Problems needing attention in manual patch welding process

Date：2021-10-15 17:21:00Views：977

SMD components are more and more popular because of their small size and easy maintenance. You can use appropriate tools and master some knowledge of manual welding SMD, and you will soon become an expert in welding SMD components. Next, we mainly talk about the precautions of manual patch welding process.

Manual welding process is generally divided into flat welding, vertical welding, horizontal welding and overhead welding. Flat welding is the most common welding method, and overhead welding is a welding method with high technical requirements. Here are the following points for attention in these welding processes:

1. Flat welding:

1) The qualified welding process, electrode diameter, welding current, welding speed, welding arc length, etc. shall be selected and verified by welding process test.

2) Clean the welded junction: before welding, check whether the groove and assembly gap meet the requirements, whether the tack welding is firm, and there shall be no oil and rust around the weld.

3) The baking electrode shall meet the specified temperature and time. The electrode removed from the oven shall be placed in the electrode insulation barrel and taken as soon as it is used.

4) Welding current: select the appropriate welding current according to the thickness of weldment, welding level, electrode model, diameter, welder proficiency and other factors.

5) Arc striking: the starting and falling arc point of fillet weld shall be at the end of the weld, which should be greater than 10mm. Arc striking shall not be carried out casually. After ignition and arc striking, the welding rod shall be pulled away from the weld area immediately to maintain a gap of 2 ~ 4mm between the welding rod and the component to produce arc. The butt weld shall be connected to the combined weld and fillet weld in time. Arc striking plates and lead out plates shall be set at both ends of the weld. The arc must be struck on the arc striking plate before welding to the weld area. For the midway joint, the arc shall be struck 15 ~ 20mm in front of the weld joint. After preheating the weldment, the welding rod shall be returned to the beginning of the weld. The welding can be carried out before the weld pool is filled to the required thickness.

6) Welding speed: constant speed welding is required to ensure uniform weld thickness and width. From the inside of the mask, it is appropriate to keep an equal distance (2 ~ 3mm) between molten iron and slag in the molten pool.

7) Welding arc length: it is determined according to different electrode models. Generally, the arc length is required to be stable. Acid electrode is generally 3 ~ 4mm and alkaline electrode is generally 2 ~ 3mm.

8) Welding angle: determined according to the thickness of the two weldments, the welding angle has two aspects: one is that the included angle between the electrode and the welding forward direction is 60 ~ 75 °; Second, there are two cases of the included angle between the electrode and the welding. When the thickness of the weldment is equal, the included angle between the electrode and the weldment is 45 °; When the thickness of the weldment is different, the included angle between the electrode and one side of the thicker weldment shall be greater than that between the electrode and one side of the thinner weldment.

9) Arc stopping: after each weld is welded to the end, the arc pit shall be filled, and the arc shall be carried out in the opposite direction of the welding direction, so that the arc pit is thrown inside the weld bead to prevent the arc pit from biting. After welding, the arc plate shall be cut off by gas cutting, polished and leveled, and shall not be knocked down by hammer.

10) Slag removal: the slag shall be removed after the whole weld is welded, and the welding can be continued only after the welder's self inspection (including appearance and weld size) is confirmed to be free of problems.

2. Vertical welding:

The basic operation process is the same as that of flat welding, but the following problems shall be paid attention to:

1) Under the same conditions, the welding power supply is 10% ~ 15% less than the flat welding current.

2) Short arc welding is adopted, and the arc length is generally 2 ~ 3mm.

3) The electrode angle is determined according to the thickness of weldment. The thickness of the two weldments is equal, and the included angle between the electrode and the electrode in the left and right directions is 45 °; When the thickness of the two weldments is different, the included angle between the electrode and the thicker weldment side shall be greater than that on the thinner side. The electrode shall form an angle of 60 ° ~ 80 ° with the vertical plane, so that the angular arc is slightly upward and blown to the center of the molten pool.

4) Arc stopping: when welding to the end, fill the arc pit with arc discharge method, move the arc to the center of the molten pool and stop the arc. It is forbidden to throw the arc pit aside. In order to prevent biting, lower the arc and change the electrode angle to make the electrode perpendicular to the weldment or blow slightly downward from the arc.

3. Transverse welding:

It is basically the same as flat welding. The welding current is 10% ~ 15% less than that of flat welding under the same conditions, and the arc length is 2 ~ 4mm. Angle of welding rod: during horizontal welding, the welding rod shall be inclined downward with an angle of 70 ° ~ 80 ° to prevent molten iron from falling. According to the thickness of the two weldments, the electrode angle can be adjusted appropriately, and the forward direction of the electrode and welding is 70 ° ~ 90 °.

4. Overhead welding:

It is basically the same as vertical welding and horizontal welding. The included angle between the electrode and the weldment is related to the thickness of the weldment. The electrode is at an angle of 70 ° ~ 80 ° with the welding direction. Small current and short arc welding should be used.

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