RU2365635C1 - Method of production of carbon structural sheet steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to rolling, in particular to making cold-rolled sheet steel with glossy finish. In order to improve application properties of the sheet steel with the carbon content of 0.07…0.14 wt % the steel strips are cold-rolled on the continuous rolling mill in the knurled working rolls of the final stand with the average height of the surface pattern of their bodies Ra≤3 mcm producing a sheet of 2.0…2.5 mm thick and with a glossy finish, annealing of the cold-rolled coils in the bell-type furnaces with protective hydrogen atmosphere without increasing the temperature of the coolest point on the coil, starting water cooling at a temperature of 280°C and without water cooling allowing to be under the heating bell with the burners turned off for 4 hours minimum and temper rolling of the annealed strips on the grinding working rolls with Ra≤1 mcm.

EFFECT: improved application properties of the sheet steel.

1 ex

Description

The invention relates to rolling production and can be used in the manufacture of cold-rolled sheet steel with a glossy surface.

Mandatory operations of the cold-rolled steel sheet manufacturing process are strip billet rolling on a continuous (e.g. broadband) mill, annealing of cold-rolled coils (usually in bell furnaces) and subsequent training of annealed strips. All these operations are also necessary for the production of sheets with a glossy surface, which are in high consumer demand. The manufacturing technology of cold-rolled strip steel is described in sufficient detail in the reference book “Technology of rolling production”. / Ed. V.I. Zyuzina and A.V. Tretyakov. Book 2, Moscow: Metallurgy, 1991, pp. 640-644, 683-688 and 694-698.

A known method of manufacturing a metal tape, including compression of the workpiece by 50-75% cold rolling, heat treatment of the rolled tape and its subsequent editing after every 15-25% compression (see AS USSR No. 480807, class B21D 1/05, publ. 10.10.75 g.). However, this method is unsuitable for producing sheet steel with a glossy surface.

The closest analogue to the claimed method is the technology for the production of cold rolled carbon steel, given in the book by V. F. Zotov and V. I. Elin “Cold rolling of metal”. M .: Metallurgy, 1988, p.168-172, 188-189 and 193-196.

This technology includes cold rolling of strips in a continuous mill, annealing of cold-rolled coils and training of annealed strips, and is characterized by the fact that the total reduction for strips with a thickness of 2.0 ... 2.5 mm is taken within 43 ... 57%, annealing consists of three stages ( heating, aging and cooling of the metal), and training is carried out with a relative compression within 0.25 ... 3.5%. This technology is also unsuitable for the production of sheets with a glossy surface, since it does not specify the state of the surface of the work rolls of the mills, and also does not specify the annealing modes.

The technical task of the present invention is to improve the consumer properties of carbon structural sheet steel with a glossy surface.

To solve this problem, in a method involving cold rolling of a roller in a continuous mill, annealing of cold rolled coils and training of annealed strips, rolling of steel with a thickness of 2.0 ... 2.5 mm with a carbon content of 0.07 ... 0.14 wt.% Is carried out on the mill in incised work rolls of the last rolling stand with an average microroughness of the surface of their barrels Ra≤3 μm, annealing is carried out in bell-type furnaces with a protective hydrogen atmosphere without raising the temperature of the point of the roll most behind heating, with the start of water cooling at a temperature of 280 ° C and without air cooling, taking the holding time under the heating cap with the burners turned off for at least 4 hours, and the annealed strips are trained on polished work rolls with Ra≤1 μm.

The given process parameters are obtained empirically and are empirical.

The essence of the proposed technical solution is to use when cold rolling and training rolls with specific microgeometry of the surface of their barrels, as well as to optimize the modes of annealing of cold rolled steel. As a result of this, a maximum yield of sheets with a given glossy surface is achieved.

Experimental verification of the proposed method was carried out at OJSC "Magnitogorsk Iron and Steel Works". To this end, in the production of 10sp sheet steel with a glossy surface 2.0 ... 2.5 mm thick containing 0.07 ... 0.14 wt.% Carbon, the values of Ra of the rolls of the last rolling stand of the rolling mill, as well as the annealing parameters of the coils were varied in bell-type furnaces. The results of the experiments were evaluated by the yield of sheets with the desired glossy surface.

The best results (yield of high-quality sheets with a glossy surface within 99.6 ... 100%) were obtained using the inventive technology. Deviations from its recommended parameters worsened the achieved indicators.

So, for example, rolling in the mill, finishing stand rolls had a notch of barrels with Ra> 3 μm, reduced the yield of sheet metal with the required surface to 87 ... 98%. The output of glossy quality sheets decreased when using nitrogen-hydrogen and nitrogen protective atmosphere during annealing, as well as when raising the temperature of the point of the roll most behind in heating, with the start of water cooling. A decrease in the yield of glossy sheets was observed when holding under a heating hood with burners off for less than 4 hours and when training annealed strips on work rolls with Ra> 1 μm.

The technology chosen as the closest analogue was not tested in the experiments due to its obviously unsuitability for obtaining high-quality sheet metal with the required surface. Thus, an experimental verification confirmed the acceptability of the technical solution found to achieve the goal and its advantage over a known object.

Feasibility studies have shown that the use of the present invention for the production of carbon structural sheet steel with a glossy surface will increase the yield of rolled products with improved consumer properties, which will increase the profit from its sale by at least 15%.

Concrete example

A strip of 2.2 mm thickness containing 0.11 wt.% Carbon is rolled on a continuous broadband mill. Work rolls of the finishing stand of the mill are made with incised surfaces of their barrels with Ra = 2 μm.

Annealing of cold rolled coils - in bell-type furnaces with a protective hydrogen atmosphere and without temperature rises of the point of the coil most lagging behind in heating, with the start of water cooling at a temperature of 280 ° C and without air cooling. The exposure time under the heating hood with the burners turned off is 4.5 hours.

Annealed strips are trained in polished work rolls with Ra = 0.8 μm. The yield of high-quality sheets with a glossy surface of 99.8%.

Claims (1)

A method for the production of carbon structural sheet steel, including cold rolling strips in a continuous mill, annealing cold rolled coils and training annealed strips, characterized in that the rolling of sheet steel with a carbon content of 0.07 ... 0.14 wt.%, A thickness of 2.0 ... 2.5 mm with a glossy surface in the notched working rolls of the finishing stand of the mill with an average microroughness of the surface of their barrels Ra≤3 μm, annealing is carried out in bell furnaces with a protective hydrogen atmosphere without raising the temperature of the most rail on the heating roll point, water cooled from a temperature of 280 ° C, the exposure is performed under the heating coil cap with detached burners for at least 4 hours, and temper rolling the annealed strips are buffed on the working rolls with Ra≤1 microns.