Low-cost production process for increasing fault detection qualification rate of Q345R steel plates

Abstract

The invention relates to a low-cost production process for increasing the fault detection qualification rate of Q345R steel plates. The process mainly comprises the following steps: performing molten iron feeding with the content of S less than or equal to 0.010%, performing converter tapping with the total oxygen content controlled to be less than or equal to 20 ppm, and performing LF refining with the content of S controlled to be less than or equal to 0.005%; when the steel plate thickness is more than or equal to 60 mm or the compression ratio is less than or equal to 10, performing on-line shearing and RH refining, wherein the degree of vacuum is less than or equal to 5.0 mbar, and the maintaining time is more than or equal to 12 min; when the product thickness is controlled to be 12-80 mm, controlling the fine rolling temperature to be 1020-870 DEG C and the finish rolling temperature to be 820-830 DEG C, and discharging and cooling after the self-tempering temperature is controlled to be 700-680 DEG C; when the product thickness is less than or equal to 60 mm and the discharge temperature is more than or equal to 350 DEG C, shearing after stacking for slow-cooling for 72 h. The production process achieves the purpose of increasing the fault detection qualification rate of Q345R steel plates with low cost through the procedures of scientific and reasonable distribution and control of sulfur, deep deoxidation, RH refining, steel plate stacking for slow-cooling and the like.

Description

technical field [0001] The invention relates to a production process of a steel plate for a pressure vessel, specifically a low-cost production process for improving the qualified rate of flaw detection of a Q345R steel plate, and belongs to the field of metallurgy. Background technique [0002] Q345R steel is an ordinary low-alloy steel plate for pressure vessels with a yield strength of 340MPa. It has good comprehensive mechanical properties and process properties. It is currently the most widely used and used steel plate for pressure vessels in my country. Therefore, there are strict requirements on its surface and internal quality. However, the high unqualified rate of Q345R steel plate flaw detection has always been one of the most common problems in the production process. According to relevant inspection and analysis, the main defects that lead to the unqualified flaw detection of Q345R steel plate are central segregation, central cracks and MnS inclusions, etc. . T...

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Problems solved by technology

[0003] Chinese patent CN102002630A discloses a "steel Q345R-Z35 extra-thick plate for anti-HIC pressure vessel and its production method". Casting, ingot heating, rolling, ACC cooling, straightening, steel plate stack cooling, normalizing heat treatment and other processes; this invention has developed a steel plate for extra-thick pressure vessels through reasonable composition design and process route design. The test results show that , the passing rate of the first-level flaw detection and the passing rate of the preliminary performance inspection are all 100%. In addition, the lamellar tear resistance performance reaches the Z35 level, and the hydrogen-induced cracking test results are excellent; the disadvantage is that it adopts mold casting and adds normalizing The heat treatment process not only reduces the production efficiency, but also increases the production cost