RU2048216C1 - Cold strip steel production method - Google Patents

Abstract

FIELD: rolling. SUBSTANCE: method involves setting ultimate thickness of hot rolled strips in inversely proportional dependence relative to ultimate width of cold rolled strip and value of carbon equivalent of steel by regulated dependence. EFFECT: increased efficiency of method by reduced relative thickness of scale on hot rolled strip. 2 tbl

Description

 The invention relates to rolling production, and specifically to the manufacture of cold-rolled steel strips in sheet-rolling shops, in which modern continuous cold rolling mills are commissioned.

 There is a known method of cold rolling [1] in which, in order to improve the quality of the strips, the rolling is carried out with a total compression determined by the mathematical dependence, in which the total compression of the cold rolled strip is determined by the depth of defects on the surface of the hot rolled strips and the roughness of the rolls on the cold rolling mill.

 The disadvantage of this method is that it does not optimize the thickness of the hot-rolled strip depending on the thickness and width of the cold-rolled.

 The closest in technical essence and the achieved result to the invention is a method for the production of strips [2] consisting in the fact that the thickness of the intermediate roll before the finishing group of stands of a broadband mill is changed in accordance with the width of the rolled strips and determined by mathematical dependence. The basis of this method is the principle of maximum use of the capabilities of the equipment of the finishing group of stands of a broadband mill in order to improve the quality of hot rolled strips.

 However, the method does not reduce the consumption of metal scale in the production of cold-rolled strips.

 The objective of the invention is to reduce the relative thickness of the scale layer on the hot rolled strip, thereby reducing the cost of producing a cold rolled strip.

где В ширина холоднокатаной полосы, м;
C_э= C+

+

углеродный эквивалент, мас.This is achieved by the fact that in the proposed method for the production of cold rolled strip steel, the final thickness of the hot rolled strips is determined by the empirical formula:
h _gk = 45

where In the width of the cold-rolled strip, m;
C _e = C +

+

carbon equivalent, wt.

 C, Mn, Si the content of carbon, manganese, silicon in steel, wt.

h _hk thickness of the cold-rolled strip, mm;
V _ol rolling speed, m / s.

 The essence of the invention lies in the fact that the thickness of the hot rolled strip is set to the maximum allowable for a given cold rolling mill in direct proportion to the thickness of the cold rolled strip and inversely proportional to the strip width, the carbon equivalent of the steel and the cold rolling speed. Increasing the thickness of the hot-rolled strip allows you to reduce the relative thickness of the scale layer and improve technical and economic indicators in the production of cold-rolled strip steel.

To implement the method, the branded assortment of the cold rolling mill is divided into several groups. Steel grades with close carbon equivalent values are introduced into each group, for example, group I includes steels with C _e 0.05-0.20%; group II steel with C _e 0.20-0.30%; in group III with C _e 0.31-0.40% in IU steel group with C _e 0.41-0.50%, etc. Within each brand group, the assortment is divided into subgroups of various widths. For example, in the 1st group, stripes with a width of 900-1100 mm are introduced, in the 2nd subgroup of a strip with a width of 1101-1300 mm, in the III subgroup of a strip with a width of 1301-1550 mm.

 After the breakdown of the assortment into groups and subgroups, rolling tables are compiled, in which, for a cold-rolled strip of a given final thickness, the thickness of the rolled sheet (hot-rolled strip) is established by empirical dependence. After that, rolling tables are made, for example, of the following type, into which such parameters as a group of steel grades are necessarily entered; thickness and width of a particular strip, rolling speed, rolling temperature.

 Based on empirical dependence, a complete table is developed for the entire range of cold rolling mills, which is an integral part of the technological instruction.

In accordance with such a table for the production of a cold-rolled strip with a thickness h _hk and a width B from steel with carbon equivalent C _e , the thickness of the hot-rolled strip h _{hk is set} .

 The method was tested in the production of cold rolled strip steel at the Cherepovets Metallurgical Plant. Hot rolled strips were rolled in a continuous mill 2000; scale from their surface was removed in continuous pickling units operating on sulfuric acid. Cold rolling of the strips was carried out on a new five-stand mill 1700.

 The following are examples of the method with reference to table 2.

= 3,1 мм
При толщине слоя окалины 10 мкм относительная толщина слоя окалины (суммарная для двух поверхностей полосы) составила 0,65% Горячая прокатка полос на толщину 3,1 мм позволила иметь высокую производительность при горячей прокатке (1020 т/ч) так и при последующем травлении (145 т/ч).PRI me R 1 (table 2). Etched steel strip 08Y grade 3.1 mm thick, 1.5 m wide with a mass content of carbon, manganese and silicon, respectively 0.07; 0.24 and 0.01 wire rods on a five-stand mill 1700 with a speed of 16 m / s to a thickness of 0.8 mm. The thickness of the hot rolled strip was determined by the empirical formula:
h _gk = 45

= 3.1 mm
With a scale layer thickness of 10 μm, the relative thickness of the scale layer (total for two strip surfaces) was 0.65%. Hot rolling of strips to a thickness of 3.1 mm made it possible to have high productivity during hot rolling (1020 t / h) and subsequent etching ( 145 t / h).

= 3,7 мм
При толщине слоя окалины 10 мкм относительная толщина слоя окалины составила 0,54% Горячая прокатка полос на толщину 3,7 мм позволила иметь высокую производительность как при горячей (1050 т/ч), так и при последующем травлении (143 т/ч).PRI me R 2 (table 2). The etching of a strip of 3sp steel is 3.7 mm thick, 1.25 m wide with a mass content of carbon, manganese and silicon, respectively, 0.16; 0.47; 0.19, rolled on a five-stand mill 1700 at a speed of 15 m / s to a thickness of 1.2 mm. The thickness of the hot rolled strip was determined by the empirical formula:
h _gk = 45

= 3.7 mm
With a scale layer thickness of 10 μm, the relative thickness of the scale layer was 0.54%. Hot rolling of strips to a thickness of 3.7 mm made it possible to have high productivity both during hot (1050 t / h) and subsequent etching (143 t / h).

= 5,1 мм
При толщине слоя окалины 10 мкм относительная толщина слоя окалины составила 0,39% Горячая прокатка полос на толщину 5,1 мм позволила иметь высокую производительность как при горячей прокатке (1400 т/ч), так и при последующем травлении (190 т/ч).PRI me R 3 (table 2). Etching of a strip of steel of grade 40 5.1 mm thick, 10 m wide with a mass content of carbon, manganese and silicon, respectively 0.41; 0.53; 0.25 was rolled on a five-stand mill 1700 at a speed of 10 m / s to a thickness of 2.0 mm. The thickness of the hot rolled strip was determined by the formula:
h _gk = 45

= 5.1 mm
With a scale layer thickness of 10 μm, the relative thickness of the scale layer was 0.39%. Hot rolling of strips to a thickness of 5.1 mm made it possible to have high performance both during hot rolling (1400 t / h) and subsequent etching (190 t / h) .

When calculating the thickness of the hot strip (h _kg) not by (Table 2, Example 4) is selected lower than in the process according primert within 1 h _zk 3.0 mm. In this case, the relative thickness of the scale layer is higher (0.65%). This reduces productivity during hot rolling (1000 t / h) and etching (142 t / h). Thus, deviations from the proposed modes lead to an increase in the relative thickness of the scale layer, to a decrease in productivity during hot rolling and etching.

 A comparison of the proposed (table 2, examples 1-3) and the known (table 2, example 5) methods shows that in the proposed method the relative thickness of the dross layer is 0.06-0.32% and higher the performance of the units when hot rolling and pickling, respectively, at 40-420 and 8-55 t / h. As can be seen from the table only in the case of applying the formula for calculating the thickness of the hot-rolled strip (table 2, examples 1-3), the goal of the invention is achieved, as a result of which the parameters of the proposed method should be considered significant.

 Thus, the application of the proposed method provides for the production of cold rolled steel reducing the relative thickness of the scale layer and increasing the performance of the units during hot rolling and pickling. The effect of the implementation of the proposed method is achieved by improving the technical and economic indicators in the production of cold rolled steel.

Claims (1)

METHOD FOR PRODUCING COLD-STEEL STRIP STEEL, including hot rolling on a broadband mill, descaling and cold laying on a continuous mill, characterized in that the final thickness of the hot-rolled strip is determined inversely with the final width of the cold-rolled strip and the carbon equivalent value of steel according to the carbon equivalent of steel

where B is the width of the cold rolled strip, m;

carbon equivalent, wt.  C, Mn, Si the content of carbon, manganese and silicon in steel, wt. h _{x k the} thickness of the cold-rolled strip, mm;
v _{n p} rolling speed, m / s.

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