From: Ramin Kondori <raminkondori@gmail.com>
Sent: Tue, 26 Jul 2011 07:44:45
To: materials-welding@googlegroups.com
Subject: Re: [MW:11898] CVN Energy
Dear Harish:
It's pure statistics.
Metallurgists have studied toughness of alloys by conducting impact tests.
Impact energy-Temperature diagrams has been obtained.
in cases like carbon steels (and common engineering applications), they have observed that if impact energy is more than 27J then the fracture will not be so called "brittle" ...
This means that even after reaching the "ultimate strtength" the material doesn't suddenly colapse but rather it will continue to absorb more energy and then fails...
This has a lot of advantages... you know what...!!!
In some cases thet design engineers feel that they need a more energy absorbtion before fracture, they specify higher values like 47J.
27J impact tougness is one of "those" numbers that are important like 3.14 ...
They just discovered it, not by caculation but rather by observation and logical conclusion
Dear Kristian,My doubt is still not cleared. I have a material with MTC showing >300J CVN energy at -40î Now my welding code is AWS D1.1, which states, " for materials with SMYS>640MPa, CVN energy shall be as per contractual requirements"; my contractor does not have any CVN acceptance criteria.
Now please tell me, how to get the acceptance criteria.
2011/7/19 Kristian Lund Jepsen (KUJ) <KUJ@ramboll.com>
Harish,
If your order (contract and/or design documentation) does not give any specific requirements regarding CVN, you are probably going to manufacture piping or steel in a low class, where there is no requirements on impact testing.
Then you don't need any qualification of welding procedures as regards the impact energy.
But it might be a good idea to have that confirmed by your costumer.
regards
Kristian
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Harish Kannepalli
Sent: 18. juli 2011 19:27Subject: Re: [MW:11814] CVN Energy
To: materials-welding@googlegroups.com
Thanks Kristian. Now i have an unlisted steel, whose base metal CVN energy in MTC shows 280J at -40û so what is acceptance for PQR coupon. Here we cannot consider base metal energy as acceptance criteria. I do not have contract/design requirements.
2011/7/18 Kristian Lund Jepsen (KUJ) <KUJ@ramboll.com>
The 27 J impact energy (minimum) at the minimum design temperature did arrive from European regulations and standards as mentioned below. They are based on experience on what is "safe".
The 27 J will apply both to base material (pipe, beam, plate, etc.) and welds (basically the HAZ of the welds). The welding procedure (the welding procedure shall be qualified including impact testing, the test will be part of the PQR.
The welds are often the most critical ones in relation to charpy. Going back in the history, it was also the welds (HAZ) that failed on the Liberty ships being built during world war II. This was really the beginning of requiring charpy tests in connection with qualification of welding procedures. Ref. for example: http://en.wikipedia.org/wiki/Liberty_ship
regards
Kristian
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Harish Kannepalli
Sent: 17. juli 2011 19:19
To: materials-welding@googlegroups.comSubject: Re: [MW:11791] CVN Energy
Dear All,
I think i could not convey my concern properly. How did the value 27J arrive? For base materials, we can say minimum requirements, but design codes also ask for min. energy requirements on weld coupons; where the microstructures are different from that of base materials.
2011/7/17 Kristian Lund Jepsen (KUJ) <KUJ@ramboll.com>
Yes, depends on, if you think about piping or steel structure – and also the code you are using.
In Europe, all piping under PED (Pressure Equipment Directive, 97/23/EC) shall as a minimum have impact energy 27 J at the minimum design temperature of the piping. This is also implemented in the European piping code, EN 13480 and the European pressure vessel code, EN 13445.
For structural steel in accordance with Eurocode 3 (EN 1993), the basic requirement is stated in EN 1993-1-10. Typically it will be required to verify 27 J at min. design temperature, but the actual test temperature/energy is depending on the thickness of the material. A table in EN 1993-1-10 states for EN 10025 steels the actual conditions (temperature and energy) and to what temperatures they may be used, depending on the thickness of the steel plate or section/profile.
regards
Kristian
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of sudhakar kuppuswamy
Sent: 16. juli 2011 20:04
To: materials-welding@googlegroups.com
Cc: pgoswami@quickclic.net
Subject: Re: [MW:11771] CVN Energy
Dear Harish,
Based on the international code 7standard, for a particular standards material there will be a value of energy to be absorbed and temperature at which the CVN test has to be done. refer the tables given in the required codes ,in case of ASME materials refer SEC 2 PART A and B for base material and PART C for welding consumables. You will get any idea.
Since impact properties of a material depends on chemical composition and final Heat treatment carried out during manufacturing, from my knowledge I don't think there will be any specific formula to correlate . Generally CVN test is carried out on trial and error basis in manufactures industries .
On Sat, Jul 16, 2011 at 10:18 PM, Harish Kannepalli <harishkannepalli@gmail.com> wrote:
Dear Sir,
I have a very basic doubt since long time, posted in this forum also. How do we get the minimum energy requirements for CVN tests at a particular temperature? Is there any mathematical calculation to get this energy?
--regards,
Harish.
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