A method of preventing surface defects in 430 stainless steel

Abstract

The present application belongs to the technical field of stainless steel surface process, and particularly relates to a 430 stainless steel surface defect prevention method, which comprises the following contents: (1) adjusting the pressure of the side guide head according to the thickness of the steel strip; (2) increasing the program to make the coiling tension identify the coiling weight; (3) improving the rigidity precision of the pinch roll; (4) adding a vertical wheel on the side of the side guide work and the transmission side; (5) adopting the hot roll process for pretreatment after the new coiling roll is put on the machine; (6) the welding rod cannot be made of 1Cr13 material, and the W-shaped staggered welding process is adopted between the welding beads; (7) the head CT precision in the coiling process is accurately controlled by adjusting the heat transfer coefficient of each cooling section and the target temperature of the cooling section; (8) the roll gap display measured deviation of the coiling roll is controlled; (9) the blocked water nozzle is found in time, and the water nozzle with small flow after artificial dredging is replaced; (10) the lining plate adopts the powder wear-resistant lining plate. The method reduces the surface defect problems of the pinch roll scratch and the coiling roll roll mark, and improves the product qualification rate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of stainless steel surface process, and particularly relates to a 430 stainless steel surface defect prevention method. BACKGROUND

[0002] Among the 430 surface defects, the defects caused by the coiler account for more than 70%, mainly including the pinch roll scratch and the coiler print. The domestic 430 manufacturers actively improve the 430 surface quality, such as controlling the side blowing water flow and pressure of the pinch roll before coiling, improving the coiler precision, and increasing the standby pressure tank. Although these improvements play a positive role in improving the 430 surface quality, they are still not enough for the heat fatigue resistance and other characteristics of the 430 steel, and the surface defect problem still exists. The main reasons for the pinch roll scratch are as follows:

[0003] (1) At present, the domestic coiling side guide uses a lining plate side guide, the head pressure of the coiling side guide is small, after the strip is bitten by the pinch roll, the strip cannot be quickly centered, the strip is seriously deviated from the center of the winding drum after winding several turns at the head of the winding drum, and after the side guide is completely closed in place, friction occurs between the strip and the side guide, and the lining plate is prone to point contact. One side of the side guide is stressed, sparks are generated, the sparks are brought into the surface of the pinch roll to form a scratch;

[0004] (2) The winding drum speed fluctuates greatly with the change of the coiling weight, under the same tension, the winding drum speed is different after the strip is thrown by the finishing mill, and the change of the winding drum speed causes the scratch.

[0005] The main reasons for the coiler print are as follows: (1) the regular weld bead caused by the adhesion on the surface of the coiler or the uneven hardness of the coiler surface is printed on the surface of the steel plate; (2) the coiler precision is not up to standard, especially the horizontal precision of the coiler is not up to standard, and the coiler print defect is generated at 6-10 turns at the head of the steel coil; (3) the coiler surface is unevenly cooled, and the high-temperature strip causes the coiler surface to be annealed to cause adhesion. SUMMARY

[0006] The purpose of the application is to provide a 430 stainless steel surface defect prevention method to solve the problems of the scratch and the coiler print on the surface of the 430 stainless steel.

[0007] To achieve the above purpose, the application adopts the following technical scheme:

[0008] A 430 stainless steel surface defect prevention method comprises the following contents:

[0009] (1) According to the thickness of the steel strip, adjust the pressure of the side guide head; the thicker the steel strip, the greater the pressure of the side guide head, the pressure of the side guide head is the set pressure of the side guide body * coefficient, the greater the pressure of the side guide head, the faster the action speed of the side guide head, in order to quickly clamp the head of the steel strip, without appearing tower shape, let the steel strip roll in the center position of the winding drum, the steel strip enters the side guide, there is a 30mm gap between the front steel strip and the side guide on each side, after the steel strip is bitten into the pinch roll, the side guide is quickly closed, only the side guide and the steel strip have a certain contact force, the side guide can reach or find the set pressure, the set pressure on the control system is the parameter sent by the process control machine, the pressure sensor will collect the pressure after the side guide contacts with the steel strip in the field, the closer the actual pressure collected in the field to the set pressure on the control system, the better;

[0010] (2) Increase the program to make the winding tension identify the winding weight, and stabilize the winding drum speed; different winding weights require different winding tensions, through the program, the winding weight is divided into three grades, different winding weights correspond to different winding tensions, and the winding drum speed is stabilized;

[0011] (3) Improve the rigidity accuracy of the pinch roll, the specific content is as follows:

[0012] <1> Before leaving the factory, detect the height on the platform every time the pin hole sleeve is replaced;

[0013] <2> Increase the gasket under the bearing seat of the pinch roll to adjust the rigidity of the pinch roll, and the pressure can be reduced by about 16kn for every 1mm of gasket;

[0014] <3> Adjust the eccentric pin according to the roll gap deviation before zero adjustment, the roll gap deviation of the working side and the transmission side 0.2;

[0015] (4) The side guide working side and the transmission side are both provided with a vertical wheel, which changes the sliding friction between the steel strip and the side guide into rolling friction, reducing the spark generation between the side guide and the steel strip;

[0016] (5) After the new coiling aid roll is put into operation, the hot roll process is used for pretreatment, 780 degrees or above high temperature stainless steel is not coiled within 48 hours, and specifications with strength T500 or above are not coiled within 48 hours;

[0017] (6) Improve the surface overlaying process of the coiling aid roll, 1Cr13 material welding rod cannot be used, W-shaped staggered welding process is adopted between welding beads, and the hardness of the surface of the coiling aid roll is improved;

[0018] (7) Precisely control the head CT accuracy in the winding process by adjusting the heat conduction coefficient of each cooling section and the target temperature of the cooling section; the heat conduction coefficient is adjusted from 0.9 to 1.1, the temperature sensitive system is adjusted from 0.3 to 0.16, and the target temperature and the head temperature are adjusted with a difference of 10 degrees;

[0019] (8) Control the display deviation of the roll gap of the winding roller, select the automatic zero adjustment, then manually press and recheck, and then manually correct the roll gap control method again. This method can accurately control the deviation between the winding roller display and the actual measurement on site;

[0020] (9) Discover the blocked water nozzle in time, replace the water nozzle after manual dredging, and control the uniformity of the cooling water of the winding roller in the full width direction;

[0021] (10) The lining plate adopts a powder wear-resistant lining plate. The strip steel and the lining plate contact and produce friction. The lining plate is not bonded, and the wear presents as powder iron filings, which will not be pressed on the surface of the steel plate.

[0022] Preferably, in the (1), when H≤2.0 mm, the side guide head pressure is 1.23*set pressure, when 2.0<H≤3.4, the side guide head pressure is 1.2*set pressure, when 3.4<H≤4.0, the side guide head pressure is 1.15*set pressure, when 4.0<H≤5.0, the side guide head pressure is 1.16*set pressure, when 5.0<H≤6.5, the side guide head pressure is 1.1*set pressure, when 6.5<H≤8, the side guide head pressure is 0.9*set pressure, and when 8.0<H, the side guide head pressure is 1*set pressure, wherein H is the thickness of the steel strip, and the set pressure unit is kn.

[0023] Preferably, in the (2), the winding tension picture precision alarm function is also included. The program design alarm is divided into four sections. When the winding speed minus the lower pinch roll speed is less than 0, the picture produces a yellow tension alarm. When the winding speed minus the lower pinch roll speed is in the range of 0-0.8 m / s, the picture displays green to indicate the normal range. When the winding speed minus the lower pinch roll speed is in the range of 0.8-1.2 m / s, the picture displays pink to prompt the operator to intervene to reduce the winding tension. When the winding speed minus the lower pinch roll speed is greater than 1.2 m / s, the picture displays red to prompt immediate intervention, and failure to intervene will produce surface scratch defects.

[0024] Preferably, in the (2), the production scheduling structure is also optimized. The production scheduling is concentrated for similar weights. The coil weight is divided into three grades, i.e., below 18 tons, 18-23 tons, and above 23 tons. The production scheduling is concentrated for the same weight in the same grade to avoid the need for the system to frequently switch the winding tension due to different weights, which affects the work efficiency and increases the energy consumption.

[0025] Preferably, the (4) working side and transmission side vertical wheels are 5, the radial force of the vertical wheel Fr=50000N, the axial force Fa=10000N, the circumferential force Ft=50000N, the journal diameter d1=55mm, the rotating speed n=1000r / min, the design life Lh'=2000h, the action point distance L=200mm, the distance L1 between Fr and the bearing 1=100mm, the distance La between Fr and the shaft center line=100mm, the temperature coefficient ft=1, the lubrication mode Grease=oil lubrication, the bearing type is a tapered roller bearing, the bearing inner diameter d=55mm, and the basic rated static load Co=270000N.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] (1) The coiling weight is identified by the coiling tension, the reel speed is unchanged after the finishing and the steel is thrown, and the scar is avoided;

[0028] (2) The pressure of the side guide head part is adjusted by the steel strip thickness, the strip steel is quickly centered, the sliding friction between the strip steel and the side guide is changed into rolling friction by the vertical wheel, the spark generation between the side guide and the strip steel is reduced, and the scar on the surface of the pinch roll is avoided;

[0029] (3) The vertical wheels are additionally arranged on the working side and the transmission side, the rolling friction is formed between the strip steel and the side guide, and almost no spark is generated;

[0030] (4) The high-temperature steel of more than 780 degrees is not coiled within 48 hours, the surface annealing is prevented to reduce the hardness, the adhesive is not generated, and the pinch roll imprint defect is avoided; the uniformity of the cooling water of the pinch roll in the full width direction is controlled, and the annealing of the pinch roll surface caused by the high-temperature strip steel is prevented;

[0031] (5) The hardness of the surface of the pinch roll is improved by replacing the welding rod material and optimizing the welding process, and the regular welding trace caused by the uneven hardness is avoided to be printed on the surface of the steel plate;

[0032] (6) The CT stability of the thick specification head part has a great influence on the coiling shape appearance and the pinch roll imprint, the head part CT precision in the coiling process is accurately controlled by adjusting the heat conduction coefficient of each cooling section and the target temperature of the cooling section, the strip steel is prevented from slipping with the pinch roll in the head part coiling process, and the roll imprint is reduced;

[0033] (7) The actual measurement deviation of the pinch roll gap is controlled, the slipping caused by the large pinch roll gap is avoided, and the pinch roll is prevented from being impacted and adhered due to the small pinch roll gap. DETAILED DESCRIPTION

[0034] The technical scheme of the application is described below in combination with the embodiments.

[0035] A method for preventing surface defects of 430 stainless steel, comprising the following contents:

[0036] (1) According to the thickness of the steel strip, adjust the pressure of the side guide head; the thicker the steel strip, the greater the pressure of the side guide head, the pressure of the side guide head is the set pressure of the side guide body * coefficient, the greater the pressure of the side guide head, the faster the action speed of the side guide head, in order to quickly clamp the head of the steel strip, without appearing tower shape, and the steel strip is wound at the center position of the winding drum, there is a 30mm gap on each side between the front steel strip and the side guide when the steel strip enters the side guide, after the steel strip is bitten into the pinch roll, the side guide is quickly closed, only the side guide and the steel strip have a certain contact force, the side guide can reach or find the set pressure, the actual pressure collected by the pressure sensor after the side guide contacts with the steel strip on the control system is as close as possible to the set pressure, 3.4<H≤4.0, the pressure of the side guide head is 1.15*set pressure, and H is the thickness of the steel strip;

[0037] (2) Increase the program to make the winding tension identify the winding weight, and stabilize the winding drum speed; different winding weights require different winding tensions, the winding weight is divided into three grades through the program, different winding weights correspond to different winding tensions, and the winding drum speed is stabilized; the winding tension picture has accurate alarm function, the program design alarm is divided into four sections, when the winding drum speed minus the lower pinch roll speed is less than 0, the picture generates yellow tension alarm, when the winding drum speed minus the lower pinch roll speed is in the range of 0-0.8m / s, the picture displays green color to indicate normal range, when the winding drum speed minus the lower pinch roll speed is in the range of 0.8-1.2m / s, the picture displays pink color to prompt the operator to intervene to reduce the winding tension, and when the winding drum speed minus the lower pinch roll speed is greater than 1.2m / s, the picture displays red color to prompt that immediate intervention is necessary, and no intervention will produce surface scarring defects; optimize the production scheduling structure, concentrate the production scheduling of the steel strips with similar weights, divide the winding weight into three grades, i.e. below 18 tons, 18-23 tons and above 23 tons, concentrate the production scheduling of the steel strips with the same weight, and the winding tension settings at different stages are shown in Table 1.

[0038] Table 1 Winding tension settings at different stages

[0039]

[0040] (3) Improve the rigidity accuracy of the pinch roll, and the specific contents are as follows:

[0041] <1> Before leaving the factory, detect the height on the platform every time the pin hole sleeve is replaced;

[0042] <2> Increase the gasket under the bearing seat of the pinch roll to adjust the rigidity of the pinch roll, and the pressure can be reduced by about 16kn every time the gasket is increased by 1mm;

[0043] <3>According to the zero adjustment eccentric pin before the zero roll gap deviation, the work side and the transmission side of the roll gap deviation 0.2;

[0044] (4) The side guide work side and transmission side are additionally provided with five vertical wheels, the radial force Fr of the vertical wheel is 50000 N, the axial force Fa is 10000 N, the circumferential force Ft is 50000 N, the shaft neck diameter d1 is 55 mm, the rotating speed n is 1000 r / min, the design life Lh' is 2000 h, the distance L of the action point is 200 mm, the distance L1 of Fr from the bearing 1 is 100 mm, the distance La of Fr from the shaft center line is 100 mm, the temperature coefficient ft is 1, the lubrication mode is grease, the bearing type is a conical roller bearing, the bearing inner diameter d is 55 mm, and the basic rated static load Co is 270000 N. The sliding friction between the strip steel and the side guide is changed into rolling friction, and the spark generation between the side guide and the strip steel is reduced.

[0045] (5) The new coiling aid roller is preprocessed by adopting the ironing roller process after being put into use. The 780-degree high-temperature stainless steel is not coiled within 48 hours, and the specifications with the strength T500 are not coiled within 48 hours.

[0046] (6) The surface hardfacing process of the coiling aid roller is improved. The surface hardness of the welding rod made of 3Cr13Mn material can reach HRC60. The W-shaped staggered welding process is adopted between the welding lines to improve the hardness of the surface of the coiling aid roller.

[0047] (7) The head CT precision in the coiling process is accurately controlled by adjusting the heat conduction coefficient of each cooling section and the target temperature of the cooling section. The heat conduction coefficient is adjusted from 0.9 to 1.1, the temperature sensitive system is adjusted from 0.3 to 0.16, and the target temperature and the head temperature are adjusted with a difference of 10 degrees.

[0048] (8) The display deviation of the coiling aid roller gap is controlled. The automatic zero adjustment is selected, and then the manual pressing and secondary inspection are performed. Then, the control method of manually correcting the roller gap again is adopted. This method can accurately control the deviation between the display and the actual measurement of the coiling aid roller.

[0049] (9) The blocked water nozzle is found in time. The water nozzle is replaced after being manually dredged when the flow is small. The uniformity of the coiling aid roller cooling water in the full width direction is controlled.

[0050] (10) The lining plate adopts the powder wear-resistant lining plate. The strip steel and the lining plate contact to generate friction. The lining plate is not bonded, and the wear presents the powder-shaped iron filings, which will not be pressed on the surface of the steel plate.

[0051] The maximum deviation between the display and the actual measurement of the coiling aid roller before using the method is 3.0 mm, and the deviation is reduced to 0.6 mm after using the method. The vertical wheels are additionally provided on the work side and the transmission side. The rolling friction is formed between the strip steel and the side guide, and almost no spark is observed on site.

[0052] After the method, the surface defects of 430 coiled plate caused by the pinch roll and the lap roll of the coiler are reduced from 1.79% to 1.12%, the qualified rate is improved, the cost is reduced, and the unqualified proportion is far lower than the average unqualified proportion of 1.55% of the same industry.

Claims

1. A method for preventing surface defects in 430 stainless steel, characterized in that, It includes the following contents:

1. Adjust the pressure of the side guide head according to the strip thickness. The thicker the strip, the greater the pressure required at the side guide head. The pressure at the side guide head is the set pressure of the side guide body * coefficient. The greater the pressure at the side guide head, the faster the action speed of the side guide head. To quickly clamp the strip head and prevent tower shape, and make the strip coil at the center position of the coiler drum. There is a 30mm gap on each side between the strip and the side guide before the strip enters the side guide. After the strip is bitten into the pinch roll, the side guide closes quickly. Only when there is a certain contact force between the side guide and the strip can the side guide reach or find the set pressure. The set pressure on the control system is the parameter sent by the process control computer. After the on-site side guide contacts the strip, the pressure sensor will collect the pressure. The closer the actual pressure collected on-site to the set pressure on the control system, the better. When H ≤ 2.0mm, the pressure at the side guide head is 1.23 * set pressure; when 2.0 < H ≤ 3.4, the pressure at the side guide head is 1.2 * set pressure; when 3.4 < H ≤ 4.0, the pressure at the side guide head is 1.15 * set pressure; when 4.0 < H ≤ 5.0, the pressure at the side guide head is 1.16 * set pressure; when 5.0 < H ≤ 6.5, the pressure at the side guide head is 1.1 * set pressure; when 6.5 < H ≤ 8, the pressure at the side guide head is 0.9 * set pressure; when 8.0 < H, the pressure at the side guide head is 1 * set pressure, where H is the strip thickness and the unit of the set pressure is kn; 2. Add a program to enable the coiling tension to identify the coiling weight and stabilize the coiler drum speed. Different coiling weights require different coiling tensions. Divide the coiling weight into three grades through the program, and different coiling weights correspond to different coiling tensions to stabilize the coiler drum speed; 3. Improve the stiffness accuracy of the pinch roll. The specific contents are as follows: <1> Before leaving the factory, each time the pinhole sleeve is replaced, the elevation detection is carried out on the upper platform; <3> Adjust the eccentric pin according to the roller gap deviation before zeroing, and adjust the roller gap deviation on both the working side and the transmission side. 0.2; <2> Add gaskets under the pinch roll bearing seat to adjust the stiffness of the pinch roll. For every 1mm increase in the gasket, the pressure decreases by 16kn; 4. Vertical wheels are added on both the working side and the driving side of the side guide to change the sliding friction between the strip and the side guide into rolling friction and reduce the generation of sparks between the side guide and the strip; 5. After the new coiling helper rolls are put into operation, they are pretreated with the hot roll process. High-temperature stainless steel above 780 degrees is not coiled within 48 hours, and specifications with a strength above T500 are not coiled within 48 hours; 6. Improve the surface surfacing process of the coiling helper rolls. Use 3Cr13Mn material electrodes and adopt the W-shaped staggered welding process between weld beads to improve the surface hardness of the coiling helper rolls; 7. Accurately control the CT accuracy of the head during coiling by adjusting the heat transfer coefficient of each cooling section and the target temperature of the cooling section. The heat transfer coefficient is adjusted from 0.9 to 1.1, the temperature-sensitive system is adjusted from 0.3 to 0.16, and the adjustment is made when the target temperature and the head temperature differ by 10 degrees; 8. Control the measured deviation of the coiling helper roll gap display. Select the control method of automatic zero adjustment followed by manual pressing and secondary inspection, and then manual correction of the roll gap again. This method can accurately control the deviation between the coiling helper roll display and the on-site measurement; (9) Promptly identify blocked water nozzles, replace water nozzles with low flow rates after manual unblocking, and control the uniformity of cooling water in the entire width direction of the auxiliary roller. (10) The liner is made of powder wear-resistant liner. The strip steel comes into contact with the liner and generates friction. The liner is not bonded. The wear is manifested as powdery iron filings, which will not be pressed on the surface of the steel plate.

2. The method for preventing surface defects in 430 stainless steel according to claim 1, characterized in that, The (2) also includes a precise alarm function for winding tension. The program is designed to have four alarm segments. When the winding speed minus the lower pinch roller speed is less than 0, a yellow tension alarm is generated on the screen. When the winding speed minus the lower pinch roller speed is within the range of 0-0.8 m / s, the screen displays green to indicate the normal range. When the drum speed minus the lower pinch roll speed is within the range of 0.8-1.2 m / s, the screen displays a pink indicator to prompt the operator to intervene and reduce the drum tension; when the drum speed minus the lower pinch roll speed is greater than 1.2 m / s, the screen displays a red indicator to prompt immediate intervention, otherwise surface scratch defects will occur.

3. The method for preventing surface defects in 430 stainless steel according to claim 2, characterized in that, The (2) also includes optimizing the production scheduling structure, grouping production of similar weights together, dividing the roll weight into three levels: below 18 tons, 18-23 tons, and above 23 tons. Production of the same weight level will be grouped together to avoid frequent switching of the required winding tension due to different weights, which would affect work efficiency and increase energy consumption.

4. The method for preventing surface defects in 430 stainless steel according to claim 3, characterized in that, In (4), there are 5 vertical rollers on both the working side and the transmission side. The radial force of the vertical roller is Fr=50000N, the axial force is Fa=10000N, the circumferential force is Ft=50000N, the journal diameter is d1=55mm, the rotational speed is n=1000r / min, the design life is Lh'=2000h, the distance between the action point is L=200mm, the distance between Fr and bearing 1 is L1=100mm, the distance between Fr and the axis is La=100mm, the temperature coefficient is ft=1, the lubrication method is Grease=oil lubrication, the bearing type is tapered roller bearing, the bearing inner diameter is d=55mm, and the basic rated static load is Co=270000N.

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