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

# Short note: alloys of steel

Civil Engineering Materials · Chapter 8: Metals and Alloys

- Asked in: 2066 Shrawan (old course), 4 marks
- Video: [Introduction to Construction Materials: Steel](https://www.youtube.com/watch?v=bDlVD7vajGM) — Ahmed WA Hammad
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/alloys-of-steel-note
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-8

## Question

Write a short note on alloys of steel.

## Short answer

Alloy steels contain elements beyond carbon to improve properties: stainless (Cr-Ni) resists corrosion, manganese steel (12-14% Mn) is very tough for rail crossings, high-speed steel (W, Cr, V) keeps hardness at heat, and silicon steel gives magnetic cores.

## Answer

**Alloy steels** are steels that contain one or more alloying elements other than carbon (such as Cr, Ni, Mn, Mo, V, W, Si) in amounts large enough to give special properties.

#### Common alloy steels
| Alloy steel | Main elements | Properties and uses |
|---|---|---|
| Stainless steel | Cr (11-18%), Ni | Corrosion resistant; kitchenware, cladding, railings |
| Nickel steel | Ni 2-5% | Strong and tough; bridges, gears |
| Chrome steel | Cr 0.5-2% | Hard, wear resistant; ball bearings, tools |
| Manganese steel | Mn 12-14% | Very tough, wear resistant; rail crossings, crushers |
| Tungsten / high speed steel | W, Cr, V | Retains hardness at high temperature; cutting tools |
| Silicon steel | Si 1-4% | Magnetic properties; transformer cores |
| Vanadium steel | V | Fatigue resistant, tough; springs, axles |
| High strength low alloy steel | Cu, Cr, Ni small | Weather-resistant (COR-TEN); bridges |

Alloying improves strength, hardness, toughness, corrosion and heat resistance, but increases cost.

## Check yourself

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

1. Alloy steels are steels that:
   A. Contain alloying elements besides carbon in enough quantity to give special properties
   B. Contain only carbon
   C. Contain no iron
   D. Are cast iron
   Answer: A. Alloying elements (usually above 1-2%) give special properties. (Key point: Alloy steel definition)

2. Stainless steel contains mainly:
   A. Mn 12-14%
   B. Si 1-4%
   C. W and V
   D. Cr 11-18% with Ni
   Answer: D. Chromium gives corrosion resistance; used for kitchen ware, cladding and railings. (Key point: Stainless steel)

3. Which pairing is correct?
   A. Manganese steel: transformer cores; silicon steel: rail crossings
   B. Manganese steel (12-14% Mn): very tough, rail crossings, crushers; silicon steel: transformer cores
   C. Both used for ball bearings
   D. Silicon steel: cutting tools
   Answer: B. Mn steel is wear resistant; Si steel has magnetic properties. (Key point: Manganese and silicon steels)

4. Which is correct?
   A. High speed steel (W, Cr, V) retains hardness at high temperature for cutting tools; HSLA is weather-resistant like COR-TEN
   B. HSLA is used for cutting tools; HSS for bridges
   C. Both are non-ferrous
   D. HSS loses hardness when hot
   Answer: A. HSS retains hardness when hot; HSLA steels such as COR-TEN resist weathering. (Key point: High speed and HSLA)

## Related in other subjects

- [Aluminium alloys compared with steel](https://www.bctengineer.com/question.md?key=semester_3%2Fmaterial_science%3Aaluminium-versus-steel-applications) — Material Science, chapter 9