Steel plate with yield strength at 890mpa level and low welding crack sensitivity and manufacturing method therefor

Abstract

A steel plate with yield strength at an 890 MPa level and low welding crack sensitivity and a manufacturing method therefor. Weight percentages of components thereof are: C: 0.06-0.13 wt. %, Si: 0.05-0.70 wt. %, Mn: 1.20-2.30 wt. %, Mo: 0-0.25 wt. %, Nb: 0.03-0.11 wt. %, Ti: 0.002-0.050 wt. %, Al: 0.02-0.15 wt. %, and B: 0-0.0020 wt. %, where 2Si+3Mn+4Mo≤8.5, and others being Fe and inevitable impurities. The use of controlled thermo-mechanical rolling and cooling technologies is beneficial to improvement of steel plate strength, plasticity and toughness. The yield strength of the steel plate is greater than 890 MPa, the tensile strength is greater than 950 MPa, the charpy impact work Akv (−20) is greater than or equal to 120 J, and the welding crack sensitivity indicator Pcm is less than or equal to 0.25%.

1 . A steel plate with a yield strength at an 890 Mpa level and low welding crack sensitivity, wherein the steel plate has the following components in weight percentage: C of 0.06-0.13 wt. %, Si of 0.05-0.70 wt. %, Mn of 1.20-2.30 wt. %, Mo of 0-0.25 wt. %, Nb of 0.03-0.11 wt. %, Ti of 0.002-0.050 wt. %, Al of 0.02-0.15 wt. %, and B of 0-0.0020 wt. %, with 2Si+3Mn+4Mo≤8.5, the balance being Fe and inevitable impurities; and the steel plate meets the welding crack sensitivity index Pcm≤0.25%. 
     
     
         2 . A method for manufacturing a steel plate with a yield strength at 890 Mpa level and low welding crack sensitivity, comprising the steps of:
 1) smelting and casting   the following chemical components were smelt and casted to a continuous casting billet or steel ingot of a thickness not less than 4 times of the thickness of the finished steel plate; the continuous casting billet or steel ingot has the following chemical components in weight percentage: C of 0.06-0.13 wt. %, Si of 0.05-0.70 wt. %, Mn of 1.20-2.30 wt. %, Mo of 0-0.25 wt. %, Nb of 0.03-0.11 wt. %, Ti of 0.002-0.050 wt. %, Al of 0.02-0.15 wt. %, and B of 0-0.0020 wt. %, with 2Si+3Mn+4Mo≤8.5, the balance being Fe and inevitable impurities; and the steel plate meets the welding crack sensitivity index Pcm≤0.25%;   2) heating and rolling   the heating temperature is 1050-1180° C., and the holding time is 120 to 180 minutes;   the rolling is divided into a first stage of rolling and a second stage of rolling;   during the first stage of rolling, the start rolling temperature is 1050-1150° C., and when the thickness of the rolled piece reached 2-3 times of the thickness of the finished steel plate, it is stayed in the roller bed until the temperature reached 800-860° C.;   during the second stage of rolling, the pass deformation rate is 10-28%, and the finish rolling temperature is 780-840° C.;   3) Cooling   the steel plate is cooled to 220-350° C. at a speed of 15-30° C./S, and air cooled after being out of water.   
     
     
         3 . The method for manufacturing the steel plate with a yield strength at 890 Mpa level and low welding crack sensitivity of  claim 2 , characterized in that, in step 3), the air cooling is cooling in packed formation or in a cold bed.