Charpy Test for the Longitudinal Weld Seam of Steel Pipe

[bagel_68]

Hi all

We are currently conducting Charpy V Notch Test to the Longitudinal Weld Seam of a Steel Pipe. The specimens we have tests are of two different size : full size (10mm x 10mm x 55mmL) and 2/3 size (6.7mm x 10mm x55mmL).

We have conducted the tests severally time at -30degC. The results of the 2/3 size were consistently larger than that of the full size.

We are trying to explain this strange situation. It is because larger the cross sectional area should require more impact energy but in this case it is the other way round. Would like to seek opinion / comment on this situation.


More info about the pipe is given below :

The longitudinal weld seam was welded by submerged arc welding during the pipe manufacturing.

The bevel for the longitudinal weld is of x-groove (or double v-bevel), i.e. the submerged arc welding are to be carried out on both the external face and internal face.

The pipe is 600mm diameter and 12.7mm thick.Thank you very much.

 

[Achy47]

Hello,

Thank you for sharing your findings and seeking opinions on this situation. I would like to offer my insights on this issue.

Firstly, it is important to understand the purpose of conducting a Charpy V Notch Test on a steel pipe. This test is used to measure the impact strength and toughness of a material, which is crucial for determining its suitability for certain applications. The impact strength is the amount of energy absorbed by a material before it fractures, while toughness is the ability of a material to resist cracking and fracturing.

Now, coming to your findings, it is indeed strange that the 2/3 size specimens consistently showed larger results than the full size specimens. One possible explanation for this could be the difference in microstructure between the two sizes. The full size specimen may have a coarser grain structure compared to the 2/3 size specimen, which could make it more prone to brittle fracture at low temperatures. On the other hand, the 2/3 size specimen may have a finer grain structure, making it more tough and able to absorb more impact energy before fracturing.

Another factor to consider is the welding process used for the longitudinal weld seam. Submerged arc welding involves the use of a flux layer, which can affect the microstructure of the weld and the heat-affected zone. It is possible that the 2/3 size specimens, being smaller in size, may have been welded more consistently and uniformly compared to the full size specimens, resulting in a more homogeneous microstructure and better impact strength.

It would also be helpful to know if the specimens were taken from different locations along the length of the pipe. It is possible that the full size specimens were taken from a region with higher residual stresses or defects, which could affect their impact strength.

In conclusion, there could be various factors at play here, including microstructure, welding process, and specimen location. It would be beneficial to conduct further experiments and analyze the microstructure of the specimens to understand the root cause of this difference in results. I hope this helps and please feel free to reach out for any further clarification.