What are the disadvantages of the impact method arc initiation and scratching method?

Although the scratching method is relatively easy to start the arc, if this method is not used properly, it will scratch the surface of the weldment. In order to minimize the damage to the surface of the weldment, the welding groove should be scratched, and the length of the scratch should be 20 25mm. When welding in a narrow place or when scratches are not allowed on the surface of the weldment, the impact method should be used to start the arc.

The arc striking method is difficult to master, the lifting action of the welding rod is too fast and the welding rod is too high, and the arc is easy to extinguish; If the action is too slow, the electrode will stick to the workpiece. When the electrode is glued to the workpiece, the electrode should be quickly swung left and right to separate it from the weldment; If it still cannot be separated, the welding tongs should be released immediately to cut off the power supply, so as to avoid damage to the welding machine due to the short circuit time being too long.

1。Scratch method. The action is like a match, first align the end of the electrode with the weld, and then twist the wrist to make the electrode gently wipe on the surface of the weldment, after scratching about 20mm, lift the electrode 3-4mm, after the arc is ignited, the arc length should be kept within the required range immediately, and with the help of the illumination of the arc, the arc should be moved to the starting welding point to start welding.

2。At 10-20mm before the initial welding joint, gently touch the welding piece with the lower end of the electrode, tilt the electrode to the right (or left) at the moment of contact, and immediately lift the electrode, and use the arc light illumination to lead the arc to the initial welding joint to start welding.

The scratching method is easier to master than the impact method, but in order not to scratch the surface of the weldment, it is advisable to use the impact method when welding alloy steel or stainless steel workpieces.

The impact method is simple and practical, but it is only suitable for acid electrodes.

The alkaline electrode should be sassafras to avoid porosity at the arc strike.

The arc drawing method is to first align the end of the welding rod with the workpiece, and then gently scratch the welding rod on the surface of the workpiece like a match to ignite the arc, and the shorter the stroke length, the better, generally between 15 and 25mm. The electrode is then quickly lifted to such a position that the arc length is maintained at a height of 2 4mm and is allowed to burn steadily. Then immediately move to the place to be welded, stay for a while (play the role of preheating), then shorten the arc to slightly less than the diameter of the electrode, do an appropriate amount of lateral swing at the initial welding point, and stabilize the arc at the root of the groove, and start normal welding when the molten pool is formed, as shown in Figure 2-5a.

The advantages of this arc striking method are that the arc is easy to ignite, easy to operate, and has high arc initiation efficiency. The disadvantage is that it is easy to damage the surface of the workpiece, and it is rarely used when welding full-scale products.

There is a convenient way, you can put a piece of scrap next to the welded workpiece, first use the welding rod to knock the arc on the scrap, and then weld on the workpiece, it will be easy to ignite the arc;

The arc is like a match, and the fixed-point arc is like the current electronic lighter; The success rate of arc initiation in the former is not high, and the success rate is lower with the increase of use time. The latter has a high success rate of arc initiation.

Electrode arc welding is the use of low voltage, high current discharge to produce arc, therefore, electrode (how to choose electrode) must be instantaneous contact with the workpiece to achieve, there are two methods of arc initiation in the process:

The first type: the impact arc method. Click on the surface of the weldment with an electrode, and then quickly lift the electrode to keep a distance of 2-4mm between the end of the electrode and the surface of the weldment, so that it can produce an arc.

The second type: scratch arc method. The lower end of the electrode is scratched on the surface of the weldment like a match, and when the end of the electrode leaves the surface of the weldment 2-4mm, an arc is generated.

There are two types of arc initiation methods for electrode arc welding: scratch method and direct impact (impact) method.

1) Scratch method. The scratching method is easy to master, but it is easy to contaminate the weldment when the operation is not skilled. In order to reduce the contamination of the weldment, the arc striking should be carried out in the groove, and the stroke length should be as short as possible (20 - 25mm is appropriate).

After arc initiation, quickly move the arc to the weld and pause for a moment to preheat as necessary. When the top heat is upset, the arc is appropriately elongated (about times the diameter of the electrode), and then the arc is shortened (the arc length is equivalent to the diameter of the electrode), and heated at the root of the groove of the starting point to form a molten pool for normal welding.

The arc striking when the joint is connected should be 15mm in front of the arc pit. The groove surface is carried out, and then return to the arc pit and stop for a while, and then press the arc short to continue normal welding. Attention should be paid to keeping the same height and width of the whole weld in order to ensure the quality of the weld.

For this reason, it is hoped that the arc breaking time is as short as possible, and if it is an arc break that needs to be replaced, the operation of replacing the welding rod should be as skilled and fast as possible.

2) Direct Hit Method. The direct attack method can be carried out at the starting welding place, and the pollution of the weldment is light, but the welding rod and the starting welding point should not be used too violently to prevent the coating from falling off and causing the temporary bias blowing of the arc. The operation after arc striking is the same as the scratch method.

When the joint connection adopts the direct arc striking method, the arc striking should be carried out on the groove on the side of the arc pit (the end of the melt pool).

When the current is relatively small, the scratching arc method is used, and it is not easy to stick the welding rod.

When the current is relatively large, you are not afraid of sticky strips, and you can use any arc striking method.

The sassafras method is like a match, and the direct hitting method is the point method.

There are two kinds:1Striking arc method:

At the beginning of the welding, the electrode is perpendicular to the contact and impact action of the weldment, and the arc is ignited after the electrode is quickly lifted at a distance of 2 4mm after the formation of a short circuit, and the arc should be triggered on the groove on one side of the end of the molten pool. 2.Scratch arc method:

The electrode is swiped on the surface of the weldment to ignite the arc.

Reference: Welding Handbook Volume I.

The arc striking methods of various electrodes, acidic and alkaline electrodes are slightly different, I learned!

1. At the beginning of arc arc welding, the process of igniting the welding arc is called arc initiation.

2. The methods of arc initiation include the following two categories:

1.Non-contact arcing refers to the use of high-frequency voltage to conduct gas between the end of the electrode and the weldment to produce an arc. This method is rarely used for electrode arc welding.

2.When contacting the arc starting, the electrode and the weldment are short-circuited, and then the electrode is pulled open to ignite the arc. According to the different operating techniques, it can be divided into two types: percussion method and sassafras method.

1. Percussion method: make the electrode contact perpendicular to the surface of the weldment, when the end of the electrode touches the surface of the weldment, the electrode is quickly lifted and kept at a certain distance, and the arc is ignited immediately. When operating, the welder must master the time and distance of the wrist up and down movements.

2. Scratching method: first align the end of the electrode with the weldment, and then scratch the electrode on the surface of the weldment, when the arc is drawn and then take advantage of the moment when the metal has not begun to melt in large quantities, immediately maintain the distance between the end of the electrode and the welded surface at a distance of 2 --4mm, and the arc can be burned stably. If the welding rod and the weldment stick together, as long as the welding rod is shaken left and right a few times, it can be separated from the weldment, if it can not be separated from the weldment at this time, the welding tong should be relaxed immediately, the welding circuit is disconnected, and the welding rod is slightly cold before being removed.

3.Apply; Due to the low temperature of the arc striking end and the shallow penetration of the penetration, it is easy to produce unwelded penetration. When the acid electrode is connected to the arc, the arc can be slightly elongated, the root of the groove can be preheated, and then the arc can be lowered for normal welding.

Alkaline electrode is beneficial to root penetration due to the characteristics of the coating, and there is no need to use the arc striking method of acid electrode, but do not start the arc directly, and quickly pull back the starting end after the arc is triggered at the front end of the groove at a distance, and the arc is lowered for welding.

3. Contraindications for the operation of the transport strip:

1.If the electrode is pulled up too fast or lifted too high during operation, the arc cannot be ignited or the arc is extinguished after only burning for a moment. Conversely, if the action is too fast, the electrode may stick to the weldment, causing a short circuit in the welding circuit.

2.If the electrode sticks to the weldment during arc initiation, the welding tong should be relaxed immediately. If the short-circuit time is too long, the short-circuit current will burn out the welder.

Scratch arc initiation is a type of contact arc initiation.

1. There is no XZ7250 welding machine, only ZX7-250 welding machine.

2. ZX7-250 welding machine is an inverter electrode hand arc welding machine, which can only scratch the arc and be used for simple argon arc welding.

3. The welding method is divided into two ways: contact arc striking and non-contact arc striking, and the contact arc striking has electrode arc welding and carbon dioxide gas shielded welding; Non-contact arc striking includes tungsten argon arc welding and plasma arc welding. ZX7-250 welding machine is a welding rod welding machine with contact arc strike.

4. There are two ways of contact arc initiation: impact arc initiation and rubbing arc initiation.

5. Impact arc initiation method: the contact and impact action of the welding rod perpendicular to the weldment at the beginning of the weldment, and the arc is ignited after the electrode is quickly lifted at a distance of 2-4mm after the formation of a short circuit. At 10-20mm before the initial welding joint, gently touch the welding piece with the lower end of the electrode, tilt the electrode to the right (or left) at the moment of contact, and immediately lift the electrode, and use the arc light illumination to lead the arc to the initial welding joint to start welding.

6. Scratching arc initiation method: the arc can be ignited by swiping the welding rod on the surface of the weldment. The action is like a match, first align the end of the electrode with the weld, and then twist the wrist to make the electrode gently wipe on the surface of the weldment, after scratching about 20mm, lift the electrode 3-4mm, after the arc is ignited, the arc length should be kept within the required range immediately, and with the help of the illumination of the arc, the arc should be moved to the starting welding point to start welding.

There is no Z7x250 welder.

It is ZX7-250 welding machine, inverter electrode hand arc welding machine. It can only be used as a simple TIG welding machine.

Scratching arc initiation, that is, the tungsten electrode is in contact with the workpiece like a match, and the short circuit current is large at the moment of scratching, resulting in an arc. Scratching arc initiation is a contact arc initiation method.