Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1997-08-28
1998-09-22
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148619, C21D 713
Patent
active
058109501
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to methods for annealing and pickling a high manganese cold rolled steel sheet for use in manufacturing automobiles and electronic panels in which a superior formability and high strengths are required. In particular, the present invention relates to a method for annealing high manganese cold rolled steel sheets, in which the surface oxidation is inhibited to the minimum during a continuous annealing after a cold rolling. And also, the present invention relates to a method for pickling a high manganese cold rolled steel sheet, in which the surface oxide layer can be easily removed.
DESCRIPTION OF THE PRIOR ART
Recently, in the automobile industry, the discharge of carbon dioxide came to be regulated for preventing the aggravation of the air pollution. In this connection, in the field of the automobile steel sheets, high formability and high strength steel sheets are in demand. The automobile weight can be reduced and the combustion efficiency can be improved.
Conventionally, in view of its formability, the extremely low carbon steel, in which the matrix is ferrite, is used for the automobile steel sheets. However, in the case where an extremely low carbon steel is used as the automobile steel sheet, the formability is superior, but the tensile strength is low, down to 28-38 Kg/mm.sup.2. Therefore, not only cannot the automobile weight be reduced, but also the automobile's safety is jeopardized, thereby threatening the riders' lives.
In an attempt to solve the above problems, the present inventor disclosed the following inventions on the austenitic high manganese steel having superior formability and strengths. These are: Korean Patent Application No. 91-25112 (entitled "Austenitic High Manganese Steel Having Superior Formability and Strengths", filed on Dec. 12, 1991); Korean Patent Application No. 92-13309 (entitled "High Manganese Steel Having Superior Formability, Strengths And Weldability, And Manufacturing Method Therefor", filed on Jul. 24, 1992); and PCT Application No. PCT/KR 92/00082 (entitled "Austenitic High Manganese Steel Having Superior Formability, Strengths and Weldability, And Manufacturing Method Therefor", filed on Dec. 30, 1992).
The above mentioned high manganese steel having superior formability and strength is a steel of Fe--Mn--Al--C series, and contains large amounts of manganese and aluminum which are highly oxidable elements. Therefore, when it is annealed at a temperature of 500.degree.-1000.degree. C. under the usual atmosphere, a thick and dense oxide layer is formed on the surface of the steel sheet. If this thick and dense oxide layer is formed, it loses the commodity value as an automobile steel sheet and an electronic panel steel sheet. That is, during the manufacturing process of an automobile, if the thick and dense oxide layer is present, phosphating and painting become impossible, and therefore, it cannot be used for automobiles.
Further, if the thick and dense surface oxide layer is formed, it cannot be easily removed by pickling. Even if it is removed by using a strong chloric acid, the surface of the steel sheet becomes irregular, thereby lowering the commodity value. And also, hazard is latent in using the strong chloric acid, and a large scale pickling facility is required, thereby requiring a high facility cost.
SUMMARY OF THE INVENTION
In order to solve the problem of the formation of the thick and dense oxide layer during the manufacturing process of a high manganese steel, the present inventor carried out research and experiments, and came to propose the present invention based on the results of the research and experiments.
It is an object of the present invention to provide a method for annealing a cold rolled high manganese steel sheet. The annealing atmospheric gas is adjusted in annealing process so as to minimize the thickness of a surface oxide layer, and to make aluminum nitride into the oxide layer which is an agent for removing the oxide layer in the pickling process. The surface oxide layer
REFERENCES:
patent: 4047979 (1977-09-01), Grange et al.
patent: 5431753 (1995-07-01), Kim et al.
patent: 5634990 (1997-06-01), Choi et al.
patent: 5647922 (1997-07-01), Kim et al.
Kim Tai Woung
Kim Young Gil
Park Shin Hwa
Pohang Iron & Steel Co. Ltd.
Research Institute of Industrial Science & Technology
Sheehan John
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