Method for producing cold-rolled bands or sheets

Details Method for producing cold-rolled bands or sheets Method for producing cold-rolled bands or sheets

2001-05-01

2003-06-24

Yee, Deborah (Department: 1742)

Metal treatment

Process of modifying or maintaining internal physical...

With casting or solidifying from melt

C148S603000

Reexamination Certificate

active

06582537

ABSTRACT:

The invention relates to a method for producing cold-rolled strips or sheets out of low-alloyed steels with a respective max. 0.2% of C, P, Al, Ti, V, Nb, S, B and a respective max. 1% Si and Mn, remainder iron and unavoidable impurities. After being melted, the steel is cast into slabs, thin slabs or strips, generally in a continuous casting procedure, and then hot-rolled, cold-rolled and subjected to recrystallizing annealing.
The annealing temperature level required for a complete recrystallization of the cold-rolled strip or sheet can be influenced in the preliminary stages of strip steel production. For example, it is known that the recrystallization temperature can be reduced via a high hot-strip coiling temperature and a high cold-rolling ration.
The object of the invention is to reduce the production outlay and associated manufacturing costs for generating a completely recrystallized, cold-rolled strip or sheet.
To achieve this object, the invention proposes that, in the generic procedure, the slabs or strips be hot-rolled at an initial temperature exceeding 1,100° C. and a final temperature lying under Ar
3
, the hot strip be coiled at a temperature lying below 650° C., and the cold strip then be cold-rolled at a temperature which is nearly independent of the cold rolling ratio and as low as possible ranging from 500 to 750° C. for a time sufficient to ensure complete recrystallization.
The invention is based on the surprising determination that by the use of a reduced hot-roll final temperature and a low coiling temperature a complete recrystallisation of the cold-rolled strip can be obtained at a comparatively low temperature nearly independently of the cold rolling strain. A low temperature for recrystallization annealing saves energy and costs.
In addition to the alloy contents specified above, the steels may contain 0.01% of nitrogen and the quantity of boron (>0.78×N) required for nitrogen fixation. Beyond that, slight quantities of other alloying elements that have no negative impact on the recrystallization conditions are also permissible.
If possible, the hot-roll final temperature should lie 50° C. under Ar3, and the coiling temperature should preferably range from 300 to 600° C. IF-steels with a low carbon content of up to 0.01% or steels micro-alloyed with Ti, V, Nb can be completely recrystallization annealed in a temperature range of 600 to 780° C., while non-micro-alloyed steels can be completely recrystallization annealed at even lower temperatures ranging from 500 to 680° C., largely independently of the cold rolling level.


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