CN104785527B - Emulsion direct-injection system spray distance determines method - Google Patents

Abstract

The invention discloses a kind of emulsion direct-injection system spray distance and determine method, its oil film thickness formed when being determined by coefficient of friction to determine belt steel rolling, the maximum oil film thickness formed further according to belt steel surface determine emulsion at belt steel surface can the time of staying, finally according to emulsion at belt steel surface can the time of staying and strip speed, obtain the nozzle distance to milling train center, i.e. emulsion direct-injection system spray distance.

Description

Method for determining spraying distance of emulsion direct-injection system

Technical Field

The invention relates to an emulsion spraying control method, in particular to an emulsion spraying distance determination method.

Background

When the cold-rolled strip steel with thin specification and high precision is produced, a cold rolling unit or a secondary cold rolling unit is included, particularly the secondary cold rolling unit needs to lubricate a roll gap by using a water-oil emulsion direct injection mode. The emulsion is made in a mixing box with adjustable water quantity and oil quantity, and is delivered to different spray racks to be sprayed on the surface of a steel plate, and after a period of time, lubricating oil films are formed on the upper surface and the lower surface of the strip steel and a rolling area, so that the stability of the rolling process is ensured.

In the process of rolling strip steel, an emulsion spraying system is generally divided into an emulsion circulating system and an emulsion direct-injection system. The emulsion circulating system is widely applied under various rolling conditions, and as shown in fig. 1, the emulsion is sprayed on the surface of a roller A or a strip steel B by a nozzle C, so that the roller is cooled on one hand, and the rolling process is lubricated on the other hand. The direct emulsion spraying system is characterized in that the emulsion is directly discharged after being used and cannot be recycled, and the system is characterized in that the emulsion is sprayed on the surface of the strip steel B at a certain distance from a roll gap by a nozzle C and forms a lubricating oil film with uniform thickness on the surface of the strip steel after a certain time. In contrast, the ESI value of the emulsion in the emulsion direct injection system is high, the oil-water two-phase system is stable, a lubricating oil film can be formed on the surface of the strip steel only after a certain time, but the thickness of the oil film is more stable and uniform, so that the emulsion direct injection system is particularly suitable for products with high requirements on surface quality in cold rolling.

The determination of the distance from the nozzle to the center of the rolling mill is particularly important in consideration of the characteristic of oil film formation on the surface of the strip steel in an emulsion direct injection system. The distance is too large, the emulsion drips everywhere to pollute peripheral equipment, and the whole volume of the equipment is too large; if the distance is too small, the time required for forming the oil film on the surface of the strip steel is insufficient, so that the oil film thickness is too small, the oil film thickness distribution is not uniform, and the phenomenon of insufficient lubrication occurs.

The existing method for determining the distance from the nozzle to the center of the rolling mill generally adopts an analogy method, namely, the design is carried out by referring to the distance set value of a unit which is produced more stably at home and abroad. The defects of the adoption of the category comparison method are obvious, on one hand, the equipment composition, the product structure, the production working condition and the like of each unit are different, and the rationality of the current design cannot be guaranteed; on the other hand, the reference unit data is limited, and the comprehensive comparison cannot be realized. Therefore, after the actual operation of equipment, the phenomenon of insufficient lubrication can occur in the direct injection system of part of units under the original design flow, although technicians can make up for the insufficient lubrication by increasing the flow and the like, the problem of insufficient lubrication is relieved by blind flow increase, but the problem of emulsion splashing is caused, so that the surface quality of the strip steel is seriously influenced. Therefore, how to reasonably determine the distance from the nozzle to the center of the rolling mill, namely the spraying distance of the emulsion direct injection system, becomes the key for improving the working performance of the direct injection system.

Disclosure of Invention

The invention aims to provide a method for determining the spraying distance of an emulsion direct injection system, which can accurately determine the distance between a spray head and the center of a rolling mill, thereby ensuring the effect of direct injection of emulsion and obtaining a strip steel product with high surface quality.

In order to achieve the above object, the present invention provides a method for determining a spraying distance of an emulsion direct injection system, which comprises the following steps:

(1) determining the friction coefficient mu between the rolling mill and the strip steel under the condition of sufficient lubrication_j：

${\mathrm{\μ}}_j=\frac{Q_{F_j}-1.08-1.08+1.02r_j}{1.79r_j\sqrt{1-r_j}\·\sqrt{\frac{{R^{\′}}_j}{h_{1j}}}}$

$Q_{Fj}=\frac{P_j}{(K_{mj}-{\mathrm{\ξ}}_j)\·B_j\·\sqrt{{R^{\′}}_j{\mathrm{\Δh}}_j}}-\frac{2}{3}\sqrt{\frac{1-{v_j}^2}{E_j}{K}_{mj}\frac{h_{1j}}{{\mathrm{\Δh}}_j}};$

Wherein: r is_jThe reduction rate of the frame is shown,h_1jrepresents the outlet thickness in mm; h is_0jRepresents the inlet thickness in mm; r'_jRepresents the flattening radius of the working roll, and the unit is mm; p_jRepresents the rolling force in KN; k_mjRepresenting the pass average deformation resistance in MPa ξ_jRepresenting the equivalent tension influence coefficient, ξ_j＝0.3σ_1j+0.7σ_0j，σ_1jIs the pre-tensile stress in MPa, σ_0jIs the post-tensile stress in MPa; b is_jRepresenting the width of the strip steel, and the unit is mm; Δ h_jDenotes the absolute reduction in pass,. DELTA.h_j＝h_0j-h_1j；v_jRepresents the poisson's ratio; e_jRepresenting the elastic modulus of the strip steel; q_FjRepresenting an intermediate parameter in the calculation process;

(2) determining the oil film thickness lambda of the strip steel in the rolling process under the current working condition_j：

${\mathrm{\λ}}_j=\frac{1}{a_1}ln\frac{{\mathrm{\μ}}_j-a_2}{a_3}$

Wherein, a₁、a₂、a₃As model coefficients, a₁＝-3.0100、a₂＝0.0126、a₃＝0.1416；

(3) Thickness of oil film lambda_jWith a maximum oil film thickness lambda required during rolling of an initially set unit product_maxComparing, and taking the larger one as the final maximum oil film thickness lambda_max'；

(4) Determining the maximum oil film thickness lambda which can be actually achieved by the unit₀：

λ₀＝ηλ_max'

Wherein eta is 1.0 to 1.3;

(5) determining the maximum oil film thickness lambda which can be actually achieved by the unit₀Critical formation time t:

$t=\frac{{\mathrm{\λ}}_0-b_1}{b_2}$

wherein, b₁、b₂As model coefficients, b₁＝0.1766、b₂＝4.4595；

(6) Determining the distance s of the nozzle from the center of the rolling mill^*：

$s^{*}=\stackrel{\‾}{v}\·t$

Wherein,the average rolling speed of the rolling mill is shown,the unit is m/s.

The inventor finds out through research that the reasons for insufficient lubrication are that the distance from a nozzle to the center of a rolling mill is too small, the emulsion on the surface of a strip steel cannot form an oil film with enough thickness in a limited time under normal flow of the emulsion, and the distribution is not uniform. The oil film formed when the flow is increased is ideal, but the emulsion is seriously dropped and splashed. In addition, the inventor also finds that the oil film thickness at the roll gap has a certain functional relationship with the friction coefficient in the cold rolling process, so that the formed oil film thickness can be calculated by determining the friction coefficient. In addition, according to the mechanism of forming the lubricating oil film on the surface of the strip steel in a direct injection system, the thickness of the oil film formed on the surface of the strip steel in high-speed motion and the staying time of the emulsion on the surface of the strip steel are approximately in a linear relationship, so that the distance from the nozzle to the center of the rolling mill can be obtained through the time and the running speed of the strip steel.

The method for determining the spraying distance of the emulsion direct injection system can quickly and accurately determine the distance between the spray head and the center of the rolling mill, thereby ensuring the direct injection effect of the emulsion and obtaining a strip steel product with high surface quality.

Drawings

FIG. 1 is a schematic injection diagram of an emulsion circulation system.

FIG. 2 is a schematic injection diagram of an emulsion direct injection system.

Fig. 3 is a schematic flow chart illustrating steps of a method for determining a spraying distance of an emulsion direct injection system according to an embodiment of the present invention.

Detailed Description

The method for determining the spraying distance of the direct emulsion injection system according to the present invention will be further explained and illustrated with reference to the drawings and the specific embodiments of the present specification, however, the explanation and the illustration should not be construed as an undue limitation on the technical solution.

As shown in fig. 3, the spraying distance of the emulsion direct injection system is determined according to the following steps:

(0) starting;

(1) collecting all the technological parameters of the products with m specifications produced by the unit under the condition of sufficient lubrication:

-average rolling speed; p_j-rolling force; k_mjPass average deformation resistance ξ_jEquivalent tension influence factor, ξ_j＝0.3σ_1j+0.7σ_0j，σ_1jFront tensile stress, σ_0j-post-tensile stress; b is_j-strip width; r'_j-working roll flattening radius; Δ h_jAbsolute reduction in pass,. DELTA.h_j＝h_0j-h_1j，h_0jInlet thickness, h_1j-outlet thickness; r is_j-the reduction rate of the stand,E_j-strip modulus of elasticity; v. of_j-a poisson's ratio; m 18, j 1,2,.., m;

(2) the maximum oil film thickness lambda required to be reached in the rolling process of the unit product_maxMaximum oil film thickness lambda which can be actually achieved by the unit₀＝0；

(3) Let 1 be a process variable j characterizing the product specification;

(4) judging whether an inequality j is less than or equal to m, if so, turning to the step (5); otherwise, turning to the step (8);

(5) calculating the friction coefficient mu between the rolling mill and the strip steel under the condition of sufficient lubrication_jThe calculation formula is as follows:

${\mathrm{\μ}}_j=\frac{Q_{F_j}-1.08-1.08+1.02r_j}{1.79r_j\sqrt{1-r_j}\·\sqrt{\frac{{R^{\′}}_j}{h_{1j}}}}$

$Q_{Fj}=\frac{P_j}{(K_{mj}-{\mathrm{\ξ}}_j)\·B_j\·\sqrt{{R^{\′}}_j{\mathrm{\Δh}}_j}}-\frac{2}{3}\sqrt{\frac{1-{v_j}^2}{E_j}{K}_{mj}\frac{h_{1j}}{{\mathrm{\Δh}}_j}}$

(6) calculating the thickness of an oil film when the j specification strip steel is rolled under the current working condition:

${\mathrm{\λ}}_j=\frac{1}{a_1}ln\frac{{\mathrm{\μ}}_j-a_2}{a_3}$

model coefficient a₁＝-3.0100、a₂＝0.0126、a₃＝0.1416；

(7) Determine inequality lambda_j＞λ_maxIf yes, let λ_max＝λ_jIf j is j +1, the step (4) is carried out, otherwise, the step (4) is carried out;

(8) maximum oil film thickness lambda which can be actually achieved by computer set₀：

λ₀＝ηλ_max

Wherein the safety factor η is 1.10; (λ here)_maxI.e. lambda in its claims_max', i.e. the determined final maximum oil film thickness)

(9) Calculating the critical formation time t of the maximum oil film thickness:

$t=\frac{{\mathrm{\λ}}_0-b_1}{b_2}$

model coefficient b₁＝0.1766、b₂＝4.4595；

(10) Calculating the optimal distance s from the nozzle to the center of the mill^*，

(11) And (6) ending.

It is to be noted that the above lists only specific embodiments of the present invention, and it is obvious that the present invention is not limited to the above embodiments, and many similar variations follow. All modifications which would occur to one skilled in the art and which are, therefore, directly derived or suggested from the disclosure herein are deemed to be within the scope of the present invention.

Claims (1)

1. A method for determining the spraying distance of an emulsion direct injection system is characterized by comprising the following steps:

(1) determining the friction coefficient mu between the rolling mill and the strip steel under the condition of sufficient lubrication_j：

${\mathrm{\μ}}_j=\frac{Q_{F_j}-1.08+1.02r_j}{1.79r_j\sqrt{1-r_j}\·\sqrt{\frac{{R^{\′}}_j}{h_{1j}}}}$

$Q_{Fj}=\frac{P_j}{\left(K_{mj}-{\mathrm{\ξ}}_j\right)\·B_j\·\sqrt{{R^{\′}}_j{\mathrm{\Δh}}_j}}-\frac{2}{3}\sqrt{\frac{1-{v_j}^2}{E_j}{K}_{mj}\frac{h_{1j}}{{\mathrm{\Δh}}_j}};$

Wherein: r is_jThe reduction rate of the frame is shown,h_1jrepresents the outlet thickness in mm; h is_0jRepresents the inlet thickness in mm; r'_jRepresents the flattening radius of the working roll, and the unit is mm; p_jRepresents the rolling force in KN; k_mjRepresenting the pass average deformation resistance in MPa ξ_jRepresenting the equivalent tension influence coefficient, ξ_j＝0.3σ_1j+0.7σ_0j，σ_1jIs the pre-tensile stress in MPa, σ_0jIs the post-tensile stress in MPa; b is_jRepresenting the width of the strip steel, and the unit is mm; Δ h_jDenotes the absolute reduction in pass,. DELTA.h_j＝h_0j-h_1j；v_jRepresents the poisson's ratio; e_jRepresenting the elastic modulus of the strip steel; q_FjRepresenting an intermediate parameter in the calculation process;

(2) determining the oil film thickness lambda of the strip steel in the rolling process under the current working condition_j：

${\mathrm{\λ}}_j=\frac{1}{a_1}ln\frac{{\mathrm{\μ}}_j-a_2}{a_3}$

Wherein, a₁、a₂、a₃As model coefficients, a₁＝-3.0100、a₂＝0.0126、a₃＝0.1416；

(3) Thickness of oil film lambda_jWith a maximum oil film thickness lambda required during rolling of an initially set unit product_maxComparing, and taking the larger one as the final maximum oil film thickness lambda_max'；

(4) Determining the maximum oil film thickness lambda which can be actually achieved by the unit₀：

λ₀＝ηλ_max'

Wherein eta is 1.0 to 1.3;

(5) determining the maximum oil film thickness lambda which can be actually achieved by the unit₀Critical formation time t:

$t=\frac{{\mathrm{\λ}}_0-b_1}{b_2}$

wherein, b₁、b₂As model coefficients, b₁＝0.1766、b₂＝4.4595；

(6) Determining the distance s of the nozzle from the center of the rolling mill^*：

$s^{*}=\stackrel{\‾}{v}\·t$

Wherein,the average rolling speed of the rolling mill is expressed in m/s.