GB2152412A - Means for reducing wear of a continuous casting metal mould - Google Patents

Abstract

A mould for continuous casting of molten metal has front, rear and opposed side walls arranged in a rectangular or box-like configuration and is open at the top and bottom to define a mould cavity. As the metal being cast (53) flows downwardly through the mould, the metal contacts one or more bearing members (45) at or below the lower end of the mould. The bearing member(s) reduce(s) contact between the metal and the mould wall facing (16), thus reducing wear of the mould wall facing. The bearing member(s) (45) is (are) adjustable to control the degree of contact between the metal and the mould wall facing. <IMAGE>

Description

SPECIFICATION A continuous casting metal mould with wear compensator This invention concerns a continuous casting metal mould, and more specifically such a mould incorporating a wear compensator.

In the process of continuously casting steel strands, molten metal is poured into the open upper end of a hollow box-like mould. As the molten metal flows downwardly through the mould, the metal is partially cooled, thus forming a skin which surrounds a molten metal core. The partially cooled metal strand continues to flow downwardly through the open bottom end of the mould in the form of a continuous slab, billet or the like. The moulds used in this process generally comprise a pair of spaced apart, parallel front and rear walls and a pair of spaced apart, parallel opposed side walls. Each of the walls is made of a relatively heavy, outer backing plate construction and an inner copper or copper-like facing or liner. The exposed inner surfaces of the facing form the inner casting surfaces of the moulds.

As the partially cooled metal strand flows vertically downwardly through the open bottom end of the mould, the downwardly moving strand is typically withdrawn from the mould and carried by rollers through a cooling zone and the axes of successive rollers follow an arcuate path such that the molten strand follows an arcuate path from the vertical to the horizontal. Water or other coolant is sprayed on the molten strand as the strand is carried by the rollers and the coolant aids in solidifying the metal strand. As the metal strand moves along the arcuate path from the vertical to the horizontal, the molten strand hardens and solidifies into a solid slab which may thereafter be cut to desired lengths.

In the continuous casting process as heretofore described, coolant is also flowed through the steel jacket or backing plate of each of the mould members to assist in cooling the molten strand to thus aid in solidification of the strand.

Heretofore, the copper or copper-like faces of the mould wall members have been subjected to wear resulting in wear patterns and the amount of wear on each of the mould faces is frequently unequal.

The wear on the mould faces is caused by at least three factors. A first cause of wear is the abrasion of the metal strand against the copper face. Even though a mould flux powder is utilized, the abrasion of the hot molten metal against the copper face causes considerable wear.

A second cause of wear and substantial cause of the unequal wear of the copper faces is the misalignment of the rollers below the mould. The misalignment of the rollers causes a shifting of the partially molten strand and causes a greater force on portions of the mould wall faces. Furthermore, the movement of the continuous strand in an arcuate path causes stresses whioh result in unevenly distributed forces against various portions of the copper or copper-like faces.

Yet another factor causing wear on the copper faces is unequal cooling of the strand as the strand moves through the mould and this unequal cooling occurs not only in the top-to-bottom direction but also in the side-to-side direction of the mould.

It will be appreciated that the uneven wear on the copper mould faces changes the dimension of the mould cavity and, therefore, the cross-sectional size and shape of the continuous slab is not constant. That is, not only may the bottom of the mould gradually increase in overall size but, in addition there is curvature imparted to the surfaces of the slab. All of this requires additional machining of the slab, in addition to cutting the slab to length, so that the exterior surfaces of the finished slab are flat and so that the cross-section of the slab is constant.

Prior to the present invention it was necessary to re-machine the copper facings, to eliminate the wear patterns, after about 30,000-40,000 tons of molten metal have been cast. This re-machining required extensive time intervals of shutting down the casting operation so that the facings could be cooled, removed, and re-machined. Of course, it was possible to have a duplicate set of facings available so that worn facings could be removed from the mould wall backing members and replacement facings fastened to the mould wall backing members. Thus, while one set of facings were being re-machined to eliminate wear patterns a second set of facings could be utilized. While this reduces the shut-down time of the casting operation, there is an increased cost because duplicate sets of mould facings are required for each mould.

Another solution to this problem has been the application of a hard facing such as nickel or chrome on the interior casting surface of the mould, but this also substantially increases the cost of the mould facings.

The present invention seeks to overcome or reduce the aforementioned problems by a totally new approach to solving the problem of uneven wear of the mould wall facings.

According to the present invention, in a continuous casting mould formed by a pair of opposed, spaced apart front and rear mould wall members and a pair of opposed spaced apart side mould wall members, each of the mould wall members has an interior casting face and the members are arranged to form an open upper and lower ended casting cavity defined by said interior faces and roughly rectangular in cross-section, bearing surface means being provided below at least one of the mould wall members, the bearing surface means extending laterally inwardly toward the plane of the interior facing of the opposed mould wall member, such that upon casting, a metal strand will contact the bearing surface means, so reducing contact between the metal strand and the mould wall member thereabove.

Furthermore, according to the present invention, in a continuous casting metal mould formed of a pair of opposed, spaced apart front and rear mould wall members and a pair of opposed spaced apart side wall members, each of the wall members has an interior casting face, and the mould wall members are arranged to form a box-like open upper and lower ended casting cavity defined by the casting surfaces, bearing means being provided positioned below the mould for reducing contact between at least one mould wall member and a metal strand being cast through the casting cavity.

The bearing surface according to the present invention may be one or more bearing surfaces for each mould wall and the bearing surface, which functions like an extension of the mould, may be adjustable inwardly and outwardly such that as the bearing surface wears, the bearing surface may be adjusted inwardly to maintain the desired function of reducing contact between the strand and the bottom portion of the mould facing.

The bearing surfaces of the present invention are substantially smaller, in a vertical direction, than the mould wall itself and these bearing surfaces substantially extend the useful life of the mould facings. Furthermore, because of the relatively small size of the bearing surfaces, they aresubstantially less expensive to replace. In addition, because of the small size of these bearing surfaces, if they are to be re-machined there is a substantial reduction of the time interval during which the casting operation must be shut down.

The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective illustration of a typical continuous casting mould; Figure 2 is a front elevational view of the interior mould wall with the wear pattern illustrated thereon; Figure 3 is a perspective illustration of a rear mould wall, such as shown in Figures 1 and 2, with the bearing surfaces of the present invention positioned at the bottom of the mould wall; Figure 4 is a sectional elevational view to a larger scale taken along line 4-4 of Figure 3, and with a molten metal strand in association therewith, and Figure 5 is a cross-sectional view taken along the line 5-5 of Figure 4.

A continuous casting mould 10, illustrated in Figure 1 typically comprises a pair of opposed, spaced apart rear mould wall members 11, 12, respectively, and a pair of opposed, spaced apart side mould wall members 13, 14, respectively. The four mould wall members are configured as a generally square or rectangular box-like container open at the top and bottom with the side wall members 13, 14 adjustably clamped between the front and rear wall members 11, 12, to define a casting cavity 15 therebetween. Molten metal is poured into the upper, open end of the cavity 15 and solidified metal in the form of a slab having a solidified skin enclosing a molten metal core emerges from the open lower end of the mould cavity.The slab emerging from the lower open end of the casting cavity will be engaged by rollers which cause the slab to follow a downward arcuate path from the vertical toward the horizontal as is well known.

The front and rear mould wall members 11, 12 are each formed as a laminate structure including a copper or copper-like facing 16 mounted te a steel jacket or steel backing plate 17.

Similarly, the side wall members 13, 14 are each formed as a laminate structure including a copper or copper-like face plate 18 mounted to a steel jacket or steel backing plate 19.

Conventional adjustment means 20 are provided to spread apart the front and rear mould wall members so that the side wall members may be moved toward or away from each other, thereby adjusting the width of the casting cavity 15, with each of the copper facing plates positioned to contact the molten metal during the casting operation.

As is conventional, means are provided for cooling the molten metal during the casting operation.

Specifically,each of the copper facing plates 16, 18 has a plurality of vertical channels or grooves 21 (Fig.4) machined in one face thereof. Each of the steel backing plates 17, 19 have upper and lower horizontal grooves 22, 23 (again Figure 4), which function as headers, with the grooves 22, 23 being in communication with each of the vertical channels 21 when the copper facing is secured to the steel backing plate. Inlet and outlet ports 24, 25, respectively, are machined through the steel backing plate in fluid communication with the headers 22, 23 such that upon introduction of a coolant such as water into the inlet port 24, the coolant flows through the header, through the channels, through the opposite header and emerges through the outlet port 25.

Prior to the present invention, for reasons previously discussed such as abrasion of the cast molten metal against the facing plates, misalignment of the rollers below the mould relative to the cavity and unequal cooling, the copper facing plates 16, 18 tend to wear unevenly. Figure 2 illustrates the typical wear patterns which develop on a copper facing plate including a first section 30 which would exhibit the greatest amount of wear, and second, third and fourth sections 31, 32 and 33, respectively, which exhibit successively less wear.

After the casting of 20,000-40,000 tons of steel, the wear on an individual facing could be as high as .040 inch for section 30.030 inch at 31, .020 inch in section 32 and .010 inch in section 33. It should be appreciated that wear patterns will exist on all four of the copper facings.

To substantially reduce if not eliminate these wear patterns on the facing plates themselves, the present invention provides bearing means 40 for substantially reducing contact between the cast molten metal strand and the copper facing plates 16, 18. The bearing means are easily replaceable, relatively inexpensive, and serve as a vertical extension of the mould cavity walls at the lower end of the mould.

With reference to Figures 3, 4, and 5, the preferred bearing means of the present invention includes a first mounting block 41 mounted to the bottom of the backing plate 17 by a plurality of bolts 42. The mounting block 41 which may be made of steel, includes a transverse bore 43 therethrough with the axis of the bore being perpen dicular to the direction of casting of the molten metal. Specifically the bore 43 extends from the outside toward the inside of the mould and the bore is provided with an axial keyway 44.

The bearing means 40 also includes a bearing surface block 45 which may be made of copper or which has a copper facing and is secured to a shaft 46. Shaft 46 is dimensioned to fit within the transverse bore 43 and includes an axial key 47 to engage the keyway 44 in the mounting block. The combination of the key and keyway prevents rotational motion of the bearing surface 45.

It is desired to be able to adjust the position of the bearing surface block 45 relative to the cavity and means are provided to accomplish such adjustment. In the illustrated embodiment, shaft 46 includes a plurality of teeth 48 formed on one side of the shaft in the nature of a rack. Gear means 49 is mounted by a mounting bracket 50 to the backing plate 17 and a lever or other advancing means 51 is provided to rotate the gear 49 in either direction to thereby advance or withdraw the toothed rack shaft 46. Movement of the shaft 46 results in corresponding linear movement of the bearing surface block 45.

As illustrated in Figure 4, the position of the bearing surface block 45 in contact with the solidified skin 52 of the molten metal strand 53 provides a space or separation 54 between the strand 53 and the copper facing 16 at the bottom end of the mould cavity thereby substantially reducing wear and substantially eliminating any uneven wear of the copper facing plates.

The present invention contemplates the provision of bearing means 40 for one or more of the mould wall members 11, 12, 13 and 14. In addition, the bearing means may include a single bearing surface block 45 extending the full side-to-side dimension of the mould wall facing or, as illustrated in Figure 3, there may be a plurality of such bearing surface blocks 45 each of which would be individually adjustable by having a first mounting block 41 and actuating mechanism associated therewith.

It may be appreciated that as the bearing surface block 45 wears, the position of the shaft 46 is advanced inwardly toward the strand to thus reduce contact between the strand 53 and the mould wall facing 16. Such adjustment may be accomplished during a continuous casting operation or between casting operations.

Should the copper bearing surface block 45 become worn, it may be easily replaced by advancing the gear 49 so that the shaft 46 may be withdrawn from the mounting block 41 and a new bearing block-shaft combination inserted into the mounting block.

It should be appreciated that the bearing surface means may be attached to the bottom of the mould or, alternatively, may be secured to the rollers below the mould, or may be independently mounted between the bottom of the mould and the top of the first set of rollers.

The foregoing is a complete description of a preferred embodiment of the present invention. Various changes may be made without departing from the scope of the present invention as defined in the appended claims.

Claims (9)

1. A continuous casting mould formed by a pair of opposed, spaced apart front and rear mould wall members and a pair of opposed spaced apart side mould wall members, each of the mould wall members having an interior casting face and the members being arranged to form an open upper and lower ended casting cavity defined by said interior faces and roughly rectangular in cross-section, wherein bearing surface means is provided below at least one of the mould wall members, the bearing surface means extending laterally inwardly toward the plane of the interior facing of the opposed mould wall member, such that upon casting, a metal strand will contact the bearing surface means, so reducing contact between the metal strand and the mould wall member thereabove.

2. A mould as claimed in claim 1, wherein at least two bearing surface means are provided, one below and adjacent to each of the front and rear mould wall members.

3. A mould as claimed in claim 1 or 2, wherein the or each bearing surface means is adjustable towards and away from the plane of the opposed interior facing.

4. A mould as claimed in claim 3, wherein the bearing surface means is adjustable during continuous casting.

5. A mould as claimed in claim 1, 2 or 3, wherein the or each bearing surface means includes a plurality of discrete bearing surfaces.

6. A mould as claimed in claim 5, wherein each of the discrete bearing surfaces is selectively and independently adjustable.

7. A mould as claimed in any one of claims 1 to 6, wherein the or each bearing surface means is secured to the mould.

8. A continuous casting metal mould formed of a pair of opposed, spaced apart front and rear mould wall members and a pair of opposed spaced apart side wall members, each of the wall members having an interior casting face, and the mould wall members are arranged to form a boxlike open upper and lower ended casting cavity defined by the casting surfaces, wherein bearing means is provided positioned below the mould for reducing contact between at least one mould wall member and a metal strand being cast through the casting cavity.

9. A continuous casting mould substantially as herein described, with reference to and as illustrated in Figures 3 to 5 of the accompanying drawings.