SU835536A1 - Method of producing sheets for offset printing - Google Patents

Description

one

The invention relates to the rolling industry and can be used to produce sheets for offset printing.

For an offset printing method, a high-precision cold-rolled steel sheet is required, other 0.3-0.5 mm wide, 420-1400 mm wide, with a defect-free surface of class 8-10 of finishing and with mechanical properties that allow forming when the sheet is installed in an offset machine.

Known methods for producing sheets, in which hot-rolled etched rolls are rolled with simultaneous emulsion on a continuous thin-sheet four-stand cold cold rolling mill to thick, 0.31–0.5 mm, annealed in bell furnaces and transported to a single-split training train, quarto, training the strips are produced with a reduction of up to 2% 1.

The disadvantage of this method is that the metal after training has insufficient hardness, and this leads to damage to the surface and kinks from the effect of bending, their loads, lowering, and the resistance of offset forms to them.

There is also known a method of producing sheets for offset printing from low carbon construction steel, on which cold rolling, annealing and second cold rolling (training) are performed, and the second cold rolling is dried in rolls with different roughness and with a total reduction of 1.5 % 2. However, the sheets after the second cold rolling due to the small work hardening are plastic and have a hardness not exceeding 50 units. HRB. When performing finishing operations and when using sheets

at the consumer, their surface is easily damaged, fractures appear in places of concentration of bending loads, the source of which is the mass of the sheet or the pressure of the liquid in the galvano- line.

The purpose of the invention is to improve the mechanical characteristics and reduce the surface defects of the sheet.

This is achieved by the fact that, in the known method of producing sheets for offset printing, the second cold rolling is performed with a reduction of 10-45% and then further processing the strip by alternating bending with a relative deformation of 0.8-1.2%.

The drawing shows the dependencies

the number of bends on the amount of reduction (degree

work hardening) when rolling in a processing strip

alternating bend.

The plasticity of the sheet for offset printing is determined by the number of bends with kinks in sponges with a radius of 2 mm. It has been established that a sheet that can withstand 30 bends with kinking meets the requirements that ensure sufficient formability of the metal when filling the mold into a printing machine.

The strength characteristics of the steel increase with decreasing compression and the ductility decreases. When crimped to 10%, the sheet has high ductility, but insufficient strength, and its surface is easily damaged. Curve 1 in the drawing is the dependence of the number of bends on the amount of reduction during the second rolling, from which it follows that the sheet will withstand 30 bends after rolling with a reduction of not more than 30%. Processing with alternating bending with a deformation of 0.8-1.2% yields the same 30 bends with a reduction of up to 45% (curve 2), which will provide an increase in sheet strength without reducing ductility below the allowable value.

Research has shown that when processing with alternating bending with a deformation of less than 0.8%, a noticeable increase in the plasticity of the sheets is not achieved, and with deformations of more than 1.2%, the sheet roughness formed during the second rolling changes, which leads to a decrease in the quality of printed products.

Example. Low carbon steel in rolls 500–1500 mm wide with chemical composition (%):, 09; , 2-0,4; , 04; , 03; , 025; ,ten; , l; Si 0.15; , 05 from the hot rolling mill is transported to the pickling unit. After hydroacid etching, the strip is subjected to first cold rolling with a relative compression of 60–70%, in rolls with a roughness of Ra 3.0–3.5 μm, which reduces the welding of the coils of the coils during annealing. Rolling strips are subjected to recrystallization annealing in bell-type furnaces under a muffle at a temperature of 680-730 ° C. The annealed strips roll a second time on a four-quarto mill of quarto to a thickness of 0.3–

0.5 mm with a relative compression of 10-45% in rolls with a roughness of 2.3 μm, which will provide a surface with a required profile of microprofile. After the second rolling, the hard metal has high strength, characteristics, but insufficient ductility. In order to increase the plasticity, such a metal is subjected to an alternating bend treatment in a roller-straightening machine with a roller diameter of 20-70 mm, the number of rollers being 25-50 pieces. The value of the relative deformation is 0.8-1.2%. After treatment with an alternating bend, the ductility and flatness of the metal increase.

The technical and economic advantages of the proposed method consist in the fact that the second cold rolling makes it possible to obtain a 10-45% high-strength sheet during compression. This sheet has less mechanical damage. Processing with alternating bending allows to increase the plasticity and flatness of the sheet, which

will lead to an increase in form resistance.

Claims (2)

1.Sheftel P.I. Technologists of rolled steel production. M., Metallurgists, 1976, with. 462-465, 484-485. 2. USSR author's certificate number 590021, cl. B 21B 1/38, 1976. ten I 2030 0SO W 8B 60 Degree tmepa ° / about