Study On High Temperature Plastic And Static Transformation Rule Of Offshore Platform Steel E690

With the decrease of resources on land, various countries in the world have aimed at developing marine resources positively. It has a stringent requirements for the performance of the offshore platform as which operate in the environment hostile.The steel of E690 has the good function, which means it’s not only with ultra-high strength, but also has good plasticity, and it belongs to the ultra-high strength steel structure. By studying the plasticity at high temperature and the static transformation rules on E690 steel, this paper provide theoretical basis for the continuous casting process and steel rolling process.High temperature plasticity is the index of the crack sensitivity. Generally speaking, the better the high temperature plastic is, the less the amount of crack will be. By testing the plastic of E690 steel on the Gleeble-3800 thermal simulator at high temperature. This paper study the strength and shape curve at the temperature range of600~1350 ℃. The result shows that E690 steel has good high temperature plastic, and the sample has a plastic trough at 800~950 ℃. The plastic area of the sample is at950~1280 ℃. The first brittle zone of the sample is at 1280~1380 ℃. At the temperature range of 950~1100 ℃, the plastic sample increased significantly due to the dynamic recrystallization happens. As the formation of liquid film and the grain boundary area to the grain boundary of low melting point impurity such as sulfur,phosphorus, specimen cracking along grain boundary, a significant reduction in the sample of the plastic with the temperature higher than 1280 ℃. In order to ensure the high temperature plasticity of the steel which used in E690, the straightening temperature should be at 950~990 ℃ in production.After steel austenitized, the austenite will decompose in the cooling process. And the supercooled would austenite into different groups according to different mechanism under different transformation temperature. By testing the expansion of E690 steel on the Gleeble-3800 thermal simulator at high temperature, this paper study the phase change regularity of E690 steel. The experimental results show that the Ac1, Ac3 point E690 steel is 716 ℃, 827 ℃. In addition, with the Ms. Point of steel in this experiment is 364 ℃ respectively. With the cooling rate is lower than 0.1 ℃ / s,the product of the cooling transformation of ferrite and bainite(F + B). And with the cooling rate is 0.2, 0.5 ℃ / s, the product of the cooling transformation of ferrite,bainite and martensite.(F + B + M). Cooling rate of 1~3 ℃ / s, cooling products into pearlite, bainite and martensite(P + B + M). Cooling speed is greater than 5 ℃ / s,after the cooling result is bainite and martensite(B + M).