Study On Thermal Process、Microstructure And Properties Of Surfacing Welding On ZG29MnMoNi Matrix Under Different Preheating Temperature

With its unique advantages of low production cost, high performance and longservice life, the steel castings dual hardfacing metal layer forging die has solved theproblem of large forging die’s manufacture and cost. And it has extensive appliedforeground and development space. However, dual metal layer surfacing is still in theresearch exploratory stage, there is no relevant experience and theory as a support. Thestudy of the influence of process parameters on surfacing welding quality, whichimproved the quality stability, shorten the development cycle of the die, reduce the costof production and increase the economic efficiency, as well as create conditions forfurther marketing of the product.This study takes the single-layer single-channel surfacing on ZG29MnMoNimatrix as the research object, and simulations of thermal processes for single-layersingle-channel surfacing are conducted under different preheating temperatures,meanwhile, microstructures and properties under different preheating temperatures areanalyzed.The first chapter of this paper introduces surfacing technology and application，characteristics of20MnMoNi， numerical simulation of welding thermal process,research status of preheat temperature, as well as the source of research subject andresearch content and route. The second chapter introduces the related means, of thetechnical route and the research train of thought.Based on the characteristic of simufact.welding finite element software，thethermal cycle and temperature field was numerical simulated under the experimentalconditions of single-layer single-channel surfacing welding in the third chapter.Comparison and analysis the changing rule of the welding thermal cycle andtemperature gradient under different preheating temperature according to the collecteddata from the results of numerical simulation:1) Cooling rate of the thermal cycledecreased according the increasing preheating temperature.2) Different preheatingtemperature got different thermal field in special area, especially near the fusion line,was significant.3) Preheating temperature had significant influence on the magnitudeand distribution of temperature，as well as the temperature gradient decreased with theincreasing of preheating temperature.The fourth chapter expounds the internal cause of the change rule, the microstructure and hardness according the increasing preheating temperature, by meansof the thermal cycle, temperature gradient and distribution of stress, which obtain by thethird chapter’s research results. The microstructure and hardness of the surfacingwelding under different preheating temperature presented the following changes：1)With the increase of preheating temperature, heat affected zone tissue presents thechange trend of martensite-bainite-pearlite, and the hardening tendency graduallybecome to be weakened.2) The linear distribution of the microhardness, whichperpendicular to the fusion line, gradually becomes smooth transition with the increaseof preheating temperature.In the last chapter of this paper, the QP-123casting-steel die coated is designed,manufactured and put on forging production according to the finite element simulationresults and experimental verification, which achieved good results, and provided theoryfoundation and production guidance for the preheating of surfacing hot forging die.