This set of Foundry Questions and Answers for Experienced people focuses on “Binders used in Making Cores”.
1. ____________ is the oldest binder used in making cores.
a) Coal tar
b) Dextrin
c) Molasses
d) Vegetable oil
View Answer
Explanation: The concept of foundry emerged several years ago. As vegetable oil is considered to have several binding properties, it was used. It gained its popularity due to its wide availability and less expensive in nature.
2. Use of cores is extensively done in the casting of engine blocks.
a) True
b) False
View Answer
Explanation: The cores are normally a disposable item which gets destroyed to get it out of the component. One of the GM V-8 engines requires five dry sand cores for every casting.
3. The core when mixed with synthetic oil does not require heating.
a) True
b) False
View Answer
Explanation: The core when mixed with synthetic oil in conjunction with cereal or clay is to be baked in convention oven between 200 and 250oC so that the heat causes the binder in polymerizing. This helps the binder perform well.
4. The cores produced by the binder process called hot-box process is called _________
a) Shell core
b) Resin bond cores
c) No-bake cores
d) Dry sand cores
View Answer
Explanation: The hot-box process uses a thermoset and catalyst for a binder. The cores produced by this process are called shell cores because only the outside layer is hardened when it comes into contact with the hot core box.
5. In Cold-box process, the binder that is used to harden the core is by liquid binders.
a) True
b) False
View Answer
Explanation: In the cold-box process, the binder coated sand is allowed in the box and the special gases are passed through it to harden the sand. The gases are passed through it are at normal temperature.
6. Which of the following gases is not used in the cold-box process?
a) Amine gas
b) Sulphur-di-oxide
c) Carbon-di-oxide
d) Marsh Gas
View Answer
Explanation: Amine gas and sulphur-di-oxide gases are used at high temperatures where the core boxes are made of wood and plastic. The carbon-di-oxide gas is used as a casting core binder in sodium silicate. Marsh gas does not find any applications in the cold-box process.
7. To produce core at room temperature, special binders and air-set sands are used.
a) True
b) False
View Answer
Explanation: The air-set sands are used to produce cores at room temperature. The sands do not require the gas catalyst because the curing catalyst and organic binders are mixed together already in the sand that initiates the curing process at room temperature.
8. Baking is required for the cores produced by the shell core making method.
a) True
b) False
View Answer
Explanation: The resin used in the shell core making is allowed to melt to the specified thickness and is cured. The excess sand is dumped or removed. The hardened sand is extracted from the core. This hardened sand is good enough to perform its function and extra baking is not required.
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