With rapid development of modern industry, die casting technology has been widely used in various fields. As an efficient and precise production method, die casting production has become an indispensable link in manufacturing industry. However, in die casting production process, external factors will have different degrees of influence on quality of die castings, which is a problem that relevant personnel cannot ignore. So-called external factors refer to those uncontrolled factors, which may come from environment, raw materials, equipment, operators, etc., and these factors may have a certain impact on quality of die castings. Based on this, this paper will focus on influence of external factors on quality of die castings and propose corresponding countermeasures. Only through continuous practical research can we better solve influence of external factors on quality of die castings and promote further development of die casting technology.

Die casting production is a common metal processing method, and its production process is affected by many external factors. Following are 3 common external factors in die casting production. First, temperature. In die casting process, metal liquid needs to be within a certain temperature range to maintain fluidity and plasticity. If temperature is too high or too low, metal liquid will not be able to fully fill mold, or cause incomplete solidification. Therefore, in die casting production, it is necessary to ensure that temperature of metal liquid is controlled within an appropriate range to ensure quality and shape of product; second, humidity. Changes in humidity will cause changes in adhesion of mold surface, which in turn affects fluidity and filling of metal liquid. In a high humidity environment, moisture may accumulate on mold surface, resulting in inability of metal liquid to fill evenly, forming pores or defects. Therefore, in die casting production, it is necessary to pay close attention to changes in ambient humidity and take corresponding measures to adjust mold temperature and humidity to ensure product quality; finally, gas environment in die casting production is also an important external factor. During die casting process, gas in mold needs to be effectively discharged to avoid generation of bubbles or pores. At the same time, some harmful gases, such as metal vapor or exhaust gas, may be generated during die casting process. These harmful gases pose a potential threat to workers' health and environment. Therefore, in die-casting production, corresponding ventilation and exhaust systems need to be adopted to purify gas environment and ensure safety of workplace.

In die-casting production, external factors have an important influence on quality of die-castings, among which temperature and humidity are two key external factors. High temperature will increase fluidity of molten metal, which may cause various problems. Molten metal is easy to absorb gas in air at high temperature. When temperature is too high, gas in molten metal cannot escape completely, forming pores. These pores will seriously affect density and strength of die-castings, reduce their quality. At the same time, fluidity of molten metal increases at high temperature, which is prone to incomplete solidification of liquid metal during filling process, resulting in shrinkage inside die-casting, which will also affect its quality. Excessive humidity will also have an adverse effect on quality of die-castings. Excessive humidity will cause pores on contact surface between molten metal and mold. In a high humidity environment, moisture on contact surface between molten metal and mold will evaporate and form gas. These gases cannot escape completely, and will form pores during die-casting process. Pores will reduce density and strength of die-casting and have a negative impact on its quality.
In addition, excessive humidity can easily lead to defects on the surface of die-castings. During cooling process of molten metal in a high humidity environment, moisture will occur simultaneously with metal solidification, forming surface defects, which not only affects appearance of die-casting, but may also have a negative impact on its function.
Management and operation are also key factors. Poor management and operation will lead to a decline in quality of die-castings. Therefore, in production process, it is necessary to strictly follow the operating procedures to ensure quality control of each process. At the same time, it is also necessary to strengthen training and skills improvement of employees to improve their understanding and operation level of die-casting process. Through study of these external factors, corresponding response ideas can be formulated to improve quality of die-castings.

In die-casting process, mold is a tool that withstands high temperature and high pressure. If mold structure design is unreasonable, it is easy to cause metal liquid to fail to flow fully during filling process, thereby forming inclusions or defects inside die-casting. For example, if flow channel of mold is improperly designed, molten metal will not flow smoothly, resulting in inclusions; when cooling system of mold is not designed reasonably, it will cause uneven solidification of metal, resulting in defects. Therefore, when designing mold, fluidity and solidification of molten metal should be taken into account, and mold structure should be reasonably designed to avoid inclusions inside. Improper selection of mold materials will affect surface finish and precision of die casting.
In die casting production, mold is a tool that directly contacts molten metal. If hardness of selected mold material is not enough, it is easy to cause wear on mold surface, which in turn affects surface finish of die casting. At the same time, if thermal conductivity of mold material is not good, it will cause uneven solidification of molten metal, thereby affecting dimensional accuracy of die casting. Therefore, when manufacturing mold, it is necessary to select a suitable mold material to ensure that it has sufficient hardness, wear resistance and thermal conductivity to ensure surface finish of die casting (see Figure 1).

 

Figure 1 Die casting machine water system filter device setting diagram

In die-casting production process, external factors have an important impact on quality of die-castings. Quality of raw materials is the most critical factor. Unstable alloy composition and excessive impurity content will directly affect strength of die-castings.
Alloys are mixtures of various metal elements. Stability of their composition directly determines mechanical properties of die-castings. If alloy composition is unstable, that is, content of various metal elements cannot be maintained within design requirements, then strength and durability of die-castings cannot be guaranteed. For example, a certain alloy raw material should contain a certain proportion of copper and zinc elements to meet specific strength requirements, but if content of these two elements cannot be stably controlled, it will affect strength of die-casting and may even fail to meet design requirements. In production process of raw materials, it is inevitable that there will be various impurities, such as oxides, sulfides and metal debris. If content of these impurities is too high, they will cause problems in die-casting process. On the one hand, high content of oxides and sulfides will reduce fluidity of alloy, resulting in pores in die castings, which will reduce strength and sealing performance of die castings; on the other hand, inclusions such as metal debris will make structure of die castings uneven, thereby reducing its overall performance.

In die casting production, impact of external factors on production environment cannot be ignored. In order to ensure stability of production process and product quality, corresponding measures need to be taken to deal with these external factors. Maintaining constant temperature and humidity is very important. In die casting production process, fluidity of molten metal is affected by temperature. If temperature fluctuates greatly, it will directly affect fluidity of molten metal, thereby affecting molding quality of product.
Therefore, a constant temperature should be maintained in die casting workshop, and drastic temperature fluctuations should be avoided by installing an air conditioning system or strengthening insulation measures. Humidity is also a key factor that needs to be controlled. High humidity will cause water film on the surface of mold and die castings, affecting surface quality of product. In order to reduce negative impact of humidity on the surface of mold and die castings, ventilation equipment needs to be strengthened. Exhaust fans or ventilation ducts can be installed to remove moisture from workshop in time and maintain air circulation. At the same time, it is also possible to consider adding dehumidification equipment in workshop to reduce humidity to an appropriate range.

In die-casting production process, impact of external factors on product quality cannot be ignored. In order to effectively deal with these factors, optimizing mold design and manufacturing is an important idea. Mold design is directly related to product quality and production efficiency. Staff should use advanced mold design software to accurately analyze stress distribution and deformation of mold, so as to optimize mold structure to make it more reasonable and balanced, avoid product defects and mold damage caused by unreasonable mold structure.
At the same time, it is necessary to increase importance of mold material selection, choose high-quality steel as much as possible, effectively improve hardness and wear resistance of mold, extend service life of mold, better maintain dimensional stability of product and enhance surface quality of product.
In addition to the above two aspects, there are other coping ideas worth considering, such as combining die-casting process requirements to optimize cooling system of mold to improve cooling speed and uniformity of product, reduce product defects. And by reasonably setting water spray holes and air escape holes of mold, thermal fatigue and porosity problems can be effectively avoided (see Figure 2).

 

1. Injection punch 2. Pressure chamber 3. Liquid metal 4. Fixed mold 5. Moving mold 6. Mold cavity 7. Runner 8. Residual material
Figure 2 Schematic diagram of mold closing and die casting mold opening

First, regularly test, evaluate alloy composition and impurity content provided by supplier. Alloy composition plays a decisive role in performance and quality of die-casting products, and presence of impurities may cause reduced product strength or other quality problems. Therefore, establish a stable cooperative relationship with suppliers and regularly test raw materials they provide to ensure stability of raw material quality; secondly, introduce advanced material analysis technology. By using advanced material analysis technology, such as spectral analysis, electron microscopy, etc., comprehensively analyze composition and structure of raw materials, ensure stability of raw materials, and avoid potential quality problems; thirdly, establish a complete supply chain management system. By working closely with suppliers, establishing a long-term and stable cooperative relationship, quality of raw materials can be better controlled.

 

At the same time, by jointly formulating strict cooperation standards and quality control requirements with suppliers, a stable supply of raw materials can be ensured. Finally, strengthen internal quality management. In die-casting production process, it is necessary to strengthen control of raw material quality to ensure inspection pass rate and use accuracy of raw materials (see Figure 3). At the same time, a sound quality management system should be established to conduct comprehensive quality monitoring, timely discover and correct quality problems, so as to ensure quality stability of products.

In die-casting production, external factors have an important impact on quality of die-castings. Through study of these external factors, corresponding response ideas can be formulated to improve quality of die-castings. Therefore, in die-casting production, attention should be paid to control of factors such as temperature, pressure, mold quality, management and operation to ensure that quality of die-castings meets requirements.