Carbon Steel Research

Tài liệu này là một báo cáo giữa kỳ của Đại học Công nghiệp Thành phố Hồ Chí Minh, tập trung vào vật liệu thép carbon. Báo cáo đi sâu vào các đặc tính vật lý (như mật độ, điện trở suất, độ dẫn nhiệt), hóa học (như khả năng phản ứng và chống ăn mòn ở nhiệt độ cao), và cơ học (như độ bền kéo, độ cứng, độ dẻo và độ dai) của thép carbon. Nó cũng phân loại thép carbon thành các loại thấp, trung bình và cao, đồng thời thảo luận về các phương pháp nhận dạng và ứng dụng đa dạng của chúng trong các ngành công nghiệp.

Ministry of Industry and TradeIndustrial University of Ho Chi Minh CityFaculty of Mechanical Engineering

Midterm ReportSubject: Introduction to Mechanical Engineering

Tittle: Material (Carbon Steel)

Lecturer: Võ Ngọc Yến Phương, PhD

Student’s Names: Nguyễn Thành Luân ID: 23655841

Table of Contents

I Categorize of Carbon Steel 1

i General Characteristics 1

ii Low, medium, high carbon 1

iii Identification Methods 2

iii.1 Spark Testing Method: 2

iii.2 Hardness Testing Method: 2

II Carbon Steel Properties 3

i Physical properties 3

i.1 Density 3

i.2 Electrical and Heat Properties 3

ii Chemical properties 5

ii.1 Reactivity and Corrosion Resistance 5

ii.2 Chemical Behaviors at High Temperatures 6

iii Mechanical properties 7

iii.1 Strength and Hardness 7

iii.2 Ductility and Toughness 8

III Application of Carbon Steel 9

i Construction 9

ii Industry 9

iii Space applications 12

iv Military 13

IV Conclusion 13

i Carbon Steel compares to other metals 13

ii Summary of Carbon Steel’s Importance 15

V Conclusion 15

VI Reviews 16

i Construction 16

ii Industry 17

iii Space applications 18

iv Military 19

VII References 20

Steel is an alloy primarily made of iron and carbon, with other elements such asmanganese, silicon, sulfur, and phosphorus Steel has outstanding properties such ashigh mechanical strength, good corrosion resistance, and the ability to withstandstrong impacts Due to these characteristics, steel is widely used in many fields such asconstruction, automobile manufacturing, mechanical engineering, the oil and gasindustry, and shipbuilding The steel production process typically begins with iron oresmelting, followed by stages such as melting, heating, rolling, drawing, and finallyshaping according to usage requirements

Steel has been used for thousands of years, with ancient Egyptians craftingweapons and tools from it Its widespread industrial use began in the 19th century withthe Bessemer process (1856) and advanced further with 20th-century electricsteelmaking Earlier manual methods produced inconsistent quality, but modernmetallurgical advancements revolutionized production and fueled the industrial boom

In the early 20th century, steel became the primary material in the manufacturingindustry The advent of efficient steel production methods helped the mechanicalengineering industry thrive, especially in the production of machinery, industrialequipment, construction projects, and transportation vehicles Steel played a crucialrole in building infrastructure and developing heavy industry

In the 1960s and 1970s, the steel industry continued to grow rapidly with theapplication of alloy steels and stainless steels These types of steel have highapplicability in the production of industrial equipment, machine parts requiringprecision, and high wear resistance

Today, steel continues to play an extremely important role in mechanicalengineering, especially in industries such as automotive, aerospace, shipbuilding,construction, and machinery production The development of steel technologies, such

as lightweight steel, high-strength steel, and smart steel, has opened up many newapplication possibilities in production and manufacturing fields

I Categorize of Carbon Steel

i General Characteristics

Carbon steel is steel that primarily contains carbon as a major component, and it isclassified based on its carbon content(ranging form 0.5% to 1.5% of carbon) It hasimportant physical, chemical, and mechanical properties that influence its applications

1 High Strength: Steel has good load-bearing capacity, especially alloy steel and carbon steel

high-2 Good Heat Resistance: Steel has high heat resistance, particularly tool steel and alloysteel

3 Corrosion Resistance: Stainless steel resists corrosion from water and air

4 Electrical and Thermal Conductivity: Steel has the ability to conduct heat andelectricity

5 High Hardness: Steel has wear resistance, especially high-carbon steel

6 Good Weldability: It can be easily welded to connect components

7 Wide Applications: Steel is used in construction, machinery manufacturing,automobiles, and many other industries

ii Low, medium, high carbon

Table 1: Comparison of Low, Medium, and High Carbon Steel Properties and Applications

carbon steel prone to brittleness

Applications Construction,

household products, automobiles

Machinery, mechanical parts,construction

Cutting tools, duty machine parts

heavy-Advantages Low cost, easy to

machine

Better strength and hardness than low carbon steel

Excellent tensile strength and wear resistance

Disadvantages Low strength, poor

corrosion resistance

Harder to machine, not as strong as high carbon steel

Hard to machine, brittle, not suitable for impact-resistant applications

iii Identification Methods

iii.1 Spark Testing Method:

Description: Carbon steel produces sparks when ground or cut The characteristics

of the sparks vary depending on the carbon content

 Low Carbon Steel: Short sparks, few branches, light yellow color

 Medium Carbon Steel: Longer sparks, more branches, bright yellow or red color

 High Carbon Steel: Long, strong sparks, many branches, bright red or white color

Procedure: Use a cutting or grinding tool to work with the steel and observe thesparks to determine the type of steel

iii.2 Hardness Testing Method:

Description: Carbon steel has different hardness and strength levels depending onthe carbon content High-carbon steel will be harder than low-carbon steel

Procedure: Use a hardness tester (Rockwell, Vickers) to check the hardness of thesteel High-carbon steel will show a higher hardness value compared to low-carbonsteel.

II Carbon Steel Properties

i Physical properties

i.1 Density

Carbon steels have a density ranging from approximately 7.75 to 8.05 g/cm³ Thisslight variation is due to differences in alloying elements(manganese, nickel,chromium, and others) and carbon content

Table 2: Carbon steel’s density compares to some other metal

Material Density (g/cm 3 ) Key Differences

Stainless Steel 8.4 – 8.0 Similar to carbon steel but with higher

corrosion resistance

Copper Alloys 8.4 – 9.0 Generally denser than carbon steel.Aluminum ~2.7 Much lighter than carbon steel

Density of carbon steel determines several key properties, including: [1]

 Strength to weight ratio: The high density of carbon steel combined with its strength

makes it an excellent material with an outstanding strength to weight ratio, ideal forapplications like aircraft construction

 Corrosion resistance: While not as corrosion - resistant as stainless steel, carbon

steel’s density provides a protective oxide layer that minimizes corrosion fromenvironmental factors

 Machinability: Carbon steel density influences its machinability Its relative softness

compared to other metals, such as titanium, makes it easier to process and shape

i.2 Electrical and Heat Properties

Electrical resistivity, represented by the Greek letter ρ (rho), is a measure of how

strongly a material opposes the flow of electric current The lower the resistivity, themore readily the material permits the flow of electric charge

Electrical conductivity is the reciprocal quantity of resistivity Conductivity is a

measure of how well a material conducts an electric current Electric conductivity may

be represented by the Greek letter σ (sigma), κ (kappa), or γ (gamma)

To measure a material's electrical resistivity, a

straightforward method is the two-point probe

technique In this approach, two electrodes are

placed on the material's surface: one injects a

known current, and the other measures the

resulting voltage By applying Ohm's Law

(resistance equals voltage divided by current), the

material's resistivity can be calculated This

method is simple and effective for assessing the

electrical properties of various materials

By understanding and applying these fundamental properties of electricity,engineers, scientists can design and implement systems that are efficient, safe, andtailored to specific electrical requirements

Table 3: Electrical Properties of Carbon Steel compares to others materials

Material ρ (Ω•m) at 20 °C Resistivity σ (S/m) at 20 °C Conductivity

The thermal conductivity of a material is a measure of its ability to conduct heat.

It is commonly denoted by k , λ (lambda), or κ (kappa) and is measured in W·m−1·K−1

Specific Heat Capacity, is the amount of heat that must be added to one unit of

mass of the substance in order to cause an increase of one unit in temperature

Maximum Service Temperature, the highest temperature at which the material

can be used, for prolonged periods, without significant change in properties

One common method to measure thermal conductivity is the steady-statetechnique, where a heat source is applied to one end of the material and thetemperature difference is measured across it This allows us to calculate how well thematerial conducts heat

Picture i.2.1:

Figure 1: Two-point probe technique

demonstration

Table 4: Thermal Properties of Carbon Steel with Varying Carbon Content

Material

Thermal Conductivity (W/m·K) at 20°C

Specific Heat Capacity (kJ/(kg K)

Maximum Service Temperature( o C)

ii Chemical properties

ii.1 Reactivity and Corrosion Resistance

Carbon steel, the most widely used engineering material, accounts forapproximately 85%, of the annual steel production worldwide Despite its relativelylimited corrosion resistance, carbon steel is used in large tonnages in marineapplications, nuclear power and fossil fuel power plants, transportation, chemicalprocessing, petroleum production and refining, pipelines, mining, construction andmetal - processing equipment

The corrosion resistance of carbon steel is significantly influenced by its carboncontent Generally, as the carbon content increases steel becomes stronger and harderbut also more brittle and susceptible to corrosion This inverse relationship necessitates

a careful balance when selecting carbon steel for applications where both mechanicalstrength and resistance to corrosion are critical

To enhance the corrosion resistance of carbon steels, various alloying elementscan be introduced For instance, small additions of copper, chromium, nickel, andphosphorus have been shown to produce significant reductions in corrosion rates incertain environments These alloyed steels, often referred to as weathering steels,develop a protective oxide layer that inhibits further corrosion, making them suitablefor specific atmospheric conditions

Table 5: Corrosion Resistance and Reactivity of Carbon Steels

Property Low Carbon Steel Medium Carbon Steel High Carbon Steel Reactivity High reactivity;

readily oxidizes when exposed to air and moisture, leading to rust formation

Moderate reactivity;

oxidizes upon exposure

to corrosive environments, though less rapidly than low carbon steel

Lower reactivity compared to lower carbon steels;

however, still prone

to oxidation without proper protection

Corrosion

Resistance Generally poor; susceptible to rust and

corrosion in moist environments

Protective coatings areoften applied to enhance resistance

Moderate; better corrosion resistance than low carbon steel but still prone to rust without protection

Protective measures are recommended

Relatively better corrosion resistance due to higher carbon content, but still vulnerable to rust over time Protectivecoatings can

improve durability

ii.2 Chemical Behaviors at High Temperatures

Carbon steel exhibits significant changes in its chemical behavior when subjected

to elevated temperatures, which can influence its mechanical properties andperformance in various applications

Decarburization

At temperatures above 700°C, carbon within the steel can react with atmosphericgases, leading to decarburization—the reduction of carbon content at the material'ssurface This process diminishes the formation of hard carbide phases, resulting in asoftened surface layer Decarburization can be detrimental in applications wheresurface hardness is critical, as it may compromise wear resistance and fatigue strength.Preventive measures include heat treatments in controlled atmospheres or applyingprotective coatings to minimize carbon loss [2]

Corrosion

Exposure to high temperatures can also

lead to oxidation, where iron in the steel reacts

with oxygen to form iron oxides on the surface

This oxide layer can affect the steel's s urface

properties and, if not controlled, may lead to

scaling and reduced cross - sectional area,

compromising structural integrity The rate of

oxidation increases with temperature and is

influenced by factors such as alloy composition Figure 2: Crossion process in air environment

and environmental conditions Protective atmospheres or alloying additions likechromium can enhance oxidation resistance [3]

Phase Transformations

Elevated temperatures

induce phase transformations

in carbon steel, altering its

microstructure and mechanical

properties Heating above the

critical temperature (~727°C)

transforms ferrite into

austenite, a face - centered

cubic structure capable of

dissolving more carbon Upon cooling,

austenite can transform into various

microstructures, such as pearlite, bainite, or

martensite, depending on the cooling rate

These transformations are exploited in heat

treatment processes to achieve desired mechanical properties

Table 6: Comparison of Carbon Steel Behaviors at High Temperatures

Property Low Carbon Steel (≤0.3% C) Medium Carbon Steel (0.3–0.6% C) High Carbon Steel (≥0.6% C) Decarburization

Oxidation

Phase Stability Stable up to ~727°C Stable up to ~727°C Stable up to ~727°C

iii Mechanical properties

iii.1 Strength and Hardness

Carbon steel's strength and hardness are primarily influenced by its carboncontent, with higher carbon levels generally enhancing these properties However, thisincrease often comes at the expense of ductility and weldability The following tableprovides a comparison of mechanical properties across different carbon steel grades.[4]

Figure 3: Austenite’s face - centered cubic

structure

Table 7: Mechanical Properties of Carbon Steels by Carbon Content

Steel(≤0.3% C)

Medium Carbon Steel(0.3 –0.6% C)

High Carbon Steel(≥0.6% C) Tensile Strength

 Tensile Strength: Represents the maximum stress that a material can withstand

while being stretched or pulled before breaking Higher carbon content typically results in increased tensile strength

 Yield Strength: Indicates the stress at which a material begins to deform

plastically As carbon content increases, yield strength also rises

 Hardness (Rockwell C): Measures the resistance of the material to indentation.

Higher carbon steels exhibit greater hardness values on the Rockwell C scale

Understanding a material's strength and hardness is crucial for selecting theappropriate material for specific applications Strength indicates how much stress amaterial can withstand before deforming or breaking, which is essential for ensuringstructural integrity under load Hardness measures a material's resistance to localizeddeformation, such as indentation or scratching, and is often correlated with wearresistance By assessing these properties, engineers can predict how materials willperform under various conditions, ensuring safety, durability, and efficiency in theirdesigns

iii.2 Ductility and Toughness

Ductility and toughness are essential mechanical properties of carbon steels,significantly influenced by their carbon content

Ductility

Ductility refers to a material's ability to undergo significant plastic deformationbefore rupture, allowing it to be stretched or formed without breaking In carbon steels,ductility decreases as carbon content increases This reduction limits the material'sability to be shaped or deformed without cracking

Toughness

Toughness measures a material's capacity to absorb energy and resist fractureunder impact or sudden loads It is a combination of strength and ductility As carboncontent increases, toughness generally decreases due to reduced ductility, makinghigh-carbon steels more susceptible to brittle failure

Table 8: Ductility and Toughness of Carbon Steels by Carbon Content

Property Low Carbon Steel (≤0.3% C) Medium Carbon Steel (0.3–0.6% C) High Carbon Steel (≥0.6% C) Ductility

III Application of Carbon Steel

Because carbon steel has many outstanding advantages such as high strength andhardness, corrosion resistance, good workability and flow, and flexibility inprocessing, carbon steel is widely used in construction, industry, and aerospace space,etc,

i Construction

In construction: Use High Carbon Steel because thanks to its good corrosionresistance and high durability, high carbon steel is the ideal material for infrastructureconstruction, including: house frames, bridges and roads

Figure 4: Carbon steel frame in the building

ii Industry

Automotive industry: Medium carbon steel is used to manufacture important carparts such as car frames, doors, hoods and exhaust pipes, With its light weight andhigh hardness, medium carbon steel creates durable structures, increases space