The main influencing factors of additive manufacturing process were analyzed

At present, metal materials are still widely used in industrial production. Additive manufacturing technology is used to replace traditional process methods. Manufacturing metal parts difficult to be processed by various traditional processing methods is an important development direction of additive manufacturing technology at present. Different from the traditional process methods, additive manufacturing technology has higher requirements on the properties and applicability of materials. However, as the industrial foundation, metallic powder material has become an important factor that restricts the rapid development of additive manufacturing industry in China. Although there are many technical methods to realize additive manufacturing, the processing mechanism is basically the same, that is, the material melts rapidly under the action of high-energy heat source. Due to the short acting time, the molten metal solidifies rapidly under the cooling action of the matrix, so as to realize the formation in a specific scanning area. The energy of additive manufacturing products is determined by the properties of heat source, material properties and process parameters.

Now by guangdong dhonghong new material editor to increase the process of the impact of the detailed analysis of the process：

1、The heat source

In the field of metal additive manufacturing, the most mature heat source is laser and high-energy electron beam. The working principle of electron beam and laser is different. The heating mode of electron beam is that high-energy electrons pass through the surface of the target material and enter a certain depth from the surface of the target, and then transmit energy to the target atom, which intensifies the vibration of the target atom and converts the kinetic energy of electrons into thermal energy. The heating mode of the laser is to absorb the energy of photons on the surface of the target, and the laser does not pass through the surface of the target. In the process of material manufacturing, the power and scanning speed of the heat source are generally constant, that is, the energy density acting on the material is constant. The absorption of heat energy by materials is determined by the mechanism of action and surface state of materials. For the most commonly used laser heat source, the absorption of laser light energy is related to the wavelength, reflectance and energy density of the materials. In the forming process, the surface state and size of the materials have obvious constraints on the laser. Due to the different mechanism of action, electron beam has better adaptability than laser in the process of additive manufacturing.

2、Material

Powder materials are the most commonly used materials for metal additive manufacturing. Metal powder is the most important link in the manufacturing industry chain of metal parts additive, and is also the most valuable place. Metal powder materials are generally used in powder metallurgy industry. Powder metallurgy molding is the final finalization of powder by using high pressure and high temperature conditions after preforming. In the whole process, physical metallurgy changes of materials are relatively slow, and materials have sufficient time for fusion, diffusion and reaction. Due to the limitation of temperature and pressure during powder metallurgy processing, in order to ensure the compactness of the workpiece, the powder material should be used to fill the mold cavity as completely as possible. According to the technical characteristics of powder metallurgy technology, a set of more perfect powder evaluation methods and standards have been developed, and relatively perfect indexes can be used to quantify the properties of powder materials, such as particle size, specific surface area, particle size distribution, powder density, velocity, loose pack density, porosity, etc. For powder metallurgy, the fluidity of powder and the density of vibration are important indexes for the measurement of powder materials for powder metallurgy.

3、The technological process

When the powder filling method adopts the powder laying method, the heat source ACTS on the powder first. In order to ensure the full metallurgical combination between the powder and the formed area, it is necessary to ensure that the depth and size of the molten pool in the processing process are within a reasonable range. When adopting synchronous powder feeding mode, whether coaxial or lateral powder feeding mode, the effect of heat on the material is divided into two parts: acting on the formed area and acting on the powder material. When the powder is heated to a certain temperature by a heat source on the way of motion, it is driven into the formed area under the action of its own kinetic energy. The whole molding process is equivalent to the process of bombarding the fusion area with relatively high-energy powder materials. This method is more conducive to improving the density of the product than the way of powder spreading.

Compared with powder metallurgy process, additive manufacturing process has obvious difference. The metallurgy change of powder material under the action of heat source is extremely rapid. In the forming process, the powder material and heat source directly act, and the powder material does not have the constraint of mold and the action of external persistent pressure. It is generally believed that powder materials with diameter less than 1mm are suitable for additive manufacturing, and powder materials with particle diameter of about 50 mm m have better molding performance. Compared with the powder metallurgy industry, there is no mature evaluation method or standard in China to determine the applicability of powder materials and additive manufacturing process.

If you want to know more about metal powder metallurgy, please consult guangdong dahong new materials.