| The fuze is one of the important components of the rockets,and is a typical variable thickness umbrella-shaped parts.At present, the main production process is still to rely on the bar or pipe material to achieve the cutting part of the wall thickness changes, the production process there is a low utilization of materials, production efficiency, low performance parts,high production costs of the practical problems. To solve the problem of the backwardness of the production process of the parts, per the structural characteristics of the fuze parts and the material properties, the warm extruding mold with variable thickness of the umbrella was developed. By optimizing the mold structure and process parameters, it can improve the utilization rate of material from 17% to 45%, and the production efficiency is more than 1times. The internal organization of the workpiece is even and the performance is improved. It can not only solve the problem of "three low and one high" in mechanical processing, but also can realize clean, civilized and automatic production, which is of great significance to the production enterprise. But the life of the punch mandrel is only 2000-3000 pieces, an increase of mold costs and reduce the production efficiency, limiting the application of this technology to promote the main obstacles.In this paper, the premature failure of the punch mandrel in trial production is analyzed and the main forms of punch failure are analyzed, including shear fracture and wear failure.Shear fracture occurs near the working zone, mainly due to the stress concentration during the forming process and the rough wall thickness caused by excessive bending caused. And the stress concentration is reduced by optimizing the mold structure. The calculation criterion of the wall thickness difference of the forging is established per the high temperaturemechanical properties of the mold material and the simulation technology, and the safety margin of the wall thickness difference is determined to be ± 1mm. Per the mechanism of wear occurrence and development, the main influencing factors are found to be the increase of mold temperature and the decrease of hardness. The main methods to relieve the wear are put forward: cooling, Lubrication and mold surface treatment.Application of water-based graphite lubricant quantitative spray can achieve mold cooling and lubrication, the need to determine the rough between the heat transfer between the mold and the relationship. A one-dimensional unsteady heat conduction model with frictional heat generation and plastic deformation heat internal heat source is established, which can accurately calculate the heat transfer during the forming process. In this paper, the calculation of the mold to absorb heat in a single forming process, to determine a reasonable amount of lubricant coating to achieve the cooling and lubrication of the mold.Increasing the surface hardness of the mold is an important means to reduce the formation of high temperature abrasive wear. The optimum process of laser melting of H13 hot work mold steel was determined by experiments. The surface hardness of the mold was improved by laser melting 5-7 HRC, which could effectively resist the oxide scale scratches and slow down the formation of high temperature abrasive wear.Combined with the main research results of the pilot production, mold life from 3,000 to10,000 or more, to extend the life of the mold of the study. The surface damage of the mold surface was obviously reduced by SEM and EDS observation, and it was found that the use of water-based graphite lubricant quantitative spray technology and laser melting technology can effectively alleviate the mold failure caused by high temperature abrasive wear, mold life improved more than 3 times. Through the above research, the problem of rapid damage failure of warm extruding mold is solved, which is of great significance in the popularization of warm extruding mold technology. |
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