RU2288791C1 - Thin steel sheet cold rolling method - Google Patents

Abstract

FIELD: manufacturing processes for producing cold rolled thin steel sheets.

SUBSTANCE: method comprises steps of supplying lubricating liquid containing predetermined amount of palm oil to intervals between predetermined stands of continuous rolling mill. According to invention lubricating liquid is fed onto rolled strip before first stand of mill and, if necessary between second and third stands of mill. Palm oil is used multiply in reverse cycle of lubricating liquid having oiliness 0.3 - 0.4% at flow rate of palm oil in range 4 - 7 g/m² of rolled strip.

EFFECT: lowered production costs due to reduced consumption of palm oil without degrading product quality.

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Description

The invention relates to rolling production and can be used in the manufacture of cold rolled sheet steel, for example tin.

Such steel with a thickness of 0.18 ... 1.0 mm and a width of 730 ... 1000 mm with a tensile strength σ _of ≤370 MPa is currently rolled on five- or six-gauge continuous mills, similar to mill 1200 of OJSC Magnitogorsk Iron and Steel Works. The technology of cold rolling on a typical five-stand mill is described in sufficient detail, for example, in the book of N.I.Sheftel. Cold rolling of sheet steel. M., Metallurgy, 1966, p. 56-60.

A necessary element of the technology for rolling cold-rolled steel of the above parameters is the supply of a lubricant-cooling fluid (coolant) to the corresponding inter-stand spaces of the continuous mill, which provides the required amount of metal, reduces energy consumption during cold rolling and reduces the consumption of rolls. On stiffening mills, the composition of the coolant, as a rule, includes palm oil and some additives (additives) dissolved in water.

A known method of cold rolling of sheet metal in a continuous mill, in which to improve the quality of the strip by increasing the durability of the rolls, the strip between the I and II stands is stretched to create a specific tension of a certain value (see AS USSR No. 1044347, class. 21 In 1 / 26, published in BI No. 36, 1983). However, this method does not talk about the use of coolant during rolling (as well as its main characteristics), which complicates the implementation of the known technology.

The closest analogue to the claimed method is the rolling technology of tin, described in the reference Benyakovsky M.A. and other Technology rolling production, book 2., M., Metallurgy, 1991, S. 664-669.

This technology includes the supply of a certain composition of coolant to the specified interstand spaces of a continuous cold rolling mill and is characterized by the fact that the said liquid (emulsion) contains palm oil and water with a ratio of their quantities 1/3 ... 1/7 depending on the thickness of the strip, and total oil consumption per 1 ton of rolled stock is 1.8 ... 2.5 kg.

The disadvantage of this method (technology) is the increased consumption of palm oil supplied before the mill II, III, IV and V, which increases production costs due to the significant cost of imported oil.

Indeed, as shown by testing of the proposed method (see below), it is possible to reduce the consumption of this oil without compromising the quality level of rolled sheet.

An object of the invention is to reduce production costs by reducing the consumption of palm oil during cold rolling of sheet steel.

To solve this problem in a rolling method, mainly tin, including the supply of a cutting fluid containing a certain amount of palm oil to predetermined intercellular spaces of a continuous mill, said fluid is fed to the rolled strip in front of the first mill stand and, if necessary, between the second and a third stand, while palm oil is repeatedly used in the coolant cycle with its fat content of 0.3 ... 0.4% with the consumption of this oil in the range of 4 ... 7 g per 1 m ² of strip surface.

The essence of the proposed technical solution lies in the fact that coolant is supplied only in one (maximum - two) intervals of a continuous mill without adding palm oil for a certain period (with coolant fat content of at least 0.3%), and oil consumption is not more than 7 g per unit surface (area) rolled strip.

This becomes possible, because, firstly, there is still grease on the strip from oiling it after etching of the hot-rolled metal, which serves as a tackle for tin. Secondly, when the coolant supply cycle is flowing back into the crankcase of the mill and again fed to the strip, it is enough to have the indicated optimal palm oil flow rate.

The need for additional coolant supply between the mill stands II and III may arise with some wear of the work rolls (not affecting the quality of finished products), as well as when rolling strips of increased strength (up to 450 ... 470 MPa) and thickness (more than 0, 3 ... 0.4 mm).

Establishing the palm oil consumption rate per unit of rental area (1 m ² ) simplifies the necessary technical and economic calculations, since the consumption rate in kg / t (as in the method chosen as the closest analogue) with a significant weight range of 1 m2 ^of rental (for strip 0.18 × 730 mm, this value is 1.03 kg, and for 1.0 × 1000 mm - 7.85 kg) becomes, in fact, an abstract value. For technologists, it is important to know exactly the amount of lubricant supplied per unit area of strip metal.

Experimental verification of the proposed method was carried out on a five-stand mill 1200 of OJSC MMK.

For this purpose, when rolling strips with a thickness of 0.18 ... 0.60 mm and a width of 730 ... 1000 mm from st.08kp, ps, the place of coolant supply at the mill was varied, periodically monitoring its fat content, as well as the consumption of palm oil. The results of the experiments were evaluated by the quality of the rolled metal.

The best results (first grade tin yield up to 99.2% with a minimum consumption of palm oil) were obtained using the proposed technology. Deviations from it reduced the yield of grade I.

So, when coolant was supplied between the mill stands I and II (at the above emulsion fat content and palm oil consumption), grade I yield was 98.5 ... 98.8% due to the appearance of longitudinal scratches on the strips from the partial slip of the rolls I crates. A similar result (with a decrease in the yield of grade I to 98%) was observed with a coolant content of less than 3% and a decrease in palm oil consumption to 2 ... 3 g of 1 m ² strip.

An increase in coolant fat (up to 0.7%) did not lead to an increase in grade I production, but adversely affected the quality of tin when it was annealed after cold rolling (the appearance of soot stains on metal). An increase in the consumption of palm oil to 8 ... 10 g / m did not lead to an increase in the yield of tin I grade.

Rolling on partially worn rolls, in particular, strips of steel with σ _in > 370 MPa with a thickness of 0.5 ... 0.8 mm, without additional coolant supply between the stands II and III, reduced the yield of grade I to 97.5% .

An experimental rolling of tin was also carried out using technology taken as the closest analogue. In this case, the yield of tin I grade did not exceed 99%, and the consumption of palm oil was, on average, 9 g / m ² , which led to a corresponding increase in labor costs.

Thus, a pilot test confirmed the acceptability of the technical solution found to achieve the goal and its advantages over the known technology.

According to technical and economic studies conducted at the Central Control Laboratory of OJSC MMK, the use of the proposed technology for rolling sheet steel (mainly sheet metal) will increase the profit from the sale of finished steel by at least 10%, due to lower production costs by reducing palm oil consumption without compromising product quality.

Case Studies

1. 08kp sheet steel (tin) with a section of 0.35 × 750 mm is rolled on a five-stand mill.

A cutting fluid with a fat content of 0.4% is fed to the strip in front of the first mill stand. The consumption of palm oil, which is part of the coolant, is 6 g / m ² .

2. 08ps steel strip with a cross section of 0.7 × 1000 mm with σ _in = 450 MPa is rolled on the same mill.

Coolant with a fat content of 0.3% is supplied before the first stand and in the interval between the second and third stands. The consumption of palm oil is 5 g / m ² .

Claims (1)

A method of cold rolling thin-sheet steel, mainly tin, comprising supplying a cutting fluid containing palm oil to predetermined intervals of a continuous mill, characterized in that said liquid is fed to the strip to be rolled in front of the first mill stand and, if necessary, between the second and the third stand, while palm oil is repeatedly used in the reverse cycle of the cutting fluid with its fat content of 0.3-0.4% with a flow rate of this oil in the range of 4-7 g per 1 m ² of strip surface.