Abstract: A control process of inclusions in ultra-clean rare earth steel, wherein the content of rare earth elements REM in the ultra-clean rare earth steel, the total oxygen content T[O]m, the total sulfur content T[S]m in the steel, and the total oxygen content T[O]r in a rare earth metal or alloy added to the steel are controlled to satisfy the following formula: ?500<REM?(m*T[O]m+n*T[O]r+k*T[S]m)<?30, where REM is the content of rare earth elements in the steel, in ppm; T[O]m is the total oxygen content in the steel, in ppm; T[O]r is the total oxygen content in a rare earth metal or alloy added to the steel, in ppm; T[S]m is the total sulfur content in the steel, in ppm; m is a first correction coefficient, with a value of 2-4.5;n is a second correction coefficient; and k is a third correction coefficient.

Abstract: Provided in the present application are a rare-earth microalloyed steel and a control process. The steel has a special microstructure, and the microstructure comprises a rare earth-rich nanocluster having a diameter of 1-50 nm. The nanocluster has the same crystal structure type as a matrix. The rare earth-rich nanocluster inhibits the segregation of the elements S, P and As on a grain boundary, and obviously improves the fatigue life of the steel. In addition, a rare-earth solid solution also directly affects a phase change dynamics process so that the diffusion-type phase change starting temperature in the steel changes at least to 2° C., and even changes to 40-60° C. in some kinds of steel, thereby greatly improving the mechanical properties thereof, and providing a foundation for the development of more kinds of high-performance steel.

Abstract: Provided in the present application are a rare-earth microalloyed steel and a control process. The steel has a special microstructure, and the microstructure comprises a rare earth-rich nanocluster having a diameter of 1-50 nm. The nanocluster has the same crystal structure type as a matrix. The rare earth-rich nanocluster inhibits the segregation of the elements S, P and As on a grain boundary, and obviously improves the fatigue life of the steel. In addition, a rare-earth solid solution also directly affects a phase change dynamics process so that the diffusion-type phase change starting temperature in the steel changes at least to 2° C., and even changes to 40-60° C. in some kinds of steel, thereby greatly improving the mechanical properties thereof, and providing a foundation for the development of more kinds of high-performance steel.

Abstract: Provided are an ultra-clean rare earth steel and an occluded foreign substance modification control method, the steel includes 10-200 ppm of rare earth elements, 50% or more occluded foreign substances in the steel are dispersed into RE-oxygen-sulfide with the average equivalent diameter Dmean ranging from 1-5 ?m in a spherical shape or a substantially spherical shape or a granular shape; according to the method, at least 80%, preferably at least 90%, of Al2O3 occluded foreign substances in the steel are modified into RE-oxygen-sulfide, compared with steel with the same components without rare earth, the total amount of the occluded foreign substances in the steel is reduced by 18% or higher, the cracking probability caused by occluded foreign substances such as Al2O3 in traditional pure steel is reduced, the mechanical performance such as the fatigue life of the steel is remarkably improved.

Abstract: A constructing-and-forging method for preparing homogenized forged pieces comprises: preparing preformed billets: cutting off a plurality of continuous casting billets, milling and smoothing surfaces of the billets to be welded, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces in a vacuum chamber by electron beam welding; forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are at the same level as those of the bodies of the billets. Cheap continuous casting billets are stacked and forge welded.

Abstract: A constructing-and-forging method for preparing homogenized forged pieces comprises: preparing preformed billets: cutting off a plurality of continuous casting billets, milling and smoothing surfaces of the billets to be welded, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces in a vacuum chamber by electron beam welding; forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are at the same level as those of the bodies of the billets. Cheap continuous casting billets are stacked and forge welded.

Abstract: A constructing-and-forging method for preparing homogenized forged pieces comprises: preparing preformed billets: cutting off a plurality of continuous casting billets, milling and smoothing surfaces of the billets to be welded, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces in a vacuum chamber by electron beam welding; forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are at the same level as those of the bodies of the billets. Cheap continuous casting billets are stacked and forge welded.

Abstract: A constructing-and-forging method for preparing homogenized forged pieces comprises: preparing preformed billets: cutting off a plurality of continuous casting billets, milling and smoothing surfaces of the billets to be welded, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces in a vacuum chamber by electron beam welding; forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are at the same level as those of the bodies of the billets. Cheap continuous casting billets are stacked and forge welded.

Abstract: A method for controlling A-shaped segregation of steel ingot. The method includes: 1) controlling a content of phosphorus in liquid steel at less than or equal to 0.005 wt. % upon tapping from an electric furnace, preventing steel slag from entering a ladle, controlling content of harmful elements at less than or equal to 100 ppm; and adding between 3 and 15 kg of calcium oxide and less than or equal to 0.5 kg of aluminum to each ton of the liquid steel; 2) pre-deoxidizing the liquid metal using vacuum carbon deoxidation; 3) de-sulfurizing, controlling content of oxygen, and controlling the content of sulfur in the liquid steel at less than or equal to 0.005 wt. %; and 4) performing vacuum degasification, controlling the total oxygen content at less than or equal to 15 ppm; and casting the steel in the presence of inert gas or in vacuum.

Abstract: A method for controlling A-shaped segregation of steel ingot. The method includes: 1) controlling a content of phosphorus in liquid steel at less than or equal to 0.005 wt. % upon tapping from an electric furnace, preventing steel slag from entering a ladle, controlling content of harmful elements at less than or equal to 100 ppm; and adding between 3 and 15 kg of calcium oxide and less than or equal to 0.5 kg of aluminum to each ton of the liquid steel; 2) pre-deoxidizing the liquid metal using vacuum carbon deoxidation; 3) de-sulfurizing, controlling content of oxygen, and controlling the content of sulfur in the liquid steel at less than or equal to 0.005 wt. %; and 4) performing vacuum degasification, controlling the total oxygen content at less than or equal to 15 ppm; and casting the steel in the presence of inert gas or in vacuum.

Abstract: The present invention relates to the field of casting blank manufacturing, in particular to a method for enhancing the self-feeding ability of a heavy section casting blank, which can solve the problems of poor centre quality, surface crack and high rejection rate of the heavy section casting blanks in the prior art.