The modern method of making primary steel from liquid iron and scrap uses the basic oxygen steel-making process. This process, also known as the BOS process, is widely used in the steel industry due to its efficiency and effectiveness in producing high-quality steel.

The basic oxygen steel-making process involves several steps and utilizes a furnace called the basic oxygen furnace (BOF). Here is a detailed explanation of each step:

1. Charging: The process begins by charging the basic oxygen furnace with a mixture of liquid iron and scrap. The liquid iron is typically produced in a blast furnace, while the scrap consists of recycled steel.

2. Preheating: The mixture of liquid iron and scrap is preheated before entering the basic oxygen furnace. This preheating helps to reduce energy consumption during the subsequent steps.

3. Oxygen blowing: Once the mixture is preheated, it is then introduced into the basic oxygen furnace. High-purity oxygen is blown into the furnace at supersonic speeds through a lance. The oxygen reacts with impurities in the liquid iron, such as carbon, silicon, and manganese, to form oxides. These oxides are then removed as slag.

4. Refining: As the oxygen reacts with the impurities, the temperature in the furnace rises, and the metal becomes more liquid. The refining process continues until the desired composition and temperature are achieved.

5. Alloying: After the impurities are removed, alloying elements are added to the molten metal to achieve the desired properties of the steel. These alloying elements can include manganese, chromium, nickel, and others, depending on the desired steel grade.

6. Deoxidation: To prevent oxidation during casting, a deoxidizing agent, such as aluminum or silicon, is added to the molten steel. This helps to remove any remaining oxygen and ensures the steel retains its desired properties.

7. Casting: Once the desired composition is attained, the molten steel is cast into various forms, such as blooms, billets, or slabs, depending on the final product requirements.

The basic oxygen steel-making process offers several advantages over other methods. It is cost-effective, energy-efficient, and capable of producing large quantities of high-quality steel. Additionally, it allows for flexibility in adjusting the composition and properties of the steel, making it suitable for a wide range of applications.

Overall, the basic oxygen steel-making process has revolutionized the steel industry and is now the primary method of producing steel from liquid iron and scrap.