Achievements in quality improvement of large diameter thick wall seamless steel

2021-07-05 15:38:43 COMMENT：0 HITS：

　　To improve the first pass rate of large diameter and thick wall seamless steel pipe and strip was listed as one of the key projects in 2014, and the research institute took the lead in organizing relevant personnel of large-scale material and wire rod companies to study and determine the key measures. In the last ten days of March, the heating process of die cast bearing steel ingot was optimized to make the ingot fully diffuse at high temperature and reduce the segregation degree of carbide in billet. In April, the bar and wire company formulated the test plan and detailed process plan of controlled rolling and controlled cooling, and took measures such as restoring the function of 36mm cooling water pipe of No.1-3 water tank, adding No.4 water tank after shearing, optimizing the shearing capacity of sectional shearing, etc., which enhanced the cooling intensity and uniformity after rolling, and controlled the temperature of upper cooling bed of 35mm bar product at 680-700 ℃, The precipitation of secondary carbide network in rolling process is reduced.

　　Network carbides are secondary carbides precipitated along austenite grain boundary in the temperature range of 700-900 ℃ during and after rolling; Banded carbide is a kind of carbide segregation with high and low concentration formed by dendrite segregation during pouring and rolling. Network and band carbides are the main factors that affect the mechanical properties of bearing steel and reduce the contact fatigue life of bearing parts.

　　After four months of quality research, the first pass rate of reticulated and banded carbides in bearing steel bar of large diameter and thick wall seamless steel pipe casting in Dalian has been increased by nearly 20%. The success of the project is of great significance in improving product quality, increasing market share and accumulating technical experience.

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