[MW:2294] RE: 2291] Re: 2286] Re: hydro test --- 95% SMYS

Hi!

Hydro Test never increases the resistance to brittle fracture.

To reduce brittleness (Reduce the hardness ) , You need to carry stress relieving , which is carried by heating to  600-620C (Depends upon material grade) soak for at least  1hr/ inch and cool in furnace.

ii) Second method is by ultrosonicaly / vibration ,  you can reduces the stresses but you can not reduce the hardness (This method is used for  Machine tool fabricated components (like frame)

Regards

 

Hegde

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Agung Wenda
Sent: Monday, June 01, 2009 11:04 AM
To: materials-welding@googlegroups.com
Subject: [MW:2291] Re: 2286] Re: hydro test --- 95% SMYS

 

Hi all,

One of the methods of eliminating residual stress is by heat treatment i.e. stress relieving, done at about 650 ºC (1202 ºF) for about one hour or till the whole part reaches the temperature then air cooled in still air. This removes more than 90% of the internal stresses.

To increase resistance to brittle fracture or in another word increasing mechanical properties such as ductility, can be done in several methods in metallurgical stand point of view. One of them is by cold working, such as rolling etc., the reason for this is strain hardening where dislocation density increases with plastic deformation.

The point is, hydrotest will not allow material to undergo plastic deformation not even reach yield strength. And hydrotest is not involving high temp either, thus such strengthening mechanism or eliminating residual stress will not occur. 

fyi and ref

ADW - Indonesia

 

2009/5/31 Pablo Acelajado <pjacelajado@npc.com.sa>

 

May 31, 2009

 

Hi,

 

Indirectly the material is cold drawn very slightly during hydrotest at high pressure (90% - 95%SMYS) and becomes stronger. It also follows that there is reduction in the residual stress.

 

Good luck.

PJA

SAVE TREES  - THINK BEFORE YOU PRINT

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Shank Vagal
Sent: Sunday, May 31, 2009 1:36 PM
To: materials-welding@googlegroups.com
Subject: [MW:2286] Re: hydro test

 

Ali. This is a very unusual query; hydrotest is an integrity test. All other things - where did you get them from? Rgds Shank --- On Sun, 31/5/09, Ali Asghari <asghariali@rocketmail.com> wrote: From: Ali Asghari <asghariali@rocketmail.com> Subject: [MW:2285] hydro test To: materials-welding@googlegroups.com Date: Sunday, 31 May, 2009, 9:07 AM hi can every body answer two follwing questions? how hydro test increase the resistance to brittle fracture or failure by crack like flaw?do hydro test decrease residual stress?   regard advance.

 

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