1. Essence of characteristics and use of welding.

The essence of welding is the process of connecting two or more components into a single unit by using a heat source that heats up the liquid (or plastic) state, Crystals (or press force) form the weld.

Portable welding machine specification and application

– Solder links are non-removable fixed links.

– Compared to rivets save 10 to 20% of metal mass, compared with 50% savings cast.

Welding helps to create complex shapes, connecting metals of the same nature or different properties.

– Welds have high durability and tightness, meeting the requirements of important structures (hulls, tanks, boilers, etc.).

– The welding process can be automated or mechanized.

– The cost of fabrication is very cheap.

– However, welding has some disadvantages: Existence of stresses and deformation left over after welding, the area of ​​heat effect appears to reduce the structural strength of the structure.

2. Classify welding methods.

* Based on the energy used, welding techniques are divided into the following methods:

– Methods of electric welding: Using electric power to heat (electric contact welding, electric arc welding, etc.).

– Mechanical welding methods: Using metal deformation at the welding area (cold welding, friction welding, ultrasonic welding, etc.)

– Methods of chemical welding: Use of energy generated by chemical reactions to heat metal welding (welding, heat welding, etc.).

Combined welding methods: Use the combination of the above energies (welding of solderable materials).

* Based on the metal state of the weld at the time of welding.

– Melt welding:

Include welding methods: welding, electrode welding, arc welding, etc. Metal welding in liquid state during welding.

– Pressure welding:

Including welding methods: ultrasonic welding, welding, diffusion welding, contact resistance welding, etc. Welding metal in plastic flowing state.

3. Weld forming and welding metal organization.

Factors affecting the transfer of liquid metal from the electrode to the welding puddle.

Effect of liquid metal gravity drops

Liquid metal under the influence of gravity always tends toward the puddle (which has a large effect on welding).

Surface tension

Surface tension is created by the action of molecular forces. Molecular forces tend to make the surface of the liquid shrink, giving the liquid surface the smallest amount of free energy.

Surface tension causes the liquid metal spheres to be spherical and remain in this state throughout the transfer to the weld pool, where the welded surface is pulled by the surface tension to form a uniform mass ( Great effect on space welding.

Magnetic force

Magnetic force emanates around the electrode when current flows through the electrodes and the weld. This force acting on the electrode liquid electrode reduces the cross sectional area. Whereas Ih = const, at the point where the density of current J increases rapidly, the liquid metal reaches boiling point, cutting off the liquid metal from the electrode. On the other hand, because of the large area of ​​the welding pool, the magnetic field strength on the surface of the welding pile is small and the density of the j current is small, so that the liquid metal always tends to enter the welding pool at every welding position.

Gas pressure

Due to the high arc temperature, the reaction occurs very strongly, the hot melt welding electrodes (welding solder) will generate more gas, creating pressure to push the liquid metal from the electrode into the puddle (which has a large effect). For welds in space).

4. Metallurgical process when electric soldering melts

The concept of welding

Welding Pots are made of liquid metal created during welding under the effect of a heat source.

Vung Han consists of two parts:

– Head (A): Occurs in the process of melting basic metals and additional metals.

– tail section (B): formation and formation of welds occur.

The shape and size of the pile depends on many factors: the power of the heat source, the method and mode of welding, the thermal properties of the welding metal, etc.

Weld

Liquid metal composition is crystalline in the weld, it is liquid. According to the horizontal section, the weld is divided into two types: welded joints and corner weld.

Link welding

Solder joints are understood to be welds, heat-affected regions and base metals. Welding bond types: Angle welds, weld joints, and solder joints.