Cracks in the soda ash pipeline
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Within a 30-meter radius around the inlet and outlet pipelines of the soda ash (30%) pump in our plant, longitudinal cracks of varying degrees have appeared in the welds after some time of operation. Could everyone please help analyze the cause? Pipe diameter: DN80*4; material: 20# steel. Argon arc welding is used for root pass, with J507 filler metal for the cover pass. Post-weld heat insulation is applied.
The weldability of 20# steel is excellent; this situation shouldn’t occur, right? I suspect there’s something wrong with the material
It is recommended to use non-metallic materials for transporting soda ash, as the results will definitely be much better than those achieved with metal pipes.
This kind of alkali embrittlement occurs when the temperature is relatively high. Personally, I believe there’s also a problem with the electrode you chose; generally, J422 is sufficient.
I don’t think it’s a welding problem; the J507 electrode poses no issues at all. Here, we basically use the 507 electrode for all carbon steel welding. It seems that there’s no real need for heat insulation after welding this pipe. (When you mention heat insulation after welding, does that mean the environmental conditions during welding were poor—like rainy weather or winter conditions?)
This post was last edited by yanlianzi on 2011-5-9 at 09:10. Reply to 1# sunshubin: It’s a matter of material; it’s due to stress cracking
For alkali embrittlement, it is recommended to use 304 material
Hehe, this is caused by alkali embrittlement, which falls under the category of stress cracking. The original poster used the wrong material; the carbon content in Grade 20 steel is too high. It is recommended to use Grade 10 steel instead, as it can better prevent stress cracking caused by alkali embrittlement
It should be a material issue. Here, we also use ordinary carbon steel pipes to transport liquid caustic soda, and this phenomenon has never occurred
Thank you all. I wonder if it’s due to the vibrations of the pump; please help me analyze this.