The third part of the paper on electric welding technology: analysis of electric welding technology

In recent years, with the increasing demand for welding in China's market, a large number of foreign welding machinery products have flooded into China's machinery market, providing a broad market space for the development of China's welding industry and laying a solid foundation for the renewal and optimization of welding technology. In this paper, the common centralized welding technology in China is analyzed, and its working points are expounded in detail for reference by peers.

Keywords: electric welding; Arc welding; welding technique

In today's social development, welding technology has been widely used in both construction engineering and industrial production, and it has also promoted the optimization and update of various types and types of welding tools. Based on this social background, all walks of life attach great importance to the research of welding technology, which is also the core content of future production.

First, arc welding.

Arc welding is one of the most popular welding technologies in the current social development, which plays an important role and significance in the current social development. In the application of arc welding, arc welding machine is the main welding equipment, through which low-voltage current is delivered to ignite the melting coated electrode and combustion plate, thus solidifying at the welding target position. In the current welding work, the common points of arc welding work include the following aspects.

1, the concept of arc welding

The so-called arc welding, also known as covered electrode arc welding, is the most widely used welding method in industry today. Its application principle is to use the heat generated by arc discharge to make covered electrode and the welding target melt and condense into a weld, so as to obtain a firm welding joint and ensure the integrity of engineering construction.

2. The working principle of arc welding

In the process of arc welding, the arc of arc welding is directly supplied by power supply, controlled by the discharge phenomenon between industrial devices and covered electrode under industrial conditions, and managed by gas ions and cathode electron emission beams. At present, covered electrode arc welding is mainly used for manual welding, which mainly adopts flat welding and vertical welding.

3, the scope of application of arc welding

At present, arc welding is mainly used to weld workpieces that can be operated manually, which includes many different working methods, such as vertical welding, flat welding and overhead welding. In addition, because covered electrode arc welding equipment has the characteristics of portability, flexible handling, wide range of materials and unlimited structural shape, this welding method can be widely used in any welding work with power supply.

4, the general provisions of arc welding

First of all, in the welding process, the grade, diameter, shape and joint form of structural parts should be analyzed in advance, and a reasonable and scientific covered electrode should be selected to ensure the normal development of welding work. At the same time, the welding process and welding parameters should be analyzed in advance. Secondly, in the welding process, the development of arc welding should be controlled in the pad, edge strip and weld, and the main reinforcement should not be burned during the work to avoid structural deformation; Thirdly, when welding, the grounding wire must be closely connected with metal structures such as steel bars to ensure work safety.

5. Matters needing attention in arc welding process selection

In today's engineering projects, if arc welding is used, the following contents must be strictly controlled in the work to ensure the smooth development and progress of the work. The first is the electric shock accident. In the process of arc welding, due to the different welding standards and welding processes, it is often necessary to replace the covered electrode and welding current and voltage in welding work. At this time, the operation requires direct contact with electrodes and plates, which is easy to cause electric shock accidents. The main causes of such accidents are unqualified labor protection articles, irregular skills of staff and illegal operation, so these aspects must be paid attention to and analyzed in advance in order to ensure the smooth progress of welding work. Secondly, prevent fire accidents, because sparks and arcs will occur in the welding process of arc welding, and even lead to an increase in air temperature. Under this condition, once inflammable and explosive articles are produced, it may cause fire accidents. Therefore, in the welding work, we must do a good job of fire prevention and control in advance to ensure the smooth development and progress of the work.

Second, the resistance welding welding process analysis

The so-called resistance welding mainly refers to a modern welding process in which the pressure is generated after the power supply is connected through the combination of workpieces, and the resistance heat is generated by using the current to contact the resistance in the adjacent area through the joint. This welding technology is also very common in current work. In the application process, it is a method of heating the workpiece to a molten or plastic state by using the resistance thermal effect generated by the current flowing through the contact surface and adjacent areas, thus forming metal bonding.

1, spot welding

Spot welding is a resistance welding method that the weldment is assembled into a lap joint and pressed between two columnar electrodes, and the base metal is melted by resistance heat to form a solder joint. Spot welding is mainly used for thin plate welding.

The process of spot welding:

First, preloading to ensure good contact between workpieces.

Secondly, electrify to form nugget and plastic ring at the weld.

Thirdly, power-off forging makes the nugget cool and crystallize under continuous pressure, forming a solder joint with compact structure and no shrinkage cavity and crack.

2, seam welding

The process of seam welding is similar to spot welding, except that the cylindrical electrode is replaced by a rotating disc-shaped roller electrode, and the weldment is assembled into a lap joint or butt joint and placed between two roller electrodes. The drum compresses the weldment and rotates, and the power supply is continuous or intermittent to form a continuous weld.

Seam welding is mainly used for welding structures with regular seams and sealing requirements, and the thickness is generally below 3 mm

3. Application

With the development of aerospace, electronics, automobiles, home appliances and other industries, resistance welding has been paid more and more attention. This also puts forward higher requirements for the quality of resistance welding. Fortunately, the development of microelectronics technology and high-power silicon controlled rectifier in China provides conditions for the improvement of resistance welding technology. China has produced a secondary rectifier welder with excellent performance. The control box composed of integrated circuit and microcomputer has been used in the matching of new welding machines and the transformation of old welding machines. Advanced closed-loop monitoring technologies such as constant current, dynamic resistance and thermal expansion have been popularized and applied in production.

Third, help welding and lap welding

1. Before welding, the assembly and positioning of steel bars shall meet the following requirements.

(1) When welding with side bars, the gap between the end faces of two main bars should be 2 ~ 5 mm.

(2) When lap welding is adopted, the bending and installation of the top of the steel bar shall ensure that the axes of the two steel bars are in a straight line.

(3) Help him and the main reinforcement to be fixed by four-point tack welding; When lap welding, it should be fixed at two points, and the positioning weld should be more than 20mnn away from the upper strip or lap end.

Under the installation condition of prefabricated members on site, when the steel bars at the joint are welded by lap joint, if it is really difficult to pre-bend the steel bars, it is not necessary to bend them.

2. When welding, the arc striking should start from one end of reinforcement or overlapping reinforcement, and the arc closing should be at the end of reinforcement or overlapping reinforcement, and the arc pit should be filled. In multi-layer welding, the first weld should have sufficient penetration, and the time and end point of the main weld and the positioning weld, especially the positioning weld, should be combined well.

Four, electroslag pressure welding

The welding process includes arc initiation, arc stabilization, electroslag and top pressure. Before welding, remove the rust at the end of steel bar within about 120mm, clamp the fixture on the lower steel bar, straighten the upper steel bar and clamp it in the movable electrode, and fill the flux box with flux. When manual electroslag pressure welding is used, direct arc initiation method can be used. First, the upper and lower steel bars are in contact. After the welding power supply is connected, immediately lift the upper steel bar by 2 ~ 4 mm and ignite the arc. Then, continue to slowly lift the steel bar for several millimeters, and after the arc combustion is stable, it will gradually decrease with the melting of the steel bar and turn into the electroslag process. After the steel bar is melted to a certain extent, the welding power supply is cut off at the same time, and the jacking is carried out quickly. After cooling 1 ~ 3min, you can open the flux box, recover the flux, remove the fixture and knock off the slag. The lifting of steel bars should be appropriate to prevent open circuit or short circuit.

Verb (abbreviation of verb) conclusion

Welding technology and technology are widely used in modern engineering construction, and various welding technologies and construction technologies are constantly innovating and developing. Using different welding tools according to the actual situation can complete the construction requirements more efficiently and with high quality.

refer to

[1] Sun Guanglei. SAFUREX duplex stainless steel welding technology [J]. Pressure vessel.2009 2009 (10/0)

Zhao Hu. Weldability and welding technology of 3 10S heat-resistant stainless steel [J]. Drying technology and equipment. 20 1 1(02)

Guess you like:

1. Material welding technical documents

2. Technical Paper on Metal Welding in Power Plant

3. Model welding training report

4. Theoretical knowledge of welding technology

5. Stainless steel welding technical documents