Process for improving comprehensive mechanical performances of weld of high-frequency straight welded tube

Abstract

The invention discloses a process for improving the comprehensive mechanical performances of the weld of a high-frequency straight welded tube. The process comprises the following steps: 1, carrying out intermediate frequency heating; 2, water mist cooling: allowing the tube to run along a roller way for 1-3m after the intermediate frequency heating insulation of the weld, and carrying out water mist cooling, wherein the water mist cooling water pressure is 0.4-0.6Mpa, the weld cooling speed is 80-100DEG C / s, and the final cooling temperature is 400-600DEG C; 3, air blowing: blowing by compressed air after the water mist cooling, wherein the pressure of the compressed air is 0.1-0.3MPa; and 4, natural cooling and water cooling treatment: naturally cooling through allowing the welded tube to move forward with the roller way after the compressed air blowing, and carrying out the water cooling treatment of the whole welded tube after the body temperature of the welded tube decreases to 350DEG C or less to complete the heat treatment of the weld. The weld processed through the process has the advantages of good mechanical performances, high surface qualify, convenient processing and low cost.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of high-frequency straight seam welded pipes, and in particular relates to a process method for improving the comprehensive mechanical properties of weld seams of high-frequency straight seam welded pipes. Background technique [0002] With the continuous progress of hot-rolling technology in my country, the production of hot-rolled coils of pipeline steel currently adopts temperature-controlled rolling (TMCP) technology. In the production of pipeline steel (X70 and above steel grade), the strength and performance of the steel are improved by adding a large amount of precious alloy (such as Mo, etc.) to the process of controlling rolling to ensure performance with an appropriate amount of microalloy components. the strength of steel. However, in the production of X70 grade high-frequency straight seam welded pipe, the weld seam needs to be subjected to simulated normalizing heat treatment af...

AI Technical Summary

Problems solved by technology

This method is currently the main method to solve the low strength of the weld seam after normalizing heat treatment, but there are some problems in the implementation of this method

(1) During production, the quenching high and low pressure water systems operate normally at the same time, resulting in high production costs

(2) The design of the nozzle and the matching of the cooling method have high requirements; the stable water-air ratio can ensure uniform cooling, and the cooling range is narrow. When cooling with this method, the cooling will be uneven.

(4) After quenching, the weld strength increases but the impact toughness decreases significantly

Based on the above reasons, the weld area of ​​the high-frequency longitudinal welded pipe treated by the current heat treatment method is martensitic, and the comprehensive mechanical properties are poor, which cannot well meet the standard requirements for oil and gas pipes.

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