A method of controlling nitrogen content in n80 steel

Abstract

The invention relates to a method for controlling the nitrogen content in N80 steel. The method comprises the following steps: firstly, the LF slag smelting is stabilized and the deoxidation technology is perfected so that the weight and the components of the molten slag are controllable and the nitrogen flushing state during the process is stable; secondly, the proper nitrogen flushing flow, pressure and time are set in the VD packing process so that the nitrogen content after emptying is stable; and thirdly, the proper nitrogen flushing time, flow and pressure are set after the VD emptying so that the nitrogen content is stable and controllable. The method performs improvement to the non-quenching and tempering way, effectively controls the nitrogen content in the N80 level steel by taking measures, not only has low cost, but also effectively reduces the surface cracks of the casting billet and improves the quality of products.

Description

technical field

[0001] The invention relates to a method for controlling nitrogen content in N80 steel. Background technique

[0002] At present, domestic production of N80 oil pipe steel is generally produced by quenching and tempering treatment. This production method has many procedures and high cost. However, the non-quenching and tempering method is used for production, that is, it is controlled by adding vanadium-nitrogen alloy or ferrovanadium plus nitrogen blowing process, and the vanadium and nitrogen content in the steel must be guaranteed. The cost of the former is high, and the alloy yield is not stable; although the cost of the latter is low, but the process of blowing nitrogen into the ladle is adopted, the control of nitrogen content is unstable, because N80 steel requires high content of [N] and [V] , resulting in the precipitation of [VNC] compound on the grain boundary, thereby destroying the continuity of the grain boundary, causing the grain boundary to ...