Control Method of Center Segregation of 30crmo Round Tube Billet Steel Slab

Abstract

The invention relates to the field of ferrous metallurgy, in particular to a center segregation control method for a 30 CrMo circular tube blank and a 30 CrMo steel casting blank. The center segregation control method for the 30 CrMo circular tube blank and the 30 CrMo steel casting blank can improve center segregation parameter control and includes the following steps that a, a converter smelting process is implemented; b, an LF molten steel refining process is implemented; c, an RH refining process is implemented; and d, a molten steel continuous casting process is implemented, wherein the stirring current of a crystallizer electromagnetic stirrer ranges from 350 A to 400 A, the frequency ranges from 2 Hz to 4 Hz, parameters of a solidification final stage electromagnetic stirrer are characterized in that the stirring current ranges from 200 A to 300 A, the frequency ranges from 6.0 Hz to 8.0 Hz, the superheat degree control scope ranges from 15 DEG C to 35 DEG C, the pulling rate is controlled to range from 0.75 m / min to 1.00 m / min, and the secondary cooling specific water amount is controlled to range from 0.21 to 0.29 per kilometer of steel. Growth of columnar crystals is restrained, and control of center segregation parameters is improved. The center segregation control method is particularly suitable for producing the 30 CrMo circular tube blank and the 30 CrMo steel casting blank with the cross section phi being 350 mm.

Description

technical field [0001] The invention relates to the field of iron and steel metallurgy, in particular to a method for controlling the center segregation of a 30CrMo round billet steel casting slab. 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, often causing problems such as production leakage, which is harmful to production and adverse effects on the environm...

AI Technical Summary

Problems solved by technology

However, for the production of large-scale 30CrMo round tube blanks with a φ350mm cross-section, the specific methods for controlling the equiaxed crystal ratio and improving the uniformity and compactness of the solidified structure of the slab have not been involved.