Liquid Model Forging of Parts Defects and Prevention: extrusion segregation
Abstract
This paper focuses on liquid model forging defects and prevention, particularly extrusion segregation. In the production process of liquid model forging, many problems can occur, such as porosity, unclosed voids, and other defects. These defects can be avoided if effective production method and technologies are used. Commonly used methods to reduce and prevent segregation are mold temperature control, flow balance, and advanced techniques. The paper explains the conditions and effects of extrusion segregation and introduce different techniques on how to prevent it.
Introduction
Liquid model forging is a process of forming and manufacturing parts with liquid materials. It is required to ensure the uniformity, strength, and dimensional accuracy of the liquid materials before the forming process starts. During the production process, the liquid materials are poured, heated and pressed into the desired shape through a mold. As the mold’s temperature and pressure change, the liquid material undergoes a gradual solidification process. The main issue of liquid model forging is extrusion segregation. It can occur in two situations: first, when the molten material is poured into the mold and the molten material segregates due to the difference in temperature between the two sections of the mold; second, when the molten material is extruded under pressure in the mold, the cooling rate is different, leading to segregation.
Effects of segregation
Segregation of the liquid materials during liquid model forging results in a mechanical and a dimensional structure of the forging parts that deviate from that specified by the design. The phenomenon of segregation can cause differential shrinkage or shortening of the casting parts. The resulting strain can cause deformation and misalignment of the casting parts, which directly affects the strength, toughness, and service life of the casting parts. In addition, the grain structure of the materials may also be changed, which affects the physical properties of the casting parts and causes stress concentration.
Prevention of segregation
Segregation of the liquid materials during liquid model forging can be prevented by using a suitable production process and related production technology. The most commonly used methods are mold temperature control, flow balance, and advanced techniques.
Mold temperature control
Mold temperature control is a simple and effective technique to prevent segregation. It helps to achieve the uniform temperature distribution in the mold and ensures that the parts produced have the same composition and structure. Generally, it is necessary to monitor the temperature of the molten materials during the whole molding process so that the temperatures of the two sections of the mold can be kept as close as possible, thus ensuring uniform temperature distribution in the mold.
Flow balance
Flow balance is a technique used to control the flow rate of the molten materials during the molding process. It has been found from experiments that the segregation of the molten materials can be prevented when the materials are poured at high flow rates and low flow rates. The high flow rate decreases the level of segregation by quickly filling up the cavity and maintaining the uniform temperature of the molten material. The low flow rate enables the molten material to slowly spread before solidifying, thus reducing the chances of segregation during solidification.
Advanced techniques
Advanced techniques such as laser cladding and surface alloying are used to prevent segregation in liquid model forging. These techniques are used to add an additional layer or alloy coating to the surface of the parts which reduces the occurrence of segregation. These techniques can improve the surface properties of the parts and thus enhance their dimensional accuracy.
Conclusion
The phenomena of segregation can be avoided if effective production method and technologies are used. The most commonly used techniques are mold temperature control, flow balance, and advanced techniques such as laser cladding and surface alloying. These techniques not only prevent segregation but also improve the surface properties and dimensional accuracy of the parts. Thus, by using these techniques and appropriate control measures, manufacturers can ensure that the parts produced are of good quality and meet the required design and performance specifications.
