Pack Carburizing:

What is Pack carburizing?

Pack carburizing is a case hardening process where low-carbon steel or iron components are heated in the presence of a solid carbon-rich material (like charcoal or carbon powder) to increase surface hardness.

🔹 Why is it needed?

• Low-carbon steels lack hardness and wear resistance.

• Pack carburizing forms a hard, wear-resistant outer layer while keeping the core tough.

• It enhances the fatigue strength and lifespan of machine parts.

How Does Pack Carburizing Work?

1. Preparation

• The steel components are placed in a sealed container.

• They are packed with solid carbonaceous material (charcoal, coke, or carbon powder).

• An activator (like barium carbonate) is added to speed up carbon diffusion.

2. Heating

• The container is heated in a furnace (900–950°C or 1650–1750°F).

• At high temperatures, carbon from the solid material breaks down into carbon monoxide (CO).

• The CO gas reacts with the steel surface, diffusing carbon atoms into the outer layer.

3. Soaking

• The component remains in the furnace for several hours (5–10 hours), depending on the desired case depth.

• The longer the soaking time, the deeper the carbon diffusion (case depth: 0.5–2mm).

4. Cooling & Quenching

• The part is cooled slowly or quenched in water or oil.

• Quenching locks in the hard martensite structure, increasing hardness.

Key Features of Pack Carburizing

✔ Hard case (0.5–2mm thick)
✔ Tough, ductile core
✔ Uses inexpensive carbon sources
✔ Simple & cost-effective for batch processing

Advantages of Pack Carburizing

✅ Cost-effective – Uses solid carbon, no expensive gases required.
✅ Simple setup – No need for complex gas or liquid handling.
✅ Can be used for large batches – Effective for mass production.
✅ Good wear resistance – Improves component lifespan.
✅ Low distortion risk – Controlled heating minimizes warping.

Disadvantages of Pack Carburizing

❌ Slow process – Takes longer than gas or liquid carburizing.
❌ Non-uniform carbon absorption – Case depth may vary.
❌ Limited control over carbon concentration – Difficult to fine-tune properties.
❌ Messy process – Leaves behind residual carbon waste.

Applications of Pack Carburizing

🔹 Automotive Industry – Gears, shafts, camshafts, crankshafts.
🔹 Aerospace Industry – Engine parts, landing gear components.
🔹 Machinery & Tools – Bearings, cutting tools, industrial rollers.
🔹 Defense & Firearms – Gun components, armor plates.