Research On Design Of Flux-Cored Wire For Repairing Automobile Hot Forging Dies

Hot forging dies have poor service conditions and are prone to wear,cracking and deformation,leading to scrapping.Due to the long manufacturing cycle and high cost of new molds,repair and remanufacturing are often used to extend their service life.The quality of the hot forging die repair wire directly determines the quality of the mold repair,but in terms of the design of the hot forging die repair flux-cored wire,the performance indicators and quality stability of domestic products are far from foreign countries.As a result,the service life of the hot forging die after repair is not high.In view of this,through theoretical analysis,numerical simulation and experimental research,the performance and nominal composition design of hot forging die repair welding wire,as well as the preparation method of welding wire and rare earth modification research were carried out,and a positive welding wire formula design method was proposed.A flux-cored wire for surfacing repair of hot forging die with excellent performance has been successfully applied in the 5CrNiMo die repair experiment.The main research work is as follows:Taking the hot die of vehicle steering knuckle as the research object,DEFORM software was used to simulate its forging process,and the relevant temperature field distribution law was obtained.Combined with the conventional failure mode of hot forging die,the final performance index of the die repair wire was determined.Referring to the comprehensive performance of two types of hot forging dies in the market to repair the welding wire,the target welding wire hardness,high temperature strength,impact toughness and thermal stability were quantitatively designed.Based on the preparation process of flux-cored welding wire by steel strip method,and definition formula of transition coefficient,a theoretical method for accurately converting the formula of the welding wire to be obtained by parameters such as raw material composition,nominal composition and transition coefficient was proposed.At the same time,in order to improve the manufacturability of welding wire additive,extreme attitude welding experiments were carried out,the influence of slag-forming agent content on weld bead morphology was studied,and the target welding wire slag-forming agent content was determined.JMat Pro software was used to analyze the influence of key alloying elements Cr,Cr/Mo and Co content on CCT curve and the second phase in the quenched and tempered state,and the design range of Cr,Cr/Mo and Co was narrowed.Based on the surface response method,aiming at the metal hardness,600 ℃ tensile strength,impact toughness and thermal stability of the welding wire,the element contents of Cr,Cr/Mo and Co were optimized,and the optimal nominal composition of the welding wire and the corresponding basis formula were determined.The Gibbs free energy of reaction of rare earth elements [Ce],[Y] under the protection of [Al],[C],[Si] was calculated,and the possibility of [Ce],[Y] transition under welding was analyzed.The surfacing experiment of rare earth modified wire was carried out,and the transition coefficient of rare earth [Ce] was determined.Analysis of variance was carried out to determine the effect of rare earth ferrosilicon on the hardness of surfacing metal.The influence of rare earth ferrosilicon on the impact toughness and high temperature tensile properties of welding wire at 600℃was explored.Using rare earth modified welding wire,the 5CrNiMo mold surfacing repair experiment was carried out.The hardness and impact toughness of the bonding area between the repair layer and the substrate were tested,and the bonding quality of the repair layer and the substrate was verified.A high temperature friction and wear experiment was carried out,and the friction and wear properties of the designed welding wire were verified by using 5CrNiMo die steel as a reference.The research methods and results of the subject provide a reference for the design of welding wire formula,and have certain academic value and engineering guiding significance.