Metal packaging can making process

December 24, 2022

Nitriding treatment is developed in recent years in the production of printed Iron Cans. It is an inert gas protection device, which makes it impossible to generate an oxide film on the surface of the weld during the welding process. After the nitrides are applied to the welds, they have a beautiful appearance. , weld uniform small, paint adhesion increases and so on. Therefore, it has been widely used in recent years.

First, jet technology

The jet is a fluid jetted out of the nozzle at high speed. It is widely used in industrial automation control. Today, what we are going to introduce is the use of the entrainment effect of a jet to apply nitriding in can making.

1, the suction effect of the jet

The so-called entrainment of the jet is a jet of fluid that is ejected from the nozzle. Due to the friction between the fluid molecules, the original stationary medium around it is caused to flow forward.

As shown in Figure 1, the velocity of the jet will be reduced at this time. This phenomenon is the entrainment of the jet, also known as pumping.

2. The wall-attachment effect of the jet

If we set a pair of baffles on both sides of the nozzle, the situation does not change when the baffle is far from the nozzle, still the same as shown in Figure 1. If two baffles are brought close to the nozzle and the distance between the baffles and the nozzles is not equal, we can find that when the baffle moves to a certain distance, the jets emitted from the nozzles will change in an instant. Direction, and attached to the wall of the baffle closer to the suction flow. As shown in Figure 2, this phenomenon is called the Coanda effect of the jet. This phenomenon is caused by the pressure difference, due to the suction effect of the jet, in S1

Second, the working principle of nitriding device

Any object with speed, we can say that it has "momentum." Therefore, of course, there is momentum for the jet. If two jets are ejected from the nozzle in different directions, the two jets will combine to form a new jet, which is no longer in the same direction as any jet, but deflects an angle, according to the law of conservation of momentum. M3v3=m1v1+m2v2 As shown below, the deflection angle depends on the size of the original two jets. If the momentum of the original two jets is equal, the direction of the new jet after synthesis is exactly in the middle of the original two jets, ie, ∠α=∠β.

If m1v1>m2m2, then ∠β>∠α, the direction of the new jet will be in the direction of the jet between the two and closer to the momentum, this phenomenon is the momentum exchange of the jet. As shown in Figure 3.

The nitriding device is a fluidic device made by utilizing the momentum exchange of the jet and the Coanda effect of the jet to allow the nitrogen gas to adhere to the surface of the can body.

Third, the nitriding process

1, process

Liquid nitrogen → Depressurization → Molding motor synchronization

Solenoid valve → flow juice → jet element → attached wall body

2, jet components schematic (Figure 4)

Fourth, nitriding flow control

The key to nitriding treatment is to form a protective film of gas outside the can body to isolate the weld from the air. The formation of the protective film has a great relationship with the flow rate and flow rate of nitrogen. As shown in Figure 5, due to the blockage of the welding wheel, a small low pressure area is created on both sides of the welding wheel to drive the air flow. When the flow rate is too small, the nitride effect cannot be obtained. If the flow rate is too high, a vortex is formed at the welding point and the nitride film is destroyed. Therefore, adjusting the pressure of nitrogen gas is very important. After repeated practice, it is recommended to use a pressure of less than 1 kg/m2 and a flow rate of 0.6 L/min.

V. Compensation for nitrogen protection

Since the can body and the can body have a certain gap in the welding process, the minimum is 1 to 2 mm and more than 10 mm long. Therefore, instead of giving a control signal to the jet, the wall jet is supplemented with air so that the nitrogen does not cover the can body. Therefore, during the production process, the phenomenon that the head part is oxidized and blackened, which is usually called incomplete nitriding.

To prevent this from happening, we suggest that the internal and external nitriding devices be used together so that the nitriding nitriding to the outside nitriding a compensating air flow, so that air can not enter, in order to ensure the quality of nitriding.

Author:

Mr. Yan

E-mail:

sales@tinboxtlt.com

Phone/WhatsApp:

8618098231343