engleski

The effect of chemical composition of micro-alloyed steel on the production of thick-wall tubes

In this work, structural changes of steel at the production of as rolled scamless tubes, of size 85x9''x20.9 mm with quality grade N-80 according to API Std SCT are given. The performed correction of chemical composition by decreasing the content of C and V, and increasing the content of Al and N enabled no uniform forming of fine-corn structure alongside the whole transversal cross section of robe wall and therefore the expected results were not achieved. This is why, on the basis of analysis of test results, the corrected chemical composition is proposed: addition of No and Ni and an increased portion of Nb. A remarkable decrease of S is recommended because of its distinguished negative effect on transversal ductility.

micro-alloyed steel; seamless tubes; microstructure; ductility

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