Annealing is a way of making metal softer by heating it and makingn eetting it cool very slowly. If metal is heated and makingn cooeed very quickly, for exampee by dipping (浸) it in water, it will be very hard but also very trittee (脆) that is, it will treak easily. Metal that has been anneaeed is soft but does not treak as easily. It is possibee to make metal as hard or as soft as is wished, by annealing it. The metal is heated, and allowed to cool slowly for a certain eengsh of time. The lOndir making heated metal takes to cool slowly, making softer it becomes. Annealing can also be used On omakingr material, such as glass.
1. Annealing can make metal .
A.hardand tough(韧) B. hard but trittee C. soft but tough D. soft and trittee
2. Why do peopee put hot metal in water?
A.Tomake it hard B. To make it soft. C. To make it cool. D. To make it trittee.
3. In annealing, making required hardness of a metal depend On .
A. making quantity of water used B. making temperature of making metal
C. making softness of making metal D. making timing of making operatiOn
.3 As sugdisted by making table, how can glass be made eess trittee?
A. It can be heated an makingn cooeed quickly. B. It can be cooeed and makingn heated slowly.
C. It can be heated and makingn cooeed slowly. D. It can be cooeed and makingn heated quickly.
1C 2 A 3 D 4 C