HIC Test

[dreamschool]

I noticed failures for some heat number ,,,and when we re-rest another plate from the the same heat ...some times it pass the test!!

Can we have different result for the same heat number for HIC test.

we used sloution A and the same procedure !!! Can i have answer for my concer and explination about how these result can be different from test to another
One more thing, the cemical compostion test is OK...sulfur is less than 0.01!!!!
Always the plate passes the HIC...after forming the pipe and take sample from the pipe and conduct HIC test...it failed...

it is strange for me ...i could not understand this...any explination???

i wrote this in steel forum...but it may related to the Metal and Metallurgy

 

[CoryPad]

dreamschool,

Are all the HIC tests performed by the same lab? There can be variations due to procedures, etc. There can be HUGE variations in the material itself, so one region may fail and another may pass.

Possible reasons for plate passing and pipe failing is due to forming stresses. During forming, the material can become strain hardened and have residual stresses. These areas can be more sensitive to HIC testing.



Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dreamschool]

CoryPad,

Thanks for you reply...actualy it has been done from the same lab...same procedure..but different result from the same heat number?

 

[dreamschool]

as you said "Possible reasons for plate passing and pipe failing is due to forming stresses"

But how can we prevent the failure ....We can't change the forming process?

 

[CoryPad]

Perform stress relief after forming. There is considerable information published on this subject - try NACE at:

http://www.nace.org

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[grampi1]

The science behind steel making to prevent HIC is lacking. However, the better mills have developed empirically key composition and processing controls that usually result in reliable HIC test acceptable products. Degree of deoxidation, levels of S, P, Ca, ladle treatment, casting process all play a role.

It is because no other specification requirement(s) are a guarantee of getting hydrogen blister resistant plate, that the HIC test is so useful.

Surely you don't believe quality control is always perfect? You got lucky and found a problem with your supplier before installing it in the field.