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19 Cards in this Set
- Front
- Back
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When and why does steel undergo a brittle fracture? |
At reduced temperatures, steel becomes a brittle material, rather than a ductile one. This means that only a small amount of energy is needed to create a fast fracture, leading to a potentially catastrophic failure. This can occur in large welded structures, in low toughness steels under high tensile stress. Page 1-9 |
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Brittle fracture is common in situations where the steel is under large tensile stresses, has a low toughness and/or a high strain rate. What are some of the factors that can cause these situations to occur? |
- Low temp (reduces toughness) - thick plate and/or rigid joints (high restraint) - repeated loading (fatigue, causes cracks and stress concentrations) - residual stresses from welding and forming Page 1-12 |
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Names some types of steel: |
- Carbon-Manganese Constructional Grade - Weathering (WR Grade) Steels - Mild Steels - HSLA Steel - Quneched and Tempered Steels - Martensitic Steels - Ultra-High Strength Maraging Steels - Tool and Die steels - Water Hardening Tool Steels Page 1-16, 1-17, 1-21, 1-24, 1-27, 1-28, 1-39, 1-42, 1-45 |
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Describe the properties of a C-Mn (Carbon Manganese) Steel |
- Low carbon content - Good toughness and weldability - 350-400 MPa - Used for structural application Page 1-16 |
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Compare weathering grade steels and C-Mn Steels. |
- Addition of Copper (Cu) and Chromium (Cr) provides better atmospheric corrosion resistance - Strength is approximately the same - Does not need painting - Particularly used for exposed structural elements Page 1-17 |
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What are the three primary criterion for the selection of steels? |
- Strength - Toughness - Weldability (Assessed with carbon equivalent) Page 1-19 |
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What is the difference between High-Strength Low Alloy (HSLA) steels and C-Mn steels? |
- A higher strength (up to 500 MPa) - About the same weldability - Better mechanical properties under thermo-mechanical processing - Difference comes about because of small addition of alloying elements (Cr, Ni, Ti) Page 1-24 |
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Where are quenched and tempered (Q+T) steels used? |
- They are used when weight savings are desired, by having high hardness (300-500 BHN) or high strength (800-1000 MPa) - Have good weldability - Examples include: high performance components, military hardware and mining equipment Page 1-27 |
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Why is tempering necessary in Q+T steels? |
Tempering is necessary to increase the ductility of the steels. If not tempered, the steels will be very brittle and fracture easily. |
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What advantage does face hardening have for martensitic steels in terms of impact protection? |
The hard face does not get unduly deformed by an impact, and the more ductile steel behind the face can absorb the energy of the impact. Page 1-36 |
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Name some characteristics of martensitic steel |
- High strength and hardness - Also quite tough and fracture resistant - Harden just the surface, or the whole way through the thickness - Requires care in fabrication |
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How is face-hardened armour produced? |
Local flame heating and immediate water quenching is used to harden outer faces. Page 1-36 |
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What are ultra-high strength maraging steels about? |
- Fully martensitic with alloying elements to give age hardening properties (Mo, Ti, Cu) - Gives considerable weight savings Page 1-39 |
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How are tool and die steels hardened? |
They are heat-treated to produce superior mechanical properties (high strength, wear resistance, hardness, impact resistance, etc.) |
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Which group of steels is used for 'cold' applications? |
Water hardening steels Page 1-45 |
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Which group of steels is used for hot working applications? |
Hot Worked steels Page 1-46 |
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What makes high speed steels good for use as high-speed cutting tools? |
They don't soften as much at high temperatures and have a good wear resistance. They are heat-treated to have a high hardness, but a reduced toughness. Page 1-47 |
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Name the five types of cast iron and some of their properties |
- Gray– High C allow, low strength and ductility - White– Hard brittle alloy with massive Fe3C content - MalleableIron – heat treated white iron with increased ductility - Ductile– Similar to malleable iron except S and Mg are added to further increaseductility - Alloy –Usually with gray or white irons to improve hardness or corrosion resistance |
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How does the fracture resistance of cast irons compare with other steels? |
It is much lower. Page 1-59 |
