SU910331A1 - Continuous casting machine secondary cooling zone - Google Patents

Description

I

This invention relates to ferrous metallurgy, in particular to continuous casting machines. . .

The closest to the technical essence of the invention is a continuous casting machine, the mold of which is made with a protrusion in the form of an arch on most of the wide walls, as a result of which, at the exit of the mold, billets receive an arched concave shape of the HP on wide edges. Such a cross section of the workpiece is able, together with the pressure of the support rollers located along the narrow faces of the workpiece, to keep the crust from bulging along the wide edges under the action of the ferrostatic pressure of the liquid steel, and the rollers are pressed against the workpiece with a force sufficient to prevent the expansion of the wide faces. The rollers mounted on the wide faces of the workpiece are in contact with it at the corners.

And serve only to center the workpiece.

The disadvantages of the design of the secondary cooling zone of a known machine design are that with an arch located on most of the wide faces of the workpiece, it is impossible to provide the arch deflection arrow set in the mold with the pressure of the side rollers. therefore

10, under the action of the ferrostatic pressure, the solidified crust of the billet begins to bulge over wide edges, which leads to a deterioration in the quality of the metal. Besides,

15 it is very difficult to constructively carry out support rooshki, whose pressing force to the workpiece would change with a change in the speed of pouring, surface temperature, brand

20 cast steel and cross-sectional dimensions of the workpiece. The purpose of the invention is to improve the quality of continuously cast 3

by eliminating the bulging of wide edges and increasing the durability of the rollers of the secondary cooling zone.

The goal is achieved by creating a secondary cooling zone in continuous casting machines, including support and pull rollers, mounted under the mold with a height of one roll on wide edges across the width of the workpiece in the upper part of the secondary cooling at a length of 0.35-0.7 lengths are stepped, and in the place of the protrusion on the mold the diameter of the rollers is two more heights of the protrusion, the width of the larger diameter is 0.2-0.9 of the width of the protrusion, and the rest of the zone has a secondary cooling made constant diameter

Fig, 1 shows the proposed device, a general view; in FIG. A-A in FIG. in FIG. 3 shows a section B-B in FIG. Ij in FIG. 4 shows a section B-B in FIG. one.

In the upper part of the secondary cooling somi of a continuous casting machine containing a mold I with protrusions 2 on wide walls 3 rollers 4 along the width of the workpiece 5 are made with steps of a larger diameter, and in the place of the projection 2 of mold I the diameter of the rollers is larger than in the place corresponding to the valleys 6 molds, two heights of the ledge of the mold, i.e. on 2Vi.

The length of the section of the secondary cooling zone with an increased diameter of the rollers at the protrusion on the mold is, depending on the grade of cast steel, 0.8-1.1 and the length of the liquid phase in the thinned part of the workpiece. 7, which is 0.35-0 , 7 secondary cooling zones. This interval is explained by the fact that some brands of steel at high temperatures have strength enough to crust the workpiece, having a thickness corresponding to 0.8 length of the liquid phase in the thinned part, resist the action of ferrostatic pressure and do not bulge without additional support hollows with rollers, at the same time there are steel grades

whose strength at temperatures close to the crystallization temperature is insufficient, therefore, the thinned part must be maintained after its complete solidification to eliminate the bulging. To a length equal to 1.1 times the length of the liquid phase in the thinned part, its temperature significantly decreases, and the strength of the steel increases so that the thinned part does not bulge without the support of its rollers,

So, for example, when casting steel St, 3, which has sufficient strength at high temperatures, into billets with a cross section of 150 X 1200 mm and a thinned part 120 mm at an operating speed of 0.9 m / min, the length of a section of the secondary cooling zone with increased roller diameter will be equal to:

, 8b 0,8-V., 8 0, 6 m,

where L is the length of the liquid phase in the thinned part;

V - pouring speed, equal to 0.9 m / min.

(GG, the hardening time of the thinned part is 5 minutes. When casting steel 10, which has insufficient strength at high temperatures, the length of the section with increased diameter of the rollers will be:

L 1.1 0.95g5 m

The step width is 0.20, 9 of the width of the protrusion of the mold. The upper limit is chosen based on the fact that when the rollers are installed in the machine, their longitudinal mixing is possible relative to each other. Therefore, with a width of steps exceeding 0.9 the width of the protrusion of the mold, a barrel with a large roller diameter can find a transition from a thick part of the workpiece to a thinned one, which is unacceptable in a normal process. The lower limit is selected from the condition that there is no bulging by the thinned part that is not supported by the roller. The width of the unsupported section 2 (Fig. 3) must not exceed the pitch of the rollers in the upper part of the secondary cooling zone, which is chosen so that there is no bulging of the crust

. between the rollers. The step of the rollers in the zero section of the secondary cooling zone. nor operating caster does not exceed 180 mm. So, for example, with a total width of the thinned part and transitions s mm and the width of the thinned part L 200, mm, the width of the steps will be 200X0, mm, and each non-supported section will be equal to 180 mm, Toy. does not exceed the pitch of rollers. YU

Below the section of rollers with different diameters have a section of smooth rollers 8 (Fig. 4), continuing to the end of the technological length of the continuous casting machine and in which 15 complete solidification of the billet at the maximum casting speed ends.

Such a design of the secondary cooling zone not only ensures that the crusts of the thinned part of the workpiece are kept from bulging, but also increases the durability of the rollers.

The use of rollers in the upper part of the secondary cooling zone with steps of a larger diameter in the middle part makes it possible to increase the moment of resistance in the most dangerous section of the roller. If, for example, the roller in the place corresponding to the protrusion of the mold has a diameter of 30,180 mm and the rest of the diameter is 150. mm (the height of the protrusion is 15 mm), then when the diameter increases by 1.2 times, the resistance moment in the dangerous section increases by 1 , 73 times at 35 of the same load acting on the roller. This contributes to the reduction of the bending of the roller and the reduction of stress in it.

It is known that the solidification time of 40 continuously cast billets is proportional. the square of its thickness. Therefore, the thinned part of the billet will harden much faster than the edges, and the length of the liquid phase 45 in it will be less than at the edges. Reducing the thickness of the billet in pinch by 20% will reduce

in it the length of the liquid phase is 1.56 times. After the thinned part solidifies, the forces on the rollers of the secondary cooling zone are significantly reduced. Thus, when casting on a vertical continuous casting machine of a billet with a section of 50 × 1200 mm at a speed of 0.9 m / min, the force per roller at a distance from the meniscus of 8.4 m is 15.5 m, and when casting a billet with a thinned middle part 120 mm After the solidification of the thinned part, the force on the roller at the same distance of 8.4 m from the meniscus is 9.8 tons, i.e. force decreases 1.58 times. Such a reduction in the force on the rollers makes it possible to significantly increase their durability.

Claims (1)

1. Patent of Germany No. 2144082, -. cl. In 22 D P / 12, 1968. . 3 fug. G ///////// y //////// 7Z fug.Z in-in 0ugh S 2/77777777.