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First, some intermediate institutions in China, including components and whole manufacturers. They undertake parts and components, and then find some manufacturers in the country to produce. Since the two blanks have different production processes, the current market price is different, and the latter's offer is generally higher than the former. If we do not distinguish between the two kinds of blanks, if we press the low price of the castings when we accept the business quotation, there will be operational errors, affecting the benefits and even losses; Second, the professional casting and forging manufacturers. Since the latter is a die-casting part, it can be produced by a conventional die-casting process and the business is taken over. After the die-casting mold was opened, finally, the blank produced by the die-casting process basically had shrinkage shrinkage defects or appearance defects, and the blank was unqualified, eventually causing undue loss.
2. Relationship between die-casting forging, liquid die forging and continuous casting and forging
The essence of the continuous casting and forging process is that in one piece of equipment, in the same set of molds, the casting filling and forging are continuously completed. The continuous casting and forging process is not a new process, and its principle has a long history. The most typical and simple continuous casting and forging process is the familiar liquid die forging (melting forging) process. The die-casting forging process, in a visual sense, is a liquid die forging that is as complex as a conventional die-casting part with a special equipment with a higher degree of automation. Because of this, it is not easy to separate the die-casting forgings from the ordinary die-casting parts. Similar to the quality of the blank produced by the continuous casting and forging process, it is the “first casting and then forging†process. The first casting and forging process is very common: two sets of molds are required for blank production, one for manual metal mold casting and the other for precision forging using a friction press or hydraulic press. The die-casting forging process is a process that has only recently emerged internationally. Due to the limitation of patented technology, this process is still rare in China. Guangdong Zhaoqing Hongyin Electromechanical Technology Co., Ltd. was the first to introduce this technology to the outside world. Various blanks including sports car forging pistons, small cylinders, extreme sports motorcycle frames (6061 materials), and small wheels have been produced.
3. Introduction to Die Casting Forging Process
The die casting die forging process is a process performed on a dedicated die casting forging machine. The basic process is: the metal liquid is first filled into the cavity of the mold by low speed or high speed casting, and the mold has a movable cavity surface, which is pressed and forged with the cooling process of the molten metal, thereby eliminating the shrinkage of the blank. The loose defect also causes the internal structure of the blank to reach the forged broken grain. The overall mechanical properties of the blank are significantly improved. In addition, the blank produced by the process has an outer surface finish of 7 (Ra1.6), such as a cold extrusion process or a machined surface, with a metallic luster. Therefore, we call the die-casting forging process the “extreme forming processâ€, which is a step further than “no cutting, less residual forming processâ€. Another advantage of the die-casting forging process is that, in addition to producing conventional casting materials, it can also produce deformed alloys and forged alloys to produce highly complex parts. These alloy grades include: hard aluminum super-hard aluminum alloy, wrought aluminum alloy, such as LY11, LY12, 6061, 6063, LYC, LD, etc.). The tensile strength of these materials is nearly twice as high as that of ordinary cast alloys. It is more positive for aluminum alloy automobile wheels, frames and other parts that are expected to be produced with higher strength and impact resistant materials.
4. How to distinguish between the two blanks
From the appearance, it is difficult to distinguish the blanks produced by the two processes. If you see a machined part, it is even harder to distinguish. Therefore, we can only analyze and judge in reverse: First, die-casting parts are generally “structural partsâ€, while die-casting die-forgings are “functional partsâ€. "Structural parts" are opposite to "functional parts". The latter generally refers to the impact, high temperature, pressure, strength (force), as well as surface treatment (such as anodizing), heat treatment (solid solution strengthening). Typical products are engine blocks, hubs, pistons, connecting rods, brake shoes, pneumatic or hydraulic valve bodies (such as the common three-position five-way valve). The former is like a door frame, an instrument panel, an engine cover, and the like. The second is to judge from the material composition. Because die castings are generally cast alloys, for other grades of alloys, they are often produced by die casting die forging. The third is to judge the processing requirements of the blank on its outer surface. For example, aluminum die-casting parts, because of the silicon containing, and the blank produced by the die-casting process, the outer surface has microscopic pores (commonly known as "water grain"), and the surface of the material will have "black spots" after anodizing. Therefore, if the blank is anodized, the blank will not be produced by a common die casting process. The fourth is to judge from the metallographic organization. Die-casting parts and die-casting die forgings are easily distinguished on the metallographic side. The former is a dendritic as-cast structure, and the latter is a forged structure of uniform fractured grains.
5. Eliminate some wrong opinions
First, we can not think of the vacuum infiltration after die casting to solve the shrinkage and shrinkage defects in the die casting. It can not be considered that the vacuum die casting process can be used to produce functional parts that can be produced by continuous casting and forging. When the technology in the line has progressed, we must have a scientific attitude of advancing with the times in terms of ideas and ideas. Second, vacuum die castings have the same shrinkage and shrinkage defects as ordinary die castings; vacuum die casting, which is only a little more effective than ordinary die casting in assisting exhaust gas, and shrinkage holes caused by metal liquid phase shrinkage Shrinking (the inside is vacuum, no gas), it is no way. Third, the most common mistake made by professionals is that although it is known that this blank cannot be produced by ordinary die-casting process, a process called “reverse punch indirect and partial extrusion†is selected. They thought that this process had the same effect as the liquid die forging process, which is completely wrong. The essence of the "reverse punch extrusion" process is still a die casting process! Only the kind of "forward punch full projection area forging" is the real liquid die forging process.
6. Conclusion
It is very meaningful to distinguish between ordinary die-casting parts and die-casting die forgings. Although the methods to be mastered are not difficult, many are concepts and cognitive skills.
1. It is proposed to distinguish between open-cast castings and die-casting forging (liquid die forging), which is meaningful for two types of manufacturers.