Manufacturing method of X70 pipeline steel hot rolled steel roll

Abstract

The invention discloses a manufacturing method of X70 pipeline steel hot rolled steel roll, the components of the X70 pipeline steel hot rolled steel roll do not adopt alloys such as V, Mo, Cu and the like, the Nb alloy content is improved, and a proper amount of Cr is added. The manufacturing method is characterized in that a normal temperature casting blank enters in a heating furnace to heat, the heating temperature is 1180-1220 DEG C, the holding time is 150-240 minutes, the casting blank after heating enters a roughing mill group to carry out roll milling, and the percent of reduction from a first pass R1 to a fourth pass R4 of the roughing mill group is greater than 20%; the relative percent of reduction of a fifth pass R5 is greater than 23%, the coarse finishing temperature is 1000-1050 DEG C, and the thickness of a middle blank is 52-60 mm; the steel billet after rough rolling directly enters a refined continuous rolling mill group, the finish rolling temperature is 980-1040 DEG C, and the percent of reduction from a sixth chassis F6 to a seventh chassis F7 of the refined continuous rolling mill group is greater than 8%; a steel plate after finish rolling can be subjected to ultra-fast cold section cooling and streamline flow cooling, the cooling speed is 15-20 DEG C / s, and fast cool section steel plate temperature reduction and front section collection cold cooling steel plate temperature reduction are respectively controlled to 80-100 DEG C; and the temperature is lower than 620 DEG C when a steel plate reaches the middle section of the streamline flow cooling, and the winding temperature is 400-500 DEG C.

Description

technical field [0001] The invention relates to a production method of hot-rolled steel coils, in particular to a method for producing X70 pipeline steel hot-rolled steel coils with low alloy cost and no precious metals such as molybdenum and vanadium by using an ultra-fast cooling process after rolling, which can be widely used It is applied to the production of hot-rolled steel coils for X70 steel grade oil and gas pipelines, especially for X70 steel coils with a thickness of 16mm or more. Background technique [0002] At present, the metallographic structure of high-grade pipeline steel coils at home and abroad generally requires "highly fine-grained" and "highly homogeneous" acicular ferrite to meet the high strength and toughness requirements of pipeline steel coils. The acicular ferrite structure is a bainite-like structure different from the ferrite-pearlite type. The acicular ferrite structure is not a single independent structure, but granular see body, bainite iron...

AI Technical Summary

Problems solved by technology

Among them, Mo or Nb, V, Ni, etc. are all precious metals, which will inevitably increase the overall cost of steel