Hydrogen embrittlement

[Jap1]

My company is going to make cylinders that made of 4140 Q&T steel pipe. Chrome plating is applied to cylinder surface after final machining. Tensile strength is around 145 ksi with HRC 32 based on the MTR. Do we need to worry about hydrogen embrittlement? Or do you suggest hydrogen baking should be done ?

 

[mfgenggear]

Op
General rule of thumb is steel equal to or harder than 40 HRc should be post bake.
Follow the recommendations of AMS2759/9

 

[EdStainless]

First question, why are you working with such a low strength?
You can go higher and still have good toughness, and it will support the Cr better.
If it were me, I would bake after plating.

 

[Jap1]

First question, why are you working with such a low strength?
You can go higher and still have good toughness, and it will support the Cr better.
If it were me, I would bake after plating.

Thank you for you valuable feedback. I was told that stainless steel pipes were not available from a vendor, so we received A 519, 4140 QT 110 pipes, and some of pipes are over-sized due to the availability. I was reviewing the MTRs this Monday, and I had a thought that I should be concerned about hydrogen embrittlement or not. I heard all kind of hardness numbers such as above HRC 30, 35, and 40 regarding hydrogen embrittlement.

 

[Jap1]

Op
General rule of thumb is steel equal to or harder than 40 HRc should be post bake.
Follow the recommendations of AMS2759/9

Thank you for you insight. I'll look into the procedure.

 

[mfgenggear]

 

[GD2]

See the following Excerpts from API 571:
4.5.6.6 Prevention / Mitigation
a) Dependent on the source of the hydrogen, alloy composition and fabrication/heat treatment history.
b) Use lower strength steels and PWHT to temper the microstructure, improve ductility and reduce
residual stresses and hardness.
c) During welding, use low hydrogen, dry electrodes and preheating methods. If hydrogen is expected
to have diffused into the metal, an elevated temperature bake out [400°F or higher (204°C or higher)]
may be required to drive the hydrogen out prior to welding.
d) Heavy wall equipment in hot hydrogen service requires controlled shutdown and start-up procedures
to control the pressurization sequence as a function of temperature.
e) In corrosive aqueous services, apply a protective lining, SS cladding or weld overlay to prevent the
surface hydrogen reactions.