Given the composition of your material and some additional info, you can predict TTT and CCT diagrams. If you cool slow enough to miss the nose of the martensite start, you'll not form martensite. From my initial looks at the graph (best guess on composition), you'll need to cool VERY slowly to avoid forming martensite. This might not be possible without very high preheat temps.
http://calculations.ewi.org/vjp/secure/TTTCCTPlots.asp