Method for producing a hot strip by means of strip casting with material properties adjustable across the strip cross-section

Abstract

In a method for producing a hot strip of steel with material properties that are adjustable over the strip cross-section, a steel melt is fed onto a revolving casting belt of a horizontal strip casting facility and solidifies to form a pre-strip having a thickness between 6 and 20 mm, and the pre-strip is subjected to a hot rolling process after complete solidification. A gas jet or plasma jet composed of metallic and/or non-metallic elements that affect the material properties of the hot strip influences the steel melt that is still liquid and/or just about to start to solidify. The concentration of the elements introduced into the melt by the gas jet or plasma jet and diffusing into the melt is adjusted across the strip thickness and strip width by changing the influencing kinetic energy of the gas jet or plasma jet, the partial gas pressure and/or the applied temperature.

Claims

1. A method for producing a hot strip of steel, comprising: feeding a steel melt onto a revolving casting belt of a horizontal strip casting facility; directing a plasma jet composed of metallic and/or non-metallic elements upon the steel melt while the steel melt is still liquid and/or just about to start to solidify; adjusting a kinetic energy of the plasma jet to thereby change a concentration of the metallic and/or non-metallic elements being introduced into the steel melt by the plasma jet so as to influence a material property of the steel melt across a thickness and width of the steel melt; allowing the steel melt to fully solidify to form a pre-strip; and subjecting the pre-strip to a hot rolling process after complete solidification.

2. The method of claim 1, further comprising adding solid particles to the plasma jet.

3. The method of claim 1, wherein the material properties are adjusted symmetrically or asymmetrically across the width of the steel melt.

4. The method of claim 1, wherein the material properties are additionally adjusted in a variable manner across a cast length of the steel melt.

5. The method of claim 1, wherein a targeted impact on still liquid marginal zones of the steel melt with the plasma jet affects a shape of edges of the steel melt during the course of solidification.

6. The method of claim 1, wherein the pre-strip has a thickness between 6 and 20 mm.

7. A method for producing a hot strip of steel, comprising: feeding a steel melt onto a revolving casting belt of a horizontal strip casting facility; directing a gas jet composed of metallic and/or non-metallic elements upon the steel melt while the steel melt is still liquid and/or just about to start to solidify; adjusting a kinetic energy of the gas jet to thereby change a concentration of the metallic and/or non-metallic elements being introduced into the steel melt by the gas jet so as to influence a material property of the steel melt across a thickness and width of the steel melt; allowing the steel melt to fully solidify to form a pre-strip; and subjecting the pre-strip to a hot rolling process after complete solidification.

8. The method of claim 7, wherein the gas jet is composed of a gas which is inert and/or reducing.

9. The method of claim 7, wherein the gas jet is composed of a mixed gas made of an inert gas as carrier and a reducing gas.

10. The method of claim 7, wherein the gas jet is composed of a gas which is cold or preheated.

11. The method of claim 7, wherein the pre-strip has a thickness between 6 and 20 mm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The method according to the invention will be described in greater detail with reference to a drawing, in which:

(2) FIG. 1 shows the schematic illustration of a horizontal strip casting facility with impact points for the gas jet or plasma jets for influencing the material properties,

(3) FIG. 2 shows adjustable concentrations or element distributions across the sheet thickness.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) FIG. 1 shows by way of the schematic illustration of a horizontal strip casting facility the possible impact points for the gas jet or plasma jets for targeted influencing the material properties of the steel strip.

(5) A melting vessel 1 is shown from which the liquid steel melt 8 is fed via a feed vessel 2 to a casting channel 3 so that the melt 8 is deposited by a casting nozzle 4 onto a casting belt 5 revolving about a leading deflection roller 6 and a trailing deflection roller 7. The casting belt 5 is supported between the deflection rollers 6 and 7 by support rollers 9 between which cooling nozzles 10 are arranged for cooling the belt. The depicted rotation arrows at the deflection rollers 6 and 7 designate the transport direction of the solidified casting strand 11.

(6) The possible impact points of the gas jet or plasma jet upon the casting strand are labeled with I and II.

(7) At the impact point I, the melt is still liquid even on the strand surface. As a result of the penetration of the transport medium (e.g. by means of the gas jet or plasma jet) into the still liquid melt bath, the melt is inoculated with gaseous/vaporous metallic and/or non-metallic elements and thoroughly mixed in the melt in a controlled manner as a result of the flows generated by pressure applied by the transport medium upon the melt. The thus attained greater surface and creation of new surfaces leads to an increase in particle amounts that can be diffused in.

(8) Using a downstream electromagnetic transverse agitator in casting direction enables an additional thorough mixing through dispersing the already diffused particles and the increase of diffused amount as a result of the creation of new surfaces.

(9) In the area of the impact point II, the surface of the casting strand has already started to solidify. The porously kept surface allows diffusion of atoms, which are separated at this spot from the transport medium (e.g. gases or vapors), from the surface into the solid material.

(10) Impact of the strip by the gas jet or plasma jets may take place either at one of the two impact points or jointly on both in a time-staggered or simultaneous manner.

(11) Through additional variable impact across strip width and strip length, a wide variety of requirements with respect to required material properties can be realized. Thus, the material properties and the later component properties in the strip can virtually be adjusted at precise locations.

(12) The described application positions allow adjustment of the concentrations and distributions across the strip width as illustrated in FIG. 2:

(13) Application Position I.fwdarw.Distribution A):

(14) Gradient materials with steadily unilateral surface gradient. This gradient established by the diffusion can be adjusted by the kinetic energy of the gas jet or plasma jet, the partial gas pressure as the applied temperature (diffusion velocity in temperature-dependent).

(15) Application Position II.fwdarw.Distribution B):

(16) Composite materials with unilateral sudden change in distribution on the outside.