التفاصيل البيبلوغرافية
| العنوان: |
METHOD FOR PRODUCING A SURFACE-DECARBURISED HOT-ROLLED STRIP |
| Document Number: |
20100319812 |
| تاريخ النشر: |
December 23, 2010 |
| Appl. No: |
12/673664 |
| Application Filed: |
August 07, 2008 |
| مستخلص: |
Disclosed is a method which allows steel strip to be produced in which high hardness and good formability are combined. The following steps of operation are followed. making the steel strip from the heat-treatable steel, heating the steel strip, when coiled into the open coil, to a decarburising annealing temperature which may be up to 20° C. below the Ac1 temperature of the given heat-treatable steel and which does not exceed the Ac3 temperature of the given heat-treatable steel, annealing the steel strip, in the open coil, in a decarburising atmosphere for a decarburising annealing time of at least 90 minutes, the decarburising gas which forms the decarburising atmosphere flowing through the gaps which exist between the layers of the open coil, accelerated cooling the steel strip, the depth of decarburisation, as measured from the given surface of the steel strip, being limited to a range which is less than a quarter of the thickness of the steel strip. |
| Inventors: |
Bian, Jian (Moers, DE); Grafen, Axel (Erkelenz, DE); Sabatino, Giovanni (Dinslaken, DE) |
| Assignees: |
THYSSENKRUPP STEEL EUROPE AG (Duisburg, DE) |
| Claim: |
1-15. (canceled) |
| Claim: |
16. A method for producing a surface-decarburised steel strip which is made of a heat-treatable steel containing at least 0.4% by weight of carbon, comprising the steps of: making of the steel strip from the heat-treatable steel, heating of the steel strip, when coiled into the open coil, to a decarburising annealing temperature which may be up to 20° C. below the Ac1 temperature of the given heat-treatable steel and which does not exceed the Ac3 temperature of the given heat-treatable steel, annealing of the steel strip, in the open coil, in a decarburising atmosphere for a decarburising annealing time of at least 90 minutes, the decarburising gas which forms the decarburising atmosphere flowing through the gaps which exist between the layers of the open coil, and accelerated cooling of the steel strip, the depth of decarburisation, as measured from the given surface of the steel strip, thus being limited to a range which is in each case less than a quarter of the thickness of the steel strip. |
| Claim: |
17. The method according to claim 16, wherein the coil has an increased amount of protective gas applied to it for the accelerated cooling. |
| Claim: |
18. The method according to claim 16, wherein the depth of the decarburisation is 30-120 μm. |
| Claim: |
19. The method according to claim 16, wherein the decarburising annealing time is a maximum of 120 minutes. |
| Claim: |
20. The method according to claim 16, wherein the decarburising atmosphere contains 85-97% by volume of nitrogen and 3-15% by volume of hydrogen. |
| Claim: |
21. The method according to claim 16, wherein the steel strip is heated, in the open coil, to the decarburising annealing temperature in an atmosphere of protective gas before it is exposed to the decarburising atmosphere for the decarburising annealing time. |
| Claim: |
22. The method according to claim 21, wherein the atmosphere of protective gas which is maintained during the heating contains 85-97% by volume of nitrogen and 3-15% by volume of hydrogen and in that, on the decarburising annealing temperature being reached, water vapour is fed into the atmosphere of protective gas to produce the decarburising atmosphere. |
| Claim: |
23. The method according to claim 22, wherein over the decarburising annealing time, the dew point of the decarburising atmosphere is held in the range 20-28° C. by regulating the proportion of water vapour it contains. |
| Claim: |
24. The method according to claim 16, wherein the steel strip is pickled before being wound into the open coil. |
| Claim: |
25. The method according to claim 24, wherein the steel strip is skin-pass rolled after the pickling and before being wound into the open coil. |
| Claim: |
26. The method according to claim 16, wherein the heating and decarburising annealing of the open coil are carried out in a batch type annealing furnace. |
| Claim: |
27. The method according to claim 16, wherein the decarburising annealing temperature is 680-780° C. |
| Claim: |
28. The method according to claim 16, wherein the decarburising temperature is 10-20° C. lower than the Ac1 temperature. |
| Claim: |
29. The method according to claim 16, wherein the composition of the heat-treatable steel comprises (in % by weight): C: 0.4-1.0% Si: 0.1-0.5% Mn: 0.3-1.2% P: <0.02% S: <0.008% Al: 0.01-0.05% Cr: 0.1-0.5% Ni: 0.1-0.4% Mo: ≦50.1% the remainder being iron and unavoidable impurities. |
| Claim: |
30. The method according to claim 16, wherein the following steps of operation are completed in the course of the making of the steel strip: melting of the heat-treatable steel, casting of the heat-treatable steel into a starting material such as a slab or thin slab, hot rolling of the starting material into the steel strip at a final hot-rolling temperature of 850-900° C., and reeling of the steel strip at a reeling temperature which is 600-620° C. |
| Current U.S. Class: |
148/208 |
| Current International Class: |
21; 23 |
| رقم الانضمام: |
edspap.20100319812 |
| قاعدة البيانات: |
USPTO Patent Applications |
