Quality Control of Steel Bar Welds and Troubleshooting of Seam Welders

Quality Control of Steel Bar Welds and Troubleshooting of Seam Welders

Nantong Auspice Welder Co., Ltd. Huang Huide

Nantong Aosite Pike Welding Machine Co., Ltd. specializes in producing seam welding machines for more than 20 years. The main products include automobile fuel tank seam welding machine, diesel engine oil tank seam welding machine, gasoline engine oil tank seam welding machine, motorcycle fuel tank seam welding machine, electric oil oil tinder Welder, transformer heat sink seam welding machine, small diameter steel barrel seam welding machine, power frequency communication, three-phase frequency conversion, medium frequency inverter, steel barrel pointless seam welding machine, automatic medium frequency inverter seam welding machine are being debugged and used among.

Let's take a look at the annual meeting of the steel drum industry to discuss the quality control of the steel barrel weld and the seam welder troubleshooting.

First, the quality control of steel barrel welds

1. Control of poor contact between conductive shaft and conductive sleeve

The working principle of the seam welder is that the low voltage and large current are short-circuited by the two electrodes, and the steel plate is melted to achieve the purpose of sealing. During the welding process of the steel drum, a large current of about 16000A will be transmitted from the transformer to the welding wheel through the movable contact surface. Due to the resistance and hardness of the material, we can not use the heat-treated steel to make the conductive shaft for the purpose of increasing the hardness. With the conductive sleeve to increase the wear resistance, only the heat-treated chrome-zirconium copper material can be selected as the conductive shaft, and copper or 94 copper is used as the conductive sleeve. Although the above two materials are used as the movable contact conductor, the electrical conductivity is improved, but the wear resistance is relatively poor, especially the hardness difference between the two materials is small, and it is easy to cause the bonding surface to be pulled or even fired and killed, when the conductive shaft When the above situation occurs on the contact surface with the conductive sleeve, the contact surface is likely to be heated, and the current is unstable during the welding of the seam welder, and the weld seam leaks. Therefore, the seam welder must use chromium-zirconium copper with softening temperature and high hardness as the conductive shaft, so that it is not easy to cause pulling and the like. At the same time, the operator should refuel between the conductive shaft and the conductive sleeve. When it is found that the conductive shaft and the conductive sleeve are seriously worn, it must be replaced in time to ensure the stability of the welding current, so as to avoid the contact current between the shaft and the sleeve, the current parameter is changed. Causes weld leaks.

Our company's recently developed fully automatic seam welder has changed the bushing structure used in past steel barrel seam welders, using a combination of a butterfly conductive ring and a silver tile conductive ring. Due to the automatic compensation function of this structure after wear, the stability of the welding current is greatly improved.

2. Poor control of the contact faces of the individual conductors in the electrode circuit

During the production process of the steel drum, the surface of the seam welder looks normal welding, and the network voltage, controller and welded steel plate are also normal. However, severe cracking and leakage often occur during the process of leaking the steel drum. This is likely to occur in the electrode loop of the seam welder due to oxidation, ignition, loose screws, etc. bad. At this time, the direct short circuit method can be used. When the cooling water is normally watered, the current is directly short-circuited according to the normal welding current. After about ten minutes, it is checked that the part is particularly hot, indicating that the contact surface of this part is definitely problematic and needs to be Disassemble for correction processing.

3. Control of uneven welding speed of seam welder

In the welding process, due to the non-standard production of the feeding frame, the positioning wheel, the clamping wheel, the inner and outer material frame of the spotless seam welding machine, the automatic seam welding machine are adjusted too tightly, or other parts such as the guide groove are improperly positioned. In the welding process, the resistance of the steel drum is large or small, resulting in uneven speed, so that under the same specification, the heat is suddenly increased and the heat is unstable, and the weld leakage and cracking are unstable. At this time, we must promptly check the hidden parts of the seam welder that may cause uneven speed and promptly eliminate them.

4. Control of welding pressure

The seam welder is a kind of electric resistance welder. It is used to melt the workpiece and directly melt the metal by direct current short circuit to achieve the purpose of welding. In the case of the same welding current, the welding pressure is different. The difference in resistance between the two types of heat generation is different. The higher the pressure, the smaller the resistance between the steel plates. On the contrary, the greater the resistance, the consistency of the welding pressure is maintained, and the welding current is stable, and the welding quality is directly related. Therefore, under normal production conditions, it is necessary to control the consistency of the welding pressure. When we use the welding pressure, how much pressure should be used for the thick steel plate, and the process standard should be formulated and the operation should be standardized.

5. Welding wheel material and hardness control

During the welding process of the seam welder, the steel plate is subjected to a certain pressure between the two welding wheels and is heated and melted by a large current, so the requirements for the welding wheel are high. It can now be used as a material for welding wheels. Currently, there are copper-tungsten alloys, cobalt-cobalt copper, and chromium-zirconium copper. In order to improve the utilization rate of the welding wheel, it is preferable to use a copper-tungsten alloy and a cobalt-cobalt copper having high hardness, but these two materials are expensive. There are also production plants that produce nickel-chromium-copper as a welding wheel, but these materials have a low softening temperature and are prone to brittleness and stick to the steel plate. Therefore, chromium zirconium copper is currently the most economical choice as a welding wheel, but the heat treatment hardness of chromium zirconium must meet the national standard HRB75o or above to ensure the durability, economy and welding quality of the welding wheel. At the same time, during welding, the iron shovel and garbage on the surface of the welding wheel must be cleaned to avoid changes in the welding current.

6. Control of the edge width of the steel plate

The weld seam of the cross-cut seam welder looks like it is all welded, but it is not. The melting site of the weld is composed of two regions, a solution and a nucleation. Close to the two sides of the blue zone, due to the flow direction of the current and the degree of heat dissipation of the weld protection, the two sides of the weld are not necessarily completely welded, and only the intermediate nucleation part is the real weld. Therefore, there is such a rule in the welding process that the width of the weld bead is the sum of the thickness of the two steel plates plus a factor of 1.7. For example, a steel drum is produced from a 1.2 mm steel plate, and its lap width should be 1.2 mm + 1.2. The millimeter + 1.7 factor is equal to 4.1 mm. We can understand that the thickness of 1.2+1.2 mm is equivalent to the width of the nucleation, the coefficient of 1.7 is equivalent to the solution, and the minimum of nucleation cannot be less than the width of the two layers of the steel plate. The lap joint is too small, and it is easy to crack in the subsequent process such as the rib, the coil, and the burring. Therefore, it is necessary to control a certain lap width to ensure the welding quality, and it is not possible to blindly pursue the smaller the better. Of course, there are too many edges, which cost materials and electricity, and it is also disadvantageous for the use of seam welding machines. In the actual production of steel plates with a thickness of less than 0.8 mm, especially for galvanized sheets, the width of the lap width should be appropriately increased because the zinc layer may be worn away by grinding the zinc sheet.

7. Control of steel plate blanking size

In the seam welding process of the seam welder, the control of the steel sheet blanking has a considerable correlation with the weld quality. Especially when using the spotless seam welding machine and the automatic seam welding machine, if the error of the blanking is too much, the resistance of the steel plate will change when it passes through the welding wheel, causing the speed change of the steel barrel during the welding process, causing the heat not to be caused. stable. If the diagonal distance error of the blanking is too large, the width of the lap width will be different, which will also cause the change of welding heat and even the scrapping of the barrel. Therefore, the length and diagonal distance of the steel plate must be controlled when cutting.

8. Selection control of steel plate material.

At present, the steel plates supplied on the market mainly include several grades such as SPCC ST12. The higher the carbon content of the steel plate, the worse the hot solubility is, and the brittleness is easy. The welding specifications are not easy to find, and the leakage phenomenon is serious. Many steel drum manufacturers have In this regard, there are many steel drum manufacturers that encounter the same grade, the same batch, and even the quality of the same coil of steel. The same seam welding machine is the same as a welding specification, and the leakage rate of the product is different. Therefore, in order to control the quality of the weld, it is necessary to select the steel grade which is cheap and has a small yield as the preferred material.

9. Quality control of uneven grinding during galvanized sheet welding

During the welding process of the steel drum, the uneven thickness of the material has a great influence on the change of the welding heat. When the operator selects the welding specification, the thickness of the galvanized material is uneven during the grinding process or the zinc layer is not completely polished. However, there is no irregular change in heat during welding. Therefore, it is best to use mechanically when grinding galvanized sheet, less manual grinding, and it is necessary to adjust the amount and uniformity of the grinding wheel to prevent uneven thickness or oblique side. .

10. Control of unstable weldment displacement

In the welding process, in addition to the control of speed and pressure, the stability of workpiece movement is also very important. Due to mechanical reasons, the workpiece appears to be twisted left and right, up and down, and it is highly probable that leakage of steel drum occurs in a certain part. And always in a position, it is necessary to observe whether the workpiece is twisted during the welding process.

11. The control used by the controller

At present, the controllers used by seam welding machine manufacturers include ordinary microcomputer controllers, frequency converter controllers, intermediate frequency controllers, and three-phase secondary rectifier controllers. These controllers should be of relatively stable quality at present, but they are selected in welding specifications. There is a certain emphasis on the adjustment. In the selection of specifications, it is recommended to use a small current adjustment, small batch test welding of steel drums, especially when using spotless welding machine, fully automatic seam welding, welding one inspection, isotonic After the leakage and cracking phenomenon is basically stable, the welding is carried out in large quantities to prevent batch repair and even scrapping of the steel drum.

In addition, after the welding current is adjusted, if the welding speed or welding pressure is changed, the welding current should be properly adjusted to avoid cracking and leakage of the welded steel drum.

12. Cooling water temperature and water quality control

In the welding process, the seam welder is equivalent to a high-power electric furnace. Such large electric energy is transferred into heat energy, which needs to be cooled by cooling water to take away the heat. If the cooling effect is not good, the temperature of the entire electrode loop of the seam welder is getting higher and higher. As we all know, metal materials have a characteristic. The higher the temperature, the higher the resistance and the lower the conductivity. We have found this in a few customers. The welding started normally, and there was a batch leakage phenomenon after a certain period of startup. In fact, this is because the water temperature is continuously increased and the welding heat is continuously reduced, so that the product quality is unstable, so the cooling for recycling is used. Water must be equipped with effective water cooling equipment such as cooling towers. In addition, the water quality of the cooling water should be well controlled, and no garbage impurities should enter the cooling water path of the seam welder to avoid clogging the pipeline, reducing the cooling effect, or even burning other components such as the transformer, causing unnecessary trouble.

13. Network voltage stability control

The grid voltage is rated at 380V, but the actual grid is generally slightly higher than this standard. Due to the difference in network load, the network voltage is lower than 380V. When the network voltage drop is more than 10%, seam welding will occur. The heat regulation of the machine is small, the current is slightly increased, and the workpiece is broken down. When the size is slightly smaller, the workpiece will leak and crack, and the weld will be unsightly. In another case, due to the small capacity of the distribution transformer, when the other high-power electrical appliances are turned on, the network voltage is high and low, which is the most taboo for the weld. When the voltage suddenly drops or rises during normal welding, the weld will leak. In addition, the distribution transformer will be too far away from the seam welder. Therefore, these problems must improve the quality of the network, first, increase the capacity of the network transformer; second, avoid the cross-use of high-power electrical appliances; third, the seam welder should be as close as possible to the distribution transformer or increase the cable specifications. It is best to use a copper core cable. There is also the use of medium frequency seam welder or variable frequency controller seam welder to reduce the load on the network.

Second, the seam welder troubleshooting

1. The air switch trips, the welding wheel is directly short-circuited and fires.

Generally, it is a short circuit between transformers or primary and secondary breakdown. The elimination method is to disconnect the transformer and connect the cable and check with a multimeter.

2. The controller displays an alarm and does not work. It may be that the controller is short of water or the water pressure is too low, or it may be over-current, under-current, over-voltage, under-voltage of the seam welder. Remedy: Check the water pressure of the cooling water, whether the water flow is normal, and whether the heat adjustment is reasonable.

3. Transformer vibration, air switch trip, and workpiece breakdown.

It may be that the thyristor single tube is turned on or the tube is fully connected. Remedy: Replace the thyristor.

4. After starting the seam welder welding switch, the welding wheel will not come down.

It may be that the solenoid valve is not connected to the controller signal, the solenoid valve spool is stuck and does not change direction, and the solenoid valve coil has burned out. Remedy: Check if there is a current signal on the solenoid valve connection. If there is no signal overhaul controller, use the manual solenoid valve to change direction. If there is no action, replace the solenoid valve.

5. The welding wheel does not rotate after pressing the workpiece.

Remedy: Check if the controller has motor control signal, control whether the motor's relay has action, whether the motor has burned out, whether the speed control inverter is faulty, whether the drive shaft tip is broken or not, and whether the electrode shaft and the tile are killed. . Check the processing one by one.

6. There is no welding current after the welding wheel is down.

Remedy: Check whether the controller has the welding signal output, whether the water pressure switch is open or not, and check and repair one by one.

7. When the welding wheel is down, it will catch fire:

It is possible that the pressurizing time is too short, the supply of the gas source cannot keep up, the welding pressure is adjusted too small, and the piston seal of the cylinder is seriously worn, causing the gas in the upper and lower air chambers.

Remedy: Extend the welding pressurization time, increase the air supply pressure or configure the air storage bag, and replace the cylinder seal ring.

8. The weld is not clear.

Remedy: Check the surface of the welding wheel for burrs, shovel, unevenness or correction of the tooth tip. The working current is adjusted too much. Remedy: Polish the welding wheel, change the correction wheel, adjust the welding current appropriately, and check if the grid voltage drop is too large.

9. The weld head and tail are cracked.

Remedy: There are two kinds of phenomena: one is the current is too large to tear; the other is the current is too small to crack, if the tear is adjusted to a small current, if the crack is adjusted to a large current.

10. The width of the blue area is inconsistent.

Remedy: Carefully observe the width of the blue area. Irregularity may be that the contact surface of a certain conductor part of the secondary circuit is not good. There is a slight change in the width of the blue area. There may be problems with the main control board of the controller. Treatment method: Check the secondary circuit connection point. Repair the controller.

11. The welding wheel is misaligned.

Remedy: It may be that the conductive sleeve is too worn, and the conductive shaft and the conductive sleeve are replaced.

The above is the experience we have explored over the years through the production of seam welder and the use of the customer, for your reference, if you have any problems, please understand.

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