A preliminary study on the quality of steel drum curling seal
Text / Peng Xiaoxiang
The author has personally experienced and worked with barrel making for more than ten years to observe and study the phenomenon that the self-made and imported steel barrel sealing machine affects the crimp sealing of the steel barrel during sealing. In order to solve the sealing quality of steel barrels, the purpose is to provide some useful reference for the peers on the barrel-making front.
1. Overview of Steel Drum Seal
In addition to the quality of steel and welding, the sealing performance of the steel drum is mostly manifested in the curling, so the quality of the steel drum curling directly affects the quality of the steel drum.
In recent years, China's barrel industry has made great progress. In particular, the development of shipping packaging for dangerous goods at sea has been able to basically meet the requirements of maritime dangerous regulations. At the same time, the maritime dangerous regulations also put forward higher requirements for the steel drum seals in the barrel industry. For many years, in the process of shipping dangerous goods, the claims for the quality of the steel drum seal, that is, the leakage of the steel drum caused the loss of content, environmental pollution and the deterioration of the contents. The claims not only caused huge economic losses to the country, but also It has brought some bad international influences. Therefore, how to improve the quality of steel drums and improve the sealing performance of steel drums is of far-reaching significance for revitalizing the barrel industry and improving the economic and social benefits of enterprises.
Before China's reform and opening up, the demand for steel drum packaging was basically satisfied with the domestic packaging and transportation needs. Due to the low demand, and the domestic transportation is on inland rivers and land, the quality and sealing performance of steel drums are not high. Therefore, the barrel making work is often completed by a production plant with a small scale and a low production level. The equipment of these manufacturers is simple, and most of them are produced in manual and semi-mechanical workshops. At the same time, there is no professional manufacturer of container equipment. However, in the past three decades, the closure has become open, and the production of a large number of dangerous goods packaging and ocean workshops is far from satisfying and adapting to the development of today's country. Therefore, in accordance with the requirements of international dangerous regulations, based on the factory's actual improvement of existing production equipment and processes, the production of packaging products that comply with the international dangerous regulations and adapt to the transportation of dangerous goods at sea has become a top priority for China's barrel industry.
2. Ten problems in the barrel making process
1. The crimped upper bottom of the steel drum is made by folding the drum body and the bottom cover on the sealing disc of the sealing machine, and the crimping and sealing task is completed by the spinning of the sealing wheel. Therefore, when the sealing wheel is crimped, the geometry of the sealing wheel groove is fixed. During spinning, the sealing wheel is pushed into place, and the iron capacity in the sealing wheel groove is also fixed. The welding seam of the barrel is made of two layers of steel plates lap welded together. Although both layers of steel plates are ground, the welding layer is always thicker than one layer of iron. In addition, the mechanical properties of the welded seam are changed after being melted and cooled at high temperature. At the same time, there are 1 ~ 2mm steel plates with no fusion and thinning on both sides of the lap weld, which directly participates in the curling, so that the amount of curling material is thickened, and the sealing wheel rotates the excess material during sealing An iron tongue is formed outside the curled edge, which also causes an inadequate seal.
2. Because the size of the groove of the sealing wheel is designed according to the sequence of double or triple hemming steps, so too much material and too little material capacity are not allowed in the forming wheel groove because it enters the sealing groove If there is too much material, it will squeeze out the excess material in the spinning process to form an iron tongue outside the roll layer; too little material enters the sealing groove, because the rigidity of the material will rebound after spinning, forming a gap in the roll layer , Can't reach the curling layer. Practice has proved that the size of the barrel flanging and cover hook of the 200-liter steel drum is reasonable, and the tightness of the roll layer of the steel drum is reliable, otherwise it will cause peripheral leakage. At the same time, during the sealing process of the roll sealing wheel, due to the shearing and punching burrs around the cover hook and the barrel body hook, a large amount of heat is generated in the relative motion friction during spinning, which makes the surface of the wheel groove annealing reduces the work The surface hardness aggravates the wear of the surface of the forming groove. After a period of production, the size of the sealing wheel groove was damaged. The wear of the sealing wheel groove directly affects the tightness of the curling layer and the sealing performance of the steel drum.
3. Crimping and sealing is largely determined by the size of the sealing wheel, the rationality of the sealing wheel groove process, and the working step connection between the sealing wheels. Generally speaking, the double hemming is done by the secondary work into the sealing wheel. The dimensions between each wheel are different and related. The first round is the pre-roll of the second round, and the second round is the preparation of the third round. After the third round is completed, the hemming process is completed, and they cooperate with each other in an orderly manner. The author found that when some factories produce triple hemming, the bottom cover is separately pre-rolled, and it is used as a process. We believe that three sealing wheels on a sealing machine can complete the sealing task in three steps at a time, which is conducive to the coaxiality between the bottom cover and the barrel body during the sealing. Reduce the error of multiple installations, and facilitate the sealing after the steel drum is crimped.
4. Since most of the sealing machines of various production plants are self-made, even if they are purchased from outside, the technical parameters of the sealing machines are different due to the different manufacturers. In particular, the improper cooperation between the speed of the sealing wheel and the differential speed of the sealing disc will also affect the quality of the steel drum hemming. Taking the 200-liter steel drum sealing machine as an example, when the feed speed of the three-pass sealing wheel is 80mm / min, if the thickness of the steel plate material for the drum is 1.2mm, the linear speed of the sealing disc edge to the sealing wheel is 339m / min. If the thickness of the steel drum plate changes, the difference between the sealing wheel and the sealing disc generally changes accordingly. In general: under the condition that the work advance speed of the work progress wheel is the same as the thickness of the steel plate for the barrel, the linear speed of the circumference of the seal of the barrel body and the bottom cover after the hook is overlapped must be consistent; No change, the thickness of the barrel plate is different, the linear speed of the perimeter of the sealing body after the barrel body and the bottom cover are overlapped is different; the speed of the rotary wheel is slower as the thickness of the barrel plate is thicker.
5. In the hemming, in order to ensure the quality of the hemming, the sealing material needs to be coated on the inside of the lid hook portion of the hemming portion and the barrel hook portion. The sealing material is mainly composed of latex or rubber and fillers, resins, tackifiers, etc. There are two types of water splitting agents and solvents. Because it is impossible for the roll layer to be completely free of gaps when crimping, the sealant is used to fill this internal gap. The sealing material is very strict due to the fact that the filling material is different. Basically, it must have anti-corrosion, weather resistance, temperature resistance, flexibility, impact resistance and other properties. In the application method, to ensure that the coating is uniform. Currently, there are two application methods, one is manual brushing and the other is mechanical spraying. We think it is best to use mechanical spraying. The characteristic of spraying is that the coating is uniform, consistent and reasonable. Spraying is carried out in two steps, one is pre-coating on the cover hook, and the second is re-coating when crimping. In recent years, China has produced many new coating and sealing materials as needed. For example, the Bailu brand produced in Xiamen and the N-2 type sealant produced in Zhuzhou fill these gaps in China. As for some manufacturers still using bone gum brown sugar boiled filler and hot-melt polyvinyl alcohol as the filler for the seam sealing, it is undesirable, because they are easy to cause changes in sealing performance in anti-corrosion, impact resistance and temperature resistance.
6. Due to the different equipment of each barrel factory, the processing technology of semi-finished products before sealing assembly is also different, especially the effect of high temperature cooling on the mechanical properties of semi-finished products processing will of course affect the sealing performance of the assembly hemming. For example, the barrel for the chemical industry and the barrel for food use the internal coating process principle to pickle and passivate the surface of the barrel body cover, etc., and spray the thermosetting anti-corrosion non-toxic paint with high pressure and bake at 180 ～ 260 ℃ for 15 ～ It takes 20 minutes to cure and form a film, and the coating film is attached to the inner wall of the barrel to separate the contents from the barrel wall to achieve the purpose of anti-corrosion packaging. These semi-finished products will cause different or inconsistent mechanical properties of the barrel hook and the cover hook due to the different cooling conditions after baking. Therefore, pay attention to the accuracy of the temperature and the placement and storage after the furnace when coating and baking. Although there is no absolute guarantee that the processing mechanical properties of this batch of barrel parts are completely consistent, the reduction is generally the same. Because between barrels or parts of barrel parts, especially the part that directly participates in the curling during the assembly of the barrel and the local processing mechanical difference will affect the curling seal.
7. In the self-made sealing machine, the sealing wheel is divided into manual screw type, pneumatic type, eccentric mechanism automatic type and hydraulic automatic type. Among these working principles, we believe that the manual screw-type working speed is not well-controlled, and the labor intensity is large; although the pneumatic automatic type can meet the needs of general working, but the pressure in the pipeline is lost due to the long pipeline of the gas system Large, coupled with more gas-using equipment and more air flow divergence, the pressure in the sealing machine's infeed system is unstable, which affects the uniformity of the infeed speed of the sealing wheel. The eccentric automatic mechanism and the hydraulic automatic type make the feed speed of the feed wheel uniform and uniform, and the force is balanced. Therefore, it is recommended to use the eccentric mechanism or hydraulic automatic mechanism for the working method of the sealing wheel, which will help the sealing performance after crimping and sealing.
8. Although the production of steel barrel flat curling is allowed on GB325, we believe that double round curling and triple curling are better than double flat curling. The double round curling is not complicated in terms of its process. The pretreatment production process of the barrel parts is the same, but some improvements are made on the two sealing wheels, and the improvement is not difficult. The triple hemming is also to add a pre-rolling wheel on the sealing wheel, plus adjust the transition size between the other two sealing wheels reasonably, and at the same time strengthen the strength of the retaining mechanism of the three-way working wheel, connect the barrel hook and cover The size of the hook may be longer than the size of the double hemming. Because round hemming has much greater bearing capacity than flat hemming, triple round hemming is double or several times that of flat hemming. The round curling process can be produced as long as some improvements are made on the existing equipment. Therefore, eliminating doubts, emancipating the mind, and triple curling are by no means unattainable.
9. Due to equipment limitations, some factories divide the blanking and forming process into two procedures when processing the cover. Other factories use discs to cut the cover material, what harm will this cause to the steel drum curling seal? The bottom cover is cut out first and then formed. Incorrect positioning during forming affects the coaxiality of the edge of the cover hook and the cover. In addition, the disc shear has a tearing force in the centrifugal direction when shearing, so the force is unbalanced, and the lower cover material cannot guarantee the roundness of the periphery. The size of the cover hook after forming is inconsistent, plus the tensile deformation Waves appear on the edges, so that the processed cover will seriously affect the quality of the curling after sealing. It is better to change the compound punching die to the second-time cutting and forming process in the secondary process of dividing and cutting. If the manufacturer of the punch is about 100 tons of punching pressure, it is only necessary to change the flat edge of the composite die to a symmetrical wave edge or a symmetrical inclined edge. Because the punching force and pressing force of the composite die are not carried out at the same time, the punching force and pressing force after separation do not exceed 100 tons of punching force. The 100-ton punching press is fully capable of cutting and forming 200-liter steel drum bottom covers.
10. Civilized production is very important. In the production, especially the barrel and bottom cover of the assembly parts for the transfer of the barrel collide and hit, the barrel hook and the cover hook are curled, or the oil, mud, sand and dust are stuck, and they are not trimmed and scrubbed during sealing. The self-rolling with the cover hook or the inclusion of impurities in the seam affects the tightness of the curling.
3. Some suggestions for improving quality
1. Improve the thickness of edging and reduce the width of the welding seam at the barrel hook (11 ± 1 for the 200-liter steel drum barrel is changed to 4 ± 1 mm); increase the hot-rolling thinning mechanism when welding the weld, Make the hook of the overlying barrel close to the thickness of the barrel material.
2. Improve the coaxiality and roundness of the bottom cover hook, and change the bottom cover to first cut and then form the second process for the first cutting and forming of the composite mold.
3. Reasonably adjust the differential speed and speed ratio between the sealing disc and the sealing wheel of the sealing machine.
4. The working mode of rewinding sealing wheel is from manual screw type and pneumatic type to eccentric mechanism automatic type and hydraulic type.
5. Ensure the correct size of the spinning groove of the double round curling and triple round curling sealing wheels, and replace the worn sealing wheels in time.
6. Pay attention to the mechanical properties of the barrel hook and cover hook in the pre-treatment process, adjust the working distance of the sealing wheel at any time, and try to seal the barrel body and the bottom cover with the same mechanical properties in a batch of production.
7. Change double flat curling to double round curling or triple curling.
8. When the cover is changed to separate pre-crimping for sealing, the barrel body and the cover are sealed on the same sealing machine by three sealing wheels at one time.
9. Carefully repair the geometric dimensions of the barrel hook and cover hook according to the process drawings.
10. It is supplemented by corrosion-resistant, impact-resistant, and tough coating materials suitable for the contents as the filler in the curling.
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