摘要:
Methods for annealing and pickling high manganese cold rolled steel sheets for use in automobiles and electronic panels in which a superior formability and high strengths are required are disclosed. That is, the invention provides a method for annealing a cold rolled high manganese steel sheet, in which, after cold-rolling a high manganese steel of Fe--Mn--Al--C series, the annealing atmospheric gas is adjusted during an annealing so as to minimize the thickness of a surface oxide layer, and an oxide layer removing agent such as aluminum nitride is spread into the oxide layer, so that the surface oxide layer can be easily removed. The invention further provides a method for pickling a cold rolled high manganese steel sheet, in which the surface oxide layer formed on the cold rolled high manganese steel sheet is uniformly removed with a mild aqueous solution of chloric acid, thereby improving the surface quality of the steel sheet, and saving the pickling facility cost. When the high manganese steel sheet is annealing at a temperature of 500.degree.-1000.degree. C., the annealing atmosphere consists of 100% of nitrogen or 50% or more of nitrogen and a balance of hydrogen. The high manganese steel sheet is pickled for 30-90 seconds within an aqueous solution of chloric acid having an acid concentration of 0.06-0.8 weight % and a temperature of 15.degree.-50.degree. C.
摘要:
A high manganese steel having superior hot workability is disclosed, in which small amounts of the alloying elements are added into a high manganese steel of Fe-Mn-Al-C system, so that the rupture strength of the grain boundaries of columnar crystals can be improved, thereby realizing an improved hot workability. Further, a process for manufacturing a high manganese hot rolled steel sheet is disclosed, in which the above mentioned high manganese steel is subjected to be controlled the initial hot rolling conditions during a hot rolling, so that large cracks would not be generated on the edges and on the surface of the hot rolled steel sheet. The process for manufacturing a hot rolled high manganese steel without any cracks includes the following the steps. That is, the process includes the steps of: preparing the ingot or the continuous casting slabs of the conventional Fe-Mn-Al-C steel with one or more elements selected from a group consisting of 0.0005-0.04% of B, 0.0005-0.050% of Ti, 0.0005-0.050% of Zr, 0.0005-0.040% of La, 0.0005-0.040% of Ce, and 0.0005-0.030% of Ca; heating the ingot or the continuous casting slab to a temperature range of 1150.degree.-1300.degree. C.; carrying out a hot rolling by applying a low reduction ratio below 7% per pass and an average strain rate below 2.0 sec.sup.-1 per pass, until a total reduction ratio reaches 40%; and carrying out a hot rolling by the high reduction ratio after reaching the total reduction ratio of 40%.