E36 shipbuilding steel plate is belong to our Hot Rolled Steel Plate catalog.
1. E36 shipbuilding steel plate production process
Hot molten iron pre-treatment–120t top bottom blown converter–LF / VD refining–continuous casting–heating–phosphorus removal–rolling–ACC cooling–normalized–finishing–stock.
2. E36 shipbuilding steel plate chemical composition
E36 high-strength ship plate steel not only requires a higher strength at the same time on the low temperature (a 40℃) impact toughness and welding performance is also higher.Therefore, taking the micro-alloying to improve the purity of steel and excellent chemical control rolling and cooling technology is the main basis for produce E36 steel.
According to low-alloy high-strength steel design concept, modern welding structure requires low alloy high strength steel with lower carbon content and can be adapted to the site welding conditions.Welds and welding heat affected zone area minimum notch toughness and maximum hardness should meet the new requirements.
Shipbuilding Steel Plates
In order to ensure good weldability and low temperature impact toughness, it is necessary to reduce the carbon content and carbon equivalent in the steel, requiring the carbon equivalent of E36 to be less than 0.38. Where: Ceq (%) = C+ 1 / 6Mn + (Cr + Mo + v) / 5 + (Ni + Cu) / 15.
In ensuring good low-temperature tenacity, through micro-alloyed and optimization of controlled rolling and cooling processes to enhance the strength of steel sheets. The core component of the process design stage of E36 ship plate is how to grain refinement. Proper addition of Ni to the steel ensures a good low-temperature toughness of the steel, while increasing the content of Mn, through its solid solution can increase the strength of the steel plate appropriately. In addition, by adding an appropriate amount of micro alloying element Nb, precipitation of fine Nb (C, N) to grain boundary during hot rolling improves the re-crystallization termination temperature, to offers a higher, wider temperature range for the steel rolling. And at lower than the austenite re-crystallization temperature to a certain deformation of the steel, it will produce no re-crystallization of the “pancake-shaped grain”. In the subsequent austenite to ferrite transformation process, it is easier to get fine ferrite grains, improve the strength and toughness of steel.
3.controls inclusions and steel purity
Shipbuilding steel plate has a high request on steel chemical composition, mechanical properties, and processing performance. Especially high-grade ship plate has high requirements on the organization of steel uniformity, strength, low-temperature impact toughness. this must to improve the purity of molten steel, reduce the inclusion of steel, while the control older debris in order to improve the plasticity of steel, toughness, and elongation.
3.1 steel purity control
First, determine the reasonable end point of carbon content, take the enhanced stir mix, improve the level of and control, reduce the end of oxygen content. Secondly, the key to solving the problem is debris in the de-oxidation process, which need to control converter slag and the amount of ladle tail slag reform, in the furnace after the feeding of aluminum, quickly reduce the oxygen content in the steel and ladle slag, and then through the soft blow and long town static, to promote the floating of the inclusions. LF and VD refining process to further reduce the slag oxidation, improve the slag Alkalinity, and feed calcium oxide on the oxide denaturation, the formation of liquid inclusions, with a reasonable argon stirring to further promote the floating and absorption of inclusions to improve The purity of the molten steel and the lower oxygen content in the ladle. The continuous casting process is mainly to prevent secondary oxidation and further purification, for which the use of large-capacity tundish (25t), the whole process of argon protection pouring, high alkalinity in the cover agent to promote the further reduction of inclusions to improve the purity of molten steel.
In order to deep de-sulfurization, the first should reduce the amount of converter slag slag, LF rapid slag to create good conditions. In the process of tapping through the ladle slag reform and strengthen the molten steel de-oxidation, so that refining ahead of time. Through the ladle slag reform and strengthen the molten steel deoxidation, so that refining ahead of time. LF refining to choose a reasonable slag, slag MnO + FeO content of less than 2% To meet the slag deoxidation, desulfurization of the necessary conditions, while slag basicity controls the 4.0 or so, the MI index is between 0.31 and 0.34, to make good thermodynamics and kinetic conditions. Under the VD vacuum, a large amount of argon blowing is used to further improve the desulfurization kinetics of molten steel. The use of large-capacity tundish to promote the floating of the inclusions. The mass fraction of sulfur in tundish is less than 0.003%, which meets the requirements of high-quality ship plate steel and improves the low-temperature impact toughness of ship plate steel. The slab purity control level in the sheet:
3.2 Ingredients, morphology and quantity of inclusions in slabs
Calcium treatment technology to control the composition and morphology of inclusions in steel, so that the residual calcium content of tundish steel in the 15 × 10-6 or more, to obtain a higher Ca / A1 and Ca / S value, so that the molten steelA1O, inclusions degeneration is more complete. At the same time, the mass fraction of sulfur in the molten steel is controlled below 0.003%. The residual sulfur in the steel will be distributed in the steel in the form of calcium sulfide particles, so as to improve the quality of the product.
4 Shipbuilding plate rolling process control
The TMCP process is a forming process, its final deformation process is carried out in a specific temperature range.In the first rolling stage (rough rolling), the austenite grains are coarsened by heat, and are gradually refined due to the constant deformation and recrystallization process. In order to achieve complete recrystallization, the austenitic rough rolling should be finished at 950 ° C or more to make. The second rolling stage, at finishing stage non-recrystallization region of austenite, resulting in the phase of rolling of the recrystallized grains formed with an elongated deformation. After the phase change, the formation of a very fine grain of the ferrite, so that you can get good strength and toughness. According to the required strength and toughness, in the first stage, the slab is rolled to the most 2.5 to 4 times the finished product thickness, and the middle billet is cooled to about 950℃ after the start of the second stage rolling and rolling into the final finished product thickness.
The recrystallized austenite is controlled when cooled by ferrite certain degree of grain refinement, but the effect is not significant. If the un-recrystallized austenite is controlled to cool, not only after deformations austenite crystal interface can also be produced in the deformed zone nuclei in Austrian Body grains also produce ferrite nuclei, to achieve a substantial ferrite-grain refinement.
The steel plate is rolled in the last pass of finished rolling road transport directly into the ACC device, the plate through the ACC device,The upper and lower sides of the water at the same time for rapid cooling, so that the temperature of the steel plate about 700℃ ~ 800℃ (ie, austenite or biphase) rapid decline 600C a 650℃ (ACC control cooling). Thickness at 25mmAbove the steel plate, through the ACC device speed of about 0.3 ~1.0m / s; for the thickness of less than 25mm of steel, through the speedUp to 3.0m / s. Straightening temperature is generally controlled at 600℃ above, and then in the 600℃~ 400℃ between the slow, so that the steel ferrite easy to precipitate, avoid free time tendency, resulting in cold-formed substandard, impact toughness decreased.
5 Mechanical properties of ship plate
After the plate rolling mill using controlled rolling and cooling technology after rolling, the ship plate strength and elongation are to meet the national standard requirements, the mechanical properties:
Low-temperature impact toughness is the main reason for the quality of high-grade ship plate steel primer. According to the performance of steel after rolling inspection situation, the use of this workout production slab can meet the quality requirements of high-grade ship plate steel.
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