Metallurgy Flashcards
What is the definition of metal
- it is a solid at room temp
- it is opaque(not transparent)
- it conducts heat and electricity
- it reflects light when polished
- it expands when heated and contracts when cooled
- it has a crystal structure
What is ferrous metals?
Iron is the major ingredient and are usually magnetic.
They are alloys of iron and steel
Very high carbon steel is used to make punches, dies, sheer blades and cutting tools often called tool steels or high speed steels
Describe non ferrous metals?
Do not have iron in large enough amounts to have any major influence.
Aluminum, magnesium, zinc, copper, lead and brass are examples of non ferrous metals
Nickel is a-bit different because it is non ferrous but still magnetic.
What is the most practical method for identifying metal?
Visual appearance
Texture
Colour
What is the visual difference between hot and cold rolled steel
Hot rolled steel has black millscale on it
Cold rolled had shiny smooth surface
An object with rough surface is an indication that it is a?
Cast
If a solid metal has smooth outer surface it has been?
Formed
What are the most important properties to consider for metals are?
Hardness(ability for metal to resist penetration
Ductility (the ability of the material to be stretched without breaking)
Toughness (the ability of the metal to withstand shock)
Tensile strength (the ability of a metal to be pulled without breaking)
Machinability (measures the ease you can cut and shape the metal)
What method is stronger in structural steel? Hot rolling or welded?
Hot rolling
What steel is most common in building steel?
Carbon steel
What is structural steel?
Metal shaped to a certain profile
What do these numbers represent? C6x10.5
C=channel
6=size (outside flange to outside flange)
10.5=weight (lb/ft)
What do these numbers represent?
L3x3x1/4
Equal angle iron leg
L=angle iron
3= leg length
1/4= thickness
What do these numbers mean?
L8x6x1
Unequal angle iron
Longest leg always written first
How is HSS classified?
Outside dimensions and wall thickness
Why is hot rolled steel made slightly bigger?
So it can be machines finished to the nominal size
What is cold drawn wire tubing?
The act of pulling steel rod through one or more dies. This is used to make wire or tubing.
What is the difference between sheet steel and steel plate?
Thickness (sheet steel is up to 28 to 18 gauge. Steel plate is over 3/16th)
Width (sheet metal 36,48,60, and 72” steel plate 48-96”
What are the 7 classifications of metals?
Carbon steel Alloy steel Tool steel Stainless steel Aluminum and it’s alloys Copper and it’s alloys Cast iron
What is SAE?
Society of automotive engineers
What is AISI?
American iron and steel institute
Using the aisi-sae numbering system what do the numbers mean?
4140
41=type of steel
40=amount of carbon
What is the difference between carbon steel and alloy steel
Carbon steel contains carbon and iron
Alloy steel contains significant elements other then iron and carbon
What is tool steel?
High quailing steel used for cutters, tools, does, molds and jigs
Meant to be hardened after machining
What is stainless steel
Alloyed with lots of chromium. More corrosion resistant
What are the primary advantages of aluminum?
Lightweight, high machinable and corrosion resistant
What is brass
A mixture of copper and zinc
What is bronze
A mixture of copper and tin
What is harder brass or bronze?
Bronze
What is heat treatment?
The process of heating and cooling metal to change one or more of its properties.
What is pearlite
The structure of soft steal
What is martensite?
The structure of hardened steel.
It consists of angular needle like crystals
What is Austenite?
Austenite is formed when pearlite is heated to red hot cause the layers of ferrite and cementite to begin to dissolve into each other. When Austenite cools it it changes into either pearlite or martensite.
What is the basic process for heat treating steel?
Hardening - heated to form Austenite and rapidly cooled to form martensite. Only steel is .20% or more can be hardened.
Tempering - heating and cooling steel to take away the brittleness.
Annealing - use to make hardened material soft again so it can be machines
Normalizing - the process that eliminates strains and restores the proper grain structure of the steel
What is the rockwell hardness test?
A tester that determines the hardness of a specimen by measuring how far you can force a penetrator into it.
What metal do you use the penotrator with pointed diamond?
Hardened materials
When do you use the steel ball penotrator?
Softer steels and non ferrous metals
What is the Brinell hardness testing?
A hydraulic press is used to force a round penotrator into the material and the indent is measured
What are some ways to identify metal?
Chip test
Spark test
File test
Flame test
Smooth continuous chips indicate?
Soft material like aluminum copper or low carbon steel
Small brittle chips indicate?
Higher carbon steels
Low carbon steel produces what kind of sparks?
Bright, long, straight, yellowish
High carbon steel sparks?
Burst near the wheel, darker Yellow
Cast iron sparks?
Red burst near the grinder wheel and orange-yellow further out. May have to apply more pressure to produce sparks
High speed steal sparks?
Lines are orange with very little branching and end up in ball shaped sparks
What is an alloy?
A mixture of a metal with other metals or non metals
Metal weight chart
Cold rolled steel has a smooth grey surface and is produced by cleaning the scale from hot rolled billets then drawing them through rollers or dies until desired shape and size is reached. Why is cold rolled steel more expensive then hot rolled?
Cold rolling is a finishing process
Why does cold rolled steel tend to warp when cut?
The process of cold rolling sets up internal stresses
Carbon content of:
Low carbon steel
Medium carbon steel
High carbon steel
Cast iron
.02-.30% cannot be hardened most parts are made of low carbon steel
.30 - .60% better mechanical properties than low carbon steel and higher tensile strength. Can be hardened found in hand tools
Over .60% meant to be hardened and is found in cutting tools like taps and drills.
Cast iron is anything over 1.7% carbon
Why must quenching be done immediately after it has been sufficiently heated when hardening?
If the steel is allowed to cool, it reverts to pearlite (soft steel) instead of martensite(hardened steel)
What is most effective quenching?
Brine followed by:
Water
Oil
Air
When do you want to temper the steel and why?
Temper must be done immediately after hardening or it will crack.
Tempering draws out the brittleness cause by the hardening process
Tempering steel involves 3 steps
1: heating the steel carefully and observing color changes.
2: stop heating when area you are tempering reached the right temperature
3: quench
When file testing steel what are some key points to remember?
1: if the metal can be filed, then it can be drilled, turned, or milled. If it cannot be filed the work piece must be ground
2: helps select the correct hardness scale thereby preventing damage to the penetrator.
3: can tell you if the work piece has been properly hardened. If the file bites in it means it was not hardened properly
File action in Rockwell scale
Hot rolled steel characteristics?
Scaled surface
Rounded edges
Slight irregularities
More ductile/malleable/ tough than cold rolled
Cold roll steel characteristics
Cleaner surface finish
Square edges
Better dimensional accuracy
Harder and stronger than hot rolled
