Study On Regionalized Laser Bionic Coupling Combination To Improve The Performance And Service Life Of B2 Large Forging Die

With the rapid development and change of China’s industrial level,4Cr2MoVNi die steel with high thermal stability and low price has been widely used in large hot forging dies.However,fatigue cracks and severe wear appear on the surface of the die due to the erosion and wear of the extrusion blank by the forging press and the hot and cold circulation on the die surface in the harsh working environment,resulting in the service life of the die being far less than the designed life.So,in the processing and manufacturing industry,it is of great application value and important practical significance to strengthen the surface of large-scale forging molds in different regions,enhance the surface’s fatigue resistance and wear resistance,improve the accuracy of molds and extend the service life.Through the actual investigation,it is found that in order to improve the surface wear resistance of the mold,the workshop usually carries on the overall strengthening treatment for the mold.However,there are obvious limitations of overall strengthening for large forging dies.First of all,after the mold is strengthened as a whole,the problem of serious surface wear of the mold cannot be solved;Secondly,deliberately increase the strengthening time,increase the thickness of the strengthening layer will waste processing resources,increase production costs.Finally,the overall hardness of the mold surface is increased,which causes the mechanical cracks to be exacerbated under the effect of cyclic stress,resulting in mold scrap.According to the theory of coupled bionics,it is concluded that during the evolution of thousands of years,organisms will form a non-smooth structure between soft and hard to resist the frictional contact brought by the living environment.Based on the previous research,this study combined with coupled bionics theory,and used laser fusion processing technology for the first time to prepare coupling bionic units with different structures and shapes on the surface of large-scale forging molds to improve the fatigue wear resistance of the mold surface.And compared with the traditional strengthening method,analyze the primary and secondary factors that affect the fatigue wear of the mold surface,and verify the practicality of the regional strengthening method in the actual production process.In this paper,the effects of the structure,shape and characteristic of the coupled bionic unit body on the fatigue resistance of 4Cr2MoVNi mold steel were studied.The surface of the mold was strengthened in different regions and its practicality was verified in actual production.In this study,three coupling biomimetic structures with the area proportion of 45%and 60%of the coupled biomimetic units are designed,which are striated and gridded,and the area proportion of 100%.In the experiment,the primary and secondary factors that affect the fatigue wear performance of the mold are summarized by controlling the single variable of thermal fatigue temperature,laser energy and coupled bionic model.The finite element software is used to simulate and analyze the temperature field,stress field and wear of the surface of large forging dies.According to the obtained rules,different coupling bionic unit body models were prepared on the surfaces with different temperatures,stresses and wear levels of the mold,and actual production tests were performed on the mold after the coupling bionic treatment.The results show that:firstly,the larger the proportion of the model area of the bionic coupling element body,the better the fatigue resistance of the specimen;The grid-like bionic coupling element model has better fatigue wear resistance than the stripe-like bionic coupling model;The grid-like bionic coupling unit model has better fatigue wear resistance than the stripe-like bionic coupling model;Of all the models,the specimens with close-packed structure have the best fatigue wear resistance.Secondly,under different fatigue temperature and laser energy tests,the research shows that the anti-fatigue of the bionic coupling sample with close-packed structure is the best,followed by the grid-like bionic coupling model,and finally the stripe-like bionic coupling type;The main factors affecting the amount of wear are the type of bionic coupling model>fatigue temperature>laser energy,and then three different laser energies of 153.5J/cm~2,161.3J/cm~2,and 174.5J/cm~2 were used on the mold surface to prepare different coupling bionic models.Finally,in the actual production process of the factory,it is found that after the production of the same number of forgings,different biomimetic coupling model combinations can be prepared according to the wear degree of different areas to enhance the anti-fatigue wear performance of the mold,so that the wear degree of the mold surface is consistent.In addition,the curve fitting of the theoretical production forgings of the mold with the bionic coupling surface is performed,and it is concluded that preparing different combinations of bionic coupling models by region can increase the mold life by 1.57-1.80 times.According to the characteristics of non-uniform fatigue and wear on the surface of large-scale molds,it is of great practical significance to prepare different bionic coupling model combinations to locally strengthen the mold performance,which can improve the service life of the mold.