What is the ideal weld joint in electric welding technology?

I don't know what you want to ask, welded joints are mainly butt, lap, corner joint, and other plug welds. The performance of the joint is still the best butt, the weld strength coefficient is the highest, and the corner joint and lap joint are generally used in unimportant structural parts.

Welding methods for aluminum and aluminum alloys.

1 Welding characteristics of aluminum and aluminum alloys.

1) Aluminum is very easy to oxidize in air and during welding, and the alumina (Al2O3) generated has a high melting point, is very stable, and is not easy to remove. Hindering the melting and fusion of the base metal, the proportion of the oxide film is large, it is not easy to float out of the surface, and it is easy to generate slag inclusions, non-fusion, non-welding penetration and other deficiencies. The surface oxide film of aluminum and adsorption of a large amount of water are easy to cause porosity in the weld.

Before welding, strict surface cleaning should be carried out by chemical or mechanical methods to remove the oxide film on its surface. Strengthened protection during the welding process to prevent oxidation. In the case of tungsten TIG welding, the AC power supply is used to remove the oxide film through the "cathodic cleaning" effect.

In gas welding, a flux is used to remove the oxide film. In the case of thick plate welding, the welding heat can be increased, for example, the helium arc heat is large, the use of helium or argon-helium mixed gas protection, or the use of large-scale MIG/MAG shielded welding, in the case of DC positive connection, there is no need for "cathodic cleaning".

2) The thermal conductivity and specific heat capacity of aluminum and aluminum alloys are about twice that of carbon steel and low-alloy steel. The thermal conductivity of aluminum is more than ten times that of austenitic stainless steel. In the welding process, a large amount of heat can be quickly conducted to the inside of the base metal, so when welding aluminum and aluminum alloy, the energy is consumed in addition to the molten metal pool, there is more heat wasted in other parts of the metal, the consumption of this useless energy is more significant than the welding of steel, in order to obtain high-quality welded joints, energy concentration and high power should be used as much as possible, and sometimes process measures such as preheating can also be used.

3) The coefficient of linear expansion of aluminum and aluminum alloys is about twice that of carbon steel and low-alloy steel. The volume shrinkage rate of aluminum solidification is large, and the deformation and stress of the weldment are large, so it is necessary to take measures to prevent welding deformation. When the aluminum welding molten pool is solidified, it is easy to produce shrinkage holes, shrinkage porosity, thermal cracks and high internal stress.

In production, measures can be used to adjust the composition of the welding wire and the welding process to prevent the occurrence of thermal cracks. If corrosion resistance permits, aluminum-silicon alloy welding wire can be used to weld aluminum alloys other than aluminum-magnesium alloys. With the increase of silicon content, the crystallization temperature range of the alloy becomes smaller, the fluidity is significantly improved, the shrinkage rate decreases, and the hot cracking tendency decreases accordingly.

A: The main feature of welded joints is that they are suitable for various occasions. Including the specifications of the steel pipe are relatively flexible, and after welding with the pipeline, it has the characteristics of firm connection and good sealing performance, so it is widely used in oil refining, chemical industry, light industry, textile, national defense, metallurgy, aviation, shipbuilding and other systems; It is also suitable for all kinds of mechanical engineering, machine tools and equipment and other hydraulic transmission pipelines.

When the production of compression fittings cannot meet the needs, and in the case of strong corrosion, the use of welded joints can be preferred.

Welded joint form and characteristics.

Answers are recommended as such.

Joint form and characteristics: At present, there are more than 40 kinds of metal welding methods, but they are mainly widely used in three categories: fusion welding, pressure welding and brazing.

Fusion welding: Fusion welding, also known as fusion welding, is one of the most common welding methods. The so-called fusion welding refers to the method of heating the welded joint to a molten state and completing the welding without pressure during the welding process.

Fusion welding can be divided into: arc welding, electroslag welding, gas welding, electron beam welding, laser welding, etc. The most common arc welding can be further divided into: manual arc welding (electrode arc welding), gas shielded welding, submerged arc welding, plasma welding, etc.

Pressure welding: It is called by the welding method of pressure method (there are two kinds of heating and non-heating)."Pressure welding".Only the pressure method is used to connect the two metal parts together, which is called pressure welding. It is common to have high-voltage wire discharge pressure welding.

Brazing: A welding method in which a metal material with a lower melting point than the base metal is used as the brazing metal, and the liquid brazing metal is used to wet the base metal and fill the gap in the workpiece interface and diffuse it with the base metal. The brazing deformation is small, the joints are smooth and beautiful, and it is suitable for welding precise, complex and composed of different materials, such as honeycomb structural panels, turbine blades, tungsten carbide tools and printed circuit boards.

Before brazing, the workpiece must be carefully processed and strictly cleaned to remove oil stains and excessive oxide film to ensure the assembly gap of the interface. The clearance is generally required to be between millimeters. Common ones are soldering, carbon dioxide shielded welding, argon arc welding, and wind welding.

Welding Zhaoyu front joint is a processing technology and connection method that uses heating, pressure, or both to produce atomic bonding between two workpieces of the same sex or opposite sex. Welding has a wide range of applications and can be used for both metals and non-metals.

Welding technology is mainly used in metal base metal, commonly used arc welding, argon arc welding, CO2 protection welding, oxygen-acetylene welding, laser welding, electroslag pressure welding and other non-metallic materials can also be welded.

There are more than 40 kinds of metal welding methods, which are mainly divided into three categories: fusion welding, pressure welding and brazing.

1. Fusion welding is a method of heating the workpiece interface to a molten state during the welding process and completing the welding without pressure. During fusion welding, the heat source quickly heats and melts the interface of the two workpieces to be welded to form a molten pool. The molten pool moves forward with the heat source, and after cooling, a continuous weld is formed, which connects the two workpieces into one.

2. Pressure welding is to realize the atomic combination between two workpieces in the solid state under pressurized conditions, also known as solid welding. The commonly used pressure welding process is resistance butt welding, when the current passes through the connection end of the two workpieces, the temperature rises due to the large resistance, and when heated to the plastic state, it is connected under the action of axial pressure to become a whole.

3. Brazing is a method of using metal materials lower than the melting point of the workpiece as brazing metal, heating the workpiece and brazing metal to a temperature higher than the melting point of the brazing metal and lower than the melting point of the workpiece, wetting the workpiece with liquid brazing filler, filling the interface gap and realizing the mutual diffusion of atoms with the workpiece, so as to realize the welding method.

Welding: Welding: also known as welding, welding, is a manufacturing process and technology that joins metals or other thermoplastic materials such as plastics by heating, high temperature or high pressure.

Welding achieves the purpose of bonding through the following three ways:

1. Heat the workpiece to be joined to partially melt it to form a molten pool, and the molten pool will be joined after cooling and solidifying, and the melt filler can be added to assist if necessary;

2. Separate heating of the solder with a low melting point, without melting the workpiece itself, connecting the workpiece by the capillary action of the solder (such as soldering and hard welding);

3. At a temperature equal to or lower than the melting point of the workpiece, supplemented by high pressure, superimposed extrusion or vibration, etc., the two workpieces can penetrate and bond with each other (such as forging welding and solid-state welding).

According to the specific welding process, welding can be subdivided into gas welding, resistance welding, arc welding, induction welding and laser welding and other special welding.

There are many types of energy** used in welding, including gas flames, arcs, lasers, electron beams, friction, and ultrasonics. In addition to being used in factories, welding can also be performed in a variety of environments, such as in the field, underwater, and in space. Welding can be dangerous to the operator wherever it is, so proper precautions must be taken when performing welding.

The possible injuries to the human body caused by welding include burns, electric shock, vision damage, inhalation of toxic gases, excessive ultraviolet radiation, etc.

Hello, the definition of welding is simple and clear, and the answer is that through a certain way, the welding base metal is melted and fused together, and the strength is the same as that of the original base metal, so as to achieve the purpose of welding

Welding is the process of forming a permanent connection between the materials of the workpiece to be welded (the same or different kinds), through heating or pressurization or both, and with or without filling materials, so that the materials of the workpiece can achieve the harmony between atoms and form a permanent connection.

Welding is done by heating or pressurizing or both.

With or without filler material to make weldments to be combined, a processing technology method.

Welding: It is a process that forms a permanent connection through heating or pressurization or both, with or without the use of filler materials, so that the welded workpiece (the same or different material) can achieve interatomic bonding.

Welding welding is a process in which the material of the workpiece to be welded (the same or different species) is used by heating or pressurization or both, and with or without filler materials, so that the material of the workpiece can achieve the harmony between atoms and form a permanent connection.

(1) The welded joint is composed of the weld metal and the heat-affected zone.

1) Weld metal: When welding is heated, the temperature at the weld is above the liquidus line, and the base metal and the filler metal form a common molten pool, which becomes a cast structure after condensation. During the cooling process, the liquid metal crystallizes from the fusion zone to the center of the weld, forming a columnar crystal structure.

Due to the alloying effect of the electrode core and coating in the welding process, the chemical composition of the weld metal is often better than that of the base metal, as long as the welding rod and welding process parameters are reasonably selected, the strength of the weld metal is generally not lower than the strength of the base metal.

2) Heat-affected zone: During the welding process, the metal on both sides of the weld has a change in structure and properties due to the thermal action of welding.

2) The heat effect zone of low carbon steel is divided into fusion zone, superheat zone, normalizing zone and partial phase transformation zone.

1) The fusion zone is located between the weld and the base metal, and part of the metal is roasted and part is not melted, also known as the semi-melted zone. The heating temperature is about 1 490 1 530 °C, and the composition and structure of this area are extremely uneven, the strength is reduced, and the plasticity is very poor, which is the source of cracks and local brittle failure.

2) Superheating zone is close to the fusion zone, and the heating temperature is about 1 100 1 490 °C. Due to the temperature greatly exceeding AC3, the austenite grains grow sharply, forming a superheated structure, which greatly reduces the plasticity and reduces the impact toughness value by about 25% to 75%.

3) The heating temperature of the normalizing area is about 850 1 100 °C, which belongs to the normal normalizing heating temperature range. After cooling, uniform and fine ferrite and pearlite structures are obtained, and their mechanical properties are better than those of the base metal.

4) Partial phase transition zone The heating temperature is about 727 850 °C. Only part of the tissue is transformed, and the tissue is uneven after cooling, and the mechanical properties are poor.

The welded joint consists of three parts: the weld, the fusion zone and the heat-affected zone.

The material of the workpiece being welded is called the base metal (or base metal). The weld is the bonded part formed after welding (that is, the part of metal that is cooled and solidified after being heated and melted during welding); The heat-affected zone is the area where the metallographic structure and mechanical properties of the material change due to the influence of heat (but not melting) during welding or cutting; The fusion zone is the area where the weld transitions to the heat-affected zone. Therefore, welding quality is often evaluated by the performance of welded joints.

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