Hydrogen Cracking Types 2

[zibaeng]

Hi everyone.
Excuse me because of my bad english grammer.
I searched into the internet and some handbooks for hydrogen cracking types, and found different answers.
Am I right? "There are 4 types: Cold cracking, underbead cracking, HAZ cracking and delayed cracking"
If it is right or not, please help me to know the names and definitions of different types.
Thanks a lot.

 

[metengr]

zibaeng;
I would suggest in lieu of hydrogen cracking you use the phrase hydrogen embrittlement from welding, since your examples above pertain to welding;

http://www.aws.org/wj/jan04/still_feature.html

 

[gtaw]

The terms delayed cold cracking, underbead cracking, and HAZ cracking are often used to describe cracking problems associated with diffusible hydrogen when welding various steels.

With the exception of austenitic stainless steels, steel alloys that have higher carbon content or higher carbon equivalencies are more susceptible to hydrogen assisted cracking.

Preheat is typically used to mitigate the potential for hydrogen cracking when welding. Post weld heat treatments also reduces the potential for hydrogen assisted cracking by modifying the microstructure and permitting the hydrogen to The terms delayed cold cracking, underbead cracking, and HAZ cracking are often used to describe cracking problems associated with diffusible hydrogen when welding various steels.

Preheat is typically used to mitigate the potential for hydrogen cracking when welding. Post weld heat treatments also reduce the potential for hydrogen assisted cracking by modifying the microstructure and permitting the hydrogen to effuse into the atmosphere without causing damage.

With the exception of austenitic stainless steels, steel alloys that have higher carbon content or higher carbon equivalencies are more susceptible to hydrogen assisted cracking. Hydrogen assisted cracking is associated with martensite. The higher the carbon content or the higher the carbon equivalency, the greater the potential of forming hard, brittle martensite in the HAZ if the cooling rates are not controlled. Increased amounts of martensite and increased quantities of diffusible hydrogen increases the potential for hydrogen assisted cracking problems.

Slow controlled cooling while welding or selecting steels with low carbon equivalencies reduce the potential for forming martensite. Reducing the quantity of diffusible hydrogen into the weld pool also reduces the potential for hydrogen assisted cracking. Combining reduced cooling rates, using steels with low carbon equivalencies, and using a low hydrogen welding process reduces the potential for hydrogen assisted cracking.


Best regards - Al

 

[Guest102023]

The confusion surrounding the jargon describing hydrogen issues in steel is rivaled only by that describing high-temperature creep & fatigue issues.

 

[btrueblood]

I like that reply, brimstoner.

 

[bklauba]

Below is an excerpt found AcelorMittal's North American website, in their white paper "How to weld T-1":

‘Generally, welded structures of ArcelorMittal USA “T-1” Steels should not be given a postweld heat treatment. Loss of weld-metal and heat-affected-zone toughness and stress-rupture cracking may occur as a result of such a treatment. Many modern steels for welded construction, such as the “T-1” Steels, are designed to be used in the as-welded condition. Unlike some carbon steels, the postweld heat treatment process can have an adverse effect on such alloy steels. Those alloying elements that contribute most significantly to the attainment of high strength and notch toughness in alloy steels and in weld metal joining these steels are usually the alloy elements that have an adverse effect when weldments of such steels are postweld heat treated.’

So, it would appear that certain alloys (which are footnoted in their plate spec manual) should either not receive post weld heat treatment after welding, or should only be heat treated with very careful precautions and testing. It would appear that they would normally recommend avoiding what would be considered a thermal stress relief.

However, heating to temperatures well short of TSR (500 - 600 F) and held at that temp for sufficient time, should get rid of the hydrogen.

 

[SectionIX]

The link has an excellent video showing how delayed cracking occurs and can be controlled.

http://www.dnvusa.com/resources/video/HydrogenDiffusionDemonstration.asp

 

[gtaw]

Excellent video!

Best regards - Al

 

[Guest102023]

Great video - the mineral oil demonstration makes it real.

 

[Guest102023]

p.s., there are other videos on the DNV site that also look interesting.

 

[vanci]

What about Hot Cracking?

 

[kingnero]

What about it? Do you know what sulphur does?