---
title: "Mechanical vs heat treatment; red shortness"
subject: "Civil Engineering Materials"
chapter: 8
key: "semester_3/civil_engineering_materials:mechanical-vs-heat-treatment-red-shortness"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/mechanical-vs-heat-treatment-red-shortness
site: BCT Engineering
---

# Mechanical vs heat treatment; red shortness

Civil Engineering Materials · Chapter 8: Metals and Alloys

- Asked in: 2078 Bhadra, 3+2 marks
- 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-vs-heat-treatment-red-shortness
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-8

## Question

Differentiate between mechanical and heat treatment of steel. How will you define annealing and red shortness of steel?

## Short answer

Mechanical treatment shapes by force and refines grain (e.g., rolling). Heat treatment alters internal structure without changing shape (e.g., annealing, slow cooling to soften). Red shortness is hot brittleness from sulphur forming low-melting iron sulphide at grain boundaries.

## Answer

#### Mechanical vs heat treatment
| Point | Mechanical treatment | Heat treatment |
|---|---|---|
| Principle | Shaping by force: rolling, forging, drawing, pressing | Heating, soaking and cooling in a controlled way |
| Change | Shape/size and grain refinement | Internal structure (phases) with the shape unchanged |
| Aim | To get shape, remove defects, strengthen by work-hardening | To change hardness, strength, ductility, toughness |
| Temperature | Hot or cold | Specific temperatures (150-950 C) |
| Examples | Hot rolling, cold drawing, forging | Annealing, normalizing, quenching, tempering |

#### Annealing
Annealing is heating steel above the upper critical temperature, soaking, and cooling very slowly in the furnace to soften it, remove internal stresses and refine the grain.

#### Red shortness
**Red shortness** is the brittleness of steel at red-hot temperature (during hot working such as forging and rolling), causing cracks. It is caused by the presence of **sulphur** (forming low melting iron sulphide at the grain boundaries). It is reduced by adding manganese, which forms manganese sulphide, and by keeping sulphur low.

## Check yourself

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

1. Heat treatment changes
   A. Shape by force
   B. Colour
   C. Internal structure without changing shape
   D. Size
   Answer: C. Structure. (Key point: Difference)

2. Red shortness is caused by
   A. Phosphorus
   B. Carbon
   C. Manganese
   D. Sulphur
   Answer: D. FeS. (Key point: Red shortness)

3. It is reduced by
   A. Adding manganese
   B. Adding sulphur
   C. Quenching
   D. Cooling
   Answer: A. MnS. (Key point: Remedy)

4. Annealing cools
   A. Rapidly
   B. Very slowly in furnace
   C. In air
   D. In water
   Answer: B. Slow. (Key point: Annealing)

## Related in Civil Engineering Materials

- [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, objectives, isothermal annealing](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aheat-treatment-isothermal-annealing-s) — Civil Engineering Materials, chapter 8
- [Mechanical treatment of steel](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Amechanical-treatment-steel) — Civil Engineering Materials, chapter 8, asked 2×
- [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
- [Isothermal annealing and quenching](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aheat-treatment-isothermal-annealing-quenching) — Civil Engineering Materials, chapter 8
- [Principle of heat treatment of metal](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aheat-treatment-principle) — Civil Engineering Materials, chapter 8, asked 5×

## 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
- [Annealing, normalizing and tempering of steel](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aheat-treatment-annealing-normalizing-tempering) — Workshop Technology, chapter 7
- [Faraday's laws; mechanical to heat energy](https://www.bctengineer.com/question.md?key=semester_1%2Fengineering_physics%3Afaraday-law-mechanical-to-heat) — Engineering Physics, chapter 8