preheat

[Kannayeram Gnanapandithan]

ASME SECTION IX, QW 406-Preheat

QW 406.1, Preheat temp should not decrease more than 100*F(55*C) and QW 406.3, Inter pass temp should not increase more than 100*F ( 55*C). What is the logic to choose temp limit 100*F( 55*) and consequences if exceed this limitations

THANKS & BEST REGARDS,

KG.PANDITHAN, IWE,  AWS-CWI, CSWIP 3.1,

CONSULTANT-WELDING & QUALITY

Mobile no: +919940739349

[George Dilintas]

 If the preheat is reduced substantially, then distortion will increase and cooling rate will increase also substantially. If cooling rate to high, especially during first pass, then lack of fusion is more probable in large thickness. In some bainitic steel  grades rapid cooling rate could lead to martensite formation.  

If interpass temperature will increase substantially then the heat input will increase substantially which could lead to grain growth etc.

The logic behind is that in case of large changes the metallurgy has to be reconsidered

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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

[Kannayeram Gnanapandithan]

what is logic to fix 55 degree Celsius, why not 30 or 45 etc 

THANKS & BEST REGARDS,

KG.PANDITHAN, IWE,  AWS-CWI, CSWIP 3.1,

CONSULTANT-WELDING & QUALITY

Mobile no: +919940739349

On Mon, Nov 14, 2016 at 1:08 AM, George Dilintas <dili...@gmail.com> wrote:

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 If the preheat is reduced substantially, then distortion will increase and cooling rate will increase also substantially. If cooling rate to high, especially during first pass, then lack of fusion is more probable in large thickness. In some bainitic steel  grades rapid cooling rate could lead to martensite formation.  

If interpass temperature will increase substantially then the heat input will increase substantially which could lead to grain growth etc.

The logic behind is that in case of large changes the metallurgy has to be reconsidered

2016-11-13 6:11 GMT+02:00 Kannayeram Gnanapandithan <kgpan...@gmail.com>:

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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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[George Dilintas]

The Code is a legal document. It is neither an engineering handbook nor a metallurgy one. The Code is using this value which is a kind of convention since we are talking about a legal documents. This convention (55 degC) is a kind of safety margin to avoid large modifications in heat flow. However, first prevails the sound engineering judgement which has to be used to tune, and not to violate the Code requirements. 

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