The origin of tinplate

Tinplate was called “Yangtie” in the early days, and its official name should be tinned sheet steel. Because China’s first batch of foreign iron was imported from Macau in the middle of the Qing Dynasty, Macau was transliterated (Makou) at that time, so the Chinese generally called it (tinplate).

What is tinplate

Tinplate is the common name for electroplated tin sheet steel. The English abbreviation is SPTE, which refers to cold-rolled low-carbon thin steel sheet or steel strip plated with pure tin on both sides, also called tin-plated iron. Tin mainly plays a role in preventing corrosion and rust. It combines the strength and formability of steel with the corrosion resistance, solderability and beautiful appearance of tin in one material. It has corrosion resistance, non-toxicity, and high strength. , Good ductility characteristics.

The characteristics of tinplate

Tinplate is widely used in packaging, which has its advantages:

(1) It is opaque. In addition to the deteriorating reaction of food, light can also cause changes in protein and amino acids. The opacity of tinplate makes the preservation rate of vitamin C higher.

(2) Good sealing

(3) The reduction effect of tin can reduce the chance of food being oxidized

(4) Provide a source of effective iron. Due to the electrochemical effect of metal, a small amount of iron will dissolve in the storage of canned food. It exists in the sealed canned food in the form of divalent iron and is easily absorbed by people.

Because of these properties, tinplate cans provide a closed system that completely isolates environmental factors in addition to heat. Using it to store food and beverages can prevent food from deteriorating due to light, oxygen, and moisture, and it will not be affected by aroma penetration. It becomes weaker or becomes smelly through pollution by environmental odors. The storage stability of food is better than other packaging materials, the preservation rate of vitamin C is higher, and the retention of nutrients is also better.

The above is a small point of tinplate knowledge. In fact, the story happens in our lives. We are full of knowledge in our lives and work. As long as we are good at learning, boring things will become very interesting and your spirit will also change. Very rich.

With the help of canning equipment, the production of tin cans becomes very easy. The process has gone through a series of canning equipment production lines, most of which have been integrated into one process. Usually, the first step involves the slitting process, during which the main body, bottom and cover will be obtained. Then there is a canning machine that automatically makes cans. Then do top crimping, then necking, flanging and final seam.

The widely used cans are made of tin and aluminum. However, these two types do not have the same properties. Although most industries use them for conventional packaging processes, they usually go through different manufacturing processes.

At the beginning of establishment
Tin cans were first used for storage purposes in the 1810s, and aluminum was introduced in 1965. These two types of tin cans have many uses, but the main purpose is to preserve food for local and overseas consumption. These two types can protect food from air and light. They are also very durable and can be recycled.

Tin can
Tin cans are generally ductile at room temperature because they are composed of crystalline metallic elements. They are extracted from elements such as cassiterite, tin compounds and oxygen. The refining process of tin makes it very suitable for manufacturing. It is not easy to corrode, which is why it can be used for packaging food. Some modern tin cans have a steel coating and a layer of tin to make them corrosion resistant.

Aluminum
Compared with other minerals, aluminum is a relatively cheap mineral element. This is because they are high in content, accounting for 8.2% of the earth’s crust. However, refined aluminum is a bit complicated because it has other compounds, such as aluminum oxide or aluminum sulfate. Most aluminum cans are light and strong.

Difference
One of the main differences between the two is weight. Tin cans are heavier than aluminum cans and are usually strong and durable. They have corrosion resistance and are therefore very suitable for acidic foods such as tomatoes. However, in terms of recycling, aluminum cans are more efficient. Compared with refined new aluminum, you will save a lot of money when recycling aluminum.

When making cans, make sure that the canning equipment you buy is fully automated and easy to use.

Is the appearance of numerous machines an important sign of mechanized mass production? When people begin to have a new understanding of the new industrial era, others are gradually becoming familiar with the development and new significance of the new production machines that emerge from time to time in the mechanized era. The mastery and analysis of can seaming machine products has caused many people to chase after it. In fact, many people have never explained the significance of mechanization in the new industrial era in the analysis of existing industrial new products.

In the more appropriate time of industrial production, all the simple models of mechanical products have never been transformed into new ways that all kinds of people can truly control. Perhaps in the new stage of industrialization, people should know something about can seamers based on the existing improvements. Everyone who knows something has discovered that the more innovative discoveries have finally made everyone understand. Gradually, I realized how the authentic charm of the industrial age might have a new turn. From industrial closure to the current newer industrialization period, everyone is slowly feeling what kind of analysis and design methods are needed for the reform of today’s new industrial era. Perhaps the real choice of industrial design has always been particularly clear. When a variety of different industrial machinery products really appeared, many people began to make good use of the recent tube sealing methods, and the standards of various machinery products and services used were all clear.

The prudent industrial production design process has never lacked the significance of the new industrial mechanization. For different industrial production concepts, everyone will embark on a wonderful journey of mechanized industrial production.

The inner coating of food cans is an organic coating applied on the inner wall of metal cans. Its function is to prevent metal from contacting food, avoid electrochemical reaction and metal pollution, so as to protect food quality and improve the shelf life of food. However, some harmful substances contained in paint, such as BPA (bisphenol-A), BADGE (bisphenol-A diglycidyl ether), NOGE (novolac glyceryl ether) and their derivatives, etc., will be Content migration not only affects the nature of the paint, but more importantly, it will contaminate food and affect the health of consumers. These substances are widely present in various coatings, and their harm to human health and the environment has aroused widespread concern in society.

The newly formulated food packaging regulations of the European Union have stricter restrictions on BADGE, BPA, BFDGE, etc. At present, my country’s national standards concerning the hygienic indicators of inner coatings of cans, such as GB4805-94 “Hygienic Standards for Epoxy Phenolic Coatings for Food Cans”, GB9683-88 “Hygienic Standards for Polyamide Epoxy Coatings for Food Containers”, and its testing items are also Only limited to free phenol, evaporation residue, potassium permanganate consumption, there is still a big gap compared with foreign countries. For example, there is no index for heavy metals in the hygienic index of epoxy phenolic resin, and the index for heavy metal (lead) in the national standard “Analytical Method for Hygienic Standards of Polyethylene, Polystyrene, and Polypropylene Molded Products for Food Packaging” is simply used. The colorimetric comparison does not require accurate determination of heavy metal content. These hygienic indicators are far from meeting the needs of canned food export.

Research on coating materials, coating production technology, testing, laboratory methods and related standards on the inner wall of food metal packaging containers is urgent and imperative.

At present, the bottom flushed round cans used in domestic production are made by drawing tin or chrome-plated sheet by a shallow drawing method, and the ratio of the height of the can to the diameter of the can is less than 1. Since the can body is shallow and has no seams, it is now mostly used for canned fish, shellfish, shrimp, crab, etc., which can reduce the corrosion of the can wall.

Since the punching and cupping (shallow punching) mainly uses the ductility of the tin-plated sheet, the sheet is plastically deformed under the squeezing action of the die to form the required container shape, so the process flow is relatively simple, and the key process is the punching of the can body Trimming and trimming are done on the punching machine with the help of different stamping dies.

1. Since the metal material of the shallow punching plate tank is not thinned during the punching and drawing process, in order to ensure the thickness of the tank bottom, a thicker plate is required to avoid bending and deformation of the tank bottom.

2. For the empty cans with deep stamping, it is required to use the soft-pointed sheet after quenching and tempering to adapt to the pressure in the stamping process, so that the sheet has better plasticity and avoid the iron sheet breaking during the stretching process, and the hardness is generally required. The grade is T2, if it exceeds T4, it is difficult to draw.

3. The tin-plated layer of the sheet has lubricating properties during the drawing process. If you use paint tin-plated sheet, you can use 2.8/2.8g/m2 (0.25 pounds/basic box) tin plating. However, drawing with plain iron requires 5.6/5.6g/m2 (0.50 lb base box) or 8.4/8.4g/m2 (0.75 lb/base box) tin plating.

4. The thickness of the plate used for punching and cupping also depends on the pressure of the product, the vacuum requirement and the adaptability of the double-roll seal of the top cover.

5. The blanking size of the punching and cupping tank is calculated according to the expanded area after forming. In the actual stamping process, the expanded area of ​​the container is generally slightly larger than the calculated area for trimming.

The stretching principle of cupping
1.The forming process of punching and cupping is shown in Figure 1-32.

Punching and cupping is an integral structure formed by punching the punch to the die to stretch the sheet. When the punch is driven by the crankshaft of the punch into the punch, the sheet is punched and the designed container is formed according to the shape of the punch.
2.The force analysis in the stamping process is shown in Figure 1-33.

Circular punching and cupping The diameter D of the plate used for punching and cupping is larger than the diameter d of the punch. When punching, the plate starts from the outer diameter of the punch and takes the outer part into the gap between the punch and the die, and is on the circumference The internal stress P1 is generated in the direction. Since the gap is basically the same as the thickness of the sheet, the sheet is not allowed to become thicker after shrinking. As the circumference shrinks, the sheet is bound to be compressed. In order to adapt to this shrinkage phenomenon, it can only extend in the radial direction. , Produce the elongation internal stress P2. When the plate continues to move into the concave die, the die mouth receives the greatest external force, and correspondingly produces intense deformation. Because the elongation force in the radial direction is greater than the compression force in the circumferential direction, the metal plate is elongated and stretches along the punch and The gap of the die forms a cylindrical cupping can.

3.The deformation of each part during drawing is shown in Figure 1-34.

(1) At the edge of the board

When the plate shrinks from the large diameter direction and is clamped and pulled into the concave die by the pressure of the punch at the same time, the shrinkage in the circumferential direction, the elongation in the radial direction and the increase in thickness are produced at the same time. Therefore, stress and deformation When these three aspects occur at the same time, the outer edge part deforms the most.

(2) At the cavity of the cavity

The crystalline change of the metal in this part is the most intense. It requires the flat plate to be squeezed into an upright cylinder through the arc surface of the concave die mouth, so the force is the largest, the stress and deformation are also generated at the same time, and the thickness increases accordingly.

(3) In the gap between the punch and the die

This part of the plate is only subjected to downward pressure from the punch, and thus stretches. The stress is mainly in the radial direction and the deformation is generated at the same time in the radial direction and the thickness direction. Because the volume of the metal does not change, after the sheet is elongated, the thickness of the metal will be thinned in different degrees in this part.

(4) In the rounded part of the punch

This part of the metal is the first to receive the pressure of the punch, and is also the first to be elongated, and the thickness is reduced. The internal stress is the same as that of the concave die, and it is also generated in three directions at the same time. The deformation is generated in the radial direction and the thickness direction.

(5) On the bottom part of the punch

This part is affected by the tensile force of the surrounding metal, and the diameter is slightly increased, but the deformation is within the elastic limit of the metal, so the thickness is not reduced or slightly thinned.