امتصاص الغاز في صهر النحاس النقي, تقنيات عملية لتغطية الفحم وإزالة أكسدة الفوسفور والنحاس

التركيز على المحتوى: Specifically for pure copper (red copper) صهر. This guide discusses the susceptibility of molten copper to hydrogen and oxygen absorption in induction furnace environments and shares practical recipes for air isolation and deoxidation.

Core Pain Point Analysis: Why is Pure Copper Smelting in Induction Furnaces Prone to Gas Absorption?

Pure copper is extremely sensitive to gases (Hydrogen and Oxygen) when in a liquid state:

• Hydrogen Absorption: Hydrogen is the main culprit for porosity (gas holes). While the electromagnetic stirring effect of an induction furnace ensures uniform temperature, it also constantly rolls the surface melt into the interior. If the coverage is poor, this effectively “stirs” رُطُوبَة (the source of hydrogen) from the air directly into the copper liquid.
• Oxygen Absorption: Oxygen reacts with copper to form Cuprous Oxide. Although this does not directly cause porosity, it reacts with hydrogen to form water vapor. This is the fundamental reaction that leads to “hydrogen embrittlement” and poor density in castings.

أنا. Charcoal Coverage Process: Building Physical and Chemical Barriers

في فرن الحث, charcoal acts not only as a physical cover but also as a reducing agent. لكن, using the wrong charcoal (على سبيل المثال, damp or powdered) will introduce gas instead of preventing it.

1. Charcoal Selection and Treatment (Crucial!)

• Must be Calcined/Baked: Ordinary charcoal contains moisture and volatiles. Tip: You must use charcoal that has been calcined at high temperatures (red hot state) or baked for a long time (above 150°C for 2 ساعات). If not dried, charcoal itself becomes a massive source of hydrogen.
• Granularity Control:
  • Avoid Powder: Induction furnaces have strong electromagnetic stirring. Fine powdered charcoal is easily sucked into the copper liquid, causing slag inclusions.
  • Recommended Size: Use block charcoal the size of chestnuts (10مم – 30مم). This size packs tightly enough to isolate air but is large enough to rely on buoyancy to stay on the surface without being stirred under.

2. Operational Skills for Coverage

• توقيت: Do not wait until the copper is fully melted to add charcoal. The first batch of charcoal should be added as soon as the base charge melts and forms a molten pool.
• Coverage Thickness: غالباً, gas absorption occurs because the cover is “too thin.” A thickness of 30مم – 50مم يوصى به. Ensure the copper liquid surface is never exposed or glowing red; it should always present a black coverage layer.
• Slag Skimming: When skimming slag before tapping, operate quickly. Skim a portion and immediately pour or measure temperature to minimize exposure time.

الثاني. Phosphorus-Copper Deoxidation Process: Precise Formula and Timing

Phosphorus-Copper (usually using Cu-14%P أو Cu-15%P master alloy) is the most effective deoxidizer for pure copper. It reacts with Cu2O to form Phosphorus Pentoxide gas or slag, which is then expelled.

1. Practical Dosage Formula

For standard pure copper, the amount of deoxidizer cannot be guessed. Too little won’t clear the oxygen; too much will severely reduce electrical conductivity.

• Recommended Dosage:0.1% ~ 0.15% of the total copper weight.
• Calculation Formula:
• Phosphorus-Copper to add (g) = Total Copper Weight (كلغ) * 1.5
  • دراسة حالة: For smelting 100 كلغ of pure copper, it is recommended to add 150 g ل 15% Phosphorus-Copper.
  • ملحوظة: If the proportion of return scrap (waste material) is high and oxidation is severe, you may increase this to 0.2% (200g), but be aware that conductivity may drop.

2. Golden Timing for Addition

• Do Not Add Too Early: Phosphorus will burn off and volatilize at high temperatures.
• Best Moment: يضيف 1-2 minutes before tapping/pouring.
• Operational Technique:
  • Cut power or reduce wattage.
  • Push aside a local area of the charcoal layer.
  • Use a Bell Plunger (Bell Jar) to press the Phosphorus-Copper block deep into the furnace bottom (Do not throw it on the surface; otherwise, the phosphorus will float and burn off without deoxidizing).
  • Stir gently (using residual magnetism or manually) to ensure a uniform reaction.
  • Let stand for 1-2 minutes to allow oxide slag to float up, skim the slag, and pour immediately.

ثالثا. Process Flow Summary

For ease of workshop operation, you can refer to this simple workflow:

1. تحضير: Dry oil/contaminants from copper materials; preheat and bake block charcoal nearby.
2. Start Melting: Add a small amount of copper to the crucible bottom and add the first batch of dry charcoal along with the charge.
3. During Melting: As materials are added, constantly replenish charcoal to maintain a 30-50مم thickness. Strictly forbid exposed copper liquid.
4. After Full Melt: Raise to pouring temperature (على سبيل المثال, 1150-1200درجة مئوية) and skim off old charcoal slag that has adsorbed impurities.
5. إزالة الأكسدة (Critical Step):
   • Prepare Phosphorus-Copper at a ratio of 1.5g per kg.
   • Press it deep into the copper liquid using a tool.
   • Stir smoothly and evenly.
6. Settling & صب: Let stand for about 2 دقائق, sprinkle a layer of covering agent (such as perlite or fresh dry charcoal) for insulation, and pour quickly.