BAHIR DAR UNIVERSITY
BAHIR DAR INSTITUTE OF TECHNOLOGY
i
Table of Contents
List of figures ............................................................................................................................................... iii
ii
1. Annealing .................................................................................................................................................. 2
1.2. Process Annealing ................................................................. Ошибка! Закладка не определена.
1.2.1 Normalizing ................................................................... Ошибка! Закладка не определена.
1.2.2. Full Anneal.................................................................... Ошибка! Закладка не определена.
2 Different between continuous casting and ingot casting....................................................................... 9
2.1. Continuous Casting ......................................................................................................................... 10
2.1.1. Advantages of Continuous Casting ......................................................................................... 10
2.2. Ingot Casting ................................................................................................................................... 11
2.2.1. Critical Indicators for Casting Ingots ...................................................................................... 11
2.2.2. Improvement Direction of Cast Ingots Casting ...................................................................... 11
3 Different between cold and Hot Rolling process of manufacturing......................................................... 12
3.1. What is Hot Rolled Steel? ............................................................................................................... 12
3.1.1. Properties of Hot Rolled Steel ................................................................................................ 12
3.1.2. Benefits of Hot Rolled Steel ................................................................................................... 13
3.1.3. Drawbacks of Hot Rolled Steel............................................................................................... 13
3.1.4. Common Uses of Hot Rolled Steel ......................................................................................... 13
3.2. What is Cold Rolled Steel? ............................................................................................................. 13
3.2.1. Properties of Cold Rolled Steel............................................................................................... 14
3.2.2. Benefits of Cold Rolled Steel ................................................................................................. 14
3.2.3. Drawbacks of Cold Rolled Steel ............................................................................................. 14
3.2.4. Common Uses of Cold Rolled Steel ....................................................................................... 15
Reference .................................................................................................................................................... 15
List of figures
Figure 1:The iron–iron carbide phase diagram in the vicinity of the eutectoid, indicating heat-treating
temperature ranges for plain carbon steels. (Adapt from G. Krauss, Steels: Heat Treatment and Processing
Principles, ASM International, 1990, page 108.) ............................. Ошибка! Закладка не определена.
Figure 2:continuous casting ........................................................................................................................ 10
Figure 3:Ingot Casting ................................................................................................................................ 11
Figure 4:Hot Rolled Steel ........................................................................................................................... 12
Figure 5:Cold rolled steel............................................................................................................................ 14
iii
1. Introduction
Gecdsbjkkkkkkkkznfgggggggggggggggggggggggggggggggggggggggggggggg
።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።።
1
n።።።
VJ።።።
2. Annealing
The term annealing refers to a heat treatment in which a material is exposed to an elevated temperature for an extended time period
and then slowly cooled. Ordinarily, annealing is carried out to
1) relieve stresses;
2) increase softness, ductility, and toughness; and/or
3) produce a specific microstructure. A variety of annealing heat treatments are possible; they are characterized by the changes
that are induced, which many times are microstructural and are responsible for the alteration of the mechanical properties.
Figure 1 Annealing Treatment (a material being heated to a specific temperature.)
Key Stages of Annealing
2
Stages of Annealing
Image Description: The image provides a graphical representation of the annealing stages. It shows the relationship
between annealing time and temperature.
To better understand annealing, we can divide it into three essential stages. Each step involves a change in geometry and
material properties.
Stage 01: Heating (Recovery Stage)
First, the metal is heated to a temperature between 400C and 900C, depending on its composition. This temperature is usually
above the material’s recrystallization temperature but below its melting temperature. The objective is to enable atomic
rearrangement without inducing phase change.
Stage 02: Holing (Recrystallization Stage) holding or “soaking” at that temperature,
Then, the metal is held at an elevated temperature mentioned above for a controlled period. It ensures uniform distribution of
heat, which in turn allows structural changes. The soaking time depends on the material thickness and the desired properties.
Stage 03: Cooling (Grain Growth Stage)
3
Finally, the material is cooled at a controlled rate to obtain the desired mechanical properties. The cooling can be slow (in a
furnace), moderate (in still air), or rapid (in water or oil). So, the cooling method influences the final hardness and grain
structure.
What Are the Common Types of Annealing?
The process has various purposes for achieving the best manufacturing outcomes. In this section, we will examine the most
frequently used part-softening treatments in industrial applications.
Full Annealing
The Full Annealing process requires heating metals beyond their critical temperature, followed by maintaining them at a
certain duration before being gradually furnace-cooled. Controlled furnace cooling helps refine the material grain structure
while softening the metal and improving its machining properties. Manufacturing sectors like automobiles and heavy
equipment utilize full annealing procedures to improve steel parts.
Process Annealing
Low-carbon steel materials regain their ductility through subcritical softening processes, also known as Process Annealing. The
metal receives heating treatment at a temperature level below its critical point while waiting for internal stresses to fade away.
Furthermore, when the material reaches the preferred softness level, it will cool in the calm surrounding air. This process
allows sheet metal and wire manufacturers to maintain material deformability when subjected to numerous shape deformations
without losing elasticity or strength.
Stress Relief Annealing
4
Stress Relieving
Image Description: The image shows a close-up view of the stress-relieving process.
Stress Relief type reduces metal internal stresses while maintaining its mechanical properties intact. In the process, the material
receives heated treatment at a specific temperature range for an established time to let welding-related stresses, machiningrelated stresses, and cold working-related stresses escape. The purpose of controlled cooling is to maintain structural stability
by preventing new distortions. The type mainly applies to aerospace, the construction sector, and pressure vessel manufacturing
companies.
Spheroidizing Annealing
Spheroidizing Annealing softens high-carbon steels, leading to better machining capabilities. The material undergoes heating
below its lower critical temperature for an adequate duration to achieve spheroidized carbides. The structured carbide
arrangement minimizes the resistance to the cutting tool, leading to higher machining efficiency. The method serves tool
manufacturers, bearing producers, and high-strength steel fabricators to improve tool shaping and extend operational life.
5
Types
Temperature Range
Cooling Method
Full Annealing
Above recrystallization temp Furnace cooling
Key Benefits
Common Applic
ations
Improves machinability Automotive,
machinery
Process Annealing
Below critical temp.
Air cooling
Restores ductility
Sheetmetal, wire
s
Stress-Relief Annealing
Low heat treatment
Moderate cooling Removes internal stress Welded
es
structures,
aerospace
Spheroidizing Annealing
Just below critical temp
Slow cooling
Softens high-carbon
Tool-making,
steel
bearings
Isothermal Annealing
Above transformation temp Intermediate hold Uniform hardness
Mediumcarbon steel
Recrystallization Annealing Above recrystallization temp Air cooling
Refines grain structure Rolling,
wire drawing
Bright Annealing
Controlled atmosphere
Rapid cooling
Maintains surface finis Stainless
h
steel, precision p
arts
Isothermal Annealing
Isothermal Annealing requires heating metal substances past their transformation point. During the process, the metal
undergoes cooling at an intermediate level, allowing the material to reach equilibrium. This industrial process produces
uniform hardness and structural stability. It also delivers uniform microstructural features and hardness properties. Therefore, it
works best for processing medium and high-carbon steels.
Recrystallization Annealing
Primarily, after cold working processes, metals receive recrystallization treatment to achieve refined grain structures. The
material reaches a temperature slightly higher than its recrystallization point to enable the replacement of deformed grains
through strain-free grains. The treatment restores material characteristics while suppressing work-hardening effects and
preventing the expansion of grain size.
Bright Annealing
Bright annealing protects metal from oxidation and discoloration. It involves heating the material under controlled atmosphere
conditions. When prevented from oxygen contact, the material maintains its initial surface finish, so no further polishing or
cleaning steps are required. Rapid cooling preserves its brightness and corrosion resistance. The medical sector, together with
semiconductor applications and precision components manufacturing, uses this method to preserve stainless steel and highperformance alloy surface quality.
Comparison of Annealing Types
The appropriate type is usually selected based on the type of material, required hardness, and desired application. Here’s an
analysis of each annealing type.
Advantages of Annealing?
6
Improving ductility: Annealing can be used to increase the ductility of a metal material. Ductility is a measure of a
material’s ability to deform under stress without breaking. By increasing the ductility of a material, it becomes more
resistant to cracking, breaking or shattering under stress.
Improving toughness: Annealing can also be used to increase the toughness of a metal material. Toughness is a
measure of a material’s ability to absorb energy before breaking. By increasing the toughness of a material, it
becomes more resistant to impact and other types of mechanical stress.
Improving machinability: Annealing can also be used to improve the machinability of a metal material.
Machinability is a measure of a material’s ability to be shaped, formed or machined. By improving the machinability
of a material, it becomes easier to work with, which can reduce the cost of manufacturing and production.
Relieving internal stresses: Annealing can also be used to relieve internal stresses in a metal material. Internal
stresses are caused by factors such as cold working, welding, and casting. By relieving these internal stresses, the
material becomes more stable and less likely to warp or crack.
Improving grain structure: Annealing can also be used to improve the grain structure of a metal material. The
grain structure of a material is its internal microstructure, which is composed of small crystals called grains. By
improving the grain structure of a material, it can become stronger, tougher and more ductile.
Softening hard materials: Annealing can also be used to soften hard materials like steel, allowing them to be
shaped, bent and machined more easily.
Improving the corrosion resistance: Annealing can also improve the corrosion resistance of the material, by
homogenizing the microstructure, and removing internal stresses which can cause premature corrosion.
Overall, annealing is a versatile heat treatment process that can be used to improve a wide range of properties in
metal materials. It can increase ductility, toughness, machinability, relieve internal stresses, improve grain structure,
soften hard materials, and increase corrosion resistance. These improved properties can make the material more
suitable for different applications, more durable, and more cost-effective to produce.
Disadvantages of Annealing?
While annealing is a widely used heat treatment process with numerous advantages, there are also some
disadvantages associated with it. Here are some of the potential drawbacks of annealing:
1. Time-Consuming:
 Annealing processes often require extended periods of time, especially when slow cooling is
involved. This can lead to increased production times and, consequently, higher costs.
7
2. Energy Consumption:
 Annealing processes typically involve heating materials to elevated temperatures, which can be
energy-intensive. The need for furnaces operating at high temperatures may result in increased
energy consumption and associated costs.
3. Size Limitations:
 Large and bulky components may face challenges during the annealing process due to the size
limitations of available furnaces. Achieving uniform heating and cooling throughout large pieces
can be more challenging.
4. Microstructure Variability:
 Achieving consistent and uniform microstructural changes throughout a material can be
challenging, especially in complex or heterogeneous materials. Variations in the cooling rate,
temperature distribution, or material composition can lead to non-uniform results.
5. Potential for Distortion:
 Depending on the material and the specific annealing process, there is a risk of distortion or
warping of the material. This can be a concern, particularly when dealing with intricate or precision
components.
6. Not Suitable for All Materials:
 Annealing may not be suitable for all types of materials. Some materials may not respond well to
the process, or the desired changes in properties may not be achievable through annealing alone.
7. Surface Scaling:
 In certain annealing processes, especially those involving high temperatures, there is a risk of
surface scaling or oxidation. Protective atmospheres or controlled environments may be needed
to mitigate this issue.
8. Selective Annealing Challenges:
 When dealing with materials containing multiple phases, achieving selective annealing to modify
only specific areas or phases can be challenging. Uniform treatment throughout the entire
material may be more straightforward, but selective annealing can require more precise control.
It’s important to note that the disadvantages of annealing can vary depending on the specific type of annealing
process, the material being treated, and the desired outcomes. Despite these drawbacks, annealing remains a
crucial and widely used method for improving the properties of materials in various industries.
Applications of Annealing?
Annealing is a heat treatment process that finds applications in various industries for improving the properties of
materials. Here are some common applications of annealing:
1. Metalworking:
 Softening and Ductility Improvement: Annealing is frequently used in metalworking to soften
metals and increase their ductility. This is especially important after processes like cold working
(e.g., rolling, drawing, or extrusion) that can introduce hardness and reduce ductility.
2. Steel Manufacturing:
8
Recrystallization and Grain Growth: Annealing is crucial in the steel industry to control the
microstructure of steel. Processes like full annealing, recrystallization annealing, and stress relief
annealing are used to refine grain structure, reduce internal stresses, and enhance mechanical
properties.
3. Electronics:
 Semiconductor Annealing: In the semiconductor industry, annealing is used to modify the
properties of thin films and semiconductor devices. Rapid Thermal Annealing (RTA) is a specific
technique used for precise and quick annealing of semiconductor materials.
4. Glass Manufacturing:
 Stress Relief in Glass: Annealing is applied to glass products to relieve internal stresses induced
during the manufacturing process. Slow cooling of glass products helps to prevent cracking and
improve overall strength.
5. Aerospace and Automotive Industries:
 Stress Relief in Welded Components: Welded components in aerospace and automotive
industries often undergo stress relief annealing to reduce internal stresses and improve the overall
integrity of the welded structure.
6. Magnetic Materials:
 Magnetization and Demagnetization: Annealing is used in the production of permanent
magnets to align the magnetic domains and enhance the magnetic properties of materials like
iron, cobalt, and nickel.
7. Heat Exchangers:
 Softening for Forming Processes: In the manufacturing of heat exchangers and other pressure
vessels, annealing is employed to soften the material, making it more suitable for forming
processes like bending and shaping.
8. Jewelry Manufacturing:
 Workability Enhancement: Precious metals used in jewelry, such as gold and silver, are often
annealed to improve their workability. This makes them easier to shape and mold into intricate
designs.
9. Tool and Die Production:
 Hardening and Tempering: Tool and die components are often heat-treated using processes like
annealing, hardening, and tempering to achieve the desired combination of hardness, toughness,
and wear resistance.
10. Plastic Injection Molding:
 Stress Relief in Molded Components: Annealing is employed in the plastic injection molding
process to relieve residual stresses in molded components, ensuring dimensional stability and
reducing the risk of warping or cracking.

2. Different between continuous casting and ingot casting
Continuous casting and ingot casting are popular casting methods in the casting industry. However, with the continuous development
of technology, continuous casting has made rapid progress in the modern casting industry, and it is gradually replacing casting and
9
other casting methods as the mainstream. So, what are the differences between continuous casting and ingot casting? Today, Luoyang
Giant Power will introduce it to you in detail.
2.1. Continuous Casting
Continuous casting is an advanced casting method. The principle is to pour the melting metal into a special metal type called a crystal
device, solidifying (shell) casting, continuously from the other end of the crystallizer. Pull out, it can obtain a cast of any length or
specific length.
Figure 1:continuous casting
2.1.1. Advantages of Continuous Casting
At present, in the casting industry, most steel plants apply continuous casting to produce various products. Continuous casting has the
following advantages.
1. Because of quickly cooled, the crystals are dense, the tissue is uniform, and the mechanical performance is better;
2. During continuous casting, there is no pouring system on the casting. Therefore, continuous ingots do not need to cut the head to the
end when rolling. It saves metals, and increases income;
3. Simplify the process, thereby reducing the intensity of labor;
4. The area required for production is also greatly reduced;
5. Continuous cast production is easy to achieve through mechanization and automation. What's more, continuous casting and rolling
can be achieved when casting ingots, which greatly improves production efficiency.
10
2.2. Ingot Casting
The ingot, melting metal is injected into the steel ingot mold through the steel water pack, and the process of condensing into the steel
ingot is also called mold casting, which is the last process of steelmaking. The qualified molten steel refined by the steelmaking furnace
must be cast into steel ingots or casts with a certain section shape and size for further usage.
Figure 2:Ingot Casting
2.2.1. Critical Indicators for Casting Ingots
The quantity and quality requirements of steel ingots are the basis of various technical and economic indicators of steelmaking. Steel
water income rate, the qualification rate of the steel ingot, the steel ingot mold and the refractory material consumption all directly
affect the material and energy consumption and the cost of the steel. Ingots are usually the slowest and weakest parts of various
processes of steelmaking production. To improve the production capacity of nuggets, you can dig into the production potential of
steelmaking. Therefore, expanding the type of ingot, increasing the speed of injection, and improving the efficiency has always been
an important technical measure for existing steel mills to excavate potential transformation.
2.2.2. Improvement Direction of Cast Ingots Casting
1. Promote the refined process outside the furnace in the mold-cast steel plant to improve the fluctuation range of steel water cleanliness
and reduce the temperature and composition of steel water;
11
2. Further improve the technical equipment prepared by the steel barrel, improve the process operation, and improve the automation
level of casting operations;
3. Improve the design of the steel ingot mold, continue to improve the thermal efficiency of the thermal insulation cap, improve the
material and production technology of the steel ingot, to further improve the material rate of steel ingots, and reduce the consumption
of steel ingot mold;
4. Improve the efficiency of the mechanization and cleanup of steel ingots, study improvement of steel ingot mold and bottom plate
coatings, and improve the surface quality of steel ingots;
5. Improve or develop new protection pouring processes, and reduce the secondary oxidation of steel water and mixed material
pollution in the process of eliminating the cleaning of steel to improve the cleanliness of steel ingots.
3. Different between cold and Hot Rolling process of manufacturing
3.1. What is Hot Rolled Steel?
Rolling refers to the specific way the steel material is produced. Hot rolled steel refers to steel produced with extreme heat treatment.
That is, the production occurs at extreme temperatures. Manufacturers begin with large, rectangular metals (billets). They then heat the
billets
before
sending
them
for
processing
—
a
stage
where
they
are
flattened
into
Figure 3:Hot Rolled Steel
3.1.1. Properties of Hot Rolled Steel
The following properties will help you identify hot rolled steel:

Scaled surface — cooling from high temperatures leaves remnants on the steel surface to make it look scaly.
12
large
rolls.

Slight distortions — cooling also produces slightly trapezoidal shapes without perfect angles.

Corners and edges are slightly rounded — this is a result of shrinkages and less precision in finishing.
3.1.2. Benefits of Hot Rolled Steel
Hot rolled steel offers the following benefits for your applications:
Lower Cost: The processing of hot rolled steel is much less than cold rolled steel, making it cheaper.
Little to No Internal Stresses: The cooling of hot rolled steel occurs at room temperature, making it essentially normalized.
This means that it has little or no internal stresses due to work-hardening or quenching processes.
 Easier Workability: Since the hot rolling process is done at extremely high temperatures, the resulting steel is easier to shape
and form. The most common shapes come from hot rolled steel, e.g., UB, UC, RHS, SHS, flats, etc.
 Weldability: Uniform microstructure and ductility of hot rolled steel help to lower residual stresses and improve thermal
tolerance, therefore guaranteeing robust, crack-resistant welds. Its low carbon content enhances weldability, although postweld treatments may still be needed to further optimize performance.
 Applications: It is ideal for applications where tolerance is not the priority.


3.1.3. Drawbacks of Hot Rolled Steel



Dimensional defects due to expansion during heating and shrinkage/warpage while cooling down.
It often has a rough texture on the surface that needs to be removed or bugged before any finishing process.
Slight distortions.
3.1.4. Common Uses of Hot Rolled Steel
As discussed earlier, hot rolled steel slightly shrinks as it cools. This causes manufacturers to have lesser control over the final shape.
Therefore, the applications of hot rolled steel are usually those that do not require tight tolerances, including the following:




Automobile parts, e.g., wheel rims and frames
Agricultural equipment
Railway equipment, e.g., tracks and train components
Construction materials
3.2. What is Cold Rolled Steel?
Essentially, cold rolled steel refers to hot rolled steel that has undergone further processing. As mentioned earlier, rolling involves the
range of processes involved in forming the steel, including turning, grinding, and polishing. The other operations modify an existing
hot rolled steel into a more refined product. The term “cold rolled” essentially applies to steels that have undergone compression.
13
Figure 4:Cold rolled steel
3.2.1. Properties of Cold Rolled Steel
The following features will help you identify cold rolled steel:




Smooth surfaces usually have an oily-like touch
The surface has better finish qualities and tighter tolerances
Square bars come with well-defined edges
Tubes often possess better straightness and concentric uniformity
3.2.2. Benefits of Cold Rolled Steel
Here are some of the benefits you can get from using cold rolled steel:
Better Surface Properties: Parts made with cold rolled steel often have smooth and shiny surfaces void of scale or rust. Thus,
making them useful when aesthetics is essential.
 Greater Strength: They are typically stronger and harder (up to 20% greater strength) than hot rolled steel. This makes them
useful for high-stress applications.
 Higher Precision: Since cold rolled steel does not shrink while forming, it allows for the fabrication of more precise parts
with consistent and accurate shapes.
 Various Surface Finish: It supports an extensive range of surface finishes.

3.2.3. Drawbacks of Cold Rolled Steel


More expensive due to the additional processing involved.
Internal stresses occur in the material due to additional treatments leading to unpredictable warping in some cases.
14

Fewer shapes are available, e.g., sheets and box section shapes.
3.2.4. Common Uses of Cold Rolled Steel
The ideal applications for cold rolled steel are those requiring better metal surface finishing and tighter tolerances. Examples of such
components include the following:





Aerospace parts
Mechanical components
Home appliances
Rods, bars, strips, and sheets
Metal furniture structures
Reference:
Callister, W. D.., & Rethwisch, D. G. (2009). Materials science and engineering: an introduction. John Wiley.
https://www.rebarmill.com/differences-between-continuous-casting-and-ingot-casting/
https://www.rapiddirect.com/blg/hot-rolled-vs-cold-rolled-steel/
15