Economical fabrication method of high-toughness X70 pipeline hot rolled steel plate coil

Abstract

The invention provides an economical high-toughness X70 pipeline hot rolled steel plate coil and a preparation method thereof. The X70 pipeline hot rolled steel plate coil comprise the following chemical components by weight percentage (%) of: 0.060%<C<=0.075%, 0.15%<=Si<=0.30%, 1.20%<=Mn<=1.65%, 0.070<Nb<=0.080%, 0.010%<=Ti<=0.020%, and Cr<=0.25%. The preparation method includes steps of: a heating procedure, a rough rolling procedure, a finish rolling procedure, a cooling procedure and a coiling procedure, wherein in the finish rolling procedure, the rolling temperature of the first pass of finish rolling is not higher than 1050 DEG C, the deformation for the last pass of finish rolling is less than 8%, the accumulated deformation of the last two passes is less than 16%, and the finishing temperature of the finish rolling is 770-850 DEG C; in the cooling procedure: laminar cooling is conducted at a cooling rate of 18-26 DEG C / s after the finish rolling; and in the coiling procedure, coiling is conducted at 300-400 DEG C after the laminar cooling.

Description

technical field [0001] The invention relates to a hot-rolled coil of X70 pipeline steel and a preparation method thereof. Background technique [0002] The composition design of 'Nb + Mo' is generally used in the production of X70 pipeline steel at home and abroad to obtain acicular ferrite structure; on the one hand, it can obtain higher low-temperature impact toughness; The yield strength property of the material decreases after the tube. After a lot of research, it is found that in the industrial production of X70 pipeline steel, even if molybdenum is used, uniform acicular ferrite structure cannot be completely obtained, and the occurrence of Bauschinger effect cannot be completely avoided. In severe cases, the matrix structure of X70 pipeline steel coils is a mixed structure of polygonal ferrite, granular bainite and a small amount of acicular ferrite, and the drop in yield strength before and after coiling is close to 100MPa, making X70 steel pipes The yield strength...

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Problems solved by technology

[0003] In addition, the use of molybdenum in the manufacture of X70 coils can suppress the formation of polygonal ferrite and make it easier to obtain acicular ferrite, making the manufacturing process simple and feasible. However, the disadvantages of this method are also obvious, that is, in Every time 0.10% molybdenum is added to the steel, the production cost per ton of steel will increase by 220-250 yuan

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