Low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding and manufacturing method therefor

Abstract

The present disclosure provides a low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding and a manufacturing method therefor. The low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding includes, by weight in percent, 0.04%-0.13% C, 0.10%-0.40% Si, 0.60%-1.30% Mn, 0.005%-0.012% P, S≤0.006%, 0.01%-0.05% Al, 0.03%-0.15% Sn, 0.005%-0.020% Nb, 0.005%-0.025% Ti, 0.15%-0.40% Ni, 0.15%-0.50% Cu, 0.10%-0.25% Cr, 0.007%-0.024% Ca and the balance Fe and inevitable impurities. The corrosion-resistant steel provided by the present disclosure is mainly designed for the upper deck and inner bottom plate of a storage and transportation tank of a polar route oil tanker, and the steel has excellent low-temperature toughness and can be welded with large heat input.

1 . A low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding, comprising, by weight in percent:
 0.04%-0.13% C, 0.10%-0.40% Si, 0.60%-1.30% Mn, 0.005%-0.012% P, S≤0.006%, 0.01%-0.05% Al, 0.03%-0.15% Sn, 0.005%-0.020% Nb, 0.005%-0.025% Ti, 0.15%-0.40% Ni, 0.15%-0.50% Cu, 0.10%-0.25% Cr, 0.007%-0.024% Ca and the balance Fe and inevitable impurities.   
     
     
         2 . The low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 1 , further comprising, by weight in percent, at least one of 0.02%-0.15% Sb, 0.03%-0.10% W, 0.05%-0.15% Mo and 0.05%-0.10% RE. 
     
     
         3 . The low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 1 , wherein the inevitable impurities comprise, by weight in percent, 0.0020%-0.0060% N, H≤0.00015% and O≤0.0020%. 
     
     
         4 . The low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 3 , wherein the ratio Ti/N falls within 2.43-3.56. 
     
     
         5 . The low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 1 , wherein Ni+Cu is ≥0.35% and the ratio Ni/Cu is ≥0.70, and the ratio Ca/S falls within 1.8-4. 
     
     
         6 . A method for manufacturing the low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding, comprising:
 heating, for 3-5 hours, a plate slab with the components  claim 1  to  1100  ° C. to 1150° C.;   performing first-stage rolling on the heated steel slab to obtain an intermediate slab, and performing second-stage rolling on the intermediate slab, wherein an initial rolling temperature of the first-stage rolling is 950° C. to 1100° C., an initial rolling temperature of the second-stage rolling is 850° C. to 900° C., and a final rolling temperature of the second-stage rolling is 800° C. to 860° C.; and   performing on-line cooling on the rolled steel plate to 500° C. to 600° C. at a cooling rate of 5° C./s-20° C./s to obtain the steel plate.   
     
     
         7 . The method for manufacturing the low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 6 , wherein in the rolling process, the final rolling temperature of the second-stage rolling ranges from 840° C. to 860° C.; and in the on-line cooling process, the rolled steel plate is cooled to 550° C. to 600° C. at the cooling rate of 5° C./s to 15° C./s, and a pearlite volume fraction of the cooled steel plate is ≤30%. 
     
     
         8 . The method for manufacturing the low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 6 , wherein in the rolling process, the initial rolling temperature of the second-stage rolling ranges from 850° C. to 890° C., and the final rolling temperature of the second-stage rolling ranges from 800° C. to 840° C.; and in the on-line cooling process, the rolled steel plate is cooled to 500° C. to 560° C. at the cooling rate of 7° C./s to 20° C./s, and a bainite volume fraction of the cooled steel plate is ≤35%. 
     
     
         9 . The method for manufacturing the low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 6 , further comprising:
 performing offline cooling: stacking, for not shorter than 24 hours, to slowly cool a straightened finished steel plate with a thickness ≥40 mm with an initial temperature being 250° C. to 400° C., shearing and getting the product off a production line, and transporting same to a finished product stacking area.   
     
     
         10 . The method for manufacturing the low-temperature-resistant and corrosion-resistant cargo oil tank steel suitable for high-heat-input welding according to  claim 6 , wherein
 in the rolling process, the ratio of a thickness of the intermediate slab to a thickness of a finished steel plate is not less than 2.5, and a cumulative reduction rate of the first-stage rolling and the second-stage rolling is not less than 50%.