Method for controlling blank casting quality of phi-280mm 30Mn circular tube blank

Abstract

The invention discloses a method for controlling the internal quality of a 30Mn circular tube steel casting blank with a phi-280mm production section, and belongs to the field of metallurgy. The method comprises the steps such as smelting in a converter, molten steel refining in an LF furnace, continuous casting of molten steel. First of all, the purity of the molten steel is improved according to reasonable parameter control in the molten steel smelting stage, and the high-temperature plasticity of the molten steel is improved and the steel grade crack sensitivity is lowered after the molten steel is subjected to titanium microalloying; and then, mold electromagnetic stirring and final electromagnetic stirring are combined in the molten steel pouring stage, so that component and temperature homogenization of the molten steel can be achieved, the shell of the circular tube steel casting blank can grow uniformly, the solidification structure of the circular tube steel casting blank can be effectively improved, the loose level can be raised, the area of an equiaxial crystal region can be enlarged, the compactness of the central region of the circular tube steel casting blank can be effectively improved, the crack defect of the circular tube steel casting blank can be effectively controlled, the surface non-clearing rate can be improved, and the quality of such a rolled product can be controlled well and stably.

Description

technical field [0001] The invention relates to the field of iron and steel metallurgy, in particular to a quality control method for producing 30Mn round tube blanks with a cross-section of φ280mm. Background technique [0002] 30Mn pipe billet steel is mainly used for the production of oil well pipe steel used in oil and gas exploitation and transportation. P≤0.020%, S≤0.010%, V≤0.015%, Cr: 0.85%~1.05%, Mo: 0.17%~0.24%, Cu≤0.15%, Ni≤0.20%, Alt: 0.020%~0.040%, Residual element requirements: Nb≤0.010%, Ti≤0.010%, B≤0.005%, and V+Nb+Ti+B+Zr≤0.15%; As≤0.015%, Sn≤0.010%, Sb≤0.010%, Pb≤0.008 %, Bi≤0.010%, and As+Sn+Sb+Pb+Bi≤0.045%, and the balance is Fe. Under the joint action of stress and hydrogen sulfide gas during use, brittle fracture (called hydrogen sulfide stress corrosion) will occur suddenly when the stress is much lower than its own yield strength, which will easily cause problems such as production leakage, which is harmful to production and adverse effects on the...

AI Technical Summary

Problems solved by technology

Mainly due to the low thermal conductivity and large linear expansion coefficient of the steel type, large internal stress is generated during cooling and solidification, and surface crack defects are prone to occur; moreover, due to the relatively large cross-section of the billet and the round billet, its specific surface area is smaller. The billet has lower heat transfer efficiency and slow solidification and cooling. After the billet shell is formed, the heat transfer efficiency will decrease, which will lead to a larger radial temperature gradient in the cross-section of the billet, and the heat transfer direction will be prominent, which will further lead to the development of columnar crystals and a relatively low equiaxed crystal ratio. low trend