Analysis and Experimental Study on Butt Welding Mechanism of Thin Wall Core Tube for High-pressure Valve Based on Brazing Process

At present, the mature technology of magnetic core tube includes sleeve brazing and butt welding. In this paper, the vacuum butt brazing test of low carbon steel sleeve and stainless steel magnetic barrier ring is carried out by using copper base filler metal. The interfacial structure and mechanical properties of magnetic core tube brazed joint formed under different brazing temperature, holding time and brazing gap were investigated and analyzed by optical micros-cope and Vickers hardness tester. The pressure test platform was used to test the brazed magnetic core tube under different parameters, and the density of the weld was judged according to the pressure drop results. The blasting test was carried out on the magnetic core tube brazed under different parameters by using the blasting test bench to test the strength of the brazing weld. The results show that the density and strength of brazing seams increase first and then decrease with the increase of brazing temperature, the extension of holding time and the increase of brazing clearance. Combined with the test results, the ideal process parameters of brazing between low carbon steel sleeve and stainless steel magnetic barrier ring are brazing temperature 1050°C, holding time 45min, brazing gap 0.07mm. Under these parameters, the magnetic core tube formed under these parameters has the lowest pressure drop of 10bar and the maximum bursting pressure of 110MPa.