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bagel

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  1. I understand that there is a requirement from the API 5L PSL2 regarding the yield to tensile ratio which I believe is to safeguard the material from failure happens all in a sudden without any warning signal from deformation due to yield. The typical required max yield to tensile ratio is 0.93 which means that the tensile strength is at least 7% higher than the yield strength. The max ratio of high grade material in API 5L PSL2 is getting even higher which seems to be even more risky in terms of sudden tensile failure. According to the British Gas specifications back in 80s, they required an additional requirement on pipe ordering using API 5L specification with a more stringent requirement of max yield to tensile ratio at 85% I would appreciate it if any friends in this forum can enlighten me the rationale of such figure of 0.93. Thank you very much.
  2. Hi allWe are currently conducting Charpy V Notch Test to the Longitudinal Weld Seam of a Steel Pipe. The specimens were taken as transverse and 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.
  3. Hi allWe have been sourcing Class 4.6 bolts of the following specifications :1. Acceptable fastener standards: ISO4762 (Cap Heads), ISO4014 (Hexagonal Head), etc2. Mechanical properties: ISO 898-1:2013 especially Table 2 and 3 with impact energy of at least 27 J tested at – 20 degC or at least 40 J tested at room temperatureHowever, we have difficulty sourcing these bolts in good quality. Previously, we have bought some bolts but they showed poor performance in elongation and impact tests.As such, we would appreciate it if any of you could advise any source that we can purchase these Class 4.6 bolts in good quality. Thank you very much.
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