Preheating is done for numerous reasons, based on the type of material and its corresponding thickness. Apart from moisture removal which is already an important task prior to welding to avoid hydrogen infusion, one of the main reasons preheating is done is to avoid having localized heat input into the metal that would eventually lead to toe cracks and other such defects. Preheating helps to prevent the sudden heat shock caused by introduction of heat (welding) into the metal by actually preparing the metal to accept the introduced heat and slowly dispersing them throughout the metal .
On Sat, Oct 9, 2010 at 11:25 AM, Hemant Wadibhasme <hemant.wadibhasme@gmail.com> wrote:
Dear all,i am workig in cross country pipeline,as per WPS the preheating temp. for carbon steel (Gr. X56, X65) is 100 degree, and in plant for carbon steel the preheating temp. is 10 degree that means there is no requirement of preheating, somebody has told me in pipeline the preheating is done only to remove the moisture on the surface of metal otherwise there is no any requirement of preheating, is it proper reason, pls share your experience.
--Thanks and Regards
Hemant F Wadibhasme
Sr. QA/QC Engineer.
Larsen and Toubro
ECC Division.Contact No. 09727083772
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