Annealing is a way of making metal softer by heating it and then letting it cool very slowly. If metal is heated and then cooled very quickly , for example by dipping it in water , it will be very hard but also very brittle(脆)---that is , It will break easily. Metal that has been annealed is soft but does not break as easily . It is possible 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 length of time. The longer the heated metal takes to cool slowly , the softer it becomes . Annealing can also be used on other materials, such as glass.
Annealing can make metal _______________.
A.hard and tough (韧) | B.hard but brittle |
C.soft but tough | D.soft and brittle |
Why do people put hot metal in water ? ____________
A.To make it hard | B.To make it soft |
C.To make it cool | D.To make it brittle |
As suggested by the text , how can glass be made less brittle ?____________
A.It can be heated and then cooled quickly |
B.It can be cooled and then heated slowly |
C.It can be heated and then cooled slowly |
D.It can be cooled and then heated quickly |