In addition to the nice explanations of Mr Herman Pieper, you may find the
attached presentation as useful on DBTT.
There is no specific rule of thumb for DBTT, a lot of factors could
influence this, e.g. composition, melting practices, heat treatment, and the
temperature of charpy impact test.One will need a set of impact test and
plot the values to find the nearest DBTT to the nearest value.
Drop weight test (DWT) typically indicates the nil ductility
temperature(NDT) for any steel under question. It's not commonly asked in
ASME Code.
Only ASME Sec-III code ,Part-NB, NC & ND have requirements of DWT so as to
correlate between DWT and charpy V-Notch testing. For all these codes this
requirement is referenced in NB/NC/ND 2320.
Applicable ASTM spec for DWT is E-208. See the brief illustration about this
test in the attachment.
Thanks.
Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net
-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of hpi001
Sent: Tuesday, August 10, 2010 2:19 PM
To: Materials & Welding
Subject: [MW:6427] Re: Ductile to Brittle Transition Temperature
DBTT is the temperature at which the fracture surface of charpy-V impact
test samples turns in to brittle and the values drop down.
For determining this temperature you need a lot of charpy specimens from the
same material or weld sample.
You first start to test single specimens at different temperatures (which
temperature depends on the material) in order to find the temperature range
where you need to execute the test and to reduce the number of specimens
needed.
For example for carbon steel you may test a specimen at 0, -40 and - 80 °C.
If the specimen at -40 °C already shows a full brittle fracture surface
without any lateral expansion, and at 0 °C the fracture surface consist both
brittle and tough parts it's sure that the DBTT lays in between these
temperatures.
From this point on you need to test sets of 3 specimens, in this case at for
example +20, +10, 0, -10, -20, -30°C. All these values you can put in a
diagram (Impact value against temperature) and will give you a curve showing
a line from 100% brittle fracture to 100% tough fracture. You will see that
you have a specific temperature where the values drop from constant high
values to constant low values.
To determine the exact DBTT you first need to specify this DBTT. Some
specifications say it should be the temperature half way between 100% tough
and 100% brittle, other specifications specify a minimum charpy value for
the DBTT.
The Drop Weight tear test is a test method similar to charpy impact testing
but at which full thickness samples will be tested against standard 10x10 mm
samples for charpy tests.
Hope this answers your question.
Best Regards,
Herman Pieper
On 10 aug, 17:21, limesh M <limes...@gmail.com> wrote:
> Dear All ,
>
> What is DBTT(Ductile to brittle transition temperature)?
>
> How we can find DBTT?
> Is there any relationship between DBTT and Drop weight tear test?
>
> Regards,
>
> Limesh
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to
materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at
http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and
meant for educational purposes only, Users must take their own decisions
w.r.t. applicable code/standard/contract documents.
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
No comments:
Post a Comment