Iron and Steel in Construction

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the process of heating steel to a temperature slightly lower than for normalizing and cooling it several hundred degrees very slowly?

Tempering

Quenching

Annealing (correct)

Forging

Which mechanical test is the most important for structural steel?

Hardness test

Impact test

Tension test (correct)

Bending test

What is the purpose of tempering in the heat treatment of steel?

To increase the hardness of steel

To reduce the residual stresses and increase ductility (correct)

To change the color of steel

To improve the corrosion resistance of steel

What is the shape of a typical tensile test specimen?

Circular cross section Signup and view all the answers

How is tensile stress calculated?

By dividing the force by the original cross-sectional area Signup and view all the answers

What is the process of deforming steel by pressure or blows into a desired shape?

Forging Signup and view all the answers

What is the primary characteristic that determines the mechanical properties of iron and steel?

Internal crystalline structure Signup and view all the answers

What happens to the atoms in iron and steel when they are subjected to strain?

They move closer together in compression or farther apart in tension Signup and view all the answers

What is the effect of rapid cooling on the crystals of iron and steel?

It produces larger crystals Signup and view all the answers

What is the primary component of iron ore, aside from gangue?

An oxide of iron Signup and view all the answers

What is the source of carbon in the production of iron and steel?

Coke Signup and view all the answers

What is the term for the metals that include all forms of iron and steel?

Ferrous metals Signup and view all the answers

What is the primary purpose of the soaking pit in steel production?

To cool the steel to a uniform temperature throughout Signup and view all the answers

What is the primary factor that influences the properties of steel?

The mechanical operations that shape the steel Signup and view all the answers

What is the significance of the first digit in the designation of a type of steel?

It indicates the class of steel Signup and view all the answers

What is the primary difference between the SAE system and the AISC system of designating structural steel?

The SAE system has added letter prefixes to designate the steel-making process used Signup and view all the answers

What is the typical shape of an ingot of steel?

Square or rectangular and tall Signup and view all the answers

What is the range of weight for an ingot of steel?

From hundreds of pounds to many tons Signup and view all the answers

What is the primary purpose of the steel erection process?

To connect pre-cut pieces of rolled sections to form the structure Signup and view all the answers

Which type of steel is widely used for buildings and bridges?

Carbon Steel Signup and view all the answers

What is the range of yield stress for designing steel structures?

24 to 100 Ksi Signup and view all the answers

What is the primary purpose of applying a shop coat of paint to steel?

To protect the steel until final painting on-site Signup and view all the answers

What is a common structural component fabricated from angles and rods?

Open-web steel joists Signup and view all the answers

What is the primary purpose of the first two or three digits in an E designation?

To indicate the minimum tensile strength in Kips per square inch Signup and view all the answers

What is the primary purpose of the fabrication process?

To cut, drill, punch, and weld steel pieces in shops Signup and view all the answers

What is the significance of the digit '3' in an E designation regarding welding positions?

It is suitable for flat welding only Signup and view all the answers

Which welding method is suited for field use?

Shielded Metal-Arc Method Signup and view all the answers

What type of weld is triangular in cross-section and is placed at a right-angle joint?

Fillet Weld Signup and view all the answers

What is the primary purpose of a Butt or Groove Weld?

To join plates edge to edge Signup and view all the answers

What is the significance of precisely cutting the pieces to be welded in a Butt or Groove Weld?

It helps to ensure the pieces meet properly Signup and view all the answers

Study Notes

Steel Properties and Classification

Each type of steel is designated by a group of numbers, where:
- The first digit indicates the class of steel (e.g., carbon steel is No. 1, nickel steel is No. 2)
- The next one or two digits indicate the approximate percentage of the major alloying element for alloy steels
- The last two or three digits indicate the carbon content in hundredths of a percent
American Iron and Steel Institute (AISI) has adopted the SAE system with some variations, adding letter prefixes to designate the steel-making process used and other letters to designate special conditions

Steel Production and Processing

Ingots are cooled to a uniform temperature throughout in a soaking pit, which is a furnace where the steel temperature is allowed to decrease to about 2300°F (1260°C)
Mechanical operations that change an ingot of steel into a useful shape include:
- Rolling: compressing and shaping an ingot into a useful shape
- Extrusion: forcing a billet of hot, plastic steel through a die of the desired shape
- Drawing: pulling steel through a small die
- Forging: deforming steel by pressure or blows into a desired shape
- Normalizing: heating the steel to a temperature of about 1500°F (815°C) or higher
- Annealing: heating the steel to a temperature slightly lower than for normalizing and cooling it several hundred degrees very slowly
- Quenching: cooling steel very rapidly in oil, water, or brine from a temperature of about 1500°F (815°C)
- Tempering: reheating the quenched steel to a temperature of 300 to 1200°F (150 to 650°C) and cooling in air to reduce the residual stresses and increase ductility

Steel Tensile Test

Mechanical tests for steel include tension, bending, hardness, and impact
For structural steel, the tension or tensile test is the most important
Typical Tensile Test Specimen is a 0.500-in.-diameter cylinder machined to a smooth, accurate circular cross section
Tensile stress is calculated by dividing the force by the original cross-sectional area
Strain is calculated by dividing the increase in distance between the marks by the original 2-in distance

Steel Designations and Welding

All designations begin with the letter E, followed by a four- or five-digit number
The first two or three digits indicate the minimum tensile strength in Kips per square inch
The next digit indicates the recommended welding positions (1: all positions, 2: flat and horizontal, 3: flat only)
The next digit indicates current supply and recommended welding techniques
Welding methods include:
- Shielded Metal-Arc Method (manual method suited for field use)
- Submerged-Arc Method (powdered flux is automatically spread ahead of the electrode)
- Gas Metal-Arc Welding (a coil of electrode wire is constantly fed to a holder as the electrode melts)
- Flux-Cored Arc Welding (used to facilitate continuous feeding of the electrode as welding takes place)
Weld types include:
- Fillet Weld (most frequently used type, triangular in cross section, placed at a right-angle joint)
- Butt or Groove Weld (ends to be connected are butted together and welded, flat edges, Single-V, and Double-V are most common grooves)

Iron and Steel

Iron in its various forms, including steel, is by far the most important of the metals used in the construction industry
Ferrous metals include all forms of iron and steel
Iron and steel appear to be smooth and uniform, yet they consist of particles called grains or crystals that can be distinguished under a microscope
Grains are formed as the metal passes from the liquid to the solid state
Constitution is an internal crystalline structure that determines to a great extent what mechanical properties the metal will have

Structural Steel

Structural Steel encompasses rolled shapes, plates, connectors, and bracing used in structural frames
It includes most steel directly attached to the frame, excluding certain items like grating, metal deck, and ornamental metal
Yield Stress is the basis for designing steel structures, typically ranging from 24 to 100 Ksi
Types of structural steels include:
- Carbon Steel (contains a maximum of 0.29% carbon and is widely used for buildings and bridges)
- High-Strength, Low-Alloy (HSLA) Steel (contains small amounts of alloying elements to enhance mechanical properties and resistance to rust)
- Corrosion-Resistant, High-Strength, Low-Alloy (CR-HSLA) Steel (offers enhanced corrosion resistance and forms a protective coating over time when exposed to the atmosphere)
- Quenched and Tempered Alloy Steel (available only as plates, with high yield stresses and specific heat treatment requirements)

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of iron and steel, the most widely used metals in the construction industry. Learn about their structure, composition, and properties. Understand how iron and steel are formed and what gives them their unique strength.