Introduction to Steel Making and Wrought Iron

Study Notes

Introduction to Steel Making

Wrought iron is the purest commercially produced form of iron, notable for its malleability.
Pure iron melts at 1536°C, while pig iron is tapped from the blast furnace (B/F) at temperatures around 1250–1350°C due to impurities lowering melting points.
Prior to the 1850s, the maximum furnace temperature reached 1450°C, allowing for pig iron to be re-melted easily.
As refining reduces impurities, iron becomes more viscous, complicating the separation from slag.
The majority of slag is mechanically worked out, yielding a nearly impurity-free ferrous material known as wrought iron.
The puddling process, using a reverberatory furnace, is employed to make wrought iron. The furnace's dome-shaped roof supplies heat, and the hearth is lined with iron oxide and alumina-rich fireclay.

Wrought Iron Making Process

Production involves oxidation of impurities in pig iron, initiating with iron oxide during melting.
The refining process has three stages, primarily focusing on the oxidation of silicon, manganese, and phosphorus.
The temperature of the bath increases as impurities are removed, leading to a pasty mass that requires stirring.
Chemical reactions during refining include:
- Si + 2 Fe3O4 → SiO2 + 6 FeO
- Mn + Fe3O4 → MnO + 3 FeO
- 2 C + O2 → 2CO

Properties and Uses of Wrought Iron

Exhibits ductility, low strength, corrosion resistance, and can easily be forged and welded.
Composed of approximately 99% iron, making it the softest, toughest, and most ductile iron variant.
Common applications include crane hooks, chains, railway couplings, pipe fittings, and various metal sheets and bars.

Principles of Steel Making

Steel is produced through the purification of pig iron, which contains 92-95% iron and 5-8% impurities.
Steel making is focused on the selective oxidation of impurities, transforming them into oxides, while iron making emphasizes reduction smelting of iron ore.
The final steel composition generally consists of 97-98% iron and 2-3% impurities.

Historical Steel Making Processes

Key processes include:
- Wrought iron making
- Cementation steel making
- Crucible steel making

Raw Materials for Steel Making

Essential raw materials include:
- Source of metallic iron
- Oxidizing agents
- Fluxes
- Source of heat
- De-oxidizers
- Alloying agents
- Furnace refractories

Bessemer Process

The Bessemer process involves blowing air through molten pig iron, oxidizing elements like carbon, silicon, and manganese to form slag.
The Acid Bessemer process relies on the oxidation of silicon to generate heat, while the Basic process burns phosphorus for heat.
The choice of process depends on the pig iron's composition:
- Acid process is preferred for high silicon content.
- Basic process is utilized for high phosphorus content.

Acid Bessemer Process

Steel making is classified into acid and basic processes based on the slag's nature.
The Acid Bessemer process generates acidic slag and begins with supplying hot metal into the converter.

Description

Explore the fascinating processes involved in the making of steel and wrought iron. This quiz covers the characteristics of wrought iron, the important factors affecting melting points, and the techniques employed in their production. Test your knowledge on the history and methods of steel making!