The Influence of Temperature Parameters on the Quality of Liquid-Forged Parts
Abstract
The liquid-forging process can be used to produce parts with superior strength and surface finish compared with conventional forging technologies. The temperature of the forging materials is one of the most important factors in this process, and the influence of furnace temperature and working temperature on the quality of liquid-forged parts need tobe further studied. By simulating the stress-strain relationships of liquid-forged parts in the finite element analysis software, this paper analyzes the influence of furnace temperature, working temperature, stirring and cooling rate on the strength and surface finish of liquid-forged parts, and puts forward the optimal temperature production process parameters reasonable.
Introduction
Liquid-forging is a kind of forging technology by part forging parts in liquid state. The parts forged by this process have good compressive strength and surface finish, which is superior to that of the parts forged by the traditional cold-forging and warm-forging processes. Temperature plays an important role in this process. Regulation of the liquid material temperature can improve the performance of the parts, and reasonable temperature control can reduce production cost and improve product quality.
The physically-based mechanical model and numerical simulation are widely used for research of liquid-forging temperature. Zhao et al. (2000) studied the rumpling processes of blank by numerical simulation. Zhuang et al. (2012) used a simplified physical model to simulate the temperature process of liquid-forging. Zhao et al. (2013) used the numerical simulation technology to analyze and study the force effect on the blank in a rumpling process.
The physical and numerical simulation research can provide a powerful means of understanding the temperature parameters influence on liquid-forging process. In this study, after analyzing the facts, the finite element numerical simulation software is used to simulate and research the rumpling process of liquid-forge parts. Through researching the temperature parameters’ influence on the strength and surface finish of liquid-forging parts, the optimal process parameters are proposed, and the liquid-forging temperature parameters are optimized.
Theoretical Analysis
The material temperature is an important influencing factor in liquid-forging. In general, when the temperature is above the melting point, it is in the liquid state and can be forged by forging. When the forging material has a certain superheat temperature, the material has a certain plasticity and occupies the certain blanking cavity space. When the temperature is lower than the melting point, it is in the solid state and cannot be forged. Therefore, the temperature parameters of the process are the premise of liquid-forging process.
The temperature of the liquid-forging process has two parameters, furnace temperature and working temperature. The furnace temperature refers to the temperature of the liquid material at the entrance of the whole process. The liquid material put into the mold should be in the melting state. The melting temperature of different material is different. Therefore, the temperature of the liquid material should be higher than the melting point of the material at the entrance of the process. The working temperature is the temperature of the liquid material at the entrance of the process should be lower than the melting point after the liquid material is formed. After the material enters the process, the flow property of the liquid material is changed by the stirring in the process, and the external stretching force and compressive force such as the forging caused in the forging process make the material volume decrease, the easy to pull spacing extended, and the strain increases, so that the temperature of the material decreases until the temperature of the solid material is reached in a small deformation range.
In the actual liquid-forging process, the temperature should be determined according to the material itself. For materials with higher melting point, the temperature should be set higher; for materials with lower melting point, the temperature should be set lower. In addition, the cooling rate is also an important factor to be considered. If the cooling rate is too fast, the strain of the material becomes large and the material cracks easily, resulting in low product quality. Therefore, the cooling rate should be selected reasonably according to the material.
Process Simulation and Results
In order to study the influence of temperature parameters on the quality of liquid-forging parts, the finite element method is used to simulate the rumpling process of liquid-forged parts. The simulation model is shown in Figure 1. In theprocess modeling, the material properties, stress-strain relationship and friction characterization consider about the forging temperature.
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