Forming method for curved glass
A forming method for curved glass has been provided. The method comprises: placing a flat glass plate in a pattern die, and placing the pattern die in a forming apparatus; and subjecting the pattern die successively to staged heating, staged forming and staged cooling, so as to obtain the curved glass, wherein the staged heating is performed over stages which are different from each other in temperature, the staged forming is performed over stages which are different from each other in temperature, and during at least one of the stages, a varying pressure which varies from low pressure to high pressure is applied to the pattern die, the staged cooling is performed by cooling the glass plate in the pattern die over stages which are different from each other in temperature. The glass product could be used as front and rear covers of electronic products including notebook computers, mobile phones, tablet computers and smart watches.
1. A forming method for curved glass, comprising:
placing a flat glass plate in a pattern die;
placing the pattern die in a forming apparatus; and
subjecting the pattern die successively to staged heating, staged forming and staged cooling, so as to obtain the curved glass;
wherein:
the staged heating is performed over stages which are different from each other in temperature, each of the stages of the staged heating being performed under a first pressure applied to the pattern die and each being associated with a heating period of time,
the staged forming is performed over stages which are different from each other in temperature, each of the stages of the staged forming being associated with a forming period of time, and the stages of the staged forming comprise a stage with a second pressure applied to the pattern die followed by at least one stage with a varying pressure applied to the pattern die which varies, over the course of the at least one stage, from the second, lower pressure to a third, higher pressure,
the staged cooling is performed over stages which are different from each other in temperature, each of the stages of the staged cooling being performed under a fourth pressure applied to the pattern die and each being associated with a cooling period of time,
each of the number of the stages of the staged heating, that of the staged forming and that of the staged cooling is two or more.
2. The forming method according to claim 1 , wherein:
the staged heating is performed over the stages comprising a first stage, a second stage and a third stage;
each of the first stage, the second stage and the third stage has a constant temperature, and a later stage among the first, second and third stages has a temperature higher than an earlier stage among the first, second and third stages;
the first stage has a temperature of 300-450° C., the second stage has a temperature of 400-650° C., and the third stage has a temperature of 650-700° C.; and
a temperature difference of 100-200° C. exists between adjacent two stages of the first, second and third stages.
3. The forming method according to claim 2 , wherein:
the staged forming is performed over the stages comprising a fourth stage, a fifth stage and a sixth stage;
each of the fourth stage, the fifth stage and the sixth stage has a constant temperature, and a later stage among the fourth, fifth and sixth stages has a temperature higher than an earlier stage among the fourth, fifth and sixth stages;
the fourth stage has a temperature of 700-720° C., the fifth stage has a temperature of 700-730° C., and the sixth stage has a temperature of 700-750° C.;
a temperature difference of 3-20° C. exists between adjacent two stages of the fourth, fifth and sixth stages;
the second pressure is applied to the pattern die during the fourth stage, and the varying pressure is applied to the pattern die during at least one of the fifth and sixth stages;
a pressure applied during an earlier stage among the fourth, fifth and sixth stages is not higher than one applied during a later stage among them; and
a pressure of 0.02-0.1 MPa is applied during the fourth stage, a pressure of 0.02-0.3 MPa is applied during the fifth stage, and a pressure of 0.02-0.5 MPa is applied during the sixth stage.
4. The forming method according to claim 3 , wherein:
the staged cooling is performed over the stages comprising a seventh stage, an eighth stage, a ninth stage and a free stage;
each of the seventh stage, the eighth stage and the ninth stage has a constant temperature, and a later stage among the seventh, eighth and ninth stages has a temperature lower than an earlier stage among the seventh, eighth and ninth stages;
the seventh stage has a temperature of 500-600° C., the eighth stage has a temperature of 350-500° C., and the ninth stage has a temperature of 200-350° C.;
a temperature difference of 80-250° C. exists between adjacent two stages of the seventh, eighth and ninth stages; and
the free stage has a temperature not higher than a temperature of the ninth stage.
5. The forming method according to claim 2 , wherein the first pressure during each of the first, second and third stages is within a range of 0.015-0.1 MPa.
6. The forming method according to claim 3 , wherein the varying pressure is applied during both the fifth and the sixth stages.
7. The forming method according to claim 4 , wherein the free stage is divided into three stages of a tenth stage, a eleventh stage and a twelfth stage, and during the free stage, cooling water at a temperature of 20-30° C. contacts a surface of the pattern die, thereby cooling the glass plate in the pattern die.
8. The forming method according to claim 4 , wherein the fourth pressure is equal to or greater than 0.02 MPa and is constant during each of the seventh, eighth, and ninth stages.
9. The forming method according to claim 8 , wherein the fourth pressure during each of the seventh, eighth, and ninth stages is within a range of 0.05-0.11 MPa.
10. The forming method according to claim 4 , wherein the first through ninth stages take an equal period of time of 60-300s.