Diapositivas

Exam 1 Review

Rachel Savino MMET 207 Inglés 35 diapositivas

Diapositivas del conjunto (35)

Rockwell Hardness Testing
- Diamond Indenter
- Process: minor load applied, major load applied, major load removed
- Minor Loads - Superficial: 3 kg , Regular: 10 kg
- Major Loads - Superficial: 15, 30, 45 kg , Regular: 60, 100, 150
- Superficial is used for thin materials
Comparison of Hardness Tests
- Knoop/Vickers: Diamond indenter, 1-2000g load, microhardness of soft steels to ceramics
- Brinell: Ball indenter, 500 and 3000 kg, soft steels
- Rockwell (Bc)(Tc)(Rc): ball indenter, 100 kg - superficial major loads - for soft
- Rockwell (Nc)(Ad)(Cc): Diamond indenter - for hard
- HARD to SOFT: Knoop/Rockwell C, Brinell, Rockwell B, Shore
Mechanical Properties
- Strength
- Tensile
- Yield
- Compression
- Flexural
- Shear
- Creep
- Stress rupture
- Stiffness
- modulus of elasticity
- flexural and shear modulus
- Formability
- elongation
- area reduction
- bend radius
- Toughness
- Impact strength
- notch sensitivity
- Durability
- Hardness
- wear resistnce
- fatigue strength
Stress and Strain
- STRESS = force/area (psi)
- STRAIN = change in length/length (in/in)
- found by tensile test
Stress-Strain Curve
- Pie de imagen: more ductile = longer x axis, a stretched graph
.2% offset yield
- When yield point cannot be found:
- set at .2% elastic strain
- using young's modulus of elasticity (slope) find point of the curve if the slope is used where x=.2%
Modulus of Elasticity
- stress/strain = E (psi) - SLOPE of graph, at the beginning
- important in choosing materials
- Steel = 30x10^6 psi
- Aluminum = 10x10^6
Standard gage length
- gage length for tensile testing = very great in comparison to diameter
Impact Testing
- used to determine material behavior at higher deformation speeds
- the higher the impact strength, the greater the fracture resistance will be
- pivoting arm drops, breaks specimen
- notch samples can be used to test notch sensitivity
- Nil-Ductility Transition: the temperature above which a material is ductile and below which it is brittle
Fatigue Strength
- tested by repeating fluctuating loads
- the number of cycles required to cause failure in a specimen against the amplitude of the cyclical stress developed
Creep Strength
- prolonged tensile or compressive load at a constant temperature. The rate of deformation of a sample material to stress at a constant temperature is known as the creep rate. It is the slope created by the creep vs. time.
Material Selection Factors
- Chemical
- composition
- phases
- grain size
- inclusions
- Physical
- Specific Heat
- thermal conductivity
- heat distortion temperature
- magnetic
- electrical
- optical
- acoustic
- density
- color
- Mechanical
- Tensile/compressive properties
- toughness
- ductility
- fatigue strength
- hardness
- creep resistance
- shear strength
- Manufacturing Considerations
- size
- shape
- surface texture
- tolerances
Blast Furnace
- outputs pig iron, high in carbon (3.5%)
- slag used in concrete
Limestone and Coke
- the production of iron historically required three important raw materials: iron ore, coke and limestone
- reduces impurities
- produces slag
- coke = converted coal
Reduction
- Happens in a blast furnace
- Removes carbon with help of oxygen
- iron (III) oxide+carbon monoxide =iron+carbon dioxideFe2O3(s)+3 CO(g) =2 Fe(l)+3 CO2(g)
Steel Refining
- Wrought iron and refined iron are products of pig iron refining
- Refining: purifying an impure metal
- Primary steelmaking: uses mostly new iron from a blast furnace
- Secondary steelmaking: uses scrap steel as raw material in electric arc furnace.
Furnaces
- Blast Furnace - iron ore, limestone and coke, hot air goes in. product: PIG IRON.
- Basic Oxygen Furnace (BOF) - uses scrap metal to make new steel by pushing in oxygen, nitrogen and argon (oxygen lance) oxygen forms CO and CO2, removes carbon, sulfur and phosphorus - 40% used in america. Capacity: 150-300 tonnes per "heat" every 30 minutes. pours out.
- Electric Arc Furnace (EAF) - uses old steel, sends electricity through to raise temperature. 35 minutes per heat. 1-400 tonnes. SECONDARY steelmaking. graphite electrodes, oxygen, lime create electric arcs. Can be shut down between uses.
Continuous Casting
- from furnace, liquid steel is in ladle, goes through tundish feeding to caster mold, straightens out and is cut. water cooled. produces 3000 heats between shutdowns.
- Inclusions, porosity, segregation and grain size
Secondary Refining
- Vacuum degassing
- vacuum arc remelting
- electroslag melting
- vacuum induction melting
- electron beam refining
- ladle stirring injection and ladle furnace heating
- KNOW ACRONYMS
- What are the metals used for after?
Steel Grades
- list, how are they achieved?
- killed
- rimmed
- capped
- semi-killed
Ingots
- how are they made
Non-metallic inclusions
- ?
Semi-finished steel forms
- figure 12-12
integrated mill vs minimill
finished forms of steel
- what is the difference between plate and sheet?
- strip and bar?
BCC FCC
- what it means, looks like
- characteristics
- how is impact strength affected?
Allotropic
- define
- discuss importance
- know about Fe (delta iron, gamma iron, alpha iron)
Progression of solidification
grain and grain boundaries
phase diagram
steel terminology
- rimmed -slightly deoxidized with outer shell of low impurities, surface cleanliness
- killed - strongly deoxidized, chemical additions
- galvanized - zinc-coated steel
- galvannealed - zinc-coated and heat treated steel. better paint adhesion
- sheet - 0.01-0.025 x >24 in, big and thin
- bar - rounds/squares/hexes 0.25 - 3 in
- coil - rolled steel, very thin
- flat wire - rolled rectangles made by cold-reducing rounds
- wire - coiled rounds diameter <.25 in
- shapes - hot rolled shapes, >3 in
- tin plate - steel with .005-0.014 in (may be tin coated)
- strip - rolled steel 0.01-0.025 x <24 in, less big and thin
- plate - thick, heavy steel shapes
- free machining - steels with sulfur lead or others- machine easier
- drawing quality - for satisfying elongation requirements
- merchant quality - M suffix, nonstructural applications, low quality
- commercial quality - from rimmed, capped, concast, or semikilled steel
- h steels - H suffix, guaranteed hardness in heat treatment
- b steels - small boron additions as hardening agent
- pickling - acids used to remove oxides and scale
- temper rolling - eliminates stretcher strains, improve surface finish
- temper - amount of cold reduction in rolled sheet/strip
- e steels - E prefix, melted by electric furnace
cold rolling vs hot rolling
- properties
- how
- dynamic re-crystallization
- which to choose for what
Fe-Fe3C diagram
- Pie de imagen: Pearlite, Austenite, Cementite, Ferrite
% ferrite, % pearlite
- given carbon content or approximate tensile strength
annealing
- define
- what is the condition of the material after treatment?
- how is it done
- temperatures and times
- explain how mechanical properties are affected