---
title: "Mechanical treatment of steel"
subject: "Civil Engineering Materials"
chapter: 8
key: "semester_3/civil_engineering_materials:mechanical-treatment-steel"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/mechanical-treatment-steel
site: BCT Engineering
---

# Mechanical treatment of steel

Civil Engineering Materials · Chapter 8: Metals and Alloys

- Asked in: 2057 Chaitra (old course), 2+4 marks; 2059 Poush (old course), 4 marks (asked 2 times)
- Video: [Steel – Mechanical treatment – Aluminum – Uses – Market forms](https://www.youtube.com/watch?v=UO5F2WhWPLQ) — RCET CIVIL
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/mechanical-treatment-steel
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-8

## Question

Why is mechanical treatment done in steel? Explain different methods of mechanical treatment.

## Short answer

Mechanical treatment shapes steel and improves properties by refining grain, removing defects, and increasing strength. Hot working (rolling, forging) is done above recrystallisation temperature; cold working (cold rolling, drawing) at room temperature induces strain hardening.

## Answer

#### Why mechanical treatment is done
**Mechanical treatment** (mechanical working) is the shaping of steel by applying force (hammering, rolling, drawing) to obtain the required shape and size, and to improve its properties.
- It gives the required shape and size (bars, sheets, sections, wires).
- It refines the grain and removes casting defects such as blow holes and porosity, increasing strength, toughness and density.
- It improves the surface finish and dimensional accuracy.
- Cold work raises yield strength and hardness (strain hardening).

#### Methods
**A. Hot working** (above the recrystallisation temperature, about 900-1200 C for steel):
1. **Rolling:** red-hot steel passes between rollers to make plates, sheets, bars and structural sections.
2. **Forging:** hammering or pressing hot steel into shape (bolts, hooks, crankshafts).
3. **Extrusion:** forcing hot metal through a die to give a long section.
4. **Pressing/piercing:** for pipes and hollow items.

**B. Cold working** (at room temperature or below recrystallisation temperature):
1. **Cold rolling:** for thin sheets with a smooth surface.
2. **Drawing:** a bar is pulled through a die to make wires and rods.
3. **Bending, twisting (cold twisted deformed bars) and stretching.**
4. **Spinning, shearing, stamping and pressing.**

| Hot working | Cold working |
|---|---|
| Above recrystallisation temperature | Below recrystallisation |
| Easy to shape; less force | More force; strain hardening |
| Rough finish, scale forms | Good finish and accuracy |
| Grains refined, ductile | Stronger, less ductile |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Mechanical working
   A. Only colours
   B. Only weakens
   C. Only cools
   D. Shapes steel and refines grain and removes casting defects
   Answer: D. Shape. (Key point: Why)

2. Hot working is done
   A. Above recrystallisation temperature
   B. Below
   C. Room temp
   D. Sub zero
   Answer: A. Hot. (Key point: Hot working)

3. Cold working causes
   A. Softening
   B. Strain hardening: higher strength and less ductility
   C. Scale
   D. Rough finish
   Answer: B. Strain hardening. (Key point: Cold working)

4. Drawing makes
   A. Plates
   B. Castings
   C. Wires and rods by pulling through a die
   D. Bricks
   Answer: C. Die. (Key point: Drawing)

## Related in Civil Engineering Materials

- [Mechanical vs heat treatment; red shortness](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Amechanical-vs-heat-treatment-red-shortness) — Civil Engineering Materials, chapter 8
- [Mechanical vs heat treatment, tempering](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Amech-heat-treatment-isothermal-tempering) — Civil Engineering Materials, chapter 8
- [Heat treatment and three methods](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aheat-treatment-three-methods) — Civil Engineering Materials, chapter 8

## Related in other subjects

- [Heat treatment processes of steel](https://www.bctengineer.com/question.md?key=semester_3%2Fmaterial_science%3Aheat-treatment-of-steels) — Material Science, chapter 6
- [Notes on powder metallurgy and heat treatment](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Apowder-metallurgy-heat-treatment-notes) — Machine Design II, chapter 3