SEEMANTA ENGINEERING COLLEGE

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

Course Title: Course Code:
Semester: Question Paper Year: Total Hrs: Ques. Paper Code:
Author:
Lesson Plan by: Designation:
Department:
Course Objective:
 AAAAAAAAAAA
 SSSSSSSS
 WWWWWW
 WWWWWW
 WWWWWW
Course Outcome:
CO 1:
CO 2:
CO 3:
CO 4:
CO 5:
CO 6:
Bloom Taxonomy:
L1: Remembering
L2: Understanding
L3: Applying
L4: Analysing
L5: Evaluation
Legend:
L: Lecture
BB: Black Board
OHP: Overhead Projector
PPT: Power Point Presentation
Question and Answer Pattern (As per BPUT Syllabus):
TOTAL NO OF QUESTION 10
PART A TOTAL NO OF ANSWER 10
EACH QUESTION WITH ANSWER CARRY 2 MARKS
TOTAL NO OF QUESTION 10
PART B TOTAL NO OF ANSWER 10
EACH QUESTION WITH ANSWER CARRY 6 MARKS
TOTAL NO OF QUESTION 6
PART C TOTAL NO OF ANSWER 6
EACH QUESTION WITH ANSWER CARRY 16 MARKS

Signature of Student with Date

1|P a g e
PART A (SHORT TYPE QUESTION AND ANSWER)
A.Q.01 Define Porosity. 2 Mark
A.A.01 Porosity is a measure of the amount of empty space in a material. It is typically defined as the
ratio of the volume of the voids to the total volume of the material, and is usually expressed as
a percentage. Porosity can be found in many materials, including rocks, soils, ceramics, and
even living organisms.

A.Q.02 What is Mild Steel? 2 Mark

A.A.02 Mild steel is a type of carbon steel with a low carbon content, typically between 0.05% and
0.25% by weight. This low carbon content makes mild steel relatively soft and ductile, and it is
also relatively inexpensive to produce. As a result, mild steel is one of the most widely used
types of steel in the world.
A.Q.03 Define unit cell. 2 Mark

A.A.03
A unit cell is the fundamental building block of a crystal lattice. It is the smallest
repeating unit that captures the overall symmetry and structure of the crystal. Unit cells
are typically defined by three parameters:

>Cell shape: The most common unit cell shapes are cubic, hexagonal, and
tetragonal, but other shapes are also possible.
>Lattice parameters: These parameters define the lengths and angles of the edges of
the unit cell.
>Position of atoms: This specifies the location of the atoms within the unit cell.

A.Q.04 What is the significance of phase diagram?

A.A.04
>Phase diagrams provide a visual representation of the conditions under which
different phases of a substance exist. This can be helpful for understanding the
behavior of materials and predicting how they will respond to changes in temperature
or pressure.

>Phase diagrams can be used to identify the conditions under which phase transitions
occur. Phase transitions are the changes that occur when a substance changes from
one phase to another, such as from a solid to a liquid or from a liquid to a gas.
Understanding these transitions is important for many applications, such as metallurgy
and chemical engineering.

>Phase diagrams can be used to determine the thermodynamic properties of a

substance. Thermodynamic properties are the properties that describe the relationship
between a substance and its environment, such as its enthalpy, entropy, and free
energy. These properties are important for understanding the behavior of substances
in a wide variety of applications.

A.Q.05 State two properties of spring materials.

A.A.05 Two important properties of spring materials are:
Signature of Student with Date

2|P a g e
 1. 1.High elastic limit: The elastic limit is the maximum stress a material can withstand
before it begins to deform permanently. Spring materials need a high elastic limit so
that they can be repeatedly compressed, stretched, or twisted without losing their
shape.

2. 2.Low modulus of elasticity: The modulus of elasticity, also known as Young's

modulus, is a measure of a material's stiffness. Spring materials need a low modulus of
elasticity so that they can easily deform under stress and then return to their original
shape when the stress is removed.

A.Q.06 heat treatment is needed?Why

A.A.06 Heat treatment is a process that alters the microstructure of a material to improve its
properties, such as hardness, strength, toughness, ductility, and elasticity. It is commonly used
for metals and alloys, and involves heating the material to a specific temperature, holding it at
that temperature for a certain amount of time, and then cooling it at a controlled rate.
A.Q.07 State two characteristics of Duralumin.
A.A.07
Duralumin is a strong, lightweight aluminum alloy with a number of desirable
properties. Here are two of its key characteristics:

1. 1.High strength-to-weight ratio: Duralumin is significantly stronger than pure aluminum,

yet it retains much of the same lightweight properties. This makes it an ideal material
for applications where strength and weight are crucial considerations, such as in
aircraft construction.

2. 2.Ductility and malleability: Duralumin is relatively soft and ductile, meaning it can be
easily rolled, forged, or extruded into various shapes. This makes it easy to work with
and form into complex components.

A.Q.08 Define polymerization.

A.A.08 Polymerization is a chemical process in which small molecules called monomers are
linked together to form a long chain molecule called a polymer. The monomers can be
the same or different, and they can be linked together in a head-to-tail or a head-to-
head fashion. The type of polymerization depends on the type of monomer and the
reaction conditions.

A.Q.09 Explain composite materials.

A.A.09
Composite materials are made from two or more different materials that are combined
to create a material with properties that are different from the individual components.
For example, fiberglass is a composite material made from glass fibers that are
embedded in a resin. The glass fibers give the fiberglass its strength, while the resin
holds the fibers together.

Signature of Student with Date

3|P a g e
 Composite materials are often stronger and lighter than traditional materials, and they
can be used in a wide variety of applications, including aerospace, automotive, and
construction

A.Q.10 What is the function of bearing?

A.A.10
Bearings are mechanical components that reduce friction and support the weight of
rotating parts. They are essential for the smooth operation of machinery and are used
in a wide variety of applications, including cars, airplanes, and appliances.

There are many different types of bearings, but they all work by allowing two surfaces
to move relative to each other while minimizing friction. This is done by using rolling
elements, such as balls or rollers, between the two surfaces. The rolling elements
distribute the load and allow the surfaces to move smoothly.

Bearings are an essential part of many machines, and they help to ensure that
machinery operates efficiently and reliably.

PART B (LONG TYPE QUESTION AND ANSWER)

B.Q.01 What is Spring? Discuss about different spring materials. 6 Mark
B.A.01 Spring, in the context of mechanical engineering, refers to a flexible, elastic object that stores mechanical
energy when it is compressed, stretched, or twisted and releases it when the force is removed. Springs
are widely used in various applications, including automotive systems, industrial machinery, consumer
products, and more. They play a crucial role in providing shock absorption, vibration isolation, and
maintaining the equilibrium of mechanical systems.

There are several types of springs, each designed to serve specific purposes. Some common types of
springs include:

1. **Coil Springs:**
- These are helical springs made of wire wound in a spiral configuration.
- They can be designed for compression, extension, or torsion applications.
- Coil springs are widely used in automotive suspension systems, mattresses, and industrial machinery.

2. **Leaf Springs:**
- Leaf springs consist of multiple layers of flexible material (usually steel strips) bound together.
- Commonly used in the suspension systems of vehicles like trucks and trailers.
- Provide a smooth ride by absorbing shocks and distributing loads.

3. **Torsion Springs:**
- Torsion springs are designed to resist twisting or rotational motion.
- Typically used in applications where a rotating force is involved, such as in door hinges or clipboards.

Signature of Student with Date

4|P a g e
 4. **Extension Springs:**
- Extension springs elongate or stretch when a load is applied to them.
- Examples include garage door springs and trampoline springs.

5. **Flat Springs:**
- These springs have a flat, usually rectangular, shape.
- Used in applications where space is limited, such as in electrical switches or relays.

6. **Constant Force Springs:**

- These springs provide a constant force throughout their range of motion.
- Often used in applications like retractable cords and window counterbalances.

7. **Belleville Washers:**
- Although not traditional springs, Belleville washers function similarly under axial loads.
- They are conical disks that can be stacked to create a spring-like effect.

Materials used in the manufacturing of springs must possess qualities like high elasticity, fatigue
resistance, and durability. Some common spring materials include:

1. **High Carbon Steel:**

- Most traditional springs are made from high carbon steel due to its excellent combination of strength
and elasticity.

2. **Stainless Steel:**
- Stainless steel is resistant to corrosion, making it suitable for applications where exposure to moisture
or harsh environments is a concern.

3. **Alloy Steels:**
- Alloy steels, such as chrome vanadium and chrome silicon, offer enhanced performance
characteristics and are often used in high-stress applications.

4. **Non-Ferrous Alloys:**
- Materials like phosphor bronze and beryllium copper are used in specific applications where non-
magnetic or non-corrosive properties are essential.

The selection of the appropriate spring material depends on factors such as the application
requirements, operating conditions, and budget constraints. Each material has its own set of advantages
and limitations, and engineers choose the one that best suits the needs of the specific application.
B.Q.02 Explain Frankel Defect with figure. 6 Mark

B.A.02
B.Q.03 Discuss about any two microconstituents of Iron & Steel. 6 Mark
B.A.03 In the context of iron and steel, microconstituents refer to the distinct phases or structures that can be
observed under a microscope. Two important microconstituents in iron and steel are ferrite and
cementite.

1. **Ferrite:**
- **Composition:** Ferrite is a solid solution of alpha iron with a small amount of carbon (up to 0.022%
at 723°C). It has a body-centered cubic (BCC) crystal structure.
- **Properties:** Ferrite is a relatively soft and ductile phase. It is magnetic and has good corrosion
resistance. The presence of ferrite in steel can enhance toughness and impact strength.

Signature of Student with Date

5|P a g e
 - **Formation:** Ferrite forms at high temperatures during the cooling of molten steel. In equilibrium
cooling, pure iron transforms entirely to ferrite at 912°C, but in practical steelmaking, other phases may
also be present.

2. **Cementite:**
- **Composition:** Cementite is an iron carbide (Fe3C), consisting of 6.7% carbon and 93.3% iron. It
has an orthorhombic crystal structure.
- **Properties:** Cementite is a hard and brittle phase. It is extremely hard and contributes to the
hardness and strength of steel. However, excessive cementite can lead to brittleness, reducing the
material's toughness.
- **Formation:** Cementite forms during the cooling of steel when the carbon content exceeds the
solubility limit of carbon in ferrite. It usually appears as a distinct phase in the microstructure, often in
the form of white, needle-like particles.

The combination and distribution of these microconstituents, along with other phases like pearlite and
martensite, determine the mechanical and metallurgical properties of the steel. The heat treatment
processes, such as annealing, quenching, and tempering, play a crucial role in controlling the formation
and distribution of these microconstituents, influencing the final properties of the steel product.
Engineers and metallurgists carefully design steel alloys and processing conditions to achieve the desired
balance of strength, toughness, and other mechanical properties based on the specific application
requirements.
B.Q.04 Classify Composite materials. Discuss about Dispersion-
strengthened Composites.

B.A.04 Composite materials are engineered materials made by combining two or more constituent materials to
achieve specific performance characteristics not easily attainable with individual components. They
typically consist of a matrix material and reinforcement elements. One category of composite materials is
dispersion-strengthened composites.

Dispersion-strengthened composites are a type of composite material where fine particles of a

strengthening phase are dispersed uniformly in a matrix material. The strengthening phase can be
metallic, ceramic, or another type of material chosen for its desirable properties. The dispersion of these
particles within the matrix enhances the overall mechanical properties of the composite.

The dispersion-strengthening process involves techniques such as powder metallurgy, mechanical

alloying, or liquid-phase dispersion. In powder metallurgy, fine particles of the strengthening phase are
mixed with the matrix material powder, followed by compaction and sintering to create a uniform
structure. Mechanical alloying involves high-energy ball milling of the matrix and strengthening phase
powders, leading to a finely mixed powder that is subsequently consolidated. Liquid-phase dispersion
incorporates a liquid phase during processing, promoting homogeneous distribution.

The key advantage of dispersion-strengthened composites is the improved mechanical properties,

including enhanced strength, hardness, and wear resistance. These materials find applications in
aerospace, automotive, and structural engineering, where high performance and reliability are crucial.
The dispersion of fine particles provides resistance against dislocation movement, resulting in improved
strength and toughness compared to the base matrix material.

In summary, dispersion-strengthened composites are a class of composite materials where uniform

dispersion of strengthening particles in a matrix enhances mechanical properties, offering a versatile
solution for various demanding applications.
B.Q.05 State the effects of adding Nickel and Molybdenum in steel as
alloying elements.
Signature of Student with Date

6|P a g e
B.A.05 Nickel and molybdenum are commonly used as alloying elements in steel to enhance its properties for
specific applications. Here are the effects of adding nickel and molybdenum to steel:

Nickel:

1. **Increased Toughness:** Nickel improves the toughness of steel, making it more resistant to impact
and shock. This is particularly important in applications where the steel is subjected to dynamic loading
or sudden stress.

2. **Corrosion Resistance:** Nickel contributes to the corrosion resistance of steel, especially in harsh
environments. It helps protect against rust and other forms of corrosion, making the steel more durable.

3. **Improved Ductility:** Nickel enhances the ductility of steel, allowing it to undergo deformation
without breaking. This is beneficial in manufacturing processes and applications that require forming and
shaping.

4. **Enhanced Heat Resistance:** Nickel improves the steel's ability to withstand high temperatures,
making it suitable for applications involving elevated temperatures, such as in the manufacturing of heat
exchangers and boilers.

5. **Magnetic Properties:** Nickel can influence the magnetic properties of steel, and certain nickel-
containing steels may exhibit magnetic characteristics useful in specific applications.

Molybdenum:

1. **Increased Strength:** Molybdenum is known for its ability to increase the strength of steel,
particularly at elevated temperatures. This makes molybdenum-containing steels suitable for high-stress
applications.

2. **Improved Hardness:** Molybdenum contributes to the hardenability of steel, enhancing its

resistance to wear and abrasion. This is beneficial in applications where the steel is subjected to friction
and mechanical wear.

3. **Corrosion Resistance:** Similar to nickel, molybdenum also improves the corrosion resistance of
steel, especially in aggressive environments such as those containing acids and corrosive chemicals.

4. **Creep Resistance:** Molybdenum enhances the creep resistance of steel, making it more suitable
for applications involving prolonged exposure to high temperatures, such as in the aerospace and power
generation industries.

5. **Reduced Sensitivity to Temper Embrittlement:** Molybdenum helps mitigate the sensitivity of steel
to temper embrittlement, which is a reduction in toughness that can occur when certain steels are
exposed to specific temperature ranges.

B.Q.06 Discuss about different bearing materials.

B.A.06 Bearing materials play a crucial role in the performance and longevity of bearings, which are mechanical
components designed to reduce friction between moving parts. The choice of bearing material depends
on various factors such as load capacity, speed, temperature, lubrication, and environmental conditions.
Here are some common bearing materials:

Signature of Student with Date

7|P a g e
 1. **Steel:**
- *Carbon Steel:* Commonly used for standard bearings. It offers good strength and hardness.
- *Stainless Steel:* Resistant to corrosion, making it suitable for applications in harsh environments or
where there's exposure to moisture.

2. **Ceramics:**
- *Silicon Nitride:* Known for its high hardness, low density, and excellent heat resistance. Ceramic
bearings often perform well in high-speed and high-temperature applications.
- *Zirconia (ZrO2):* Exhibits high strength, wear resistance, and corrosion resistance. Zirconia is used in
ceramic hybrid bearings where the rolling elements are ceramic, but the races are typically steel.

3. **Bronze:**
- *Phosphor Bronze:* Offers good corrosion resistance and is often used in low-speed, high-load
applications. It has self-lubricating properties.
- *Aluminum Bronze:* Combines good strength with excellent corrosion resistance. Aluminum bronze
bearings are suitable for heavy-load applications.

4. **Plastics:**
- *Polytetrafluoroethylene (PTFE):* Known by the brand name Teflon, PTFE is a low-friction material
with good chemical resistance. Bearings with PTFE liners are often used in low-load, high-speed
applications.
- *Nylon:* Offers good wear resistance and is often used in light-load applications. Nylon bearings are
also known for their quiet operation.

5. **Composite Materials:**
- *Fiberglass-Reinforced Plastics:* Combining the strength of fiberglass with the benefits of plastic,
these materials are used in bearings for corrosive environments.
- *Metal Matrix Composites:* Reinforcing metals with ceramic particles can enhance strength and wear
resistance.

6. **Cermet (Ceramic-Metal Composite):**

- Combining the advantages of both ceramics and metals, cermets offer improved hardness, wear
resistance, and thermal stability.

7. **Babbitt Metal:**
- Used for plain bearings, Babbitt metal is a soft alloy consisting of tin, antimony, and copper. It provides
good conformability and embeddability, making it suitable for high-speed applications.

The choice of bearing material depends on the specific requirements of the application. Factors such as
load capacity, speed, temperature, corrosion resistance, and lubrication conditions need to be carefully
considered to select the most appropriate bearing material for optimal performance and durability.
Additionally, advancements in material science continue to contribute to the development of new and
improved bearing materials with enhanced properties.
B.Q.07 Compare thermoplastic with thermosetting plastics.
B.A.07 Thermoplastic and thermosetting plastics are two broad categories of polymers, distinguished by their
response to heat and their behavior under different temperature conditions. Here's a comparison
between the two:

1. **Definition:**
- **Thermoplastics:** These are polymers that can be melted and re-molded multiple times without
undergoing any significant chemical change. They become pliable when heated and solidify when cooled.
- **Thermosetting Plastics:** These are polymers that undergo a chemical reaction (curing) when
Signature of Student with Date

8|P a g e
 heated, resulting in a rigid, infusible structure. Once set, they cannot be re-melted or re-molded.

2. **Chemical Structure:**
- **Thermoplastics:** Have a linear or branched structure with weaker intermolecular forces. The
polymer chains are held together by secondary bonds, allowing them to be easily separated and
reshaped.
- **Thermosetting Plastics:** Have a three-dimensional network structure due to the cross-linking of
polymer chains during the curing process. This cross-linking makes them rigid and unable to be reshaped.

3. **Behavior with Heat:**

- **Thermoplastics:** Soften when exposed to heat and return to a solid state upon cooling. This
process is reversible, and the material can be molded repeatedly.
- **Thermosetting Plastics:** Harden irreversibly upon heating and undergo a chemical change during
curing. Once set, they do not soften or melt upon reheating.

4. **Applications:**
- **Thermoplastics:** Widely used in applications where flexibility, recyclability, and ease of processing
are essential. Examples include packaging materials, toys, and pipes.
- **Thermosetting Plastics:** Commonly used in applications where durability, dimensional stability,
and heat resistance are critical, such as in electrical components, automotive parts, and adhesives.

5. **Recyclability:**
- **Thermoplastics:** Generally more recyclable since they can be melted and re-molded without
significant degradation of their properties.
- **Thermosetting Plastics:** Recycling is challenging because the curing process involves irreversible
chemical reactions, making it difficult to melt and reprocess them.

6. **Examples:**
- **Thermoplastics:** Polyethylene, polypropylene, PVC, and PET.
- **Thermosetting Plastics:** Epoxy, phenolic, melamine, and Bakelite.

7. **Cost:**
- **Thermoplastics:** Often less expensive due to the ease of processing and recycling.
- **Thermosetting Plastics:** Can be more expensive, especially in applications where their specific
properties are crucial.

Understanding the differences between thermoplastics and thermosetting plastics is essential for
selecting the right material for a particular application based on the desired characteristics and
performance requirements.

PART A (LONG QUESTION AND ANSWER)

A.Q.01 Discus about any four types of mechanical properties of engineering materials. 16 Mark

Signature of Student with Date

9|P a g e
A.A.01 Here are four types of mechanical properties of engineering materials:
1. Strength
Strength is the ability of a material to resist deformation or fracture under an applied
load. There are several different types of strength, including:
Tensile strength: The maximum stress that a material can withstand before it fractures
under a tensile load.
Compressive strength: The maximum stress that a material can withstand before it
fractures under a compressive load.
Shear strength: The maximum stress that a material can withstand before it fractures
under a shear load.
Strength is an important property for many engineering materials, as it determines how
much load a material can carry without breaking.
2. Hardness
Hardness is the resistance of a material to localized deformation. It is typically
measured by scratching the surface of the material with a harder material and then
measuring the width of the scratch. There are several different types of hardness,
including:
Brinell hardness: Measured by the diameter of a steel ball that is pressed into the
surface of the material.
Rockwell hardness: Measured by the depth of penetration of a diamond or ball indenter
into the surface of the material.
Vickers hardness: Measured by the area of a square pyramid that is pressed into the
surface of the material.
Hardness is an important property for materials that need to resist wear and tear, such
as cutting tools and bearings.
3. Toughness
Toughness is the ability of a material to absorb energy before it fractures. It is typically
measured by the area under the stress-strain curve of a material. Toughness is an
important property for materials that need to withstand impact loads, such as car
bumpers and safety helmets.
4. Ductility
Ductility is the ability of a material to deform under an applied load without fracturing. It
is typically measured by the elongation of a material before it fractures under a tensile
load. Ductility is an important property for materials that need to be formed into shapes,
such as wires and sheets.
These are just a few of the many mechanical properties of engineering materials. The
specific properties that are important for a particular material will depend on the
application.

Signature of Student with Date

10 | P a g e
A.Q.02 Discuss about various properties of plastic. 16 Mark
A.A.02 Plastics, or polymers, are a versatile class of materials with a wide range of properties that make them
suitable for various applications. The properties of plastics can be broadly categorized into several key
aspects:

1. **Mechanical Properties:**
- **Strength and Stiffness:** The mechanical strength of plastics varies widely, with some plastics
exhibiting high tensile strength and stiffness, making them suitable for structural applications, while
others may be more flexible.

- **Impact Resistance:** Many plastics have excellent impact resistance, which makes them suitable
for applications where the material may experience sudden or repeated impacts.

- **Flexibility and Ductility:** Plastics can be highly flexible and ductile, allowing for various forming
processes such as extrusion, injection molding, and thermoforming.

2. **Thermal Properties:**
- **Melting Point:** Plastics have a broad range of melting points. Some plastics have relatively low
melting points, making them suitable for processes like injection molding, while others can withstand
higher temperatures.

- **Thermal Conductivity:** Generally, plastics have low thermal conductivity, which makes them
good insulators. This property is advantageous in applications where thermal insulation is required.

- **Heat Resistance:** The heat resistance of plastics varies. Some plastics can withstand high
temperatures without significant degradation, while others may soften or deform at elevated
temperatures.

3. **Chemical Resistance:**
- Plastics often exhibit resistance to various chemicals, making them suitable for applications where
exposure to acids, bases, solvents, and other chemicals is a concern.

- However, the chemical resistance of plastics is material-specific, and not all plastics are resistant to
the same range of chemicals.

4. **Electrical Properties:**
- Plastics can be good electrical insulators, making them suitable for electrical and electronic
applications.

- Some plastics also have semiconducting properties, expanding their use in electronic devices.

5. **Durability and Weather Resistance:**

- Plastics can be durable and resistant to environmental factors such as UV radiation, moisture, and
weathering. This makes them suitable for outdoor applications.

- However, some plastics may degrade over time when exposed to certain environmental conditions,
and their resistance to weathering can vary.

6. **Density and Weight:**

- Plastics generally have low density, making them lightweight compared to many other materials.
This property is advantageous in applications where weight is a critical factor.

Signature of Student with Date

11 | P a g e
 7. **Transparency and Optical Properties:**
- Plastics can be transparent or translucent, making them suitable for applications like packaging,
optical lenses, and display screens.

- The optical properties of plastics can be engineered to achieve specific functionalities, such as UV
resistance or light diffusion.

It's important to note that the properties of plastics can vary widely depending on the specific type of
polymer, its molecular structure, and the additives used during processing. As a result, the selection of
a plastic material for a particular application requires careful consideration of the desired properties
and the environmental conditions the material will be exposed to.
A.Q.03 What is Tool Steel? Classify it and state its properties with composition. 16 Mark
A.A.03 Tool steel is a type of steel that is specifically designed for making tools. It is
characterized by its high hardness, wear resistance, and toughness. Tool steels are
typically classified into two main categories: cold-work steels and hot-work steels.
Cold-work steels are used for applications where the tool will not be subjected to high
temperatures, such as cutting tools, dies, and hand tools. They typically have a carbon
content of between 0.7% and 1.5%. Common cold-work steels include:
O1: A general-purpose cold-work steel with good hardness and wear resistance.
A2: A high-carbon, high-chromium cold-work steel with excellent wear resistance.
D2: A high-carbon, high-chromium, high-vanadium cold-work steel with exceptional
wear resistance.
Hot-work steels are used for applications where the tool will be subjected to high
temperatures, such as forging dies, casting dies, and hot extrusion dies. They typically
have a carbon content of between 0.5% and 1.0% and contain alloying elements such
as chromium, tungsten, molybdenum, and vanadium. Common hot-work steels
include:
H13: A high-carbon, high-chromium, high-molybdenum hot-work steel with good hot
hardness and toughness.
H11: A high-carbon, high-chromium, high-tungsten hot-work steel with excellent hot
hardness.
A6: A high-carbon, high-molybdenum, high-vanadium hot-work steel with exceptional
hot hardness and toughness.
Properties of Tool Steel:
Hardness: Tool steels are very hard, typically with a Rockwell hardness of 50 HRC or
higher. This hardness is necessary for them to cut or shape other materials without
being deformed themselves.
Wear resistance: Tool steels are also very wear resistant, meaning that they can
withstand abrasion and maintain their hardness over time. This is important for tools
that are used for repetitive cutting or forming operations.
Toughness: Tool steels are also tough, meaning that they can withstand impact without
breaking. This is important for tools that are used for applications where they may be
Signature of Student with Date

12 | P a g e
 subjected to shock loading.
Composition of Tool Steel:
The composition of tool steel varies depending on the specific grade and application.
However, all tool steels contain carbon as the primary alloying element. Carbon is
responsible for the hardness of tool steel. Other common alloying elements include
chromium, tungsten, molybdenum, and vanadium. These elements can improve the
wear resistance, toughness, and hot hardness of tool steel.
Applications of Tool Steel:
Tool steel is used in a wide variety of applications, including:
Cutting tools: Cutting tools such as drills, milling cutters, and reamers are made from
tool steel.
Dies: Dies are used to form or shape other materials. They are often made from tool
steel because of its hardness and wear resistance.
Hand tools: Hand tools such as chisels, hammers, and screwdrivers are often made
from tool steel.
Knives: Knives are made from tool steel because of its hardness, wear resistance, and
toughness.

A.Q.04 Draw Fe-C phase diagram. Explain about different phase transformations.
A.A.04
A.Q.05 Explain about different crystal structures.
A.A.05 Crystal structures refer to the specific arrangement of atoms, ions, or molecules in a crystalline
material. The arrangement is determined by the way these entities pack together in three-dimensional
space. The study of crystal structures is essential in materials science, chemistry, and physics, as it
helps to understand the properties and behaviors of materials. Here are some common crystal
structures:

1. **Cubic Crystal Structure:**

- **Simple Cubic (SC):** In this structure, atoms are located at the corners of a cube, with one atom
per corner. Simple cubic structures are rare in metals due to poor packing efficiency.

- **Body-Centered Cubic (BCC):** Atoms are present at the corners and in the center of the cube.
This structure is more common in metals like iron, tungsten, and chromium.

- **Face-Centered Cubic (FCC):** Atoms are located at the corners and in the center of each face of
the cube. This structure is common in metals like aluminum, copper, and gold. FCC structures have
higher packing efficiency compared to BCC.

2. **Hexagonal Close-Packed (HCP):**

- In HCP structures, the atoms are arranged in a close-packed hexagonal pattern, with each layer
positioned over the previous one. This structure is found in metals like magnesium and titanium.

3. **Tetragonal Crystal Structure:**

- Tetragonal structures have a rectangular or square base with atoms at the corners. These structures
are less common than cubic or hexagonal structures.

Signature of Student with Date

13 | P a g e
 4. **Orthorhombic Crystal Structure:**
- In orthorhombic structures, the unit cell has three mutually perpendicular axes of different lengths.
The atoms are arranged in a rectangular pattern. This structure is found in some minerals and metals.

5. **Rhombohedral Crystal Structure:**

- Rhombohedral structures are similar to hexagonal close-packed structures but have a different
angle between the unit cell axes. Carbon, in the form of graphite, exhibits a rhombohedral crystal
structure.

6. **Monoclinic Crystal Structure:**

- Monoclinic structures have three unequal axes, with one of them inclined to the other two. The
atoms are arranged in a parallelogram pattern.

7. **Triclinic Crystal Structure:**

- Triclinic structures have three unequal axes with no right angles. The angles between the axes are
all different, resulting in a distorted unit cell.

8. **Diamond Cubic Crystal Structure:**

- Diamond, a form of carbon, has a unique crystal structure known as diamond cubic. Each carbon
atom is bonded to four other carbon atoms in a tetrahedral arrangement.

Understanding the crystal structure of a material is crucial for predicting its physical and mechanical
properties. The arrangement of atoms affects properties such as hardness, electrical conductivity,
thermal conductivity, and optical behavior. X-ray crystallography and other techniques are used to
determine and analyze crystal structures experimentally.

Signature of Student with Date

14 | P a g e