[MW:15709] ASME IX Code Changes of Heat Input Calculation

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"ASME IX Code Changes of Heat Input Calculation"
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ANIL BARIK
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ASME IX Code Changes of Heat Input Calculation

Readers with practical experience with Heat Input Calculations meeting ASME IX Code changes, are welcome to contribute their knowledge to this publication, for the benefit of all others who risk to get lost.

Heat Input is an essential variable only for selected applications, if the fabrication code requires impact testing. For welding ambient temperature piping/vessels, changes in heat input are not essential variables. The same applies for welding the typical power plant ferrous materials (Cr-Mo and CS [carbon steel]).

Creep strength enhanced ferritic steels and duplex stainless steels need more careful review for establishing specified ranges of heat input to meet code requirements.

The changes were introduced when it was realized that Heat Input from new power supplies, capable of pulse welding or of waveform control, cannot be represented adequately by the simple formula, called Equation 1 per ASME Section IX QW-409.1(a).

This gives Heat Input as equal to Voltage per Amperage x 60 divided by travel speed in linear distance units per minute.

Advanced manufacturers enabled their equipment to provide the required heat input information by sampling both voltage and amperage at high frequency, and by displaying either energy values or power values.

Therefore two new formulas were added to the controlling document, both giving equivalent results. The first, called Equation 2 per ASME Section IX QW-409.1(c)(1), simply gives energy in Joules divided per weld bead length.

The second called Equation 3 per ASME Section IX QW-409.1(c)(2) multiplies the Power in Joules per second (watts) per arc time in seconds, and again divides the power result in watt by weld bead length.

A draft of this paragraph can be seen online at
http://www.lincolnelectric.com/en-us/equipment/Documents/RevisedASMEcode.pdf

The 2010 edition of ASME Section IX, includes the new formulas of the variable QW 409.1, and provides instructions for calculation of heat input that takes into account waveform control, when required.

Significant differences in heat input calculations were found in practical trials, depending on the measuring methods. The new methods of monitoring heat input provide a much needed control tool for those cases where this variable is critical for assuring sound welds.

A Welding Journal article on New Code Requirements for calculating Heat Input is available online at
http://files.aws.org/wj/2010/06/wj201006/wj0610-61.pdf

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