  We found that transport critical current density (Jc) of the Ba1-xKxFe2As2/Ag
tapes is significantly enhanced by the combination process of cold flat rolling
and uniaxial pressing. At 4.2 K, the Jc reaches a high value of 9.1x104 A/cm2
in 4 T, which is almost the practical level of 105 A/cm2. The Jc-H curve shows
extremely small magnetic field dependence and keeps a high value of 6.9x104
A/cm2 in 10 T. These are the highest values reported so far for iron based
superconducting wires. We also show our successful attempts of the fabrication
of multi-filamentary tapes. A high Jc value of 5.3x104 A/cm2 (4.2 K, 10 T) was
obtained in seven-filamentary tapes. The hardness and microstructure
investigations reveal that the superior Jc in uniaxial pressed tape samples is
due to the high core density, more textured grains and the change of microcrack
structure. These results indicate that iron based superconductors are promising
for high magnetic field applications.
