Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Materials > Steels > Flashcards

Steels Flashcards

1
Q

What characteristics do water-hardened tool steels have?

A

High tensile strength & hardness, low ductility and toughness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What percentage carbon and alloying elements do water-hardened tool steels have?

A

0.85 - 0.95%C, Vanadium, Chromium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the typical heat treatment process of water-hardened steels?

A

Preheating an annealed tool, typically at 670°C
Austenitizing (soaking at high heat)
Quenching (create hard brittle (martensite) condition
Tempering or Annealing (draw to desired hardness)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are hypereutectoid steels? Why are they difficult to machine?

A

Hypereutectoid steels are steels with carbon content >0.76wt%C
Due to a brittle network of pearlite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is spheroidization annealing? What does it do? What are the aims?

A

Heating, soaking and cooling (very slowly)
Breaks up hypereutectoid steel: the pearlite and cementite network
- minimise hardness
- maximise ductility, machineablility and softness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the purpose of chromium in water hardened tool steels? What are the benefits?

A

Cr inhibits pearlite formation
Increases hardness and hardenability (the ability of the material to form martensite)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the purpose of vanadium in water hardened tool steels? What are the benefits

A

Vanadium inhibits grain growth when austenitizing. Works by forming V4C3 and pinning grain boundaries.
Increases hardness and improves wear resistance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are applications of water hardened tool steels?

A
  • Hammers
  • Forging Dies, Cutting Dies
  • Blanking and boring tools
  • Chisels, scissors, knife blades
  • Watch making tools
  • Engraving tools
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are some characteristics of shock-resisting tool steels?

A
  • High impact resistance
  • Excellent toughness
  • Good wear resistance
  • High hardenability and softening resistance
    Toughness (most important)
    Hardness (second most)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the definition of toughness?

A

The ability of a material to withstand a suddenly applied load.
The energy absorbed by a material before failure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the carbon content and main alloys of shock-resisting tool steels?

A

0.5%C, Chromium, Molybdenum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the typical heat treatment process for S7 shock-resistant tool steel?

A
  • Annealing (heat slow and uniform to 815-845°C, furnace cool to 510°C at a rate of 8-15°C/hr)
  • Stress relieving (warm to 650°C, furnace cool)
  • Hardening (pre-heat 650 - 700°C, austenitize: heat 925°C - 960°C)
  • Quench (by oil)
  • Temper (150-200°C, holding 30 mins/25mm)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does tempering do? How does it work?

A

Increases ductility but reduces strength.
Works by inducing recrystallisation, making crystals more equiaxed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are some applications of shock-resisting tool steels?

A
  • Chisels
  • Punches
  • Shear blades
  • Driver bits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What contributes to the shock resistance of shock-resistant tool steels?

A
  • Toughness then hardness are most important factors
  • A lower carbon content than other tool steels is used to improve impact strength.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What contributes to S7 (shock-resistant) increased hardenability?

A

1.8wt% Mo and 6.5wt% Cr
Oil quenching

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are general characteristics of cold-worked tool steels?

A
  • High abrasion and wear resistance
  • High toughness
  • High impact resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the 3-grades of cold-worked tool steels?

A
  • Oil hardening steels [O]
  • Air hardening steels [A]
  • High carbon, high chromium steels [D]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are some characteristics of oil-hardening steels?

A
  • Hardened by oil quenching
  • Contain high carbon with manganese, chromium and molybdenum
  • High as-quenched hardness
  • Low red hardness
  • High hardenability, resist cracking on quenching
20
Q

What is a popular cold-worked oil- hardening steel?

A

O1 (0.5wt%Cr, 0.5wt% W)
Can’t be used for hot working, restarts tempering

21
Q

What are applications of air-hardening steels?

A

Applications where high toughness and fair wear resistance are required:
- Blanking
- Forming dies
- Knives
- Coining dies

22
Q

What elements compose air-hardening steels? What are important alloys?

A

1.0-2.0wt%C, Cr, Mn, Mo, V, Ni
A2 and A4 are important alloys

23
Q

What are properties of high carbon, high chromium steels? What are the applications?

A

Properties:
- Excellent wear resistance
- Non-deforming properties
- Good oxidation resistance (Cr)
Applications:
Blanking and piercing dies, coining dies.

24
Q

What are some characteristics of hot-worked tool steels

A
  • 0.3-0.5wt%C
  • High temperature (200-800°C) metal forming operations
  • Resistance to deformation at hot working temperatures
  • Resistance to mechanical and thermal shock (low wt%C)
  • Wear and erosion resistant
25
Q

What are the 3 groups of hot-worked tool steels?

A

Chromium based [H11 - H19]
Tungsten based [H20 - H26]
Molybdenum based [H41 - H43]

26
Q

What is secondary hardening?

A

It is the introduction of Mo and W into the grain structure to produce M-carbides which reduce the softening in an alloy at high temperatures.
Without these elements, diffusion of Fe-carbides occur readily causing softening.

27
Q

What is happening during secondary hardening?

A
  • Cementite (Fe3C) forms as carbon diffuses out of the martensite.
  • The microstructure of the matrix coursens (strength and hardness fall)
  • If the cementite can be replaced by a more stable carbide e.g. Mo or W, softening is greatly reduced

-IF sufficient amounts of these alloying elements are present from 500-600°C, secondary hardening occurs.

28
Q

What are some characteristics of high speed tool steels?

A
  • Resistance to softening in red heat (high red hardness)
  • Wear resistance
  • High hardness
  • Edge retention
29
Q

What are the two groups of high speed steels (HSS)?

A
  • Molybdenum high speed steel [M]
  • Tungsten high speed steel [T]
30
Q

What are the purpose of each alloy in high speed steels (HSS)?

A
  • W and Mo provide carbide formation and secondary hardness.
  • V provides increased abrasion resistance, reduced oxidation, increased hardness.
  • Co provides high temperature hardening.
31
Q

List in order of heat extraction rate air, water or oil quenching?

A
  • Air: 2.5-25 W/m2K
  • Oil: 20-500 W/m2K
  • Water: 100-15,000 W/m2K
32
Q

What is the benefit of high Cr and C in cold worked steels?

A

Oxidation resistance due to Cr

33
Q

What is the application of HSS

A

Mill cutters operating at high speeds

34
Q

What contributes to HSS materials hardness?

A

W and or Mo provide carbide formation and red hardness/secondary hardness
- V provides abrasion resistance, reduced oxidation and increased hardness.
- Co provides high temperature hardening.

35
Q

In Taylor’s tool life equation vT^n=C, what are the units of C?

A

m/min

36
Q

What is sintering?

A

Sintering is the process of forming a solid mass of material through heat and pressure without melting the material. Usually done with powdered metal.

37
Q

What are cermets?

A

Combinations of TiC, TiN, TiCN, with nickel or molybdenum as binders

38
Q

What are applications of cermets?

A

High speed finishing of steels, stainless steels and cast irons.
- higher speeds and lower feeds than steel cutting cemented carbide grades
- better finish achieved, often eliminating need for grinding

39
Q

How is sintered polycrystalline diamond (SPD) fabricated?

A

By sintering fine grained diamond crystals under high temperatures and pressures into desired shape with little or no binder

40
Q

What are applications of sintered polycrystalline diamond (SPD)?

A

High speed machining of non-ferrous metals and abrasive non-metals such as fiberglass reinforced polymer, graphite and wood

41
Q

What is the hardest material known next to diamond?

A

Cubic boron nitride (cBN)

42
Q

What are applications of cubic Boron Nitride?

A

Machining steel and nickel-based alloys

43
Q

What are applications of cemented carbide?

A

Used in lathes,
milling machines of cast iron, non ferrous alloy and non metallic materials

44
Q

What are general properties of cemented carbides?

A
  • High compressive strength
  • Low to moderate tensile strength (brittle)
  • High hardness (90 - 95 HRA)
  • Good hot hardness
  • Good wear resistance
  • High thermal conductivity
  • High elastic modulus 600GPA
  • Toughness lower than HSS
45
Q

What are coated carbides?

A

Cemented carbide insert coated with one or more layers of TiC, TiN and or Al2O3 or other hard materials

46
Q

What is chemical vapour disposition? (CVD)

A

CVD coated carbides make up 70% of all coated WC-Co tools.
They offer high thermal stability, high adhesion (wear resistance) and ability for multi layer coating.

Materials (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions