阅读说明：本技术 热镀锌带钢镀层厚度切换的控制方法 (Control method for switching thickness of hot-dip galvanized strip steel coating ) 是由 任新意 高慧敏 郑艳坤 刘醒 王振鹏 雷振尧 杨腾 徐海卫 周欢 于孟 李冉 于 2021-07-27 设计创作，主要内容包括：本发明提供了一种热镀锌带钢镀层厚度切换的控制方法,包括：对上一卷热镀锌带钢镀层厚度W-(1)和下一卷热镀锌带钢镀层厚度W-(2)进行测量；根据上一卷热镀锌带钢镀层厚度W-(1)和下一卷热镀锌带钢镀层厚度W-(2)的差值对热镀锌带钢镀层厚度的变换模式进行判定；根据热镀锌带钢镀层厚度的变换模式的判定结果对气刀参数进行调整。本申请实施例通过提供一种热镀锌带钢镀层厚度切换的控制方法,解决了现有技术中带钢锌层厚度切换时的气刀参数调整不及时和精度差的技术问题,在保证带钢镀层厚度满足客户标准的前提下,最大程度的减少了锌层耗费成本。(The invention provides a control method for thickness switching of a hot-dip galvanized strip steel coating, which comprises the following steps: the thickness W of the coating of the previous coil of hot-dip galvanized strip steel 1 And the thickness W of the coating of the next coil of hot-dip galvanized steel strip 2 Carrying out measurement; according to the thickness W of the coating layer of the previous coil of hot galvanized strip steel 1 And the thickness W of the coating of the next coil of hot-dip galvanized steel strip 2 Judging the transformation mode of the hot-dip galvanized strip steel coating thickness by the difference value; and adjusting the air knife parameters according to the judgment result of the transformation mode of the hot-dip galvanized strip steel coating thickness. The embodiment of the application provides a control method for thickness switching of a hot-dip galvanized steel strip coating, solves the technical problems of untimely adjustment of air knife parameters and poor precision during thickness switching of a zinc layer of a steel strip in the prior art, and reduces the zinc layer to the maximum extent on the premise of ensuring that the thickness of the steel strip coating meets the customer standardCosts are consumed.)

1. A control method for switching the thickness of a hot-dip galvanized strip steel coating is characterized by comprising the following steps:

the thickness W of the coating of the previous coil of hot-dip galvanized strip steel₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Carrying out measurement;

according to the thickness W of the coating layer of the previous coil of hot galvanized strip steel₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Judging the transformation mode of the hot-dip galvanized strip steel coating thickness by the difference value;

and adjusting the air knife parameters according to the judgment result of the transformation mode of the hot-dip galvanized strip steel coating thickness.

2. The method for controlling the thickness switching of the hot-dip galvanized steel strip coating according to claim 1, wherein the adjusting of the air knife parameters according to the determination result of the conversion mode of the hot-dip galvanized steel strip coating thickness comprises:

according to the traditional hot galvanizing strip steel zinc layer thickness theoretical model: w ═ K ═ V^a*D^b*P^cAnd the thickness of the hot-dip galvanized steel strip and the thickness of the zinc layers on the upper surface and the lower surface of the hot-dip galvanized steel strip, the theoretical formula is expressed as follows:

wherein e is a natural constant, W is a zinc layer thickness, P is an air knife pressure, TH is a strip steel thickness, D is an air knife distance, V is a strip steel speed, H is an air knife height, k is₀、k₁、k₂、k₃、k₄With a fixed constant, the above equation is linearized to yield:

collecting large data air knife pressure P, air knife distance D, strip steel speed V, air knife height H and corresponding zinc layer thickness W data in field production, and obtaining each fixed constant value k through model parameter identification in formula (1)₀、k₁、k₂、k₃、k₄To obtain a regressive mathematical model:

in the production process, when the speed of the strip steel or the thickness of a set zinc layer changes, the technological parameters of the air knife are adjusted, and the corresponding adjustment quantity of the technological parameters of the air knife is calculated according to the model, wherein the corresponding adjustment quantity is as follows:

in the formula, TH₁The thickness of the hot-dip galvanized steel strip of the previous coil, W₁For the thickness of the coating layer, P, of the previous coil of hot-dip galvanized strip steel₁Air knife pressure for the previous coil of hot-dip galvanized strip steel, D₁Air knife distance H for the previous coil of hot-dip galvanized strip steel₁The height of an air knife TH of the previous coil of hot-dip galvanized steel strip₂The thickness of the next coil of hot-dip galvanized steel strip, W₂For the next coil of hot-dip galvanized strip steel coating thickness, P₂Air knife pressure for the next coil of hot-dip galvanized strip steel, D₂Air knife distance H for the next coil of hot-dip galvanized strip steel₂The height of the air knife of the next coil of hot-dip galvanized steel strip.

3. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 2, characterized in that:

when the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference of-3 g/m²≤W₁-W₂≤3g/m²Then, the change mode of the thickness of the hot-dip galvanized strip steel coating is judged to be the same coatingMode(s).

4. The method for controlling the switching of the coating thickness of the hot-dip galvanized strip steel according to claim 3, characterized in that:

when the changing mode of the hot dip galvanized strip steel coating thickness is the same coating mode, the air knife parameters are kept unchanged.

5. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 2, characterized in that:

when the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W of₁-W₂>3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning the thickness of the coating.

6. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 5, characterized in that:

when the transformation mode of the hot-dip galvanized strip steel coating thickness is the coating thickness thinning mode, the air knife parameter is L after the welding seam_aThe adjustment is started at the position.

7. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 6, characterized in that:

according to the formula (4) and the formula (6), the air knife pressure is controlled from P₁Adjusted to P₂Height of air knife is set by H₁Adjusted to H₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P₁The variation Δ H of the height of the air knife is H₂-H₁The air knife distance remains unchanged;

according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting height of air knife_H＝ΔH/v_HTime t for adjusting air knife distance_D0, the longest length required for adjusting all parameters of the air knifeTime is max (t)_P,t_H,t_D)；

Finally obtaining the air knife parameter L after the welding seam_a＝V*max(t_P,t_H,t_D) The adjustment is started at the position.

8. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 2, characterized in that:

when the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W1-W₂<-3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning and thickening the coating.

9. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 8, characterized in that:

when the transformation mode of the hot-dip galvanized strip steel coating thickness is a coating thickness-changing mode, the air knife parameter is L before the welding line_bThe adjustment is started at the position.

10. The method for controlling the thickness switching of the coating of the hot-dip galvanized steel strip as claimed in claim 9, characterized in that:

according to the formula (4) and the formula (5), the air knife pressure is controlled from P₁Adjusted to P₂Air knife distance is from D₁Adjusted to D₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P₁The air knife distance variation Δ D ═ D₂-D₁The height of the air knife is kept unchanged;

according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting air knife distance_D＝ΔD/v_DTime t for adjusting height of air knife_HThe maximum time required for the adjustment of all the parameters of the air knife is max (t) equal to 0_P,t_H,t_D)；

Finally, the air knife parameters are obtainedBefore the weld joint L_b＝V*max(t_P,t_H,t_D) The adjustment is started at the position.

Technical Field

The invention relates to the technical field of cold rolling, in particular to a control method for thickness switching of a hot-dip galvanized strip steel coating.

Background

The hot-dip galvanized steel strip has good mechanical property and corrosion resistance, and is widely applied to the industries of automobiles, household appliances, buildings and the like. The thickness of the coating is an important performance index for measuring hot-dip galvanized strip steel, and the spot weldability and adhesiveness of the product are influenced by the fact that the zinc layer is too thick, and meanwhile, zinc raw materials are wasted; the corrosion resistance of the product is affected by the thinness of the zinc layer, and the requirement of customers cannot be met. Therefore, the control precision of the strip steel coating thickness is directly related to the product quality and the production cost, and the improvement of the zinc layer thickness precision of the hot galvanizing strip steel is a common concern of hot galvanizing production enterprises and metallurgical equipment suppliers at home and abroad.

At present, in the process of switching the coating thickness of most hot galvanizing units in China, the control of the coating thickness of strip steel still depends on the production experience of workers and adopts a manual control mode, air knife parameters cannot be adjusted timely and accurately, long-time coating thickness out-of-tolerance is caused, and even the coating thickness standard of a client is not met, so that the product quality is objectified. Although a small part of hot galvanizing production lines adopt PID closed-loop control on air knife parameters, the control effect is not ideal due to the fact that process variables influencing the thickness of a coating are complex, particularly the influence of an air knife adjusting mechanism on the thickness of the coating is nonlinear, and meanwhile, the control effect is also very poor in consideration of large time lag between the detection of the thickness of a strip steel zinc layer and the adjustment of the air knife parameters.

Disclosure of Invention

The embodiment of the application provides a control method for thickness switching of a hot-dip galvanized steel strip coating, solves the technical problems of untimely adjustment of air knife parameters and poor precision during thickness switching of a zinc layer of a steel strip in the prior art, and reduces the cost of zinc layer consumption to the greatest extent on the premise of ensuring that the thickness of the steel strip coating meets the customer standard.

The embodiment of the application provides a control method for thickness switching of a hot-dip galvanized strip steel coating, which comprises the following steps:

the thickness W of the coating of the previous coil of hot-dip galvanized strip steel₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Carrying out measurement;

according to the thickness W of the coating layer of the previous coil of hot galvanized strip steel₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Judging the transformation mode of the hot-dip galvanized strip steel coating thickness by the difference value;

and adjusting the air knife parameters according to the judgment result of the transformation mode of the hot-dip galvanized strip steel coating thickness.

Further, the adjusting the air knife parameters according to the determination result of the change mode of the coating thickness of the hot-dip galvanized steel strip comprises:

according to the traditional hot galvanizing strip steel zinc layer thickness theoretical model: w ═ K ═ V^a*D^b*P^cAnd the thickness of the hot-dip galvanized steel strip and the thickness of the zinc layers on the upper surface and the lower surface of the hot-dip galvanized steel strip, the theoretical formula is expressed as follows:

wherein e is a natural constant, W is a zinc layer thickness, P is an air knife pressure, TH is a strip steel thickness, D is an air knife distance, V is a strip steel speed, H is an air knife height, k is₀、k₁、k₂、k₃、k₄With a fixed constant, the above equation is linearized to yield:

collecting large data air knife pressure P, air knife distance D, strip steel speed V, air knife height H and corresponding zinc layer thickness W data in field production, and obtaining each fixed constant value k through model parameter identification in formula (1)₀、k₁、k₂、k₃、k₄And a regression mathematical model can be obtained:

in the production process, when the speed of the strip steel or the thickness of a set zinc layer changes, the technological parameters of the air knife are timely adjusted, the corresponding adjustment quantity of the technological parameters of the air knife is calculated according to the model, and the corresponding adjustment quantity is as follows:

in the formula, TH₁The thickness of the hot-dip galvanized steel strip of the previous coil, W₁For the thickness of the coating layer, P, of the previous coil of hot-dip galvanized strip steel₁Air knife pressure for the previous coil of hot-dip galvanized strip steel, D₁Air knife distance H for the previous coil of hot-dip galvanized strip steel₁The height of an air knife TH of the previous coil of hot-dip galvanized steel strip₂The thickness of the next coil of hot-dip galvanized steel strip, W₂For the next coil of hot-dip galvanized strip steel coating thickness, P₂Air knife pressure for the next coil of hot-dip galvanized strip steel, D₂Air knife distance H for the next coil of hot-dip galvanized strip steel₂The height of the air knife of the next coil of hot-dip galvanized steel strip.

Further, when the thickness W of the coating of the hot-dip galvanized steel strip of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference of-3 g/m²≤W₁-W₂≤3g/m²And judging the conversion mode of the thickness of the hot-dip galvanized strip steel coating to be the same coating mode.

Further, when the change mode of the hot dip galvanized strip steel coating thickness is the same coating mode, the air knife parameters are kept unchanged.

Further, when the thickness W of the coating of the hot-dip galvanized steel strip of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W of₁-W₂>3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning the thickness of the coating.

Further, when the transformation mode of the hot-dip galvanized strip steel coating thickness is the coating thickness thinning mode, the air knife parameter is L after the welding seam_aThe adjustment is started at the position.

Further, according to the formula (4) and the formula (6), the air knife pressure is controlled from P₁Adjusted to P₂Height of air knife is set by H₁Adjusted to H₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P₁The variation Δ H of the height of the air knife is H₂-H₁Air knife distance protectionKeeping unchanged;

according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting height of air knife_H＝ΔH/v_HTime t for adjusting air knife distance_DThe maximum time required for the adjustment of all the parameters of the air knife is max (t) equal to 0_P,t_H,t_D)；

Finally obtaining the air knife parameter L after the welding seam_a＝V*max(t_P,t_H,t_D) The adjustment is started at the position.

Further, when the thickness W of the coating of the hot-dip galvanized steel strip of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W1-W₂<-3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning and thickening the coating.

Further, when the transformation mode of the hot-dip galvanized strip steel coating thickness is a coating thin and thick changing mode, the air knife parameter is L before the welding seam_bThe adjustment is started at the position.

Further, according to the formula (4) and the formula (5), the air knife pressure is controlled from P₁Adjusted to P₂Air knife distance is from D₁Adjusted to D₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P₁The air knife distance variation Δ D ═ D₂-D₁The height of the air knife is kept unchanged;

according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting air knife distance_D＝ΔD/v_DTime t for adjusting height of air knife_HThe maximum time required for the adjustment of all the parameters of the air knife is max (t) equal to 0_P,t_H,t_D)；

Finally obtaining the air knife parameter L before the welding seam_b＝V*max(t_P,t_H,t_D) BitThe process begins to adjust.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

(1) the method for judging and adjusting the hot-dip galvanized strip steel coating thickness switching mode can meet the flexible adjustment under the condition of switching different strip steel coating thicknesses, and avoids the product use problem caused by the fact that the strip steel coating thickness does not meet the customer standard;

(2) the calculation method for the air knife parameter adjustment starting point provided by the invention combines the process conditions of the air knife adjustment mechanism response rate, the strip steel production speed and the like, and reduces the zinc consumption cost to the maximum extent on the premise of meeting the strip steel coating thickness standard of a client.

Drawings

Fig. 1 is a process flow chart of a control method for switching the coating thickness of a hot-dip galvanized steel strip according to an embodiment of the present disclosure;

FIG. 2 is a graph showing a variation of parameters of a gas knife in a same coating mode according to a second embodiment of the present application;

FIG. 3 is a graph of a variation of a gas knife parameter in a coating thickness thinning mode according to a second embodiment of the present application;

fig. 4 is a graph of the variation of the parameters of the air knife in the thin and thick plating mode provided in the second embodiment of the present application.

Detailed Description

The invention provides a control method for the thickness switching of a hot-dip galvanized strip steel coating, which judges different modes of the thickness switching of the strip steel coating through comparison and analysis by reading the preset coating thickness of the current production coil strip steel and the preset coating thickness of the next production coil strip steel. Meanwhile, the reasonable starting point of air knife parameter adjustment is determined by theoretical calculation by considering the air knife process parameter adjustment amount in different strip steel coating thickness switching modes and combining the response speed of an air knife adjusting mechanism and the real-time running speed of strip steel, so that the cost of zinc layer consumption is reduced to the maximum extent on the premise of ensuring that the strip steel coating thickness meets the customer standard.

In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.

Example one

The embodiment of the application provides a control method for thickness switching of a hot-dip galvanized strip steel coating, which comprises the following steps:

step S1: the thickness W of the coating of the previous coil of hot-dip galvanized strip steel₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Carrying out measurement;

step S2: according to the thickness W of the current hot-dip galvanized strip steel coating₁The thickness value W of the coating of the next coil of hot-dip galvanized steel strip₂Judging the transformation mode of the hot-dip galvanized strip steel coating thickness by the difference value; when the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference of-3 g/m²≤W₁-W₂≤3g/m²And judging the conversion mode of the thickness of the hot-dip galvanized strip steel coating to be the same coating mode. When the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W of₁-W₂>3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning the thickness of the coating. When the thickness W of the hot-dip galvanized strip steel of the previous coil₁And the thickness W of the coating of the next coil of hot-dip galvanized steel strip₂Difference value W1-W₂<-3g/m²And judging the mode of changing the thickness of the hot-dip galvanized strip steel coating to be the mode of thinning and thickening the coating.

Wherein the step S3 of adjusting the air knife parameter according to the determination result of the conversion mode of the hot-dip galvanized strip steel coating thickness includes:

according to the traditional hot galvanizing strip steel zinc layer thickness theoretical model: w ═ K ═ V^a*D^b*P^cAnd the thickness of the hot-dip galvanized steel strip and the thickness of the zinc layers on the upper surface and the lower surface of the hot-dip galvanized steel strip, the theoretical formula is expressed as follows:

in the formula, e is the natural constantThe number W is the thickness of the zinc layer, P is the air knife pressure, TH is the thickness of the strip steel, D is the air knife distance, V is the strip steel speed, H is the air knife height, k₀、k₁、k₂、k₃、k₄With a fixed constant, the above equation is linearized to yield:

collecting large data air knife pressure P, air knife distance D, strip steel speed V, air knife height H and corresponding zinc layer thickness W data in field production, and obtaining each fixed constant value k through model parameter identification in formula (1)₀、k₁、k₂、k₃、k₄And a regression mathematical model can be obtained:

in the production process, when the speed of the strip steel or the thickness of a set zinc layer changes, the technological parameters of the air knife are timely adjusted, the corresponding adjustment quantity of the technological parameters of the air knife is calculated according to the model, and the corresponding adjustment quantity is as follows:

in the formula, TH₁The thickness of the hot-dip galvanized steel strip of the previous coil, W₁For the thickness of the coating layer, P, of the previous coil of hot-dip galvanized strip steel₁Air knife pressure for the previous coil of hot-dip galvanized strip steel, D₁Air knife distance H for the previous coil of hot-dip galvanized strip steel₁The height of an air knife TH of the previous coil of hot-dip galvanized steel strip₂The thickness of the next coil of hot-dip galvanized steel strip, W₂For the next coil of hot-dip galvanized strip steel coating thickness, P₂Air knife pressure for the next coil of hot-dip galvanized strip steel, D₂Air knife distance H for the next coil of hot-dip galvanized strip steel₂The height of the air knife of the next coil of hot-dip galvanized steel strip.

When the changing mode of the hot dip galvanized strip steel coating thickness is the same coating mode, the air knife parameters are kept unchanged.

When the transformation mode of the hot-dip galvanized strip steel coating thickness is the coating thickness thinning mode, the air knife parameter is L after the welding seam_aThe adjustment is started at the position. According to the formula (4) and the formula (6), the air knife pressure is controlled from P₁Adjusted to P₂Height of air knife is set by H₁Adjusted to H₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P_1,Air knife height variation Δ H ═ H₂-H₁The air knife distance remains unchanged; according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting height of air knife_H＝ΔH/v_HTime t for adjusting air knife distance_DThe maximum time required for the adjustment of all the parameters of the air knife is max (t) equal to 0_P,t_H,t_D) (ii) a Finally obtaining the air knife parameter L after the welding seam_a＝V*max(t_P,t_H,t_D) The adjustment is started at the position.

When the transformation mode of the hot-dip galvanized strip steel coating thickness is a coating thickness-changing mode, the air knife parameter is L before the welding line_bStarting to adjust at the position. According to the formula (4) and the formula (5), the air knife pressure is controlled from P₁Adjusted to P₂Air knife distance is from D₁Adjusted to D₂From this, the air knife pressure variation Δ P ═ P is obtained₂-P₁The air knife distance variation Δ D ═ D₂-D₁The height of the air knife is kept unchanged; according to the air knife pressure response speed v of the field air knife device_PAir knife height response rate v_HAir knife distance v_DObtaining the response speed air knife pressure adjusting time t_P＝ΔP/v_PTime t for adjusting air knife distance_D＝ΔD/v_DTime t for adjusting height of air knife_HThe maximum time required for the adjustment of all the parameters of the air knife is max (t) equal to 0_P,t_H,t_D) (ii) a Finally obtaining the air knife parameter L before the welding seam_b＝V*max(t_P,t_H,t_D) The adjustment is started at the position.

Example two

Taking the field production situation of a certain 1700 hot galvanizing unit as an example, the steel type of the strip steel of the current production coil is DX51D + Z, the thickness is 0.6mm, the width is 1250mm, and the preset coating thickness is 60g/m²The running speed of the strip steel is 120 m/min. The steel type and the specification of the strip steel of the next production coil are the same, the speed is kept unchanged, and the preset coating thickness is respectively considered to be 40g/m²、61g/m²、80g/m²The plating layer switching method is used.

According to the formula (3), when the thickness of the strip steel is 0.6mm, the speed of the strip steel is 120m/min, and the thickness of the zinc layer is 60g/m²When the air knife distance is 8mm and the air knife height is 300mm, the air knife pressure is 260 kpa. When the thickness of the zinc layer is changed to 40g/m²When the thickness of the zinc layer is regulated within a small range, the air knife pressure is preferably regulated, then the height of the air knife is regulated, the air knife distance is kept unchanged, according to the formula (4) and the formula (6), the air knife pressure is regulated from 260kpa to 430kpa, and the air knife height is regulated from 300mm to 500 mm. When the thickness of the zinc layer is changed to 80g/m²Firstly adjusting the air knife pressure, keeping the air knife height unchanged because the air knife height cannot meet the thickness requirement of a zinc layer, further adjusting the air knife distance, and controlling the air knife pressure to be 260kpa according to a formula (4) and a formula (5)The adjustment was 165kpa and the air knife distance was adjusted from 8mm to 7 mm. The air knife pressure, air knife distance and air knife height corresponding to different zinc layer thicknesses of the strip steel are shown in table 1.

Change of working condition	Thickness of strip steel	Thickness of coating	Air knife pressure	Air knife distance	Height of air knife	Strip speed
							0	0.6	60	260	8	300	120
1	0.6	61	260	8	300	120
							2	0.6	40	430	8	500	120
3	0.6	80	165	7	300	120

The air knife pressure P, the air knife distance D, and the air knife height H are three main process parameters of the air knife apparatus, and the adjustment capability per unit time is determined by the air knife apparatus itself. Taking the FOEN air knife equipment of a 1700mm hot galvanizing unit as an example, the response speed of the air knife pressure in the air knife equipment is v_PAir knife height response rate v 5.8kpa/s_H6.2mm/s, air knife distance response rate v_D＝0.5mm/s。

(1) The preset coating thickness of the strip steel of the next production coil is 61g/m²When the thickness of the coating layer is changed to 1g/m, the thickness of the coating layer is changed to 1g/m²And judging that the coating is switched to the same-coating mode, so that the air knife parameters of the strip steel of the next production coil are kept unchanged, namely the air knife height is 300mm, the air knife distance is 8mm, and the air knife pressure is 260kpa, as shown in figure 2.

(2) The preset coating thickness of the strip steel of the next production coil is 40g/m²In this case, the change of the plating layers of the front and rear coils was 20g/m²And judging that the coating is switched to a coating thickness thinning mode, so that the air knife parameter of the strip steel of the next production coil is L after the welding seam_aThe adjustment is started at the position.

As can be seen from table 1, the adjustment amount of the air knife parameter: air knife pressure from P₁260kpa to P₂430kpa, and the air knife pressure variation Δ P₂-P₁170 kpa; height of air knife from H₁300mm to H₂500mm, and the air knife height variation DeltaH is H₂-H₁200 mm; the air knife distance remains constant. The air knife pressure is adjusted for time t_P＝ΔP/v_P170/5.8-34.48 s; air knife height adjustment time t_H＝ΔH/v_H200/6.2-32.26 s; air knife distance adjustment time t_D0. The maximum time required for the air knife to adjust all parameters is max (t)_P,t_H,t_D)＝max(34.48,32.26,0)＝34.48s。

The running speed V of the strip steel is 120m/min, and the running distance L of the strip steel after the air knife parameter adjustment is finished_a＝V*max(t_P,t_H,t_D) 120/60 × 34.48 × 68.97m, i.e., the air knife parameters were adjusted 68.97m after the weld, as shown in fig. 3.

(3) The preset coating thickness of the strip steel of the next production coil is 80g/m²When the thickness of the coating is changed to-20 g/m due to the change of the coating of the front and rear coils²And judging that the coating is switched to a 'coating thickness-variable mode', so that the strip steel air knife parameter of the next production coil is L before the welding seam_bThe adjustment is started at the position.

As can be seen from table 1, the adjustment amount of the air knife parameter: air knife pressure from P₁Decrease to P260 kpa₂165kpa, air knife pressure change Δ P₁-P₂95 kpa; the height of the air knife is kept unchanged; air knife distance from D₁Reduced to D at 8mm₂7mm, and D represents the variation of air knife distance₁-D₂1 mm. The air knife pressure is adjusted for time t_P＝ΔP/v_P95/5.8-16.38 s; air knife height adjustment time t_H0; air knife distance adjustment time t_D＝ΔD/v_D1/0.5-2 s. The maximum time required for the air knife to adjust all parameters is max (t)_P,t_H,t_D)＝max(16.38,0,2)＝16.38s。

The running speed V of the strip steel is 120m/min,the running distance L of the strip steel after the air knife parameter adjustment is finished_bV max (tP, tH, tD) 120/60 × 16.38 ═ 32.76m, i.e. the air knife parameters need to be adjusted 32.76m before the weld, so that the strip coating thickness of the next coil can meet the customer standard, as shown in fig. 4.

The technical scheme in the embodiment of the application at least has the following technical effects or advantages:

(1) the method for judging and adjusting the strip steel coating thickness switching mode can meet the flexible adjustment of different strip steel coating thickness switching conditions, and avoids the product use problem caused by the fact that the strip steel coating thickness does not meet the customer standard;

(2) the calculation method for the air knife parameter adjustment starting point provided by the invention combines the process conditions of the air knife adjustment mechanism response rate, the strip steel production speed and the like, and reduces the zinc consumption cost to the maximum extent on the premise of meeting the strip steel coating thickness standard of a client.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.