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CWI Textbook Chapters > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

Metal Structures can combine to form what 3 forms and are referred to as atoms

A

Solid
Liquid
Gas

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2
Q

Increase in temperature in metal will cause atoms to?

A

vibrations of the atoms continue to increase causing the spacing to increase and the metal to expend. once the interatomic spacing is so great the atoms are no long attached enough to form a specific structure and become liquid

Further heating would eventually turn the liquid into a gas (vapor point)

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3
Q

Decrease in temperature in metal will cause atoms to?

A

move closer together in turn causing the metal to contract

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4
Q

What is the internal energy and interatomic spacing
Solid Metal?
Liquid Metal?
Gas?

A

Solid Metal
- Lowest internal energy and shortest interatomic spacing
Liquid Metal
-Higher internal energy and greater interatomic spacing
Gas
- Considered Unstructured - Highest internal energy and greatest interatomic spacing

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5
Q

When a metal solidifies it always does so in a

A metal solidifies in to a(an) _________ by a process know as?

A

crystalline pattern

Nucleation & Growth

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6
Q

The smallest number of atoms that can complete describe their orderly arrangement is referred to as a?

A

Unit cell

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7
Q

The most common crystal structures or phases in metals are…

A

BCC - Body-centered cubic
FCC - Face-centered cubic
HCP - Hexagonal close packed

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8
Q

BCC?

Which metals?

A

Body-centered cubic

Iron, Carbon steel, Chromium, Molybdenum & Tungsten

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9
Q

FCC

Which metals?

A

Face-centered cubic

Aluminum, copper, nickel & austenitic

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10
Q

HCP

Which metals?

A

Hexagonal close packed

Titanium, Zinc, Cadmium, Beryllium, & Magnesium

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11
Q

Allotropic

A

A metal crystal possessing different structures but the same chemical composition

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12
Q

Mechanical properties can be dependent upon…?

A

The GRAIN size of the Materials

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13
Q

Fine-grained materials are preferred for what type of temurature

Because?

A

Room and low temperature services

They generally exhibit better ductility, notch toughness and fatigue properties.

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14
Q

Coarse-grained materials are preferred for what type of temperature

A

Higher Temperatures

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15
Q

Metals are___________ __________ formed by atoms in an ________ _________ . This arrangement is know as a ________ and is described as a ______ ____

A

Crystalline structures
ordered patterns
phases
unit cell

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16
Q

The junction between individual grains are referred to as a

A

Grain boundary

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17
Q

The grain size will dictate?

A

The amount if grain boundary are present

& determines to a certain degree the mechanical properties of the metal.

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18
Q

Smaller atoms such as carbon, nitrogen and hydrogen tend to occupy sites Between the atoms that form the lattice structure of the base metal

A

interstitial allowing

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19
Q

Allowing elements with atoms close to the size of those of the bas metal tend to occupy __________ sites know as

A

substitutional alloying

20
Q

Types of smaller Atoms metals

A

carbon, nitrogen and hydrogen

21
Q

Types of larger Atoms metals

A

copper in nickel

and nickel in copper

22
Q

Heat treatments

A

annealing, normalizing, quenching, tempering, preheating, and thermal stress relieving

23
Q

Annealing def?
Properties?
How?

A

Heat treatment - softening treatment used to increase the metals ductility at ht expense of its strength.

Metal is raised to the austenitic range and held, them cooled very slowly in a furnace, the to room temperature

24
Q

Normalizing def?
How?
Properties?
Weldable?

A

Heat treatment - softens metal, not as significantly as annealing. Considered “homogenizing’ heat treatment. makes metal uniform throughout its cross section

Heated up and slow cooled in still air

Harder. stronger metal with better ductility than annealing

Easily weldable

25
Q

Quenching
How?
Properties?
Weldable?

A

Heat treatment - Raising metal demo to austenite range, holding then rapidly coming to room temp by submerging it in quenching medium (water, oil, salt water (brine))

Increased hardens and strength and decreased ductility

26
Q

Tempering

A

a heat treatment which reduces the strength and hardness of as-quenched steels and restores ductility and toughness

  • reheating quenched material below transformation temp 1333F
27
Q

Preheating

A
  • used to slow down cool rate of the base metal
  • improves ductility without significantly degrading the metals strength. temp not as high as post heat treatments

additional preheat required if there in an increase in carbon equivalent

28
Q

Post heating

A
  • used to reduce residual stresses and to temper hard, brittle phases formed during cooling or quenching
  • temp higher then pre heat treatments
29
Q

stress relieving

A

a heat treatment which relieves a metal’s residual stress by heating, holding at temp. and cooling per a prescribed cycle.

Thermally, or mechanically

30
Q

lamellar

A

Layered, or plate like

31
Q

diffusion

A

moment of atoms within a solution (solid, liquid or gas )

32
Q

Peening

A
  • Severe mechanical deformation of a metal.
  • Also a mechanical treatment
  • use of a heavy hammer to flatten the face of the weld which reduces residual stresses of the weld.
  • not used on root pass or final layer
33
Q

Thermal stress relief

A

a large area of the weed zone is heated uniformly and held fora period of time. bELLOW LOWER TRANSFORMATION TEMP 1333deg F then uniformly cooled to room temp.
eliminates distortion

strength reduced while temp is increased

34
Q

Vibratory treatment stress relief

A

a sound wave is introduced during or after welding to prevent build up of stresses

35
Q

Diffusion

A

Changes of atoms in the solid state

gold and lead example) also (solid solubility

36
Q

Solubility

A

As the temp increases the more the metals can mix together

37
Q

Hydrogen cracking is oft referred to as

A

underbead or delayed cracking

38
Q

Hydrogen in welding

A
  • try to eliminate hydrogen when welding
  • clean surface
  • use low hydrogen rods should be kept dry and care taken after seal of package has been broken.
  • hydrogen will diffuse out of most metals at temp of 200-450F
39
Q

Pack carburizing

A

Heating metal up with carbon below their melting point to allow diffusion to occur and give the base metal additional properties. makes the steel harder

Steal is packed into carbon particles and heated some carbon will dissolve and diffuse in the surface of the steel

40
Q

Nitriding

A

Process whereby nitrogen is dissolved into the surface of carbon steel.

hardening technique using ammonia instead of carbon to use diffusion. ammonia and steal are heated up and then the ammonia breaks down and the nitrogen atom enter the steel surface.

41
Q

Stainless steal

5 classes of SS

A
  • Classified as having a least 12% chromium
  • Ferritic - Weldable with proper filler
  • martensitic - most difficult to weld. (need post/pre heat)
  • austenitic - Weldable with proper filler
  • (PH) precipitation hardening - weldable
  • duplex grades - weldable
42
Q

duplex grades

A

stainless steel - half ferrite & half austenite at room temp.
- improved resistance to chloride stress corrosion cracking

43
Q

Sensitization

A

When heating to welding temp chromium and carbon present in the metal combine (@1250F) resulting in corrosion dues to less resistance qualities

44
Q

Pearlite

A

Steel is heated into austenitic range, the resulting microstructures will contain pearlite
- generally very soft and ductile.

45
Q

Heat input formula

A

Heat input =

                   welding current X Welding Voltage X 60
                    \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
                              welding travel speed (in/min)
46
Q

Cementite

A

Rapid quenching of a steel from the austenitic range results in a hard, brittle structure

CWI Textbook Chapters (10 decks)

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