Disadvantages of using die-casting parts:
1. Equipment costs are expensive
The equipment required for die-casting production, such as die-casting machines, melting furnaces, holding furnaces, and die-casting molds, are quite expensive.
2. Poor airtightness of die-casting parts
Due to the phenomenon of turbulent flow when the molten liquid is filled into the die-casting mold, local air holes or shrinkage holes are formed, which affects the airtightness of the die-casting parts. There is currently a method of immersion treatment that can be used to ensure airtightness.
3. Die cast alloys are restricted
We still need to discuss the relevant materials, mold materials, and operation methods.
The general term for hole defects of different sizes and shapes generated on the surface and inside of die-casting parts. Including pores, shrinkage, porosity, etc.
1. Pore type defects formed by gas in die castings. Its surface is generally relatively smooth, mainly in pear shaped, circular, and elliptical shapes. Usually exposed on the surface of die castings, large pores often exist in isolation, while small pores appear in groups.
2. The dispersed pores distributed in groups on the surface of die castings. Its characteristics and formation reasons are the same as subcutaneous pores, usually exposed on the surface of die-casting parts, and can be removed after machining for 1-2 mm.
3. Porous casting defects formed by the combination of dispersed gas pores, shrinkage pores, and porosity.
4. Subcutaneous pores are dispersed pores located under the skin of die castings. Reactive pores generated by the reaction between metal liquid and sand mold. It is usually discovered after mechanical processing or heat treatment.
5. The large amount of gas generated during the choking pouring process cannot be smoothly discharged, causing boiling in the metal liquid, resulting in a large number of pores and even incomplete defects in the die casting.
6. Pinholes are generally precipitated pores with needle size distribution on the cross-section of die castings. It poses great harm to the performance of die castings.
In recent years, vacuum heat treatment technology, surface technology of aluminum sleeve molds, and pre hardening technology of mold materials have developed rapidly in mold heat treatment technology. Generally speaking, the surface of cast die castings is relatively rough, with more holes, and the surface of the die castings is not clean, covered with substances such as sand and white wax. But if it is not cleaned in advance, it is difficult to get silver plated. Therefore, it is necessary to clean the surface of the die casting first, and then apply a layer of silver on the surface of the die casting to make it more qualified.
Due to the unique structure of die castings, the requirements for their electroplating process are also very strict, in order to produce satisfactory products. However, it should be noted that in order to avoid affecting the casting process, residual solution in the gaps of the cast aluminum should be cleaned up. If there are residual substances inside, it will affect the next step of casting.
The actual surface area of die-casting parts is many times larger than the calculated surface area, and the impact current density during electroplating is about three times higher than that of ordinary parts. The pre plating time is also longer than that of ordinary parts; When pre plating aluminum, the parts and hanging tools should be shaken frequently to ensure uniform and consistent coating color, and to prevent the occurrence of spots during silver plating that may affect the appearance quality of the coating; The metal structure of die-casting parts is looser than that of rolled aluminum, with rough and porous surface. In addition, the surface of die-casting parts often contains a portion of molding sand, paraffin, and silicate substances. If not cleaned thoroughly, it often leads to local plating failure. Therefore, the key to solving the silver plating quality of die-casting parts is to clean the surface and add appropriate process steps.
Temperature control is the control of surface heat treatment, with careful size control. If the temperature is low during the processing of die castings, it is easy to cause surface material loss and the product cannot be removed. When the temperature is too high, the mold has many defects, such as cracks.
The working life of die-casting molds: The incorrect organizational structure and excessive grain size caused by heat treatment result in a decrease in the main performance of the mold, such as toughness, cold and hot fatigue performance, wear resistance, etc., which affects the working life of the mold.
Post time: Aug-14-2023