Die-casting machines, die-casting alloys, and die-casting molds are the three essential elements of die-casting production, and none of them are indispensable. The so-called die-casting process is the organic and comprehensive application of these three elements, enabling the stable, rhythmic and efficient production of qualified castings with good appearance, internal quality, dimensions that meet the requirements of the drawings or agreements, and even high-quality castings.

Die-casting molds are one of the three major elements of die-casting production. A correctly and reasonably structured die-casting mold is a prerequisite for the smooth progress of die-casting production, and plays an important role in ensuring the quality of castings (pass rate during production).

Due to the characteristics of die-casting technology, the correct selection of various process parameters is the determining factor for obtaining high-quality castings, and die-casting molds are the prerequisite for correctly selecting and adjusting various process parameters. Die-casting mold design is essentially a comprehensive reflection of various factors that may occur in die-casting production.

If the design of the die-casting mold is reasonable, there will be fewer problems encountered in actual production, and the qualification rate of the casting will be high. On the contrary, the design of die-casting molds is unreasonable. For example, when designing a casting, the wrapping force of the dynamic and fixed molds is basically the same, while the pouring system is mostly produced on the fixed mold and placed on the Guannan die-casting machine where the punch cannot feed after injection, which cannot be produced normally. The casting remains stuck to the fixed mold. Although the smoothness of the fixed mold cavity is very smooth, there is still a phenomenon of sticking to the fixed mold due to the depth of the cavity. Therefore, in the design of die-casting molds, it is necessary to comprehensively analyze the structure of the castings, familiarize oneself with the operation process of the die-casting machine, consider the possibility of adjusting the decompression casting machine and process parameters, master the filling characteristics in different situations, and consider the mold processing methods, drilling holes, and fixed forms before designing a die-casting mold that is practical and meets production requirements.

The filling time of metal liquid is extremely short, and the specific pressure and flow rate of metal liquid are very high, which is extremely harsh for the working conditions of die-casting molds. In addition, the impact of alternating stress caused by quenching and heating has a significant impact on the service life of die-casting molds.

The service life of die-casting molds usually refers to the number of molds (including the number of scrap products in die-casting production) that have been carefully designed and manufactured under normal use conditions, combined with good maintenance and natural damage, before being scrapped due to irreparable damage.

In actual production, there are three main forms of die casting mold failure: ① thermal fatigue cracking damage failure; ② Fragmentation failure; ③ Corrosion failure.

There are many factors that can cause mold failure, including external factors (such as high or low casting temperature, whether the mold is preheated, the amount of water spray coating, whether the tonnage of the die-casting machine matches, high die-casting pressure, too fast inner gate speed, cooling water not being opened synchronously with die-casting production, the type and composition of the casting material Fe, the size and shape of the casting, wall thickness, coating type, etc.). There are also internal factors (such as the metallurgical quality of the mold material, the forging process of the billet, the rationality of the mold structure design, the rationality of the pouring system design, the internal stress generated during the mold machine (electrical processing) processing, the heat treatment process of the mold, including various matching accuracy and smoothness requirements, etc.).

If early failure occurs in die-casting molds, it is necessary to identify the internal or external causes for future improvement.

1. Thermal fatigue cracking failure

During die-casting production, the die-casting mold is repeatedly subjected to the action of cold and heat stimulation, causing deformation on the formed surface and its interior, which leads to repeated cyclic thermal stress. This leads to damage to the organizational structure and loss of toughness, leading to the occurrence and continued propagation of microcracks. Once the crack expands, molten metal is squeezed in, and repeated mechanical stress accelerates the crack propagation.

Therefore, on the one hand, the die-casting mold must be fully preheated at the beginning of die-casting. In addition, during the die-casting production process, the mold must be maintained within a certain operating temperature range to avoid early stages

Compiled from an academic library for reference in learning.

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