How to make mirror surface platinum bar ？

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I. Materials and tool preparation
Platinum raw materials:
Platinum particles, platinum bars or recycled platinum (purity must meet the target requirements, such as Pt950, Pt900).
Gold melting equipment:
Gold melting machine: must be able to generate high temperatures above 1768°C (usually using high-frequency induction melting furnace or arc melting furnace).
Graphite crucible: high temperature resistant container (platinum is easy to react with metal crucibles, graphite or ceramic materials must be used).
Mold material:
Graphite mold: high temperature resistant and easy to engrave logo grooves (need to be customized).
Refractory gypsum mold: suitable for fine casting (need to be dried and demolded in advance).
Imprinting tool:
Steel stamp mold: customized hardened steel stamp with logo (need to withstand high temperature).
Laser engraving machine: used for later engraving (requires professional equipment).
Auxiliary tools:
High temperature pliers, casting spoon, protective gloves, goggles, fire blanket, inert gas (such as argon to prevent oxidation).
II. Production process
1. Design and mold making
Logo design:
Use CAD or 3D modeling software to design the logo, ensuring that the pattern is clear and suitable for casting/imprinting.
If the mold casting method is used, the logo groove (reverse mold) needs to be engraved in the mold.
Mold processing:
Engrave the designed logo into the graphite mold (requires CNC engraving machine or manual engraving).
If a refractory gypsum mold is used, it needs to be reproduced through 3D printing master mold.
2. Melting platinum
Preheating equipment:
Preheat the melting machine and graphite crucible to above 1000°C to avoid cracking of platinum due to sudden cooling.
Melting process:
Put the platinum raw material into the graphite crucible, start the melting machine and heat it to above 1768°C (it is recommended to operate under inert gas protection).
After the platinum is completely melted, use a high-temperature spoon to skim off the surface impurities.
3. Pouring platinum blocks
Fix the mold:
Fix the preheated mold (graphite or gypsum) in a safe position to ensure that the pouring port is unobstructed.
Pouring molten metal:
Pour the molten platinum into the mold quickly to avoid cooling and solidification (the operation must be completed within 10 seconds).
Cooling demoulding:
Naturally cool to room temperature (platinum cools slowly, so you need to wait patiently).
Tap the mold to remove the platinum block and use an ultrasonic cleaner to remove surface residues.
4. Logo embossing
Option 1: Direct molding during casting
If the logo groove has been engraved in the mold, the logo will automatically bulge on the surface of the platinum block after pouring.
Advantages: One-time molding, no post-processing required.
Disadvantages: High mold production cost and precise alignment required.
Option 2: Post-embossing
Preheat the platinum block: Use a spray gun to locally heat to 600-800°C (reduce hardness for easy embossing).
Stamping operation:
Align the custom steel stamp to the position and apply pressure with a hydraulic press or hammer (control the force to avoid deformation).
Annealing treatment: Reheat the platinum block after stamping and cool it slowly to eliminate internal stress.
5. Surface treatment
Polishing: Polish gradually with emery paper (400-3000 mesh), and finally polish with an agate knife or cloth wheel.
Electroplating: Rhodium plating is optional to enhance gloss and wear resistance (professional electroplating equipment is required).
III. Key points
Safety protection:
Wear fireproof clothing, goggles, and high-temperature resistant gloves throughout the process, and the smelting area is equipped with fire extinguishing equipment.
High-temperature platinum melt will explode when it comes into contact with water, so ensure that the environment is absolutely dry.
Anti-oxidation measures:
Introduce argon or nitrogen during smelting and pouring to prevent oxidation and graying of the platinum surface.
Precision control:
The casting mold needs to be precisely processed, otherwise the edge of the logo may be blurred.
The platinum block needs to be fixed during stamping to prevent displacement and ghosting.
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