The ornamental design for a tiechain, as shown and described.
FIG. 1 is a perspective view of a tie chain showing my new design;
FIG. 2 is a plan view thereof;
FIG. 3 is a top elevational view thereof, taken in the direction of arrow 3 in FIG. 6;
FIG. 4 is a bottom elevational view thereof, taken in the direction of arrow 4 in FIG. 6;
FIG. 5 is a side elevational view thereof, taken in the direction of arrow 5 in FIG. 6, it being understood that the opposite side is a mirror image thereof;
FIG. 6 is included to provide directional arrows to aid in better understanding the various drawing views; and,
FIG. 7 is an enlarged view taken in the area enclosed by the dotted circle indicated by Arrow 7 in FIG. 6 to better show detail of the design.