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The correct reasons for the occurrence of hot tear in casting among the following reasons will be:
i. Hindered contraction occurring immediately after metal has solidified
ii. Poor collapsibility of mould and core
iii. Too high pouring temperature
- a)i and ii only
- b)i and iii only
- c)ii and iii only
- d)i, ii and iii
Correct answer is option 'D'. Can you explain this answer?
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The correct reasons for the occurrence of hot tear in casting among t...
The correct reasons for the occurrence of hot tear in casting are i) Hindered contraction occurring immediately after the metal has solidified, ii) Poor collapsibility of the mold and core, and iii) Too high pouring temperature.
1. Hindered contraction occurring immediately after the metal has solidified:
Hot tear in casting can occur due to the hindered contraction that takes place when the metal starts to solidify. As the metal cools and solidifies, it undergoes a volumetric contraction. However, if this contraction is hindered by the surrounding mold and core, it can lead to internal stresses within the casting. These internal stresses can cause the casting to crack or tear, resulting in hot tears.
2. Poor collapsibility of the mold and core:
Another reason for hot tear in casting is the poor collapsibility of the mold and core. Collapsibility refers to the ability of the mold and core to shrink and move away from the solidifying metal as it undergoes contraction. If the mold and core do not have sufficient collapsibility, they can restrict the contraction of the metal, leading to the development of internal stresses and subsequent hot tear.
3. Too high pouring temperature:
Pouring temperature plays a crucial role in the formation of hot tears. If the pouring temperature of the molten metal is too high, it can result in excessive thermal expansion of the metal during solidification. This increased thermal expansion can cause the metal to exert high forces on the surrounding mold and core, leading to the occurrence of hot tear.
In summary, hot tear in casting occurs due to hindered contraction occurring immediately after the metal has solidified, poor collapsibility of the mold and core, and too high pouring temperature. These factors contribute to the development of internal stresses within the casting, leading to cracking or tearing. Therefore, it is important to control these factors during the casting process to minimize the occurrence of hot tear and ensure the production of defect-free castings.
1. Hindered contraction occurring immediately after the metal has solidified:
Hot tear in casting can occur due to the hindered contraction that takes place when the metal starts to solidify. As the metal cools and solidifies, it undergoes a volumetric contraction. However, if this contraction is hindered by the surrounding mold and core, it can lead to internal stresses within the casting. These internal stresses can cause the casting to crack or tear, resulting in hot tears.
2. Poor collapsibility of the mold and core:
Another reason for hot tear in casting is the poor collapsibility of the mold and core. Collapsibility refers to the ability of the mold and core to shrink and move away from the solidifying metal as it undergoes contraction. If the mold and core do not have sufficient collapsibility, they can restrict the contraction of the metal, leading to the development of internal stresses and subsequent hot tear.
3. Too high pouring temperature:
Pouring temperature plays a crucial role in the formation of hot tears. If the pouring temperature of the molten metal is too high, it can result in excessive thermal expansion of the metal during solidification. This increased thermal expansion can cause the metal to exert high forces on the surrounding mold and core, leading to the occurrence of hot tear.
In summary, hot tear in casting occurs due to hindered contraction occurring immediately after the metal has solidified, poor collapsibility of the mold and core, and too high pouring temperature. These factors contribute to the development of internal stresses within the casting, leading to cracking or tearing. Therefore, it is important to control these factors during the casting process to minimize the occurrence of hot tear and ensure the production of defect-free castings.
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The correct reasons for the occurrence of hot tear in casting among t...
The correct reasons for the occurrence of hot tear in casting are:
i. Hindered contraction occurring immediately after the metal has solidified:
- When the metal solidifies, it undergoes thermal contraction. However, if there are restrictions in the mold or core, the contraction is hindered, leading to the development of internal stresses in the casting.
- These internal stresses can cause the casting to crack or tear during the cooling and solidification process.
- Hot tear defects are more likely to occur in areas where the metal is thickest, as the contraction is more pronounced in these regions.
ii. Poor collapsibility of the mold and core:
- Collapsibility refers to the ability of the mold and core to collapse or shrink away from the casting as it cools and solidifies.
- If the mold or core has poor collapsibility, it will not shrink away from the casting properly, leading to the development of internal stresses and potential hot tear defects.
- Poor collapsibility can be caused by factors such as improper design of the mold or core, inadequate venting, or insufficient mold or core material.
iii. Too high pouring temperature:
- Pouring temperature refers to the temperature at which the molten metal is poured into the mold.
- If the pouring temperature is too high, it can result in excessive thermal gradients and differential cooling within the casting, leading to the development of internal stresses and hot tear defects.
- High pouring temperatures can also cause the metal to solidify too quickly, reducing its ability to deform and accommodate the thermal contraction, further increasing the likelihood of hot tear formation.
In summary, the occurrence of hot tear defects in casting can be attributed to hindered contraction occurring immediately after metal solidification, poor collapsibility of the mold and core, and too high pouring temperature. These factors contribute to the development of internal stresses in the casting, which can lead to cracking or tearing during the cooling and solidification process.
i. Hindered contraction occurring immediately after the metal has solidified:
- When the metal solidifies, it undergoes thermal contraction. However, if there are restrictions in the mold or core, the contraction is hindered, leading to the development of internal stresses in the casting.
- These internal stresses can cause the casting to crack or tear during the cooling and solidification process.
- Hot tear defects are more likely to occur in areas where the metal is thickest, as the contraction is more pronounced in these regions.
ii. Poor collapsibility of the mold and core:
- Collapsibility refers to the ability of the mold and core to collapse or shrink away from the casting as it cools and solidifies.
- If the mold or core has poor collapsibility, it will not shrink away from the casting properly, leading to the development of internal stresses and potential hot tear defects.
- Poor collapsibility can be caused by factors such as improper design of the mold or core, inadequate venting, or insufficient mold or core material.
iii. Too high pouring temperature:
- Pouring temperature refers to the temperature at which the molten metal is poured into the mold.
- If the pouring temperature is too high, it can result in excessive thermal gradients and differential cooling within the casting, leading to the development of internal stresses and hot tear defects.
- High pouring temperatures can also cause the metal to solidify too quickly, reducing its ability to deform and accommodate the thermal contraction, further increasing the likelihood of hot tear formation.
In summary, the occurrence of hot tear defects in casting can be attributed to hindered contraction occurring immediately after metal solidification, poor collapsibility of the mold and core, and too high pouring temperature. These factors contribute to the development of internal stresses in the casting, which can lead to cracking or tearing during the cooling and solidification process.
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The correct reasons for the occurrence of hot tear in casting among the following reasons will be:i. Hindered contraction occurring immediately after metal has solidifiedii. Poor collapsibility of mould and coreiii. Too high pouring temperaturea) i and ii onlyb) i and iii onlyc) ii and iii onlyd) i, ii and iiiCorrect answer is option 'D'. Can you explain this answer?
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