Elimination of Printing Defects on Hot-dip Galvanized Steel Coil

Abstract : When the hot-dip galvanizing unit produces thin-gauge steel strips with a thickness less than 0.4 mm , when the expansion shaft of the coiler is in the expanded state to coil the steel strip , there will be more scroll marks on the inner ring of the steel coil. Missing coating defects occur in the steel coil during the coating process of the color coating unit . Eliminate or reduce reel marks by adding elastic rubber sleeves to hot-dip galvanized coiler shafts and color-coated uncoiler shafts.

Keywords : Continuous hot-dip galvanizing unit ; scroll printing ; elastic rubber sleeve
 

a hot-dip galvanizing and color-coating unit in a factory is producing thin strip steel with a thickness of less than 0.4 mm , when the expansion shaft of the hot-dip galvanizing coiler or color-coating uncoiler is in the expanded state to coil the steel strip , the inner ring of the steel coil More reel marks are produced , and what's more, the steel coil core is raised at the gap between the four wedge blocks of the uncoiler and the coiler in the radial direction . On the one hand, the normal production rhythm of the hot-dip galvanizing and color coating units is restricted due to the influence of the unloading of the steel coil ; and the protruding coil core causes the entire steel coil to be judged as a waste product . On the other hand, after the convex part of the winding core is uncoiled , the plate surface is deformed , resulting in defects such as missing coating and edge waves in the coating process produced by the color coating unit in the next process . Only this defect affects the machine composition rate to 0.245% .
1 Causes of Reel Printing Defects
The reel of the hot-dip galvanized coiler is composed of 4 fan-shaped blocks , exist
When the coiler is coiling the steel strip , the 4 fan-shaped blocks are in the state of expanding , Its diameter is 508 mm, and its circumference is 508 Xn = 1 595.929 mm . There is a gap of ( 1595.929 - 1 448.274) -4=36.91 mm between each fan-shaped block ( as shown in Figure 2) .

Figure 2 Reel Expanded State
Fig- 2 Expanded mandrel

At this time , the gap between the fan block and the two radii of the reel form a triangle ( as shown in Figure 3) . The central angle Z AOB of the triangle is a then a=2 aics n ( 36 954 ) =8.333 . , arc length
Also = disk X2 n X 254 = 36.947 mm, chord length AB = 36.914 mm .

After the strip steel is coiled on the reel , the inner ring of the strip steel in the gap part is not supported by the arc surface of the reel , and under the action of tension , the strip steel changes from the arc state to the chord length state. Therefore, the length of the chord-shaped strip steel coiled on the reel is shorter than that of the arc-shaped strip , and the length difference is AB— AB = 36.947 —36.914 =0.033 mm . When the steel coil is unloaded , the strip steel between the layers in the reel gap part of the steel coil cannot be in a circular arc shape . Due to the disappearance of the coiling tension , the strip steel in this part will bulge toward the core of the coil , forming a reel mark ( also called heart shape) Volume , tread volume ) defect , especially the defect of thin strip steel is more serious .
2 Measures to eliminate scroll marks
In order to eliminate the reel marks of strip steel , improve the yield , and ensure the normal production rhythm of the hot-dip galvanizing line to produce thin-gauge strip steel . Specially add an elastic rubber sleeve to the reel of the hot-dip galvanized coiler and the reel of the color-coated uncoiler . When the reel is in the retracted state , put the elastic rubber sleeve on the reel . The sleeve is expanded , and the strip steel is coiled on the rubber sleeve , and the strip steel forms a whole circle along the wall of the rubber sleeve . To achieve the purpose of eliminating scroll marks . The elastic rubber sleeves for hot-dip galvanized coiling and color-coating uncoilers are plastic elastic cylinders made of IPN polyurea-fabric composites and IPN polyurea elastomers . The inner diameter of the steel coil is usually ① 508 mm or ① 610 mm, so the inner diameter of the steel coil with the elastic rubber sleeve is designed to be ① 610 mm .
3 Technical solutions for rubber sleeve design
31 Elastic rubber sleeve for coiling on hot-dip galvanized coiler
The original position size of the hot-dip galvanized coiler reel is ① 461X 1550 mm, and the working position size is ① 508 X 1 550 mm . In order to facilitate the installation and disassembly of the rubber sleeve , the inner diameter of the elastic rubber sleeve is designed to be ① 466 mm. At the same time, in order to ensure that the diameter of the inner ring of the steel coil at the working position is 610 mm, it is considered that the reel of the coiler expands from the original position to the working position. 508—461=47 mm . According to experience , when the reel expands 47 mm , the thickness of the elastic rubber sleeve is reduced by about 3 mm , and the outer diameter of the elastic rubber sleeve should be designed to be 613 mm . Then the wall thickness of the rubber sleeve d = ( 613—508) -2=52.5 mm . This can ensure that the outer diameter of the rubber sleeve at the working position of the reel of the coiler ( that is, the diameter of the inner ring of the steel coil ) is 610 mm . Therefore, the outer diameter of the elastic rubber sleeve D = 466 + 52.5X2 = 571 mm .
To sum up , the design dimensions of the elastic rubber sleeve used in the hot-dip galvanizing coiler : ① 466X ① 571X1 550 mm ( as shown in Figure 4) .

32 prepainted decoiler
The original bit size of the uncoiler reel of the color coating unit is ① 481X
1 550 mm, the size of the working station is ① 508X1 550 mm . In order to facilitate the installation and disassembly of the rubber sleeve, the inner diameter of the elastic rubber sleeve is designed as ① 485 mm. At the same time, in order to ensure that the inner diameter of the hot-dip galvanized steel coil is 610 mm when the working position is tightened and the reel of the uncoiler is from the original position to the The stroke of the working position is 508-481=27 mm. According to experience , when the reel is opened by 27 mm , the thickness of the elastic rubber sleeve is reduced by about 2 mrm . Tighten the hot-dip galvanized steel coil , and set a tension of 6 mm for the rubber sleeve of the uncoiler . Therefore, the outer diameter of the rubber sleeve at the working position of the reel of the uncoiler ( that is, the diameter of the inner ring of the steel coil ) is about 610 + 6X2 = 622 mm . Then the wall thickness of the rubber sleeve of the uncoiler d = (622 + 2-508) —2=58 mm , so the outer diameter of the elastic rubber sleeve for the uncoiler is D = 481 + 58X2 = 597 mm
Therefore , the size of the elastic rubber sleeve used for color coating uncoiling : ① 485X597X1550 mm ( as shown in Figure 5 ) .

4 Epilogue
Through the use of the elastic rubber sleeve , the hot-dip galvanized steel coil printing defect directly supplied to the color coating unit as raw material is eliminated . The physical picture is shown in Figure 6 . It reduces the defects such as missed coating , poor plate shape and edge waves caused by the printing defects of the raw material reel in the color coating unit . The finished product rate of the color coating unit is improved .
After communicating with the customer , the thin-gauge hot-dip galvanized steel coil is supplied with an inner diameter of ① 610 mm , and an elastic rubber sleeve can be installed on the reel of the coiler to avoid the thin-gauge hot-dip galvanized steel coil. Reel printing defects can meet user needs . The supply capacity of thin-gauge hot-dip galvanized steel coils has been improved .
This kind of elastic rubber sleeve can be used in continuous hot-dip galvanizing line and connected
It is used together with continuous color coated steel plate units.

( Continued from page 47 )
Since it was put into production , The low-carbon steel production of No. 3 Steelmaking has increased by nearly 80 % compared with the past . By improving the level of operation , strengthen management , No. 3 Steelmaking has overcome the problem of slag splashing to protect the converter when smelting low carbon steel . Guaranteed the quality of slag splashing furnace protection , The furnace life of the converter has not been affected by the increase in smelting low-carbon steel .
1) The corrosion of the slag splash layer in the middle and late stages of converter smelting is characterized by chemical erosion and high temperature melting . By improving the smelting process , implementing measures such as adding magnesium balls in stages , adjusting the loading system , and appropriately reducing the position of the carbon pulling gun , the key to ensuring the corrosion resistance of the slag splash layer is to adjust the final slag composition when smelting low-carbon steel .
2) Reasonably lowering the tapping temperature and developing and using compound slag-reducing agents to reduce bubbles in the furnace are also effective measures to improve the life of the slag-splashing layer . References :

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