Die castings that are processed from zinc alloy die casting are becoming increasingly prevalent in almost every aspect of modern life. Every day, the die-casting process is used to process a wide variety of zinc alloy die-casting parts. Casting technology has been proposed for use in a wide variety of applications, ranging from the production of small zinc furniture hardware, such as modern frying pans, pots, and casings of communication equipment, to the processing of structural parts for the automotive industry. the obstacle.
The weight of zinc alloy die-casting parts can range anywhere from a few grams to more than 50 kilograms, and there is a wide range of requirements for the die-casting molds as well as the thermal steel that is utilized. In recent years, there has been a significant increase in the amount of emphasis placed on quality, and the surface quality of the finest castings used in contemporary mobile phones requires an extremely high level of precision . Brightly painted surfaces are required for a significant amount of structural workpieces, such as those found on automobile doors. Because of this, there are stringent requirements placed on the surface roughness of zinc alloy die-casting parts as well as the thermal stability of thermal steel.
Die-casting molds need to have higher power than they ever have before in order to accommodate the low-cost production of zinc alloy die-casting parts. Only by doing things this way is it possible to produce such a large number of zinc alloy die-casting parts in such a short amount of time during operation. As a material for die-casting molds, there are currently three types of thermal steels that conform to international standards. These three types of material have been proven to be suitable for the production of economically aluminum alloy die casting and qualitatively superior standard zinc alloy die-casting parts. As the complexity of zinc alloy die-casting parts, as well as the size of zinc alloy die-casting parts, increases, there is a corresponding increase in the amount of labor required. There are already standard thermal steels, but they cannot satisfy the requirements for economically feasible processing in order to increase the size.
In response to rising standards for both the quality of zinc alloy die castings and the characteristics of the thermal steel that is employed, three new varieties of thermal steel with improved characteristics have been developed.
1. Thermal steel, which is used in die casting molds
The DINEN ISO4957 standard is the international grade standard that applies to thermal steel 1.2343, 1.2344, and 1.2367. The thermal strength and thermal toughness of 1.2343 steel are properly matched, and it is the thermal steel that is used for die-casting molds in Europe at a higher frequency than any other thermal steel. Steel with a higher vanadium content, such as 1.2344, has greater thermal strength die casting aluminum and tempering stability than steel with a lower vanadium content, such as 1.2343. On the other hand, its toughness is lower. Historically, this variety of steel was utilized most frequently in the United States of America. The 1.267 steel is superior to the other two steels in terms of both its thermal strength and its tempering stability. This is primarily attributable to the high molybdenum content of 3% that it contains. This benefit can be attributed to the obvious reduction in toughness.
The new special thermal steels TQ1 and HP1 are based on the most stringent purity criteria, which not only indicates a decrease in the content of phosphorus and sulfur, but also indicates a rapid and effective decrease in the content of harmful associated elements. These results indicate that the new steels are superior to their predecessors in terms of both phosphorus and sulfur content. These harmful elements are mainly accumulated during the process of recycling scrap iron, which has a negative effect on the steel's ability to withstand impact. It is also possible to detect a decrease in the content of carbon and silicon, both of which have been shown to have a positive influence on the toughness over this range of temperatures. TQ1 produces a very high combination of toughness, hot strength, temper stability, and thermal shock stability properties thanks to the combination of the molybdenum and vanadium content that was mentioned earlier.
In the same way, HP1 steel is constructed with the highest possible level of purity in mind. However, when compared to TQ1, it has significantly less molybdenum in its structure. Therefore, when manufacturing steel, one must take into consideration the rise in the amount of the alloying element molybdenum. Both the HP1 and the TQ1 can achieve the same level of thermal strength by adjusting the temperature of the recommended hardness and using niobium alloy. The third variety of special steel, referred to as HTR die casting aluminum, has a composition that has been specifically designed to significantly improve thermal strength, tempering stability, and thermal conductivity. Because of this, the amount of chromium that it contains has been drastically cut down, which, along with the decreased amount of carbon, contributes to the increased tenacity of the steel.
2. Specifications of the steel in question
The application of heat to the molds used in die-casting is not only an important working method, but it is also helpful for making the appropriate choice of thermal steel. A graph that looks like this one illustrates how the heating of the steel affects its hardness. The tempering curve of the steel being introduced lost foam casting can be found in Figure 1. The less common 1.2344 steel that is used less in Germany is not listed on this curve. All of the steel types listed, with the exception of HTR steel, exhibit obvious secondary hardness maximum values at tempering temperatures ranging from 500 to 550 degrees Fahrenheit. The hardness of the material decreases as the temperature at which it is tempered is allowed to continue to rise. The curve has a downward slope, which suggests that there is a tendency toward tempering stability. When the steepness of the tempering curve decreases, the tempering stability of the steel decreases as well, and the steel's response to heating during pouring operations becomes more sensitive.
This curve demonstrates that steel with a tempering stability of 1.2367 is superior to that of steel with a tempering stability of 1.2343. TQ1 and HP1 achieve nearly the same level of tempering stability as 1.2367 in the technical range for tempering temperatures that are higher than 550 degrees. Because it contains a significant amount of tungsten, the special steel known as HTR has tempering temperatures aluminum alloy die casting that are noticeably higher than those of other steels. The secondary hardness maximum not only shifts to a higher tempering temperature at about 70 degrees, but the curve also drops smaller at temperatures that are higher than this maximum. This occurs because the secondary hardness maximum moves to a higher tempering temperature.
You can achieve a consistent and fine structure by following the method described above. The basic idea is to make the most of the effects that rapid heating and cyclic processing have on the material. The material is heated up very quickly in order to produce a large number of austenite nuclei, and as a result, fine grains are produced lost foam casting and obtained. The quality of the refined product is directly proportional to both the rate at which the process is carried out and the magnitude of the temperature differential. The success of this process can also be improved by increasing the number of times it is performed. On the one hand, repeated heating and cooling can promote nucleation, and on the other, it can further refine the crystals that have already been nucleated. The grains of austenite are refined once during each iteration of the process, which results in an increase in the nucleation rate during the subsequent austenitization.
Before repeating this process, the sample's hardness and impact values will continue to rise, and the outcomes of each cycle will be unique. After three to five cycles of heat treatment, the material's hardness value as well as its impact value will both experience significant improvements. The sample's hardness value and impact value will not significantly change after the application of the same process that was used previously. It will take about six times before it gets close to the maximum possible level of refinement. If the cycle is repeated at this point in the process, there will not be much of an improvement in the effectiveness of the heat treatment as a result. As a result, the optimum number of cycles is between four and five. Die-casting molds can be given a cyclic ultrafine heat treatment, which is one of the effective ways to improve the precision of the molds. In spite of the fact that the process is rather involved, the effects can be easily seen in the end product.
