Process Optimizing Of Integral Casting And Heat Treatment For Cast Steel Axle Housing

The axle housing is a key part of the automobiles,which plays an important role in carrying the weight of the car and transmitting the load,the safety performance and service life of automobiles are directly affected with the quality of axle housing.In recent years,with the rapid development of China's automobile industry,there are more and more demand for high quality and high reliability drive axle housings,but the existing axle housing performance can not meet the practical use requirements of heavy-duty commercial vehicles.Therefore,there is an urgent need for a high-strength axle housing with a simple process and low cost to meet market's demand.This article is based on the demand of market,aims to design a new high-strength cast steel material which is specifically used to produce integrally cast axle housings with simple production process and low-cost.This article reviews and studies the effect of different alloying elements on the microstructure and properties of steel,designed an low alloy high strength cast steel based on carbon,silicon,manganese and chromium,at the same time add RE,Ti,B and other trace elements,named ZG27Mn2Si2CrB.In this paper,computer simulation technology is used to design and optimize the casting process to ensure the quality of castings,shorten the product trial cycle and reduce production costs.Meanwhile,research the flow state and regularity of metal liquid in cast mold,heat transfer and temperature gradient changes in the casting process,interfacial heat transfer conditions and interactions between castings and molds by numerical simulation.Provides an intuitive and scientific basis for the analysis of mold filling,solidification rules and defects formation mechanism of casting process.Determine the specific process parameters and optimize the process plan,for scientific forecast and optimize production.Achieve the goal of high quality,high efficiency,low power consumption and clean.We surveying and mapping CCT curve of the experimental steel by Gleeble3800thermal simulation instrument for more precise formulation of heat treatment process.Expreramental steel bainite transformation platform is wider and hardenability is good by analysis CCT Curves.Expreramental steel can obtain bainite and martensite at lower cold zone speeds.Then,we discuss the heat treatment process parameters of ZG27Mn2Si2CrB.We determine the annealing state as the initial state for heat treatment.Heat steel to 815°C(sub-temperature treatment)and 900°C(complete austenitizing treatment)for insulation after annealing pretreatment,then cool at different cooling rates and temper at different temperatures.We find that the mechanical properties of the expreramental steel after 815?sub-temperature treatment heat treatment is poor.The ferrite morphology and distribution deteriorate the performance of steel.And the mechanical properties of the expreramental steel after 900?heat treatment is good.We designed the subsequent heat treatment process by the CCT curve.The Annealed experimental steel heated to 900?and cooled by three cooling methods(air cooling,mist cooling,NJ cooling),then tempered experimental steel with different temperatures at 340??380??480??520?.Study the effect of cooling rate and tempering temperature on microstructure and mechanical properties of experimental steel.The experimental results show that bainite and martensite appear in the microstructure of the experimental steel after cooling by all of three cooling methods.Air-cooled steel contains more bainite and less martensite,and mist-cooled steel contains more martensite and less bainite,the microstructure of NJ-cooled steel is almost bainite,only little martensite.This paper optimizes two heat treatment processes that meet the design requirements.The Annealed experimental steel heated to 900?and cooled by air cooling,then tempering at 520°C,the steel exhibits mechanical properties?_b?1200 MPa,?%?13%,Hardness is 36.3 HRC.The Annealed experimental steel heated to 900?and cooled by NJ cooling,then tempering at 520°C,the steel exhibits mechanical properties?_b?1300 MPa,?%?11%,Hardness is 38.2 HRC.