| 1. | Apparatus for shearing plate stock, which comprises: (a) means for conveying a single layer of pieces of scrap sheet material; (b) a fixed serrated lower blade which is located such that said pieces can be fed over the serrations of the lower blade by said conveying means; and (c) a downwardly movable serrated upper blade, which has serrations of complementary shape and location to those in said lower blade, said serrated blades being arranged to define a series of cornerlinked parallelograms in material to be sheared by said blades. |
| 2. | Apparatus according to claim 1, wherein the downwardly movable blade is downstream of the fixed blade. |
| 3. | Apparatus according to claim 1 or claim 2, wherein a backstop member is provided downstream of the downwardly movable blade so as to prevent downstream movement of the pieces of sheet material during each shearing operation. |
| 4. | Apparatus according to any preceding claim, wherein said means for conveying the scrap material is provided with guide means for ensuring correct alignment of the scrap sheet material prior to said material being fed over the serrations of said lower blade. SUBSTITUTE SHEET . |
| 5. | A method of shearing plate stock, which comprises conveying a single layer of pieces of scrap sheet material between a fixed serrated lower blade and a downwardly movable serrated upper blade, moving said upper blade downwardly so as to cause shearing of said sheet material, the serrations of the upper and lower blades being of complementary shape and location so as to shear said material into a series of pellets in the form of cornerlinked parallelograms. |
| 6. | A method according to claim 6, wherein said plate stock is of steel. |
| 7. | A method according to claim 6 or 7, wherein apparatus according to any of claims 1 to 5 is employed. |
| 8. | A method of cooling molten steel, which comprises introducing steel pellets into said molten steel, in which said pellets are produced by a method according to claim 7 or 8. SUBSTITUTESHEET. |
The present invention is concerned with a method and apparatus for shearing of metal plate (such as steel plate),
Traditional steelmaking processes involve production of liquid steel in bulk (in large vessels of capacity of the order of 300 tonnes)- which is then poured to form cold ingot moulds- to be transported to slabbing mills for rolling into steel slabs. A more recent process involves continuous casting of molten steel from large vessels into steel slabs; this method therefore avoids the need for ingot moulds- which introduces substantial energy savings and quality improvements, but at the same time involves difficulties in temperature control of the molten steel.
If the temperature of the latter is too high- the resulting slab is too soft, while if the temperature is too low, the slab is difficult to manipulate. Precise temperature control of the molten steel is essential for successful continually casted slabs to be produced. The problem is to control the temperature throughout the vessel without causing the top layers or bottom layers of liquid steel to become too hot or too cold relative to the rest of the vessel. The conventional way of achieving the desired temperature control
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is to make the steel slightly too hot and then reduce the temperature by the introduction of some sort of cold product. Unfortunately, each product of this type which could be economically employed has disadvantages and is not available in either a consistent form or a large enough quantity.
One method which has been employed for cooling molten steel involves dipping a cold steel slab into the molten steel and stirring it by means of an overhead gantry crane. This method has inherent safety problems, is difficult to control and does not give consistent cooling throughout the molten material.
A more recent method involves the introduction of chopped or small grade steel scrap into the molten steel. This method has the disadvantage that if the chopped scrap has too low a density, it tends to float on the molten steel and therefore only cool the top layers; conversely if the density is too high, it tends to sink to the bottom before it has fully melted, with consequent overcooling of a bottom layer. Thus although ' this method can offer precise control over the quantity and quality of cooling material, it cannot offer consistent temperature reduction throughout the molten steel.
We have now devised method and apparatus whereby sheared pellets of consistent quality and density can be achieved.
According to a first aspect of the present invention, therefore, there is provided apparatus for shearing plate stock, which comprises:
(a) means for conveying a single layer of pieces of scrap sheet material;
(b) a fixed serrated lower blade which is located such that said pieces can be fed over the serrations of the lower blade by said conveying means; and
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(c) a downwardly movable serrated upper blade, which has serrations of complementary shape and location to those in said lower blade, said serrated blades being arranged to define a series of corner-linked parallelograms in material to be sheared by said blades.
The term "parallelogram" relates to a planar four-sided figure with two pairs of parallel and equal sides; the term is intended to encompass a rectangle, which is a special case of a parallelogram in which the angles are all right angles.
Preferably, the downwardly movable blade is downstream of the fixed blade, and a backstop member is provided downstream of the downwardly movable blade so as to prevent downstream movement of the pieces of sheet material during each shearing operation. This enables selection of the length of the pieces to be sheared from the sheet material, and thus to permit control of the density of the resultant pellets.
The present invention further comprises a method of shearing ' plate stock, which comprises conveying a single layer of pieces of scrap sheet material between a fixed serrated lower blade and a downwardly movable serrated upper blade, moving said upper blade downwardly so as to cause shearing of said sheet material, the serrations of the upper and lower blades being of complementary shape and location so as to shear said material into a series of pellets in the form of corner-linked parallelograms.
The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a general view of an exemplary apparatus according to the invention;
Figure 2 is a more detailed view of the shearing blades of the apparatus of Figure 1; and
Figure 3 shows further details of the cutting edges of the shearing blades.
Referring to the drawings, there is shown a conveyor system 1 comprising a series of skid rollers 2 which are arranged at an inclined angle relative to the gap between a pair of serrated blades, comprising a fixed serrated bottom blade 3 and a vertically movable serrated top blade 4.
The serrated blades 3 and 4 are such that they each have the same number of serrations across the width of the respective blade (sixteen such serrations being shown in the illustrated embodiment) and of complementary shape such that the overlap of the blades defines a series of corner-linked parallelograms, the series extending across the width of the blades. (One such parallelogram 5 is shown with hatched lines in Figure 1 and, in more detail, in Figures 2 and 3).
The optimum angle of the blade is determined by the working ' edge contour angle of the respective blade; for the most efficient and best pellets the contour angle and the conveyor feed line angle are preferably the same.
In use, an array of scrap steel sheet portions 6 is fed over rollers 2 along line A, which is inclined relative to the line B of conveyor drive; this has the effect that the sheet portions tend to migrate towards the left hand side 7 of the conveyor system 1 in the illustrated embodiment.
Just beyond the line of top blade 4 is a back stop member 8 which extends all across the width of the blades 3 and 4.
To ensure that the scrap pieces are guided into the blade at optimum position, side register skid bar/rollers or other side register means (not shown) are preferably employed.
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The line of conveyor drive rollers in the illustrated embodiment is angled so as to drive the scrap sheet portions towards the side register whilst also driving them forward to make contact with the backstop 8 ready for the shear stroke. Other methods of feeding can, of course, be employedsuch as a conveyor which is inclined to the horizontal (Such that the sheet material would tend to migrate to the side register under the influence of gravity.
Pieces of scrap steel plate are laid on the angle biased roller conveyor, and are placed in a single layer across the conveyor as near to the side register edge as possible, and along the length of the conveyor as bear to the backstop bar as possible. The prudent placing of the plate pieces leaving as few gaps as the irregular shapes of the pieces allows, is the most efficient way of getting the maximum tonnage of cut pellets out of the apparatus.
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