2. Iron from the blast furnace contains elements such as carbon, phosphorus and sulphur that make it brittle. These are removed in the BOS process.

3. Scrap iron is added to the converter.

5. Molten iron from the blast furnace is carried in a ladle, where powdered magnesium is added. The magnesium reacts with sulphur impurities to form MgS slag, which is scraped off.

6. The molten iron is poured from the ladle into the converter.

8. Oxygen is blown in. It reacts with carbon forming carbon monoxide gas, which escapes. Phosphorus oxidises to form phosphorus(V) oxide.

9. Calcium oxide is added. It reacts with acidic impurities like phosphorus(V) oxide and forms a slag.

10. The converter is tipped and the molten steel is tapped off.

11. The converter is tipped the other way and the slag is removed.

13. The converter is ready for the next cycle of steelmaking.