RU2348479C2 - Pouring practice of rail steel at engine of continuous casting of blanks - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: from interim ladle steel is fed into composite mold and poured with speed 0.45-0.60 m/min. Steel temperature in interim ladle is higher than the liquidus temperature for 5-35°C. Crystalliser contains cooling plates with vertical ribs in area of plates joint. Cathetus a and b, forming ribs are in ratio a/b=1:(1.0-1.3). Ratio of small cathetus a to small side h of crystalliser is 1:(15-20), ratio of big cathetus b to big side l of crystallizer is 1:(18-24), and ratio of small side h to big side l of crystalliser is 1:1.2. Total area of crystalliser is 1075-1080 cm². Dimensions of crystalliser, located in limits of declared ratios, allows reduction of surface defect of uninterruptedly-casted blanks.

EFFECT: steadfastness increasing of crystalliser and increasing of continuous caster productivity, improving of macrostructure of casted uninterruptedly-casted blanks.

1 dwg

Description

The invention relates to ferrous metallurgy, and more particularly to methods for continuous casting of rail steel.

Known methods for continuous casting of steel on continuous casting machines in the mold box type [1]. However, the use of molds with right angles leads to the formation of surface defects in the corners on continuously cast billets in the form of “inversions of the crust” and transverse cracks.

Also known is a mold for forming an ingot containing cooled plates with vertical ribs in the joint zone of the plates, while the vertical ribs are made dihedral with a vertex of 0.02-0.10 cross-sections of the working cavity of the mold, the plates being joined along the surface of one face, and the other face forms the working surface of the mold in the joint zone [2].

The disadvantages of the method of casting in this mold is the low resistance of the ribs on the working surfaces of the ribs at the junction in connection with the claimed scheme of connecting the ribs and the formation on the surface of continuously cast billets "gaps" and cracks associated with erosion of the mold in the ribs.

The closest in technical essence is the method of casting rail steel on a continuous casting machine, comprising supplying steel to a composite mold containing cooled plates with vertical ribs forming beveled corners in the joint zone of the plates, characterized in that they use a composite mold in which the legs are a , b, forming the ribs, are in the ratio 1: (1.5-2), and the ratio of the small leg a, forming the vertical ribs, to the small side h of the mold is 1: (50-60), and the ratio is large leg b, forming the vertical ribs to the large side of the mold l is 1: (30-33); the ratio of the small side h to the large side l of the mold is 1: 1.1, and the steel is cast at a casting speed of 0.5-0.65 m / min and the steel temperature in the intermediate ladle is 10-45 ° C higher than the liquidus temperature - prototype [3].

Significant disadvantages of this method are:

- low productivity of casting due to the small size of the cross-sectional area of the mold;

- increased rejection after rolling the resulting continuously cast billets on surface defects due to the irrationally selected ratio of legs;

- reduced mold resistance in connection with the selected size ratios of the mold;

- poor macrostructure of continuously cast billets due to the irrational aspect ratio of the mold, casting speed and overheating of steel over the liquidus temperature in the intermediate ladle.

The desired technical results of the invention are an increase in the productivity of continuous casting machines, a decrease in the rejection of continuously cast billets for surface defects, an increase in the mold resistance, an improvement in the macrostructure of cast continuously cast billets.

A diagram of a composite mold for the continuous casting of billets is shown in the drawing.

To this end, a method is proposed for casting rail steel on a continuous casting machine, comprising supplying steel to a composite mold containing cooled plates with vertical ribs, which are formed by legs a and b, forming beveled corners in the joint zone of the plates, in which steel is cast at a speed of 0 , 45-0.60 m / min at a steel temperature in the intermediate ladle higher than the liquidus temperature by 5-35 ° C, while casting is carried out using a mold, the ratio of legs a / b of which is 1: (1.0-1, 3), the ratio of the small side a to the small side h of the mold is 1: (15-20), the ratio of the large side b to the large side l of the mold is 1: (18-24), and the ratio of the small side h to the large side l of the mold is 1: 1.2 with a total mold area of 1075-1080 cm ² .

The claimed limits are selected experimentally.

The change in the ratio of legs, forming vertical edges a / b 1: (1.0-1.3), leads to the formation of surface defects on continuously cast billets in the form of “inversions of crusts” and cracks.

The change in the deviations of the small leg a, forming vertical ribs to the small side of the mold h 1: (15 ÷ 20), leads to the formation of angular cracks on the surface of continuously cast billets.

The change in the ratio of the large leg b, forming vertical ribs to the large side of the mold l 1: (18 ÷ 24), also leads to the formation of angular cracks on the surface of continuously cast billets.

Changing the ratio of the small side h to the large side l of the mold 1: 1.2 with a total mold area of 1075-1080 cm ² does not allow for a good study of the metal structure during rolling of the rails and leads to a decrease in the quality of the macrostructure of the rails. The selected ratio also allows to increase the resistance of the molds and provides an increase in casting productivity.

The casting speed of 0.45-0.60 m / min and the reduced temperature of the metal in the intermediate ladle (higher than the liquidus temperature by 5-35 ° C) compared with the prototype allows to improve the macrostructure of continuously cast billets.

The inventive method of casting was tested on a 4-groove radial caster with a mold section of 300 × 360 mm when casting a vanadium-containing rail steel grade E76F. The mold was used with the following parameters: leg a - 15 mm, leg b - 10 mm, small side h - 300 mm, large side l - 360 mm, total mold area - 1075-1080 cm ² . The casting speed according to the technology varied from 0.45 to 0.60 m / min at a temperature in the intermediate ladle of 1475-1495 ° C. Using the proposed method allowed to increase the casting capacity of continuously cast billets while significantly improving the quality of the macrostructure and surface of the continuously cast billet. The application of the inventive technology allowed to reduce the number of rejected continuously cast billets on surface defects such as “crust inversion” and transverse cracks by 0.9% (against 0.7% in the prototype). The resistance of the mold to regrinding is 140-180 heats (with 110-120 heats in the prototype). The output of rails of l grade in the length of 25 meters increased by 2.6% (in the prototype - by 1.5%). CCM productivity increased by 7-9%.

Information sources

1. Popandopulo I.K., Mikhnevich Yu.V. Continuous casting of steel - M .: Metallurgy, 1990. - 296 p.

2. A.S. 923727, cl. B22D 11/04.

3. Pat. 2264885, B22D 11/00, 11/04.

Claims (1)

A method of casting rail steel on a continuous casting machine, comprising supplying steel to a composite mold containing cooled plates with vertical ribs formed by legs a and b forming oblique corners in the joint zone of the plates, characterized in that the steel is cast at a speed of 0, 45-0.60 m / min at a steel temperature in the intermediate ladle higher than the liquidus temperature by 5-35 ° C, while casting is carried out using a mold, the ratio of legs a / b of which is 1: (1.0-1.3) relation the small side a to the small side h of the mold is 1: (15-20), the ratio of the large side b to the large side l of the mold is 1: (18-24), and the ratio of the small side h to the large side l of the mold is 1: 1, 2 with a total mold area of 1075-1080 cm ² .