ONLINE-CONTROLLED SEAMLESS STEEL TUBE COOLING PROCESS AND SEAMLESS STEEL TUBE MANUFACTURING METHOD WITH EFFECTIVE GRAIN REFINEMENT

摘要

An online-controlled seamless steel tube cooling process with effective grain refinement, comprising the following steps: when the temperature of a crude tube is higher than Ar3, evenly spraying water along a circumferential direction of the crude tube so as to continuously cool the crude tube to T1°C-T2°C, the cooling rate being controlled to be N1°C/s-N2°C/s, where T1=810-360C-80(Mn+Cr)-37Ni-83Mo, T2=T1+115°C, N1=55-80×C, N2=168*(0.8-C), and C, Mn, Cr, Ni and Mo in the equations respectively represent the mass percents of corresponding elements in the seamless steel tube; then, cooling to the room temperature, the cooling rate not exceeding 10°C/s. Correspondingly, also provided are a seamless steel tube manufacturing method with effective grain refinement, and a seamless steel tube. The online-controlled seamless steel tube cooling process does not require the addition of too many alloying elements do not need to be added, is simple and can yield seamless steel tubes with good grain refinement and better toughness.