Mechanical Properties of Steel and Manufacturing

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Questions and Answers

What is the primary purpose of using steel blooms in the axle manufacturing process?

To enhance aesthetic appearance of the axles

To improve electrical conductivity

To reduce the weight of the axles

To provide a base material for forging axles (correct)

Which mechanical property is defined as the stress at which plastic deformation begins?

Elastic modulus

Yield strength (correct)

Ultimate strength

Tensile strength

What material is commonly used for forging hammers in the railway industry?

DIN 56NiCrMoV7 (correct)

CAST Iron

Stainless Steel

Aluminium Alloy

How is ductility measured?

Through the percentage elongation before fracture Signup and view all the answers

What must be documented during the reclamation process of forging hammers?

The entire reclamation procedure Signup and view all the answers

Which property gives the maximum information about a material's mechanical characteristics?

Tensile test Signup and view all the answers

What analysis method is used to determine the hydrogen content in liquid steel?

LECO hydrogen analyzer Signup and view all the answers

What is the formula for calculating yield strength?

$rac{Py}{A0}$ Signup and view all the answers

What does a high percentage elongation indicate about a material?

It has high ductility Signup and view all the answers

Which process is required for producing steel blooms for axles?

Basic electric arc furnace process or equivalent Signup and view all the answers

What does malleability refer to in materials?

The ability to undergo plastic deformation under compressive load Signup and view all the answers

What is ultimate tensile strength defined as?

The maximum load a specimen can handle before necking occurs Signup and view all the answers

How is fracture strength mathematically represented?

σf = Pf / A0 Signup and view all the answers

What does toughness measure in a material?

The energy a material can absorb before fracture Signup and view all the answers

At what temperature does BCC iron undergo allotropic changes to become FCC iron?

912 degrees Celsius Signup and view all the answers

What structure does pure iron exist in at room temperature?

BCC structure Signup and view all the answers

What is the point at which necking occurs in a material?

After the ultimate load is reached Signup and view all the answers

Which form of iron is known as austenite?

γ-iron Signup and view all the answers

What does the right vertical axis of the Iron carbon equilibrium diagram represent?

Percentage of carbon by weight Signup and view all the answers

How does fracture strength differ from ultimate tensile strength?

Fracture strength is lower than ultimate tensile strength Signup and view all the answers

What is the maximum amount of carbon that can be added to molten iron before it becomes saturated?

6.67% Signup and view all the answers

Which phase of iron has a maximum solid solubility of 0.025% carbon at 727 degrees Celsius?

α-Ferrite Signup and view all the answers

Austenite has which of the following characteristics?

Non-stable below 727 degrees Celsius and has an FCC structure Signup and view all the answers

What phase of iron is considered the hardest structure on the Fe-C diagram?

Cementite Signup and view all the answers

Which phase forms when austenite containing exactly 0.83% carbon is cooled very slowly below 727 degrees Celsius?

Pearlite Signup and view all the answers

What is the solid solubility of carbon in δ-Ferrite at its maximum temperature of 1495 degrees Celsius?

0.1% Signup and view all the answers

What is the crystal structure of Cementite?

Orthorhombic Signup and view all the answers

Ledeburite is formed from a mixture of which two phases?

Austenite and Cementite Signup and view all the answers

Which phase is described as having a fingerprint-like appearance?

Pearlite Signup and view all the answers

What happens to the structure of austenite at 1394 degrees Celsius?

It changes from FCC to BCC Signup and view all the answers

Study Notes

Consumables Used in Axle Shop

Consumables used in Rail Wheel Factory are required from multiple suppliers
Specifications are provided to help suppliers develop and supply to RWF
Steel Blooms for forging Diesel/Electric locomotives and EMU driving axles:
- Manufactured using basic electric arc furnace or other approved processes
- Steel must meet requirements from IRS R 43 and IRS R 16
- Hydrogen and nitrogen content must be analyzed using standard LECO analyzers
Forging Hammers:
- Used to forge steel axles and armature shafts
- Made from DIN 56NiCrMoV7 steel, quenched and tempered to 34 HRC
- Reclamation process documentation is required and made available to inspecting officials

Properties of Materials

Materials are characterized by various properties
Mechanical properties are evaluated and compared using tests
Popular tests include tensile tests, compression tests, shear tests, hardness tests, impact tests, and bending tests
Tensile tests provide the most comprehensive information about mechanical properties

Mechanical Properties (Tensile Tests)

Yield Strength: Stress at which plastic deformation begins without significant load increase
Ultimate Stress: Highest stress the material can withstand before failure
Yield Stress: Stress at which the material starts to deform permanently
Proportional Limit: Stress limit where stress and strain are directly proportional
Fracture: Point of material failure
Necking: Reduction in cross-sectional area of the specimen at the point of failure
Linear region /Plasticity or yielding: region where stress and strain are linearly related
Perfect hardening: Region where the specimen continues to deform plastically without any noticeable increase in strength

Ductility

Ability of a material to undergo plastic deformation under tensile load
Measured by percentage elongation: ((L-L₀)/L₀) *100, Where L = length after test, L₀ = Original length

Malleability

Ability of a material to undergo plastic deformation under compressive load

Ultimate Tensile Strength

Maximum stress a material can withstand before failure
Calculated as (Ultimate load / Original cross-sectional area)

Fracture Strength

Stress at the point of material failure
Calculated as (Fracture load / Original cross-sectional area)

Toughness

Material's ability to withstand both elastic and plastic deformation before failure
Higher toughness indicates the material can absorb more energy before fracture

Iron-Carbon Equilibrium Diagram

Study of the constitution and structure of steels and irons
Iron exhibits allotropy (exists in multiple crystal structures at different temperatures)
Different phases of iron and carbon at varying temperatures and compositions are detailed on the diagram

Phases in the Iron-Carbon System

Alpha ferrite, Austenite, Delta ferrite, Cementite, Pearlite, and Ledeburite are explained
Their properties and structures are described.
Solid solubility of carbon is discussed for each phase at various temperatures.

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Description

This quiz covers essential concepts in mechanical properties of steel, particularly related to axle manufacturing processes. Explore topics such as yield strength, ductility measurement, and the importance of materials in forging hammers. Test your knowledge on the characteristics and behaviors of steel in various conditions.