Controlling Method of Equiaxed Grain Ratio of 30crmo Round Tube Billet with φ280mm

Abstract

The invention discloses a method for controlling the equiaxial crystal ratio of a 30CrMo 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, RH refining and continuous casting of molten steel. The key technology of the method is a combination of mold electromagnetic stirring and final electromagnetic stirring are combined in the continuous casting stage. The method has the following beneficial effects: first of all, the purity of the molten steel is improved and the optimum tapping conditions of the molten steel can be achieved according to reasonable parameter control in the molten steel smelting stage; 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, a columnar crystal structure can be continuously scoured and fused in the stirring process, the equiaxial crystal nucleation ratio can be improved, the columnar crystal growth can be inhibited, and then the equiaxial crystal ratio of the circular tube steel casting blank can be improved.

Description

technical field [0001] The invention relates to the field of iron and steel metallurgy, in particular to a method for controlling the equiaxed crystal ratio of a 30CrMo round tubular steel billet with a section of φ280 mm. Background technique [0002] 30CrMo billet steel is mainly used for the production of steel for oil well pipes 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 ...

AI Technical Summary

Problems solved by technology

[0003] For 30CrMo tube billet steel, the high chromium and molybdenum content in the steel composition itself determines that the columnar crystals of the cast slab have a relatively large development trend. Moreover, because the cast slab has a relatively large section and is a round billet, its specific surface area is small. The heat transfer efficiency of the slab is lower, the solidification and cooling are slow, and the control of the crystallization structure is more difficult. Therefore, for different sizes of round tube billets, the methods for controlling the equiaxed crystal ratio are also different.