Method for the heat treatment of a steel reinforcement element for tires
The method for the heat treatment of a steel reinforcing element (F) for a tire comprises a transformation of the steel microstructure and in which the temperature of the reinforcing element (F) is reduced during the transformation of the steel microstructure by simultaneously extracting heat from the reinforcing element (F) and supplying heat to the reinforcing element (F).
1. A method for the heat treatment of a steel reinforcing element for a tire, comprising:
transforming the steel microstructure, said transforming comprising a step of:
reducing a temperature of the reinforcing element during the transformation of the steel microstructure in a cooling device having a heat extractor, the heat extractor having an inlet ( 40 ) at an entry end of the heat extractor, and an outlet ( 42 ) located at an exit end of the heat extractor, the cooling device further having two electrically conductive terminals ( 36 , 38 ), respectively positioned upstream and downstream of the inlet ( 40 ) and the outlet ( 42 ), by:
extracting heat from the reinforcing element within the cooling device by the heat extractor arranged within the cooling device while simultaneously supplying heat to the reinforcing element within the cooling device by application of Joule effect heating to the reinforcing element between the two electrically conductive terminals ( 36 , 38 ).
2. The method according to claim 1 , wherein the heat is extracted from the reinforcing element within the cooling device by thermal convection in contact with at least one cold source.
3. The method according to claim 2 , wherein the heat is extracted from the reinforcing element within the cooling device by:
a run chamber containing an intermediate cold source arranged between the reinforcing element and an external cold source, and
a chamber for circulation of the external cold source arranged around the run chamber of the reinforcing element.
4. The method according to claim 1 , wherein each of the two electrically conductive terminals comprises an electrically conductive rotatable pulley.
5. The method according to claim 1 , wherein the reinforcing element has a mean run speed greater than 40 m·min −1 .
6. The method according to claim 1 , comprising moving the reinforcing element at a mean run speed greater than 90 m·min −1 while reducing the temperature of the reinforcing element.
7. The method according to claim 1 , comprising moving the reinforcing element at a mean run speed greater than or equal to 200 m·min −1 while reducing the temperature of the reinforcing element.
8. The method according to claim 1 , comprising moving the reinforcing element at a mean run speed greater than or equal to 300 m·min −1 while reducing the temperature of the reinforcing element.
9. The method according to claim 1 , wherein the mean rate of temperature reduction during the transformation of the microstructure of the steel is greater than or equal to 30° C.s −1 .
10. The method according to claim 1 , wherein the mean rate of temperature reduction during the transformation of the microstructure of the steel is greater than or equal to 50° C.s −1 .
11. The method according to claim 1 , wherein the mean rate of temperature reduction during the transformation of the microstructure of the steel is greater than or equal to 70° C.s −1 .
12. The method according to claim 1 , wherein the mean rate of temperature reduction during the transformation of the microstructure of the steel is less than or equal to 110° C.s −1 .
13. The method according to claim 1 , wherein the temperature is reduced by more than 30° C. during the transformation of the steel microstructure.
14. The method according to claim 1 , wherein the temperature is reduced by more than 50° C. during the transformation of the steel microstructure.
15. The method according to claim 1 , wherein the temperature is reduced by more than 75° C. during the transformation of the steel microstructure.
16. The method according to claim 1 , wherein the temperature is reduced by more than 100° C. during the transformation of the steel microstructure.
17. The method according to claim 1 , wherein the transformation of the steel microstructure takes place in a temperature range from 800° C. to 400° C.
18. The method according to claim 1 , wherein the transformation of the steel microstructure takes place in a temperature range from 750° C. to 500° C.
19. The method according to claim 1 , wherein the transformation of the steel microstructure takes place in a temperature range from 650° C. to 550° C.
20. The method according to claim 3 , wherein the intermediate cold source comprises a heat exchange gas.
21. The method according to claim 20 , wherein the heat exchange gas comprises a gas selected from reducing gases, inert gases and mixtures of these gases.
22. The method according to claim 3 , wherein the external cold source comprises a heat exchange liquid.