CET Carbon Equivalent Formula
The CET equivalent is a modified version of the carbon equivalent (CEV) that accounts for manganese and molybdenum with lower weighting factors. It helps determine cooling conditions and preheat temperature for modern structural steels.
Physicochemical Mechanism of Action
The CET equivalent calculates the weldability of steels by summing carbon (C), manganese (Mn), and molybdenum (Mo) with specific weighting factors. This sum indicates how the metal behaves during cooling.
Metallurgical Relevance & Welding Risks
A too high CET equivalent can lead to rapid cooling and contribute to the structure becoming glass-hard. This increases susceptibility to cracking and reduces the toughness of the steel. Conversely, a too low CET equivalent can lead to slower cooling, causing grain coarsening and thus a reduced strength level.
Workshop Practice & Action Instructions
To calculate the CET equivalent, add the following weighting factors multiplied by the corresponding element contents:
• Carbon (C): 1
• Manganese (Mn): 0.5
• Molybdenum (Mo): 0.2
Example: A steel has 0.4% carbon, 0.8% manganese, and 0.3% molybdenum.
CET = (0.4 * 1) + (0.8 * 0.5) + (0.3 * 0.2) = 0.4 + 0.4 + 0.06 = 0.86
Cooling conditions and preheat temperature should be chosen so that the CET equivalent falls within the optimal range of about 0.5 to 1.0. For a CET equivalent above 1.0, cooling should be slower to avoid cracking. For a value below 0.5, cooling should be faster to prevent grain coarsening.