Controlled rolling and cooling process of Q345E structural steel

In the national standard, the P and S requirements of Q345E structural steel are not very strict, but because the mechanical properties required by the user are higher than the national standard, the impact test is conducted at -40 ℃, so we strengthen the control of the purity of steel in smelting and production, and strictly control the content of P, S and Cu in the steel. Steel slag friends are added in batches in the whole process of refining to deoxidize and ensure sufficient refining time of white slag.

When the temperature and composition are appropriate, the ladle is put into VD, the vacuum cover is closed, and the vacuum pump is opened step by step. When the vacuum degree is appropriate, the ladle is kept for (20~25)min. In the process of vacuum holding, the mixing strength of molten steel is improved to ensure the degassing effect. After the release, an appropriate amount of aluminum wire is fed to ensure that the Alt of the finished product is 0.020%~0.035%, and enough soft blowing time is ensured before hoisting and pouring.

The strength and low temperature impact toughness of Q345E structural steel can be greatly improved by using controlled rolling and cooling process. The increase of the total deformation under 900 ℃ plays a role in refining the grain and improving the strength, so that the comprehensive performance of Q345E structural steel can meet the requirements of users.

The production of low alloy and high strength Q345E structural steel by controlled rolling and cooling process can meet the special requirements of users. The final rolling temperature was proved by experiment. 850 ℃ is conducive to the formation of equiaural massive ferrite, which can improve the low temperature impact toughness of Q345E structural steel. The increase of the total deformation under 900℃ plays a role in refining the grain and improving the strength.