Shears with parallel blades are used in slabbing lines, blooming lines, billet and bar mills. They are used for cold and hot rolling cutting to length.
Rolled material profile cut with shears with parallel blades:
Cut surface during cutting with these shears remains constant. The temperature of the metal delivered to the shear metal is 750-1100°С.
Blades length L:
a) for shears with cutting force of 0,5…2,0 mN is to be 3-4 times bigger than max. width of the workpiece, taking into account capability of cutting workpieces with smaller cross sections in several lines (in bundles);
b) for shears with cutting force below 16 mN, used for blooms, is to be 2-3 times bigger than max. cross section bloom;
c) for shears with cutting force below 20 mN, used for slabs, is to be 150…200 mm bigger than max. slab width.
Blades cross section size is based on the following correlation: S / δ = 2,4…3, where S is height, and δ is blade thickness.
Blades shape is a symmetrical rectangle. Grinding angle equals to 90°. Blades are manufactured of the following steel grades: 6ХНМ, 6ХВ2С etc. with hardness up to 40...50 HRC after heat treatment. For blades service life increasing it is allowed to use hard alloy metal tipping.
Guillotine shears are divided into two types in accordance with their design features: opened type and closed type.
Opened type shears have got short blades, they are used for flat steel workpieces and cold rolled section steel. Upper (moving) blade is inclined at the angle of 2…6°.
Closed type shears are used for wide sheets and strips cutting to length, both in cold and hot conditions.
Closed type shears are manufactured with upper and lower moving blade
In the shears with upper moving blade the upper blade is fixed inclined and the lower blade is fixed horizontally. The incline angle to be taken as equal to 1…5° for cutting force decrease, depending on cutting sheets thickness. The more the rolled sheet (strip) thickness the more the incline angle.
In the shears with lower moving blade the lower blade is fixed horizontally (the upper is fixed inclined) or inclined (and the upper is horizontally). During cutting with upper inclined blade the sheet (strip) bows, and the cut results asymmetrical. During cutting with lower inclined blade the sheet (strip) retains against upper horizontal blade and the cut results straight (perpendicular).
For the better cutting quality the shears with circular cut are used. The circular cut principle is that the upper blade is an arc of circle, that is non-slip rolled along the lower horizontal blade. And so every point on the blade arc describes a cycloidal curve during rolling and the angle of cutting keeps constant.
Flying shears blades materials are as follows: steel of grades 5Х2ВС, 5ХНВ etc. Blades hardness for metal cold cutting is of 52...59 HRC, for metal hot cutting is of 40...50 HRC.
Flying shears are used for rolled products travelling cut-off. Generally, flying shears working capacity means rolling mill working capacity.
Flying shears basic types: drum-type, lever-crank shears, shears with floating crank, planetar and pendulum shears.
Blades for these types of shears are parallel mounted, or the lower blade is straight and upper blade has got inclined or chevron (Y-shaped) blade edge or vice versa.
Such form of blades provides high quality cold cutting of thin and thick strips, and also reduces dynamic force during cutting. Strip cutting plane becomes more smooth and vertical (especially during thick strips cutting).
Blades materials: tool steels which can workat increased impact loads, hardness after treatment HRC 50…60.
Disk shears are used for strip trimming and longitudinal cutting into narrower strips (slitting).
For high quality cutting (straight and without burs) the circular blades are mounted with radial overlap of 1…2 mm (the thicker the strip the smaller the blades overlap). When the strip thickness is more than 10mm an underlap and a small back-lash (horizontal) overlap are used, and during cutting a strip with less than 0.2 mm thickness the blades are mounted tight, without clearance. Disc thickness to be within 0,06…0,1 of its diameter.
The blades are manufactured of chrome-tungsten, steel of grade 5ХВС with hardness after heat treatment of 60 HRC; blades grinding angle is taken as 90° (blades are strictly cylindrical).
Therefore, with a knowledge of exact cutting parameters, ENCE GmbH specialists can select the required type of tool steel, hardness and the other blades characteristics, to maximize your equipment capacity. Your end result will be as follows: saved money because of cutting tool service life increasing, and also cutting quality improvement.
You may find information about other metallurgical production equipment from ENCE GmbH (ЭНЦЕ ГмбХ) on the main page of metallurgy site in different languages of the world:
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