A method for controlling the roughness of a galvanized product

Abstract

The application discloses a roughness control method of galvanized products, and the roughness general change law formula is obtained through analysis and induction, that is, the plate surface roughness=work roll surface roughness*overprint rate*wave peak use efficiency*steel grade coefficient k. The roughness control is converted from empirical data into a calculable, predictable and controllable control method, the organization, planning and accuracy of the product roughness control are improved, and the product delivery is ensured. The product surface roughness sharply decreases at 150t before the same rolling period, and the roughness linearly and uniformly decreases at 150-6000t; the specific production time of the product in the rolling period is obtained, the production scheme is planned in advance, the roughness controllable production is realized, and the roughness control precision is improved. The rolling force influence curve of the plate surface roughness is in a ladder distribution, and then the singleness that the roughness is only arranged according to the rolling period is broken, the roughness control means is enriched, and the roughness control achievement rate is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating process, and particularly relates to a roughness control method of galvanized product. BACKGROUND

[0002] The surface roughness Ra of the steel plate directly affects the stamping forming and metal flow characteristics, and a certain surface roughness is beneficial to store and maintain the oil film and improve the sliding property of the steel plate. However, if the roughness is too high, the oil amount stored in the concave part is increased, while the oil supply effect to the convex part is poor, thereby causing the oil amount in the convex part to be insufficient and the stress to be too concentrated, resulting in the damage of the oil film, the increase of the friction resistance of the steel plate, the poor flowability of the steel plate surface, and the decrease of the surface quality of the stamping formed steel plate.

[0003] The influence of Ra on the DOI (Distinctness of Image) of the coating quality. The DOI (Distinctness of Image) value is generally used in Europe and the United States and Japan to describe the appearance quality of the paint film. The corresponding term in Japan is called "freshness". The surface of the sheet used for automobile manufacturing is not a smooth plane, but a matte roughened surface, which is beneficial to the stamping oil storage lubrication and the appearance quality after the paint coating. The matte roughened surface is to rely on the rolling process to give the steel plate surface a certain roughness, and the appropriate roughness directly determines the appearance quality of the paint film. When the roughness is too large, the paint film is uneven and the flatness is not up to standard. When the roughness is too small, the paint film flows to form a flow pattern. Therefore, in the forming process of the galvanized sheet for automobiles, the surface roughness of the steel plate should be within a suitable range. After a large number of tests and researches, the surface roughness of the steel plate should be controlled within Ra 0.6-1.6 μm. SUMMARY

[0004] In order to improve the control precision of the roughness of the galvanized product, the present application provides a roughness control method of the galvanized product. The influence of the finishing mill rolling force and the rolling cycle on the surface roughness of the galvanized product is determined by studying the roughness change in the rolling cycle of the galvanized product, the production time of the galvanized product in one rolling cycle is controlled, and the target value of the roughness is obtained.

[0005] A roughness control method of a galvanized product, the surface roughness of the galvanized product is formed by the combined action of the roughness of the work roll, the zinc layer, the rolling force, the steel grade and other parameters, and the corresponding relationship between the surface roughness and the work roll surface roughness is:

[0006] Surface roughness = work roll surface roughness x impression rate x wave peak utilization efficiency x k; wherein,

[0007] Impression rate: 50% to 60%;

[0008] Wave peak utilization efficiency: 60% to 100%;

[0009] k is a steel grade coefficient.

[0010] An ideal curve of the roughness change of the plate surface is formulated, and a rolling cycle-Ra contrast graph is obtained.

[0011] Further, the roughness of the plate surface gradually decreases in the same rolling cycle; 150t is the demarcation point in the same rolling cycle, and the roughness sharply decreases in the rolling cycle of 0-150t; the roughness linearly and uniformly decreases in the rolling cycle of 150-6000t, and the roughness of the plate surface decreases by 0.1μm per rolling cycle of 1350t.

[0012] An ideal curve of the roughness change of the steel plate surface is formulated, and the curve first rapidly decreases and then slowly decays with the increase of the rolling cycle, and the turning point should be at 150t according to data analysis and should enter a stable period. Thus, a rolling cycle-Ra contrast graph is obtained in a rolling cycle, as shown in Figure 1 In the same rolling cycle, it can be found through data collection and analysis that the roughness of the plate surface gradually decreases, because the roughness of the working roll surface exists to a certain extent in the rolling process, and the degree of wear is continuously accumulated, and the closer to the end of the rolling cycle, the more serious the wear, and the smaller the roughness of the plate surface. Therefore, in combination with the decrease law of the roughness of the plate surface, the roughness change law in the rolling cycle is summarized, and the roughness of the plate surface decreases by 0.1μm per rolling cycle of 1350t.

[0013] Further, the effective utilization rate of the roughness of the working roll surface imprinted on the plate surface of the steel plate is 50%-60% in the rolling process.

[0014] On the basis of the rolling cycle-Ra contrast graph, in combination with the ABAQUS finite element analysis of the rolling process, it can be known that the actual use part of the working roll surface is the wave crest of the roughness of the working roll surface in the rolling process, and the metal is more difficult to deform in the wave trough in the deformation flow process. According to the analysis results and the actual roll surface measurement, the effective utilization rate of the roughness of the working roll surface imprinted on the plate surface of the steel plate is 50%-60% in the rolling process.

[0015] The roughness of the working roll surface directly affects the roughness of the plate surface. Since the galvanizing process exists in the galvanizing unit, the roughness of the plate surface is basically the same before entering the skin pass mill, and after the skin pass rolling, the roughness of the working roll surface is imprinted on the surface of the strip steel under the action of the rolling force and the tension, and the surface of the strip steel obtains the roughness. Since the working roll surface directly contacts the surface of the strip steel, the roughness of the surface of the strip steel is affected by the roughness of the working roll surface, the greater the roughness of the working roll surface, the greater the roughness of the surface of the strip steel, and the roughness of the working roll is preferably Ra2.0 and Ra2.5.

[0016] Further, the wave peak use efficiency is 60% to 100%.

[0017] In combination with the wear condition of the working roll surface in actual work, the wave peak use efficiency is increased. Figure 2 As shown in the figure, the wave peak height before wear is the blue part (dark part), and the wave peak height after wear is reduced to the gray part (light part). The difference between the height reduction during the period is the range of the reduction of the roll surface roughness. Through the evaluation of the wear condition, the wave peak height after wear is 60% to 100% of the original wave peak height. Thus, the coefficient wave peak use efficiency is introduced.

[0018] Further, the steel grade coefficient k is corrected by taking the rolling force of the conventional steel grade 2000 kN as the benchmark and taking the ratio of the average rolling force of different steel grades to the rolling force of 2000 kN as the steel grade coefficient to compensate for the difference in the average rolling force.

[0019] In combination with the production product structure analysis of the galvanizing unit, the yield strength of the corresponding material of different steel grades is different. The higher the yield strength, the more difficult the deformation, and the greater the required rolling force. There is a difference in the average rolling force. Thus, the steel grade coefficient k is introduced to compensate for the difference in the average rolling force. The rolling force of the conventional steel grade 2000 kN is taken as the benchmark, and the ratio of the average rolling force of different steel grades to the rolling force of 2000 kN is taken as the steel grade coefficient to correct it to obtain the final formula:

[0020] Plate surface roughness = working roll surface roughness × impression ratio × wave peak use efficiency × k.

[0021] The influence of rolling force on plate surface roughness is nonlinear, and the curve presents a ladder distribution. In combination with the actual verification rule, the plate surface roughness can be controlled to a certain extent, the singleness that the roughness can only be arranged according to the rolling period is broken, the roughness control means is enriched, the roughness control achievement rate is improved, and the specific rule is as follows:

[0022] When the rolling force is between 1500 kN and 1700 kN, the rolling force increases, and the roughness does not change;

[0023] When the rolling force is between 1700 kN and 1900 kN, the rolling force increases, and the roughness increases. The influence range is 0.1;

[0024] When the rolling force is between 1900 kN and 2100 kN, the rolling force increases, and the roughness increases slightly (the amplitude is less than 0.1).

[0025] Further, the actual use rule of the above-mentioned roughness control method for one kind of galvanized product is:

[0026] In combination with the actual production process, the production time of the steel coil with special requirements for the plate roughness needs to be specially arranged, and generally as a high-grade automobile outer plate, the rolling cycle of such a steel coil needs to be calculated before production, and the work roll surface cannot be damaged or other damage to the roll surface before the arrival of the machine time, once the work roll is replaced, the rolling cycle needs to be recalculated, which is not conducive to the continuous production of high-grade automobile outer plate. Through the combination of work roll preparation and rolling cycle, the transition time required for outer plate production is shortened; before outer plate production, the work roll with Ra2.5 roughness is normally put on the machine, the work roll with Ra2.0 roughness is prepared, and the production is arranged according to the rolling cycle of the work roll with Ra2.5 roughness, and the work roll with Ra2.0 roughness is replaced during the transition period if the roll surface is abnormal, which saves about 3000 tons of rolling cycle, achieves the goal of rapid transition and rapid production, and avoids the phenomenon of missing the outer plate production cycle due to roughness transition.

[0027] The control measures of the galvanizing unit for three roughnesses are as follows:

[0028] The product with Ra=1.25μm is arranged in 880t rolling cycle production;

[0029] The product with Ra=1.20μm is arranged in 1400t rolling cycle production;

[0030] The product with Ra=1.10μm is arranged in 1600t rolling cycle production.

[0031] Compared with the prior art, the beneficial effects of the present application are as follows:

[0032] In order to improve the control precision of the roughness of the galvanized product, through the research on the roughness change in the rolling cycle of the galvanized product, the influence of the finishing mill rolling force and the rolling cycle on the plate roughness of the galvanized product is determined, the production time of the galvanized product in one rolling cycle is controlled, and the target value of the roughness is obtained.

[0033] The specific production time of the product in one rolling cycle can be obtained through the rolling cycle-Ra contrast curve, which is convenient for planning the production scheme in advance, and makes the roughness controllable production, improves the roughness control precision, and ensures that the product surface roughness meets the standard. The influence of the rolling force on the plate roughness is nonlinear, and the curve presents a ladder distribution, which can control the plate roughness to a certain extent in combination with the actual verification rule, get rid of the singleness that the roughness can only be arranged according to the rolling cycle, enrich the roughness control means, and improve the roughness control achievement rate.

[0034] Through analysis and induction of the test data, a general roughness change rule formula is obtained, so that roughness control is changed from empirical data to a calculable, predictable and controllable control method, and the organization, planning and accuracy of product roughness control are improved, thereby ensuring product delivery. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a rolling cycle-Ra contrast graph;

[0036] Figure 2 is a peak wear before and after contrast graph, wherein the peak height before wear is a blue part (dark part), and the peak height after wear is reduced to a gray part (light part);

[0037] Figure 3 is a work roll size graph. DETAILED DESCRIPTION

[0038] The application will be further described below in combination with specific examples, but the application is not limited in any way by the examples. For the sake of brevity, the raw materials in the following examples are all commercially available products unless otherwise specified, and the processes used are all conventional processes unless otherwise specified.

[0039] EXAMPLE

[0040] A roughness control method of a galvanized product, comprising the following steps:

[0041] ① Formulation of rolling cycle

[0042] The work roll with Ra2.5 roughness is commonly used in the galvanizing unit, which is used in the daily production process. The rolling cycle and plate surface roughness contrast table is formulated according to the roughness change rule of the plate surface in the same rolling cycle, as shown in Table 1.

[0043] Table 1 Rolling cycle and plate surface roughness contrast table

[0044]

[0045] The work roll with Ra2.0 roughness is a special spare roll of the galvanizing unit. The work roll with Ra2.0 roughness is mainly used for high-grade IF steel FC outer plate. The rolling cycle and plate surface roughness contrast table is formulated according to the roughness change rule of the plate surface in the same rolling cycle, as shown in Table 2.

[0046] Table 2 Rolling cycle and plate surface roughness contrast table

[0047] 0-150t 150-1150t 1150-2150t 2150-3150t 3150-4150t IF 1.25-1.2 μm 1.2-1.1 μm 1.1-1.0 μm 1.0-0.9 μm 0.9-0.8 μm

[0048] ② Formulation of work roll preparation scheme

[0049] In the daily production process, the roughness of ordinary household appliance plate is required to be 0.8-1.6μm, and the roughness of automobile plate is required to be 0.8-1.2μm, but there are also special requirements for the roughness of high-end users, such as 0.8-1.0μm for pan-Asia, 0.9-1.4μm for Mercedes-Benz, and the order specifications are different, and the total order quantity is mainly concentrated in small batch orders or test materials. When preparing these products for production, due to the planning arrangement, the corresponding rolling period is missed due to the transition of the target roll specification, so as to miss the production period. In order to avoid such situations, the work roll standby roll link is adjusted to shorten the preparation period.

[0050] The roughness of the plate surface is required to be 0.8-1.2μm: the roughness of the standby Ra2.0 work roll is prepared;

[0051] The roughness of the plate surface is required to be 1.0-1.4μm: the roughness of the standby Ra2.5 work roll is prepared.

[0052] ③ Rolling force parameter setting

[0053] There should be a roughness platform in the corresponding relationship between rolling force and plate surface roughness. The change of rolling force in this platform almost does not affect the roughness. The platform is between 1500-1700kN of rolling force. However, low rolling force is not conducive to obtaining a good surface in the finishing machine. Therefore, the upper limit position of the rolling force for changing the roughness is better than the lower limit position. Thus, the rolling force parameters for producing high-grade FC outer plate are set.

[0054] The rolling force for producing high-grade FC outer plate is not less than 2100kN.

[0055] Before production, the use cycle of the finishing work roll and the roughness of the finishing work roll surface are obtained. The roughness change trend in the rolling period and the theoretical value of the plate surface roughness in the rolling period are calculated according to the plate surface roughness formula. The production time of the target product is determined according to the plate surface roughness and rolling period comparison chart. After the target product is put on the machine, the surface roughness of the product is measured. At the same time, the finishing rolling force is gradually increased to obtain the influence value of the rolling force on the plate surface roughness. Finally, the specific production time of the subsequent product is determined according to the rolling period and rolling force related data.

[0056] For any person skilled in the art, many possible changes and modifications, or modifications to equivalent embodiments, can be made to the technical solutions of the present application without departing from the scope of the technical solutions of the present application, by utilizing the technical content disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A method of controlling the roughness of a galvanized product, characterized in that, The plate surface roughness of the galvanized product is formed by the combined action of the work roll roughness, zinc layer, rolling force and steel grade parameters, and the corresponding relationship between the plate surface roughness and the work roll surface roughness is: Plate surface roughness = work roll surface roughness × transfer rate × wave peak utilization efficiency × k; wherein, The transfer rate is 50% to 60%; The wave peak utilization efficiency is 60% to 100%; K is the steel grade coefficient; An ideal curve of the plate surface roughness change is formulated to obtain a rolling cycle-Ra contrast curve graph in a rolling cycle; In the same rolling cycle, the plate surface roughness gradually decreases; in the same rolling cycle, taking 150t as a dividing point, the roughness sharply decreases in the rolling cycle of 0-150t; the roughness linearly and uniformly decreases in the rolling cycle of 150-6000t, and the plate surface roughness decreases by 0.1μm every 1350t of rolling; The effective utilization rate of the work roll surface roughness transferred to the steel plate surface is 50% to 60%; The work roll roughness is Ra2.0μm and Ra2.5μm; The steel grade coefficient k is corrected by taking the average rolling force of different steel grades as a ratio of the 2000kN rolling force as a benchmark.

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