CN102251176B - Method for rolling ship plate pitting-resistant blue steel - Google Patents

Abstract

The invention discloses a rolling method of anti-pitting blue skin steel for ship plates, which belongs to the technical field of steel for ship hull structures. After cleaning and inspection, it is loaded into the slab heating furnace for heating. After being released from the furnace, the steel billet is descaled once by high-pressure water; The thickness of the finish rolling joint is 3-5 times the thickness of the finished steel plate, the reduction of each pass is 1-20mm, and the steel plate is cooled by laminar flow. The advantage is that it can improve the surface quality of the ship plate, reduce the carry-over products caused by surface roughness, pitting, iron oxide scale pressing, etc., reduce the production cost, and at the same time, various performances can meet the requirements of ship classification regulations.

Description

A rolling method of anti-pitting blue skin steel for ship plate

technical field

The invention belongs to the technical field of steel for ship hull structure, in particular to a rolling method of anti-pitting blue skin steel for ship plates.

Background technique

The shipbuilding industry is an important part of my country's national economy. It is both a technology-intensive industry and a labor-intensive industry. Accelerating the development of the shipbuilding industry plays an important role in improving the overall level of my country's manufacturing industry, promoting the development of related industries such as steel and supporting electromechanical equipment manufacturing, and expanding employment.

After years of hard work, domestic steel plates for shipbuilding can basically meet the development needs of my country's shipbuilding industry. Especially during the "Eleventh Five-Year Plan" period, the reconstruction, expansion and new construction of medium and heavy plate production lines in iron and steel enterprises have made the production of medium and heavy plates from quantity to quality. have been improved. However, due to the harsh working environment of the ship, the hull of the ship is subject to chemical corrosion of seawater, electrochemical corrosion, and corrosion of marine organisms and microorganisms, and the requirements for surface quality are very strict. Surface quality is one of the main quality indicators of medium and heavy plates, which has an important impact on the processing and use of medium and heavy plates, so it is highly valued by manufacturers and users. It can be said that steel plates without good appearance quality are not recognized by users steel plate. Affected by the international financial crisis, shipowners put forward extremely strict requirements on the surface quality of the hull, followed by shipbuilders putting forward higher requirements on the surface quality of ship plates in steel factories.

At present, the surface color of ship plates produced by major domestic medium and heavy plate companies is basically reddish brown, called "red skin steel". Poor pitting resistance, easy to peel off in scraping and rubbing. However, the surface of foreign ship plates is blue-black, the oxide scale is thin and dense, and has strong bonding force with the steel matrix. To change this situation, it is necessary to start with the structure of the surface oxide scale of the ship plate, increase the content of Fe ₃ O ₄ to make the oxide scale blue and black, and at the same time make the surface oxide scale thin and dense. Compared with foreign ship plate technology, the present invention has simple process control, does not need to modify the existing descaling system, has fast rolling rhythm, and increases the number of rolled ship plates per hour.

Contents of the invention

The purpose of the present invention is to provide a production method of anti-pitting blue steel for ship plate, improve the surface quality of ship plate, reduce the carry-over products caused by surface roughness, pitting, iron oxide scale pressing, etc., reduce production cost, and at the same time The performance meets the requirements of ship class regulations.

Ship plate anti-pitting blue steel general strength (A, B, D, E) ship plate according to the composition design of weight percent of the present invention is:

C: 0.15～0.18%, Si: 0.10～0.30%, Mn: 0.45～0.90%, Nb: 0.005～0.02%, Ti: 0.005～0.02%, S: ≤0.01%, P≤0.02%, Als: 0.020～ 0.04%, the balance is Fe and unavoidable impurities.

The components of high-strength (32kg, 36kg) ship plates are designed according to weight percentage:

C: 0.14～0.17%, Si: 0.20～0.30%, Mn: 1.30～1.50%, Nb: 0.015～0.04%, Ti: 0.005～0.02%, S: ≤0.005%, P≤0.02%, Als: 0.020～ 0.06%, the balance is Fe and unavoidable impurities.

Control the following technical parameters in the rolling process:

(1) The continuous casting thick slab smelted according to the above chemical composition design and process flow, after cleaning and inspection, put it into the slab heating furnace for heating. The heating temperature is 1160-1220 ℃, the heating time is 150-400min, and the residual oxygen is controlled at 1%. -6%, in order to reduce the thickness of oxide scale on the surface of the billet as much as possible; after the billet is released from the furnace, it is descaled once by high-pressure water, and the pressure of the high-pressure water is set at 19-21MPa to ensure the quality of the first-time descaler; then it enters the rolling mill for rolling.

(2) After the first descaling, the steel billet is rolled into the roughing mill, and the second descaling is opened in odd passes (the descaling box is located in front of the roughing mill) to prevent the unremoved iron scale from being pressed into the surface of the steel plate, and after rough rolling for 7 -9 passes, the reduction of each pass is 10-35mm, and the rough rolling grains are completely deformed through large reductions;

Immediately after rough rolling, finish rolling is carried out. The thickness of the finish rolling joint is 3-5 times the thickness of the finished steel plate, so that the finish rolling has a certain cumulative reduction. As the surface temperature drops, the oxide scale becomes brittle, and the finish rolling The stage reduction needs to be small, and the pass reduction is preferably 1-20mm. The start-rolling temperature of the finish rolling is controlled at 1000-950°C to ensure that the surface oxide scale has good ductility at high temperatures, and the surface temperature of the final-rolled steel plate Control the temperature at 920-980°C, so that the surface of the steel plate forms an iron oxide scale structure dominated by black and dense Fe ₃ O ₄ .

(3) The steel plate is cooled by laminar flow. The starting cooling temperature of the finished steel plate is 900-950°C, which is based on the final rolling temperature minus the temperature drop (30-50°C) from the finishing rolling to the entrance of the ACC; the final cooling temperature is set at 680-750°C, mainly in this temperature range The surface quality is better and more stable; the cooling rate is set at 6-10°C/s, and the low cooling rate is beneficial to obtain stable surface quality.

Advantages of the present invention: At present, this invention has been applied to the surface quality of ship plates. After the implementation of this new process, the problems such as rough surface of ship plates have been solved, and the surface quality of ship plates has been qualitatively improved, which meets the needs of shipyards. and shipowner's requirements.

Description of drawings

Figure 1 is a photo of the "red steel" ship plate.

Figure 2 is a photo of the ship plate "blue steel" produced by the new process.

Detailed ways

After rolling, the surface of the steel plate is blue-black, and the iron scale on the surface is uniform and dense. After the shot blasting inspection, there are no problems such as scale indentation and surface roughness on the surface, which shows that the determined ship plate rolling process is reasonable and can ensure smooth production.

Table 1 Heating and water cooling process parameters of steel plate

Table 2 The rolling process parameters of the trial steel plate

Table 3 The rolling process parameters of the trial steel plate

Table 4 The rolling process parameters of the trial steel plate

Table 5 The rolling process parameters of the trial steel plate

Claims (1)

1. the rolling method of the anti-spot corrosion blue steel of the deck of boat, the anti-spot corrosion blue steel of described deck of boat common intensity composition being designed to by weight percentage:

C:0.15～0.18%, Si:0.10～0.30%, Mn:0.45～0.90%, Nb:0.005～0.02%, Ti:0.005～0.02%, S :≤0.01%, P≤0.02%, Als:0.020～0.04%, surplus is Fe and unavoidable impurities;

HS composition being designed to by weight percentage:

C:0.14～0.17%, Si:0.20～0.30%, Mn:1.30～1.50%, Nb:0.015～0.04%, Ti:0.005～0.02%, S :≤0.005%, P≤0.02%, Als:0.020～0.06%, surplus is Fe and unavoidable impurities;

It is characterized in that the processing parameter of control is:

(1) continuous casting heavy slab of smelting by above chemical composition design, the bar plate heating stove heating of after clear inspection, packing into, Heating temperature is 1160～1220 ℃, heat-up time 150-400min, residual oxygen is controlled 1%-6%; Come out of the stove the back steel billet through a de-scaling of high pressure water, and high pressure water pressure is set at 19-21MPa, gets into mill milling then;

To advance roughing mill rolling for steel billet after (2) de-scalings, and odd-numbered pass is opened secondary descaling steel, and through the rolling 7-9 of roughing road, reduction in pass 10-35mm guarantees that through depressing greatly roughing crystal grain is badly deformed;

It is rolling that laggard finish rolling has been rolled in roughing; Finish rolling adapter thickness is 3-5 times of Finished Steel plate thickness, and reduction in pass 1-20mm, finish rolling start rolling temperature are controlled at 1000～950 ℃; Finish to gauge surface of steel plate temperature is controlled at 920～980 ℃, and surface of steel plate is formed with the fine and close Fe of black color ₃O ₄It is main scale structure;

(3) steel plate adopts the laminar flow cooling, and steel plate begins to cool down temperature 900-950 ℃, is temperature drop 30-50 ℃ deducting from finish rolling to the ACC entry process on the finishing temperature basis; Set 680～750 ℃ of final cooling temperatures, set 6～10 ℃/s of cooling rate.

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