Preparation method of steel for ocean drilling platform

Abstract

The invention discloses a preparation method of steel for an ocean drilling platform. The steel comprises the following chemical ingredients by weight percent: 0.12-0.15% of C, 0.40-0.60% of Si, 0.60-0.80% of Mn, 2.00-2.20% of Cr, 0.10-0.30% of Al, 0.50-0.70% of Mo, no more than 0.015% of P, no more than 0.010% of S, 0.20-0.40% of Cu, 1.20-1.40% of Ni, 0.025-0.045% of Ti, and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: 1) smelting, refining and continuously casting into a billet; 2) soaking the steel billet; 3) carrying out hot rolling, wherein the open rolling temperature is 1130-1160 DEG C, and the final rolling temperature is controlled at 920-950 DEG C; 4) carrying out thermal treatment, namely carrying out normalizing treatment under the condition that the temperature is 880-920 DEG C, and naturally cooling.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for preparing steel for offshore drilling platforms. Background technique [0002] Chinese patent application number 200810119506.9 discloses a "controlled rolling and controlled cooling offshore platform steel and its production method", its chemical composition and weight percentage content are: C 0.05-0.09%, Mn 1.20-1.60%, Si 0.20- 0.50%, Nb 0.03-0.05%, Ti 0.010-0.020%, V 0.03-0.06%, S≤0.005%, Als 0.020-0.040%, P≤0.015%, and the balance is Fe and impurities. The thermomechanical control process (TMCP) is used for production, and the molten steel smelted according to the composition is cast into a 220-250mm thick slab; the slab is loaded into the slab heating furnace for heating, and rolled out of the furnace. The starting temperature of rough rolling is 1060-1160°C; the starting temperature of finishing rolling is 840-940°C; the final rolling temper...

AI Technical Summary

Problems solved by technology

Its disadvantages are: the microstructure of the steel plate produced by TMCP process is not uniform, and the band structure is serious. Although it can be applied to the construction of steel structures on offshore platforms, it is not an ideal lamellar tear-resistant steel because its Zz≥35% , only meet the basic technical requirements, the margin is small, and the problem of lamellar tearing will still occur during construction

Its disadvantages are: there are too many microalloying elements, including difficult-to-control elements N, REM, etc., it is difficult to operate during the smelting process, and it is difficult to control the precision of its composition, which increases the difficulty of production and increases the cost, and the post-rolling control is used in the forming process. The rapid cooling process reduces equipment utilization and production efficiency, making it difficult to popularize and apply in the actual production process

[0004] Similarly, another Chinese patent application 200610024179.X discloses "a seawater corrosion-resistant steel and its production method". Higher precision requirements, significantly increased production difficulty and cost

The expensive alloy element Mo content in the steel is high, which is an uneconomical steel type, and the Al content in the steel is very high, which brings great difficulties to the production of this steel type, especially in the casting process, the formed Al oxides and nitrides are easy to block the casting nozzle and cause production accidents