Re: [MW:24392] RE: 24355] Impact Test & cooling Rate-Preheating (carbon steel)

One more addition to Alan's good comment:

In case of lower thicknesses, the cooling rate tends to increase and may lead to martensite formation. But it is not so slow and sustained a cooling rate as to promote grain growth/reduced ductility, as you are allowed to weld between preheat & interpass temperatures.

 

BR,

Shashank C Vagal 

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From: Alan Denney <alan@denney1.freeserve.co.uk>
To: materials-welding@googlegroups.com
Sent: Tuesday, 23 February 2016 2:59 AM
Subject: [MW:24358] RE: 24355] Impact Test & cooling Rate-Preheating (carbon steel)

For structural steels and pipeline steels (carbon and carbon-manganese steels) the preheat requirement increases with combined thickness. See EN 1011:Part 2. The objective is to slow the cooling rate to prevent the formation of martensite which is hard and brittle and susceptible to hydrogen cracking.

 

Alan Denney

AKD Materials Consulting Ltd

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Mohd Siraj
Sent: 22 February 2016 09:22
To: Materials & Welding <materials-welding@googlegroups.com>
Subject: [MW:24355] Impact Test & cooling Rate-Preheating (carbon steel)

 

Dear all,

 

Background: 

impact testing is more critical for less(low)thickness than higher thickness.

 

Reason  : 

fine grain form during fast cooling and course grain form during slow cooling.

 

Question is:

Preheating use to lower the cooling rate for higher thickness.

So lower the cooling rate means form the course grain,course grain lower the toughness.

 

Preheating contributing to lower the toughness?

 

 

 

 

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