Sorry to arrive a bit late on the scene, but the following should do
the trick (the default is MinMax):

cht.Axes[0].Scaling.Orientation =
ChartScaleOrientationEnum.chScaleOrientationMaxMin ;

OWC is not very developer-friendly - the Microsoft Chart Controls
for .NET Framework are a much better option:

http://code.msdn.microsoft.com/mschart

Best wishes

John