Controlling Method of Equiaxed Grain Ratio of 35crmo Round Tube Billet with φ280mm

Abstract

The invention discloses an equiaxial crystal ratio control method for producing a 35CrMo round pipe steel slab with the section being phi 280 mm in the metallurgical field. The method comprises the steps of converter smelting, LF furnace molten steel refining, RH refining, molten steel continuous casting and the like. According to the key technology, in the continuous casting state, a technology combining mould electromagnetic stirring with solidification end electromagnetic stirring is adopted. The method comprises the beneficial effects that firstly, in the molten steel smelting stage, according to reasonable parameter control, the purity degree of molten steel is improved, the outbound condition of the molten steel reaches the optimum, then, in the molten steel pouring process, a manner combining mould electromagnetic stirring with solidification end electromagnetic stirring is adopted, molten steel ingredient and temperature uniformization is achieved, a billet shell evenly grows, in the stirring process, a column crystal structure is continuously scoured and fused, the equiaxial crystal nucleation rate is improved, growth of column crystals is restrained, and therefore the equiaxial crystal ratio of a casting blank is 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 35CrMo round tubular steel billet with a section of φ280 mm. Background technique [0002] 35CrMo tube billet steel is mainly used to produce steel for oil well pipes used in oil and gas exploitation and transportation. ≤0.018%, S≤0.010%, Cr: 0.85%~1.05%, Mo: 0.17%~0.24%, Cu≤0.15%, Ni≤0.20%, residual element requirements: As≤0.030%, Sn≤0.010%, And V+Nb+Ti+B+Zr≤0.15%; As+Sn+Pb+Sb+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 environment. With the development of society and economy, the development trends...

AI Technical Summary

Problems solved by technology

[0003] For 35CrMo 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 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.