FOR INTERNAL USE ONLY
a schematic of the end-quenched bar. Four representative locations (A, B, C, D) along the bar have been related to the representative cooling curves(CCT) and isothermal transformation (TTT) curves. Thus location A on the bar experienced a fast cooling rate resulting in austenite transforming to martensite producing the high hardness indicated. Similar cooling rate effects need to be considered from a weldability viewpoint. The addition of alloying elements (for example Mo, Cr, Mn) to steel increases the hardenability by slowing down the rate of austenite transformation. The data is plotted as shown in Figure 34 for a 0.45%C steel with different alloying additions.
Figure 33
Typical End-Quench Curves for Several 0.45%C Low Alloy Steels
Several formulae have been developed which assign a contributing factor to each element addition and its effect on hardenability and conversely weldability. The maximum hardness attainable (and therefore its weldability characteristics) in carbon and low-alloy steels, however, is still almost exclusively dependent upon the carbon content.
WELDING AND COATING METALLURGY2
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