Research on the process of full-open steel barrel barrel crimping

Research on the process of full-open steel barrel barrel crimping
Xin Qiaojuan

After joining the WTO, the competition in the market is actually the competition for the quality of enterprise products. Recently, the author had the privilege of conducting an inspection of the barrel-making enterprises in Xinjiang. Through investigation, we found that the development of Xinjiang barrel-making enterprises was unexpected. It can be said without any doubt that the development of Xinjiang steel barrel industry has already been at the forefront of the same industry in the country as a whole. He not only represents the development direction of the industry, but also makes us full of confidence in the development of the steel barrel industry.

In recent years, the overall development momentum of the barrel industry has been unsatisfactory. In order to broaden the market, various barrel manufacturers are thinking about developing new products. In addition to the development of packaging for small barrels (such as 4 liter barrels, 5 liter barrels, 12 liter barrels, 16 liter barrels, 18 liter barrels, 20 liter barrels, etc.), it is also developed in the direction of 200 liter vats (such as 200 liter full opening taper). Barrel, 200 litre open asphalt bucket, 208 litre full open bucket, etc.). At present, the barrel products in the Xinjiang market are relatively specific, mainly concentrated in the 200-liter conical full-opening barrel and the medium-opening asphalt-filled barrel. These two products are also a new trend in the development of the steel barrel industry in recent years. Due to the relatively developed petrochemical industry in Xinjiang, the use of 200 liter steel drums in petrochemicals has maintained a steady development momentum. Due to the large number of road construction and construction industry developments in China in recent years, the demand for asphalt has increased greatly. The packaging drum for asphalt has also developed with the development of the market. However, in terms of construction, the new asphalt (gold stone pitch) is used in larger quantities. It requires packaging in a conical barrel, and ordinary asphalt is also packaged in a conical barrel, which is the development direction of the barrel industry in the future. In addition, Xinjiang is the region with the most open ports in China (15 open land ports), so the increasingly frequent foreign trade, combined with the geographical advantages of Xinjiang, is the processing base for the country to plant high-quality tomato base and tomato sauce, and the processed tomato sauce. It is generally exported in a 200-liter conical full-open steel drum. In addition to the large number of 200-liter small-open steel drums and 200-liter medium-open steel drums in Xinjiang, a large number of 200-liter tapered full-open steels are required. barrel. It is estimated that the total demand for cones for ketchup packaging in Xinjiang this year is more than 1.5 million. In Xinjiang, there are a large number of cones for packing asphalt, which is said to be very convenient for use in the field. The demand for asphalt barrels in Xinjiang is around 1 million per year. The total demand for other small open barrels is also around 1 million.

There are currently 26 barrel companies in Xinjiang, all of which produce 200 litre small open steel drums, 200 litre tapered full open steel drums and 200 litre medium open steel drums. For small and medium-open steel drums, the production process is basically mature, and for 200-liter tapered full-open steel drums and 200-liter full-open steel drums, due to their specific structure, in the production process, There are some problems, and the crimping process of the 200-liter full-open barrel mouth has always had more problems, so we will focus on this process.

There are currently two main methods for the crimping of a 200-liter conical full-open barrel. The first is to use one end of the mold to turn over the edge and the other end to be rounded. This method is more common in the imported production line; the second is to use the roller to squeeze the circle. The quality of the crimping is affected by the width of the flange of the barrel, so the quality of the curling is not stable. However, the quality of the crimping is stable and the shape is smooth and smooth. However, due to the differences in equipment and equipment of various manufacturers, many problems have arisen in the production process. Now we will analyze it from the coiling process.

First, use the mold to roll

1. Stress analysis of material at the edge of the barrel when the mold is crimped

In general, manufacturers who use molds to roll the barrels at the same time use mold flanges at the same time. The initial process of winding the circle is actually started from the mold to the flange of the barrel material, but the mold groove type is different when the straight flange and the round flange are rolled. The cuff of the barrel is a form of an elongate curved surface. The force and deformation characteristics of the blank deformation zone during the burring are shown in Fig. 1. The diameter of the blank before the burring is do, and the flange deformation zone is an annular portion having an inner diameter of do and an outer diameter of d1. During the burring process, the deformation zone is continuously increased in outer diameter d under the action of the burring force.

When the barrel is rounded, the stress and strain values ​​in the deformation zone of the barrel blank are different. The tangential deformation has a maximum value at the outer edge position of the deformation zone (the formula is abbreviated), and it increases continuously as the deformation process progresses. When the flange is finished, its value is (the formula is abbreviated). The deformation of the barrel body is affected by the two-way tensile stress and all tensile stresses (the formula is slightly) and the radial tensile stress (the formula is slightly), wherein the tangential tensile stress is the maximum principal stress. The minimum principal stress is zero. The radial tensile stress (the formula is abbreviated) is the intermediate principal stress, and its value is much smaller than the value of the tangential tensile stress (the formula is omitted).

The thickness of the deformation zone of the barrel steel during the rounding process of the barrel is continuously thinning when the flange is turned. The degree of ultimate deformation can be calculated by the flanging coefficient, and its value is:
(Formula slightly)
In the formula, K is the flanging coefficient, so the above formula can be written as:
(Formula slightly)
Where b is the width of the flange

Since the barrel is curled in the cuff, the metal in the deformation zone of the barrel produces tangential elongation deformation under the action of tangential tensile stress, so the limit flanging coefficient is mainly determined by the plasticity of the steel plate material of the barrel. When the barrel mouth is rolled, the tangential elongation deformation values ​​of the points in the radial direction of the barrel steel deformation zone are different, and the maximum elongation deformation occurs at the both end edges of the barrel steel plate. Therefore, when the flange is rounded, it should be ensured that the elongation deformation of the metal at the edge of the barrel is less than the limit allowed by the plasticity of the metal material itself.

The maximum elongation deformation produced on the outer edge of the deformation zone when the barrel mouth is rounded is:
(Formula slightly)

It can be seen from the above formula that the limit turning factor of the barrel edge curling circle is inversely proportional to the elongation rate of the steel barrel body material (the formula is slightly). In practice, however, the value of the elongation δ used in the above formula is generally larger than the uniform elongation obtained in the simple tensile test because the length of the deformation in the diametrical deformation zone is different: The elongation at the edge is maximal, and the elongation at each of the other points decreases rapidly as the distance from the edge increases. The stability of the latter plastic deformation is enhanced by the influence of the adjacent portion having less elongation and deformation on the edge having the largest elongational deformation. The tendency of the metal to locally concentrate and deform on the edge portion of the flange is suppressed, so that the edge portion of the blank at the time of the flange may obtain a much larger elongation deformation than the simple tensile test.

2. Working principle of the flange (curling) machine when the mold is crimped

In the previous section, we analyzed the case where the edge of the barrel was actually the first to be crimped when the edge of the barrel was curled. Let us look at the formation process of the following mold bead.

While the end of the barrel is crimped using the mold crimping machine, the other end of the barrel is flanged. At present, at present, there is not a manufacturer of barrels to purchase a mold flanger for the purpose of crimping, and most of them use the existing barrel equipment to complete the production of open barrels. Therefore, in general, when a manufacturer with a mold flanging machine produces a small open steel drum, the mold flanging machine is used to simultaneously turn the barrel edges of the two ends, and when the open barrel is produced, the mold of one end is replaced, and the flange is replaced. At the same time, the barreling process is performed.

The schematic diagram of the mold flanging and curling is shown in Figure 2. This method of operation generally uses hydraulic transmission. Automated production can be achieved. Its working principle is generally that the hydraulic (or pneumatic) dial mechanism is used to transfer the barrel into the flanger for coarse positioning, and then the die ejector is moved to the middle under the action of the hydraulic cylinder. When it is inside the edge of the barrel, the cone is obliquely facing the barrel body to be precisely positioned. After the position is fixed, the pressing mold continues to move to the middle under the action of the thrust, so that the pressure plate on both ends clamps the barrel, and then The edge of the barrel body is turned outwardly and curled along the arc curve of the die under the action of hydraulic pressure. When the flange width and the curling edge arc meet the process requirements, the outer edge of the flange of the barrel is externally bound by the die. The top of the circle is dead and the internal displacement of the mold is subject to great resistance. As the roundness of the barrel is formed, the strength increases, which also limits the internal movement of the mold. When the resistance received by the die reaches the set hydraulic pressure, the electromagnetic reversing valve of the hydraulic system starts to reverse, and the hydraulic cylinder is withdrawn, so that the die is quickly withdrawn from the inside of the barrel. The barrel mechanism immediately puts the barrel out of the cuffing machine.

3. The formation process of the curl when the mold is crimped

The use of mold coiling technology has been a very mature stamping process in China, and it has been used in steel barrels to shrink the volume in recent years. This is because in recent years, the ultra-light steel sheet (the thickness of the barrel sheet is δ=0.5mm, and the thickness of the top of the barrel is δ=0.65mm). The full-open steel drum has been widely used in petrochemical and food industries. Due to its low production cost and low price, its market prospects are good. In order to occupy the market as soon as possible and expand market share, those pioneers have introduced several open barrel production lines from abroad. From the perspective of these imported production lines, all of them use mold crimping, so many domestic barrel manufacturers have followed suit, but in the actual production, various kinds of curling results have appeared, and some manufacturers have rolled out the edge ratio process. The size is much smaller; some are not even round but are open arcs like the lid. Let us analyze the formation process when the mold is crimped.

The mold crimping process is actually the same as the mold flanging process, except that the groove shape of the flanging mold and the mold groove shape are different when crimping. When flanging, the groove shape of the flanging die is shown in Figure 3(a); R is the radius of the fillet when the bucket is turned; b is the width of the flange of the barrel; and when crimping, the bead is As shown in Figure 3 (b). As can be seen from the figure, the curling groove is composed of two R1 and R2 arcs of different sizes and a circle of radius R. The radius R is equal to half the diameter of the barrel. . In general, R1 is smaller than R and R2 is greater than R when crimping. The value greater than or less than R is determined by factors such as the yield limit of the barrel material when the steel barrel is crimped, and the radius of curvature of the barrel when the barrel is crimped; therefore, for the barrel of different thickness materials, despite the crimping The diameter requirements are the same, but due to the different material thicknesses, the R1 and R2 arcs in the beading groove are not exactly the same as the radius R; but when the barrel material yield limit, material thickness and When the radius of curvature at the time of curling reaches a certain value, the three values ​​are equal, that is, R1=R2=R. In addition, there is a bevel in the figure. Whether the edge of the barrel is curled or rounded, the first contact is before the mold slot is formed, so the angle of the slope (the formula is slightly) is an important parameter. In other words, it mainly serves as a guiding and positioning function; for a round-turning mold, it not only serves as a guide, but also determines how much the barrel material enters the crimping groove. (Formula slightly) The angle is too small, which is not conducive to the feeding, and sometimes it will produce the phenomenon of “outer winding”; (the formula is slightly) the angle is too large, which will affect the formation of the curling circle. In general, the (formula slightly) angle is more suitable between 5 ° ~ 8 °.

Second, use the roller to squeeze the curl

The basic working principle of using the roller for crimping is in fact consistent with the winding of the bottom of the steel drum. Its basic principle is the same as rotary bending. During the crimping process, the deformation of the material has exceeded the elastic range and plastic deformation occurs. The bending of the material does not change in a certain plane, but along the curve of the curling roller; in addition to the bending deformation of the material, there is also deformation such as extrusion. As shown in Figure 4. In general, the crimping force P can be decomposed into three component forces by spatial rectangular coordinates: Px, Py, Pz. Wherein, the tangential component Px is the force required to overcome the frictional resistance of the curling roller around the barrel; the radial component force Py is the roller of the curling roller pushing the center of the barrel to make the barrel body The surrounding force produces a certain amount of force required for radial deformation; the axial component force Pz is the force required for the crimping roller to press the crimping edge in the axial direction, but the value is small (about 1/ of the Px value) 5), the calculation for simplifying the analysis can be ignored. Thus, the curling force can be approximated as a plane force system for discussion.
However, the use of rollers to squeeze the curling edge is generally carried out by using two rollers, a head roller and two rollers. In the process of crimping, the curling of the head roller and the two rollers are not completely the same. The former mainly causes the flange of the bucket body to be squeezed to produce bending and compression hooking, and the latter mainly causes the curling to further Pressing to produce plastic deformation. Therefore, it can be discussed in two processes.

1, the first side curling force analysis

As shown in Fig. 5, when the center of the head roller is moved from O1 to O2, it is in contact with the arc ab of the barrel. The head beading force P' can be approximated as the midpoint C acting on the arc of the segment.

According to the above analysis, P' is decomposed into a component force P'x along the tangential direction of the barrel and a component force P'y in the radial direction. The figure shows:
(Formula slightly)
In the formula (the formula is omitted) - the central angle of the curling roller in contact with the barrel body;
(Formula omitted) - the angle between the diameter OC and the center line OO2;
(Formula slightly) - the average radius of the barrel in contact with the arc, ie the diameter of the point C;
(Formula slightly) - the radius of action of the curling wheel.
Substituting the (formula) value into the above formula:
(Formula slightly)

When the head roller is moved from the position O1 to O2, the rotation angle is (the formula is abbreviated), the circumferential stroke along the barrel is L, and the radial stroke to the center O of the barrel is y, and the unit radial feed is For (the formula is abbreviated), then
(Formula slightly)

Therefore, the work done by the curling wheel in this process consists of two parts:
(Formula slightly)

In fact, the work of the crimping force should be equal to the work required to achieve the desired deformation of the barrel by the rolled portion. For the head roller, if U1 is the work required for the peripheral bending deformation, and U2 is the work required for the peripheral hooking deformation, it is preferable.
(Formula slightly)
Then, by A1+A2=U1+U2, the head curling force is solved.
(Formula slightly)
In the formula (the formula is abbreviated) - the coefficient related to the elasticity of the material is generally 1.2 to 1.5.

2, the analysis of the second curling force

In order to make the barrel edge round, a satisfactory round edge is obtained, so that the elastic deformation does not occur after the crimping ends. In this way, the two rollers only play a shaping role, so its groove shape is generally a semi-circular arc.

Its force condition is shown in Figure 6. If the barrel edge formed by the head circle is regarded as a continuous annular metal strip, its initial thickness is (the formula is abbreviated), and it is changed by two round rolling rollers. For (the formula is abbreviated), the center angle of the roller corresponding to the contact arc is (the formula is omitted). If a small force body composed of a unit curl width and a cross section abdc is taken in the rolling zone, set ac=hx, bd=hx+dhx, the center angle of the roller corresponding to cd is d (the formula is abbreviated), and the cd midpoint is respectively The angle between the line connecting the center O1 of the roller and the center O of the barrel to the center line O1O is (the formula is abbreviated) and (the formula is abbreviated), the working radius of the roller is (the formula is abbreviated), and the diameter of the barrel at the midpoint of the cd is (The formula is omitted).

The cd midpoint and the barrel center O are taken as the Y axis, and the C point is made perpendicular to the axis as the X axis. The projection lengths of cd along the XY axis are ce and de, respectively. Decompose the two-unit unit curling force (the formula is slightly) into (the formula is abbreviated) and (the formula is abbreviated), then the projection of the curling force acting on the micro-area composed of the cd and the unit curling width on the coordinate axis respectively for:
(Formula slightly)
Cause (simplified formula)
Therefore (the formula is omitted)
The same reason can be obtained: (the formula is slightly)
Cause (simplified formula)
Therefore (the formula is omitted)
The friction acting on the micro-area consisting of ab and unit curl width is:
(Formula slightly)
In the formula (the formula is abbreviated) - for the friction coefficient, generally can be taken 0.08 ~ 0.12.

Considering the internal stress acting on the micro-areas of both sides of ac and bd and the unit curl width (the formula is abbreviated) and (the formula is abbreviated), and the above-mentioned forces are projected onto the X-axis, and the balance is obtained.
(Formula slightly)
That is (the formula is omitted)
Among them, high-order traces (the formula is abbreviated), (the formula is slightly) can be ignored, and
(Formula slightly)
That is (the formula is omitted)
Substituting the above formula,
(Formula slightly)

To solve this differential equation, we must first find out the parameter relationship between (the formula is abbreviated) and (the formula is abbreviated).
(Formula slightly)
In the formula (the formula is abbreviated) - the coefficient can generally be taken from 1 to 1.15; (the formula is abbreviated) - the yield limit can be taken as 23.5 × 103 N / cm 2 .
After the differentiation (the formula is omitted)
Substituting (formula) and (formula) values ​​into the above formula,
(Formula slightly)
Approximate the approximate value of the variable (the formula is slightly) (the formula is omitted), and
(Formula slightly)
This simplifies the above formula:
(Formula slightly)
That is (the formula is omitted)
Take the points on both sides and sort them out: (Formula slightly)
The integral constant C can be determined by the initial condition. When hx=h0, (the formula is abbreviated),
(Formula slightly)
Solve: (Formula slightly)
The above equation indicates that the unit radial pressure mainly depends on the size of the formula. The radial interaction force of the crimping roller on the edge B of the barrel is:
(Formula slightly)
Similarly, the combined effect of tangential action is:
(Formula slightly)
Therefore, the required crimping force for the second crimping: (Formula omitted)
Through calculation, I know, (the formula is omitted).

3, the design of the roller when rolling the edge

In order to achieve the desired crimping state, a rigorous process design is required to achieve the desired crimp shape. The main factors affecting the shape of the bead are the shape of the roller, the curve of the cam and the working process. Here we only discuss the shape and design of the wheel.

The shape of the roller curve plays a decisive role in the shape and size of the curling arc. But the design of the wheel is more complicated. There are also many influencing factors, most of which are empirical values. But one thing is certain. In the formation of the curling circle, the arc formed should theoretically be an involute. In practical applications, it is easier to use and the curling streamline is beautiful and smooth, and its roller shape is close to the involute. Since the true involute is difficult to process, the roller curve generally used in production practice is mostly formed by tangential cutting of a plurality of arcs. Figure 7 shows the shape of the head and the two rollers when the full-open steel barrel is crimped. In the figure, the ed segment is a bevel. The edge of the barrel is the first contact. The angle is an important parameter. For the head roller, the angle is too small, which is not conducive to feeding. Sometimes there is a phenomenon of “outer circle”; if the angle is too large, it will affect the formation of the curl circle. In general, the (formula slightly) angle is more suitable between 5 ° ~ 8 °.

In the figure, the cd segment is the transition section of the curled circle, and the edge of the barrel should be smoothly deformed. In general, the radius R1 should not be too large; the cb segment is a forming section of the curling circle, and the rounded edge of the barrel edge is basically formed after the passage. Therefore, the radius R2 is a more important factor. Its size directly determines the size of the curling circle, so in general, R2 is slightly smaller than the radius of the edge of the opening barrel mouth; the ab section is a straight line segment, the purpose is to make the rolling circle easy to exit after forming the curling circle.

The shape of the two rollers is relatively simple, but an arc having a radius R of half the diameter of the curling circle. The purpose of using it is mainly to shape the barrel edge curve after the head roller is curled, thereby obtaining a rounded and flat arc curling surface.

It can be seen from the above analysis that the deformation process of the full-opening barrel edge of the mold crimping and the rolling edge forming by the roller is different, but the final result is not much different. Only when the roller squeezes the curling edge, the amount of the crimping material is limited by the size of the flange of the bucket. Therefore, in the process of producing fully open steel drums, the barrel curling circle is made by the method of crimping. In addition to satisfying the process requirements, it is also necessary to obtain the maximum benefit according to the actual situation of the enterprise with minimum investment.

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