Manufacturing process for austenitic high manganese steel having superior formability, strengths and weldability

A process for manufacturing a high manganese austenitic steel having superior formability and strength for automotive structural applications, comprising the steps of:

• preparing a steel slab having a composition consisting essentially of in weight %:
• less than 1.5% of C, 15.0-35.0% of Mn, 0.1-3.0% of Al, less than 0.25% of Si, less than 0.2% of N, balance Fe, and other incidental impurities;
• heating said steel slab to 1100.degree.-1250.degree. C.;
• hot rolling said steel slab to form a hot rolled sheet with a hot rolling finishing temperature of 700.degree.-1000.degree. C.;
• cold rolling the hot rolled sheet to form a cold rolled sheet;
• and
• annealing the cold rolled sheet at a temperature of 500.degree.-1000.degree. C. for five seconds to 20 hours to form a grain size less than 40 .mu.m,
• whereby upon subsequent plastic deformation at room temperature said annealed sheet is free from strain induced martensite and contains deformation twins and wherein said annealed sheet has an LDR value of greater than 1.94.

A process for manufacturing a high manganese austenitic steel having superior formability and strength for automotive structural applications, comprising the steps of:

• preparing a steel slab having a composition consisting essentially of in weight %:
• less than 1.5% of C, 15.0-35.0% of Mn, 0.1-3.0% of Al, less than 0.25% of Si, less than 0.2% of N, less than 0.2% of Ti, balance Fe, and other incidental impurities;
• heating said steel slab to 1100.degree.-1250.degree. C.;
• hot rolling said steel slab to form a hot rolled sheet with a hot rolling finishing temperature of 700.degree.-1000.degree. C.;
• cold rolling the hot rolled sheet to form a cold rolled sheet;
• and
• annealing the cold rolled sheet at a temperature of 500.degree.-1000.degree. C. for five seconds to 20 hours to form a grain size less than 40 .mu.m,
• whereby upon subsequent plastic deformation at room temperature said annealed sheet is free from strain induced martensite and contains deformation twins and wherein said annealed sheet has an LDR value of greater than 1.94.