Impact Test & cooling Rate-Preheating (carbon steel)

[Mohd Siraj]

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?

 

[Kannayeram Gnanapandithan]

When plate/Sheet are manufactured in mills, there will be fast cooling rate in lesser thickness compared to heavier thickness. But in welding, it is  reverse

--
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To post to this group, send email to material...@googlegroups.com.
Visit this group at https://groups.google.com/group/materials-welding.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/3247d39d-f53a-4bc4-aee8-79f73a1d95d8%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Alan Denney]

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

--

You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To post to this group, send email to material...@googlegroups.com.
Visit this group at https://groups.google.com/group/materials-welding.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/3247d39d-f53a-4bc4-aee8-79f73a1d95d8%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

This email has been scanned by BullGuard antivirus protection.

For more info visit www.bullguard.com

[Shashank Vagal]

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 

---

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

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/003801d16db8%2430d2dab0%2492789010%24%40denney1.freeserve.co.uk.

[Ramin Kondori]

When dealing with thick sections of fine grain structural steels, the welding engineer shall consider that although low cooling rate is favorable for impact toughness (especially HAZ toughness) but preheat is also required to reduce the residual stress as a result of high volume of the weld metal and reduce the risk of cracking especially on fist layers.

On one hand, a minimum preheat temperature is required (especially for fist layers) to prevent cracking and on the other hand, the heat input and interpass temperature shall be kept under a certain level to ensure coarse grain structure will not form (especially at HAZ).

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/613526275.231430.1456591879950.JavaMail.yahoo%40mail.yahoo.com.

[Kannayeram Gnanapandithan]

in welding, lower thickness will have slow cooling  when compared to higher thickness weld which will have fast cooling rate, that is why to slowdown , preheat is applied to avoid hard structure which inferior for toughness properties

THANKS & BEST REGARDS,

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

CONSULTANT-WELDING & QUALITY

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/613526275.231430.1456591879950.JavaMail.yahoo%40mail.yahoo.com.