Research Into The Failure Mechanism Of Circular Mould Of Pelletizer And Its Optimal Design

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.