JPS5815221B2 - Continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting method, and in particular to a casting rotary ring equipped with a casting groove on its outer periphery, which is suitable for application to continuous casting of alloys, and This invention relates to an improvement in a continuous casting method in which molten metal is injected into a moving mold space composed of a metal belt covering a part of a casting groove, and an ingot whose outer surface has solidified at least is continuously pulled out by a pinch roller for drawing out the ingot. .

BACKGROUND OF THE INVENTION In continuous casting methods for molten alloys, it has been known and practiced for some time to use a belt caster consisting of a rotating wheel and a moving metal belt.

In other words, in this method, a groove is provided on the outer periphery of the rotating casting wheel, a part of which is covered with an endless metal belt to form a mold space, and molten alloy is injected between the grooves to form a solidified shell one after another. The ingot is pulled out by rollers.

However, this method often causes cracks inside the ingot, which impairs the subsequent rolling process, and it cannot be said that sufficient productivity is achieved.

This point will be explained in detail.

Figure 1 shows a conventional continuous casting method using a rotating wheel and a moving metal belt, in which the molten alloy 2 held in a kundish 1 is passed through a rotating casting wheel 3 with a casting groove on its outer periphery. , is injected into a mold space constituted by an endless metal belt 4 which is appropriately tensioned by a pulley 5,
It is cooled by the rotating ring and metal belt to form a solidified shell 6, and the thickness of the solidified shell gradually increases, and its rotational circumferential speed is kept equal to the moving speed of the mold composed of the rotating ring and metal belt. After being straightened and straightened by pinch rollers 7, the ingot is pulled out and finally becomes an ingot 8 whose interior has been completely solidified and is used for subsequent processing.

Therefore, at the point a where the ingot containing molten metal leaves the movable mold composed of the rotating ring 3 and the metal belt 4 and is corrected by the pinch roller 7, the thickness of the solidified shell 6 is equal to the number of ingot sizes. %, and if straightening is performed under such conditions, a rapid tensile deformation strain will be applied to the inner surface of the solidified shell on the molten metal side, causing cracks to occur, resulting in an ingot with poor internal quality.

One method has been proposed to improve the above drawbacks.

In this method, the point at which the ingot containing molten metal leaves the movable mold consisting of a rotating ring and a metal belt is placed above the position a in the above embodiment, and then the ingot is sequentially straightened using a higher-order curve. It is then pulled out by a pinch roller that rotates at the same speed as the moving mold.

However, in this method, the thickness of the solidified shell at the point of separation from the movable mold is even thinner than in the above embodiment, and even if straightening is performed sequentially using a higher-order curve in this state, tensile strain will occur at the solidified interface. is applied, causing cracks, and the effect is not sufficient to continuously obtain ingots with sound internal quality.

The present invention was made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a continuous casting method that can stably and continuously obtain an ingot having a sound internal quality without cracks.

The present invention injects molten metal into a movable mold space composed of a rotating casting wheel with a casting groove on the outer periphery and a metal belt covering a part of the casting groove of the rotating wheel, and at least the outer surface of the casting mold is In a continuous casting method in which a solidified ingot is continuously pulled out by a pinch roller for drawing out an ingot, the circumferential rotational speed of the pinch roller is set to be lower than the moving speed of a movable mold composed of the rotating ring and a metal belt, The above objective has been achieved.

The present invention will be described in detail below using the drawings.

FIG. 2 shows an embodiment of the present invention, in which the molten metal 2 held in the kundish 1 is constituted by a rotating wheel 3 and a metal belt 4, and its transfer speed is maintained at U (M/m1n). The powder is injected into a moving mold, which sequentially forms a solidified shell 6, leaves the mold, and is pulled out by a pinch roller 7 maintained at a rotational speed such that its circumferential velocity V (M/m) is smaller than U. This becomes ingot 8.

Here, the solidified shell 6 undergoes straightening under the action of the compressive force applied due to the difference between U and V, but numerous experiments have shown that under such conditions no cracks occur at the solidified shell interface. became.

Here, we will discuss the material mechanics conditions for cracks that occur at the solidified shell interface.The cracks that occur at the interface depend on the amount of tensile deformation strain and strain rate applied to the solidified shell, and for example, JIS,
5S41 ordinary steel is 1X10 at a strain of 3%.
Cracking occurs at strain rates of 7 seconds or more, and cracks occur at strain rates of 1% and 1%.
Basic experiments on the high-temperature properties of steel have revealed that cracks occur at speeds of 10-2/second or more.

As mentioned above, in 5S41 ordinary steel, the amount of strain is 3%.
The rotational peripheral speed of the pinch roller is set to be smaller than the mold moving speed so that the difference between the mold moving speed and the pinch roller peripheral speed is less than 7% and 1% (difference between the mold moving speed and the pinch roller peripheral speed).

The method of setting the circumferential speed is as commonly done in this field.
This can be done in advance by testing and/or material mechanics calculations for various alloy materials.

By this means, by determining the circumferential speed that provides the optimum amount of strain and applying this result to actual continuous casting, it is possible to prevent cracking, curving, buckling, etc. of the cast.

In the conventional method of straightening, the tensile force caused by unbending the ingot inevitably acts on the solidified shell interface, which violates the cracking conditions described above and causes cracking.

In contrast, in the present invention, compressive force is applied to the solidified shell by keeping the rotational speed of the pinch roller lower than the transition speed of the mold, and the slab is straightened under the action of the compressive force. As a result, the conditions for generating cracks at the solidified shell interface can be avoided, making it possible to obtain an ingot with almost no cracks.

Examples of the present invention are shown in the table below. By using the present invention, it is possible to significantly reduce the occurrence of cracks and obtain an ingot with sound quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional example, and FIG. 2 is a schematic diagram showing an embodiment of the present invention. 2... Molten metal, 3... Rotating wheel for casting, 4
...Metal belt, 7...Pinch roller, 8...Ingot.

Claims (1)

[Claims] 1. Molten metal is injected into a moving mold space consisting of a rotating casting wheel with a casting groove on the outer periphery and a metal belt covering a part of the casting groove of the rotating wheel, and the mold is made into a mold with at least the outer surface solidified. In a continuous casting method in which ingots are continuously pulled out by pinch rollers for drawing out ingots, the circumferential rotational speed of the pinch rollers is set lower than the moving speed of the movable mold composed of the rotating ring and the metal belt. Characteristic continuous casting method.