the experimental conclusion, the conclusion is as follows:(1) Because the circular mold is wore, and causes the aperture is increased, feeding bevel edge is worn, the endophragm of model hole is uneven, and the inside diameter is increased, wall thickness reduces .those 4 kinds of structure expiration phenomenon caused the granulation stress relations changed and finally causes the circular mold expiration;(2) The plastic deformation and micro cuts produce the circular mold surface superficial material is drained under two kind of attrition mechanisms function , finally creates the circular mold’s attrition expiration.(3) The test sample’s wear resistance of quenched 45# steel to alfalfa grass powder is better than that of unquenched, what the wear resistance is best is the subcritical quenches heat treatment test sample;(4)The surface attrition of the alfalfa grass powder grinding compound to metal material—45# steel are the result of the hard and soft abrasive simultaneously, under the condition of hard abrasive, the wear is mainly the micro-cutting wearing, while it is dominated by the plastic deformation many times and the low cycle fatigue wear in the case of soft abrasive. When the test sample were quenched, the wear is mainly the micro-cutting wearing either, the plastic deformation weary which is the grass powder grinding medium to 45 # steel is not obvious. (5) In the abrasive attrition experiment of the alfalfa grass powder grinding to the 45# steel, sole enhances hardness is not the effective way of enhancing the wear resistant, the reasonable coordination of hardness, the plasticity and toughness can improve the attrition ability of 45 # steel to resistance alfalfa grass powder.更多还原