Numerical Simulation On Composite Forming Process Of Forging And Casting For Non-quenched And Tempered Steel Crankshaft Blank

As the core component of auto engine,the commonly used crankshafts mainly include forged steel crankshafts and ductile iron crankshafts.Forging steel has higher bending fatigue strength due to strong metal fiber streamline.With lower production cost,the ductile iron crankshaft has relatively bad anti-fatigue performance due to shrinkage defects.The main reason for the high cost of the forged steel crankshaft is bad material utilization,low production efficiency,high tooling expense.This paper presents a new process method for producing the crankshaft: the non-quenched and tempered steel crankshaft blank with casting and forging composite forming process method.The forging and casting forming process combines the advantages of the casting process and the forging process while allowing the parts to be shaped and modified.Forging can eliminate casting defects such as shrinkage porosity and shrinkage cavities inside the casting,so that the grains can be refined,the metal structure can be dense,the cast structure inside the casting can be transformed into a forged structure,and the complete metal fiber streamline can be preserved.This paper adapts finite element numerical simulation technology to simulate the forming process of the crankshaft,and verifies the superiority of the casting and forging compound forming process.The non-quenched and tempered steel crankshafts studied in this paper are newly developed steel crankshafts in recent years.Non-quenched and tempered steel refers to the addition of V,Nb,Ti and other alloying elements in medium-carbon manganese steel to increase the strength of the steel.The advantage of non-quenched and tempered steel is that it can eliminate the subsequent quenching and tempering treatment process,simplify the process while improving cutting performance,and environment friendly.The main research contents of this paper are as follows:1.The crankshaft pre-forging blank casting is a preform before final forging.The structural shape of the crankshaft pre-forging blank casting is a key factor affecting the crankshaft forming quality.This paper sets 3 schemes with different crankshaft pre-forged billet casting structure and outline.DEFORM-3D software is involved to carry out numerical simulation analysis of the forging shape process of the three schemes,and the best scheme is determined.2.The size of the crankshaft pre-forging blank casting connecting rod journal and main journal inner corners are key factors affecting the quality of the crankshaft.The fillet radii of the three schemes are 5,7.5 and 10 cm,respectively,and we use DEFORM-3D software to carry on the numerical simulation analysis of the forging shape craft process.The load-stroke curves,stress-strain maps,temperature field distribution maps,metal flow status maps,damaged material distribution maps and folding diagrams of the forging process with different fillet radius solutions are obtained.Comprehensive analysis shows that the forming effect is best when the corner radius is 10 cm.3.The forging temperature has a great influence on the forming process of the crankshaft forgings.In this paper,DEFORM-3D software is used to simulate the forging process of 5 different forging temperatures of 1050,1080,1100,1130,and 1150℃,and different forging temperature schemes are obtained.The load-stroke curves,stress-strain maps,temperature field maps,metal flow diagrams and material damage maps.Comprehensive analysis of the simulation results shows that the forming effect is optimal at a die forging temperature of 1130℃.4.The possible casting forming process of crankshaft pre-forged billet castings is analyzed and compared.The AnyCasting software is used to optimize the casting forming process and the iron-clad sand casting process is finally determined.In this paper,two injection schemes: step injection and middle injection are designed and the size of the gating system,the size of the riser and the size of the cold iron under the two schemes are calculated.Using AnyCasting software for filling and solidification process analysis,it is determined that the intermediate injection type gating system scheme is more suitable for the casting scheme of non-tempered steel crankshaft pre-forging blank castings.5.Not only the casting process has an impact on the quality of the casting,but also the pouring speed and the pouring temperature have a great influence on it.In this paper,10 different pouring temperatures are designed for 1510,1520,1540,1560,1580,1600,1620,1640,1660 and 1680℃ and calculated with AnyCasting software.The program conducts numerical simulation analysis of the casting process.Four different pouring speed schemes of 1.2,1.3,1.4,1.5,1.6,1.7 and 1.8 m/s are designed and used by AnyCasting software.A different casting speed scheme is used for numerical simulation analysis of the casting process.By simulating the casting forming process of castings at different casting speeds and pouring temperatures,and analyzing the distribution of defects after solidification,the following concludes: The molten metal is poured at a casting temperature of 1640 ℃.Casting formed crankshaft pre-forged billet castings have the least casting defects such as shrinkage porosity and shrinkage.Therefore,the optimum pouring temperature is determined to be 1640℃.The clinker is poured at a casting speed of 1.6 m/s.The casting shrinkage of the forged billet has the least shrinkage,and the best casting speed is 1.6 m/s.The corresponding pouring time is 4.20s.