News

In the field of gold and silver processing, traditionally, polishing is often relied upon to make the surface of gold and silver emit a charming luster. However, with the help of a vacuum ingot casting machine, we can explore some unique methods that can achieve this effect without polishing. This not only simplifies the process flow, but also reduces costs to a certain extent, while achieving satisfactory surface effects.

1.Principle exploration

In a vacuum environment, the solidification process of metals undergoes significant changes. The vacuum ingot casting machine can greatly reduce the influence of impurities and gases in the air on the gold and silver melt. When gold and silver solidify in a nearly impurity free environment, their crystallization process becomes more uniform and dense. This uniform and dense crystalline structure lays the foundation for the natural luster of gold and silver surfaces. Compared with solidification in a normal environment, vacuum environment reduces surface defects caused by gas inclusions and impurity adhesion, making the micro level of gold and silver surface smoother and smoother. Light can reflect and refract well on its surface, thus exhibiting a charming luster.

2.Operation steps

（1） Preparation work

Raw material selection: Ensure the use of high-purity gold and silver raw materials. Excessive impurity content can seriously affect the final surface gloss effect. For example, gold and silver raw materials with a purity of 99.99% or higher can minimize surface defects caused by impurities.

Equipment inspection: Conduct a comprehensive inspection of the vacuum ingot casting machine, including whether the vacuum system can achieve the specified vacuum degree, whether the heating device is operating normally, and whether the ingot mold is intact and clean. If there is a leak in the vacuum system, it will cause air to enter and affect the metal solidification environment; Abnormal heating device may cause uneven melting of gold and silver; If there is dirt or damage on the ingot mold, it will cause unevenness on the surface of the ingot.

（2） Melting gold and silver

Loading: Carefully place the selected gold and silver raw materials into the crucible of the vacuum casting machine. During the loading process, it is necessary to avoid collisions between the raw materials and the crucible wall, which can produce debris. At the same time, it is important to ensure that the raw materials are placed in the center of the crucible to ensure even heating.

Vacuum pumping: Close the furnace door of the ingot casting machine and start the vacuum system. Slowly extract the air inside the ingot casting machine and control the vacuum degree within the range of 10 ⁻³ -10 ⁻⁵ Pa according to the equipment performance. This vacuum degree can effectively reduce the pollution of oxygen, nitrogen and other gases in the air to the gold and silver melt.

Heating and melting: Turn on the heating device and heat at an appropriate heating rate according to the melting point characteristics of gold and silver. For example, the melting point of gold is about 1064 ℃, and the melting point of silver is about 961 ℃. When approaching the melting point, the heating rate should be appropriately reduced to ensure uniform melting of gold and silver and avoid local overheating. After gold and silver are completely melted into a liquid state, maintain a constant temperature for a period of time to make the composition of the melt more uniform.

（3） Ingot molding

1. Mold preparation: Preheat the ingot mold while the gold and silver melt. The preheating temperature is generally controlled between 100-200 ℃, and the specific temperature can be adjusted according to the requirements of the mold material and the gold and silver ingot. The purpose of preheating is to make the mold temperature uniform and avoid stress concentration caused by excessive temperature difference when pouring gold and silver melt into the mold, which affects the quality of the ingot.

2. Casting: When the gold and silver melt reaches the appropriate casting temperature, it is slowly and evenly poured into the preheated ingot mold through the casting device of the vacuum ingot casting machine. During the casting process, a stable flow rate should be maintained to avoid turbulence and prevent air from being drawn into the melt.

3.Solidification control: When the gold and silver melt in the ingot mold begins to solidify, the solidification speed can be controlled by adjusting the cooling system of the ingot casting machine. Generally speaking, a slow and uniform solidification rate helps to form a denser crystal structure. For example, a combination of natural cooling and moderate air cooling can be used to gradually and uniformly solidify the ingot from the surface to the interior.

3.Precautions

1. Strictly control environmental parameters: Throughout the entire process, it is necessary to strictly monitor parameters such as vacuum degree, temperature, and time. Any deviation in a parameter may have an adverse effect on the final surface gloss effect. For example, insufficient vacuum may cause gas to mix in, resulting in porosity on the surface of the ingot; Improper temperature control may lead to coarse or uneven crystal structure.

2. Skill requirements for operators: Operators need to have rich experience in operating vacuum ingot casting machines and a deep understanding of gold and silver processing technology. In the process of operation, it is necessary to be able to accurately judge various situations and take timely and correct response measures.

3. Regular maintenance of equipment: In order to ensure that the vacuum ingot casting machine is always in good operating condition, it is necessary to regularly maintain the equipment. Including cleaning the vacuum system, inspecting heating elements, calibrating temperature sensors, etc., to ensure that all performance indicators of the equipment meet the requirements.

Through the series of operations on the vacuum casting machine mentioned above, the surface of gold and silver can emit a charming luster without going through traditional polishing processes. This method provides a new approach and process selection for the gold and silver processing industry, which helps to improve production efficiency and product quality.