The influencing factors of additive manufacturing process are summarized
Date：2018/08/20Type：Company News
Keywords：广东大宏新材,金属粉末注射成形,MIM技术,MIM新材料,粉末冶金,精密复杂零件,精密结构件,一次成形,脱脂烧结,MIM手机零件,MIM智能穿戴,MIM陶瓷应用,MIM汽车零件,MIM医疗器械，粉末冶金微型齿轮，粉末冶金小模数齿轮
Comprehensive before two article about increasing material manufacturing, namely the introduction of metal material manufacturing technology process method "and" the simple analysis the main factors affecting the material manufacturing process ", using a material manufacturing technology for processing the workpiece, first of all, according to the properties of the materials selected parameters such as heat source type, power and scanning speed, then put the materials by transmission device is placed in the processing zones, and gradually shape under the action of heat. The manufacturing process of additive materials is a discontinuous process. The stability and consistency of the process are the key to its success or failure. The stability and consistency of the product processing shall be ensured by the combined action of materials, heat sources and technological processes. In the process of additive manufacturing, the type, power and scanning speed of general heat source are constant, that is, the heat source formed by the material is stable and consistent during processing. During the processing, the heat source will interact with the powder and the substrate of the formed area at the same time. However, the interaction between the heat source and the matrix becomes more obvious when direct powder feeding is adopted.
No matter which way the powder is placed in the forming area, the total amount of action of the heat on the powder is stable in the same action area and space. When the heat source ACTS on the material, it is affected by the mechanism of action and factors such as particle size, sphericity and surface state of the material. Therefore, the stability of the additive manufacturing process is ultimately determined by the stability and consistency of the material. The better the consistency of the material, the more stable the metallurgical changes in the material during the processing, so as to ensure the material changes and the final performance in the scanning path are more stable and consistent. For powder materials, the consistency of performance not only includes the consistency of general properties such as chemical composition, structure and mechanical properties of the materials, but also its morphological characteristics, such as particle size, sphericity and other factors are also important indicators. The most ideal powder for additive manufacturing should be of the same size and shape. Due to the limitations of production process and method, it is difficult to use a completely consistent material in practical production. In order to ensure the stability of the process, the metallurgical changes of the mixed powder in the process should be controlled within a reasonable range.
According to the characteristics of additive manufacturing technology, k is a constant. When Q supply /Q needs to be equal to 1, it is the most ideal working state. Under the action of heat source, the material will not overheat or underheat. When the Q supply /Q needs >, 1, it indicates that the supply of heat source in the processing process exceeds the demand, and the excess energy will heat the powder to a temperature higher than the required temperature for molding. When Q supply /Q needs to be <1, the energy supply is insufficient. As the diameter of the powder is smaller, under the same parameters, the greater the ratio of Q supply /Q demand, that is, the greater the excess energy supply, the easier it is to overheat in the forming process. Excessive heating may cause excessive melting of materials, excessively high temperature of molten pool, and the flow situation of molten metal in molten pool becomes more complicated, which may cause splashes of molten metal, and higher temperature is more likely to cause burning loss of alloy elements, and even lead to the reaction of elements and protective gas to introduce inclusions and other problems. The smaller the diameter of the powder, the larger the specific surface area, the easier the agglomeration phenomenon, the agglomeration of the powder will greatly reduce the powder transferability.
After metal is melted, spheroidization will occur easily due to the effect of surface tension. As the cooling speed is fast in forming, spheroidization may be completely retained, resulting in decreased surface quality of workpiece. In serious cases, the processing cannot be carried out. It was found in actual production that the degree of spheroidization in processing increased with the proportion of fine powder in powder. When the powder diameter is too large, the energy obtained in the heating process cannot sufficiently heat the powder to the ideal molding temperature, which may lead to incomplete metallurgical changes of the material, affect the bonding force between materials, and reduce the density of the workpiece. When the powder diameter reaches a critical value, the molding process will be completely impossible. According to the change rule of the function, the change of the function is relatively flat in the adjacent area with d0 as the middle, and the ratio of energy supply to demand deviates from the ideal state relatively less, which is conducive to maintaining the stability of the additive manufacturing process. It can be inferred that the particle size distribution of powder materials for additive manufacturing should be within a narrow range. This is in line with the actual situation that the particle size of the powder used to manufacture additive materials is usually between 200 and 500.
To sum up, guangdong dahong new material has made the following three conclusions on additive manufacturing technology：
1、Additive manufacturing is a new forming technology and material is the main factor that restricts the extensive application of additive manufacturing technology.
2、There is no essential difference between powder materials for additive manufacturing and powder metallurgy, but the particle size distribution is more strict and should be controlled within a narrow range.
3、The particle size and particle size distribution of powder for additive manufacturing are determined by heat source type and forming parameters.
For more information on powder metallurgy of metals, please consult guangdong dahong new materials.
