Martensite formation depends also on the chemical composition and not only on the cooling rate.
The last weld bead has not a fine grain structure. It has more a dendritic structure.
Fine grain martensite will give low impact energy
Fine grain ferrite will give better impact energy.
Residual stresses also affect impact energy in a negative way.
In the mild steel the PWHT is to relief the residual stresses and not to temper the martensite.
Στις Πέμ, 25 Μαρ 2021 στις 5:13 π.μ., ο/η EmaD FaRaHanI <emad.farahani@gmail.com> έγραψε:
Dear Friends,--Consider we have a mild-steel, cooling fast from welding temperature, we must have a fine grain structure with martensite formation.Hypothetically, considering that we want to use this structure. I was wondering what is the relation between the impact energy and the structure? will it be decreased due to martensite formation? or increased due to fine grain? I understand that we don't use the martensite state of structures and we need to quench and tempering them.Thanks,Emad
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Dr. Georgios Dilintas,
Dipl. Ing. In Aeronautic and Space Engineering
Ph.D in Mechanics of Solids - Computational Mechanics
A.I.S, A.N.I, IRCA Lead Auditor
Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis
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